US2072417A - Method of irradiating substances with active rays - Google Patents

Description

March 2; 1937.

E. c. BERNDT El AL 1 METHOD OF IRRADIATINQ SUBSTANCES WITH ACTIVE RAYS Original Filed Jan. 19, 1934 a Shgets-Sheet 1 INVENTORS EDWARD c. BERNDT HARRY M. CREIGHTON 250mm, am

ATTORNEYS March 2, 1937. IE. c. BERNDT ET AL METHOD OF-IRRADIATING SUBSTANCES WITH ACTIVE RAYS Original Fild Jan. 19, 1934 8 Sheets-Sheet 2 MIHHHIH 'INVENTORb EDWARD BERNDT BY CREIGH TON ATTORNEYS 4 HARRY March 2, 1937., 2,072,417

METHOD OF IRRADIATING SUBSTANCES WITH ACTIVE imYs E. c. BEIRNDT ET AL a Sheets-Sheet 3 Original Filed Jan. 19, 1934 INVENTORS EDWARD c. BERNDT M- CREIGHTON BY M'LW ATTORNEYS HARRY E. C. BERNDT ET AL March 2, 193 7.

METHOD OF IRRADIATING SUBSTANCES WITH ACTIVE RAYS Original Filed Jan. 19, 1934 a Sheets-Sheet 4 1 I I I I I I I I I I a a n 1 ATTORNEY S March 2, 1937. E. c. BER NDT ET AL 2,072,417

METHOD OF IRRADIATING SUBSTANCES WITH ACTIVE RAYS Original Filed Jan. 19,' 1934 8 Sheets-Sheet 5 K40 l l INVENTORS E EDWARD c. BERNDT q; 14 EYARRY M. CREIGHTON :3 E I I Mun-W S 162 ATTORNEYS .Q. m a

March 2, 1937. E. c. BERNDT ET AL 2,072,417

METHOD OF IRRADIATING SUBSTANCES WITH ACTIVE RAYS Original Fi1ed Jan. 19, 1934 a Sheets- Sheet e INVENTORS EDWARD C- BERNDT HARRY M. CREIGHTON ATTORNEYS March 2, .1937. 1:, 3, ND AL 2,072,417

METHOD OF .IRRAD IAT ING SUBSTANCES WITH ACTIVE RAYS Original Filed Jan 19, 1934 8- Sheets-Sheet 7 INVENTORS EDWARD c. BERNDT HARRY M. CREIGHTON MAW ATTORNEYS March 2, 1937- E. c. BERNDT El AL 2,072,417

METHOD OF IRRADIATING SUBSTANCES WITH ACTIVE RAYS I I Original Filed Jan. 19, 193: 8 Sheets-Sheet s INVENTORS EDWARD C. BERNDT HARRY M. CREIGHTON ATTORNEYS Patented Mer, 2, 1931' UNITED STAT lllllTHOD I I aoian'zor IRRADIATING suns'mncas "P TENT 'OEFIc-Ei WITH ACTIVE RAYS Edward C. Berndt Norwalk, and Harry Greigh- I ton, East Norwaik,

Conm, assignors to The R.U,..V. Engineering Corporation, South Nor-- walk,. Conn., a-corporati'on of Delaware Application.

" 29 cieime.

This invention rela'tes to the method andlappar ratus of treatingo-r irradiating substances with active rays such as ultraviolet rays to impart improvements: in both the method and apparatus m for the irradiationof substances particularly described'and/or claimed in our copendi'ng appii cation entitled Active ray treating devices, filed January 2,11-930 and-serially numbered 418,027;

- I and our application entitled Method of irradiating 1 substances with active rays, filed January l6, 1933 and serially numbered 652,020.

Itls'well known that active rays, such as ultra= violet rays, have various effects on different sub-.

stances. For example; these rays, will kill bac 20 t'eria, and ,also impart to certain substances a property which isnow called vitamin D. Active rays wilzlalso stimulate bacteria rather. than' kill them if the'treatment is mild enough. Moreover,

it has been founddesjirable to use these rays for the sterilization 'and/or'activation ofmilk, fruit juices, malt products, wines, spiritous liquors, beer and many other partially opaque substances. It.

' istobe particularly noted that with this method milk can be sterilizedzwith'ultraviolet rays and 9 at the same time the vitamin D- efiect produced.

therein. There are also cases where it is desirable to inactivate enzymes in substancespand in'such cases the method to be hereinafter'described is also applicable. There are also other reasons for 35 the treatment of substances with active rays such as to produce beneficial chemicalreactions or to irradiate oils-and petroleum"products to impart to them healing effects or other properties However, the use of active rays may result in 'pro-,

ducing both detrimental and beneficial" effects,

andwe have found it is highly important for the irradiation of a substance to be accurately controlled to produce the r'esultdesired.

An exampleof the importance of (e irradiation ofimilk. We know that the germs which iniect and propagate in milk can be de- .-stroyed .with ultraviolet rays. We further know these rays will activate or produce vitamin D in 4 milk when it is irradiated. W alsoknow that i. this control may best be illustrated in the consideration of the January 19, 1934, Serial No. aortas? Renewed,Mav26,-19 36 ""Hence, in the irradiation 0t. milk: it; is, highly lm-v portant to accurately control theactivation thereof'in imparting, thereto orinducing a vitatively opaque to ultraviolet rays. We have therefore developed'a method of irradiation and certain improvements in irradiating apparatus to advancewthe art of accurately controlled irradiation, for any purpose and particularly in the fields of sterilization and activation and make possible theuse of these active rays to better advantage than has been possible with known methods and apparatus.

-Accordingly, an important'object of our present invention is to describe'a method and produce 4 certain fundamental types of apparatus, for treating 'substances-in whichthe amount of; ray energy employed in the treatment is accurately controlled andwherein application of such treat-, ment is eflectedunder such operating conditions that one is able to forecast the results to be obtained by such treatment when the effect and correlation of the variables attending the treatment of the substances. are understood and employed.

Our method relates to the irradiation of substances capable of having beneficial 'or detrimen tal effects imparted'theretoand comprises treating such a substance witha number of relatively short intermittent exposures to radiant energy emanating from one or more sources or stages of active rays,- no one of said .exposuresbeing sufficient to give the whole body of the substance the amount of treatment necessary to produce the ultimate desired beneficial results or effects, and mixing the substance between exposures such that said mixing takes place away from the action of the rays to permit oneto control the disber of treatments to be given depends, among other things, upon the layer thickness used, the time limits of exposure and the amount of desirable or beneficial effects desired and the amount of undesirable effects that may be tolerated.

To practice our method it is necessary to understand two important principles thereof, namely, first, the minimum total time of exposure or the minimum amount of treatment required to impart beneficial properties or elfects to a substance, and, second, the maximum total time of exposure or the maximum amount of treatment to which said substance may be sub jected before undesirable, detrimental effects are produced therein. With this understanding, our

invention, in one of its broad aspects, comprises exposing a substance to the influence of activerays of sufficient effectiveness and for such duration as to give the same a fractional treatment and to impart beneficial effects thereto, but for a duration insufficient to impart undesirable effects thereto, mixing said substance after such fractional treatment, and than alternately repeating this cycle until the desired beneficial effects throughout the substance have been at tained, these repetitions being less than that required to impart detrimental effects thereto. The layer thickness used for the {treatment will depend, among other things, upon the character of thesubstance itself. A clear knowledge of this method, as hereinafter set forth, will indicate what layer thickness should or can be used in each individual irradiating case.

