US3695900A - Evacuated hermetically sealed package with semirigid shell and stretchable closure - Google Patents

Abstract

EVACUATED HERMETICALLY SEALED PACKAGE COMPRISING A TOP OF STRECTHABLE PLASTIC FILM SEALED TO A SEMI-RIGID SHELL CONTAINING A PRODUCT WITH THE STRETCHABLE TOP IN TIGHT CONTACT WITH THE UPPER SURFACE OF THE PRODUCT. THE PACKAGE IS FORMED BY APPARATUS INCLUDING A PACKAGING HEAD HAVING PRELIMINARY AND FINAL SEALING MEANS. THE PRELIMINARY SEALING MEANS INCLUDE HEAT SEAL BARS EXTENDING PART WAY AROUND THE PERIPHERY OF THE SHELL AND A HEATING ELEMENT MOUNTED WITHIN THE SPACE INTERIORLY OF THE SEAL BARS WHICH SOFTENS THE TOP AND RENDERS IT READULY STRETCHABLE IN THE AREA INBOARD OF THE SEAL LINE. FINAL SEAL MEANS INCLUDING AN EVACULATING CHAMBER AND MEANS TO COMPLETE THE SEAL BETWEEN THE TOP AND SHELL. THE APPLICATION OF ATMOSPHERIC PRESSURE UPON VENTING THE EVACUATION CHAMBER CAUSES THE TOP TO STRETCH INWARDLY AGAINST THE PRODUCT.

Description

Oct. 3, 1972 w. E. YOUNG ETAL EVACUATED HERMETICALLY SEALED PACKAGE WITH SEMIRIG SHELL AND STRETCHABLE CLOSURE Griginal Filed Sept. 1, 1965 2 Sheets-Sheet l mm Qw INVENTORS WILL/AM E. YOU/V6 R510 A. MAHAFFY BY A 51am. mm, m

ATTORNEYS Oct. 3, 1972 w YQUNG ETAL EVACUATED HERMETICALLY SEALED PACKAGE WITH SEMIRIGID SHELL AND STRETCHABLE CLOSURE Original Filed Sept. 1. 1965 2 Sheets-Sheet I nited States Patent ()lice 3,695,900 Patented Oct. 3, 1972 EVACUATED HERMETICALLY SEALED PACKAGE WITH SEMIRIGID SHELL AND STRETCHABLE CLOSURE William E. Young, Stamford, Conn., and Reid A. Mahafiy, Montclair, N.J., assiguors to Reid A. Mahatiy, John R. Harder, and American Can Company, fractional part interest to each Continuation of application Ser. No. 484,249, Sept. 1, 1965. This application July 22, 1970, Ser. No. 64,034

Int. Cl. 1365b 25/06, 31/02 US. Cl. 99-174 19 Claims ABSTRACT OF THE DISCLOSURE Evacuated hermetically sealed package comprising a top of stretchable plastic film sealed to a semi-rigid shell containing a product with the stretchable top in tight contact with the upper surface of the product. The package is formed by apparatus including a packaging head having preliminary and final sealing means. The preliminary sealing means include heat seal bars extending part way around the periphery of the shell and a heating element mounted within the space interiorly of the seal bars which softens the top and renders it readily stretchable in the area inboard of the seal line. Final seal means including an evacuating chamber and means to complete the seal between the top and shell. The application of atmospheric pressure upon venting the evacuation chamber causes the top to stretch inwardly against the product.

This application is a continuation of Ser. No. 484,249 filed on Sept. 1, 1965 and now abandoned.

This invention relates to packaging food products and the like in hermetically-sealed containers. More particularly, this invention relates to improved automatic packaging apparatus, packaging methods, and the packages made thereby.

