GB2189183A

GB2189183A - Moulding plastic articles

Info

Publication number: GB2189183A
Application number: GB08709418A
Authority: GB
Inventors: Hiroshi Kouda; Sadao Moriyama
Original assignee: Ikeda Bussan Co Ltd
Current assignee: Ikeda Corp
Priority date: 1986-04-21
Filing date: 1987-04-21
Publication date: 1987-10-21
Anticipated expiration: 2007-04-21
Also published as: GB8709418D0; JPS62172019U; GB2189183B

Abstract

A plastic article such as a foamed polyurethane cushion is prepared using granular materials (24), such as crude sand or glass beads, as a shapable member for producing a so-called mold cavity (12). A lump of the granular materials in a mold is covered at its upper surface with a flexible film (26) and repeatedly pressed, e.g. by a shaping die (28) to form thereon a recess having a desired shape. Air is exhausted from the inside of the mold to fix the shape of the recessed lump and a liquid plastic material is poured into the recess and cured for a given time. Then, a film-covered article is removed from the recessed lump of granular materials, and the film is peeled off the article to provide the desired product. <IMAGE>

Description

SPECIFICATION Method and device for molding foamed plastic article BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates in general to a method and device for molding a plastic object, and more particularly to a method and device for molding a foamed polyurethane article which is used as a cushion pad of a seat.

2. Description of the Prior Art In molding a foamed polyurethane article used as a cushion pad of a seat, a method has been widely employed which comprises by steps, in general, preparing a mold having a mold cavity, heating the mold to a predetermined temperature, pouring a liquid urethane material mixed with a foaming agent into the mold cavity, placing a lid member on the mold to cause the material to cure and harden within the mold cavity, and removing the product, viz., the hardened foamed polyurethane article from the mold.

The molds used in this molding process are each machined to have a mold cavity of desired shape which corresponds to that of a finished article. This means that even in a trial manufacturing, various kinds of molds should be produced or machined by the number of types of articles which are newly designed.

As is known, producing a number of molds by machining is very expensive and thus causes increases in cost of the foamed products.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and mold for producing a foamed plastic article with a reduced cost.

According to the present invention, there is provided a method and device for producing a foamed plastic article, which uses a lump of granular materials as a member which is easily shapable to have a mold cavity of desired shape.

According to the present invention, there is provided a method for molding a plastic article, which method comprises by steps putting granular materials in a mold, laying a flexible film on a surface of a lump of the granular materials to provide a film-covered granular lump, pressing the lump to provide the same with a recess having a given shape, exhausting air from the inside of the mold to fix the shape of the recessed film-covered granular lump, pouring a liquid material of the plastic article into the recess of the lump and curing the same, removing a film-covered product of the plastic article from the recessed lump of granular materials upon hardening of the plastic material, and peeling the film off the product.

According to the present invention, there is further provided a device for molding a plastic article, which comprises a mold proper having a cavity formed therein, an easily shapeable lump of granular materials put in the cavity of the mold proper, a flexible film laid over a surface of the lump thereby to provide a filmcovered granular lump, a shaping die having a desired profile at its work portion, the shaping die being pressed against the film-covered granular lump to provide the same with a recess having a desired shape, and means for exhausting air from the film-covered granular lump thereby to fix the shape of the same.

BRIEF DESCRIPTION OF THE DRA WINGS Objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: Figures 1 to 4 are sectional views of a device of the present invention, respectively showing the steps of molding a foamed plastic article; Figure 5 is a sectional view of the foamed plastic article with a flexible film remaining on the same; and Figure 6 is a sectional view of another device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figs. 1 to 4, there are shown the steps of molding a foamed article "A" (see Fig. 5), which are employed in the method of the invention.

In the drawings, designated by numeral 10 is a mold which has a cavity 12 formed therein. The bottom wall of the mold 10 is formed with a hole 14 from which a tube 16 extends to a vacuum pump 18. An air filter 20 is fixed to an inlet of the tube 16, which is exposed to the bore 12 of the mold 10.

Thus, upon energization of the vacuum pump 18, filtered air is forced to flow in the tube 16 in the direction of the arrow 22 as is shown in Figs. 2 and 3.

The steps for producing the foamed article "A" will be described in detail in the following with reference to Figs. 1 to 4. The article "A" disclosed herein is a cushion member of a seat.