We have found that it is very important to so irradiate a substance thatthe amount of irradiation or treatment received by diiferent portions of the substance may be carefully and accurately controlled between certain fixed limits above described. For example, in the treatment of milk, if the treatment is not accurately controlled one may impart to the whole body of milk only a small percentage of the potential vitamin D effect, which is beneficial, and at the same time '.may destroy vitamins naturally present in the milk, which may be just as important or even more important than vitamin D. Also, one may injure the taste or odor of the milk to such an extent that the milk cannot be used for human consumption, or it is said one may destroy a large portion of the vitamin D effect previously produced, all of which are detrimental effects caused by the treatment.

We have also found that it takes a lesser amount of treatment to produce vitamin D in milk than it does to produce changes in the taste or odor of the milk. Indeed, we have found,

'as will be hereinafter exp1ained,'thatthe time of exposure necessary to produce the vitamin D effect is muchshorter than the times mentioned by other workers in the literature on the sub ject. Some workers report times of exposure varying from eight seconds up to several minutes and evenhours. We have in our experiments produced the vitamin D effect in milk with an exposure which was about one twentieth (1/20th) of a second, and in some cases we have produced the effect with even a shorter time of exposure. We have also found that some types of bacteria are killed with an exposure'of about one two-hundredth (1/200th)' of a second or even 3 less, while working at a distance of one and one quarter inches from a my source. Wehave also found that the amount of irradiation required to kill harmful germs in milk is less than the amount of irradiation necessary to cause a change in taste and odor. Our experiments show that there is a considerable difference between the amount of active ray energy required to produce vitamin D and the amount required to destroy it, if it can be destroyed by the same type of energy that produced it. Our method therefore contemplates accurately controlling the irradiation of a body of milk or other substances, to produce, to a high degree, if desired, beneficial properties therein with a minimum amount of harmful effects,'if any.

By extensive experimentation we have discovered certain general rules of treating which are readily adapted to commercial treatment of various substances capable of having beneficial or detrimental effects imparted thereto. For example, we have found it is well to irradiate milk by moving it through a field of ultraviolet rays having an intensity in proportion to the concentration of the element to be affected by the treatment,

while if a thin film is used a portion of the energy is dissipated outside the substance.

It will be noted also that in our method the substance is agitated or mixed when it is away from the action of the rays.

above referred to, is sufficiently effective to accomplish satisfactory commercial results with many substances. It will be understood, for example, that when, in our method, we refer to the step of mixing, this mixing may be accomplished in any one of a number of ways and to any desired degree depending upon the problem at hand and the results to be desired.

In using our process it is desirable to take into consideration the intensity and the wave lengths of active ray energy at all points in the field of action. Considering, for instance, the surface .of the substance being exposed, if we find the intensity at one point of this surface to be lower than the intensity at another point, or if the.

wave lengths are different at different points, it is evident that the rate of flow should be faster where the high intensity or more effective wave treatment of.the surface during each exposure.

. Therefore, a simple method to control one elethe same distance from the source will then be about the same for each exposure and once the characteristics of the substance to be treated are understood, the amount-pf treatment received isa function of the time of exposure. The time of exposure for any part of a. substance cannot be computed without a. consideration of the partic The mixing or agitating may be performed. in any one of a number of lengths exist than where the low intensity or'. weaker wave lengths exist, to effect a uniform- However, it will be hereinafter seen that good f ular wave lengths available, asflwell as the. intensity of said rays at the point of utilization.

results may be obtained with our methodeven it the above directions are notfiprecisely .followed; In a general way it can be said that inst'ead of trying to irradiate the complete layer of a substance in one exposure, as is done by. those using a thin film or thin stream or by those who agitate while under the action of the rays, we only try to beneficiallyirradiate a relatively small portion, or, you might say, the skin orsurface of the layer or film and thenanix the substance while it is away from the action of the rays and 15.

thereafter return it again for treatment, repeating the cycle for as many treatments as are necessary to give the results desired.

We have discovered that this cyclic methodof giving a substance fractional or several properly timedshort intermittent periods of exposure in place of a single period of one continuous exposure, for a given number of times and mixing between exposures, gave us unexpectedly excellent results. Wehave'io'und that with a given amount of active-ray energy to be applied to a substance, the amount of beneficial effect imparted to a substance varies. with'the number of exposures and mixings given. We have also found that as a rule,-the numbermf treatments.

to which a substance may be safely subjected. depends upon/the relation be'tweenthe amount of treatment required to deleteriously afiect the substance and the minimum amount of treat ment necessary to produce a' beneficial effect in said substance. If the-time of each exposure l is too long, or the amount of treatment given is 1 too great, thenone is obliged to reduce the num-1 3 and more of them were used.

her of exposures in order to avoid detrimental effects, and consequently the amount of beneficial effects will be less than if shorter-exposures.

According"to the teachings herein, thetime of eachexposure, or the amountof treatment given during each exposure, may-be readily de-' termined by actually treating and testing-samples ofthe particular substance to be. treated. liikewise, the-most favorable time intervals between exposures maybe readily determined.

- will not be fully utilized in the completed treat- 4 We have found-as already stated, that also vary the'results. Thorough mixing between This is particularly important in sterilizing, because if the time intervals are not correct -the elfects from any preceding exposure or exposures ment. the layer thickness used when the substance is presented for irradiation has a bearing on the number of exposures to'be given andthe time lot each exposure. We have also ioundthat the degree of mixing given between exposures will exposures gives .the most accurate control of.

the amount of treatment and therefore the best results. However, this de ree of mixing may I not be necessary in man cases where the char stance may be properly controlled, one must, for

acter of the substance does'not require it, or because themaximu'm results are not desired.

"For an understanding of the properconstruction and operation of apparatus .to be used in practicing our method of irradiation, whereby the amount of. irradiation imparted toa' subthe reasons indicated above, appreciate the importance and take into consideration vth'eiolloW- ing ifactors incident to such treatment; i

(1) The intensity and wave lengths of the active rays at the 'point or zone at which they are applied to the substance being treated.-

(2) The time required to produce beneficial effects in the substance. I (3) The time required to produce intolerable detrimental effects in the substance.

(4) The depthmf layer or volume of the substance at the time it is presented to the rays for treatment, V

(5) The rate of agitation of the substance at the time of'treatment;

-(6) The degree of beneficial efiect' which it is desired to produce in the substance.

(7) The degree of detrimental effect which may arise from said treatment and the degree of said efiects which can be tolerated in the substance after the irradiation thereof has-been completed. 7 a

; (8) .The .timeof each exposure of the suhstance being treated.

ing between exposures.

