US3453162A - Method of and apparatus for lining paper containers - Google Patents

Description

v vJuly 1, 196.9 H.. M. TURNER 3,453,162

METHOD OF' AND APPARATUS FOR LNTNG PAPER CONTANERS HOWARD M. TURNER BY M AGENT July 1, 1969 H. M. TURNER 3,453,162

METHOD OF AND APPARATUS FOR LINING PAPER CONTAINERS /NvENToR ro Q HOWARD M. TURNER E 1- 1o y e s @Y a ,54 6M AGENT July l, 1969 H. M. TURNER 3,453,162

` I METHOD OF AND APPIARATUS FOR LINING PAPER CONTAINERS med gan. 10. 196s sheet 3 of s INVENTOR HOWARD M. TURNER AGENT United States Patent U.S. Cl. 156--160 15 Claims ABSTRACT OF THE DISCLOSURE An apparatus and method for lining a paper container in which a hot thermoplastic lilm i's draped across a container mouth curl and drawn into the interior of the container and over the mouth curl to provide a coated surface exposed to the material placed in the container and exposed to the lips of a person drinking from the container.

This invention relates to the lining of paper containers such as, for example, paper drinking cups and cottage cheese tubs, with a substantially fluid impervious lining material.

In accordance with one present-day practice, :such containers are rendered moisture impervious by dipping them in a molten Wax and then allowing the excess wax to run ofi land the wax that remains thereon to harden. This method of coating the containers has several disadvantages. One of the primary disadvantages is that the wax coating material commonly employed is relatively expensive and adds appreciably to the cost of a finished container. Another disadvantage is that in ord-er to assure complete coverage, the wax coating material is usually applied rather heavily which also tends to increase the expense of the completed container. A still further disadvantage of such wax coatings is that they are prone to crack when the container is flexed at low temperatures and are subject to removal by abrasion, such as, for example, with respect to a cottage cheese tub, when the edge of the spoon employed to remove the cottage cheese contacts the interior container wall surfaces. A still further disadvantage of such wax coated containers is that they are not suitable for such hot products as coffee or cocoa or for other products that must be hot lled even though subsequently chilled.

In order to overcome the above enumerated disadvantages of wax coated paper containers, .a now commonly used practice was resorted to which involves heat and pressure bonding of a relatively moisture impervious plastic film material to one or both sides of the paper strip material that will subsequently be blanked out into conta-iner body and bottom portions. Such container bodies are then formed about a mandrel usually into a circular tapered shape and opposed overlapping marginal edges are either heat sealed or adhesively bonded together so as to`form an axially extending container side seam. The blanked out bottom portion is bent around its marginal edge approximately 90 so as to form a depending flange at the marginal edge. The flanged container bottom is then inserted into the bottom end of the formed container body portion and the container body portion is bent around the depending flange of the bottom wall or panel of the container so as to provide a 'hook flange configuration into which the bottom panel liange fits. The hook seam thus formed is usually bonded either with a separate adhesive coating yor by heat sealing the plastic film material. The container is completed upon the curling of the raw cut edge defining the mouth of the container so as to provide a well-rounded container mouth with the raw edge being first curled outwardly and ice downwardly and then inwardly and upwardly so that it is hidden from view. The thus formed container has certain advantages over the wax coated container but it also has certain objectionable drawbacks. As an example, if the cut edge of the container body blank that forms the interior edge of the longitudinally extending container sid-e seam is not coated with a substantially moistured impermeable material, the fluid container contents will penetrate through this edge making the paper soggy and unsightly and diminishing its strength. It is known art to either spray or dip coat this edge of the container body blank by forming a block of such blanks in the flat like a deck of playing cards and then spraying or dipping the appropriate block edge so as to coat the same with a plastic coating material. After the stack of blanks is thus coated and has dried for a suliicient period of time, the stack is racked to break the bond between the individual blanks at the coated edge. Although this system is effective to seal the edge of the blank against fluid penetration, there still remains a portion of fluid in the container leaking out through voids in the adhesive usually employed to bond the container side seam. Suc'h voids in the adhesive also may exist in the hook seam which joins the container `body wall and container bottom panel. In this respect, the wax type of container coating was more effective in that the wax sealed the cut edge forming the interior container side seam as well as any crevices through the adhesive bonding the .side seam and the hook seam. Even when the joints of the container are heat sealed together rather than adhesively bonded, there is still the problem of discontinuities existing in the heat seals.

