US 2780401 A
Description (OCR text may contain errors)
Feb. 5, 1957 s. s. STEVENS 2,780,401
RECEPTACLE Original Filed April 25, 1947 5 Sheets-Sheet 1 INVENTOR Jdmuel 619216196205.
ORNEY Feb. 5, 1957 v s. '51. STEVENS 2,780,401
A RECEPTACLE original Filed April 25, 1947 5 Sheets-sheet z INVENTOR United States Patent() RECEPTACLE Samuel S. Stevens, Plattsburgh, N. Y., assignor, by mesue assignments, to The Diamond Match Company, New York, N. Y., a corporation of Delaware Original application April 25, 1947, Serial No. 743,357. Divided and this application February 1, 1952, Serial No. 269,473
3 Claims. (Cl. 229-25) This application is a division of application, Serial No. 743,857, tiled April 25, 1947, which issued March 25, 1952, as Patent 2,590,221, on the method of making the receptacle of `this invention.
This invention relates to molded libre articles having an interior liner or exterior covering, or both, of an organic plastic to render the wall of the article impervious to vapors and liquids.
Without limiting the invention to an article for any specific use, reference may be made, for the purpose of illustration, to the employment of this invention in connection with molded fibre receptacles suitable for packaging frozen food products. For the successful and effective packaging of such products, it is necessary to have a sturdy package which will withstand machine handling incident to lling, packaging and sealing of the food product and one which will withstand rough handling in storage and delivery to the ultimate consumer.
It is also necessary that such a receptacle retain all of the constituents of its contents and prevent the ingress or egress of fluid or vapors which would contaminate the product if coming from the outside and would permit the loss of essential ingredients of the product if allowed to escape from the inside. For example, it is both desirable and necessary to retain within the package the water or moisture content of the product throughout the time when it is stored, so that when it reaches the consumer, it will be in exactly the same state and condition as when it was packed.
In food packages of the type heretofore used for the packaging of frozen foods, it has been customary to form the package from flat sheet stock or board by either or both cutting and folding it into receptacle form. If the sheet of material thus used is surface pretreated by ordinary coating methods, prior to forming it into the receptacle, the forming operation tends to break or weaken the coating along the fold lines or creases, with the result that leakage or contamination of the product may result. Furthermore, the folds or creases are ditlcult to etfectually seal against the passage of vapor and generally produce leakage areas with the result that the product may deteriorate or become contaminated. h
In contradistinction to the conventional prior practice, the container of the present invention is molded and dried in its ultimate shape without creases, folds or score lines of any kind in its surface, so that its wall may be of substantially uniform thickness throughout and consequently of maximum `strength and rigidity for the stock employed. This container may be conveniently produced by suction molding it either from wood pulp orv other fibres, on a forming die to the desired shape and thereafter drying the resulting article between hot drying dies while under pressure between said dies to produce a relatively smooth surfaced article of ne texture and pleasing appearance. operations preferably constitutes the body of the receptacle of this invention. t y
The container which results from these 7 In carrying out the present invention, I start with a molded container body of this character. Over the interior or exterior of such body is then laminted a relatively thin sheet of an organic plastic which is adhered to said body at all points where it comes in facial contact therewith. The preferred method of adhering the sheet to the body is based upon certain discoveries which l have made, to wit: if a relatively thin sheet of an organic thermoplastic is placed against a brous surface which is heated to a temperature sufficient to render the plastic llowable or tacky while the opposite surface of such sheet is maintained at a temperature below the softening point of the plastic and pressure is applied to the sheet, the thus heated surface stratum of the sheet will become fused and tend to lflow into the interstices of the contacting fibrous surface with the result that, when the fibrous article is subsequently cooled, that portion of the plastic which has entered into its structure will harden therein and form therewith a permanent bond between the fibrous material and the plastic sheet.