(10) The amount of mixing that can be tolerated during exposure. r

Other objects of our invention will become apparent to those skilled in the art from the detailed description taken in connection with the more or less diagrammatic drawings forming a part hereof, and in which Figure 1 shows a; sectional elevational view oi an apparatus in which a body of the substance to be irradiated is simultaneously agitated and 9) The time of agitation or amount of mixpumped or otherwise forced upwardly through a treating chamber past a source of ultraviolet rays, controlled by any suitable means for in termittently cutting off the actionof said-rays means of a timing switch for turning on and off the current; supplied thereto to periodically produce ultraviolet rays'of such intensity and for such duration to beneficially treat the substance upon the substance, such for example as by and discontinue said treatment by extinguishing. said rays for predetermined time intervals during which the previously treated substance is thoroughly mixed with the untreated substa in saidchamber; v

Figure v1a, illustrates a shutter mechanism 'which may be used in combination with the ma-' chine of Figure 1- and a continuously burninglamp to producethe efiect of a; flashing ray source.

Figure 2 is a sectional .plan view taken on line 2-2 of Figure 1 and looking in thedirction of the arrows.,

Figure 3 shows an. apparatus comprising a spherical container for irradiating a substance as it flows in the form of a comparatively thin film downthe'inside' surface thereof; past a source of ultraviolet rays intermittently turned on and off for predetermined time intervals. Figure 4 shows an apparatus comprising a revolving-cone for irradiating a substance by causing the sameto fiow through a field of active rays, controlled by anysuitable on and oii timing switch or shutter mechanism. I Figure 5 shows an apparatus in which a substance to be irradiated flows from a trough down the sides of a vessel past a source of ultraviolet light controlled by any suitable on and off timin switch or shutter mechanism.

Figure 6"showsfan apparatus similar to that shown in Figure 5 in whichthe substance flows down the inside 'wall of a vessel past a source of ultraviolet rays and intermittently out of the region of said rays by passing successively behind emanating from the source.

Figure 7 shows an apparatus comprising a cylindrical cooler coil over which a substance to be irradiated is adapted to flow, from a trough, over the inside surfaces of the pipes of said coil and drop from one pipe to another behind a shield opaque to ultraviolet rays.

Figure 7a is a view taken on line '|a|a of Figure 7 and looking in the direction of the arrows.

Figure 8 is an enlarged cross-sectional view of two of the coils shown in Figure 7 and illustrates the path traversed by the substance in dropping from one coil to another behind the shield.

Figure 9 shows 'an apparatus in which a substance is adapted to flow from troughs disposed on the top of conventional washboard type cooler coils past a source of ultraviolet rays and be periodically removed from the influence of such rays by passing successively behind a plurality of spaced shields.

Figure 10 is a view taken on line |fl|0"of Figure 9 and looking in the direction of the arrows. V

Figure 11 shows an apparatus in which a substance is adapted to be treated by flowing under the influence of ultraviolet rays successively down the inside surface of a plurality of conical planesand after passing over each plane to be conductedto a point removed from the action of the rays where the substance is mixed by agitators and'thence conducted to another plane to receive a subsequent treatment.

Figure 12 is a View taken on line |2|2 of Figure 11 and looking in the direction of the arrows.

I Figure 13 illustrates an apparatus for irradiating a substance as the same passes a source of ultraviolet rays in an open free falling stream and means'for periodically interrupting the fall of the substance to cause the same to flow away from the influence of the light to become mixed and thereafter returned to the light for another treatment during a similar subsequent period of a l. Figure 14 is a, sectional view taken on line |4-|4 of Figure 13, looking in the direction of the arrows. 1

Figure 15 illustrates a device for irradiating a granular or powdered substance by conveying the same past a source of ultraviolet light in combination withmeans for agitating the substance between exposures to said light and while the same is removed from the influence thereof. Figures 16 and 16a illustrate modifications of the device shown in Figure 15 in that after each period of irradiation the substance is adapted to be mixed by either falling successively over inclined planes before being subjected to a sub-- sequent treatment (Figure 16), or by beingdelivered by one conveyor to another conveyor moving in an opposite direction.

Figure 17 illustrates a device whereby a substance may be irradiated by being conducteddown an inclined plane past a plurality of spaced sources of ultraviolet light, ,the plane being smooth in the region immediately under said lights where the substance is treated, and corrugated in the region between the lights to mix the substance between treatments.

Figures 18' and 19 are plangand elevational views, respectively, of a device for irradiating a substance disposed in a plurality of vessels successively presented to a source of ultraviolet rays for treatment and wherein means is provided for mixing the substance for a predetermined period of time after said treatment, and thereafter permitting the substance to quiet down in the vessel before being presented for a subsequent treatment.

Figure 20 shows an irradiating apparatus in combination with a perforated belt for periodi- [cally interrupting the passage of ultraviolet rays to a substance for predetermined periods during which the substance is mixed and permitted to come to rest before a subsequent treatment.

Figure 21 is a modification of the device shown in Figure 20 wherein a rotating perforated disc is employed to intermittently interrupt the passage of the treating rays.

The apparatus shown in Figures 1 and 2 comprises an open cylindrical casing 25 having a bottom 26 supported in any suitable way such as indicated at 21. A socket 28 is formed in the bottom 26 to receive the lower end of a quartz mercury vapor lamp 29. A cylindrical groove 30 is formed in the bottom of the casing to receive a quartz tube 3| disposed about the lamp 29. A revolubly mounted cylindrical shell 32 having a flange 33, supported on bearings 34 is disposed in the casing 25. A clearance space 35 is constructed between the shell 32 and the casing. A bearing surface 36 is formed at the bottom of the shell to contact with the inside of the casing so that when the shell is rotated it is supported on the bearings 34 and bearing surface 36.

A shaft 3! adapted to be rotated by any suitable means (not shown), is mounted on the out-.

side of the casing in bearings 38 and 39. A pinion 40, meshing with teeth 4| formed on the periphery of the flange 33, is mounted on one end of the shaft 31 so that when the shaft is rotated the pinion will rotate the shell 32. A plurality' of spaced agitators 42' are secured to the inside of the shell 32 and disposed from top to bottom thereof so as to define a broken helical vane in the space between the tube 3| and shell 32. The agitators 42 are of such width that the inner edges thereof terminate 'at a point proximate the quartz tube 3| without actually touching the same. Tube wipers 43 carryingany suitable wiping material 44, for wiping the outside surface of the tube 3| when moved with respect thereto, are disposed in staggered relation between the agitators 42. A cover 45, having flanges 48 and 41 adapted to support the upper ends of the lamp 29 and the tube 3 respectively, is provided for closing the opening at the top of the casing 25 and to serve as a retainer for the shell 32.

A pipe 48 having a plurality of inlet connections 49 opening into the annular space between the tube 3| and shell 32 serves as a means for introducing substance to be treated into the machines. A similar pipe 50 having connections 5| serves as a means to conduct the substance out of the machine. Current from any suitable source of supply is conducted to the lamp 29 through a time switch 52, resistance 53 and conductors 54. The switch 52 is constructeddn any suitable way whereby it is adapted to either'manually or automatically turn the current supplied to the lamp on and ofl, so that the lamp is intermittently energized for predetermined exposure periods and the rays of ultraviolet light from the lamp are available for the treatment of a tently shielding'or cutting off the action. of the rays may be used. Such a device diagram-' 5 matically illustrated in Figure 1a wherein the substance during that timegin order to treat and thereafter permit the substance to be mixed in themanner above described and to be herein-' after more particularly-described. Inasmuch as the switch mechanism per se, necessary to ac-'-- complish the described operation forms no part -of our: present invention, it is "deemed unnecessary to describe the same further than to merely state its'functional characteristics.