In order to overcome both the objections arising out of the use of wax coatings and containers manufactured from container components blanked out of priorly coated strip material, a technique was devised for lining the otherwise finished container-s with a film of thermoplastic material. In accordance with this practice, a thin iilm of thermoplastic material is positioned across the mouth of the container in air tight relationship and then heated to soften it. A vacuum is then drawn under the film through either the container bottom panel, the container side wall or both. As the air is evacuated from the interior of the container, atmospheric air above the thermoplastic film material forces it down into the container until it comes into tight engagement with the interior container wall surfaces. It is believed to be readily apparent that when employing this technique, that any crevices existing in the `seams joining the 4container together will be effectively covered over with the film, thus eliminating this problem priorly encountered in the manufacture of plastic lined containers. Other problems were encountered, however, making this technique not entirely satisfactory. It was found that when the film was sealed in a lrather taut manner across the mouth of the container and then drawn into the container employing vacuum through the container wall alone, that the film tended to ro'll down the container -side wall so as to be at substantially its initial thickness at the upper end of the container and tapered in thickness so as to be very thin at the peripheral junction between the container side wall and bottom panel and also over the entire bottom panel. This unequal distribution of the plastic coating is, of course, very objectionable in that it is thinnest adjacent the wall portions of the container where protection is most needed and heaviest adjacent the top of the container side wall where the pressure exerted by the fluid contents of the container will be the least. In order to achieve a more even wall thickness, mechanical assist plugs were resorted t0 which force the 4heated film down into the interior of the container prior to drawing Vacuum through the container walls. This had the desired effect of thinning out the pla'stic film in the upper side wall area and leaving a film of heavier gauge for covering the critical area in the vicinity of the juncture of the container side wall and bottom panel and also for covering the bottom panel. Such assist plugs are mechanically operated devices and are not entirely satisfactory in that if operated too rapidly or if the plastic is not properly heated, they might rupture the film. In any event, they represent an added piece of equipment that it would be desirable to eliminate. Still another problem encountered when using this technique is that the curl defining the mouth of the container is not covered around its entire periphery with the film lining material so as to present the most attractive curl and also to seal the crevice formed between the curl end and the Iouter container side wall. It is desired that this crevice be sealed in order to prevent the entrance of foreign matter. In the case of a paper drinking cup, it is highly desirable that the curl be coated on its under peripheral surface as this surface contacts the lower lip uf a person drinking from the cup and the smooth feel provided by a plastic coating is highly desirable and is a good selling point opposed to the tacky feel imparted -by exposed paper in this area of the curl. Still another disadvantage encountered when using this technique is that the original heat used in manufacturing the film is completely lost in that roll stock film is used that must be reheated to soften it after it has been placed over the open mouth of the container. The wasting of the heat energy employed in the -initial manufacture of the film necessarily adds to the expense of the completed container. The apparatus employed for carrying out this method of lining containers was rather clumsy and not entirely satisfactory in that it employed a die set comprising a lower cavity containing portion into which the containers to be lined were placed and an upper vertically reciprocable die closing portion used to clamp the plastic film and also to heat it. This upper die closing portion represented an additional piece of equipment that it was necessary to move upwardly out of the way a considerable distance during the positioning of the containers in the cavities in the lower die portion and also during the removal of the Ilined containers.

The present invention particularly relates to the lining of otherwise finished containers generally in accordance with the broad teachings of the last of the prior art methods just described above. However, all of the disadvantages enumerated above have either been substantially or entirely eliminated. In accordance with the method of the invention, a curtain of molten or semi-molten plastic material is extruded vertically downwardly. A horizontally movable carriage is provided that includes a cavity block which contains cavities into which the containers are placed prior to coating. In operation, the containers are placed in the cavities in the cavity block and the carriage is moved into the falling curtain of film at a speed sufficiently slow so as to allow the falling film to drape over the upper wall surface of the cavity block and down into the container mouths that project through the upper surface of the cavity block. The cavity block is provided with suitable passageways through which 'a vacuum source is connected to selected container wall portions for evacuating the air from the interior of the containers. As the hot plastic curtain `or film drapes itself completely over the curl defining the container mouth rim so as to seal off the interior of the container, the removal of air from the container results in atmospheric air above the film forcing the film the rest of the way down into the container to completely line the interior thereof. The carriage also employs heated wires mounted across opposite ends thereof in parallel relationship with respect to the falling film so that as the carriage advances into the film, the leading hot wire will sever the film and after the portion of the film being extruded that drapes over the carriage and into the containers has been completely draped over the carriage, the trailing edge thereof will be severed by the rear hot wire on the carriage. Further, in accordance with the invention, the under surface of the curl defining the mouth rim of the containers projects upwardly somewhat from the upper wall surface of the cavity block so as to provide space for vacuum drawing that portion of the film that is draped downwardly around the outermost periphery of the curl completely around the under surface of the curl and in engagement therewith and also in engagement with at least a portion of the container side wall adjacent the curl; the vacuum drawing being effected by the provision of an annular vacuum groove at the juncture of the top wall surface of the carriage cavity block and the upper side wall of the container carrying cavities. It will be apparent that with this arrangement the film is manufactured or extruded at a high enough temperature to render it fiowable and it is draped over and down into the containers and drawn by vacuum into intimate contact with the interior container walls and also around and in intimate contact with the mouth defining curl without any intermediate cooling of the film taking place. This direct employment of the freshly extruded curtain of plastic represents a saving in that the former reheating of the thermoplastic film material is now no longer needed. It represents a still further saving in that the handling of the formerly used rolls of film stock and the storage of the rolls prior to use is now completely eliminated. The apparatus has been simplified in that the upper die portion formerly employed to seal the plastic film material and to heat it to the proper forming temperature is not necessary and has therefore been eliminated. Further, in accordance with the invention, the mouth defining curl of the container is completely covered with the plastic film and the crevice between the end of the curl and the outer container side wall is bridged by the film, sealing it off against the entry of foreign matter. The method and apparatus of the invention also effectively overcomes the problem of the film thinning out excessively in the area of the juncture of the container side wall and bottom panel and across the bottom panel that was formerly encountered. This is achieved by moving the carriage containing the containers at such a speed in a direction transverse to the falling curtain of film to permit the film to drape down into the containers at substantially original thickness, an amount sufficient so that when the film has been completely draped around the mouth of the container so as to seal the interior of the container, the completion of the lining operation by the additional drawing down of the film against the container side walls by means of the vacuum being applied against selected container wall surfaces will not result in objectionable thinning of the film.

With the above explanation of the deficiencies in the prior art methods and apparatus for lining paper containers in mind, it is a general object of the invention to provide a method of lining paper containers or the like comprising the steps of draping a hot film of thermoplastic material across the mouth rim of the container so that the film initially drapes down into the container a considerable distance and subjecting selected wall portions of the container -to vacuum conditions so as to cause the film material to be drawn down into engagement with the interior wall surfaces of the container upon the completion of the draping of the film material over the entire mouth rim of the container.

