US2354916A - Method and apparatus for embossing plastic sheet material - Google Patents

Description

v. H. HURT 2,354,916

METHOD AND APPARATUS FOR EMBOSSING PLASTIC SHEET MATERIAL Aug. 1, 1944.

2 Sheets-Sheet 1 Filed Aug. 3, 1940 I F'- l INVENTOR. Ward/f m fla/ff MgW AT TORNEY Aug. 1, 1944. Y v.v H. HURT 2,354,916

, METHOD AND APPARATUS FOR EMBOSSING PLASTIC SHEET MATERIAL Filed Aug. 3, 1940 2 Sheets-Sheet 2 BY Ad: 3.

ATTORNEY Patented Aug. 1, 1944 UNITED STATES PATENT OFFICE 2,354,916 METHOD AND APPARATUS roa mossmo rmsrro SHEET rwrnamr.

Victor B. Hurt, Cranston, R. L, assignor to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application August 3,1940, Serial No. 350,931

6 Claims.

which has openings extending therethrough. A

previously known method of producing positive and negative impressions of the same design in opposite sides of plastic sheet material, particularly in heat-settable plastic sheet material such as vulcanizable sheet rubber, involves the use of a mold consisting of a pair of cooperating dies. One of the dies has the desired design formed thereinas a positiv impression and the other die .is so shaped as to correspond in negative depressed impression to the positive design. The rubber sheet to be embossed is held under pressure between the dies in register and the heat is applied to vulcanize the rubber sheet stock with the design permanently shaped therein. This process involves expensive diecutting operations and is not flexible in the sense that would permit the reproduction of a great number of designs .without undue cost. Principally because the die costs for this method of this type are expensive, the commonly employed method is to provide the design only on one set of the dies, namely, either the male or the female set, but not on both, at least not in cooperating design. As an example of this, some articles are molded with the design in the molds or female portion of the dies, while the core or male portion is generally smooth. In the case of bathing caps, the core or male portion contains the design while the mold or female portion is usually. smooth. Some caps, however, have a design in both portions but these designs are not related to each other.

According to the present invention a design may be reproduced in a sheet of rubber or other heat-settable plastic material in such manner that the design appears upon both faces of the sheet and the identity of the design is carefully maintained down to the smallest detail. The resulting article may be described as having a raised positive design upon one face and a complementary sunken negative design upon its opposite face. The invention dispenses with the expensive operations of forming two similar molds, one in positive and one in negative registration therewith. According to the invention, any fabric design may be accurately reproduced in a sheet of vulcanized rubber, the design being taken directly from the fabric itself, and intermediate operations being dispensed with.

According to the invention, a perforated base of hard-surfaced material, preferably but not necessarily inflexible, is connected on one surface with means for applying suction through the base. The other surface of the base may itself be formed with the desired design, or a sheet of designed material may be superimposed thereon. On the top of the designed sheet a sheet of uncured plastic material is placed, and a suction is applied through the base whereby the sheet is drawn or sucked against the designed material to conform with the surface configurations thereof. While the blank sheet remains in the deformed condition; it is cured or otherwise set to cause it to partake of the surface deformations which have been imparted to it. The invention is ,partlcularly applicable to the formation of rubber sheet material such as bathing suits or parts thereof or bathingcaps. It is desirable that the blank rubber sheet operated upon be of sufliciently thin rubber stock so that both surfaces of the rubber sheet are substantially identically deformed and the sharp outlines imparted to the surface of the rubber stock adjacent to the designed forming material are likewise imparted to the opposite surface of the rubber blank. Previous methods of embossing rubber sheeting wherein the interior of the mold was maintained at atmospheric pressure and the exterior of the blank rubber sheeting was subjected to increased positive pressure, either super-atmospheric or mechanical, have resulted in a blurring of the outlines of the design. The present suction or vacuum process insures accurate reproduction of the design which was hitherto considered impossible without complicated and expensive apparatus.