In cases where an on and off time switch mech anism presents practical difiiculties, a continuous light in combination with means for intermit slight obstruction to the rays emanating therefrom.

We will now describe'the manner in whichythe machine illustrated in Figures 1, la'and 2 may be operated. to practice our method of irradiation -D effect thereto.

in the treatment of milk to impart the vitamin In this explanation, milk has been selected as the substance to be irradiated merely by way of example, and'because the b'eneficlal and detrimentaleffects of such treatment are so pronounced. -Milk to be irradiated in this machineis forced or otherwise permitted to flow through the pipes 48-49 at a predetermined speed into the space or treating chamber 55 between the tube-'3 l -and shell 32 while'the shell,

agitators,-and ,wiprs, by means of the shaft and pinion 3l'4ll, are rotated as a unit in a counterclockwise direction (as seen in Figure 2) around the stationary quartz tube 3!. It will be noted that the helically disposed agitators 42 are rotated in a direction tending'to. move. the,sub-- stance in the treating-chamber in adirection opposite to that in which it isforced or per- ,mitted to flow therethrough, to inducea continuous and effective state of agitation in the substance as it passes up through ther'nachine and until it reaches the outlet pipes Ell- 5i.

Generally speaking if the distance between the lamp 29 and the tube 3|; the thickness of the layer of the milk inthe treating chamber, and the intensity and wave lengths of the ultraviolet rays emanating from a'the'lamp have all been selected or constructed to suit the result to be obtained, the milk will be. properly irradiated with a single passage through the machine when the on-and-off time intervals during which the actionof the rays are available for treatment and the rays therefrom cut off, so to speak, by either being extinguished or shielded, and the treatment arrested, is properly controlled by "either the time switch 52 or shutter 56 and properly correlated with-the rate of flow and rate of agitation of the milk. To accomplish this result the switch or shutter and'iamp must be fif'nstructedso that ultraviolet rays of suflicient ffeetivenessand for such duration are made available to. produe a beneficial efiect in that portion of the milk disposed in the treating chamber"proximate the quartz tube 3L To approach the best control of the amount of treatment tof'which the various portions of the substance are subjected, the (in-- ration of each exposure must be so timed and 75' correlated with other factors that the milk in the treating chamber, notwithstanding it is continuously agitated, will, in'effect, be substantially at rest during the exposure and the particles proximate the source will receive the beneficial effect of the exposure. At times, for instance,

'whenthe rate of agitation is high, it may be important in being able toeifect a beneficial treatment inthe' proper time to employ only a' very short exposureto rays of short wave lengths and of high intensity however other types of rays may be employed when the correlated conditions otherwise permit of their use.

After this initial treatment above described, the

switch is turned off or the shutter closed; in other words, the action of rays upon the substance is out off-- for such duration. that the ,milk in the treating chamber is mixed to a proper degree during that time. At the, expiration of the n1ix-. ing period the switch is turned on, or the shutter opened, so that substance is again subjected to the action of ultraviolet rays of suflicient eifec tiveness-and for such duration as .to produce a beneficial'effectin ..another portion of the Thereafter the'sesteps are repeated until the'de-.

sired result is attained.

Let us assume that the rate of flow through the machine 'is such that the milk flows upwardly through thetreatingchamber at the rate of one inch per second; that the-rate. of agitation is such that one second is required for a thorough and complete mixing; that the length of the treating chamber is twenty inches; that the depth of the layer of the milk in the treating chamber is ten times that through. which the rays will effectively penetrate during that period of exposure which produces a beneficial effect on the portion of the substance proximate the source, namely the skin or surface lying against the quartz tube 3I;- and that the intensity of rays used is suchthat an exposure of 1/ 100th of a second will produce a beneficial eifect in that portion of the substance exposed.

From the above it will be seenthat the treating rays be made available for i/lOOthof a second to produce a beneficial effect on a portion of the substance in the treating chamber, and

cutoff. or arrested for one second to thoroughly and completely mix the treated portion with the remainderof the substance in the treating chamber. During the time of exposure only 1% of the milk can be mixed, since the time of exposure is -l/l00th of that required for complete mixing.

milk would be 100% or completely mixed. Since the chamber is twentyinches long, itwould take twenty seconds for milk to flow through the same,

During the time the rays are off, however, the

and during that time while the milk would receive nineteen treatmentsand mixings, the total time of exposure to the rays of any particle would be only 19/ 100th second; After one passage through the machine the -percentage of possible.

beneficial effect produced in' this apparatus can be determined by actual test or computed em- ,pirically. If it is found that one passage through this particular machine does not accomplish the result desired, the substance may be passed through the machine again, providedthat to do so would not cause an undesirable detrimental efiect by giving some of the particles of the substance an additional exposure of Iii/th of a second.

Suppose, however, after this first treatment milk would stand only an additional exposure of 2/100th second -and it is desired to improve the ultimatebeneficial eflfectby a treatment in this type of machine. We might then reduce the layer thickness. For example, a shell of smaller diameter equipped with suitable agitators may be substituted for the shell 32 above'described and the space between the present tube 3| and shell 32 reduced. Assuming this is practical from a commercial standpoint, the layer thickness may be made one-half of that shown ,in Figures 1 and 2. Now if the same volume of milk is passed through our modified machine it will travel upwardly through the treating chamber at the rate of two inches per second. If the rate of agitation is such as to cause one hundred per cent mixing in one-half the time'required before, or in other words, in one-half a second, then with an exposure of 1/ 100th second, you would have two per cent mixing during exposure' If this is satisfactory for the problem at hand, one could then expose for 1/100th second and shut off the rays for one-half second and thus get nineteen exposures in one passage, and other things being equal the beneficial result would be better than. in the first case because the treatment in effect is concentrated, on a smaller volume of the substance. In the case of our modified machine the result may be improved if necessary for the case at hand by using a difierent lamp, namely, one having ray characteristics or intensities such that l/200th second givesthe same result as the 1/100th second treatment did with the first lamp, and then only one per cent mixing would take place during each exposure.

From the above discussion it is seen that to properly control the irradiation one must at all times take into consideration the factors set forth above.

The best commercial results may be realized in producing a high vitamin content in flowing or agitated milk by using the thinnest layer which is practical and a source of rays of such intensity that only a very short exposure is necessary in order to be able to beneficially treat the milk while it is substantially at rest, and at the same time be able to thoroughly mix the milk between exposures. It may also be said that as the layer thickness is reduced a higher percentage of the total milk in the treating chamber is beneficially treated at each exposure and a lesser number of particles are treated uselessly by having received an unnecessarily long exposure or an insufiicient exposure. Carried to the extreme, and to entirely impracticable limits, this leads one-in effect to attempt to expose in a film so thin that only one layer of particles can arrange themselves in a film. Now if these particles are bacteria which are only visible under a powerful microscope then it is evident that the ideal thin film cannot be produced. Consequently, our step-by-step method of exposing, then mixing, for properly timed periods, is the only known commercial way of accurately controlling the irradiation of substances which would' be deleteriously'afiected by over-irradiation.

To mix the substance during the time of exposure or treatment causes the over-irradiation of more particles than are over-irradiated by our method, which'teaches, among other things, that the treatment of the substance should be effected without substantial mixing.