Another object of the invention is the provision of a method of lining paper containers or the like with thermoplastic material comprising the steps of providing a substantially vertically extending thin curtain of hot thermoplastic material and by relative horizontal movement between the curtain of plastic and a container to be lined progressively draping the plastic curtain across the mouth rim of the container and evacuating the air entrapped in the container beneath the plastic curtain through selected wall portions of lthe container so as to effect the drawing down of the curtain of fil-rn into intimate contact with the interior wall surfaces of the container.

Still another broad object of the invention is to provide a method of lining paper container or the like with a film of thermoplastic material which comprises; vertically downwardly extruding a continuous curtain of molten thermoplastic material; by relative horizontal movement between the vertically falling curtain iand a container to be lined, causing the cur-tain of molten thermoplastic material to be draped over the mouth rim of the container so that the curtain droops down into the container a considerable distance, and effecting the evacuation of the air trapped within the container -under the plastic material draped over the mouth rim thereof through wall portions of the container to draw the so draped plastic cur-tain into intimate contact with the interior surfaces of the container.

A still further broad object of the invention is to provide apparatus which includes means for providing a substantially vertically extending plasticized curtain or lm of plastic material; a carriage adapted to be reciprocated generally horizontally and normal to the curtain of plastic, said carriage including a cavity block portion which contains at least one cavi-ty into which a cont-ainer such as a'paper cup or tub is placed bottom first for lining purposes and also includes passages in communication with the container cavity or cavities.

It is further object of the invention to provide apparatus of the type immediately above described which is simple in operation, and, which can, for the most part, be fabricated from commercially avail-able components.

A still further object is to provide an improved container in which the mouth defining curl is completely covered with thermoplastic lm; the crevice existing between the terminal edge of the curl and the body wall of the cont-ainer is bridged and sealed by the film and the film terminates along the container side wall at a point closely adjacent the curl so that the terminal edge is not noticeable.

Still other and further objects of the method, apparatus and container of the invention-and particularly the more detailed objects and advantages will become apparent upon studying the following detailed description of a preferred embodiment of the invention and the drawings illustrating the described preferred embodiment of the invention.

In the drawings:

FIG. 1 is a side elevational View of -a preferred apparatus made in accordance with the invention with portions thereof being broken away and other portions thereof being in cross section in order to best illustrate the important features of the invention;

FIG. 2 is a side elevational view of the carriage of FIG. 1; the carriage being shown in cross section and to a greatly enlarged scale;

FIG. 3 is a fragmentary sectional elevation view t-aken on section line 3-3 through the portion of the carriage illustrated in FIG. 2 including the mouth defining rim of a container positioned in the carriage and at a still larger scale; and,

FIG. 4 is a view similar to FIG. 3 but showing the rim portion of a finished container as it is being ejected from the carriage.

Referring now to FIG. 1 of the drawings, it will be observed that the machine of the invention is indicated generally by the numeral 10. The machine includes a frame generally indicated by the numeral 11. The frame 11 includes a horizont-al platform portion designated at 12. It also includes a pair of transversely spaced horizontally extending parallel rails indicated at 13 and 14, In order to better illustrate the details of the invention, it will be observed that the nearer rail 13 has the center portion thereof broken away.

Mounted on the platform 12 is a vacuum pump 15, an air compressor 16, a plastic heater and a deaerator 17, a

suitable pump 20 and a plastic supply extrusion device indicated generally at 21. The extrusion device 21 includes a hopper 22 for receiving pellets of plastic material in dicated at 23. A suitable motor 24 is used to drive the extrusion device 21 in .the usual manner. The plastic pellets 23 gravitate into the extruder portion 25 of the plastic extrusion device 21 where they are melted and the molten mass of plastic is extruded by means of the usual screw extruder (not shown) in-to a discharge pipe 26. The discharge pipe 26 is preferably heated by heating means not shown in order to maintain the molten plastic therein ata desired temperature. A stream of the molten plastic indicated at 27 is discharged from the pipe 26 into a catch vbasin 30 that is suitably attached to the underside of the rails 13 and 14. A drain pipe 31 is employed to drain molten plastic material indicated at 32 from the catch basin 30 into the plastic heater and deaerator 17. Another pipe indicated 'at 33 connects the plastic heater and deaerator 17 to the suction `side of the pump 20, The discharge pipe indicated at 34 is employed to deliver deaerated molten plastic under pressure to a curtain extrusion unit generally indicated at 35 that extrudes a thin curtain of molten plastic vertically downwardly into the catch basin 30; the curtain of plastic being indicated by the numeral 36.

The curtain extrusion unit 35 is suitably supported by means of a bracket 37 to which it is attached and which in turn is attached in any suitable manner to a portion of the frame 11. The falling curtain of plastic 36 is delivered from the extrusion unit 35 through a slot 40 provided in the housing thereof indicated at 41. Although for simplicity of illustration a slot of fixed dimension is illustrated, it is to be understood that the slot 40 may be of the adjustable type so that the thickness of the plastic curtain 36 can be varied as desired. Another alternative is to provide a slot such as slot 40 in a removable plate that attaches to the housing 41 thus permitting the attachment and removal of slot plates containing slots of various dimensions. Housing 41 is completely filled with molten plastic indicated at 42 which is maintained at a desired temperature for extrusion by means of a suitable heater 43. The temperature and pressure of the molten plastic 42 in the housing 41 are indicated respectively by temperature gauge 44 and pressure gauge 45 connected to the housing 41. The pipe 33, the pump 20 and the pipe 34 are preferably heated, for example, by electric resistance heaters and covered with a suitable insulating material which also may be employed to cover the housing 41. Suitable insulation may also be applied to the exterior surface of the catch basin 30 as well as around the drain pipe 31 in order to prevent unnecessary wasting of heat and also to help keep the plastic 32 in the catch basin 30 at a higher temperature so as to promote the drainage of the plastic out of the catch basin through the drain pipe 31. The catch basin 30 and pipe 31 may also be heated if desired to promote drainage. A temperature gauge 38 is employed to indicate the temperature of the plastic in the plastic heater and deaerator 17.

