US2777626A

US2777626A - Tray with cork surface portions and method of making

Info

Publication number: US2777626A
Application number: US406702A
Authority: US
Inventors: Richard S French
Original assignee: Keyes Fibre Corp
Current assignee: Keyes Fibre Corp
Priority date: 1954-01-28
Filing date: 1954-01-28
Publication date: 1957-01-15
Anticipated expiration: 1974-01-15

Description

Jan. 15, 1957 R. s. FRENCH TRAY WITH coax SURFACE PORTIONS AND METHOD OF MAKING Filed Jan. 28, 1354 2 Shets-Sheet 1 IN VEN TOR.

RICHARD S. FRENCH BY Jan. 15, 1957 R. s. FRENCH 2,777,626

TRAY WITH CORK SURFACE PORTIONS AND METHOD OF MAKING Filed Jan. 28, 1954 2 Sheets-Sheet 2 INVENTOR. RICHARD 5. FRENCH S ATTORNEYS TRAY WITH CDRK SURFACE PDRTIONS AND METHOD F MAKING Richard S. French, Water-ville, .Maine, assignor to Keyes Fibre Company, Portland, Maine, a corporation of Maine Application January 28, 1954, Serial .No. 406,762

16 Claims. (Cl. 2292.5)

The present invention relates to trays in which :portions .of the surface are covered with cork.

Among the objects of the present invention is the .provision of novel trays of the above type in which the cork surfacing is particularly resistant to mechanical and chemical treatment, as well as the provision of novel methods for making such trays.

The above as well as additional objects of the present invention will be more clearly understood from the following description, reference being made to the accompanying drawings wherein:

Fig. 1 is a perspective view of a tray illustrating the present invention;

Fig. 2 is a sectional view of the tray of Fig. 1 taken along the line 22;

Fig. 3 is an exploded sectional view showing a step in the making of the tray of Fig. 1; and

Fig. 4 is a perspective view of a modified form of tray exemplifying the present invention.

It has been discovered that fiber-resin trays with thin cork sheets securely aflixed to portions of its surface, can be readily provided by molding the sheets onto the tray surface when the tray is itself being molded. The tray thus formed has the cork sheet partially imbedded in its surface so that the sheet margins are .difilcult and in fact just about impossible to disengage from the tray surface, either by mechanical or chemical action. At the same time the resin of the tray works its way at least partially into the cork sheet thereby not only anchoring it securely but also making the sheet much more resistant to disintegration, .tearing or chemical attack. All these advantages are obtained notwithstanding the fact that the cork sheet will have its outer surface above the surrounding surface of the tray so that the cork will be fully effective in contributing its noise-reduc ing and skid-resistant properties to :the tray.

A feature of the present invention is that no special precautions need to be taken to assure the partial imbedding and partial projection of the thin cork sheet. Under the influence of the large molding pressures, the cork sheet becomes compressed and substantially completely imbedded, but when the molding is completed the release of the molding pressure causes the cork to expand, thereby raising its outer surface above the balance of the tray.

Referring now to the drawings, Fig. 1 shows a fiberresin tray which is basically constructed in the manner disclosed in U. S. Patent No. 2,274,095, granted February 24, 1942. This specific tray has a generally fiat body 12 surrounded by side walls 14 and, as more clearly shown in Fig. 2, has a core 21 of relatively low resin content sandwiched between layers 22, '23 that are richer in resin. The body 12 has above its central portion a thin sheet or layer of cork 25 that is securely anchored in place and'at least partially permeated by some of the resin of the upper layer 22. In addition the margin 27 of the cork Sheet has its lower portions embedded in ice the fiber layer '22 although .the upper portions of the margin 27 project above that layer.

By reason of the presence of resin in the cork sheet 25, the cork is extremely securely bonded together in place. Furthermore the partially recessed condition of the edges of the cork sheet make it very difficult for the edge to be cut by mechanical engagement with cutlery for example or by ones finger nails.

As a result the cork is particularly hardy and resistant to all types of influences and can be used in a great many applications. By way .of example, no normal amount of contact with chinaware, cutlery or food utensils of any kind has any detectable effect on the tray of the present invention. Even repeated vigorous scraping .with such articles fails to produce detectable changes. The entire tray including the cork lined surface, can be subjected to boiling water, alcoholic beverages and boiling detergent solution without appreciable loss of Weight, change in appearance orloosening of the cork.

A feature of the invention is that by the partial imbedding of the cork, thedesired noise-reducing and skidresistant portions of the cork can be provided even though the cork does not extend over the entire upper surface of the tray. In fact the cork layer can be interrupted as by means of attractive design features, stencils, silhouettes, etc., that can be used to improve the trays appearance. The interrupted construction is conveniently prepared by merely correspondingly blanking out portions of the continuous cork layer before the layer is molded in as part of the tray. At these portions the upper surface 22 of the final tray will be exposed and will occupy a recessed .level corresponding to the level .of this surface around the margins of cork layer 25. In addition, however, thecork layer will extend up slightly above these exposed portions sothat articles having bases larger than the interrupted areas will, when placed on the upper surface of the tray, rest only on the .cork.