While we have described an on-and-off switch and shutter in connection with Figures 1 and 2 to enable the substance being treated to be mixed between treatments, it will be understood that this structure is merely illustrativeand that other forms of shutters or shields, some of which Will be hereinafter described, are adapted to periodically arrest or cut off the action of the light rays and prevent the treatment of any portion of the substance during the mixing period irrespective of whether or not the substance is flowing or is at rest.

Our present invention comprises generally the improvements in apparatus for treating various substances. However, the characteristics of substances and the results which may be obtained in the irradiation thereof vary so-widely that one cannot designate which form of apparatus is to be preferred, for the treatment of a particular substance unless the treating problem is considered in the light of the above description. From a purely theoretical consideration, if the rays employed in the treatment of a substance are produced by a point source, the treating chamber should be spherical in shape and the source of rays disposed at the center thereof. On the other hand, if an elongated ray source is employed the treating chamber should be cylindrical and the source disposed at the axis thereof. However, expediency may influence one skilled in the art to disregard merely theoretical considerations for reasons which will become apparent in connection with the description of the modifications to be hereinafter described.

Figure 3 represents an irradiating device comprising a spherical container 60 into which a substance to be irradiated is discharged from a plurality of holes 6| in a coil 62 mounted at the top of the container and connected to an inlet pipe 63. Substance emerging from the holes 6| is directed against the inside of the container near the top thereof and flows down the side, in a moving stream in which more or less mixing or agitation is constantly taking place, to an outlet 64 where it is collected in container'65. An ultraviolet ray lamp 66 controlled by an on and ofi switch 52, or suitable shutter is disposed at the center of the container. is closed by a cover 61 so that the treatment may be effected if it is required in a system from which air is excluded. A shield 68 is suitably mounted in the bottom of the container to prevent the treatment of substance after it has passed thereunder.

Figure 4 represents an irradiating device comprising a cone ll rotatably mounted in bearings 12. A substance to be irradiated is pumped or otherwise forced from any suitabl' reservolr 13 through an inlet pipe 14 and discharged into the bottom of the cone. The substance so introduced is centrifugally distributed over the inside surface of the cone -H and caused to flow upwardly therein and spill over the lip 15 formed on the upper edge thereof into a trough 16 when the cone is rotated by. means of a'motor 11, a pinion l8 and gear 19 secured to the cone H. An elongated ultraviolet ray lamp 80 disposed at the axis of the conefll, is connected to a current supply through an on and off switch 52, or shielded by a shutter mechanism like that described in Figure 1a. From the trough 16 the substance is conducted through a pipe 8| to a collecting container 82. This type of device is particularly .well adapted for certain purposes because the film thickness and its rate of flow up the cone surface may be easily varied by changing the rate at which the substance is introduced into the bottom of the cone, the slope of the cone, and the speed at which the cone is rotated.

Figure 5 illustrates an apparatus comprising The container a suitably supported vessel 85 having a trough 86 mounted on the upper edge thereof, into which a substance to be treated is discharged from-a pipe 81. Substance from the trough is adapted to pass through perforations 88 in the bottom thereof and-run down the inside surface of the vessel 85 past-a source of ultraviolet light,

' such for example as a carbon. arc lamp 89. Current may be supplied to the lamp 89 through an on and. off switch 52=or a shutter mechanism similar to that shown in Figure 1a may be used.

'passed thereunder on its way to an outlet 92 The lamp 89 maybe of the open flaming arc type or as here shown be provided with a 'suitable shield 90 transparent to ultraviolet rays.

A shield 9| opaque to ultraviolet rays is suitably mounted in the bottom of the vessel to prevent the treatment of substance after it has and a collecting container 93.

Figure 6 illustrates a device for practicing our method'comprising a source of ultraviolet rays 89 adapted to operate contin ous'ly without a 3 in Figure 5. In this form of device, with its con-- tinuously running lamp or lamps, a plurality of spaced opaque shields 96 are mounted in the vessel on supports 91 secured at the bottom to shield 9| and at the top to the lamp mounting 98 by means of a support 99: The top .is further supported by a web I00 connectedto the inside of the vessel 85. Having pointed out the reasons for the importance of irradiating a substance with a number ofprop'erly timed intermittent treatments and then cutting off the I action of the rays upon the substance to arrest the treatment thereof during the mixing period, it will be seen that the devicesshow-n'in Figures 3, 4, 5, and 6 are all adapted to operate in that mixing 'or agitation is constantly taking place in a moving stream. For instance, substance emerging from the trough 86 (Figure 6) will receive atreatment as it flows down that portion of the inside surface of the vessel 85 designated by the letter A. Thereafter the substanceflows behind the firstopaque shield 98 and out of the influence of the rays when;it is mixed. After passing from behind the shield the substance receives a subsequent treatment as it flows overthe area B between the first and second. shields 95. Similarly it will receive a third, fourth and fifth treatment as it flows 'over the areas C, D 1/ and E respectively, before being finally removed from the action of the rays by passing under the shield 9i and thence to the outlet 92. In'this' case the relation between the areas A, B, C, Dand E, and the areas of the shields may be determined empirically according to the substance being treated, the time required for each treatment, and the amount of mixing whibh-inherently' takes place in a flowing stream, so that the mixing is substantially negligible during the relatively short time required for the substance to flow over the treating areas and relatively substantial during the time required for the sub'-. stance topass behind the shields 96. Finally, a

source of active'rays must be employed of such .disposed one above theother.

shield 96 between the tiers.

as to impart a beneficial effect to effectiveness the substance in the time required for it to pass 1 over. the areas A, B, C, D and E.

Figures '7 and 7a illustrate an irradiating device comprising a cylindrlcally formed cooler coil I04 comprising a plurality of spaced semi-circular sections or-pipes I05 mounted in headers I 05 and A trough I01, mounted upon e coil I04, receives-substance to be treated from any suitable source-through pipe I08. Perforations I09 are formed in the hottom of the trough I01 through which the substance flows from the trough I01 and successively over the pipe sections I05 to a trough I I0 mounted on supports III located at the bottom of'the cooler c'oil. A discharge opening H2 is provided in the, trough H0 and adapted to conduct the substance into a. collecting container II3. An

to the trough IIO, A plurality of shields II5, opaque to the active rays, is disposed between the lamp \and the coils and adapted to shield the substance from the influence of the rays as it flows and falls behind the shields from one coil to an other. vA guard II6, to prevent the substance from flowing on the side of the pipes I05 remote from the light may be provided in cases where it is desired to irradiate a. higher percentage of the substance in a single passage through the device;

Figure 8 illustrates the relative position of two coils or pipes I05 with respect to the guard H5 and the shield H5, andemphasizes how a substance, for example, in flowing'frpm points F to G, is removed from the action of the light rays during that period of flow. -It willbe understood that the relationship betweenthe spaces between the shields and the width of the shields them-- selves must be correlated to permit a treatment ing and thatthe flow behind the shields is of ,sufllcient extent to permit the proper amount of 'mixing to take place preparatory for a subsequent manner because it is known that more or. less treatment.