An important requirement of this procedure consists of maintaining at least a portion of the thickness of the plastic sheet, remote from the brous body, in solid unfused condition throughout the entire operation for it has been found that, if the heat of such body penetrates entirely through the plastic sheet so as to fuse it for its entire thickness, the contiguity of the sheet will be destroyed, pin holes will result and the sheet will not produce an impervious seal over the fibrous body to which it is applied. Therefore, in the preferred manner of practising the present invention, the dies or other expedients, through the utilization of which the organic sheet is applied to the fibrous surface, are preferably cooled by water or air circulation or otherwise to maintain that stratum of the organic sheet which engages therewith in its normal solidified and unfused condition throughout.
ln compositing the bodyof the receptacle and its lining or covering sheet, the body of the receptacle is preferably heated by an appropriate die or dies, shaped to conforml with the body, so as to raise the temperature of such body to the desired degree. The liner or covering sheet is preferably formed or shaped to conform with the surface of the body to whichf it is to be attached, on a complementary die which is preferably provided with means for maintaining said die cool. After the container body is heated and the plastic layer has been foirned Vas stated, they are brought together, preferably on substantially conforming complementary dies, to effect surface contact between the container body and the plastic sheet and they are thereupon held in such contact until the surface stratum of the sheet which is in engagement with the body shall have been softened or fused suiciently to provide an effective bond while the remainder of the thickness of the sheet is kept below its fusion point. After fusion, with or without penetration, has occurred, the entire article is cooled to complete the assembly.
Features of the invention, other than those specified, will be apparent from the following detailed description and appended claims when read in conjunction with the accompanying drawings, wherein- Figure 1 shows the cross section through an illustrative type of molded fibre article to which the liner covering sheet is to be applied. This article may be round, rectangular, square, or of any desirable shape.
Figure 2 shows a piece of flat sheet stock to be applied to the article of Figure 1.
Figure 3 shows the finished article in cross section with the sheet applied thereto as a liner.
Figure 4 shows the cross section of a heated die with the article of Figure 1 thereon'.
Figure 5 shows the fibre article being held between two heated dies to insure that the article is properly preheated, the outer die, or the die on the bottom of the article, preventing the escape of heat applied by the die heating the inner surface of the article.
Figure 6 shows the die on which the liner sheet is preformed. A s shown, the sheet has been laid on the at surface of the die and is held there by suction or vacuum applied through the openings in this flat surface.
Figure 7 shows the die of Figure 6 with the sheet folded down over the sides of the die by means not shown, with the surplus material being taken up by folding the sheet over on itself. If desired, in the case of a polygonal article, the portion of the sheet may be cut out at the corners to facilitate its being shaped over the die of Figure 6.
Figure 8 shows the surplus material at the periphery of the sheet being removed, leaving the sheet of just the size to overlie and cover the inner surface of the article and the upper edge of the latter.
Figure 9 shows a transfer die for removing the article from the die of Figure 4. This is preferably a suction or vacuum die.
Figure l() shows the article held between the transfer die of Figure 9 and the sheet applying die of Figure 6. After removal from between the two dies shown in Figure l0, the receptacle will be in the finished forrn shown in Figure 3.
According to this invention the plastic sheet may be made to cover either or both the inner and outer surfaces of the container body. However, for the purpose of concrete illustration, I will hereinafter describe the mode of applying such sheet to the inside and upper surfaces of the container body so that it will serve as a liner therefor. It should be noted, however, that the same procedure may be utilized in applying said sheet to the exterior surfaces of such body.
The sheet material preferably used for this purpose in accordance with this invention is in the nature of an organic plastic having thermoplastic properties and while many such synthetic plastics may be employed, the following may be referred to as illustrative, viz.:
To be efficient, inexpensive, and readily applicable to the body, this sheet, which is indicated in thedrawings by the reference character S, should be quite thin. The drawings show the sheet relatively thick for the purpose of illustration, but, in practice, a very thin sheet is preferably employed. v
The container body illustrated in Figure l and indicated by the reference character B is of molded fibre, as hereinbefore indicated, and it is of finished shape without folds or creases.