Reference is made to copending application Ser. No. 64,035, filed by R. A. Mahatfy et al. on July 22, 1970, showing the basic subject matter of the present application (and including disclosure of additional material). To clarify the relationship between these two applications, it is noted that the present application is directed to the broad packaging concepts wherein a semi-rigid evacuated package comprising a cup-like receptacle or container is provided with a stretch-formed top arranged to reduce the transmittal of distorting stresses from the top to the container cup. Such package may be formed with a sequenced pressure application wherein pressure first is applied to the top and thereafter to the semi-rigid bottom. The top may be stretched subsequent to package evacuation, as by evacuation chamber, or the top may be pre-stretched prior to assembly and completion of the package, as by application of difierential pressure prior to the evacuation phase of the packaging operation. The copending application Ser. No. 64,035, on the other hand, is directed to specific features including (a) a trapezoidal-like package configuration, (b) the use of a stifi protective member as a third package element, (c) the technique wherein the top is stretched by first moving it away from the semirigid container (and the product contained therein) to a region adjacent a heater, and. thereafter forcing the top towards the container to stretch it, and (d) the use of a check valve to obtain the sequenced pressure-application technique more broadly claimed in the present application.

For a number of years now, extensive use has been made of automatic apparatus for packaging products in evacuated containers formed of flexible plastic packaging material. In some cases, the products were inserted in pre-formed pouches which were then evacuated and sealed along the opening. Subsequently (see, for example, US. Patent 3,061,984), completely automatic machines were developed to form packages from two sheets of flexible plastic film drawn from respective supply rolls. In either case, the resulting container was formed entirely of thin flexible film. Thus the ultimate evacuation of the container caused the film to be forced inwardly by atmospheric pressure into close and intimate pressure-contact with the enclosed product, and distorting the film into a shape conforming to the product profile.

For many products, such as luncheon meat and frankfurters, this approach provided reasonably accetpable results. However, it was not really satisfactory for certain other types of products. For example, when packaging a shingled group of bacon slices it has been found that the pressure applied by the atmosphere through the film to all parts of the bacon tends to cause undesirable cohesion of the individual strips of bacon after the container is opened by the purchaser. Also, the resulting container does not afford prospective customers the best presentation of the bacon through the stretched and distorted parts of the film.

Accordingly, it is one object of this invention to provide an evacuated package which is superior to those available heretofore. Another object of this invention is to provide improved vacuum packaging apparatus and methods. Still another object of this invention is to provide novel techniques for packaging certain specialty products such as bacon. Other objects, aspects and advantages of this invention will in part be pointed out in, and in part apparent from, the following description considered together with the accompanying drawings, in which:

FIG. 1 is a longitudinal vertical section through a part of the packaging machine;

FIG. 2 is a detail horizontal section (from below), showing the preliminary sealing means of the packaging head;

FIG. 3 is a perspective view of a completed package;

FIG. 4 is a cross-section taken along line 4-4 of FIG. 3;

FIG. 5 is a detail view, greatly magnified, of one corner of FIG. 4.

Referring now to FIG. 1, the packaging apparatus comprises a series of trays .10 each adapted to receive and snugly support a corresponding cup-like receptacle 12 carrying the product 14, in this case a one pound shingled group of bacon slices. These trays are power-driven from right to left with an intermittent cyclical indexing move- 0 ment to permit certain sequential packaging operations to be performed at respective stations along the path of movement.

Receptacles 12 are made of transparent, calendered, non-plasticized polyvinyl chloride, advantageously having a thickness in the range of five to fifteen mils. Such polyvinyl chloride is semi-rigid, meaning that is is self-supporting and substantially retains its shape under normal conditions of use, e.g. with a normal product load such as might be simulated by filling the receptacle with water. The receptacles are in the shape of a truncated triangular prism, best illustrated in FIG. 3, and having a cross-section in the form of an isosceles trapezoid as shown in FIG. 4. The receptacles are formed with flat peripheral flanges 16 extending entirely around the opening, and lying in a common plane.

Above two adjacent positions of the trays is a packaging head generally indicated at 18 and mounted (by conventional means, not shown) for vertical reciprocating movement in synchronism with the indexing of the trays. That is, when the trays stop, head 18 moves down to carry out certain operations to be described, and then rises just before the next indexing movement, so as to permit the trays to be shifted horizontally without interference.

