GB1574720A - Manufacture of moulded - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO THE MANUFACTURE OF MOULDED ARTICLES (71) We, DUNLOP LIMITED, a British Company of Dunlop House, Ryder Street, St. James's, London S.W.1, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the manufacture of moulded articles and in particular, though not exclusively, to the manufacture of articles from polymeric material.

In the manufacture of moulded articles, such as 'O'-rings, seals, and bushes, it is known to use hinged or "book"-type presses but difficulty is met in providing efficient and effective means by which mould members of the press may be brought together with the facing surfaces of the member substantially parallel, and with uniform pressure subsequently applied to the mould members when brought together. Apparatus using cam and roller means may prove effective when new but is prone to wear of the cams etc. and a corresponding loss of parallelism together with mould wear.

To avoid this difficulty an alternative practice is to use a conventional tie bar or stephead press in which mould members are moved together and apart whilst being continually maintained in a parallel relationship.

The operation of this apparatus is less affected by wear than a hinged or book-type press but is less easy to operate. Difficulty is experienced in removing moulded articles and cleaning any residual material from mould members, especially when it is desired to perform these operations automatically.

One object of the present invention is to provide improved apparatus for the manufacture of moulded articles.

According to one aspect of the present invention apparatus for the manufacture of moulded articles comprises two press platens arranged to be relatively movable towards each other and apart with the platens maintained substantially parallel relative to each other, and two mould members arranged to define a mould cavity therebetween, the two mould members being operably connected to the press platens and locatable therebetween to permit compression of material in the mould cavity and being angularly movable relative to each other about an axis parallel to a plane containing a facing surface of at least one of the mould members to permit angular separation of the mould members.

Preferably the press platens are arranged to be movable also in a direction substantially perpendicular to the direction of separation of the platens so that they may be moved clear of the mould members. Full opening of the mould members with an angular movement is thereby permitted without requiring wide separation of the platens.

Support means may be provided to support the mould members both when clear of the platens and when situated between the platens prior to pressure being applied to the mould members by the platens.

Alternatively the press platens may be arranged substantially stationary in a direction perpendicular to the direction of separation of the mould members and the mould members moved to be inserted or withdrawn from between the press platens.

In a further alternative arrangement the press platens may be arranged to be capable of separating sufficiently to allow separation and angular opening of the mould members whilst located between the press platens.

Preferably when the press platens and mould members are arranged to be movable relative to each other in a direction substantially perpendicular to the direction of separation of the platens means is provided for angularly opening the mould members simultaneously with said relative movement.

Preferably the means comprises a mechanical linkage which opens and closes the mould members substantially simultaneously with relative movement of the platens and mould members apart and towards each other respectively. Alternatively the means may comprise, for example, an hydraulically operated piston and cylinder arrangement, or a cam mechanism.

Preferably angular movement of the mould members is obtained by hinge means but alternatively may be obtained by cam or guide means such as arcuate slots engaged by projections associated with one of the mould members. Where angular movement is by hinge means, the hinge means may comprise, for example, pins arranged to engage slots such that final closing or initial opening movement of the mould members is in a direction substantially perpendicular to facing surfaces of the mould members with the facing surfaces remaining substantially parallel. In addition to assisting in uniformly compressing material in the mould, the aforementioned parallel movement reduces mould wear as compared with a hinged mould in which relative movement between the mould members is angular.

The mould members may be arranged such that a first mould member, a lower mould member, remains in a generally horizontal plane whilst a second, upper mould member moves angularly towards a vertical position readily to permit removal of moulded articles and cleaning of the mould faces, and this is particularly advantageous when removal of moulded articles, cleaning and charging of the mould with raw material are performed manually. Alternatively, however, the first mould member may be disposed at any angle to the horizontal and may be arranged to vary in angular disposition during relative movement between the press platens and mould members. In this case the second mould member may be arranged to maintain a constant angular disposition relative to the vertical, or both mould members may be arranged to vary in angular disposition.

The invention also relates to moulded articles manufactured using apparatus in accordance with the present invention.

