US2991600A - Method and apparatus for vacuum packaging with plastic sheaths - Google Patents

Description

July 11, 1961 T. A. LANCASTER METHOD AND APPARATUS FOR VACUUM PACKAGING WITH PLASTIC SHEATHS Filed Aug. 26, 1957 2 Sheets-Sheet 1 INVENTOR FMBOTAA/Wc/IsTE)? BY A 27 1 Z5 20 A TOR EY July 11, 1961 "r. A. LANCASTER 2,991,600

METHOD AND APPARATUS FOR VACUUM PACKAGING WITH PLASTIC SHEATHS Filed Aug. 26, 1957 2 Sheets-Sheet 2 INVENTOR 7 3 /-7- Lfl/VCHSTEP 2,991,600 METHOD AND APPARATUS FOR VACUUM PACKAGING WITH PLASTIC SHEATHS Talbot A. Lancaster, Canterbury, Conn. Filed Aug. 26, 1957, Ser. No. 680,136 6 Claims. (Cl. 53-22) This invention relates to the art of vacuum sealed packages, and more especially it relates to packaging With thin plastic sheets or films.

A principal object of the invention is to provide a novel method and apparatus for wrapping articles with plastic sheet or film material so that the wrapper closely fits or sheathes substantially the entire contour of the article.

Another object is to provide a method and apparatus for applying to any shaped article a skin-tight covering or sheath of plastic sheet or film material.

Another object relates to a vacuum wrapped article of regular or irregular shape which is provided with a skintight vacuum-sealed wrapping of thermoplastic material.

Various kinds of vacuum wrappings have been devised for wrapping food products or other irregularly shaped articles in plastic coverings. Thus one known method requires the preparation of the wrapper as a bag or pouch, into which the article is inserted through the open end of the pouch. If a vacuum wrapping is required, a suction tube is inserted into the open end of the pouch prior to scaling that open end, after which the pouch is sealed and the exhaust tube withdrawn. In such cases it is usually necessary to make the pouch oversize with respect to the article to be wrapped, and after the evacuation the pouch is subjected to a temperature high enough to cause the wrapping material to shrink onto the article. Such a method is wasteful of the wrapping material and it requires the storing of a large number of various shapes and sizes of pouches, depending upon the shape and size of the article to be wrapped.

In an effort to reduce the wastage of wrapping material, it has been proposed to make the wrapping pouch undersize with respect to the article which, however, requires stretching of the pouch and the forcing of the article therein. Reliance must then be placed upon the elasticity of the pouch material to cause it to conform to the wrapped article. However, such a method still requires the pre-formation of pouches of different sizes and shapes to suit different kinds and shapes of articles. Furthermore, while the known methods are, capable of being practiced by manual operations, it is somewhat diflicult to adapt them to continuous or automatic ma chine wrapping operations. Furthermore, while it is somewhat easy with conventional methods to wrap simple and regularly shaped fiat articles, such as meat slices and the like, it is diificult and wasteful of wrapping material and time to wrap complex shaped articles such as fowl, irregularly shaped vegetables, and the like.

In accordance with the present invention, the abovenoted and other disadvantages are overcome by devising a process wherein the wrapping envelope is formed in situ during the wrapping operation, requiring merely flat sheets of thermoplastic material. As a result of the inventive method there is produced a plastic wrapped package wherein the plastic wrapping material is closely molded to conform itself to practically all the contours of the article or item being packaged. Accordingly one of the features of this invention relates to a method of forming a vacuum sealed plastic wrapping for any shape of article, and one which renders it feasible to use automatic wrapping machines for the continuous automatic vacuum wrapping of a wide variety of oddly shaped articles, to provide such articles with a skin-tight plastic evacuated sealed wrap.

