US3587839A - Package and method of packaging a product - Google Patents

Abstract

A PRODUCT PACKAGED BETWEEN TWO SOFT, HEAT SEALABLE SYNTHETIC, PLASTIC FILMS, ONE BEING STRETCHABLE AND ELASTIC AND THE OTHER BEING HEAT SHRINKABLE. THE FILMS ARE BROUGHT TOGETHER AND HEAT SEALED ALONG A LINE CIRCUMSCRIBING THE PRODUCT. THE HEAT SHRINKABLE FILM IS THEN HEAT SHRUNK SUFFICIENTLY TO DRAW BOTH FILMS TAUT OVER THE PRODUCT AND STRETCH THE STRETCHABLE FILM, THE STRETCHABLE FILM ACTING TO LIMIT THE STRESS ON THE HEAT SEALED SEAMS DURING HEAT SHRINKING AND TO THEREAFTER TAKE UP SLACK DUE TO RELAXATION OF THE HEAT SHRUNK FILM.

Description

United States Patent Forrest G. Von Brecht 6 Forest Ridge, Clayton, Mo. 63105;

Ryder Pratt, 515 Cresent Drive, Klrkwood, Mo. 6312 2 Feb. 20, 1969 June 28, 1971 Continuation-impart of application Ser. No. 665,010, Sept. 1, 1967, now abandoned.

Inventors Appl. No. Filed Patented PACKAGE AND METHOD OF PACKAGING A PRODUCT 8 Claims, 10 Drawing Figs.

U.S. Cl 206/46, 53/30, 99/171, 206/80, 229/87 Int. Cl ..Bb 53/00, B65d /28, B65d 85/70 Field of Search 206/46 (FOOD), 46 (MISC), 45.33, 56 (A2), (A), 65 (S), 63.2; 229/(S.C.), 87 (FOOD); 99/171; 53/22, 30

[56] References Cited UNlTED STATES PATENTS RE26,494 12/1968 Stoker, Jr. 206/80(A) 2,980,245 4/1961 Stoker, Jr. .206/45.33(UX) 3,010,262 11/1961 Rumsey, Jr. 206/45.33(UX) 3,024,579 3/1962 Stockhausen et al. 53/22 3,061,087 10/1962 Scrivens et a1 206/63.2 3,090,484 5/1963 Scholl 206/80(A) 3,126,680 3/1964 Baird,Jr. et al 229/(S.C.)

Primary ExaminerWilliam T. Dixson, Jr. Al!0rneyCharles E. Markham PACKAGE AND METHOD OF PACKAGING A PRODUCT This application is a continuation-in-part of our copending application Ser. No. 665,010 filed Sept. 1, 1967 and now abandoned. This invention relates to packages and to a method of forming packages of thin, soft, synthetic plastic film.

The packaging of products or the overwrapping of packaged products with soft, thin, synthetic, plastic shrink films by heat sealing seams and thereafter heat shrinking the film to form neat, smooth enclosures of pleasing appearance which remain neat and smooth through cold storage and handling presents certain problems. For example, the heat sealed seams are frequently subjected to local high stressing during heat shrinkage of the film. This may result in seam separation and in undesirable distortion of semirigid products particularly when using film of high heat shrink energy. Furthermore, the properties of shrink films are changed by heat shrinking, notably, a decrease in elasticity and the capacity to retain the tension developed during heat shrinkage increases with the amount of shrinkage. This frequently results in a slack, unattractive package which becomes worse upon handling or upon storage under low temperature conditions.

U.S. Pat. No. 3,010,262 issued Nov. 28, 1961 to H. Rumsey, Jr. discloses a package comprising a semirigid performed cup member formed from a sheet of heat sealable thermoplastic material impervious to air and rendered heat shrinkable by hot-stretching during forming of the cup member. The package further includes a fiat cover member comprising a sheet of thermoplastic material heat sealed to the rim of the cup member. This cover member is also impervious to air but is not hot-stretched or heat shrinkable. The package is evacuated as it is heat sealed thereby drawing the package into tight engagement with a product or contents therein. The evacuation of the package results in wrinkling of the semirigid cup member and the cup member is then heat shrunk to remove the wrinkles. The heat shrinkage of the cup member causes it to now smoothly embrace and tightly engage the package contents and also stretches or pulls the nonheat shrinkable cover member over the end of the package contents.

Rumsey has provided a' preformed semirigid package which is heat shrunk and relies apparently upon the rigidity of the package to preserve it's attractiveness. He does not, however, provide means to prevent the undue distortion of soft or semirigid products when employing soft shrink film wrap of high heat shrink energy nor does he provide any means to maintain a soft heat shrunk film taut.