To the right of packaging head 18, a web of flexible plastic packaging film 20 descends vertically to a lay down roll 21. This roll aids in applying the film to the top of the trays 10 as they are shifted into the first position under the packaging head 18. The film is drawn from a supply roll (not shown) and has a width suflicient to cover the receptacles 12 including the side flanges thereof. In the disclosed embodiment, film 20 is a laminate of Sarancoated polyester and polyvinyl chloride, and the polyvinyl chloride side faces down to engage the polyvinyl chloride receptacles '12. Thus the heat-sealing properties of the film 20 are compatible with those of the receptacles and both provide a good oxygen barrier.

The packaging head 18 includes both a preliminary seal means, generally indicated at 22, and an evacuation and final seal means, generally indicated at 2-4. The preliminary seal means further comprises peripheral heat-sealing bars 26 (see FIG. 2) arranged to extend around three flanges of the receptacle r12 and partially along the fourth flange. The gap in the heat-sealing bar along the fourth flange is filled with a low thermal conductivity, heat-resistant elastomer 28, e.g. silicone rubber, the lower edge of which is in the same plane as the heat sealing bars, or projects slightly below. Thus, when the head 18 descends, it presses the film 20 tightly against all of the flanges 16, sealing the film against air leakage around the entire periphery of the preliminary sealing means.

Also carried by the packaging head 18, within the preliminary seal means 22, is a flat platen 30 the lower surface of which is about /s" above the plane of the heatsealing bars 26. The side edges of this platen are spaced a small distance from the interior side walls of the heatsealing bars. This platen is formed to receive a set of heater elements 32, additional to the sealing heaters 33,

to maintain the platen at a moderately elevated temperature.

When the packaging head 18 is in its lower position, the chamber defined by the preliminary sealing means 22 is evacuated by a vacuum line 36. As shown in FIG. 1, this causes the film 20 to be forced uniformly up against the platen 30 so that the film becomes somewhat softened by the heat. Such softening makes it readily possible, by application of reasonable pressure, to stretch the film, e.g. beyond its elastic limit, for purposes as will be described subsequently.

While the receptacle 12 is in the preliminary seal position, the heated bars 26 operate in known manner to heat-seal the film 20 to the corresponding receptacle 12 along three of the flanges 16. Since the elastomer 28 is not heated, that end of the receptacle is not sealed to the film.

The head 18 thereafter rises and the partially sealed receptacle 12 is indexed to the next position where the evacuation and final sealing of the package take place. To this end, each tray 10 is provided with a captive weblifter 38 which, in accordance with prior art techniques,

is shifted up (through a previously formed cut-out 12a in the receptacle 12) to raise the end of the film 20 opposite the unsealed flange of the receptacle. The package then is evacuated through the channel thus created between the film and the receptacle. The vacuum is drawn through the web-lifter passage in the tray, through a vertically reciprocable gasketed coupler 40, a line 42 including a check valve 44 and the main vacuum valve 46 to which is connected a vacuum conduit 48. This main valve 46 also connects vacuum through a line 50 to the chamber above the film 20.

After evacuation, main valve 46 is shut off and an inert gas is admitted into the package from a gas line 52. The gas passes through an internal conduit in the web-lifter support, and exits into the package through an aperture in the top of the web-lifter. When the proper amount of gas has been admitted, the web-lifter is allowed to drop back down to its normal rest position and they usual heated final seal bar descends from above the film 20 to complete the heat-sealing of the film to the receptacle 12. This final seal extends along the side of the receptacle interiorly of the aperture 12a, and overlaps the preliminary seal lines so as to make the package completely gas-proof.

Thereafter, main valve 46 is shifted to its vent positon, admitting atmospheric air through line 50 into the final seal chamber above the film 20. The check valve 44 momentarily restrains the flow of air into the trays 10, but the air pressure above and below the package equalizes fairly quickly because some air will flow downward into the web-lifter passage which is imperfectly closed off by the final seal bar in its lowered position. In some cases, it may be desirable to speed up this pressure equalization by providing an adjustable-restriction by-pass valve around the check valve 44.

