US2153105A - Device for laboratorical measuring of liquids - Google Patents

Description

April 4, 1939. 1. szf-zcsl. 2,153,105

DEVICE FOR LABORATORICAL MEASURING OF LIQUIDS Filed` Feb. 27, 1956 S26/c s z' Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE DEVICE FOR LABORATORICAL MEASURING F LIQUIDS Istvn Szcsi, Budapest, Hungary 8 Claims.

The invention relates to controlling devices, for use mainly in laboratories, for measuring or dispensing very small quantities of liquids with extreme accuracy.

One object of the invention is to ensure the possibility of easy handling of the controlling apparatus.

Another object of the invention is to render the controlling apparatus suitable for a plurality of measurements or dispensing operations dilering from each other for the simultaneous handling of a series of tubes for the distribution of liquids by aid of a controlling device.

The other details of the invention will appea in the course of the specication. f

The drawing diagrammatically illustrates several embodiments of the invention, shown by way of example for medical purposes.

Fig. 1 is a longitudinal section and partly in side elevation of apparatus for the transference and xing of levels of liquid.

Fig. 2 illustrates a similar apparatus together with a complete pipette. This apparatus is provided with two auxiliary junctions.

Fig. 3 is a section taken along line III--III of Fig. 2, showing the cross-section of an auxiliary junction of the threaded type.

Fig. 4' illustrates apparatus similar to that shown in Fig. l, but provided with an auxiliary membranepump and an abutment for the rubber ball.

Fig. 5 shows, partly in longitudinal section and partly in side elevation, apparatus of the type comprising two membrane pumps, the apparatus being tted with a pipette of the type usually employed for the counting of blood cells.

Fig. 6 is a front elevation drawn to a smaller scale than that of the other figures, of apparatus of the type comprising a series of pipettes and a stand.

Up to now, the liquid to be examined has been drawn up into the pipettes by mouth or by means of a rubber ball iitted directly on the pipettes. This method is detrimental to health, and is also unreliable, because it is impossible even for a person possessing a great deal of practice to regulate the level of the liquid in an accurate manner.

By means of the invention, these drawbacks are eliminated by employing measuring tubes having a self-sealing bottom in communication with a pump device ior displacing the liquid therein and having precision means for adjusting and precisely fixing the level of the liquid. The bottoms of the tubes are made self-sealing by providing an opening therein which is so narrow that when the upper opening of the tube is closed, it is impossible for the liquid contained in the tube to drip out merely by its own weight. Such apparatus is shown in Fig. l, where the-constituent parts of the apparatus are the casing I, a valve operated by means of a screw-thread, namely the needle-valve 2, the hand-wheel 3, the tube junction 4 and the junction 5 for the pump device comprising a rubber ball 6, by means of which it is possible to produce either pressure or suction. The pipette 'l is connected up to the tube junction 4 by means of a rubber sleeve 8.

If the ball 6 exerts a suction effect and the lower end of the pipette 'l reaches down into the liquid to be examined, all that is necessary in order that the liquid should rise to the desired graduation is to effect an opening or closing of the needle-valve 2 by turning the hand-wheel 3. When the liquid is sucked up by the mouth or by means of a ball fitted directly to the pipette, it is not possible to close the upper space of the pipette in an air-tight manner, without thereby altering the conditions of pressure ruling in the space above the indicating level. It is also necessary to supervise, simultaneously, the variations of the level and the variations of the pressure, and it is not possible with such an arrangement to discontinue the pressure immediately when the desired level is reached. The present invention enables the pressure to be varied and the level to be xed as far as possible independently. By means of the hand-ball or other pump devices it is easily possible'to produce a continuous suction since it is possible to close the valve by a reflex motion and rapidly. The attention oi the operator may be concentrated on observing the variation of the level alone, and accordingly it is possible to work with such a degree of accuracy that the level may be varied at will, from one graduation to another. When closing the valve the hand of the operator becomes released and the level remains unchanged, even if the lower end of the pipette is lifted out of the liquid to be examined. Thus, by the apparatus according to the invention, the level existing at any moment will not only be adjusted, but will also be fixed at the same time.