It is desirable to use a sheet S of minimum thickness, and, accordingly, I preferably employ a container body B of the kind which is suction molded'from 4a liquidlibre mixture, e. g., paper pulp, and subsequently die dried by pressing a heated die against at least the surface of the body to which the sheet S is to be applied. This produces on the molded and dic-dried article a smooth even surface well adapted to contact throughout with a thin sheet of plastic material also having a smooth even surface.
To effectually unite the sheet S of Figure 2 and the container body B of Figure l according to this invention to form a unitary structure wherein the parts are substantially permanently adhered to one another, it is necessary to bring the surface of the body to which the liner sheet S is to be applied to a temperature sufficiently high to fuse or soften such sheet but not so high as to disintegrate it throughout its thickness when manipulated as hereinafter described. The heating of the body may bc accomplished as a part of the method of making the body. However, this heating may be accomplished by utilizing the die 1 shown in Figure 4, which is illustrated in this ligure as provided with heating channels 2 through which a heating iiuid may be circulated or in which an electrical heating element may be positioned for this purpose. Through the employment of such appropriate heating means, the die 1 may be brought to and maintained at an optimum temperature which will manifestly depend upon the particular thermoplastic of which the sheet S is constituted.
To assist in the heating of the inner surface of the body B and to protect the outer surface and prevent heat from being radiated therefrom, I provide a second die 3, shown in Figure 5, which serves to press the inner surface of the article against die I and hold it in firm contact therewith. Die 3 may be heated by electric heating elements 4 or by amI other suitable means.
I so control the temperatures of dies 1 and 3 that the inner surface of the article will be heated to just the proper temperature to facilitate the application of the sheet of thermoplastic material and to insure an even and uniform adhesion thereto.
To pre-shape a preformed sheet of thermoplastic material, I provide a die structure 5 shown in Figure 6. This die structure has, in its interior, two chambers 6 and 7. From the chamber 7, passages or ducts 7a lead to the upper or at surface of the die while passages 6a lead from the chamber 6 to the exterior sides of the die so that partial vacuum or suction may be communicated to these exterior surfaces. Vacuum or suction connection to chamber 6 is provided by pipe 8 and a similar vacuum or suction connection to space 7 is provided by pipe 9.
In preparing the sheet S for application to the container body, such sheet is rst positioned on the upper surface 0f the die 5 as shown in Figure 6. Its central portion will rest flat on the upper surface of the die while its marginal portions will project beyond such upper surface and overhang the sides of the die. Suction may be communicated to the chamber 7 to hold the sheet in place on the die while the overhanging or projecting portions of the sheet are folded down over the sides of the die successively, the surplus material being taken up by a series of pleats or folds so that the sheet is caused to closely conform to the die 5 as shown in Figure 7. This conforming of the sheet to the die may be accomplished manually or by any appropriate folding or forming means but in any event suction communicated to the chambers 6 and 7 either before, during or after the forming operation will hold the sheet in this conformity upon the completion thereof.
In practice the sheet S may be preliminarily cut to a contour of exact shape and size necessary to exactly cover the interior surface and upper edges of the body B so as to eliminate the necessity for subsequent trimming but in practice I prefer to form this sheet well oversize and to trim it after it has been formed, as shown in Figure 7, by trimming knives 10, as illustrated in Figure 8, which trim from the margins theexcess 11.`
In Figure 6 it will be noted that the die 5 is mounted upon a member 12 which is in effect a cooling plate, provided therein with passages 13 through which a cooling medium may be circulated to cool the die and thus keep the surface stratum of the sheet contiguous therewith at all times below its fusion or disintegrating point by drawing oif enough heat from that face of the sheet to accomplish this result. By controlling the temperature of the'water or other medium which is circulated through the passages 13, the temperature of the die surface which engages the sheet may be accurately regulated and maintained at such degree as to preclude fusion thereof and maintain its continuity. In practice it is found convenient to prepare the sheet S for application to the body B while the latter is being heated.