' I have discovered that with the normal sheet rubber stock employed in bathing cap manufacture, I may apply a very low vacuum, so that the differential in pressure between the interior and exterior of the apparatus may be as low as onehalf ounce per square inch in order to draw the stock material into the depressions of the designforming area.

The apparatus according to the present invention comprises an air-pervious base, a design form superimposed ,on one face of the base, and means for reducing the pressure from the other face of the base, Sealing means may, if found necessary, in particular instances, be provided to correspond with the outer edge of the rubber sheet to be embossed to confine the atmospheric pressure to the exterior surface of the sheet to be embossed while the interior surface thereof is maintained at sub-atmospheric pressure. As applied specifically to the manufacture of embossed bathing caps, for example, the apparatus may embody a perforated hollow bathing cap form, a sheet of air-pervious material superimposed thereon in laminated relationship and a design forming layer on the exterior, the design forming layer taking the shape of the positive or negative of the design to be reproduced. The design forming layer may, for example, comprise 'a mesh fabric or a composite sheet of material the rubber blank placed thereon, including a por- I tion of the assembly in cross-section;

Fig. 2 is a greatly enlarged cross-section of a portion of the assembly shown in Fig. 1 but with vacuum applied to show the rubber blank as conforming to the surface configuration of the design layer;

Fig. 3 is an elevation, with parts cut away and removed as in Fig. 1, showing an alternative embodiment of the invention;

Fig. 4 is a plan view of apparatus for producing designs in flat rubber sheet material with portions removed to show the laminated assemy:

Fig. 5 is a cross-section taken along the section line 5-5 of Fig. 4;

Fig. 6 is an enlarged cross-sectional detail similar to Fig. 2 showing the apparatus of Fig. 5 in operation with the suction applied;

Fig. '7 is a partially fragmentary view of an alternative embodiment for shaping a bathing p;

Fig. 8 is a view, partially in cross-section, of apparatus for embossing air-perviousmaterial; and

Fig. 9 is a perspective view showing the apparatus mounted for transfer into a vulcanizing receptacle.

The method and apparatus may both be clearly understood from a consideration of Fig. l. A hollow base or form I is sealed off at the open .end by a cap H which is pierced by a conduit l2 providing means for applying vacuum or suction to the interior of the form In. The form is preferably made of some light material such as aluminum, but may, if desired, be made of any rigid or even flexible material so long as the exterior surface thereof is relatively hard and so long as the material is of suflicient rigidity to maintain its.shape when suction is applied to the interior thereof during operation. Perforations I3 extend through the operating portions of the surface of the form it. A layer I I of air-pervious material, such as a fine mesh fabric surmounts the operating portion of the form and covers the overall area occupied by the perforations ii. The layer It is surmounted by a design forming layer l5. The design is formed by perforations or openings through the layer, comprising in the instance shown in- Fig. 1 the openings or spaces between the cords of an open mesh net having threads or cords l6 running in the lateral direction and cross threads l1 extending transversely thereof. The design forming layer l preferably terminates immediately above the terminal edge of the fabric layer It. The common terminal edge I 9 is abutted by a strip 20 of air-impervious material such as a strip of vulcanized rubber, which seals the thickness of the layers It and II and also may provide a raised portion 2| projecting farther from the base It than the exterior surface of the design forming layer l5. Instead of a separate strip 20, .the surface of the form [0 may be raised. A bathing cap blank 22 is shown placed in position over the design layer l5, with its open edge 23 slightly expanded and extending over the sealing strip 20. The cross section shown at the right hand side of Fig. l'illustrates the apparatus ready to produce a design in the rubber blank 22, before vacuum has been applied to the interior of the form "I.