If on the other hand, a pressure higher than atmospheric is produced in the ball, it is necessary to proceed in the same way, in order to disfpense the desired quantity of liquid from the pipette in an accurate manner. For dispensing in this manner, it has been necessary, up to now, to employ tubes tted with a cock on their lower ends. Such cocks, which are usually of glass, in-

cating and render the dispensing operation tedious. All these drawbacks are eliminated by the invention, and, with an accurate adjustment of the valve, dispensing in any quantities desired, and even accurately measured uniform drops may be released from the pipette,

The tube junction 4 and the junction 5 for the pump device, between which two parts the valve 2 is inserted, are parallel, whereby handling is simplified. For the same purpose the hand-wheel 3 is arranged so as to be in easy reach of the hand gripping .the mechanism, and the hand-wheel is sufliciently large to act as a base for the entire apparatus whereby the apparatus may be placed on a table with the wheel downwards.

Figs. 2 and 4 illustrate apparatus which is substantially similar to the device shown in Fig. l. The differences are the following:

According to Fig. 2, a stufng box I0 `is provided on the casing I, above the tube junction 4. An opening 9 provides communication between the interior of the tube junction 4 and the exterion of the casing through the stuffing box. The stufling box is adapted to receive a pipe 3l shown in Fig. 6, hereinafter more particularly described. When a pipette is attached to the sleeve 8 so as to enable the apparatus to operate upwardly from below, it is necessary to close the opening 9 and for this purpose a rod II is inserted in the stufng box as shown in Fig. 2. On the other hand, when the apparatus is required to be employed in the manner shown in Fig. 6, the rod II is replaced by the pipe 3i and the tube junction 4 is closed.V By means of the construction shown in Fig. 2, it is possible to employ the same apparatus in the manner shown in Fig. 2 as well as in the manner shown in Fig. 6.

Above the valve 2, a screw-threaded nipple having an opening I2 is provided which serves for assisting the rubber ball B. The nipple is provided with an axially extending slot I3 having a depth equal to that of the screw threads. This slot I3 is also shown in Fig. 3. The opening I2 is closed by a screw-cap I4. As soon as the screwcap I4 is slightly opened, the space above the valve 2, together with the rubber ball 6, will immediately, through the slot I3, communicate with the atmosphere. The screw-cap I4 is opened when effecting the operation of liberating uid drop by drop or for instance when it is desired to effect repeated suction by means of the rubber ball 6 after its first inflation, with valve 2 in the closed position.

According to Fig. 4 the rubber ball 6 is iitted with an abutment shield i5 and it is against this shield that the ball is pressed in order to enable it to be completely evacuated easily. On the side of the casing I on which the tube junction 4 is situated, and above the valve 2, an additional pump I6 is provided, serving as an auxiliary source of pressure, its purpose being that in the closed condition of valve 2, it is still possible to control the liquid level with micrometric precision. The resilient membrane pump I6, forming the additional pump may be regulated by means of the screw I'I. By these means it is possible to compensate for variations of the liquid level resulting from changes of temperature taking place during operation.

According to Fig. 5 the means for varying the level of the liquid, and fixing it at the same time consists of two pumps of different size, each of which has its own separate suction-pressure member and each of which has its own separate crease the cost of the apparatus, require lubrimechanical regulator, the neness of the adjustment produced by the two regulators being different. Apparatus of such a type is usually employed for a pipette i8 of bottle-gourd form, in order to make it possible to conform even to the greatest differences of calibration occurring in immediate mutual succession. Thus for instance in the case of the pipette I8 for the examination of blood the thin blood-drawing tube provides a space the volume of which exceeds a hundred times the volume of the blood-drawing tube.