According to one form of our invention a product is packaged by placing it between two thin, heat sealable, synthetic plastic films which are drawn together over the product and heat sealed along a line circumscribing the product. One of the films being relatively stretchable and elastic and the other being heat shrinkable and being heat shrunk sufficiently after heat sealing to draw both films taut over the product and substantially stretch the relatively stretchable elastic film. Both films are soft an limp so that both may freely move across the surfaces of the enclosed product as the heat shrinkable film is being heat shrunk and subsequently when the stretchable elastic film contracts to take up any relaxation of the shrink film or any deformation of either film due to handling of the package.

In another form of our invention a first soft, heat sealable, synthetic, plastic film is placed fiat on a platten and the product to be packaged is placed thereon. A second soft, thin, highly stretchable and elastic, heat sealable, synthetic plastic film is then substantially stretched over the upper surface and sides of the film and brought into contact with the first lower film where it is held with the lower film against the platten and I In yet another form of our invention the lower film in the arrangement described in the preceding paragraph is soft, heat shrinkable film and is heat shrunk after the upper stretchable, elastic film is stretched and heat sealed thereto whereby a lesser degree of stretching of the upper elastic film prior to heat scaling is required to draw both films taut and maintain a skin tight package.

An object of the present invention is to provide a package comprising two soft, thin, heat sealable synthetic plastic films, one on each side of the product packaged and being drawn together and heat sealed together along a line circumscribing the product, one of the films being relatively easily stretchable and elastic material and the other being heat shrinkable material and being heat shrunk after the films are heat sealed together thereby to pull both films taut over the product and stretch the stretchable film substantially, whereby the stress upon the heat sealed seams during heat shrinkage of the stretchable film is limited due to substantial stretching of the stretchable film and whereby subsequent slackening of the heat shrunk film or deformation of either film is taken up by contraction of the stretchable elastic film to maintain both films taut.

A further object is to provide a package as in the preceding paragraph in which one of the films is heat shrinkable and the other film is stretchable and elastic has negligible shrinkage when the heat required to adequately shrink the heat shrinkable film is applied to the entire package.

, A further object is to provide a package comprising two soft, heat sealable synthetic plastic films enclosing a product, one film covering the bottom surface of the product and the other film covering the top and side surfaces of the product and being heat sealed to the one film along a line circumscribing the product, the other film being stretchable and elastic and being stretched sufficiently over the top and side surfaces of the product prior to heat sealing to the one film to cause both films to be drawn taut.

A further object is to provide a method of packaging a product between two soft, thin films of synthetic plastic material in which the elasticity of one of the films is employed to draw both films taut over the product.

A further object is to provide a method of packaging a product between two soft, thin films of synthetic plastic material in which the elasticity of one film and the heat shrinkability of the other are jointly employed to draw and maintain both films taut over the product.

A further object is to provide a fiat bag comprising two soft, thin, films of heat sealable, synthetic plastic material heat sealed together along three sides, one of the films being heat shrinkable material and the other film being stretchable and elastic and having negligible shrinkage when heat is applied to the entire bag to shrink the heat shrinkable film.

Further objects and advantages will appear when reading the following description in connection with the accompany ing drawing. 1n the drawings:

FlGS. l, 2 and 3 diagrammatically illustrate the operations performed in packaging a product in accordance with the present invention;

F IG. 4 illustrates the packaged product;

FIG. 5 illustrates a soft food product, confined in a rigid or semirigid frame, packaged in accordance with the present invention;

FIG. 6 is the same, employing a rigid or semirigid tray as when packaging unfrozen red meat;

P10. 7 is a plan view of FIGS. 1 and 2, which are taken along a line 1-1 ofFlG. 7;

FIG. 8 is a plan view ofa flat bag constructed in accordance with the present invention; and

FIG. 9 and 10 illustrate product and package configurations which may be readily packaged or overwrapped, respectively, in accordance with the present invention.

in P10. 1 of the drawing a relatively rigid product having a rectangular form in plan is indicated at 10, and shown positioned between an upper film l1 and a lower film 12 on an elongated platten 14. Both films are heat scalable and they may be transparent, translucent, or opaque, or they may comprise any combination of two of the three. The film may be in rolls of long strip with one roll spaced above the other at one end of the platten, and the strips may be pulled or fed longitudinally over the platten by any suitable means as by an underlying conveyor belt (not shown), the products to be packaged being fed between the rolls. The films may also, however, be cut to suitable size for the product and manually placed on a platten with the product between them.