Fig. 2 shows in greatly enlarged detail a portion of the assembly after the air, or at least a substantial portion thereof has been withdrawn from the interior of the mold sufficient to suck the cap blank into the desired shape. The upstanding lateral cords iii are now surrounded on their exterior with portions 24 of the rubber blank which have partaken of the exact shape of those cords. The sharp outline 25 represents the inner section of the cord "0 when the coarse fabric I! has been reproduced both on the exterior and the interior of the bathing cap 22. line 26 representing the exterior surface of the fine mesh fabric I 4 has also been reproduced at least on the interior of the bathing'cap and to some extent as shown on the exterior. The pressure on the exterior surface of the bathing cap 22 is preferably normal atmospheric pressure as contrasted with the super-atmospheric or mechanical pressure applied by certain other methods of forming embossed designs on rubber, although externa1 fluid pressure may be applied as desired. The use of unaugmented pressure on this surface permits this surface, to partake of configurations or deformations or irregularities corresponding to those imparted to the interior surface without becoming flattened out as has been found -to be the case when considerably greater pressure is applied. It is preferable that the fabric layer ll be of fine mesh material which permits a relatively smooth surface to be imparted between the cords l6 and i1, so that the overall impression of the formed design is substantially identical to th design of the designforming layer I5.

The reduced pressure on the interior of the form I0 is maintained as by sealing oil the conduit I 2, during vulcanization. The entire assembly with the deformed bathing cap on the mold may thus be inserted together with other forms in any well known vulcanizing medium for the curing period.

It is to be understood that the vulcanization may take placeeither in hot air, hot water or other liquid or steam, or may be eifected by cold vulcanization, as desired. When the rubber sheet material is of suflicient thinness which is usually the, case in manufacturing rubber bathing attire the exertion of super atmospheric pressure on the exterior thereof has little or no efiect in causing the rubber to flow except to conform to the impression of the design.

Fig. 2 shows the raised portions 21 and the depressed portions 29 on the surface of a bathing cap, which, when compared with the design forming layer I5, is a sharp reproduction of that design.

Referring to Fig. 3, a hollow form or mold ll similar to the mold I0, is provided throughout its operating area with a multiplicity of minute perforations 3|. The design forming layer 32 in this instance may be a sheet of vulcanized rubber shaped to cover the perforations 3i and having large design forming opening 33, for example, ofv the shape of circular perforations 34 is drawn when suction is applied through a conduit 35 connected with the interior of the A Jagged form 30. The relative sizes and positions of the perforations 3| and 33 are such that each perforation 33 connects through at least one of the perforations 3| with the interior of the form 3|.

Furthermore, the perforations 3| are preferably so small that even when rubber of the bathing cap blank 34 is drawn by suction in contact 34. Sealing strips 35 and 33 are positioned along the edge of the cap holding area of the mold 33. A row of perforations may be provided be- 1 tween the sealing strips 3| and 36 so that a corrugated edge may be produced on the edge of the bathing cap.

If desired, a fabric layer similar to the layer l4 may be interposed between the exterior surface of the mold 30 and the interior of the design forming layer 32 in the embodiment shown in Fig. 3. If th perforations 3| are sufliciently small, this is not necessary. A further modification of this embodiment comprises forming the design as it appears in the layer 32 directly on the surface of, and through the thickness of operating portions of themold 30. Such a mold can readily be formed by electroplating a matrix onto the mold shown .in Fig. 3 and taking a negative impression of that mold, and drilling the perforations 34 through a negative impression to produce a unitary, as opposed to a laminated, design-forming hollow mold.

The embodiment shown in Figs. 4 and 5 is suitable for making designs on parts or portions of plastic sheet material, for example, bathing suit parts. An embossing assembly 43 has depressed suction applying areas 4|, each of these portions being generally shaped according to the place.

The assembly 40 comprises a solid sheet base 43 which may take the'form of a flat metal sheet. A conduit 44 extends through the base 43 and may be provided with a connection for suction applying means. On the surface of the base 43 opposite to that from which the conduit 44 extends is a sheet of wire mesh 45 to distribute the effect of suction applied through conduit 44. The provision of the open mesh wire sheet 4! permits pressure to be reduced substantially evenly throughout the area occupied thereby even though air is finally withdrawn from the base at a single point. The opposite face of the wire mesh 45 has superimposed thereon a fabric sheet 46 similar to the layer l4 of Fig. 1, for further distribution of the suction effect and also for providing a relatively smooth surface against which embossed portions of the rubber blanks 42 come in contact. This fabric may be surfacedesigned, woven or knitted. The fabric layer 46 is covered by a design-forming layer 41 having openings 43 into which the rubber blanks 42 may openings 4| therein to deflne the suction applying areas referred to above.

