US3306813A

US3306813A - Pulp molding, method and apparatus

Info

Publication number: US3306813A
Application number: US375512A
Authority: US
Inventors: Richard F Reifers
Original assignee: Diamond International Corp
Current assignee: Diamond International Corp
Priority date: 1964-06-16
Filing date: 1964-06-16
Publication date: 1967-02-28
Anticipated expiration: 1984-02-28

Description

1967 R. F. REIFERS 3,306,813

PULP MOLDING METHOD AND APPARATUS Filed June 16, 1964 2 Sheets-Sheet 1 2O 2 g 5 INVENTOR [5752a F/gjjb RICHARD F REIFERS BY )MOf/(S ATTORNEY Feb. 28, 1967 R. F. REIFERS 3,306,813

PULP MOLDING METHOD AND APPARATUS Filed June 16, 1964 2 Sheets-Sheet 2 INVENTOR RICHARD F REI FERS ATTORNEY United States Fatent ()fifice 3,306,813 Patented Feb. 28, 1967 3,306,813 PULP MOLDING, METHOD AND APPARATUS Richard F. Reifers, New Canaan, Conn, assignor to Diamond International Corporation, a corporation of Delaware Filed June 16, 1964, Ser. No. 375,512 14 Claims. or. 162223) The present invention relates to pulp molding and more particularly to a method and apparatus for forming a pulp article free of flash and having a gripping peripheral edge, and the resulting article.

Flash tends to form on some areas of pulp molded articles, particularly the trailing edges thereof, because the stock tends to pile up on one part of the article or it sticks to the deckle ring. Until the present time, it has been necessary to utilize a separate deflashing step or operation in the formation of pulp molded articles. Articles formed without such a deflashing step have not been commercially suitable since they often have unattractive flash deposits extending from the peripheral edges thereof. No molding method known up to the prior time has uiltized any means of eliminating such flash except by carrying out some type of an additional deflashing step to either effect deflashing or an additional molding of the flash containing edge of the article. At any rate, some type of additional operation, step, or molding position has been necessary in the prior art, all of which increased the expense of forming pulp articles.

Many pulp molded articles, such as trays utilized in the packaging of food products, are used in conjunction with an overwrap film of some type, which film maintains the food product in position within the pulp molded tray. Most often such films comprise transparent plastic. Until the present time, it has proven diflicult and expensive to provide additional means to secure the overwrap film to the pulp molded tray.

It is therefore an object of the present invention to provide a pulp molded article and method and apparatus of manufacture obviating the difliculties of the prior art, such as those indicated above.

It is another object of the present invention to inexpensively provide a pulp molded article which is commercially attractive, and provide means for gripping an overwrap film.

It is another object of the present invention to provide a method and apparatus, in the manufacture of a highly satisfactory pulp molded article, which eliminate flash on the decorative edges and provide such article with exceptionally clean edges.

It is another object of the present invention to provide a means and method for obtaining a distinct and well defined decorative edge on a pulp molded article which is essentially flash free and which article is exceptionally simple to manufacture.

These and other objects and the nature and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial plan view showing an article produced in accordance with the present invention;

FIGS 1a and 1b are partial sectional views taken along lines la-la and lb-lb, respectively, of FIG. 1;

FIG. 2 is a sectional view taken through a mold in accordance with the present invention;

FIG. 3 is a partial sectional view on an expanded scale similar to FIG. 2;

FIG. 4 is a partial plan view of an edge forming device in accordance with the present invention;

FIG. 5 is a partial bottom view of the device of FIG. 4;

FIG. 6 is a sectional view taken along lines 6--6 of FIG. 5;

FIG. 7 is a sectional view taken along lines 77 of FIG. 5;

FIG. 8 is a sectional view taken along lines 8-8 of FIG. 5;

FIG. 9 is a partial plan view similar to that of FIG. 1; and

FIG. 9a is a partial sectional view taken along line 9a-9a of FIG. 9.

