US2590221A - Receptacle and method of making the same - Google Patents

Description

March 25, 1952 s. s. STEVENS 2,590,221

RECEPTACLE AND METHOD OF MAKING THE SAME Filed April 25, 1947 5 Sheets-Sheet l INVENTOR SH/ IUEL 5. STEVENS ATTORNEY March 25, 1952 s. s. STEVENS 2,590,221

RECEPTACLE AND METHOD OF MAKING THE SAME Filed April 25, 1947 5 Sheets-Sheetfl INVENTOR mvzuEL S. 5 TEVE/VS TT RNEY March 25, 1952 sQs. STEVENS 2,590,221

RECEPTACLE AND METHOD OF MAKING THE SAME Filed April 25. 1947 3 Sheets-Sheet 3 F5 LU INV TOR SHMUEL 5 TEVENS Ma -g,

A ORNEY Patented Mar. 25, 1952 RECEPTACLE AND'METHOD OF MAKING THE SAME Samuel S. Stevens, Plattsburg, N. Y., assignor, by mesne assignments, to The Diamond Match Company, New York, N. Y., a corporation of Delaware Application April 25, 1947, Serial No. 743,857

10 Claims.

This invention relates to molded fibre 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. The invention is directed to the product and to the method of making the same.

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 filling, 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 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 fiat 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 difficult tov efiectually seal against the passage of vapor and generally produce leakage areas with the result that theproduct may deteriorate or become contaminated.

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 or 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 fine texture and pleasing appearance. The container which results from these operations preferably con- 1sjtitutes the body of the receptacle of this inven- 1011.

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 laminated a relativel thin sheet of an or ganic 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 I have made, to wit: if a relatively thin sheet of an organic thermoplastic is placed against a fibrous surface which is heated to a temperature sufiicient to render the plastic fiowable 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 strata of the sheet will become fused and tend to flow 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 in maintaining at least a portion of the thickness of the plastic sheet, remote from the fibrous 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 willresult and the sheet will not produce an impervious, seal over the fibrous body to which it is applied. Therefore, in the preferred manner of'practicing 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 strata of the organic sheet which engages therewith in its normal-solidified and unfused condition throughout. v

In compositing the body of the receptacl l and its lining or covering sheet, the body of the receptacle is preferably heated by an appropriate die or dies, shaped to conform with the body, so as to raise the temperature of such body to the desired degree. The liner or covering sheet is preferabl formed or shaped to conform with the surface of the body to which 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 formed as 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 strata of the sheet which is in engagement with the body shall have been softened or fused sumciently 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. As shown, the sheet has been laid on the fiat surface of the die and is held there by suction or vacuum applied through the openings in this flat surface.

tion 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 10 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 10, the receptacle will be in the finished form 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:

Cellulose acetate Cellulose acetate butyrate Chlorinated rubber Latex Polyethylene (Polythene) Vinvyl acetal Vinyl acetate Vinyl alcohol Vinyl carbozole Vinyl chloride-vinylidene chloride Rubber hydrochloride (Pliofilm) Cellophane (regenerated cellulose) Vinyl chloride Vinyl chloride-acetate Vinylidene chloride Ethyl cellulose Sodium carboxymethyl cellulose Polyvinyl alcohol Polyvinyl chloride To be efiicient, inexpensive, and readily applicable to the body, this sheet, which is indicated in the drawings 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 ver thin sheet is preferably employed.

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 a liquid-fibre 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 die-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 1 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 sufiiciently 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 be accomplished as a part of the method of making the body. However, this heating may be accomplished by utilizing the die I shown in Figure 4, which is illustrated in this figure as provided with heating channels 2 through which a heating fluid 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 I may be brought to and maintained at an optimum temperature which terior, two chambers 6 and l.

:will manifestly dependupon the particular thermoplastic of which the-sheet S is: constituted. To assist 'in theheating of the innersurface of thebody B andto' protect the outer surface an'dprevent heat froinbeing radiated therefrom, I provided a second die 3, shown in Figure 5, whichzserves 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 t or by any other suitablemeans. Ll. socontrol the temperatures of dies l and 3 Ithatthe inner surface of the article will be heated .tojust 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 or pre-form the sheet of thermoplastic material, I provide a die structure 5 shown in Figure 6. This die structure has, in item- From the chamber l, passages'or ducts 1a lead to the upper or flat 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 overhang the sides of the die. Suction may be communicated; to the chamber 1 to holdthesheet in place on the die while the overhanging or pro.- .jecting 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 1 either before, during or after the forming operation will hold the sheet in this conformity upon the completion thereof.

In practice thesheet S may be preliminarily cut to a contour of the exact shape and size necessary to exactly cover the interior surface andrupper edges of the body B soasto eliminate thenecessity for subsequent trimming but in practiceI prefer to form this sheet well oversize andto trim it after it has been formed, as shown in Figure 7, by trimming knives II], as illustrated in Figure 8, which trim from the margins the excess-ll.