One embodiment of the invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation, part in section, of apparatus in accordance with the present invention in an open position; Figure 2 is a similar view to that of Figure 1 showing the apparatus in a closed position; Figure 3 is a detail plane view of part of support means shown in Figures 1 and 2; Figure 4 is a detail side elevation view of part of the linkage shown in Fig ures 1 and 2, and Figure 5 is a detailed sectional elevation view of the apparatus shown in Figures 1 and 2 Apparatus for the manufacture of moulded articles comprises a supporting framework 10 (see Figure 1 of the accompanying drawings) provided with support means in the form of a crade 11 for supporting a first, lower mould member 12.

The cradle 11 (see Figure 3 of the accompanying drawings) is in the form of a substantially horizontal plate formed with a central rectangular aperture and the mould member is formed with shoulders (not shown) in the region of two of its opposite edges so that it may be freely supported by side portions 13 of the cradle whilst located in a horizontal plane by the cradle.

A second, upper mould member 14 is supported by a mould plate 15 hinged at one end 16 by means of a pin 17 engaging a vertical slot 18 formed in a vertically projecting portion 19 of the cradle 11. The second mould member 14 is formed with ribs (not shown) at two opposite edges and these engage with channels provided on the mould plate 15 so that the mould member 14 may be slid into position in a direction parallel with the plane of the mould plate 15.

A tie-bar press assembly 20 comprising upper and lower press platens 21, 22 between which the mould members 12, 14 may be compressed is pivoted to the supporting framework 10 at its lower end by hinge means 23. The press assembly is therefore angularly movable and may be moved to a vertical position (see Figure 2) to surround the mould members by means of an hydraulic piston 24 pivotally secured at one end 25 to the supporting framework 10 and at the other end 26 to the upper end of the press assembly 20.

Also pivotally attached to the upper end of the press assembly 20 is a linkage mechanism 27 comprising first and second links 28 and 29 respectively. The linkage mechanism is pivotally connected to a portion of the mould plate 15 furthest from the hinge pin 17 which angularly connects the upper and lower mould members and thus causes the mould members to be opened and closed as the press assembly 20 is moved away'from and towards the vertical position respectively under the action of the hydraulic operating cylinder 24.

The upper platen 21 is secured to the tiebars 29 of the press assembly at a fixed distance from the lower hinge 23, the position of the upper platen being such that when the press assembly is in a vertical position and the mould members 12, 14 are closed together the upper platen lies close to that face of the upper mould member which projects through an aperture in the mould plate 15. The lower platen 22 of the press assembly is movable along the tie-bars, in parallel relationship relative to the upper platen under the action of a hydraulically operated actuating ram 30. With the press assembly in the afore-mentioned vertical position, as shown in Figure 2, the lower platen 22, is arranged such that initially it is only slightly below the lower surface of the lower mould member 12 as supported by the cradle 11. However, on actuation of the hydraulic ram 30 the lower press platen 22 lifts the lower mould member 12 relative to the cradle 11 and urges it against the upper mould member 14 which is restrained against upward vertical movement by the upper platen 21 of the press assembly.

Associated with the lower press platen is a hook 31 extending upwardly generally parallel with the tie-bars 29 and provided at its upper end with a hook portion 32. The hook portion lies above the pin 17 when the mould members are in a closed position and the press assembly is substantially vertical and, as described below, serves to asisist in the separation of the mould members before the linkage mechanism angularly moves the mould members relative to each other. Subsequent to the pressure being applied to the mould members and pressure being released by the ram 30 the lower platen 22 will move downwards to its initial position before being pivoted clear of the mould members by the hydraulic operating cylinder. The hook portion 32 is engageable with the pin 17 thereby to urge the lower mould member 12 down onto the cradle 11 and ensure that the two mould members 12, 14 do not remain stuck together due to any adhesive effect of the material being moulded. Pin 17 has associated therewith pull down bars 17a which assist in avoiding the jamming action that might otherwise result if downward movement of the mould member were effected only by the hook and pin acting on only one side of the mould member. Two bars 17a are provided at each side of mould member 12 as viewed in Figure 5 and are linked (by means not shown) to the pin 17 so as to result in guided movement of said mould member.

