US2631646A - Die for use in high-frequency heating - Google Patents

Description

March 17, 1953 J. P. GANNoN ETAL 2,631,645

DIE FOR USE IN HIGH-FREQUENCY HEATING Filed Feb. 16, 1951 H|GH FREQUENCY nlELEoTmc HEATER f2-LEVY- aff 53 34 3J 32 35 QZ Ti-Z./

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ATTORNEY ydie. 4Aduces a tear seal `which can be neatly trimmed Patented Mar. 17, 1953 DIE FOR USE'IN HIGH-FREQUENCY HEATING John P. Gannon, Bronx, Jacob Paintner, Hollis, and William Schnitzer, Bronx, N. Y.

Application February 16, 1951, Serial No. 211,354

8 Claims.

This invention relates to a novel die for sealing, embossing and scoring superimposed sheets or strips of flexible plastic material by means of high frequency currents and pneumatic pressure.

The sealing of thermoplastic sheets by dielectric heating through high frequency currents is, of course. well known and well understood. However, we have found that the dies employed for sealing and associated operations are complex and often restricted to single functions. Accordingly, such manufacturing processes are prolonged, more dies or like equipment are required, and the expense of an article is increased. With the foregoing in mind, we have devised a die which both seals and embosses superimposed flexible thermoplastic sheets along their edges by vhigh frequency currents and pressure, and at the same time, scores the edges to permit facilitated trimming thereof.

The embossing action of the improved die further creates a tooling effect such as is found `in hand crafted leather articles.

In fact, a plastic article formed pursuant to our invention exhibits a most pleasing and expensive appearing finish at its edges since it simulates hand tooling of leather as above described.

In a. preferred embodiment of the invention, an outer Wall of the die is made adjustable vertically, such wall defining the embossing width and constituting the scoring means for facilitating trimming of the finished article. Such adjustment insures that plastic sheets of different thicknesses may be effectively scored by the outer wall thereby enlarging the usefulness of the The outer Wall is formed so that it proresulting in a sharp, clean edge.

The die of this invention is further simple and rugged in construction, economical to manufacture, and highly efficient in use.

The invention will be further understood from the following description and drawings in which:

Fig. 1 is a part diagrammatic and part elevational view of a high frequency heating and sealing device, a pneumatic press and the improved die being shown in operative position on the press. Y

Fig. 2 is a cross-sectional View taken substantially along the lines 2-2 of Fig. l.

Fig. 3 is a view taken along the lines 3 3 of Fig. 1.

Fig. 4 is a fragmentary, enlarged view illus- Fig. 5 is a perspective view of a partly formed member made with the improved die.

Fig. 6 is a top plan view of the completely formed member.

Fig. 7 is a cross-sectional View taken along the lines 1 1 of Fig. 5.

Fig. 8 is a cross-sectional view taken along the lines 8-8 of Fig. 6.

In carrying out the invention, a high frequency dielectric heater it* of conventional construction is employed to generate high frequency currents. The die itself is carried by a conventional pneumatic press II having' the usual vertically movable plunger I2 which is generally operated by a foot pedal or the like. An insulating block I3 is secured to the bottom end of the plunger and it is to such insulating block that the die I4 is mounted by any conventional means. The machine further comprises a metal table or block I5 which is supported by insulating legs I5. The output of the dielectric heater I0 is applied through wires I 'I and IS to the die I4 and table I5 respectively. Thus, a high frequency circuit is adapted to be formed through the die and the table, the plastic sheets to be sealed to be disposed therebetween as will hereinafter be made clear.

Die I4 comprises a shallow, metallic boxlike device formed of brass or other suitable metal and having a bottom or base 2f), end walls 2i and 22 and side walls 23 and 24. Die lll is therefore adapted to act upon plastic sheets which are to be fused in the form of a rectangle. Such an article may find particular use in wallets or the like although it is evident that many other articles may be formed therefrom.

The base 20 is fastened to a metal plate 25 by screws 26, and the plate is fastened to the n insulating block I3 by screws or in any other suitable manner. The plate 25 is secured to block I3 with the boxlike die inverted so that its open top faces downward.

Surrounding the side and end walls is an endless thin adjustable outer wall 2l which serves as a scoring member. Wall 2'! may be likewise formed of brass or the like and it serves to impress a deep score in superimposed plastic sheets `so as to enable any run-over to be manually Astripped or torn off. The shape of this wall 27 is Such as to result in a clean, finished edge which is considered to be of great value insofar las the appearance of a finished article is conlcerned.

3 dated. Accordingly, wall 21 is formed with a plurality of slots 28 through which bolts 29 connect the plate to the die Walls. It will be evident, therefore, that when the bolts 29 are loosened, the outer wall 21 may be adjusted vertically so as to determine its degree of extension beyond the die wall edges. It will be evident from Fig. 4 that the extent to which the outer edge 30 of Wall 21 depends below the die wall should be determined by the thickness of the plastic sheets 3I and 32 which are to be fused and scored for tear sealing purposes. Edge 30 of scoring wall 21 has a slightly rounded form the roundness being on its outer surface and extending toward the die walls, as shown in Fig. 4, so that the material of the plastic sheets may be suitably scored Without being cut through. Fig. '1 illustrated the form of the plastic sheets 3| and 32 after having been acted upon by the composite die. It Will be noted that a deep score or depression is formed at 33 which permits the border or runover material 3Ia and 32a to be torn away from the remainder of the article. Score 33 will then serve as the finished edge. The die wall further produces a depression 34 which forms a bead 35 adjacent the edge of the article. It will be noted in Fig. 4 that the die walls are formed with an outer shoulder 36, such shoulder constituting a lateral spacing means between the plate upper or outer edge 30 and the edges of the die walls. It is this spacing that produced the embossed bead 35 as will be evident. If it is desired to make the bead wider, the shoulder 33 is made wider. Similarly, if it is desired to emboss the bead 35 as by a stitching design, it is merely necessary t form teeth along shoulder 36, and the impressions thereof will be formed on bead 35.

