Device for controlled application of a differential vacuum to a mould

Abstract: A device for the controlled application of a differential vacuum to the cavity (12) of a vaccum-mould (10) consists of one or more vacuum sources (201, 211, 301, 311). Each said vacuum source communicates with the cavity (12) by means of one or more vacuum-holes (202, 212, 302, 303, 312, 313). The mould may be provided with internal dividers (30, 31) and one of the vacuum-holes (302, 303, 312, 313) may enter the cavity (12) on either side of its respective divider (30, 31).

Description: This invention relates to a vacuum-mould having a device for the controlled application of a differential vacuum to the mould cavity, for vacuum-moulding of sheet material. The present invention will be described herein with particular reference to a vacuum-mould for the production of "trim-covered" components, but is not to be construed as being limited thereto. By "trim-covered components" is meant articles comprising a resilient core having an integral cover of a fabric or other sheet material. A commonly-encountered example of such an article is a seating component (e g for use in a motor vehicle). Articles of this type frequently have a relief-patterned configuration (for example moulded grooves) and the integral cover may consist of a multilayer laminate or of several pieces of different materials sewn together in sheet form. Conventionally, "trim-covered" articles are made by means of a vacuum-moulding process, in which the fabric or other sheet material which will form the cover of the article is laid over the mouth of the mould, a vacuum is applied to draw the fabric into contact with the mould cavity and the mould is filled with, for example, a foam-forming reaction mixture. Conventional vacuum-moulds include a single vacuum chamber, of large volume relative to the volume of the mould cavity, together with a series of through-holes (hereinafter described as vacuum-holes) extending between the mould cavity and the vacuum-chamber. When a cover sheet material such as a fabric is placed across the mouth of such a mould and a vacuum applied, the response of the sheet material is slow and cannot readily be controlled. This disadvantage is especially noticeable where the cover sheet material consists of more than one layer or of several pieces of different materials. The application of an uncontrolled vacuum to such a material can result in bow and skew and in the fabric becoming "stretched" or "bunched" or otherwise not uniformly positioned against the mould cavity surface. A proposal for shaping a stretchable sheet material by vacuum-moulding in a manner to provide uniform stretching of the material during moulding is described in US-A-4087224 which shows a vacuum-mould according to the preamble of claim 1. In that proposal, the mould cavity surface is provided by a shaped side of a large hollow mould box which is divided into two or more chambers of different gas pressures to provide a differential gas pressure via apertures (holes) through the box side and thereby to create a gas flow, or 'air cushion', between the sheet material and the cavity surface during moulding. The present invention provides a vacuum-mould which eliminates the need for a mould box or chamber and which produces moulded sheet material shaped accurately in conformity with a mould cavity surface comprising changes in direction such as corner depressions (forming projections in the moulded sheet material) and divider projections (forming grooves in the moulded sheet material). In accordance with the present invention, the vacuum-mould comprises vacuum sources in the form of ports incorporated within the casing structural wall of the mould cavity and communicating with the mould cavity by vacuum-holes. Furthermore, where there is a change in direction of the mould cavity surface, a port is located at a position within the mould cavity casing wall corresponding to that change in direction, thereby providing a vacuum source dedicated to that change in direction. In particular, according to the present invention there is provided a vacuum-mould for vacuum-moulding sheet material such as in the production of a trim-covered component, said mould having a device for application of a differential vacuum to the mould cavity, said device comprising a plurality of vacuum sources in communication with the mould cavity by means of vacuum-holes, characterised in that the device comprises vacuum sources in the form of vacuum ports, of small volume relative to the volume of the mould cavity, incorporated within the structural wall of the mould cavity casing, wherein a vacuum-port is located at a position in the mould cavity casing wall corresponding to a change in direction of the surface of the mould cavity and wherein at least one vacuum-hole directly communicates the vacuum-port with the mould cavity at a change in direction of the surface of the mould cavity. The present invention further provides a method of making a moulded sheet material or trim-covered component, for instance a seating component, e g for use in a motor vehicle, by a vacuum-moulding process comprising laying a sheet material (such as material to provide the cover of a trim-covered component) over the mouth of a vacuum-mould described in the immediately-preceding paragraph and applying a controlled differential vacuum via the vacuum-holes to draw the sheet material into conformity with the mould cavity surface. In one embodiment of the present invention, each said vacuum-port may constitute part of a multi-directional vacuum manifold. In a preferred embodiment, a vacuum-port with communicating vacuum-hole(s) is located at a position corresponding to each change in direction of the surface of the mould cavity, for example at each corner and, if present, at each internal divider. It is especially convenient for a pair of vacuum-holes to extend from the vacuum-port adjacent a divider, one member of each pair of holes entering the mould cavity on each side of its corresponding divider. At least one of the vacuum-ports may be supplied with a differential vacuum relative to other vacuum-ports. The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawings. In the drawings (wherein like numerals denote like parts): Figure 1 is a schematic sectional view of a mould including a device according to the present invention; Figure 2 is an enlarged view of the "circled" portion of Figure 1. Referring to the drawings, a vacuum-mould 10 includes a mould casing 11 and a cavity 12. The cavity as shown includes two corners 20 and 21 and two internal dividers 30 and 31. Vacuum-ports 201 and 211 are incorporated within the structural wall of the mould casing 11, at positions corresponding to the corners 20 and 21 respectively. Communication between ports 201 and 211 and the mould cavity 12 is by means of vacuum-holes 202 and 212 respectively. Vacuum-ports 301 and 311 are similarly incorporated within the structural wall of the mould casing 11, at positions corresponding to the dividers 30 and 31 respectively. Each of the ports 301 and 311 communicates with the mould cavity 12 by means of a pair of vacuum-holes 302,303 and 312,313 respectively, one member of each pair of holes entering the cavity on each side of its corresponding divider.