Although the foregoing description applies particularly to packaging machines of the type where evacuation is effected at one end of the package, this invention also is applicable to machines of the center evacuation type as illustrated in US. Pat. 3,061,984. For such center evacuation machines, two assemblies as illustrated in FIG. 2 are used in a side-by-side relationship with the elastomers 28 adjacent each other. The operation is identical, except that during venting to amtopshere no air will pass from the final seal chamber to the Web-lifter passage since there is no exposed edge of the film around which it can pass. Hence the air that is admitted to the final seal chamber is somewhat more effective in forming the film downward into the trays 12. It also may particularly be desirable to bleed air slowly through a bypass valve around check valve 44 so that the coupler 40 will not adhere to the tray.

The inrush of atmospheric pressure above the film 20 serves to force this film down into the receptacle 12, causing the film to be stretched. The extent of stretching depends upon how much gas had previously been admitted into the package. Preferably, the admission of gas is adjusted to that amount which results in the edges of the bacon being pressed lightly against the interior surface of the receptacle 12 when the package is in its normal upright position as shown in FIG. 3.

The stretching of the fihn 20 interiorly of the flanges 16 is aided by the heat applied in the preceding preliminary seal operation. Thus the film is somewhat softened so that it can be stretched, advantageously to an amount resulting in a permanent set of the plastic material. In any event, the film is force-fitted and stretched by the atmospheric pressure around all of the contours of the exposed pieces of bacon. The receptacle 12, being made of semirigid material, is not so formed about the bacon but instead contacts the edges of the bacon with the desired pressure engagement sufficient to assure that the bacon is immobilized within the package. This arrangement particularly is advantageous because shifting of the bacon can smear grease on the interior of the receptacle and interfere with a prospective customers inspection of the prodnet.

The pressure of the product against the interior of the receptacle 12 should be suttficient to press any large flat product surfaces, such as that of the end slice 14a, into full contact with the interior of the receptacle. However, the pressure desirably is low enough to avoid squashing the bacon edges 14b fiat against that interior. This degree of pressure provides a superior package appearance while preventing shifting of the product, disarray and grease smearing.

The film 20 can be vacuum-formed, i.e. stretched beyond its elastic limit, while in the preliminary sealing stage, for example to such an extent that no further stretching is needed in the final seal stage. Such stretching may be useful in some applications, and is facilitated by the effective air-tight seal around all four sides at the preliminary seal means, as well as by the heat transferred to the film by the platen 30. When forming the film in the preliminary sealing position, the platen 30 advantageously is placed more than Vs" above the plane of the heat sealing bars 26, e.g. at a distance approximately equal to the extent of forming desired. For some applications, the need for pre-heating and/or pre-stretching the film may be reduced or even avoided, as by the use of film material having suitable characteristics of stretchability at normal ambient operating temperatures.

In the final seal stage, physical stretching of the interior marginal portions of the film 20 inwardly to the product 14, especially to a permanent set dimension, is desirable because it tends to eliminate any substantial buildup of tension in the film. As shown in FIG. 5, the film is formed inwardly at 20a to follow the side wall contour of the receptacle 12. Thus the force of the atmospheric pressure is carried essentially by the packaged product, aided by the internal gas pressure. This avoids placing portions of the package under heavy stress, and minimizes distortion of the semi-rigid receptacle from its original shape.

Although a preefrred embodiment of the invention has been set forth in detail, it is desired to emphasize that this is not intended to be exhaustive or necessarily limitative; on the contrary, the showing herein for the purpose of illustrating the invention and thus to enable others skilled in the art to adapt the invention in such ways as meet the requirements of particular applications, it being understood that various modifications may be made without departing from the scope of the invention as limited by the prior art.