Figures 9 and 10 show a device comprising 3 what may be described as conventional cooler stance may be periodically removedfrom the effect of the light rays by flowing behind the shields during its ;des'cent down the coils. The

middle tier of 'coils II9 illustrates the m'anner in which substance will fiow simultaneously over both sides of a coil when a guard like that illustrated and described in Figure 8 is not employed and this tier will handle more substance than the outside tiers. tween the coils in tiers H8 and I20 and will have the efiect of increasing 'the percentage of the substance treated similar to that of the guards H6 above described. It will be understood that while the shields in Figures Q, 7 and 9 are illustrafed as bei'ng'horizontally disposed at predeter mined intervals, the horizontal position of itself 75v is not essentially necessary." Suflice'it to say that Suitably proportioned spaced Guards I26 may be disposed be 'of cooler coils and the lamps I2I so that the sub-.

' I3I, I32, I33 and I34 over which a substance to be irradiated is adapted to flow through openings I35 in the bottom of a trough I36, successively past a source of ultraviolet rays I31. The length of each of these planes is such that the time required for thesubstance to flow from the upper edge thereof to the lower edge is sufllcient for the substance to receive a proper light treatment, while the distance itself is insufficient to substantially mix the particles of the substance during such treatment. A basin I38 formed behind a shield I39 is disposed at the bottom of the cone I30 and adapted to catch the substance after it has traversed the surface .thereof and received its first treatment. Any suitable mechanical agitator, I40, which in this case comprises a flexible cable I4I with paddles I42 thereon, rotated byany suitable means, not shown, is provided for agitating the substance that collects in the basin I38 and until it spills over the rearwall. I43 of the basin I38 to the plane I 3I where it is again presented for an active ray treatment under con-' ditions similar to that afforded by the plane I30. Substance from the plane I3I is collectedin a basin I42for a subsequent period of'agitation before descending the plane I32 for the next treatment; and so on. It will be understood that the shields I39 prevent the substance in the basin from being treated, and consequently the mixing which takes place therein is away from theinfluence of the light. below the plane I34 to catch thetreated sub stance and conduct-it to any suitable container.

Figures 13 and 14 illustrate a device for irradiating a substance descending in an open'fr'ee falling sheet or stream past ultraviolet ray lamps I50. This device preferably comprises a rectangular container having sides I5I, a bottom I52, formed with troughs I 53 extending lengthwise thereof between end pieces I54. The container is mounted upon any suitable-support I55. Substance to be treated is delivered through pipes I56, to troughs I51 formed in a cover I58. The troughs I51 are similar to the trough I53 in the bottom I52 and are disposed directly above the same so that if the mixing shelves or battles and I51, assists, by means of a series of angularly disposed stationary agitators I62 in supporting a baffle or catch basin I63 disposed under the opening I59. A shield I64 extending both above and below the surface of the baiiie; I63 is formed on the front edge thereof to prevent substance which collects in the basin from spilling out towards the lamps I50. A second series of angularly disposed stationary agitators I65 are mounted on the baflle I63. It will be seen, from Figure 14, that the agitators' I62 and I65 are oppositely disposed with respect to one another. The baflles I68 receive further support from the ends I54 and ribs I66 A trough I44 is provided I16 against the teeth of the ratchets I80.

which extend from top to bottom of the container at each side thereof. A tier of similar shelves, baffles, agitators and shields are disposed at each side of the lamps I50 and because of their similarity it is deemed unnecessary to describe the same with greater particularity. From the above agitators I62 but still behind the shield I64 until it reaches the edge of the shelf I6I where it drops again ina free falling sheet through a field of active raysemanating from the lamps I50 to receive another treatment. It will be understood that substance in falling successively over the --'shelves I6I receives a series of short periods of exposure without substantial mixing during each treatment and that between each treatment the substance is mixed in flowing past the stationary agitators before being presented to the rays for a subsequent treatment.

Figure 15 illustrates a device adapted to treat a powdered substance in accordance with the teachings of our method of irradiation. This device comprises a hopper.I10 from which substance flows to a conveyor belt "I and is conducted under a series of spaced ultraviolet ray lamps I12 and collected in a container I13. The lamps I12 are provided with reflectors- I14 adapted to concentrate the rays on a transverse area of the conveyor immediately under the light so that the substance in approaching and leaving lighted areas will not receive an appreciable treatment and thereby enable one to regulate the duration of .the treating period by controlling the speed of the conveyor. A guard I15 is disposed under the conveyor belt to position the belt with relation to the reflectors I14. Agitators I16, having knockers I11 extending through openings I18 in the guard I15 are mounted on pins I19. Ratchets I80, mounted on shafts I8I are driven by the conveyor mechanism, as shown. provided to urge the ends I83 of the agitators It will be readily understood that as the ratchets are rotated the agitators will jostle and mix the powder on the conveyor while the same is away from the action of the light rays.

Figure 16 shows'a modified form of device for irradiating powdered material comprising a hopper I85 from which'the material is successively Springs 182 are I conveyed on belts I86, I81, I88 past ultraviolet lamps I89, I90, I'9I, disposed proximate the surface ofsaid belts, respectively, and thereafter d6: posited in a container I92. Driving means I93 is provided for operating all of the conveyor belts at a predetermined speed so that the treatment received by the material in passing under the lamps, insofar as the conveyor speed is concerned, may be regulated and controlled. In this device substance from the belt I86 is dropped past a plurality of agitating deflectors I94, I95, I96, I91 from which it falls on to the conveyor I81. As occasion requiresthe deflectors I94--I91 may be hinged for example, at I98 and oscillated by any suitable means to further agitate the falling sub- 45 the pinion 2 l5 to make approximately a one-third revolution. i

the substance is mixed after having receivedan initial treatment and before receiving a subsequent treatment. In this case, like that shown in Figure 15, reflectors 200 are disposed about the lamps l89-|9l tolocalize the substance treat-j 'ing area and in that respect contribute to the control of the irradiation desired.

Figure 16a illustrates the manner in which a pluralityof conveyors 202, driven in opposite directions, are adapted to accomplish the necessary mixing between treatments. This form of device is adva'ntageou'swhen a substance may be proper- 1y mixed by merely turning it over after. each treatment. Such is the eiiecton a stream of'substance discharged from the end of one conveyor onto another. conveyor moved in an opposite direction; Lamps 203 are mounted proximate each stance is exposed to the rays. Corrugated sections H2 is at rest under the lamp M6, and the subm in the trough E04 are provided in this case to mix the substance, after each treatmentand before receiving a subsequent treatment.

Figures 18 and 19 illustrate themanner of irradiatinga substance at rest in avessel 2l2 mounted on a revolubly supported turntable 2l3. Gear teeth-2l4, formed in the periphery of mutilated pinion 2 l 5 serve as. means for rotating the table in the direction of the arrow when the pinion is rotated by any suitable means, not shown: This device is constructed so that the vemel 2l2 dwells under an ultraviolet lamp v 2H5 for approximately two-thirds of the time required ,for' the pinion 2 i5 to make one revolution and thereafter movefrom the position'shown to the next succeeding position during, the time required for In the devicehereshown, twelve vessels, simi lar to the vessel 2 i2, aremounted on the table 2L3 in position identified by the numerals I to",

both inclusive, so that each vessel in turn is presented to the ultraviolet rays for treatment for a predetermined time. Agitators 2l1, 2i8f2l9 and 220 are mounted in any suitable manner to beperiodically positioned and rotated respectively in any vessel occupying positions I to 4, both inclusive, during a portion of the time the table stance in the vessels is being treated. It will be understood that means, not shown, is provided to raise and lower the agitators in time to permit the pinion 2l5l'torotate the table, step-by-step,-

and move thevessel's from one position to another.