Claims: Vacuum-mould for vacuum-moulding sheet material such as in the production of a trim-covered component, said mould having a device for application of a differential vacuum to the mould cavity (12), said device comprising a plurality of vacuum sources in communication with the mould cavity by means of vacuum-holes, characterised in that the device comprises vacuum sources in the form of vacuum-ports (201;211;301;311), of small volume relative to the volume of the mould cavity (12), incorporated within the structural wall of the mould cavity casing (11), wherein a vacuum-port (201;211;301;311) is located at a position in the mould cavity casing wall corresponding to a change in direction (20;21;30;31) of the surface of the mould cavity (12) and wherein at least one vacuum-hole (202;212;302;303;312;313) directly communicates the vacuum-port with the mould cavity at a change in direction of the surface of the mould cavity. Vacuum-mould according to Claim 1, in which a vacuum-hole (202;212) communicates a corner (20;21) change in direction of the mould cavity surface with the correspondingly located vacuum-port (201;211). Vacuum-mould according to Claim 1 or Claim 2, in which the mould cavity surface includes one or more internal dividers (30;31), and a vacuum-port (301;311) is located at a position corresponding to each of said dividers. Vacuum-mould according to Claim 3, in which said vacuum-port communicates with the mould cavity (12) by means of a pair of vacuum-holes (302,303;312,313) one member of each said pair of vacuum-holes entering the mould cavity on each side of its corresponding divider (30,31). Vacuum-mould according to any of the preceding Claims, in which a vacuum-port constitutes part of a multi-directional vacuum manifold. Vacuum-mould according to any of the preceding Claims, in which a vacuum-port is supplied with a controlled vacuum different to that supplied to another vacuum-port, whereby a controlled differential vacuum is applied to the mould cavity. Method of making a moulded sheet material by a vacuum-moulding process comprising laying the sheet material over the mouth of a vacuum-mould (10) defined in any of the preceding Claims and applying a controlled differential vacuum via the vacuum-holes to draw the sheet material into conformity with the mould cavity surface. Method of making a trim-covered component by a vacuum-moulding process comprising laying a cover sheet material over the mouth of a vacuum-mould (10) defined in any of Claims 1 to 6 and applying a controlled differential vacuum via the vacuum-holes to draw the sheet material into conformity with the mould cavity surface. Method according to Claim 8, in which, after the sheet material has been drawn into conformity with the mould cavity surface, a foam-forming reaction mixture is applied onto the moulded sheet material to form a resilient core of the trim-covered component. Method according to Claim 7, 8 or 9, in which the sheet material is a multilayer laminate or comprises several pieces of different materials.

Inventors: ROGERS DAVID MICHAEL, WILSON GEORGE SHEPHERD, ROGERS, DAVID MICHAEL, WILSON, GEORGE SHEPHERD
Applicants: DUNLOP LTD, DUNLOP LIMITED
Application year: 1991
Main classification: B29C51
IPC codes: B29C33, B29C51