United States Patent() Other features and advantages not specifically enumer- Matte Patented July 11, 1961 ice tain preferred forms of the invention,

FIG. 1 is a perspective view of a device or apparatus according to the invention and illustrating one step in the method of the invention;

FIG. 2 is a view similar to that of FIG. 1, illustrating another step in the method;

FIG. 3 is a sectional view of FIG. 2, taken along the line 33 thereof, and illustrating a further step in the method;

FIG. 4 is a sectional view of FIG. 1, showing the parts in closed or clamped position, illustrating a further step in the method;

FIG. 5 is a view similar to that of FIG. 4, illustrating the final sealing step;

FIG. 6 is a sectional view of the final vacuum sealed packaged article;

FIG. 7 is a sectional view explanatory of a modification of the invention.

Referring to FIG. 1, a preferred form of device for practicing the invention includes a pair of swingably attached metal frames 10, 11. Merely by way of illustra tion, the frames are shown as of rectangular shape, although any other shape can be employed. The two frames are identical in shape and are of hollow tubular sheet metal construction. Frame 10 has attached there- -to a pair of flat metal extension plates 12, 13, each of which carries a pivot pin 14, 15 for pivotal movement of the frame in respective blocks 16, 17. The said blocks are in slidable engagement with a pair of upright rods 18, 19 which can be anchored to a suitable base 20 (FIG. 3). Similarly, frame 11 carries a pair of extensions 21, 22 and respective pivot pins pivoted in respective blocks 23, 24, which blocks are also slidably supported on the uprights 18, 19. As shown in FIGS. 4 and 5, the frames 10 and 11 can be moved to a closed or parallel spaced position, or to the open position as shown in FIGS. 1 to 3, and in the dotted line position in FIG. 5. The particular manner of swingably mounting the frames as described, enables them to be moved to parallel closed spaced positions, while allowing the frames to be spaced apart a distance D (FIGS. 4 and 5). Merely for explanatory purposes, it will be assumed that the article to be wrapped is an irregularly shaped meat product, such as chicken or fowl.

The opposing faces of frames 10 and 11 are provided with a series of small openings 25, 26. Attached to the perforated frame faces are respective soft gum rubber or sponge rubber rectangular gaskets 27, 28, each of which has a series of perforations 29, 30 in alignment with the respective frame perforations 25, 26. The gaskets 27, 28 may be of approximately one-quarter inch thickness. The rear side of each frame has an opening into which is sealed a respective flexible pipe 31, 32 leading to an evacuating pump 33 whereby each of the frames can be evacuated to any desired degree. Likewise another flexible pipe 34 is connected to a vacuum pump 35 which, if desired, may be the same pump that is connected to pipes 31, 32. However, the pipe 34 is not inserted between the frames until a subsequent stage in the method, as will be described hereinbelow. Normally frames 10 and 11 are in their open position, as shown in FIG. 1, and the pipes 31, 32 and 34 are shut off by suitable valves (not shown). When the frames are in their closed positions, as shown in FIGS. 4 and 5, the spacing D is such as to give proper clamping pressure on rubber gaskets 27, 28 to hold the plastic firmly and provide an air-tight seal between the opposing faces of the film within the clamped area and around the vacuum tube 34.

too far.

When it is desired to wrap an article such as a chicken 36, the valves for pipes 31, 32 are opened, thereby subjecting the frames to internal evacuation. Thereupon two fiat sheets or films 37, 38 of the wrapping material are then held adjacent the respective frames and as a result of the suction through the frame perforations and through the gasket perforations, those sheets are firmly held fiat against their respective frames by atmospheric pressure. I D v In accordance with the invention, the sheets 37, 38 are of a film-fonning thermoplastic. Typical of such plastics are those of vinyl, Saran, Pliofilm, cellulose acetate, cellulose acetate-butyrate, polystyrene, polyethylene, and the like. H