After the vessels have passed the first four, or

mixing positions, the substance is permitted to come to rest, in passing successively from'positions 5 to II, both inclusive, preparatory to receiving a subsequent treatment when it occupies position number l2. In some respects, this device may be said toqapproach an ideal way of treat-* ing a substance. The-operation of this device serves to emphasize applicants step-by-step sequence of treating steps wherein each'trea'tment is sumcient to activate only a portion of the sub-' stance in a given volume and thereafter thorough ly mixing the substance before it is subjected to a subsequent treatment... In this case the control of the treatment received by the substance is improved because when a'substance is quiet. dur

ing the time of each exposure all particles on the surface of the substance receive substantially the same amount of treatment.

" Fi ure 20 illustrates a device in An agitator 225 having paddles 228 is disposed in which afsuba stance to be irradiatedis placed in a rotatably mounted v'essel'223 under an ultraviolet lamp 22!.

the vessel and adapted to stir the substance when the vessel is rotated by means of a motor 221 through a belt 228 passing around apulley 229 sc .cured to the vessel in any suitable manner. Current issuppliedto the motor 221 through an automatic on and off controlling device 230 so that the-motor will run for a predetermined period and agitate the substance andthen stop for a prede-,

,termined periodtopermit the substance in the .vessel to beco'me quiet and thereafter receive a.

treatment from the lamp 224.-- Abelt 23l disposed between the lamp and vessel, and having a pin-- rality of perforations 232 is mounted on spools 222 driven intermittently. by any suitable means,

is at rest therein, it being understood that'duri'ng the period of agitation andth'e'period required to permit the' substance to. come to rest in the vessel the belt is moved to a position to shut off thedight from the substance, the table 2l3 and meshing with the teeth' of a I to that shown in Figure 20 except that a circular Figure 21 shows a device inall respects similar It is well known that ozone, nitrousoxide, air,

and similar factors may have. certain effects itwill be understood that our'process and appaeliminating either the undesirable effects, or the factors themselves, may be employed.

'onsome substances which are detrimental and ratus is such-that any well known means for Various modifications in the configuration;

composition and dispositionof the component elements which in combinationconstitute our apparatusimprovements, as well as in-the selective combination or application of the various steps in our improved process will occur to those skilled in the art, and no limitation is intended by. the

phraseology of the foregoing description or the exemplary illustrations set forth, or described in connection with the accompanying drawings. What is claimed is: I

'1. A method of irradiating a partially opaque:

substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of exposing the substance to the influence of ultraviolet rays, and While maintaining said substancefin the normally effective range of said rays intermittently cutting oif the action of said rays upon the substance, the duration of each exposure being sufliciently short and operating conditions such that no substantial mixing takes place during such exposures, and mixing the substance between exposures.

2. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance in a moving stream, in which more or less agitation or mixing is constantly taking place, past a source of ultraviolet rays, and while maintaining said moving stream in the normally effective range of said rays intermittently cutting off the action of such rays upon the moving stream, the duration of each exposure being sufiiciently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of the cutting off being suificiently long to enable substantial mixing of the substance between exposures 3. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance in a moving stream, in which more-or less agitationor mixing is constantly taking place, past a continuous source of ultraviolet rays, and shielding off from the effect of such rays and mixing successive portions of such moving stream, the duration of each exposure being sufiiciently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of shielding-off being sufiiciently long to enable substantial mixing of the substance between exposures.

4. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance in a moving stream or layer vertically downward by gravity over the interior surface of a hollow cylindrical member and parallel to the axis'of the latter, in which stream more or less agitation or mixing is constantly taking place, past one or more continuous sources of ultraviolet rays located substantially at the axis of said member,

and shielding off from exposure to such rays and mixing successive sections of said moving layer or stream, the duration of each exposure being sufliciently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of shielding off being sufiiciently long to enable substantial mixing of the substance between exposures.

5. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable efiect thereto, which comprises the steps of conveying the substance in a moving stream of greater thickness than that through which the rays will penetrate past a continuous source of ultraviolet rays,- and successively shielding off from the effects of such rays and mixing portions of such moving stream, the duration of each exposure of said substance to the ultraviolet rays being relatively short and operating conditions such that no substantial mixing takes place during such exposure and the mixing of the portions of said substance while shielded from-said rays being relatively substantial;

6. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without im-- parting an undesirable effect thereto, which com prises the steps of conveying the substance by gravity in a vertically and downwardly moving hollow cylindrical stream past a continuous source of ultraviolet rays located substantially at the axis of said moving cylindrical stream, and shielding ofr from exposure to such rays and mixing successive sections of such moving stream, the duration of each exposure to such rays being relatively short and operating conditions such that no substantial mixing takes place during such exposure and the mixing of the sections of said substance while shielded from said rays being relatively substantial.

7. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable eiTect thereto, which comprises the steps of conveying the substance in a moving stream of greater thickness than that through which the rays will penetrate, in which stream more or less agitation or mixing is constantly taking place, past a continuous source of ultraviolet rays, shielding off successive portions of such moving stream from the effects of such rays, the duration of each exposure being sufficientlyshort and operating conditions such that no substantial mixing takes place during such exposure, and accelerating such mixing of the substance as it is shielded off from such rays.

8. The method of irradiating a partially opaque substance, which comprises conveying the substance in a moving stream vertically downward by gravity over the interior surface of a hollow cylindrical member and parallel to the axis of the latter, intermittently exposing the surface of portions of the substance to a beneficially effective amount of ultraviolet ray energy located substantially at the axis of said member, the duration of each exposure being sufficiently short and operating conditions such that no substantial mixing takes place during such exposures, shielding off from exposure to such rays the remaining portions of said moving stream, and mixing said remaining portions as they are shielded off from such rays.

9. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial eiTect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance in a moving stream, in which more or less agitation or mixing is constantly taking place, past a source of ultraviolet rays intermittently energized for predetermined exposure periods, the duration of each exposure period being sufficiently short and operating conditions such that no substantial mixing takes place during such exposure periods and the duration of the periods between exposures being sufliciently long to efl'ect substantial mixing of the substance.

10. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance in a moving hollow stream, in which more or less agitation or mixing is constantly taking place, past a source of ultraviolet rays located substantially at the center of said moving stream and intermittently energized for predetermined exposure periods, the duration of each exposure period being sufficiently short and operating conditions such that no substantial mixing takes place during such exposure period and the dura:

11. 'rue sh .011 irradiating a aruauy op que subst ce by-exposures to ultraviolet rays to produce a beneficial eiiect therein and without imparting an undesirable eflect thereto,which substance. i