FIG. 1 shows, as one example of a pulp molded article formed in accordance with the present invention, a cake circle 10, having scalloped-like projections 12 extending from the peripheral end portion 14 thereof. In the cake circle 19, the extensions 12 serve to provide the cake circle with a pleasing decorative edge. When other articles are formed, such as trays, the extensions 12 also serve as friction gripping means about which an overwrap film can be more securely anchored than to a smooth peripheral edge. It is to be understood that, while a cake circle If) is shown, any pulp molded article, particularly a tray, can be formed having such or similar extensions 12 which will serve the above functions.

The scalloped-like extensions 12 of the cake circle 10, besides projecting outwardly from the peripheral end portion 14, may also extend at least in part. out of the plane of the cake circle such as shown in FIG. 1a, in a manner similar to the petals of a flower. As seen in FIG. 2, the article is not molded with the extension 12 projecting out of the plane, but such projection out of the plane (or flower petal effect) may be formed during removal of the article from the mold.

The extreme peripheral portions of the cake circle 10 are defined by an upper edge 16 and a lower edge 18. The upper edge 16, depending on the thickness of the article in relation to the extension forming portions of the mold, approaches a circle in configuration while the lower edge 18 comprises either the sole or the major defining edge of the extensions 12. Each extension 12 in addition has a sloped facing surface 20 which is essentially crescentshaped with a maximum dimensions shown in FIG. 1a and which facing surface 20 forms the hypotenuse of the triangle formed by the cross-section of such extension 12.

While the extensions 12 are shown in FIGS. 1, 1a, 9 and 9a to be essentially scalloped-like, in shape, it is understood that the invention is not limited to the production of extensions of this particular shape. Thus, as viewed in FIG. 1, the extensions 12 may project like saw teeth. The projections may also be of nonuniform size and spacing. In addition, unlike the extensions 12 shown, the extensions may be of uniform shape along the length and thus not vary continuously along their length;

The extensions 12 of the cake circle 10 of FIG. 9 are similar to the extensions 12 of FIG. 1 and have an upper edge 16, a lower edge 18 and a sloped facing surface 20. As seen by a comparison of FIGS. 1 and 9, however, the extensions 12 of FIG. 9 are smaller than the extensions 12 of FIG. 1 with the consequent result that edge 18' is shorter and each surface 20 smaller than the respective edge 18 and surface 20 of FIG. 1. Comparing FIG. 9a with FIG. 1a, it is seen that the cake circle 10 of FIG 9 does not have its extensions 12 projecting out of its plane in a flower petal effect.

FIG. 2 shows a mold 22 in accordance with the present invention for producing the cake circles 10 or 10'. The mold 22 comprises a backing plate 24 which has across its front a molding surface 26 which is permeable to the passage of air and water. Generally, and as well known in the art, such a permeable molding surface 26 will take the form of a molding screen. The mold 22 contains hollow portions 28 and holes 30 which pass from the hollow portions to the permeable molding surface. The mold is supported, generally for rotary passage through a pulp slurry containing molding vat, by a hollow spoke 32 such as is well known in the art. Means are provided (not shown) for both applying vacuum and positive fluid pressure through the hollow spoke 32, the hollow portions 28, and the holes 30 to the permeable molding surface.

During the molding operation, in a manner well known, the mold 22 is passed through a pulp slurry at which time vacuum is applied through the mold to effect deposition of the pulp deposit or 10'. Similarly, after completion of the deposition, the article 10 or 19' is removed from the mold by blowing air through the permeable molding surface 26 thereby forcing the deposit from the molding surface.

It is often desirable to use, in the construction of a mold 22, a peripheral deckle ring 34 which is held in place by screws 36. The purpose of the deckle ring 34 is to form a relatively smooth peripheral surface on the molded article 10. In addition, if the permeable molding surface 26 is a molding screen, the deckle ring 34 may be used to anchor the screen in place over the front surface of the backing plate 24. In the present invention, the deckle ring 34 is provided with undercut portions 38 about its periphery, which undercut portions effect the molding of the extensions 12 and 12'.