At this stage either or both of the sheets 37, .38 may be warmed by any suitable means to the softening temperature of the plastic as schematically represented by the blocks 50, 51 in FIG. 3. The article 36 to be wrapped is then placed in the center of the lower plastic film 38, as indicated in FIG. 3. As a result of the softening of the film 38 and the weight of the article, the said film tends to conform itself to the general contour of the lower half of the article. placed at a proper distance below the lower plastic film to prevent the weight of the article from stretching it At this stage the suction tube 34 is inserted between the films 37 and 38, as indicated in FIG. 3, and thereafter the frames are brought together in spaced parallelism, as indicated in FIG. 4. Preferably the frames are held together under suificient force, for example by a suitable clamp 39, so as to prevent air leakage. While the clamp is shown as of a screw type, any other well known clamping or closing device such as an air or hydraulic piston or a toggle clamp could be used. The valve or pipe 34 may then be opened so as to evacuate the entire space between the clamped margins of the two sheets 37 and 38.

Preferably the pipe 34 is of rigid construction so that the soft rubber gaskets 27 and 28 can conform themselves around the pipe so as to maintain an airtight seal for the evacuation of the space between the plastic sheets. As a result of the evacuation through the pipe 34, and as a result of the positive external air pressure on the outside of the films 37, 38, and since these films are in a softened or plastic state, they mold themselves permanently and in a sheath-like contact around the contours of the article 36, as indicated in FIG. 5.

After the desired amount of air has been removed from the space between the sheets 37 and 38, and the skin-tight fit around the article has been effected, the suction tube 34 can be withdrawn and the two films can be heat sealed in the marginal area around the article. The heat sealing may be accomplished by the use of sufiicient over-all heat to bring the thermoplastic films to their sealing temperatures. Preferably, however, a supplementaryheat-sealing device 40 of any well known construction may be lowered into heat sealing relation with the marginal areas of the films 37, 38. If the sealing unit *40 is of the well known impulse sealer or bar type sealer, well known in the plastic sealing art, it should be smaller in outside dimensions than the inside dimensions of the frames so as to permit it to fit inside the frame and to be brought into close marginal sealing position with respect to the plastic films. Alternatively, the sealer may be built into the frames by means of a heating ribbon attached to the soft rubber gasket of one plate. In this instance it would be preferable to use a heat resistant rubber such as silicone and the sealing may be by either impulse or heated bar principle. It is common practice to construct heat sealers with the heat source on one side only, and the other side consisting of a silicone rubber resilient material. After the heat sealing around the margins of the article has been completed, the frames and 11 are opened and the complete vacuum sealed package is removed. 'If desired, the ex- A support may be cess film around the sealed area may be trimmed away to leave a relatively narrow thin or sealed margin 41 (FIG. 6) around the sealed package.

It will be understood that the invention is not necessarily limited to the heating of the plastic films 37, 38 prior to closing the frames 10 and 1 1. For example, after the said plastic films 37, 38 have been suctionally clamped against the opposed faces of the two frames, the frames may be moved to their closed parallel relation as shown in FIG. 4, and then the plastic films may be heated to their softening temperature while the volume of space between the two film's, as defined by the clamped margins of those films, can be subjected to the required suction. It will be understood, of course, that the said suction may be applied either before, during or after the application of the softening heat to the films 37 and 38. Thus the shrinkage of the film or films by heating rnay be effected after the final sealing, instead of prior to the final sealing, as above described. 7

Furthermore, while the method above described employs a suction clamping of the films 37 and 38 against the two clamping frames 10 and 11, it will be understood that any other well known manner of holding or clamping the said plastic films against the opposed clamping faces ofthe frame members can be employed. However, by using the suction method of clamping as above described, it is practical to insert and remove the suction tube 34 without difiiculty, while enabling the attaining of a leak-proof seal between the resilient faces of the frames. It will be understood that whereas the apparatus described uses hinged frames and mechanical clamping, this machine can be constructed using any well known method of closing and clamping, such as air or hydraulic cylinders, cam or gear action, and the like. Furthermore, instead of using individual or pre-cut sheets of plastic films, the thermoplastic may be fed to the machine from two rolls of film of the proper width and each individual package either cut from the strip of packaged articles or allowed to remain in a strip of two or more for multiple marketing, as desired.