In order to prevent electrical arcing between the die I4 and the table I5, a pair of insulating sheets 40 which may be made of Bakelite or the like, may be placed directly on the table I5, and the plastic sheets to be fused are placed thereover.

rl`he above description having set forth the various elements of the die, and its use, the practice of the invention may be briefly summarized as follows:

The die I4 is first set in position on plate I3, scoring wall 21 having been vertically adjusted in accordance with the thickness of the plastic sheets 3I and 32 to be sealed and scored. As a general matter, wall 21 will always be positioned so that its upper edge 30 extends vertically outwardly or slightly below the upper edges of the walls of the die. The thin, flexible plastic sheets 3i and 32 are placed in position on the insulating sheets 43. It will be recognized that the die I4 forms one electrode in the high frequency circuit, and table or support I forms the other electrode. The high frequency heater I0 is suitably energized as the pneumatic press II is started in order to move its plunger I2 downwardly. It will be recognized, of course, that the energizing force may be applied at any time during the descent of the plunger. On the downward movement of the plunger, the die electrode is brought into contact with the sheets 3I and 32, and the high frequency currents pass through such plastic sheets, thereby rapidly raising the temperature of the material of such sheets. Scoring wall 21 first contacts the upper sheet as illustrated in Fig. 4, and continually downwardly, it not only fuses the edge but produces a tear seal as hereinabove described. Simultaneously, the upper edges of the die walls fuse the sheets in spaced relation to the scored edge to form the bead 35. The fused sheets are then removed from the press and the run-over portions IIa `and 32a appear as a peripheral web which can be manually trimmed or stripped off as illustrated in Fig. 5. This leaves a completely sealed member II which may be used in the fabrication of wallets or the like as above explained. The outer finish of article 4I may be givenk a pleasingly shiny appearance by employing a smooth hard surface on the Bakelite sheets 40 as will be evident to those skilled in the art.

It will be understood that the shape and outline of the die shown and described is for the purpose of illustration only and that the die may assume any desired shape depending upon the article being produced.

It has been found that a die constructed as above described is of pronounced utility in effecting the scoring or tear sealing of superimposed fused sheets so as to provide a neat looking, finished product at a. minimum of production costs while simulating a hand tooled article. If one type of article is to be made of different thicknesses oi plastic sheets, the Wall 21 may be vertically adjusted in and out over the die wall surfaces in order to accommodate itself to any such differences as above'set forth.

What is claimed is:

1. A die construction for use with a high friequency heating device and a press comprising a metallic device including at least one wall, and a thin outer member disposed adjacent thereto, the outer edge of said member being laterally spaced from said wall and vertically extending further outwardly than the upper edge of said wall.

2. A die construction according to claim 1 and wherein said outer edge of said member is rounded for producing a scored tear seal in plastic sheets which are fused by the die construction, said outer member being vertically adjustable on said wall to vary the vertically outward extension of its outer edge relative to the upper edge of the wall.

3. A die construction for use with a high frequency heating device and a press comprising a metallic, boxlike device including a bottom, side and end walls, a thin wall member fastened to the outer surfaces of said side and end walls with its outer edge rounded and disposed vertically outwardly of the outer edges of the side and end Walls, said walls forming sealing elements and said thin wall member forming ascoring element, said thin wall member outer edge being laterally spalced from the outer edges of the side and end was.

4. A die construction for use with a high frequency heating device comprising a metallic, boxlike device including a bottom, side and end walls and being open at its top, a metallic wall member fastened to the outer surfaces of said side and end walls and extending parallel therewith, the outer edge of said wall member being rounded and extending vertically outwardly past the outer edges of the side and end walls, a shoulder formed on said side and end walls and defining the outer edges of said walls, and said wall member outer edge being laterally spaced from said Wall outer edges by said shoulder.

5. A die construction according to claim 4 and wherein said wall member is formed with vertical slots and bolts operating through said slots for fastening said plate to said walls whereby said wall member may be vertically adjusted relative to said walls for determining the degree of vertical extension of its outer edge relative to the outer edges of said walls.

6. A die construction according to claim 5 and wherein said Wall member outer edge is rounded on its outer surface toward the outer edges of the walls.

7. A die construction for use with a high frequency heating device and a press comprising a metallic, box-like device including a plurality of Walls adapted to press upon and fuse sheets of thermoplastic material, a thin wall member fastened to the outer surfaces of said walls with its outer edge extending vertically outwardly of the outer edges of the walls, said walls and wall member forming a solid unitary structure.

8. A die construction for use with a high frequency heating device and a press comprising a metallic, box-like device including a plurality of walls adapted to press upon and fuse sheets of thermoplastic material, and a thin wall member 20 fastened to the outer surfaces of said walls with its outer edge vertically extending outwardly of the outer edges of the walls, said wall member having a rounded outer edge and being vertically adjustable in and out over the Wall outer surfaces.

JOHN P. GANNON. JACOB PAINTNER. WILLIAM ,SCHNITZER REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,478,771 Mafko Aug. 9, 1949 2,482,981 Kamrass Sept. 27, 1949 2,516,552 Clark et al. July 25, 1950 FOREIGN PATENTS Number Country Date 664,128 Great Britain Jan. 2, 1952

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