We claim:

1. A composite evacuated package comprising a relatively thick semi-rigid cup-like shell member of gasimpermeable material, said shell member having a base portion and side wall portions defining boundaries of an opening into said shell member, said shell member further including flanges around said opening; a product in said package, said product being no more than slightly smaller in lateral dimensions than said opening so as to provide a relatively close fit; a closure member of stretchable and gas-impermeable plastic sheet extending across said opening and heat-sealed to said shell member flanges, said closure member having a central face region which is at least approximately planar and generally parallel to said opening, said central face region being forced against the adjacent surfaces of the packaged product by atmospheric pressure so as to press said product against said shell base portion, said closure member further being formed adjacent said flanges with stretched portions extending down into said shell between said side wall portions and the closely adjacent side edges of the packaged product to the extent permitted by lateral space between said product and said shell, any portions of said stretched elements within such lateral space being forced by atmospheric pressure inwardly against the side edges of said product and outwardly against said side wall portions of said shell member.

2. A composite evacuated and hermetically sealed package comprising a relatively thick semi-rigid cup-like shell member of gas-impermeable material, said shell member having a base portion and side wall portions defining boundaries of an opening into said shell member, said shell member further including flanges around said opening; a product in said package, said product having lateral dimensions providing a close fit within the side walls of said shell member; the upper surfaces of said product being vertically displaced from said shell member flanges at least at a portion of the product adjacent the side wall of said shell member; a closure member of gasimpermeable plastic sheet extending across said opening and heat-sealed to said shell member flanges, said closure member having a central face region which is generally parallel to said opening, said central face region being forced against the adjacent surfaces of the packaged product by atmospheric pressure so as to hold said product tightly in position pressed against said shell base portion, said closure member further being formed adjacent said flanges with stretched elements extending away from said shell flanges to said upper surfaces of said product portion adjacent said side wall region, said elements being stretched to an extent avoiding the development of distorting tensions applied to said semi-rigid shell member from atmospheric pressure so that the atmospheric pressure load is carried by the packaged product; said stretched elements being forced by atmospheric pressure tightly against said product portion adjacent said side wall region and outwardly against any side wall portion of said shell member lying between said product portion upper surface and the adjacent flange, whereby the volume of the evacuated semi-rigid container adjusts to the size of the product so as to obtain the mechanical protection of a semi-rigid shell member while substantially eliminating voids within the evacuated interior.

3. A package as claimed in claim 2, wherein said elements are stretched beyond the elastic limit of said plastic sheet material.

4. The method of forming an hermetically-sealed package comprising the steps of securing a stretchable plastic sheet top over the opening of a semi-rigid cup containing a product to be packaged; evacuating the interior of the resulting package while providing a reduced pressure in the spaces above the package top and beneath the package cup; hermetically sealing the package; venting the space above the package top to provide a forceful pressing of the top down against the packaged product; and thereafter venting the space beneath the package cup.

5. The method of forming an hermetically-sealed package comprising the steps of placing in a semi-rigid cup having horizontal flanges around the opening a product the upper surfaces of which are below said flanges at least in the regions adjacent the side walls of the cup; sealing a plastic sheet top to said flanges at least substantially around said opening; evacuating the interior of the package while providing a reduced pressure in the spaces above the package top and beneath the package cup; hermetically sealing the package, venting the space above the package top to provide a forceful pressing of the plastic sheet top down against the packaged product; and thereafter venting the space beneath the package cup.

6. The method of making an evacuated and hermetically sealed package by means of an automatic packaging machine carrying out the process steps of:

supporting a semi-rigid tray-like shell member of relatively thick, gas-impermeable packaging material having a bottom portion with upstanding wall portions defining boundaries of an opening into said shell member and being provided with flanges around said opening, said shell member containing a product having lateral dimensions substantially the same as said opening so as to provide a close fit within said upstanding wall portions, the upper surfaces of said product being vertically displaced from said flanges, at least at the portions of said product adjacent the side wall of said shell member;

advancing said shell member through a series of positions;

advancing through a series of positions a sheet of heatstretchable and gas-impermeable plastic packaging material which at one stage of the package-making process is disposed over the opening of the shell member and is sealed thereto around a peripheral region;