In Figure 6 it will be noted that the die 5 is mounted upon a member I! which is in effect -a-coo1ing plate, provided therein with passages j,l3;th10ugh which a cooling medium may be circulated to cool the die 5 and thus keep the surface strata of the sheet contiguous therewith at all times below its fusion or disintegrating point by drawing off 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 l3, the temperature of the die surface which" engages thesheet maybe accurately regulated and maintained at such degree as to pre- 'clude fusionthereof and-maintainits contiguity.

In practice it, is found'convenient toprepare the 6 sheets-forapplicationto thebody B=while the latter is being heated.

- Afterthe 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 applying die M, such as shown in Figure 9. The die 14 is chamberedas shown at 15 and suction may be communicated to this chamber through a pipe I6 and made effective upon the inner surfaceof the die through suction passages. The die 14 is backediup by a plate l8 having therein passages).- so that: the-temperature of the die l4 may 'be'controlled. Either a heating or a; cooling fluidimay be circulated through thepassages I9 as may be desired at different stages of the method.

The die I4, 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 thebody remains on the hot die I, sothat the. parts appear as shownin Figure 9. Suction is applied to the chamber 1 5 and causes the article to be gripped by the'die-M'so that said die l4 may be moved relative to the-die l'to remove the body B from said die and transfer said'body into the position shown in Figure-10 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 willnot appreciably cooland,-'if*desired, thedie I4 may be a heated die at this time to-keep the'bodyhot.

When the relatively cool sheet S is brought into contact with the surface of the-hot body B, and theyare'pre'ssed together by the cooperating dies 5 and M, as shown in Figure 10, the heat of the contacting surface of the hot body-fuses or softens the contiguous strata 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 thermoplasticmaterial may be carried so far as to cause the fused and softened plastic to flow 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'articl'e 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 flow 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 hotbody, the opposite surface strata 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 article and from between the parts.

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 fiow 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 sufliciently heated to heat-seal themselves; so that they will not thereafter tend to open or separate.

I have referred to pressure between the dies and M 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 plasticjto enter into the chamber 1 through pipe 9, circulate through passages la 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 rough or smooth finished container bodies and, irrespective of the thickness of the sheet, but it is particularly eflicient in applying relatively thin sheets to other than smooth die-dried surfaces.

It is also feasible to apply thicker sheets to the rougher surfaced articles wholly by die pressur'e and without the use of compressed air as stated, but, when this is done, the sheets should be sufficiently thick to permit substantially allover surface contact during the fusing step with concurrent effective maintenance of the opposite surfacestrata 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 l4, through the suction pipe l6, during the entire compositing period, so as to draw such entrained air through the article body and thu evacuate it from the 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 l4.

After the fusion step has taken place, the die I4 may be immediately removed leaving the composited finished receptacle on the die 5, from which it may be removed by any suitable pick-off die or by hand, or, if desired, the dies 5 and is may be left in assembled relation while the cooling medium is circulated through the passages l9 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 the die I4 may be utilized as a pick-off die to remove the finished receptacle from the die 5 and transfer it to any appropriate discharge station for packing or otherwise.

Experience with the method hereinbefore de-- scribed 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 fiat layer of fibrous material corresponding to the body and having composited 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 thi invention, although I preferably heat-seal 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.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which comprises: heating an imperforate fibrous receptacle body to a temperature above the fusion temperature of the thermoplastic sheet to be composited therewith, thereafter shaping and bringing such sheet of thermoplastic into facially contacting conformation with one face of said imperforate heated fibrous body, and holding them in contactfor a sufficient period of time to permit the heat of the body to fuse the surface strata of the contiguous side of the sheet into bonding condition while maintaining the opposite side of the sheet at a temperature below the fusion point of such thermoplastic, whereby the sheet and fibrous body become firmly adhered together by solidification and setting of the resulting thermoplastic bond when subsequently cooled.

2. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which comprises: heating an imperforate fibrous receptacle body to a temperature above the fusion temperature of a thermoplastic sheet to be composited therewith, thereafter shaping and bringing such sheet of thermoplastic into facially contacting conformation with one face and the open edge of said imperforate heated fibrous body, and holding them in contact for a sufiicient period of time to permit the heat of the body to fuse the surface strata of the contiguous side of the sheet into bonding condition while maintaining the opposite side of the sheet at a temperature below the fusion point of such thermoplastic, whereby the sheet and fibrous body become firmly adhered together by solidification and setting of the resulting thermoplastic bond when subsequently cooled.

3. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which comprises: forming a sheet of thermoplastic into a shape to substantially conform to one surface of the fibrous receptacle body with which said sheet i to be composited, heating the fibrous receptacle body while free from contact with said formed thermoplastic sheet to a temperature above the fusion temperature of said thermoplastic sheet, thereafter bringing the formed thermoplastic sheet and the heated fibrous receptacle body into conforming facial contact, and holding them in such contact for a sufficient period of time to permit the heat of the receptacle body to fuse the surface strata of the contiguous side of the sheet into bonding condition while maintaining the opposite side of the sheet at a temperature below the fusion temperature of the thermoplastic sheet, whereby the sheet and fibrous body become firmly adhered together by solidification and setting of the resulting thermoplastic bond when subsequently cooled.

4. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which comprises: folding a flat thermoplastic sheet into a shape to conform with one surface of the fibrous receptacle body with which said sheet is to be thereafter composited, heating the fibrous receptacle body while free from contact with said folded thermoplastic sheetto a temperature above the fusion temperature of said sheet, thereafter bringing the folded thermoplastic sheet and the heated receptacle bodyv into nesting relation with their contiguous faces in contact, and maintaining them in such contact for a sufficient period of time to permit the heat of the receptacle body to fuse the surface strata of the contiguous sides of the sheet into bonding condition while maintaining the opposite sides of the sheet at a temperature below the fusion temperature of the thermoplastic sheet, whereby the sheet and fibrous body become firmly adhered together by solidification and setting of the resulting thermoplastic bond when subsequently cooled.

5. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which comprises: heating and impercrate fibrous receptacle body to a temperature above the fusion temperature of the thermoplastic sheet to be composited therewith, thereafter shaping and bringing such sheet of thermoplastic into facially contacting conformation with one face of said imperforate heated fibrous body, holding them in contact for a sufficient period of time to permit the heat of the body to fuse the surface strata of the contiguous side of the sheet into bonding condition, cooling the opposite side of the sheet to a temperature below the fusion point of the thermoplastic while the surface strata in contact with the heated fibrous body is being fused, and applying suction to the surface of the fibrous receptacle body remote from the thermoplastic sheet during the fusion step of the method.

6. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which'comprises: folding a fiat thermoplastic sheet into a shape to conform with one surface of the fibrous receptacle body with which said sheet is to be thereafter composited, heating the fibrous receptacle body while free from contact with said folded thermoplastic sheet to a temperature above the fusion temperature of said sheet, thereafter bringing the folded thermoplastic sheet and the heated receptacle body into nesting relation with their contiguous faces in contact, and maintaining them in such contact for a sufficient period of time to permit the heat of the receptacle body to fuse the surface strata of the contiguous sides of the sheet as well as the thermoplastic material of the folds of said sheet into bonding condition while maintaining the remote outer surface of the sheet at a temperature below the fusion temperature of the thermoplastic sheet, whereby the sheet and fibrous body as well as the contacting surfaces of the folds of the sheet become firmly adhered to- 10 gether by solidification and setting of the resulting thermoplastic bond when subsequently cooled.

7. The method of compositing an imperforate fibrous receptacle body and a sheet of thermoplastic which comprises: heating an imperforate fibrous receptacle body on a conforming heating die to a temperature above the fusion temperature of the thermoplastic sheet to be composited with said body, die forming a flat thermoplastic sheet in dies corresponding in shape and size to the heating die of the receptacle body while all portions of said sheet are maintained below fusion temperature, then nesting the formed thermoplastic sheet and the heated receptacle body into facial contact with one another to cause the heat of the receptacle body to fuse the contiguous surface strata of the thermoplastic sheet into bonding condition with the contacting side of the receptacle body. and cooling the opposite surface of the thermoplastic sheet during the fusion step to preclude the fusion of the surface strata thereof, and thereafter permitting the resulting composited assembly to cool for the purpose of solidifying and setting the resulting thermoplastic bond between the thermoplastic sheet and the fibrous receptacle body.

8. The method claimed in claim 7, including the further step of applying suction during the fusion step to the surface of the fibrous receptacle body remote from the thermoplastic sheet.

9. The method of compositing a fibrous body and a sheet of thermoplastic which comprises: heating the fibrous body to a temperature above the fusion temperature of the thermoplastic sheet, bringing the thus heated body and the thermoplastic sheet into faoially contacting relation and holding them in this relation until the heat of the body fuses the surface strata of the contacting face of the sheet, and cooling the opposite face of the sheet during the fusion period to contemporaneously maintain the surface strata of the latter face of the sheet in solid unfused condition.

10. The method of compositing a fiat layer of fibrous material and a sheet of thermoplastic which comprises: heating the layer of fibrous material to a temperature above the fusion temperature of the thermoplastic sheet, bringing the thus heated fibrous layer and the thermoplastic sheet into facial contacting relation and holding them in this relation until the heat of the layer fuses the surface strata of the contacting face of the sheet, and cooling the opposite face of the sheet during the fusion period to contemporaneously maintain the surface strata of the latter face of the sheet in solid unfused condition.

SAMUEL S. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 478,851 France July 12, 1892 1,101,972 Swezey June 30, 1914 1,866,312 Loetscher July 5, 1932 1,867,575 Loetscher July 19, 1932 2,003,494 Reynolds June 4, 1935 2,319,267 Sawyer May 18, 1943 2,344,488 Bowling Mar. 21, 1944 2,376,805 Peacock May 22, 1945

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