US 3061446 A
Description (OCR text may contain errors)
Oct. 30, 1962 D. P. NORMAN ETA].
METHOD OF PACKAGING FOOD 4 Sheets-Sheet 1 Filed Oct. 5, 1957 Oct. 30, 1962 D. P. NORMAN ETAI.
METHOD OF PACKAGING FOOD 4 Sheets-Sheet 2 Filed Oct. 3, 1957 5 i l J .Uovon \W Nm 96h 1962 D. P. NORMAN ETAL 3,061,446
METHOD OF PACKAGING FOOD 4 Sheets-Sheet 3 Filed Oct. 3, 1957 1962 D. P. NORMAN ETAI. 3,051,446
METHOD OF PACKAGING FOOD Filed Oct. 5, 1957 4 Sheets-Sheet 4 3,061,446 METHOD OF PACKAGING FOOD Daniel P. Norman, Ipswich, and Lawrence W. Kinney, Winchester, Mass., assignors to J. W. Greer Company, Wilmington, Mass, a corporation of Massachusetts Filed Oct. 3, 1957, Ser. No. 687,936 2 Claims. (Cl. 99174) This invention relates to packaging and more particularly to the encasement of food and other products, e.g., meat, fish and fowl portions, within thin, continuous, preferably transparent, skins of plastic material, adherent to and conforming to the outer surface contours of the product even when irregularly shaped.
Packaging of food products for sanitation and preservation in sealed packages is a common expedient. However, there has been a recent trend, partially because of the popularity of self-service stores, to provide transparency in the package so that the enclosed product can be inspected by the purchaser without breaking the seal, as would be necessary with an opaque package.
With the advent of the transparency requirement, the food processor was, as a practicalmatter, relegated to the use of preformed transparent packages because previously proposed coating materials, specifically paraflin and microcrystalline waxes applied by a hot dip, never had suitable transparency even apart from their other deficiencies, such as lack of tensile strength, brittleness particularly at refrigeration temperatures, color instability, etc. Preformed bags and envelopes, no matter what made of, have the deficiency, especially when used as the packages for irregularly shaped products, of leaving air in the package unless vacuumizing is resorted to, a step which is finding increasing use. Packaging in preformed containers is thus complicated because the product first has to be put into the preformed package through a mouth provided for that purpose, followed by a subsequent step of sealing the mouth of the bag with or without vacuumizing. Because the bags are preformed, there is, in the case of irregularly shaped products, always excess material creating folds or gatherings which, in the case of transparent wrappings, often reduce the overall transparency of the package, and if an exhaust is not practiced, it is impossible to eliminate air from such packages.
Nevertheless, use of preformed envelopes of cellophane, polyethylene or other plastic materals, is finding increasing use for lack of other practical packaging methods.
In accordance with this invention, there is provided a practical and efiicient method for encasing products, including irregularly shaped meat or, fowl portions, in situ with an apertureless, clinging continuous seamless skin distributed in approximately uniform thinness around the product, conforming to its outer surface contours and providing a protective covering for the product, the skin having desired physical properties of flexibility, adequate toughness and tensile strength to withstand handling at all temperatures normally encountered in handling and storing, including refrigeration temperatures down to 40 F. and including transparency when desired.
The skin is of such composition that it is readily removable by piercing the skin and peeling it off the product when it is to be prepared for consumption.
To fulfill these physical requirements, resort must be had to plastic materials as distinguished from waxes. However, while the necessary characteristics can readily be found in a variety of plastic materials per se, it has nited States Patent been next to impossible to apply the materials without losing one or more of the desired characteristics. For example, most plastic film formers cannot be maintained in a fluid state for any length of time without initiating degradation-they begin to degrade severely at temperatures below that at which they are fluid. Moreover, they have heat capacities of an entirely different order from waxes so that melting the material from large cakes is slow and cannot be accelerated by raising the temperature because of the dangers of degradation. And even when a tank of undegraded hot melt plastic is obtained, any coating secured by dipping first the bottom, then in-. verting and dipping the top does not have satisfactory sealsthe overlaps either do not seal satisfactorily, if they seal at all, or they leave areas of too great Vapor or air transmission.