The carriage generally indicated by the numeral 46 is arranged for back and forth reciprocation on the rails 13 .and 14. The carriage 46 includes a cavity block p0rtion 47 which also functions as a frame for supporting the wheels 50 rotatably mounted on brackets 51 that depend therefrom. Although only two wheels are visible in FIG. l, it is to be understood that four wheels 50 are provided on the carriage 46, two of which are adapted to roll along the rail 14 with the other two forming a pair adapted to roll along the rail 13. Also suitably attached to the cavity block 47 and depending therefrom is bracket S2 adapted to receive and hold the end of a piston rod 53 that is a part of an air cylinder unit generally indicated at 54. The air cylinder unit 54 includes a cylinder portion 5S as well -as an electrically Operated four-way air-flow control valve 56, the actuation of which controls the reciprocating movement of the piston rod 53 in a manner well known to the art.

Compressed air at a desired pressure as read on the air pressure gauge 57 provided on the air compressor 16 is delivered to the four-way valve S6 through pipe 60, T 61, pipe 62, elbow `63 and pipe 64. Suitable air-liow control needle valves are provided in the air cylinder unit 54 for controlling the speed of the piston rod 53; such air-flow control valves being entirely conventional. The cylinder portion of the air cylinder 54 is attached by means of suitable fasteners 65 and 66 to the rail 14. Piston rod 53 therefore attaches to the carriage 46 at the far side thereof as viewed in FIG. 1 and above the rail 14 so that it will clear lthe far edge of the falling curtain of molten plastic 36 as carriage 46 is reciprocated back and forth through and beyond the plane of the curtain 36. The width of the carriage 46 in the direction transverse to the direction of movement of the carriage as indicated by the double-ended arrow 67 is approximately co-extensive with the transverse spacing of the rails 13 and 14. The length of the extrusion slot 40 also in the same transverse direction is necessarily somewhat smaller than the inside to inside distance between the rails 13 and 14 so that the curtain 36 of molten plastic will pass with sufficient clearance between the rails 13 and 14 to ensure that in the operation of the machine 10 there will be no danger that the curtain 36 will contact the rails 13 and 14.

Also connected near the far side of the carriage 46 as viewed in FIG. 1 in a position approximately above the rail 14 and thus clearing the far edge of the plastic curtain 36 is a vacuum and air supply hose 70. An arm 71 supported on the bracket 37 is provided with a hanger 72 employed to support the hose 70. Hose 70 is connected to the vacuum pump 15 through a T 73 and pipe 74 which contains an on-off valve 75. The degree of vacuum produced by the vacuum pump 15 may be adjusted as desired and is indicated on the vacuum gauge 76. Compressed air is supplied to the hose through the T 73, pipe 77, T61 and pipe 60 from the air compressor 16. The pipe 77 is provided with an air pressure regulator 80, an on-olf valve 81 and an air pressure gauge 82. The air pressure regulator regulates the pressure of the air delivered to the hose 70 but does not influence the pressure of air supplied to the valve 56 as read on the gauge 57 and as controlled by adjustments on the air compressor unit 16.

Reference will now be made to FIG. 2 in particular for an explanation of the importance of construction details of the carriage 46 which specifically relate to the advance in the art provided by this invention. It will be observed that the hose 70 is attached to a pipe nipple 83 that extends out of a vertical end wall 84 of the cavity block 47 and which communicates the hose 70 with a transverse header passage 85 that extends along the width of the cavity block 47 in a direction normal to the direction of movement of the carriage 46. Header passage 85 is in communication with at least one passage that extends through the cavity block 47 in the direction of motion of the carriage. Such a passage is indicated at 86 communicating with a pair of container cavities indicated at 87 and 87', by means of a plurality of bores 90 and 90 disposed in circularly spaced relationship and opening into the bottom of the cavities 87 and 87'. It will be observed that each of the cavities 87 and 87 includes a bottom wall portion 91 and 91' that projects upwardly within the space circumscribed by the flange 92 and 92' of a paper container generally indicated at 93 and 93' and acts to support the bottom panel 94 and 94 of the respective containers 93 and 93'. Container cavities 87 and 87' also have respective tapered side wall portions 95 and 95'. Containers 93 and 93 have respective body portions 96 and 96' that include side wall portions 97 and 97', the outer surface of which closely fits the cavity side wall portion 95 and 95'. At the upper end, the side wall portion 97 and 97' of each of the containers 93 and 93' is curled outwardly and downwardly and then inwardly and upwardly so as to form a curled container mouth defining rim indicated at 100 and 100. Opposed marginal edges of the container body portion are overlapped and bonded together so as to form an axially extending side seam indicated at 98 and 98'.

It will be observced that in the cavity 87 the upwardly extending bottom die portion 91 is somewhat smaller in diameter than the diameter between the opposite interior faces of the container flange 92 so that an annular chamber 101 is formed into which the bores 90 open when a container 93 is placed in the cavity 87. Alike chamber 101' is similarly created with respect to the cavity 87'.

In vertical communication with the header passage 85 is at least one passage 102 that opens into a larger vertically extending passage 103. At the point of juncture between the passages 102 and 103 is located a check valve generally indicated at 104 which includes a fixed orifice 105 and a vertically movable orifice closing float 106. The orilice closing float has a passageway 107 therein that permits the flow of air through the orifice 105 and into the passageway 102 when the float 106 is in the illustrated lower position thereof but which will not permit flow of air in the reverse direction from the passageway 102 into the passageway 103 when the oat is in its raised position in which it closes the orifice 105. At its upper end, the vertical passageway 103 opens into an annular chamber 110 which encompasses the cavity 87. A passageway 111 in turn connects the annular chamber 110 to a similar .annular chamber 110 that encompasses the cavity 87. A plurality of small bores disposed around the inner perimeter of the chambers 110 and 110' and opening into the respective chambers are indicated at 112 and 112'.