First, the mold 10 is heated to a predetermined temperature, and a predetermined amount of small particles 24, such as crude sand, iron sand, glass beads, plastics beads or the like, is put into the cavity 12 of the mold 10. If desired, a mixture of these particles may be used. The surface of the lump 24 of particles in the mold 10 is leveled by a suitable tool. Then, as is seen from Fig. 1, a flexible thermoplastic film 26, such as polyvinyl chloride film, polyethylene film or the like, is laid on the surface of the particle lump 24 with its peripheral portions seated on an up per edge of the mold 10. The upper surface of the film 26 has been coated with a suitable releasing agent for the purpose which will become apparent hereinafter.Then, as is seen from the same drawing, viz., Fig. 1, a shaping die 28 having a given shape is pressed against the film 26 and thus against the lump 24. This pressing work is repeated until the lump 24 covered with the film 26 has a recess of shape corresponding to that of the work portion of the shaping die 28. Then, with the shaping die 28 kept placed on the recessed lump 24, the vacuum pump 18 is energized, as is seen from Fig. 2. With this, air in the lump 24, viz., air in the space defined by the mold 10 and the film 26, is exhausted, so that the newly defined shape of the film-covered lump 24 is fixed because of reduction in fluidity of the particles 24. If desired, the air exhaustion may be carried out at the final stage of the pressing work of the shaping die 28. Then, the shaping die 28 is lifted.With this, a recess 26a having a given profile is created on the film-covered lump 24.

Then, as is seen from Fig. 3, with the vacuum pump 18 kept energized, a liquid material 30 for foamed plastics, such as liquid material for foamed polyurethane or the like, is poured into the recess 26a by a given amount. Then, as is seen from Fig. 4, a lid 32 is placed on the mold 10 and the vacuum pump 18 is stopped. Thus, thereafter, curing of the material 30 is carried out with an aid of heat possessed by the mold 10. Although not shown in the drawings, a suitable clamping device is arranged to hold the mold 10 and the lid 32 together in order to counter against the pressure generated during the curing of the material 30. The lower surface, viz., the surface contacting with the material 30, of the lid 32 has been coated with a suitable releasing agent.

After a given time during which the material 30 has cured sufficiently, the lid 32 is removed from the mold 10. Due to the releasing agent applied thereto, the lid 32 is smoothly released from the cured foamed plastic body 30'. Then, the foamed article covered with the film 26 (see Fig. 5) is removed from the recessed lump 24 and then the film 26 is peeled off the foamed article "A". With these steps, the product "A" is provided.

Referring to Fig. 6, there is shown another mold 100 which comprises two halves 10A and 10B which are substantially the same in construction and connectable with each other to define therebetween an enclosed chamber as is seen from the drawing.

That is, each half 10A or 10B has a bore 12A or 12B formed therein. The side wall of each half is formed with a hole 14A and 14B from which a tube 16A or 16B extends to a vacuum pump 18A or 18B. An air filter 20A or 20B is fixed to each tube 16A or 18B. It is to be noted that before molding, the two halves 10A and 10B are kept disassembled and horizontally laid on suitable platens.

The steps for producing a film-covered foamed article "B" by using the mold 100 will be described in the following.

Similar to the above-mentioned case, the two halves 10A and 10B are preheated to a suitable temperature. A predetermined amount of small particles is put in each half 10A or 10B of the mold 100, and a flexible thermoplastic film 26A or 268 is laid on a levelled surface of the lump of particles 24A or 24B.

Then, a shaping die is pressed repeatedly against the lump 24A or 24B to provide the same with a recess having a given shape. As is seen from Fig. 6, the resesses of the two lumps 24A and 248 are different in shape.

Then, the two vacuum pumps 18A and 18B are energized to exhaust air from the lumps 24A and 248 thereby to fix the shapes of the same.

Then, with the vacuum pumps 18A and 18B kept energized, the two halves 10A and 10B are coupled together, as is seen from Fig. 6, leaving therebetween a clearance 36 which leads to the merged recesses of the lumps 24A and 248. It is thus to be appreciated that the clearance 36 is defined between the films 26A and 268 of the respective lumps 24A and 24B. A seal strap 38 is wound around the coupled halves 10A and 10B in a manner to sealingly cover the clearance 36. The strap 38 is formed with several vent holes 40.

A clamping device 42 then holds the coupled halves 10A and 10B together. Then, with the vacuum pumps 18A and 18B kept energized, a liquid material 30 is poured through one of the vent holes 40 and the clearance 36 into the merged recesses.