Hot melt wax coating processes are hence not amenable to materials having the very different characteristics of the plastic coating materials utilized in accordance with this invention. In fact, experience has shown that, with transparency and refrigeration requirements, preformed packages, despite their expensive handling cost, provide the only present commercially practiced packaging method.
Essentially, the process of this invention comprisesmelting and flowing a plastic film forming material having in its solid form the required physical characteristics onto a product to be packaged to form a continuous,
seamless, clinging skin without materially changing these physical characteristics as a result of the depositing operation through degradation caused either from maintenance at a temperature of fluidity for so long a time as to degrade it or by exposing it to undue aeration while'it' is in its fluid state.
To this end, the invention provides for accomplishing a quick melt of small quantities of plastic coating material followed by immediate application of the hot fluid material at a temperature below that at which it degrades to the article to be packaged from a fluid stream or curtain or overlapping streams or curtains thereof through which the product is passed. Thereafter, the coating is quickly cooled to remove tackiness so that the coated products maybe immediately packed against each other without encountering blocking, i.e., sticking together. The use of the flowing streams or curtains as distinguished from atomized sprays minimizes degrading, aeration and oxidation of the molten plastic material.
Because of the desirability of supporting the article while it is being passed through the curtains, the points ofsupport of the article are changed in the course of advance of the article so that a support which contactssome outer surface portions of the article during a part of the passage of the article towards and through the- One form of apparatus suitable for practising the proc-- ess of this invention is shown in the accompanying draw ings whereinz' FIG. 1 is a cross-sectional view of the apparatus; FIG/2 is a plan view thereof;
FIG. 3 is a cross-sectional detail view taken along the I line 3-3 of FIG. 2;
FIG. 4 is a crosssectional view transversely of the apparatus taken along the broken line 4-4 of FIG. 1;
FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 4;
FIG. 6 is a cross-sectional detail view taken along the line 6-6 of FIG. 5;
FIG. 7 is an enlarged plan view of the nozzles;
FIG. 8 is a side elevational detail view of the nozzles;
FIG. 9 is an end elevational detail view of the nozzles;
FIG. 10 is a detail view of one of the nozzles; and
FIG. 11 is a cross-sectional view taken along line 1111 of FIG. 10.
The main portion of the apparatus includes an upper jacketed hood forming a chamber 22 having at its opposite ends an inlet opening 24 and an outlet opening 25, respectively.
Extending longitudinally across the chamber is an endless open mesh wire belt conveyor mounted around sprockets 32 at the inlet end of the chamber and 34 at the outlet end, the return lower traverse of the belt passing around sprockets 36.
Goods to be processed in the machine are fed onto the chamber belt 30 from an infeed belt and at the outlet end of the chamber are received onto an outgoing endless conveyor 42.
As shown in FIG. 1, the belts 30 and 42 may be conveniently driven through sprocket chain connections to a common motor 44 and the input belt 40 may be driven at substantially the same linear speed by means not shown.
The bottom of the chamber 22 is defined by a jacketed wall providing a sump or tank 46 for molten material. An air-sealed pump 50 is connected by pipe 51 (FIG. 1) to the sump for pumping molten material, without entrapping air, up into a horizontal heat transfer tube 52 containing a central heating unit 54 (FIG. 3) to risers 56 extending up inside the jackets of the chamber 22 and connected to a distributing system best shown in FIG. 4, including an upper transverse connecting pipe 57 leading to a series of branches 59 and 60 and 61 terminating in a series of overhead and side flooding nozzles of the splash plate type as shown in FIGS. 10 and 11. These are so adjusted as to form spray curtains extending angularly with respect to the belt 30, as shown in FIGS. 7 through 9, two from above, angled toward each other and extending across the belt 30, and one from each side.