heating said plastic sheet in one of said positions thereof to soften the marginal portions of said sheet inboard of said peripheral region sufliciently to permit stretching of said marginal portions;

stretching said heated marginal portions of said plastic sheet to create a central face portion and stretched side portions adapted to extend away from said shell member flanges at least to the level of the upper surfaces of said product portions which lie next to said shell member wall portions;

evacuating said shell member while said platic sheet is disposed thereover;

applying heat to said packaging material while said shell member is evacuated with said sheet disposed thereover, said heat being applied so as to effect a permanent heat-seal to form said shell member and said sheet into a gas-tight package the internal pressure of which is less than atmospheric; and exposing the exterior of the package to atmospheric pressure with said package sufliciently evacuated that the external atmospheric pressure forces said central face portion tightly against the upper surfaces of the packaged product and presses said stretched side portions tightly against all immediately adjacent surfaces of said shell and said product, the stretching of said side portions being sufi'icient to prevent the atmospheric pressure from developing tensional stresses therein tending to distort the shell member.

7. The method of making an evacuated and hermetically sealed package by an automatic packaging machine carrying out the process steps of:

supporting a semi-rigid tray-like shell member of relatively thick, gas-impermeable packaging material having a bottom portion with upstanding wall portions defining boundaries of an opening into said shell member and being provided with flanges around said opening, said shell member containing a product having lateral dimensions substantially equal to said opening so as to provide a close fit within said upstanding wall portions; the upper surfaces of said product being below said flanges adjacent the side wall of said shell member;

advancing said shell member through a series of positions;

advancing through a series of positions a sheet of heat-stretchable and gas-impermeable plastic packaging material which at one stage of the packagemaking process is disposed over the opening of the shell member and is sealed thereto around a peripheral region;

heating said plastic sheet at one of said positions thereof to soften the marginal portions of said sheet inboard of said peripheral region suificiently to permit substantial stretching of said marginal portions;

reducing the pressure in said chamber;

evacuating the interior of said shell member while in i said chamber;

applying heat to said packaging material while in said chamber to effect a permanent heat-seal to form a gas-tight hermetically-sealed package the internal pressure of which is substantially less than atmospheric; and '1 venting said chamber to apply substantially increased pressure to the outside surfaces of the hermetically sealed and evacuated package structure suflicient to stretch said heated marginal portions of said plastic sheet down towards the packaged product, the applied pressure forcing the central portion of the plastic sheet interiorly of said stretched portions against the upper surfaces of the packaged product, the applied pressure further forcing the stretched marginal portions outwardly against the adjacent wall portions of the semi-rigid shell member to eifectively eliminate voids in the package, the stretching of said marginal portions being sufficient to prevent the atmospheric pressure force on said plastic sheet from developing tensional stresses therein tending to distort the shell member.

8. Apparatus for making packages comprising, in combination, a series of receiving elements adapted to be mounted in an endless loop arranged for movement past a series of packaging stations where sequential packaging operations are performed, said elements including means to support respective cup-like members of semi-rigid material adapted to receive products to be packaged; means to apply to said elements a film of flexible packaging material over the opening of each cup-like member in sequence; a packaging head at one of said stations and including means operable to seal said film to the respective cup-like member in a region extending around the periphery thereof; heating means within said packaging head to raise the temperature of said film interiorly of said sealed region; and evacuating means to withdraw air from the package to the extent that atmospheric pressure forces said heated flexible film inwardly against the product by stretching said film interiorly of said sealed region.