Referring to FIG. 3, it will be observed that the bores 112' open into an annular groove 113' at the juncture of the cavity side wall 95' and the top wall 114 of the cavity block 47.

It will also be observed that the upper wall 114 curves downwardly .as indicated at 115 as it extends outwardly from the annular groove 113' so as to provide an adequate length of lthe plastic curtain 36 draped down around the exterior of the curl 100' as indicated in dotted lines at 116 necessary to completely cover the undersurface of the curl 100' as a result of a vacuum condition being applied to the annular groove 113' during the operation of the machine 10. Not only does the downward curving of the wall 114 at 115' provide for an adequate length of draped plastic, it also provides adequate room between the underside of the curl 100 and the wall 114 for drawing the plastic curtain around the undersurface of the curl as would otherwise not be available if the wall 114 extended horizontally outwardly in the same plane as the rim defined by the intersection of the downwardly curved wall portion 115' and the upper terminal acute angled edge 118' of the annular groove 113. It will be noticed in FIG. 3 that the plastic curtain 36 when drawn tightly around and under the curl 100' bridges the gap existing between the cut end of the curl .and the adjacent exterior surface of the container sidewall 97', the gap being indicated at 117 and the cut end of the curl at 119'. The film also extends yslightly down the sidewall of the container but as a result of the curving of the wall 114 as at 115' down and away from the groove 113', the downward extend of the plastic in contact with the exterior of the container wall 97' is limited so as not to extend any appreciable amount below the lowermost point along the outer periphery of the curl 100'. When the linished container 93 is subsequently ejected from the cavity 87' during the operation of the machine 10, the plastic curtain 36 will break adjacent the edge 118 as will be discussed more fully later on. Since the broken edge of the lilm indicated at 120' in FIG. 4 that remains on the container 93' does not extend appreciably down the container side wall, it Will not be noticed by the casual observer as it otherwise would if it occurred lower down on the container side wall or .at a point on the undersurface of the curl 100' Ileftwardly from the center of the curl as viewed in FIGS. 3 and 4. The fact that the curl of the container made in accordance with the teachings of the invention is completely covered with plastic including the bridging of the gap 117 .and that Ithe terminal edge of the plastic on the side wall of the container is hidden from the view of the casual observer during normal use positions of the container, it is believed to be readily apparent that a superior container structure is achieved.

It is to be understood that section similar to the sections 3 3 taken through the cavity 87 but instead taken through the cavity 87 would be similar in all respects and the same numerals would be applicable as used in FIGS. 3 .and 4 with the exception that standard numerals would be used throughout rather than prime numerals.

With reference to FIG. 2, it will be observed that a terminal block 121 is mounted on the wall 84 of the cavity Iblock 47. A resistance Wire 122 extends 'between a pair of brackets 123 also mounted on the wall 84 .and only one of which is shown since FIG. 2 is a sectional view through the carriage. The resistance wire 122 extends substantially all the Way across the face 84 of the cavity block 47 and is parallel to the face 84 and also to the plane of kthe free falling curtain 36 and the general plane of the top wall 114 of the cavity block 47. Resistance wire 122 is electrically connected t0 the terminal block 121. Electrical energy is supplied to the terminal block and hence to the resistance wire 122 by means of a supply wire 125.

The opposite end of the carriage 46 is similarly provided with a resistance Wire indicated .at 122 positioned between similar brackets 123' mounted on a similar end wall 84. A similar terminal block 121 is also provided and energized by a wire 125' similar to the wire 125. It is to be understood that the opposite ends of the wires 122 and 122 are connected tog-ether with a suitable conductor so that a complete circuit is formed through the resistance wires 122 and 122.

Although the illustrated carriage 46 as described contains only the cavities 87 .and 87', it is to be understood that the operation is more efficient if the carriage is made larger both in width and length so as to include more cavities. As more cavities are added .across the width of Ithe machine, of course, the extrusion slot 40 would be made longer so that the extruded curtain of molten plastic 36 would be wide enough to cover the additional cavities.

In order to fully understand `the operation of the machine and the method employed during the use of the machine 10 for lining paper containes in accordance with the invention, the operating cycle of the machine will now be described.

OPERATION Referring once again to FIG. l, it will be apparent that before operation can commence, it will be necessary to rst provide the falling curtain of molten plastic 36. Since any plastic yin the system at start up will be in a solid state, it will be necessary to heat the plastic supply system by turning on the various heaters such as the heater 43 in the housing 41; the plastic heater and the deaerator unit 17 and the heater associated with the plastic extrusion device 21. As mentioned before, suitable heaters a're also provided to heat the pipes 33, 34 and 26 as Well as the pump 20. These heaters will also be activated at this time.

As the system is heating yup as indicated on various temperature gauges that may be employed such as the temperature gauge 44 on the housing 41 and the temperature gauge 38 on the plastic heater and deaerator unit 17, the machine 10 can otherwise be conditioned for operation. This would include the starting of the vacuum pump 15 and air compressor 16 and making any necessary adjustments thereto in order to obtain the desired readings `on the gauges 57 `and 76. The pressure on the gauge 82 would also be checked and regulated if necessary by the regulating valve 80. If the supply of plastic pellets 23 in the hopper 22 is not at the desired level, a fresh supply of pellets would at this time be provided.