. that through which the rays will penetrate past ccmprisesthe steps ot'conveylng the substance in a moving streamer Player vertically downward by gravity over the interi'or surface of a hollow cylindrical member and parallel to the axis of the latterin which stream more or less agitation .10 or mixing is constantly taking place, past one or a more sources of ultraviolet rays located substan- 12. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect thlrein and without imparting an undesirable effect thereto, which comprises the stepsof conveying the, substance in .a moving stream of greater thickness than a source of ultraviolet rays intermittently energized for predetermined exposure periods, and mixing the substance between exposures, the

duration of- 'each exposure period being relatively short and operating conditions such that no substantial mixing takesplace ,during such period and the mixing of the substance between exposure periods being-relatively substantial. 1 7

r3. The method. I or irradiating a I partially v opaque substance by exposures toultrdyiolet rays 'toproduce a beneficial eilect therein and with- 1 out imparting an undesirable efiect theretm which comprises the steps of conveyingthe substance by gravity in a vertically and downwardly moving hollow" cylindrical stream past' a; source of ultraviolet rays located substantially at the axis of said moving cylindrical stream and inter'rnittentlyenergized .-1or predetermined. exposure periods, mixing said substance between exposures/ the duration of each exposure period being relatively short and operating conditions such that no substantial mixing takes place during such a period and the mixing of said substance being relatively substantial. i

14. The method of irradiating a partially opaque substanceby exposureto ultraviolet rays to produce a beneficial efiect therein and with-- out'imparting an undesirableefiect thereto,,which comprises the steps ofconveying the substance in a moving hollow cylindrical stream, in which more or less agitation or mixing is constantly taking place, past a continuous source of ultraviolet rays located substantially at the axis of said moving cylindrical stream, and shielding off from exposure to such rays and mixing successive sections of suchl-moving stream, the duration of each exposure being sumciently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of shielding-offbeing, sufliciently long to enable substantial mixing ofthe sub stance between exposures.

' 15. The method of irradiating apartially opaque substance by exposures to 'ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable efiect thereto, whichcomprises the steps of conveying the substance by gravity in a vertically anddownwardly mov--v i I (I 1 1 'ing hollow cylindrical stream, in which more or less agitation or mixing is constantly taking place,

' past a continuous source of ultraviolet rays locat--- ed, substantially at the axis of said moving cylindrical stream, and shielding off from exposure to such rays and mixing sections of such moving stream, the duration of each exposure being sufflciently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of: shielding-off being sufliciently long to enable substantial mixing of the substancebetweenexposures.

16, The method off irradiating a partially opaque substance by exposure to ultraviolet rays to produce a beneficial effect therein and without imparting an'undesirableefiect thereto, which comprises the steps of. conveying theisubstance in a nioving hollow cylindrical stream of greater thickness than that through which therays'will penetrate past a continuous source oi ultravioletrayslocated substantially at the axis of said moving cylindrical stream, and shielding off from exposure to such rays and mixing successive sections of such moving stream, the duration of each exposure of said substance to the rays being relatively short and operating conditions such that no substantial mixing takes place during such exposure and the mixing of the sections of said substancewhile shielded from said rays being relatively substantial 1'1 The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial efiect therein and without imparting an undesirable efiect thereto, which comprises the'steps of conveying the substance tinuous source of ultraviolet rays located substantially at the axisof said moving cylindrical stream, shieldlngoff successive sections; of such moving stream from exposure to such rays, the

in a moving hollow cylindrical stream of greater" duration of each exposure being sufliciently short and operating conditions such that no substantial.

mixing takes place during such exposure and accelerating the mixing oi the'substance as it is shielded off from such rays.

18. The method" of irradiating --apartially opaque substance by exposures to ultraviolet rays to produce a beneficial efiect therein and without imparting an undesirable effect thereto, which cylindrical member and parallel to the'axis of the latter in which stream more or less agitation or mixing is constantly taking place, past one or" more continuous sources of ultraviolet rays located' substantially at the axis of said member,- shielding off successive sections of said moving duration of each-exposure being sufllciently short a and operating conditions such that no substantial mixing takes place during such exposure, and accelerating the mixing of the substance asit is shielded off from such rays.

19. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce'al beneficial effect therein andwithout imparting an undesirable effect thereto, which comprises the steps-of conveying the substance stream or layer from exposure to such rays, the

in a moving hollowcylindrical stream, in which i more or less agitation or-mixing ,is constantly taking place, pasta sourceof ultraviolet rays located substantially at the axis of said moving cylindrical stream and intermittently energized for predetermined exposure periods, the duration of each exposure period being sufficiently short and operating conditions such that no substantial mixing takes place during such exposure period and the duration of the periods between exposure being sufficiently long to effect substantial mixing of the substance.

20. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance by gravity in a vertically and downwardly moving hollow cylindrical stream, in which more or less agitation or mixing is constantly taking place, past a source of ultraviolet rays located substantially at the axis of said moving cylindrical stream and intermittently energized for predetermined exposure periods, the duration of each exposure period being sufficiently short and operating conditions such that no substantial mixing takes place during such exposure period and the duration of the periods between exposures being sufficiently long to effect substantial mixing of the substance.

21. The method of irradiating a partially opaque substance by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprisesthe steps of conveying the substance in amoving hollow cylindrical stream of greater thickness than that through which the rays will penetrate past a source of ultraviolet rays located substantially at the axis of said moving cylindrical stream and intermittently energized for predetermined exposure periods, mixing the substance between exposures, the duration of each exposure period being relatively short and operating con ditions such that no substantial mixing takes place during such exposure period and the mixing of the substance between exposure periods being relatively substantial.

. 22. The method of irradiating a partially opaque substance by exposure to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the substance in a moving hollow stream of greater thickness than that through which the rays will penetrate past a source of ultraviolet rays located substantially at the center of said moving stream and intermitthrough which the rays will penetrate and in which more or less mixing is constantly taking place, successively exposing the substance to ultraviolet rays after interruptions of predetermined duration to the passage of said rays to the substance from a source from which said rays emanate, the duration ofv each exposure being sufficiently short and operating conditions such that no substantial'mixing takes pl'aceduring such exposure and the duration 01' said interruptions being sufliciently long to effect substantial mixing of the said substance between exposures.

24. A method of irradiating milk by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of exposing the milk to the influence of ultraviolet rays, and while maintaining said milk in the normally effective range of said rays intermittently cutting'off the action of said rays upon the milk, the duration of each exposure being sufficiently short and operating conditions such that no substantial mixing takes place during such exposures,

and mixing the milk between exposures.

rays, and while maintaining said moving stream in the normally effective range of said rays intermittently cutting off the action of such rays upon the moving stream, the duration of each exposure beingsufiiciently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of the cutting off being sufficiently long to enable substantial mixing of the milk between exposures.

26. The method of irradiating milk by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the milk in a moving stream, in which more or less agitation or mixing is constantly taking place, pasta continuous source of ultraviolet rays, and shielding off from the effect of such rays and mixing successive portions of such moving stream, the duration of each exposure being sufficiently short and operating conditions such that no substantial mixing takes place during such exposure and the duration of shielding-off being sufliciently long to enable substantial mixing of the milk between exposures.

27. The method of irradiating milk by exposures to ultraviolet rays to produce a beneficial effect therein and without imparting an undesirable effect thereto, which comprises the steps of conveying the milk in a moving stream of greater thickness than that through which the rays will penetrate past a continuous source of ultraviolet rays, and successively shielding off from the effects of such rays and mixing portions of such moving stream, the duration of each exposure of said milk to the ultraviolet rays being relatively short and operating conditions such that no substantial mixing takes place during such exposure, and the mixing of the portions of said milk while shielded from said rays being such moving stream, the duration of each exposure of said milk to the rays being relatively short and operating conditions such that no sub: stantial mixing takes place during such exposure and the mixing of the portions of said milk while

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