9. Apparatus for making packages comprising, in combination, a series of receiving elements adapted to be mounted in an endless loop arranged for movement past a series of packaging stations where sequential packaging operations are performed, said elements including means to support respective cup-like members of semi-rigid material adapted to receive products to be packaged; means to apply to said elements a film of flexible packaging material over the opening of each cup-like member in sequence; a packaging head at one of said stations and including means operable to seal said film to the respective cup-like member in a region extending around the periphery thereof; support means to engage the bottom surfaces of the cup-like member at said one station; first vacuum means at said one station to withdraw air from the package and to reduce the pressure on the outside surface of said semi-rigid member during evacuation of the package; second vacuum means at said one station to reduce the pressure on the outside surface of said film during said evacuation; and control means for venting said second vacuum means to atmosphere, said control means including means automatically operable upon vent-' ing of said second means to retain reduced pressure on the outside surface of said semi-rigid member for a short period of time and thereafter to cause that pressure to equal the atmospheric pressure on said film, the atmospheric pressure during said short period of time forcing said flexible film downwardly against the product to stretch said film interiorly of said sealed region, the bottom surfaces of the cup-like member being supported by said support means against the downward pressure of atmosphere during said short period of time.

10. Apparatus for making packages comprising, in combination, a series of receiving elements adapted to be mounted in an endless loop arranged for movement past a series of packaging stations where sequential packaging operations are performed, said elements including means to support respective cup-like members of semi-rigid material'adapted to receive products to be packaged; means to apply -to said elements a film of flexible packaging material over the openingof each cup-like member in sequence; a packaging head at one of said stations and including preliminary sealing means and final sealing means, said preliminary sealing means including heated seal bars extending part way around the periphery of each member to seal said film to the respective cup-like member while leaving an opening at one region for subsequent evacuation of the package; a heating element mounted in said packaging head within the space interiorly of said seal bars and arranged to raise the temperature of said film interiorly of said sealed region; and

evacuating means at said final sealing means to withdraw air from the package such that atmospheric pressure forces said heated flexible film inwardly against the product by stretching said film interiorly of said sealed reglop.

11. Apparatus as claimed in claim 10, wherein said heating element comprises a platen disposed parallel to the surface of the film.

12. Apparatus as claimed in claim 11, including an unheated member bridging the gap between the ends of said seal bars at said region, and vacuum means for evacuating the spaces around said heating element to draw said film into contact therewith.

13. Apparatus for making packages comprising, in combination, a series of receiving elements adapted to be mounted in an endless loop arranged for movement past a series of packaging stations where sequential packaging operations are performed, said elements including means to suport respective cup-like members of semi-rigid material adapted to contain products to be packaged; means to apply to said elements a sheet of stretchable plastic packaging material with the sheet being positioned over the opening of each cupJike member in sequence to form a package structure; a packaging head at one of said stations and including means operable to seal said sheet to the respective cup-like member in a region extending around the periphery thereof; heating means within said packaging heard arranged to raise the temperature of said plastic sheet interiorly of said peripheral sealed region, said heating means comprising a heated element positioned closely adjacent said plastic sheet to transfer heat thereto interiorly of said sealed region; and evacuating means to withdraw air from the package to such an extent that atmospheric pressure forces said heated plastic sheet inwartily against the product by stretching said sheet interiorly of said sealed region.

14. Apparatus for making evacuated packages of semin'gid type and comprising, in combination, a series of receiving elements mounted in an endless loop for movemerit past a series of packaging stations where sequential packaging operations are performed, said receiving elemerits including means to support respective cup-like members of semi-rigid material adapted to contain products to be packaged; means to apply to said elements a continuous sheet of stretchable plastic packaging material with the sheet positioned over the periphery of the opening of each cup-like member in sequence to form a corresponding package structure; relatively reciprocable packaging head means adjacent the path of movement of said receiving elements; said packaging head means comprising means to evacuate and hermetically seal said package structure, including means operable to seal said sheet to the respective cup-like member throughout a region extending around the periphery of the opening thereof; said packaging head means also including heating means to raise the temperature of said plastic sheet interiorly of said peripheral sealing region and comprising a heated element positioned closely adjacent the plastic sheet to transfer heat thereto; said packaging head means further including means to create a pressure differential across the heated areas of said plastic sheet to stretch the marginal sheet portions inboard of said peripheral sealing region in a direction generally perpendicular to the surface of the plastic sheet, said stretched portions being held by atmospheric pressure in a position extending into said cup-like member and pressed against the side walls thereof after the evacuated and sealed package has been completed.