After a given time during which the material 30 has cured sufficiently, the vacuum pumps 18A and 18B are stopped and the halves 10A and 10B are disassembled, and then, the film-covered foamed article is removed from the mold 100. Then, the films 26A and 268 are peeled off the foamed article "B". The unsightly portions which would extend radially outwardly from the formed article proper are cut to finish the article "B". With these steps, the product "B" is provided.

Claims

1. A method of molding a plastic article, comprising by steps: (a) putting granular materials in a mold; (b) laying a flexible film on a surface of a lump of the granular materials to provide a film-covered granular lump; (c) pressing the lump to provide the same with a recess having a given shape; (d) exhausting air from the inside of the mold to fix the shape of the recessed filmcovered granular lump; (e) pouring a liquid material for the plastic article into the recess of the lump and curing the same; (f) removing a film-covered product of the plastic article from the recessed lump of granular materials upon hardening of the plastic material; and (g) peeling the film off the product.

2. A method as claimed in Claim 1, in which before the step (a), said mold is heated to a predetermined temperature.

3. A method as claimed in Claim 2, in which said granular materials are small particles, which are selected from a group consisting of crude sand, iron sand, glass beads and plastic beads.

4. A method as claimed in Claim 3, in which, before the step (b), the surface of the lump of the granular materials in the mold is levelled.

5. A method as claimed in Claim 1, in which said flexible film is coated at its one surface contacting the surface of the lump of the granular materials with a surface lubricant.

6. A method as claimed in Claim 1, in which the step (c) is repeated until the filmcovered granular lump has a recess which has a desired shape.

7. A method as claimed in Claim 6, in which the step (c) is carried out by a shaping die which has a work portion of a shape corresponding to that of the recess formed on the film-covered granular lump.

8. A method as claimed in Claim 1, in which, after the step (e), a lid is placed on the mold.

9. A method as claimed in Claim 8, in which the lid and the mold are coupled together by a clamping means in order to counter against pressure generated during the curing of the plastic material.

10. A method as claimed in Claim 8, in which said lid is coated at its one surface contacting the plastic material with a releasing agent.

11. A method of molding a plastic article, comprising by steps: (a) preparing two molds which are connectable with each other to define therebetween an enclosed cavity; (b) putting granular materials in each mold; (c) laying a flexible film on a surface of a lump of the granular materials in each mold thereby to provide a film-covered granular lump for each mold; (d) pressing each lump to provide the same with a recess having a given shape; (e) exhausting air from the inside of each mold to fix the shape of the recessed filmcovered granular lump in each mold; (f) coupling the two molds together in a manner to define a desired mold cavity by the recesses of the film-covered granular lumps; (g) pouring a liquid material of the plastic article into the mold cavity and curing the same;; (h) uncoupling the two molds for removing a film-covered product of the plastic article from the molds upon hardening of the plastic material; and (i) peeling the films off the product.

12. A method as claimed in Claim 11, in which said granular materials are small particles, which are selected from a group consisting of crude sand, iron sand, glass beads and plastic beads.

13. A method as claimed in Claim 12, in which the step (d) is repeated until the filmcovered granular lump has a recess having a desire shape.

14. A method as claimed in Claim 13, in which the recesses of the film-covered granular lumps are different in shape.

15. A method as claimed in Claim 14, in which the step (f) is carried out while carrying on the air exhaustion.

16. A method as claimed in Claim 15, in which the step (f) is carried out by a clamping means in order to counter against pressure generated during curing of the plastic material.

17. A device for molding a plastic article, comprising: a mold proper having a cavity formed therein; an easily shapable lump of granular materials put in the cavity of said mold proper; a flexible film laid over a surface of said lump thereby to provide a film-covered granular lump; a shaping die having a desired profile at its work portion, said shaping die being pressed against said film-covered granular lump to provide the same with a recess having a desired shape; and means for exhausting air from said film-covered granular lump thereby to fix the shape of the same.

18. A device as claimed in Claim 1, further comprising means for heating said mold proper at a given temperature.

19. A device as claimed in Claim 2, in which said granular materials are small particles, which are selected from a group consisting of crude sand, iron sand, glass beads and plastic beads.

20. A device as claimed in Claim 1, further comprising a lid member which is placed on said mold proper.

21. A device machine as claimed in Claim 1, in which said means comprises: a conduit having one open end exposed to said cavity of said mold proper; a vacuum pump connected to the other open end of said conduit; and a filter connected to said conduit to filter air flowing in the conduit.