When the temperature gauges 38 and 44 as well as any other temperature gauges employed indicate that the plastic in the system is molten and at the desired operating temperature for the type of plastic in the system, the pump 20 can be started which will cause the pressure of the plastic 42 in the housing 41 to increase as read on the pressure gauge 45 with the result that molten plastic will Ibegin to flow through the slot 40. The pressure of the plastic in the housing 41 may be varied as desired by suitable conventional adjustments provided on the pump 20. The plastic supply extruder motor 24 may now be started so as to supply a stream of fresh plastic to the system as` indicated at 27 until there is a sufficient supply of plastic in the catch basin 30 as indicated at 32 to insure that the system will not be short of plastic. The plastic supply extruder unit 21 may be subsequently turned off and then used only as necessary during the operation of the machine 10 to replace the plastic being used in the lining of the containers.

After the extrusion of the molten curtain of lm 36 has continued for the necessary length of time to stabilize the temperature and pressure conditions in the extrusion unit 35, nal temperature and pressure adjustments are made to assure that the iilm or curtain of molten plastic 36 has the necessary physical characteristics allowing it to drape down into the containers and to be vacuum drawn into -contact with the container walls without breaking. It is to be understood that the desired temperature and pressure conditions of the plastic 42 in the extrusion unit 35 will vary with the type of plastic being used as well as with the thickness of the curtain being extruded as determined yby the width of the slot 40.

In one operational set up of a machine such as the machine 10, the plastic material used was cellulose butyrate and the temperature of the plastic in the extrusion unit 35 was maintained at approximately 320 F. as read on the gauge 44. The plastic heater and deaerator 17, the pump 20 and also the pipes 33 and 34 were similarly maintained at a temperature of approximately 320 F. The pressure of the plastic 42 in the housing 41 as read on the pressure gauge 45 was maintained at approximately 75 p.s.i. A vacuum of approximately 20 inches of mercury was maintained as read on gauge 76. Coatings were varied from l-5 mil thickness. As previously explained, the thickness of the lm can be varied by eniploying an adjustable extrusion slot or removable extrusion slots. In another operational arrangement used, the plastic material was a polyethylene copolymer extruded at 1/2-25 mils in thickness with the extrusion unit 35 being maintained at approximately 315 F.

It will be apparent that during operation of the apparatus that if the falling curtain 36 does not have suicient strength because it is too hot, but is being extruded at the desired rate, the necessary corrective action would be to lower the temperatire of the plastic in the extrusion unit 35 while simultaneously increasing the pressure therein so as to prevent the extrusion rate from falling off due to the increasing viscosity of the plastic as a result of the lowering of the temperature thereof.

Once the falling curtain of plastic 36 has been established and stabilized so as to reliably exhibit the desired strength and extrusion rate characteristics, containers to be lined such as the containers 93 and 93' can now be placed in the carriage 46. As shown in FIG. 1, the carriage 46 is positioned at the endmost extent of its travel to the right with the piston rod 53 being fully retracted in the air cylinder unit 54. At this time, the position of the valves 75 and 81 should be ascertained, as valve 75 should be open and valve 81 closed so that a vacuum condition will exist in the hose 70. Operation of the electrically operated 4way valve 56 of the air cylinder unit 54 will now cause the carriage 46 to begin moving leftwardly into the path of the falling curtain of plastic 36. After a short length of travel, the resistance wire 122 which is heated to a relatively high temperature will sever the curtain of plastic 36 so that that portion of the curtain 36 below the level of the resistance wire 122 will fall down into the catch basin 30. As the carriage 46 continues to advance leftwardly, the portion of the film 36 above the resistance 4wire 122 progressively drapes itself over the top wall 114 of the cavity block portion 47 of the carriage 46. As the curtain of film 36 progressively drapes down into the leading container 93, it also progressively covers the upwardly projecting mouth defining container rim. When the rim has been completely covered, the interior of the leading container 93 is sealed against entrance of atmospheric air and the vacuum condition in the hose 70 becomes effective through the various passageways discussed in regard to the explanation of FIG. 2 to evacuate the air trapped under the portion of the film 36 draped in the container 93 resulting in this portion of film vbeing drawn into intimate contact with the walls of the container 93. Further leftward movement of the carriage 46 results in the curtain of plastic 36 being likewise draped down into the container 93 and vacuum drawn into contact with the walls of the container 93. Finally, the trailing portion of the curtain of plastic 36 is severed by the heated resistance wire 122 and the carriage passes completely beyond the plane of the extrusion slot 40 and the -curtain 36 once again becomes continuous all the way down into the catch basin 30. At this furthermost leftward position of the carriage 46 at which the piston rod 53 is fully extended out of the air cylinder unit 54, the carriage 46 will remain stationary until the valve 56 is again actuated.

In order to eject the freshly lined containers 93 and 9'3 from the carriage 46, the vacuum supply valve 75 is now closed and the air supply valve 81 opened so as to supply compressed air into the hose 70 at the proper pressure as read on the gauge 82. The compressed air enters certain of the various passageways in the carriage 46 as discussed in the explanation of FIG. 2 and acts to force the containers 93 and 93' out of the carriage 46. Upon ejection of the containers, the positions of the valves 75 and 81 are reversed so that vacuum is again applied to the hose 70. It is to be understood that the operation just described is rather general in character and in order to fully understand the fine points of the invention, it will he necessary to refer to FIG. 2 which shows a container lining operation in progress during the return stroke of the carriage from left to right as indicated by the directional arrow so that at the end of the lining operation, the carriage will be back in the position indicated in FIG. l.

Referring back now to FIG. l, it Will be remembered that the carriage `46 is now positioned at the end of its leftward stroke and is ready for recharging with fresh containers 93 and 93 to be subsequently lined. Such containers are now placed in the carriage and the 4-Way valve 56 then operated causing the retraction of the piston rod 53 into the air cylinder unit 54 resulting in the rightward movement of the carriage 46. As carriage 46 approaches the curtain of plastic 36, the heated wire 122' cuts the curtain 36 and that portion of the curtain of plastic 36 above the wire 122 begins to drape over the carriage.