15. Apparatus for making evacuated packages of semirigid type and comprising, in combination, a series of receiving elements mounted for movement past a series of packaging stations Where sequential packaging operations are performed, said receiving elements including means to support respective cup-like members of semirigid material adapted to contain products to be packaged; means to apply to said elements a. continuous sheet of stretchable plastic packaging material with the sheet positioned over the periphery of the opening of each cuplike member in sequence to form a corresponding package structure; heating means to raise the temperature of said plastic sheet comprising a heated element positioned closely adjacent the plastic sheet to transfer heat thereto; means to create a pressure differential across the heated areas of said plastic sheet to stretch the marginal sheet portions thereof in a direction generally perpendicular to the surface of the plastic sheet, relatively reciprocable packaging head means adjacent the path of movement of said receiving elements; said packaging head means comprising means to evacuate and hermetically seal each package structure, said stretched portions being held by atmospheric pressure in a position extending into said cup-like member and pressed against the side walls thereof after the evacuated and sealed package has been completed.

16. Apparatus for making evacuated packages of semirigid type wherein the upper surfaces of the product are displaced vertically with respect to the opening of the container, at least in the portions of the product adjacent the edges of the opening, said apparatus comprising, in combination, a plurality of receiving elements mounted for movement past a series of packaging stations where sequential packaging operations are performed, said receiving elements including means to support semi-rigid material formed into cup-like container members adapted to contain products to be packaged; means to advance towards said elements a continuous sheet of plastic packaging material with the sheet positioned over the opening of each cup-like member in sequence to form therewith a corresponding package structure; package forming means adjacent the path of movement of said receiving elements and comprising heating means and means to evacuate the package structures; said heating means including means operable to hermetically seal each package structure including means to seal said sheet to the respective cup-like member throughout a region extending around the periphery of the cup opening; said heating means further including means to transfer heat to the marginal portions of said plastic sheet immediately inboard of said peripheral sealing region to raise the temperature of said marginal portions to a level sufficient for stretching thereof by application of pressure; said pack age forming means also including means to create a pressure differential across said plastic sheet to stretch said marginal sheet portions in a direction generally perpendicular to the surface of the plastic sheet to develop stretched marginal portions which in the completed package are held by atmospheric pressure pressed against all immediately adjacent surfaces of the contained product and the cuplike member.

17. Apparatus as claimed in claim 16, wherein said means to evacuate said package structure comprises a relatively movable member at one packaging station arranged when actuated to form an evacuation chamber; said receiving elements being arranged to transfer said package structures into position to 'be held within said chamber; said means for heating said marginal portions of said plastic sheet being located at a packaging station preceding said one packaging station.

1-1 12 18. Apparatus as claimed in claim 17, wherein said 3,226,236 12/ 1965 Weller 99 171 means for creating a pressure differential is at a packaging 3,298,158 1/ 1967 Schmidt -3 53-l 12 station preceding said one packaging station. 3,347,011 10/ 1967 Lovas et a1. 3.- 53- -21 19. Apparatus as claimed in claim 17, wherein said 3,467,244 9/ 1969 Mahalfy'et a1; L- 20645.34" means for creating a pressure differential comprises means 5 3,522,687 8/ 1970 Mahaffy 53 22 to vent said vacuum chamber after the package has been I 1 evacuated and hermetically sealed by said package MORRIS Pflmary Examlnel forming means. B D A I References Cited S. v V S, Assistant Examiner UNITED STATES PATENTS -SQ J. A .7 2,834,686 5/1958 Reuman 99-171 53--22 A, 30,39, 42,-112 A, 141, 184; 99- 17,1-LM,

3,034,271 5/1962 Carpenter et al 53-184 TC, 171 LP; 206-46 F UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,695,900 Dated October 3 1972 Invent fl William E. Younq. et. al

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 69, insert placing said shell member with said plastic sheet disposed thereover in a sealed chamber;

Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I 7 ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM PO-1050 (10-69) USCOMM-DC 6O376-P us. GOVERNMENT PRINTING OFFICE: 1959 03ss-3:u

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