FIGS. 2 and 3 show the mold shortly after it has been removed from the pulp slurry after deposition of the deposit 10, but prior to removal thereof. As is seen, the cake circle 10, while on the mold, is essentially planar and at least the peripheral end portion 14 of the deposit lies in a single plane. In addition, it is seen that the extensions 12 lie beneath the undercut portions 38 of the deckle ring 34.

In accordance with the present invention, the pulp deposit 10 is removed by blowing air through the molding screen 26 to force the deposit 10 from the mold. Because the extensions 12 of the article extend a substantial distance beneath the undercut portions 38 of the deckle ring, the article cannot readily escape from the mold. However, sufiicient air pressure is used to force the article out of the mold regardless of the undercut portions 38; this causes the undercut portion 38 to exert a great deal of pressure on the extension 12 formed thereunder and as the article escapes from the mold the undercut portion provides a wiping action along the surface of the extension 12. This, in turn, causes the extensions 12 to deform in the manner shown in FIG. 1a. In addition, the article 10, immediately after removal from the mold, is essentially free of flash along its decorative edge.

FIG. 3 shows an expanded view of another mold in essentially the same position as that of FIG. 2. In the mold of FIG. 3, however, an opposing pressure mold 40 is used to smooth the upper surface of the article prior to the removal step.

The same procedure as described above is utilized in the formation of the article 10 further utilizing the same stock and the same processing variables. In this case, however, the extensions 12' extend only a short distance beneath the undercut portions 38 of the deckle ring. As in the formation of article 10, sufi'lcient air pressure is used to force the article out of the mold regardless of the undercut portions 38 and as the article escapes from the mold the extensions 12 are deformed or flexed in a manner similar to that shown in FIG. 1a. However, due to the small size of extensions 12, the amount of escape deformation is minimal and the extensions 12 return to their normal position as shown in FIG. 9a. This is due to the fact that the pulp fibers are molded in a correct position and have an elastic memory to that position to which they will return unless their elastic limit is exceeded during escape (such as in the removal of article 10). Whether the elastic limit is exceeded as the extension escapes the undercut portion of the deckle ring depends on, besides the depth of the undercut, a number of other variables, such as the wood fibers used in the stock, the fiber length, the density of the mat or deposit, the thickness of the mat, the processing variables, etc.; therefore there is no specific undercut depth which is a transition point on one side of which is produced the flower petal? extensions 12 and on the other side of which is produced the flat extensions 12. Like the extensions 12, however, the extensions 12 are also substantially free of flash along the decorative edge after removal of the article 10 from the mold. I

It is believed that the reason the articles produced are free of flash is that the over-hung portions of the deckle ring above the undercut portions tend to keep excess pulp or flash remote from the final true edge of the arti cle. hould any flash be formed at all, it would be in an area not normally seen by the customer.

FIGS. 4 to 8 show the details of construction of the deckle ring 34 used to form the scallopdike extensions 12 of the article of FIG. 1. Each undercut

portion

38, 38' and 38 are of uniform size and are spaced uniformly apart, with the starting point 42 of one undercut portion coinciding with the ending point of the previous undercut portion (although at the point 42 itself there is no undercut). The product configuration produced at point 42 lies between extensions 12 and corresponds to an end portion 14 as shown in FIG. 1b, and under ideal molding conditions the deposit will abut the vertical wall 37 of the deckle ring 34 as shown in FIG. 6 during the molding.

Under perfect molding conditions (quiet and thin stock), the wet stock deposit would approach the forma tion shown in FIGS. 68. In actuality, the stock at the upper edge 16 will tend to fall back somewhat from the

deckle walls

37 and 38 as the wet pulp deposit contracts from a thick mat to a thin mat as the deposit increases in density during application of vacuum after removal from the pulp slurry. In FIG. 7 it is seen that an undercut portion 38 is intermediate in size as it continuously varies in size along its length growing to a maximum at the lo= cation through which section line 88 is taken as shown in FIG. 8. While the cross-section of the undercut varies in size along its length, it nevertheless retains its triangu= lar cross-section. The deckle ring edge 48, which is com-- plimentary to the product edge 18, thus varies continu-- ously in position with regard to the inner peripheral wall 37 of the deckle ring, which is circular, and which is com plimentary to the upper edge 16 of the product.