With specific reference now to FIG. 2, it will be observed that as carriage 46 advances to the right, a p0rtion of the curtain of plastic indicated in dotted lines at 126', progressively droops down into the container 93 until the mouth defining curl or rim of the container 93' which is indicated at is completely covered with the curtain. Since vacuum is simultaneously being applied to the annular chamber 101 through the bores 90', passageway 86 and transverse header passageway 85 connecting with the hose 70, it will be apparent that the air trapped below the draped portion of plastic film 126 will be evacuated through the annular area of the porous paper container bottom panel 94 that forms the upper Wall of the annular chamber 101 when the container 93 is in place in the cavity 87'. When the air is completely evacuated in this manner from the container 93', the film portion 126' will be drawn into intimate contact with the interior surface of the side wall portion 97' and bottom panel 94 of the container 93'. It will also cover the juncture between these surfaces indicated at 127. Vacuum from the hose 70 is simultaneously applied through the vertical bore 102, the check valve 104, vertical bore 103 annular chamber 110, connecting passageway 111 annular chamber and bores 112 to the annular groove 113 as indicated by the air ow arrows in FIG. 3. With continued reference to FIG. 3, it will be remembered that as the curtain 36 drapes about the container mouth defining curl or rim 100', it will be initially disposed as indicated at 116. When the film is draped down around the entire outermost periphery of the curl as at 116 vacuum being drawn on the annular groove 113' becomes effective to draw the draped portion of film 116' completely around the underside of the curl 100' so as to cover this critical area of the curl with plastic. As plastic is drawn around the curl, it thins out as exaggeratedly illustrated and also bridges the gap 117' that exists between the cut edge of the curl and the outer surface of the container side wall portion 97; the cut edge being indicated at 119". As will be further observed in FIG. 3, the film also extends down along the container side wall to a point only very slightly below the lowermost point on the curl 100 and even with the annular acute angled edge 118 of the groove 113'. The plastic is also brought into intimate engagement with the downwardly curved wall portion of the wall 114. As will be observed from the air flow arrows of FIG. 3, air is evacuated through the porous paper container side wall portion 97 from the space existing in the interior of the curl 100' which has the effect of drawing the film into very tight engagement with the exterior surfaces of the curl including the undersurface of the curl, and slightly up into the gap or crevice 117 existing between the container wall and curl so as to provide a very tightly covered and neatly appearing container mouth rim.

Referring once again to FIG. 2, it will be seen that as the carriage 46 continues its rightward movement, the curtain 36 bridges the wall portion 114 between the cavities 87 and 87 and progressively drapes itself down into the container 93 as indicated at 126 in exactly the same manner as previously described in connection with the container 93'. Upon completion of the lining of the container 93 the trailing heated Wire 122 severs the curtain of film 36 and the carriage moves a little further to the right beyond the plane of the curtain 36 where it comes to rest at the end of its stroke.

Ejection of the container is now accomplished by closing the vacuum valve 75 of FIG. 1 and opening the air valve 81. This will supply compressed air in the hose 70 to selected passageways in the carriage 46 as will be described with reference to FIG. 2. Compressed air will be supplied to the transverse header passage 85 from the hose 70 and in turn through the passageway 86 and bores 90 and 90' to the annular chambers 101 and 101' for effecting the ejection of the containers 93 and 93 out of their respective cavities 87 and 87. Simultaneously, compressed air is supplied from the header passage 85 to the vertical bore 102. This results in the raising of the orifice closing float 106 into the fixed orifice 105 in orifice closing relationship. Since the vertical passageway 103 above the orifice 105 is relatively large, as are the annular chambers 110 and 110 and connecting passage 111, it will be apparent that the small amount of air that passes upwardly through the orifice 105 before the orifice is closed will be insufficient to materially decrease the vacuum condition existing in these passageways above the orifice 105. Vacuum thus continues to be applied to the annular grooves 113 and 113 during the ejection of the containers. It will be apparent from FIGS. 3 and 4 that at this time, the vacuum will be effective to apply a downward force on the film that bridges the gap between the acute angle edge 118 and the outer container side wall. By thus holding the film under downwardly biased tension at this point, it will be apparent that during ejection of the container as illustrated in FIG. 4 the, film will break closely adjacent the acute angle edge 118'. The broken edge of the film indicated at 120 that remains on the outer container side wall, it will be observed in FIG. 4, does not extend appreciably below the lowermost point of the curl 100 and therefore, as explained before, this edge, which may be somewhat ragged, will not normally be visible to the casual observer during use of the container.

In a modified method of operating the machine 10, the vacuum supply valve of FIG. l would be in its closed position during the movement of the carriage 46 for the purpose of draping the curtain 36 across the top of the carriage and down into the containers therein. The valve 75 during such an operation would be opened immediately after the film was draped over the carriage and the carriage had come to rest at the end of its stroke. When the valve 75 is so opened, it will be apparent that with reference to FIG. 2, the portions of the curtain of plastic 36 indicated at 126 and 126' draped ldown into the respective containers 93 and 93' will simultaneously be drawn down by vacuum to cover the interior of the containers, rather than in the previously explained sequential manner. It will also be apparent that modifications of the illustrated machine within the spirit and scope of the invention will also become obvious to those skilled in the art upon reading the foregoing description and examining the drawings. For example, it will be readily apparent that the carriage 46 could be mounted in a fixed position and the curtain extrusion unit 35 as well as the catch basin 30 and related apparatus arranged to reciprocate back and forth on a carriage by means of an air cylinder unit similar to the air cylinder unit 54 past the now fixed carriage 46.