Theedges ofthebase43 asshowninFigs.4 and 5 extend beyond the superimposed layers and join mask layer 43 at 53. When the mask is formed of flexible air-impervious material, the edges thereof may be folded over the edges of the layers, 44 and 41 to meet the upper exposed edge surface of the base 4.3. The seal at the intersection iu'between the base 43 and the mask 43 may be effected by atmospheric pressure alone when suction is applied through the conduit 34- but preferably is augmented by a layer of adhesive. If desired, other clamping means may be used to insure that suction will be applied, not around the edge of the assembly 40 but only through the suction areas 4|.

The edges'of the areas 4| correspond 'to angles of intersections of flanges 5| of the blanks 42, as in- Fig. 6. These flanges are useful in trimming operations and also in providing an unembossed marginal surface for bathing suit parts which surfaces may be of advantage in finally assembling a complete bathing suit, for example, as smooth surfaces for the application of adhesives. As in the operation shown in Fig. 3 a rubber blank .42 in Fig. 6 is drawn into the suction areas 4| and also into the design openings 43 while suction is, applied. 'I'he'conduit 44 may be sealed while the pressure within the assembly is reduced or the vacuum connection may be retained during vulcanization through a flexible hose; and the entire assembly, like a tray, may be inserted into a shelf of a suitable vulcanizer, in the usual manner. As described above, vulcanization may take place in any well known mannermlf it is desired to impart the design of the wire mesh to the rubber knobs 52, produced by the deformation of therubber into the openings .48, the fabric layer 46 may be omitted. It is preferable, 'however, to include the fabric layer 46 in order to provide further even distribution of the suction to the underface surface of the blanks 42.

In Fig. 7, the design form layer or matrix 6..

is a negative of the design to be produced on a cap blank 6| superimposed thereon. The outer surface of the design layer 60, which may be a vulcanized rubber cap embossed as described above, has channels 62 representing negatives of an original mesh design. Between the channels are depressions 63 left from a fabric, as produced in the above described examples. Perforations 84 are formedflls by drilling through the matrix layer and the base 65. which as shown in the drawings is of a metallic bathing capform. While suction is applied in the herein described manner through a conduit 66, the rubber blank 6| is sucked down onto the negative so that its interior assumes a positive of the channels 62 and of the depressions 63. The cap blank is vulcanized while thus deformed and upon removal is turned inside out so that the ;flne impressions produced from the negative are clearly visible on the exterior of the cap. Perforations 64 may be placed more or less at random, but it is preferable that at least some of them communicate with the channels 82 so that air may be evenly withdrawn from between the matrix and the blank. The provision of communicating depressions 63 over the entire operating surface of the matrix also assistsin attaining close cooperation between the blank and the matrix by permitting travel of the air as it is withdrawn by the suction. Since the depressions 63 are the result of placing a fabric in contact with thematrix during formation they therefore communicate and assist in removing air to insure proper deformation of the cap blank.

Fig. 8 shows a metallic matrix III in which the negative design is shown to comprise channels II and depressions I2. These may be formed on the exterior of the combination base-matrix 10 by cutting, embossing, chasing, etching or other suitable means. Appropriate perforations ll are distributed throughout the operating surface of the matrix. In this instance, the rubber blank I3 is air-pervious and is distinguished. from the previous examples by perforations 14. In order tosuck the rubber blank 13 down against th matrix 10 a mask II of air-impervious sheet material is placed over the article I! to be embossed. The procedure is as above described for the permanent deformation of the blank 13. It is to be understood that this method of operating on a sheet of air-pervious material may be carried out inconnection with any of the previously described apparatus or blank material so long as sealing means are provided to cause the suction to pull the materials into close contact with the matrix assembly.