Another feature of the present invention .is that the resulting cork lined tray can be sterilized as .by steam .or hot water, and this sterilization can be repeated any number .of times without detracting from the trays appearance or usefulness. It can, therefore, be made completely sanitary notwithstanding the presence of the cork, and is highly suited for use in hospitals -or the like where the clatter of trays against each other or of articles sliding around on :thetrays, is to vbe avoided.

According to the present invention, the cork surface need not be applied to any specific portion of the tray. Thus instead .of having the cork on the upper surface as indicated .in Figures :1 and 2, the cork can be provided on the lower surface. Such a construction is illustratedin Fig. 4 .Where there is shown a tray similar to that of ,Figs. 1 and 2 but having on its lower surface four corkcushicning pads 125. These pads are partially irnbedded and partially permeated with resin as indicated in connection with the cork liner 25 \of Fig. 2, and also project below the .lower surfaceof the remainder of the tray. As a result the tray can be placed on a surface Without making .any appreciable noise, will hold itself in place resisting sliding movements, and if pushed hard enough to slide, .will slide withoutgeneratiug much noise. If desired cork layers can be applied to both the 'upper and lower surfaces .of the.tray,.and in fact-can'cover the entire tray.

The trays of the present invention are readily made from preforrns in the manner shown in the aboveidentified U. 'S. patent. As illustrated in Fig. 3, three different fibre-resin preforms "31, 32, 33 can be prepared as by suction'mo'lding from a slurry of pulp fibers and phenol-formaldehyde or phenolic resin suspended in water. Any fusible form of thermosetting resins may be used, .as for example melamine-, benzoguanimine-,

urea-formaldehyde, cross-linked polyesters, and the like. These preforms are preferably arranged so that the central one has a relatively high proportion of fibers, e. g. about 50 to 70% the balance being resin, while the preforms forming the outer face have a much lower fiber content, e. g. 20 to 50% the balance being resin. In assembling the preforms, the desired cork liner 25 suitably blanked out is juxtaposed with the fiber-resin preforms in the desired relative position. 25 is preferably from to about inch thick and can be shaved from the raw bark, and can also be made by molding together granulated cork and a binder such as a casein, or synthetic resins including thcrmosetting and thermoplastic resins such as phenolics, melamineformaldehyde condensation products, polyvinyl chlorides or the like. Only about to 20% binder is needed based on the weight of the cork.

After the preforms and cork liner are assembled they are then hot molded under a pressure of at least about 500 pounds per square inch at a temperature of from 250 to 350 F. This causes the resin in the fiber-resin preforms to melt and flow so that it distributes itself uniformly over the outer portions of the

preforms

32, 33 and also penetrates into the cork layer 25.

The total molding time required is about 3 to 5 minutes, but it is advisable to momentarily reduce the pressure to about 20 pounds per square inch about five seconds after the molding is begun to permit the release of gases that are generated. When the molding cycle is completed the mold can be opened, and the molded prodnot removed. Better results are obtained by bringing the preforms to uniform moisture content immediately before molding.

To assure that all fibrous parts of the tray are properly sheathed in a resin-rich layer, it is advisable to make the outer

fibrous preforms

32, 33 somewhat longer and wider than the inner preform. In this way, the extreme margins of the inner preform will become completely enveloped by the margins of the outer preforms, which will meet each other to form the desired continuous resin-rich edge.

The accurate placing of the cork liner against the assembled preforms to make the mold charge can be simplified by using an adhesive such as a sticky layer which can be of the same or different type of resin present in the preforms. A dab of such adhesive placed either on the lower surface of the cork liner 25 or the upper surface of the fiber resin liner 32 will permit the cork layer to be assembled in proper position and assure that it will remain in that position during any handling such as that required for insertion into the mold, as well as during the molding itself.

A feature of the invention is the fact that the upstanding nature of the cork layer enables the spacing of the layer margins from the margins of the trays upper article carrying surface. In other words the cork layer 25 does not reach as far as the tray corners where the side walls merge with the body of the tray. This makes the alignment of the cork layer less critical, and in addition, flat cork sheets can be used Without the complicating folding, wrinkling, and so forth, that would be introduced if the cork layer extended up the side walls.

The advantages of the present invention are obtained with trays molded from more or fewer preforms. By way of example, a single preform can be used so that the fiber-resin part of the tray is of substantially uniform composition throughout. On the other hand a large number of thin preforms can be used and laminated together by the molding. In this type of operation the preforms can be m rely sheets of paper (0.003 to 0.050 inch thick) that have been impregnated with the resin as from solution or suspension. These paper sheets and even the thicker preforms, need not be tray-shaped if the highest possible strength is not desired in the final tray. Perfectly flat preforms will be shaped by the mold- The cork sheet ing into the proper final contour but a gradual closing of the dies is necessary with precautions taken that the preforms bend properly without tearing. Preheating of the preforms to molding temperature is very helpful in this connection, apparently because it causes the resin in the preforms to flow much more readily.