It will be understood, furthermore, that the invention is not limited to the particular materials which have been mentioned for the various parts.

The invention can also be practiced using only one film of plastic material. For example the lower film 38 may be replaced by a paper or cardboard stock which has its surface coated with a material which is heat scalable to the upper plastic fihn 37, in the same manner as above described. Thus, as shown in FIG. 7, the upper plastic film 37 has been scaled to the surface of a cardboard plate-like support 42, the surface of which has been pre- -.Viously coated with a layer 43 of a material which readily 'seals to the plastic film 37, as above described. The embodiment of FIG. 7 is particularly desirable in packaging flimsy or soft materials, such as textiles or soft meats, for example liver and the like. In either embodimerit the final package is a vacuum sheath wrapped product which is hermetically sealed and, of course, the plastic 37 and the plastic 38 may be of clear transparent article of any regular or irregular peripheral surface contour, which comprises, fastening a pair of unperforated thermoplastic sheets which are free from preformed surface distortions each against a respective upper and lower windowed frame, resting the article on the 's'heet faster'fed to are lower frame, subjecting each sheet while on its frame to an initial softening heat, closing the frames to clamp the margins of the softened sheets completely around the article whereby the weight of the article causes the lower film to conform itself to the general contour of the article, evacuating the entire volume of space defined by the clamped margins and thereby to cause both of the softened sheets to collapse and completely conform themselves against the contour of the article, then subjecting the portions of the sheets in the region between their clamped margins and the article to a final heating to seal said sheets immediately adjacent the periphery of the article.

2. The method according to claim 1 in which both of said thermoplastic sheets are fastened to their respective frames by suction through the interior of the frames.

3. Apparatus for vacuum Wrapping and sealing an article of any regular or irregular peripheral surface contour, comprising, upper and lower normally spaced supporting frames of open windowed construction, means to fasten a pair of unperforated thermoplastic sheets against each of said frames each sheet completely bridging the open window of its respective frame, the sheet on the lower frame serving -as the support for the article during the wrapping and sealing thereof, means to subject each sheet while on its frame to an initial softening heat, means to clamp the frames together and with the article sandwiched between the opposing thermoplastic sheets whereby the weight of the article causes the lower sheet to gener-ally conform in its softened condition to the general contour of the lower half of the article, means to evacuate the entire volume of space defined by the clamped margins of the sheets while in heat softened condition and thereby to cause both of the softened sheets to collapse and completely conform themselves against the contour of the article, and means to subject the portions of the sheets in the region between their clamped margins and the article to a final heating to seal the sheets immediately adjacent the periphery of the article.

4. Apparatus according to claim 3 in which each of said frames is of tubular construction having openings in the walls thereof against which said sheets are held by suction through the interior of the respective frames.

5. Apparatus according to claim 3 in which anannular heat sealing unit is arranged to be inserted through the open windowed portion of at least one of said frames to effect the said final heating and sealing of said sheets.

6. Apparatus according to claim- 5 in which the said walls of said frames at the clamping margins are provided with resilient gaskets each of which has openings in alignment with the said openings in the frame walls whereby the sheets can be fastened against their respective frames by suction through the frames and gaskets.

References Cited in the file of this patent UNITED STATES PATENTS 1,387,805 Roberts Aug. 16, 1921 1,970,193 Riebel Aug. 14, 1934 2,155,445 Pittenger et al. Apr. 25, 1939 2,621,129 Ramsbottomet a1. Dec. 9, 1952 2,690,593 Abercrombie Oct. 5, 1954 2,730,281 Prohask-a Jan. 10, 1956 2,749,686 Lorenz et a1. June 12, 1956 2,750,719 Wandelt June 19, 1956 2,780,043 Hensgen Feb. 5, 1957 2,861,405 Hanford Nov. 25, 1958 OTHER REFERENCES Modern Packaging, March 1957, article beginning on page 154.

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