I claim:

1. A method of lining a container with plastic film comprising the steps of extruding a sheet of hot plastic film vertically downward; moving a container carriage in a horizontal direction; passing a horizontal hot wire through said sheet of plastic film to sever said film; progressively draping the sheet of hot plastic film across a mouth defining rim of a container in said carriage so that the film drops down into the container;

passing a second horizontal hot wire through said sheet of plastic film to sever said film again;

removing the air from the space between said film segment and said container whereby said film is drawn into contact with the interior wall surface of said container; and

ejecting said container from said carriage by developing air pressure under said container whereby said film is broken along a peripheral line of the exterior surface of said container.

2. A method of lining a container with plastic film as set forth in claim 2 with the additional step of:

reciprocating said carriage backward and forward, re-

peating the above steps at each reciprocation of said carriage. 3. A method of lining a container with plastic film cornprising the steps of .providing a vertically disposed moving curtain of hot thermoplastic material;

moving a container carriage in a horizontal direction;

passing a hot wire through said sheet of plastic film to sever said film;

progressively draping the sheet of hot plastic film across a mouth defining curl of a container mounted on said carriage and downwardly from the outward periphery of the curl;

passing a hot wire through said sheet of plastic film to sever said lm and form a film segment;

removing the air from the space between said film segment and said container whereby said film is drawn intocontact with the interior wall surface of the container; and

breaking away a marginal waste portion of said plastic film along a peripheral line of the exterior surface of the container closely adjacent the undersurface curl.

4. The method of lining a container with plastic film as set forth in claim 3 comprising:

reciprocating said carriage backward and forward, re-

peating the above steps at each reciprocation of said carriage.

5. A method of lining a container having an outwardly directed curl defining a mouth opening with plastic film, comprising the steps of: v

providing a vertically disposed curtain of hot thermoplastic material;

moving the container carriage in a horizontal direction;

burning said sheet of hot plastic film through with a horizontal hot wire attached to the front of said carriage;

applying the sheet of hot plastic film across a mouth defining curl of said container mounted on said carriage and downwardly from the outermost periphery of the curl;

burning a second edge of said plastic film through with a second hot wire located on the other end of said carriage; and

removing the air from the space between said film and said container whereby said film is drawn into contact with the interior wall surface of said container and into contact with the entire outer surface of said curl and with a portion of the exterior surface of the container adjacent the curl.

6. A method of lining a container having an outwardly directed curl defining a mouth opening comprising the steps of:

providing a sheet of hot plastic film moving downward;

moving a container carriage in a horizontal direction;

burning said sheet of hot plastic film through with a horizontal heat source attached to the front of said carriage;

draping an expanse of hot plastic film across the mouth defining curl and downwardly from the outermost periphery of the curl to a point below the lowermost extent of the curl;

removing the air from the space between said film and said container whereby said film is drawn into contact with the interior wall surface of said container, with the entire outer surface of said curl, and with a portion of the exterior surface of said container adjacent the curl;

burning said plastic lm through with a heat source to form a second edge on the other end of said carriage; and

breaking away marginal waste portions of said plastic film along a peripheral line of the exterior surface of the container closely adjacent the undersurface of said curl.

7. A method of lining a container having an outwardly 15 directed curl defining a mouth opening as set forth in claim 6 comprising the additional step of reciprocating said carriage backward and forward while repeating the above steps at each reciprocation of said carriage.

8. Apparatus for lining paper containers having a mouth defining circumferential rim comprising: means for providing an expanse of heated thermoplastic film; cavity containing means having a cavity into which a container to be lined is placed with the mouth opening upwardly out of the cavity; means for creating relative converging movement between the film and cavity containing means to effect the free draping of the film over the mouth of the container, and means for drawing the draped film into contact with the interior Wall surfaces of the container.

9. The apparatus of claim 8 in which the means for providing an expanse of heated thermoplastic film is an extrusion device having a horizontally extending extrusion slot disposed to vertically downwardly extrude an expanse of hot thermoplastic film.

10. The apparatus of claim 9 in which the means for creating relative converging movement between the film and cavity containing means includes means for creating relative horizontal motion between the cavity containing means and the extrusion slot to effect the relative movement of the cavity containing means into, through, and beyond the plane of the extrusion slot and the downwardly falling film, resulting in the free draping of the film over the mouth of the container.

11. The apparatus of claim 10 in which the means for creating relative horizontal motion between the cavity containing means and the extrusion slot includes means for reciprocating the cavity containing means horizontally into, through, and beyond the plane of the extrusion slot.

12. The apparatus of claim 11 in which the means for drawing the draped film into contact with the interior wall surfaces of the container includes passageways in the cavity ocntaining means communicable with a source of vacuum and communicating with a lower portion of the cavity.

13. The apparatus of claim 12 in which the said passageways are also communicable With a source of compressed air for ejecting a lined container.

14. The apparatus of claim 12 in which additional passageways are provided in the cavity containing means, said additional passageways being communicable with the said passageways communicable with a source of vacuum -and also with a mouth defining edge of the cavity, and, when in communication with the vacuum source, effecting the drawing of a portion of the draped film extending down and about the exterior of the container rim into intimate contact with exterior portions of the container rim.

1S. The apparatus of claim 13 in which additional passageways are provided in the cavity containing means, said additional passageways being communicable with the said passageways communicable with a source of vacuum and a source of compressed air and also with a rim defining edge of the cavity; and a check valve preventing the said additional passageways from communicating with the said passageways communicable with a source of vacuum and a source of compressed air when in an operative position effected only by the presence of compressed air in the said passageways communicable with a source of vacuum and a source of compressed air; said additional passageways, when in communication with the vacuum source effecting the drawing of a portion of the film extending down and about the exterior of the container rim into intimate contact with exterior portions of the container rim, and said check valve being effective to maintain a vacuum condition in the additional passageways when compressed air is applied to the said passageways communicating with a lower portion of the cavity for ejecting a container, resulting in the breaking of the film about the exterior of the container.

References Cited EARL M. BERGERT, Primary Examiner.

J. C. GIL, Assistant Examiner.

U.S. Cl. X.R.

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