A rectangular sealing head 16 having a continuous electrical resistance sealing and cutoff element 18 extending therearound is slidably mounted for vertical movement above the platten. The rectangular configurations of the product and the sealing and cutoff element 18 are substantially the same, with that of the element 18 being somewhat larger so as to be spaced outwardly ashort distance from the periphery of the product. A film holding device 20 in the form of a rectangular frame having a lower abutment surface 21 is provided to bring the upper film into contact with the lower film and to hold the films firmly against the platten along a line around the periphery of the product spaced outwardly at a predetermined distance therefrom and from the sealing head so that the tensioning of the upper film 11 occasioned by the lowering of the sealing head may be controlled and uniform. The holddown device 20 is also preferably slidably mounted for vertical movement above the platten. A grid 22 in the platten spaced longitudinally from the sealing head with an underlying heat source comprising an electrical resistance heater 24 and a blower 25 are provided to effect heat shrinkage of the lower film 12 after heat sealing and trimming when a heat'shrinkable film-12 is employed.

In packaging a product 10, the product is placed between an upper soft, relatively easily stretchable elastic film l1 and a lower soft, heat shrinkable film l2 lying on the platten. The film holding device 20 is then moved downward, holding both films firmly against the platten. The sealing head 16 is now lowered forcing the upper sheet 11 into contact with lower sheet 12 along a line around and adjacent the periphery of the product. The electrical resistance sealing element 18 is then energized thereby heating the film sufficiently to form a welded seal and to sever both sheets along a continuous line around and adjacent the periphery of the product. Some stretching of the stretchable elastic film 11 occurs as it is forced downward into contact with lower film 12. After seal ing, the film enclosed product is now transported to a position overlying the grid 22 and sufficient heat is applied to the lower heat shrinkable film 12 to draw both films taut about the product and to effect an appreciable stretching of the stretchable film.

It will be understood that film 11 will contract somewhat from its stretched position upon release following the heat sealing operation and consequently the heat sealed seam may be pulled upward somewhat along the sides of the package. However, upon subsequent heat shrinking of film 12, the film 11 will again be stretched substantially. While a single heat seal element 18 is herein disclosed to both heat seal and trim the films, a separate electrical resistance element parallel with and spaced outward slightly from the element 18 and operative to apply greater heat to the films may be employed to sever the films.

When, due to the height ofa product 10 or for other reason, the upper film 11 can be stretched adequately upon lowering of the sealing head 16, heat shrinking oflower film 12 may not be required to obtain a skin tight package, the contraction of the highly stretched elastic upper film being adequate to draw and hold both films taut upon release from the sealing head. In such case the lower film 12 need not be heat shrinkable.

The flat bag shown in FIG. 8 comprises two soft, thin, heat scalable synthetic plastic films, one of which is elastic and relatively easily stretched with relatively little shrinkage when heated and the other is a relatively highly "oriented" heat shrinkable material which shrinks a relatively large amount when heated. The films are heat sealed together and trimmed along the three sides 26. The bag may be readily constructed either manually from rolled film with a U-shaped heat sealing and trim means or on a bag making machine having these expedients. In practice, the bag is made of suitable size and shape to fit the product to be packaged, and permit easy insertion of the product therein. After insertion of the product into the bag, the open side of the bag is heat sealed and trimmed and the heat shrinkable film is then heat shrunk to draw the films taut over the product. The bag is illustrated as comprising two flat rectangular films heat sealed along three sides. One or both films may, however, be gusseted and the bag may have other than a rectangular configuration in plan.

Relatively soft foods or other products confined within a relatively rigid open frame 28, as in FIG. 5, or placed within a relatively rigid tray 30, as in FIG. 6, are packaged in a manner similar to the relatively rigid product 10 in FIGS. 1 to 4.

The packaging of relatively rigid products or the overwrapping of packaged products have other than rectangular configurations in plan, such as conventional candy box configurations shown in FIG. 9 and 10, so as to provide attractive smooth enclosures with heat effectively sealed seams, is readily accomplished with the use ofa stretchable film on one side, a heat shrinkable film on the other and a heat sealing and trim head having a heat sealing and trim element configuration which accommodates the configuration of the product.

The film holddown device 20, shown as having rectangular form in FIG. 7, insures controlled and uniform stretching on all sides of the upper film 11 when the sealing and trim head 16 is moved downward to heat seal the films, as shown in FIG. 2. The holding means 20 is slidably mounted for vertical movement independently of the sealing and trim head 16, so that it may be brought down to hold the sheets firmly on the platten before the sealing head 16 is lowered. The use of film holding means, such as device 20, to hold the films a uniform distance from all sides of the product permits more accurate stretching of the upper film prior to heat sealing so that less heat shrinkage of the shrink film is required to draw the films on all sides of the product and stretch the upper film. It is to be understood, however, that means other than the device 20, shown for holding the film, may be employed. For example, when the films are continuous rolled strips pulled longitudinally over the platten 14 by a belt or other means, it is only necessary to provide means for holding the longitudinal edges of the film to achieve reasonably uniform stretching of the upper film as the sealing heat 16 is lowered.