As seen in FIGS. 6, 7 and 8, as well as FIGS. la and 1b, the upper peripheral edge 16 of the article 10 will always be circular so long as the thickness of the article is at least as great as the maximum height of the undercut portion 38 shown in FIG. 8. If, however, a thinner article is produced, then the upper peripheral edge 16 of the article will also oscillate in a manner similar to the lower peripheral edge 18 except that its variations will not be as great.

By carrying out the teachings of the present invention, it has been found that the pulp molded articles immediately after removal from the mold are without the flash which is usually present around the decorative peripheral edges of most molded pulp articles. In addition, the scallop-like edges produced, besides providing an attractive and decorative package, are also extremely useful in anohoring overwrapping films.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and therefore the invention is not intended to be limited to What is shown in the drawings and described and claimed in the specification, but only as set forth in the appended claims.

What is claimed is:

1. In a method of pulp molding comprising contacting a molding surface with a pulp slurry, depositing the pulp on the molding surface, removing the deposit and mold from the slurry, and removing the deposit from the mold, the improvement comprising depositing a portion of pulp in a plurality of undercut positions of said mold at peripheral sections of said deposit during the deposition to form a plurality of projections and removing the deposit from the mold by applying differential pressure to said deposit to deform said projections at said peripheral sections and to force said projections at said peripheral sections out of said undercut portions and provide an edge essentially free of flash.

2. A method in accordance with claim 1 wherein said diiferential pressure to effect deposition is provided by applying vacuum from the mold interior, and said differential pressure to remove the deposit from the mold is effected by applying positive air pressure from the mold interior. t

3. A method in accordance with claim 1 wherein said undercut positions are shallow so that said deformation is temporary and the elastic memory of said peripheral sections brings the edges back to their molded position.

4. A method in accordance with claim 1 wherein said undercut positions are deep so that said deformation is at least partially permanent.

5. In a mold for use in pulp molding comprising a permeable molding surface and a hollow interior adjacent said molding surface to transmit fluid pressure, the improvement comprising means to define the periphery of said article, said periphery defining means having a plurality of undercut portions into which the material to be molded deposits as discrete projections.

6. A mold in accordance with claim 5 wherein said periphery defining means comprises a deckle ring and said permeable molding surface comprises a forming screen.

7. A mold in accordance with claim 5 wherein said undercut portions are of uniform size and spacing.

8. A mold in accordance with claim 5 wherein said undercut portions are triangular in cross-section.

9. A mold in accordance with claim 5 wherein the cross-sectional configuration of each undercut portion continuously varies along its length.

10. A mold in accordance with claim 5 wherein the cross-sectional configuration of each undercut portion varies between a point of no undercut, a point of intermediate undercut, and a point of maximum undercut.

11. A mold in accordance with claim 10 wherein said undercut portions contact one another.

12. A mold in accordance with claim 5 wherein said undercut portions are complimentary to scallop-like projections.

13. A mold in accordance with claim 5 wherein said undercut portions are shallow to form an article with a planar edge.

14. A mold in accordance with claim 5 wherein said undercut portions are deep to form an article having a flower petal-like edge.

References Cited by the Examiner UNITED STATES PATENTS 2,384,958 9/1945 Pare 162-387 2,515,113 7/1950 Chaplin l624l1 2,780,401 2/1957 Stevens 229-2.5 2,841,054 7/1958 Muller et al. 162--387 2,903,063 9/1959 Crane 162411 3,001,582 9/1961 Kindseth et al. 162-4ll 3,033,434 5/1962 Carson 229--2.5 3,075,872 1/ 1963 Reifers 162223 3,123,519 3/1964 Reifers et al 162223 3,216,890 11/1965 Crabtree l62411 X 3,250,668 5/1966 Modersohn 162227 X FOREIGN PATENTS 571,117 2/1959 Canada.

DONALL H. SYLVESTER, Primary Examiner.

FRANKLIN T. GARRETT, D. M. BOCKENEK, I. H.

NEWSOME, Assistant Examiners.