A particularly efiective form of tray construction for use with the present invention is made in the manner described above in Figs. 1 and 2 with a central preform having 30% phenolic resin, by weight, and two outer preforms each with phenolic resin by weight, the balance of the central preform being unbleached sulfate pulp, and the balance of the two outer preforms being groundwood pulp. Other fibrous materials may also be used for the core or liners with satisfactory results. For

example, the core may be sulfite pulp, glass fibre, sisal.

fibers etc., and the liner may be hardwood kraft, hardwood sulfite, fine fibrous bark, etc.

Another very satisfactory tray construction has the same central preform as above, but with outer paper preforms 0.008 inch thick that carry a printed design and are impregnated with an unfilled melamine-formaldehyde resin.

In each case the cork liner becomes after molding partially imbedded and firmly bonded in place and extremely resistant to mechanical as well as chemical action.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof except as defined in the appended claims.

What is claimed is:

1. A method of making a tray which comprises forming a base from cellulose fiber and an uncured, thermosetting resin wherein the proportion of uncured resin relative to the fiber in the outer portion of the base is about 80% to 50% by weight, placing a substantially porous sheet of granulated cork having a resin binder therein against the surface of said outer portion of the base, the resin in said sheet of granulated cork being present in an amount not in excess of 20% by weight relative to the amount of cork, applying heat and pressure to the combination of the base and sheet until some of the thermosetting resin in the base flows between those cork granules of said sheet which lie below the upper surface of the sheet while maintaining the cork granules at said upper surface of the sheet free of said thermosetting resin, and curing said thermosetting resin to produce a substantially rigid base having a cork liner wherein a continuous phase of cured, thermosetting resin binds the cork liner to the base while the outer surface of said cork liner is substantially free of said cured, ,thermosetting resin.

2. The method of claim 1 wherein the thermosetting resin is at least one member of the group consisting of melamine, benzoguanimine, phenol-formaldehyde, ureaformaldehyde, and cross-linked polyester.

3. The method of claim 1 wherein the thermosetting resin is melamine.

4. The method of claim 1 wherein the resin is benzoguanimine.

5. The method of claim 1 wherein the resin is phenol-formaldehyde.

6. The method of claim 1 wherein the resin is urea-formaldehyde.

7. The method of claim 1 wherein the thermosetting resin is a cross-linked polyester.

8. A tray havinga bottom wall and an upstanding peripheral wall consisting essentially of cellulose fiber and a cured thermosetting resin, a cork liner comprising a sheet of cork bonded to the inner surface only of said bottom wall by a continuous phase of said thermosetting resin extending from said base into said cork liner and terminating short of the outer surface of said cork liner.

9. The tray of claim 8 wherein the thermosetting resin thermosetting thermosetting thermosetting is at least one member of the group consisting of melamine, beuzoguanimine, phenol-formaldehyde, urea-formaldehyde, and cross-linked polyesters.

10. The tray of claim 8 wherein the resin is a phenolic resin.

11. The tray of claim 8 wherein the resin is melamine.

12. The tray of claim 8 wherein the resin is benzoguanimine.

13. The tray of claim 8 wherein the resin is phenol-formaldehyde.

14. The tray of claim 8 wherein the resin is urea-formaldehyde.

15. The tray of claim 8 wherein the resin is a cross-linked polyester.

thermosetting thermosetting therrnosetting thermosettin g thermosetting thermosetting 16. The tray of claim 8 wherein said cork liner is partially imbedded in said inner surface of the bottom wall.

References Cited in the file of this patent UNITED STATES PATENTS Mason et al. May 22, 1883 Straus Jan. 24, 1893 Frederick Oct. 3, 1922 McManus Aug. 18, 1925 Clay June 6, 1933 Perry Feb. 9, 1937 Sawyer Feb. 24, 1942 Sawyer May 18, 1943 Dodge July 10, 1951 Knewstubb Feb. 26, 1952 Keller Dec. 8, 1953 FOREIGN PATENTS Great Britain 1910 Denmark Feb. 20, 1939

Claims

8. A TRAY HAVING A BOTTOM WALL AND AN UPSTANDING PERIPHERAL WALL CONSISTING ESSENTIALLY OF CULLULOSE FIBER AND A CURED THERMOSETTING RESIN, A CORK LINER COMPRISING A SHEET OF CORK BONDED TO THE INNER SURFACE ONLY OF SAID BOTTOM WALL BY A CONTINUOUS PHASE OF SAID THERMOSETTING RESIN EXTENDING FROM SAID BASE INTO SAID CORK LINER AND TERMINATING SHORT OF THE OUTER SURFACE OF SAID CORK LINER.