Synthetic plastic films having the desired characteristics for the purpose of carrying out the invention are known in the art and are commercially available. By way of example, polyvinyl chloride stretch films and polyvinyl chloride shrink films having the required stretchability and elasticity and the required heat shrinkability are commercially available. Moreover, thin relatively highly stretchable polyvinyl chloride films having a relatively high rate of gas transmission are also available commercially. This latter characteristic permits the film to breathe which renders it particularly suitable for packaging fresh meat and obviates the necessity of evacuating or perforating the package to prevent ballooning when heat shrinking an opposed film.

The amount of force which can be exerted by the heat shrinkable film, the resistance to stretching of the stretchable film and the amount of recovery force it can exert due to elasticity when released all increase as the film thickness increases. It is essential, therefore, when using these films in opposition that relative thicknesses be selected which will permit the heat shrinkable film to develop sufficient force to adequately stretch the stretchable film in order to develop therein a sufficient amount of elastic energy to take up subsequent relaxation of the shrink film and maintain a tight package.

By way of example, a satisfactory fresh meat package was constructed in which a soft, stretchable, elastic polyvinyl chloride film 0.0006 inch thick and having a high rate of gas transmission was employed to cover the top and side surfaces of the product and a polyvinyl chloride shrink film. 0.006 inch thick capable of being heat shrunk sufficiently to substantially stretch the upper film was employed to cover the bottom sur face of the product.

We claim:

1. A packaged product including a product and two thin, heat sealable films enclosing the product, the product having upper, lower and side surfaces, one of the films extending substantially over the upper and side surfaces of the product and the other of said films extending substantially over the lower surface thereof and the films being heat sealed together along a line adjacent to and circumscribing the lower surface of the product, the said one film being soft stretchable material capable of being stretched at least 50percent in both directions with substantially complete recovery upon release and said one film being stretched sufficiently over the upper and side surfaces of the product to draw both films taut and to hold them taut over the product.

2. A package product as set forth in claim 1 in which said one film material is transparent and permits a relatively high rate of gas transmission therethrough.

3. A packaged product including a product and two thin, heat sealable films enclosing the product between them, the films being soft and solely shaped and supported by the product, the product having upper, lower and side surfaces, one of the films extending substantially over the top and side surfaces of the product and the other of said films extending substantially over the lower surface thereof and the films being heat sealed together along a line adjacent to and circumscribing the lower surface of the product, the said one film being stretchable and elastic and the said other film being heat shrinkable and capable of developing sufficient energy when heat shrunk to stretch the said one film, and being heat shrunk sufficiently to draw both films taut over the product and stretch the said one film, whereby the package is under tension due to the elastic energy of said one film.

4. A packaged product as set forth in claim 3 in which the said one film permits a relatively high rate of gas transmission.

5. The method of packaging a product which consists in placing the product between two heat sealable synthetic plastic films which are sufficiently soft to be solely shaped and supported by the product, one of the films being relatively stretchable and elastic material and the other being heat shrinkable material, holding the films, stretching the said one film while drawing the films together along a line closely adjacent to and circumscribing the periphery of the product, holding the films together along said line while heat sealing the films together and trimming along said line, and in heat shrinking the said other film sufficiently to draw both films taut and stretch the said one film, said one film comprising at least onehalf of the total area of both films.

6. The method of packaging a product between two thin films of heat sealable synthetic plastic material one of which is soft stretchable material capable of being stretched at least 50percent in both directions with substantially complete recovery when released, which consists in placing the other of said films flat on a platten and placing the product thereon, positioning the said one film on the upper surface of the product, holding the films while stretching the said one film over the upper surface and sides of the product and drawing it into contact with the said other film along a line closely adjacent to and circumscribing the periphery of the lower surface of the product, and in holding said films along said line and against said platten while heat sealing said films together and trimming along said line, and the said one film being stretched sufficiently to maintain a substantial tension on both films when released after heat sealing.

7. The method of packaging a product between two films of heat sealable synthetic plastic material which are sufficiently soft to be solely shaped and supported by the product, one of the films being stretchable and elastic and the other film being heat shrinkable, which consists in placing the said other film fiat on a platten and placing the product thereon, positioning the said one film on the upper surface of the product, holding the films while stretching the said one film over the upper surface and sides of the product and drawing it into contact with the said other film along a line adjacent to and circumscribing the periphery of the lower surface of the product, holding said films together along said line and against the platten while heat sealing the films together and trimming along said line, and in heat shrinking the said other film sufficiently to draw both films taut and stretch the said one film.

8. The method of packaging a relatively soft product as set forth in claim 7 which further consists in placing the product in a relatively rigid open frame on the said other film prior to positioning the said one film on the upper surface of the product.

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