The branch pipe 61a leads downwardly to a transverse apertured pipe 62 which extends transversely of the chamber beneath the plane of the path of articles as they travel along the belt 30. In order to expose the bottom of the goods directly to the coating material issuing upwardly from pipe 62, the belt 30 is snubbed around two pulleys 63 and 64 (FIG. 3) to provide a gap where the belt 30 goes down around the pipe 62 and back up again.
Hot oil is circulated through jacketed hood 20 by means of an oil pump 69 connected to jacket outlets 70 (FIG. 4) and jacket inlet 71. Any suitable heating means may be provided to maintain the oil at the required temperature.
The oil pump 69 is driven by a motor 73 and the molten plastic pump by a motor 74.
In order to provide a quantity of molten plastic material in the sump, a feeding mechanism is arranged at the back of the machine and has an outlet extending down into the sump 46. A pair of oppositely facing radiant heaters 82 and 84 are situated within a suitable jacketed enclosure 86 having a slot 87 across its top. A pair of opposed feed rollers 90 geared together are mounted with their nip vertically aligned over the opening 87, and are driven by a brake motor 91. The jacket of enclosure 86 communicates with the jacket of the hood 22.
A roll of continuous sheet or strands of plastic material 92 is mounted on an arbor 94 carried by two stanchions 95 and 96.
By driving the feed rolls 90, the plastic material is fed downwardly between the radiant heaters 82 and 84, which instantly melt the material of the sheet, disintegrate the sheet and maintain a predetermined amount of material in the sump for circulation by the pump 50. For this purpose, the sump is conveniently supplied with a level control of the float kind (FIG. 4) which, if desired, operates a switch 101 connected to the motor 91 for the feed rolls 90, so that, whenever the level in the sump falls below a predetermined amount, the motor 91 will be operated to feed further sheet material until the level for which the control 100 is set is reached, at which time the switch 101 shuts off the motor 91.
Similar results may be secured by feeding discontinuous granular material or chips or shavings from a hopper to the heaters.
Also shown in the drawings (FIG. 4) is a temperature control bulb 102 extending into oil in the jacket and controlling the heating unit 54 so that a proper temperature of the material being fed to the nozzles may be maintained.
It will be noted that the tube 52 and pipes 56 are located in the oil jacket so as to provide heat transfer to the oil.
The above apparatus is designed for particular use in coating meat and fowl products with a plastic ethyl cellulose coating material.
A particularly useful material is formulated with the following ingredients:
Parts by weight Ethyl cellulose (10 cps. viscosity) 250 Mineral oil (medium viscosity) 550 Paraplex G-62 200 Antioxidant, e.g., butylated hydroxy toluene (food grade) 2.5
This material has a fluidpoint of about 305 F'., below the degradation point of the ethyl cellulose film-former and the temperature controls of the apparatus are such that it is maintained between 320 and 350 F. The material sets up very quickly with some shrinkage and thus aids in making the coating even, but with high speed operation it is desirable to provide a cooling unit 43 beneath the conveyor 42 in order that the temperature will be brought to at least 100 F. as quickly as possible and thus permit handling of the product without blocking. For this purpose the cooling section may be a slab internally cooled to a temperature of 40 to 60 F. with cold water or in some cases it is possible to immerse the products in or spray the products with cold water for this purpose.
With this material the belts can be operated at a speed of from 40 to 50 feet per minute or more and the chamber can be of a dimension of as little as 2 /2 feet in length so that the products remain within the chamber for only a few seconds.
At this speed of operation the hot melted material is sprayed at a rate of approximately nine gallons an hour over a 10" belt for which purpose it is desirable to provide a sump that has a capacity of about three gallons. The density of this material is such that it requires a feed of about 72-73 pounds of sheet material per hour during continuous operation.
The velocity of the material forming the curtains is such that it helps to drive off excess material and to form a uniform coating which can be of the order of 20 mils in thickness. In the case of the above material, the film is transparent; it is also flexible at temperatures down to and including 40 F. and thus permits subjection of the coated products to quick freezing operations and their storage at the refrigeration temperatures normally required for such products without rendering the coatings brittle. Such material also is non-toxic and does not deteriorate during the time it is being handled, color-wise or otherwise.