Two membrane pumps of different type are shown each of which has its own individual resilient membrane I9, 2li, and each of which has its own individual regulating screw 2I, 22, the said screws producing adjustment of different degree of neness. The smaller pump is employed for the contents of the narrow tube of the pipette I8, while the larger pump is employed for the contents of the wide head part of the pipette I8. Thus it becomes possible to work with the same rapidity and accuracy in both parts of the pipette.

The pumps are held together in a rigid manner by means of the frame 23, so that the adjustment of the levels of liquid will not vary even in case the apparatus is pressed by the operators hand.

The'regulator of the one pump is within easy reach of the hand which operates the other pump, so as to enable the apparatus to be held and at the same time be regulated by hand. For this purpose one pump is arranged so that its spindle is inclined relatively to that of the other pump.

According to Fig. 6, the device by which the level of the liquid is varied, consists of the collecting tube 24 which is of substantial construction to prevent any deformation at the pressures occurring during the operation of the device, and a series of tube junctions 25 branching out from the collecting tube. This device is based on the recognition of the fact that automatic pressure distribution is, between the limits coming under consideration, practically perfect. A device for varying the liquid level in this type of apparatus comprises a closing member and it is even possible to use an ordinary handball as a source of pressure for it. Inaccuracies of the ball, which would not be permissible in the case of individual tubes, will become of no eiect owing to the fact that their inaccuracy becomes distributed over ten tubes.

If the zero lines or the Calibrating base lines of the measuring or dispensing tubes connected to the common collecting tube are adjusted into a common horizontal level, the distribution of pressure will be accurate even in the case of tubes of different types. The accuracy which can be attained even permits of only one or a number of the control tubes being calibrated, while the others may remain uncalibrated. It is also sufcient if the adjustment of the levels is checked in one or two control tubes only. Thus measurements are rendered more rapid and the cost of the apparatus is substantially diminished.

Among the ten pipettes shown in the drawing which are connected to the tube junctions 25 there is only one calibrated pipette 'I, while the pipettes 25, 2l are uncalibrated. The diameter of the pipette 21 differs from that of the others, so that it is possible for a measured quantity different from the measured quantities of the other pipettes to be dispensed from the pipette 2l. On

the bottom of one of the pipettes an extension 28 in the form oi a needleis provided. 4Such extensions are used, when filling ampoules. y

The measuring apparatus together with all that belongs to it, is supported on the stand"29. The series of pipettes are held together by the strap 30. i

To the collecting tube 24 there is connected the pipe 3l, which likewise keeps its `shape unchanged at the service pressures occurring therein. The apparatus illustrated at 32 is of the kind described in connection with Fig. `2, by which the level of liquid is varied by measured amounts, and at the same time fixed. Owing to this connection the accuracy which has been assured in any case by the employment of the collecting tube 24 is substantially increased.

What I claim is:

1. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination, a measuring tube, a casing, a flexible connection between the casing and the upper end of the measuring tube for connecting and establishing open communication between the casing and the measuring tube, a bulb depending from and in open communication with the casing for drawing liquid into and expelling it from the measuring tube, a shield depending from said casing and interposed between the bulb and the flexible connection and a precision valve in the casing between the bulb and the measuring tube, said precision valve having manual actuating means therefor arranged in proximity to the bulb so as to enable the bulb and the precision valve to be actuated by the same hand for adjusting and precisely xing the liquid level in the measuring tube.

2. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected tol said measuring tube for varying the pressure in the interior of the tube to draw fluid into and expel it from the measuring tube, a precision valve interposed between said pump and the measuring tube and having actuating means therefor arranged so as to be actuatable by the hand actuating the pump for adjusting and precisely fixing the liquid level in the measuring tube, and an additional pump in open communication with the measuring tube and interposed between the precision valve and the measuring tube for displacing the liquid to enable the liquid level in the measuring tube toi be varied when the precision valve is closed.

3. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected to said measuring tube for Varying the pressure in the interior of the tube to draw fluid into and expel it from the measuring tube, a precision valve interposed between said pump and the measuring tube and having actuating means therefor arranged so as to: be actuatable by the hand actuating the pump for adjusting and precisely fixing the liquid level in the measuring tube and a manually actuatable pump connected to the measuring tube and interposed between the precision valve and the measuring tube for displacing the liquid to enable the liquid level in the measuring tube to be varied when the precision valve is closed.

4. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected to said measuring tube for varying the pressure in the interior of the tube to draw iluid into and expel it from the measuring tube, a precision valve interposed between said pump and the measuring tube and having actuating means therefor arrangedA so as to be actuatable yby the hand actuating the pump for adjusting and precisely fixing the liquid level in the measuring tube and a plurality of manually actuatable pumps of different size connected to the measuring tube and interposed between the precision valve and the measuring tube for displacing the liquid to enable the liquid level in the measuring tube to be varied with different degrees of iineness after the precision valve is closed.

5. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected to said measuring tube for varying the pressure in the interior of the tube to draw fluid into and expel it from the measuring tube, a precision valve interposed between said pump and the measuring tube and having actuating means therefor arranged soy as to be actuatable by the hand actuating the pump for adjusting and precisely xing the liquid level in the measuring tube, and a plurality of manually actuatable pumps of diierent size connected to the measuring tube and interposed between the precision valve and the measuring tube, each of said pumps having a separate adjusting member, the individual adjusting members being adapted to vary the adjustment of the respective pumps with a different degree of neness for displacing the liquid to enable the liquid level in the measuring tube to be varied with different degrees of fineness after the precision valve is closed.

6. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected to said measuring tube for varying the pressure in the interior of the tube to draw fluid into and expel it from the measuring tube, a precision valve interposed between said pump and the measuring tube and having actuating means therefor arranged so` as to be actuatable by the hand actuating the pump for adjusting and precisely fixing the liquid level in the measuring tube, and a plurality of manually actuatable diaphragm pumps of different size connected to the measuring tube and interposed between the precision valve and the measuring tube for displacing the liquid to enable the liquid level in the measuring tube to be varied with different degrees of iineness after the precision valve is closed.

7. Apparatus for measuring very small quantities of liquids with extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected to said measuring tube for varying the pressure in the interior of the tube to draw fluid into and expel it from the measuring tube, a precision Valve interposed between said pump and the measuring tube and having actuating means therefor arranged so as to be actuatable by the hand actuating the pump for adjusting and precisely fixing the liquid level in the measuring tube and a plurality of manually actuatable diaphragm pumps of different size connected to the measuring tube and interposed between the precision valve and the measuring tube, each of said diaphragm pumps having a separate adjusting member, the individual adjusting members being adapted to vary the adjustment of the respective diaphragm pumps with a different degree of fineness ior displacing the liquid level in the measuring tube to be varied With different degrees of iineness after the precision valve is closed.

8. Apparatus for measuring Very small quantities of liquids With extreme accuracy, comprising in combination a measuring tube having a capillary lower end, a manually actuatable pump connected to said measuring tube for varying the pressure in the interior of the tube to draw iiuid into and expel it from the measuring tube, a precision valve interposed between said pump and the measuring tube and having actuating means therefor arranged so as to be actuatable by the hand actuating the pump for adjusting and precisely iixing the liquid level in the measuring tube, a plurality of manually actuatable pumps of diierent size connected to the measuring tube and interposed between the precision Valve and the measuring tube, each of said pumps having a separate adjusting member, the individual adjusting members being adapted to vary the adjustment of the respective pumps with a different degree of neness for displacing the liquid in the measuring tube to enable the liquid level to be Varied with different degrees of iineness after the precision valve is closed, the said adjusting members being located in proximity to one another so as to enable the actuation of the different adjusting members to be eected with one hand.

ISTVN sZCsI.

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