Referring to Fig. 9 apparatus is shown for vulcanizing rubber bathing caps while suction is applied. A vulcanizing box 80 has heat'ng coils or pipes ll secured along the interior wall thereof. A cover 8i for the heating box is hinged at 82 and carries a pair of upstanding brackets 83 adapted to hold the pipes 84 and 85. To one end of the pipe 84 a flexible suction hose 86 is connected by an elbow 81. The other end of the pipe 84 holds a swivel joint and elbow 88 from which depends a pipe 89 carrying an elbow 90. The upper end of the pipe 85 is sealed by a cap OI. is the same as described in connection with pipe 84, terminating at the lower end with an elbow 92. Between the elbows 90 and 92 is a connection pipe 83 having T-joints 94 supporting the conduits of bathing cap forms 95 to hold them in rigid relationship with the pipe 93. After a cap blank has been stretched over the form 95, suction is applied and held as above described while the cover BI is closed. As the cover closes the forms 95 retain their upright pos'tion since the center of gravity of the pipe 93 and connected parts is lower than that of the pipe 84 or 85. The cap forms are preferably retained upright since the necessary amount of suction is so low that part of the cap edge may by gravity fold away from the form when the form is inverted. After the desired vulcanizing per od, the cap forms are withdrawn from the vulcanizing box by opening the cover and the flnishedvulcanized caps are removed.

When operating with certain plastic materials, the material may be deformed in the cold by the present apparatus, and any desired curing or setting operations may be performed after removal of the material from the apparatus.

While the application of the invention" has been specifically described with reference to the production of embossed vulcanized rubber sheeting and thin articles, it is to be .understood that it may likewise be practised on any air-impervious plastic material which may be cured or set by heat or otherwise after being initially deformed to take animpression of the desired design. While certain present preferred embodiments of the invention have been shown and described it is to be understood that the invention may be otherwise practiced or embodied within Otherwise the structure held by the pipe 85 claim and desire to protect by Letters Patent is:

1. Apparatus for producing designs in flexible plastic sheet material which comprises a rigid perforate base, means for reducing fluid pressure on one side of said base, a sheet of foraminous material in contact with the other side of said base, a flexible shapingsheet in contact with said foraminous' sheet, said shaping sheet comprising a facsimile of the design to be produced and having open spaces extending therethrough so as to expose portions of said foraminous sheet.

2. Apparatus for forming a design in a rubber sheet comprising a base having a multiplicity of minute perforations therein, a sheet of designed material applied to one surface of said base, said designed material having openings therein, at

least one of said perforations communicating with each of said openings, means associated with the opposite surfaceof the base for applying suction to the assembly, and means for sealing the periphery of a sheet of rubber to be designed so as to prevent substantial dispelling of applied suction.

3. Apparatus for producing designs in a sheet of heat-settable. flexible material comprising a flat base, a sheet of foraminous material applied to said base, a sheet of designed material having openings extending therethrough to communicate with said foraminous material, a sheet of air impervious material superimposed. on said designed sheet and having at least one opening therein communicating with said designed sheet, the edges of said air impervious material being in air-sealing relationship with said base, and means for applying suction through said base to the assembly.

- 4. The method of making an embossed bathing cap which comprises applying to a perforate bathing cap form a sheet having a design perforated therethrough, applying a blank rubber bathing cap over said designed sheet, sealing the edges of said rubber bathing cap, applying suction to the interior of said form, and vulcanizing said cap while suction is maintained in the form.

5. Apparatus for producing designs on a rubber bathing cap which comprises a hollow bathing cap form, a perforate rubber sheet over said form in laminated relationship therewith, per-- forations extending through said form and being confined to the area of said perforate rubber ible sheet of plastic material which comprises the spirit thereof and within the scope. of the placing the sheet in contact with a member having a design including perforations extending through the member, supporting said member with an air pervious sheet, reducing the air pressure within said air pervioussheet while maintaining a greater air pressure against the exposed face of the plastic sheet to place it and the underlying sheets under compression to deform the plastic sheet and force portions thereof through the perforations and into intimate molding contact with said pervious sheet, and setting said plastic sheet in the deformedshape.

vision a. soar.

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