Variations can be made in the above formula, for example, as follows:
Preferably the ethyl cellulose is of the type which is 48-50% ethoxylated and it is included in the material in as small a proportion as is required for film-forming purposes and running from to 35% by weight of the total melt. Greater percentage content of ethyl cellulose tends to run the viscosity higher than is desirable for the coating operation. The waxes are used to help decrease the moisture vapor transmission.
Ethyl cellulose is a preferred material because it complies with the food laws, but other thermoplastic filmforming materials properly plasticized and capable of being sprayed from a hot melt to form continuous coatings, for example, vinyl copolymers of acetate-chloride and vinylidene chloride materials, acrylonitrile-butadiene polymers, rubber hydrochloride, cellulose acetate butyrates, polyethylene, polyamides and polyesters are also suitable, particularly where transparency is not a requirement. It is, of course, necessary to make modifications within the skill of the art with respect to the compatibility and proportioning of plasticizers and other ingredients in the case of such other film-forming materials.
In some cases, where requirements of the law do not yet permit the use of an otherwise suitable coating material in direct contact with a food product, a pre-coat of a water soluble food-grade material, such as gelatin, algin or pectin, may be applied, followed by an exterior coat of plastic packaging material in accordance with this invention.
In operation, therefore, the apparatus provides a path for moving products continuously through hydraulic fanshaped thin sheet-like streams or curtains of the coating material directed from both sides and from above and converging on the food product as it advances, and the conveyor in the coating chamber is so designed that portions of the food product which lie against the conveyor during the initial portion of its travel are directly bared to the coating material directed upwardly from the nozzles in pipe 6-2 as the product passes spanningly across the gap in the upper traverse of the conveyor 30. In fact, the spray from pipe 62 being directed upwardly tends to suspend a dam or puddle 104 of material extending across the machine in the gap, into and across which the bottoms of the articles pass, particularly if, as shown, it has beneath it a perforated tray 10 5 to aid in making a wall of liquid about the pipe 62.
106 indicates a downwardly slanted solid sheet bafile which catches the surplus material and flows it back to the right to the sump.
The flow of material is continuous due to the action of the pump 50, and the continued supply of additional material from the sheet source of supply of plastic material is fed in sheet form as required by the level of material in the sump, being melted as it is fed towards the sump.
Despite irregularities in the outer surface contours of the product, fine transparent seamless clinging coverings are secured, thus overcoming all the deficiencies of preformed packages, with consequent savings in material, improvement in appearance, and increased packaging rates.
1. The method of packaging an irregularly shaped food product which comprises melting a sheet of plastic sealing material as it advances in sheet form, flowing the melted plastic material in the form of flat hot streams converging upon a fixed generally horizontal axis and passing the food product along said axis through said streams while baring all the outer surfaces of said product including all surface portions supporting the product to the material forming said streams to form a continuous coating of said plastic material encasing said product and cooling and solidifying said coating to form a thin continuous seamless skin of said plastic material adherent to and conforming to the outer surface contours of and sealing said food product.
2. The method of packaging an irregularly shaped food product selected from the class consisting of meat and fowl which comprises maintaining a substantially constant relatively small volume of molten transparent plastic material as a source of supply by melting said material as it advances in sheet form and feeding it into said supply as said supply is exhausted while continually flowing the molten plastic from the supply in continuous thin curtain form transversely over a fixed generally horizontal plane while also flowing said molten plastic material from the supply upwardly across said plane in the form of a dam of molten plastic material and passing said food product continuously along said plane through said fiowing plastic and with its bottom portion passing transversely through said dam to form a continuous coating of said plastic material encasing said product and solidifying the coating to form a thin continuous seamless tough transparent skin of said plastic material adherent to and conforming generally to the irregular outer surface contours of said food product.
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