After the plastic sheet has been formed as shown in Figure 7 and trimmed as shown in Figure 8 and the container body has been heated to the desired temperature, these parts .are laminated. This may be conveniently accomplished by means of a combined transfer and api plying die 14, such as shown in Figure 9. The die 14 is chambered as shown at 15 and suction may be communicated to this chamber through `a pipe 16 and made effective upon the inner surface of the die through suction passages 17. The die 14 is backed up by a plate 18 having therein passages 19 so that the temperature of the die 14 may be controlled. Either a heating or a cooling fluid may be circulated through the passages 19 as may be desired at different stages of the method.
The die 14, when utilized as a transfer die, is brought into contact with the exterior face of the hot body B after the die 3 of Figure 5 has been removed therefrom and while the body remains on the hot die 1, so that the parts appear as shown in Figure 9. Suction is applied to the chamber 15 and causes the article to be gripped by the die 14 so that said die 14 may be moved relative to the die 1 to remove the body B from said die and transfer said body into the position shown in Figure l0 wherein it is contacted with the formed sheet on the die 5. This operation is carried on expeditiously so that the interior surface of the container body will not appreciably cool and, if desired, the die 14 may be a heated die at this time to keep the body hot.
When the relatively cool sheet S is brought into contact with the surface of the hot body B, and they are pressed together by the cooperating dies S and 14, as shown in Figure l0, the heat of the contacting surface of the hot body fuses or softens the contiguous stratum of the plastic layer. In some cases, the fusion of the sheet may be carried only to such a point as to produce a sufficiently tacky condition of the plastic to effect adherence of the sheet to the body when both are restored to room temperature. In other cases, the fusion of the thermoplastic material may be carried so far as to cause the fused and softened plastic to ow into surface conformity with the body and enter to some extent into the interstices of the fibrous structure thereof.
The latter procedure may be very efficiently carried out if the container body B is of the smooth die-dried variety, for the surface of such an article is so smooth and even as to Contact with practically all portions of the smooth and even surface of the plastic sheet and it thus requires very little ow of the plastic to effect the penetrating, interlocking bond which thus occurs. Even with this type of finish merely a tacky condition may be availed of to form the bond if desired. However, in adhering the sheet to some of the rougher types of container body, the tacky condition is recommended and it is not recommended that any attempt be made to appreciably flow a portion of the thickness of a relatively thin sheet into conformity with a rough, uneven surface, although it may be done with a thicker sheet.
It should be noted that, during the fusion of that portion of the plastic sheet which contacts with the hot body,
the opposite surface stratum of the sheet is kept below its fusion point by the cooling effect of the relatively cool die 5 with which it contacts, but this `cooling effect of the die is localized at this surface of the sheet and does not preclude the amalgamation of the folds which were formed in the sheet during the forming step shown in Figure 7. In fact, if the material is permitted to flow considerably the contacting portions of the material in these folds will fuse together and become substantially homogeneous. Even when only the tacky condition, hereinbefore referred to, is produced, the folds will be sufficiently heated to heat-seal themselves, so that they will not thereafter tend to open or separate.
I have referred to pressure between the ldies 5 and 14 as utilized to press the sheet :and container body into intimate relation with one another. If desired, these dies may be provided with some clearance between their coacting faces and merely make a firm seal around the edges of the article, so as to permit compressed air, at a temperature below the fusion point of the plastic, to enter into the chamber 7 through pipe 9, circulate through passages 7a to the outer surface of the die 5 and along the outer surface of such die to passages 6a, and through said passages to the chamber 6, to exit through the pipe 8. If compressed air is thus admitted, the sheet will be forced firmly against the hot contacting surface of the body B and contact throughout these parts may thereby be assured.
The use of compressed air in the manner stated may be availed of in applying the thermoplastic sheet to either roughor smooth finished container bodies and, irrespective ofthe thickness of the sheet, but it is particularly efiicient in applying relatively thin sheeets to other than smooth die-dried surfaces.
lt is also feasible to apply thicker sheets to the rougher surfaced articles wholly by die pressure and without the use of compressed air as stated, but, when this is done, the sheets should be sufficiently thick to permit substantially all-over surface contact during the fusing step with concurrent effective maintenance of the opposite surface strata of the sheet below its fusion temperature.