Final alignment of the mould members 12, 14 during closure is ensured by means of a conventional conical protrusion 33 provided on the lower mould member and arranged to locate with a corresponding depression in the upper mould member. However, to ensure initial alignment of the upper mould member with the lower mould member during closure lugs 34 (see Figure 4 of the accompanying drawings are provided at that end of the mould plate 15 furthest from the hinged end 16 and are arranged to engage with tapered slots 35 (see Figure 3; not shown on Figure 1) provided at the ends of the cradle 11.

A particular feature of the apparatus described specifically is that the lower mould member remains stationary in a horizontal direction and the press assembly is moved into position to compress the mould members. There is, therefore, substantially less possibility of disturbance of material, and/or any metal insert required in the product, situated in the mould cavity before compression as compared with an arrangement in which heavy mould members are moved into a press and material tends to be dislodged by any jolting movement as the mould members are aligned in the required position. This is a particular advantage when moulding articles from a material such as a polymeric material which has a low viscosity before curing. In a further alternative arrangement the press assemblies and associated mould members may be arranged in a row and indexed relative to a working area so that the required press assembly is brought to the working area.

In the embodiment of the invention described above the two mould members are permanently located adjacent an operator's work surface area 36 attached to the support frame 10, but in an alternative arrangement a plurality of press assemblies and associated mould members may be disposed in a carousel arrangement rotatable in a stepwise manner so that each press assembly and associated mould member may be presented successively to a working area.

Where a number of press assemblies and associated mould members are provided they may be interconnected such that one movement, such as the opening, of one assembly causes or initiates another movement in another assembly.

Alternatively or additionally the indexing movement of one or more press assemblies relative to a working area may be arranged to initiate opening etc. of a press assembly.

Furthermore each press assembly may be provided with its own storage hoppers for raw materials and moulded parts to facilitate efficient production, and other refinements such as automatic supply of raw materials and moulded parts may be utilised.

In apparatus in accordance with the present invention there is combined the advantage of mould members which open angularly and thereby allow ease of filling of mould cavity, cleaning, and removal of moulded article, along with the use of a parallel platen press which assists to ensure a low mould wear rate and uniform compression of material in the mould members.

Whilst the invention has been described specifically in relation to compression moulding apparatus it can also be applied to other apparatus such as injection moulding apparatus to facilitate removal of moulded parts and any mould inserts, as well as cleaning of mould parts.

Claims (11)

WHAT WE CLAIM IS:

1. Apparatus for the manufacture of moulded articles comprising two press platens arranged to be relatively movable towards each other and apart with the platens maintained substantially parallel relative to each other, and two mould members arranged to define a mould cavity therebetween, the two mould members being operably connected to the press platens and locatable therebetween to permit compression of material in the mould cavity and being angularly movable relative to each other about an axis parallel to a plane containing a facing surface of at least one of the mould members to permit angular separation of the mould members.

2. Apparatus according to claim 1 wherein the press platens are movable in a direction substantially perpendicular to the direction of separation of the platens.

3. Apparatus according to claim 1 or claim 2 wherein means is provided for opening the mould members angularly relative to one another simultaneously with movement of the press platens in a direction substantially perpendicular to the direction of separation of the platens.

4. Apparatus according to claim 3 wherein said means comprises a mechanical linkage and/or cam mechanism.

5. Apparatus according to claim 3 wherein said means comprises an hydraulically operated piston and cylinder arrangement.

6. Apparatus according to any one of the preceding claims wherein support means is provided to support at least one of the mould members prior to pressure being applied to the mould members by the platens.

7. Apparatus according to claim 1 wherein the press platens are capable of separating sufficiently to allow separation and angular opening of the mould members whilst located between the press platens.

8. Apparatus for the manufacture of moulded articles constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

9. A carousel press comprising a rotatable assembly of a plurality of apparatus in accordance with any one of the preceding claims.

10. A press according to claim 9 wherein the assembly is rotatable in a stepwise manner relative to a work station.

11. A press according to claim 10 wherein the work station supports at least one of the mould members when the press platens are separated.