When the sheet S and the body B are superimposed, air
is apt to be trapped therebetween and unless this air is removed, proper bonding is practically impossible. For this reason suction should be maintained within the die 14, through the suction pipe 16, during the entire compositing period, so as to draw such entrained air through the article body and thus evacuate it from the article and from between the parts. Moreover, this suction should be maintained throughout the fusion period and it is preferably continued until this step is completed and the assembled body and sheet are removed from the die 14.
After the fusion step has taken place, the die 14 may be immediately removed leaving the composited finished receptacle on the die 5, from which it may be removed by any suitable pick-olf die lor by hand, or, if desired, the dies 5 and 14 may be left in assembled relation while the cooling medium is circulated through the passages 19 to lower the temperature of the entire assembly to a point whereat the thermoplastic will solidify and set with the parts permanently bound together. Thereafter lthe die 14 may be utilized as a pick-off die to remove the finished receptacle from the dieS and transfer it to any appropriate discharge station for packing or otherwise.
Experience with the method hereinbefore described has demonstrated its efficacy in the production of a strong and durable receptacle absolutely impervious to the passage of vapor and moisture and well adapted for the hermetic sealing of the package which it forms. Any suitable cover may be associated with this receptacle but it is preferably in the form of a flat layer of fibrous material corresponding to the body and having composited v therewith a sheet of thermoplastic material united thereto in the same manner as that employed in compositing the receptacle. Such cover may be secured in place in any appropriate manner or by any desired means without departing from this invention, although I preferably heatseal it in position on the receptacle.
The foregoing detailed description sets forth the invention in its preferred practical form, but the invention is to be understood as fully commensurate with the appended claims.
In the appended claims, reference to a molded fibrous body defines the well known type or physical character istic of the body as distinguished from the folded sheet paper or cardboard type of product. Hot pressure die dried finish refers to that characteristic and readily recognizable smooth surface finish which results from the drying of a wet molded pulp surface by contact with a hot smooth surfaced die. These terms, as well as the term fusion-bonded, define the characteristics of the parts and are well understood as such by those working in the pulp molding and plastic arts.
Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:
1. A receptacle comprising: an open top molded fibrous body one face of which is provided with a hot pressure die dried finish, said body having a bottom and an upstanding peripheral side wall, and a relatively thin preformed sheet of non-fibrous thermoplastic material permanently fusion-bonded directly against the face of said bottom and side wall of the body which has the hot pressure die dried finish by the body contacting surface stratum of the sheet itself, said sheet being free from fusion-caused perforations and forming an impervious seal over the surface of the body.v
2. A receptacle according to claim 1 comprising: a
fibrous cover having a thermoplastic liner fusion-bonded to the fibrous cover and to the non-fibrous thermoplastic sheet which is attached to the body to form an impervious seal with said` sheet and hermetically seal the receptacle.
3. A receptacle comprising: an open top molded fibrous body having a bottom and an opstanding peripheral side wall, and a relatively thin pre-formed sheet of nonfibrous thermoplastic material permanently fusion-bonded directly against one surface of said bottom and side wall by the body contacting surface stratum of the sheet itself, said sheet being free from fusion-caused perforations and forming an impervious seal over the surface of said body.
References Cited in the file of this patent UNITED STATES PATENTS 2,028,076 Norris Ian. 14, 1936 2,150,910 Chaplin Mar. 21, 1939 2,293,568 Snyder Aug, 18, 1942 2,298,421 Salfisberg Oct. 13, 1942 2,319,267 Sawyer May 18, 1943 2,466,966 France et al. Apr. 12, 1949 2,542,413 Ibsch Feb. 20, 1951 2,555,380 Stuart et al. June 5, 1951 2,565,336 Adler Aug. 21, 1951 2,620,289 Douglas Dec. 2, 1952 2,641,402 Brunn June 9, 1953 FOREIGN PATENTS 103,316 Great Britain June 20, 1936 te* Mp