GB2059331A

GB2059331A - Moulding and diecasting presses

Info

Publication number: GB2059331A
Application number: GB8031670A
Authority: GB
Original assignee: DANIELS ENG Ltd
Current assignee: DANIELS ENG Ltd
Priority date: 1979-10-02
Filing date: 1980-10-01
Publication date: 1981-04-23

Abstract

A moulding or diecasting press for the compression, transfer and/or injection moulding of polymeric materials or for the pressure die-casting of metals comprises fixed and movable press tables (2 and 4), a shroud formed in two parts (1 and 3) which are mounted for relatively slidable movement around at least one mould or die (5, 6) so as to be capable of defining, with a seal (8), a substantially closed chamber enclosing the or each such mould or die (5, 6), and means (9) to evacuate gas from said closed chamber. The two shroud parts (1, 3) each have walls defining substantially rectangular chambers, and are in telescopically sliding co-operation. <IMAGE>

Description

SPECIFICATION Moulding and diecasting presses This invention relates to moulding presses of the type used for the compression, transfer and/or injection moulding of polymeric materials and to presses of the type used for the pressure diecasting of metals.

Whilst these known presses and the moulds attached thereto are generally satisfactory, and operate efficiently, there is sometimes a tendency for the mouldings which are produced to the defective, or at least to fall short of the required standard, and this is attributable, under some circumstances, to the air or other gas which is trapped in the mould, during operation, after final closure thereof. One object of the present invention is to provide such a press with effective shrouding by which the shortcoming that has been discussed above can be eliminated, or at least very significantly reduced, without appreciably increasing the length of the moulding or casting cycle or the cost of the mouldings or castings.

According to the invention, there is provided a moulding or diecasting press of the type set forth, comprising fixed and movable press tables, a shroud formed in two parts which are mounted for relatively slidable movement around at least one mould or die so as to be capable of defining, with a seal provided between those two relatively slidable parts, a substantially closed chamber enclosing the or each such mould or die, and means operable at least partially to evacuate gas from said closed chamber when so desired.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a sectional elevation through a moulding press incorporating a two part shroud in accordance with the invention, the shroud being shown in a partially open position, Figure 2 is a plan view of the lower part of the shroud, and Figure 3 corresponds to Figure 2 but illustrates an alternative shroud construction.

Referring to the drawings, and firstly to Figure 1 thereof, that Figure shows a shroud, consisting of two main parts, an upper part 1 and a lower part 3, in a partially open position, the parts 1 and 3 being attached to fixed and moving press tables 2 and 4 respectively with corresponding half moulds 5 and 6 contained therein.

The upper shroud part 1 is attached to the fixed press table 2 by screws (not illustrated) and the upper half mould 5 is sealingly attached to a base plate la of the shroud part 1.

The lower shroud part 3 is attached to the hydraulically movable press table 4 by screws (not illustrated} and the lower half mould 6 is sealingly attached to a base plate 3e of the shroud part 3.

The lower shroud part 3 has a groove 7 machined around its inner surface and this groove houses a flexible seal 8 made in a heat resisting material which is capable of withstanding the highest temper aturesthat are likely to be encountered during any moulding operation. A commercially available elastomeric, but heat resistant, rubber material has proved to be suitable for this purpose. An internally screw-threaded connection 9 provides a coupling location for a pipe from a vacuum pump or other source of vacuum (not illustrated).

The upper shroud part 1 has an inwardly sloping taper 10 machined on its lower edge.

Referring now to Figure 2, that Figure shows in plan view the lower shroud part 3 which consists of four successively perpendicular side members 3a, 3b, 3c and 3d attached to the base plate 3e. The upper shroud part 1 is similarly constructed but is smaller in outside dimensions so that it can slide telescopically within the inner confines of the lower shroud part 3.The taper 10 on the other side members of the upper shroud part 1 gradually compresses the flexible seal 8 as the moulding press is closed and the lower shroud part 3 slides upwardly around the upper shroud part 1 and is arranged to provide a vacuum-tight seal so that at least partial evacuation of air or other gas from the closed chamber which is thus formed can be made thereby consequentially wholly or partly removing air or other gas from mould cavities 11 and 12 (defined between the abutting half moulds 5 and 6) during the moulding process.

Referring now to Figure 3, that Figure shows in plan view a lower shroud part 3 of alternative construction which consists of four successively perpendicular side members 3u, 3w, 3x and 3y joined together at their ends by four rounded corner or quadrant members 3v, all eight members 3u to 3y being sealingly attached to a base plate 3z. The upper shroud part (not illustrated) is similarly constructed, having quadrant-shaped corners, but is smaller in outside dimensions so that it can slide telescopically within the inner confines of the lower shroud part 3.The employment of the quadrantshaped corners that are embodied in the members 3v and in similar members in the upper shroud part (not shown), can result in a reduction in the rate of wear and in the incidence of consequent air leaks as compared with the embodiment of Figures 1 and 2 of the drawings where the upper and lower shroud parts 1 and 3 and the seal 8 each have four sharp 900 angular corners.

1. A moulding or diecasting press of the type set forth, comprising fixed and movable press tables, a shroud formed in two parts which are mounted for relatively slidable movement around at least one mould or die so as to be capable of defining, with a seal provided between those two relatively slidable parts, a substantially closed chamber enclosing the or each such mould or die, and means operable at least partially to evacuate gas from said closed chamber when so desired.

2. A press as claimed in claim 1, wherein said seal is formed from an elastomeric, but heat resistant, rubber material.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Moulding and diecasting presses This invention relates to moulding presses of the type used for the compression, transfer and/or injection moulding of polymeric materials and to presses of the type used for the pressure diecasting of metals. Whilst these known presses and the moulds attached thereto are generally satisfactory, and operate efficiently, there is sometimes a tendency for the mouldings which are produced to the defective, or at least to fall short of the required standard, and this is attributable, under some circumstances, to the air or other gas which is trapped in the mould, during operation, after final closure thereof. One object of the present invention is to provide such a press with effective shrouding by which the shortcoming that has been discussed above can be eliminated, or at least very significantly reduced, without appreciably increasing the length of the moulding or casting cycle or the cost of the mouldings or castings. According to the invention, there is provided a moulding or diecasting press of the type set forth, comprising fixed and movable press tables, a shroud formed in two parts which are mounted for relatively slidable movement around at least one mould or die so as to be capable of defining, with a seal provided between those two relatively slidable parts, a substantially closed chamber enclosing the or each such mould or die, and means operable at least partially to evacuate gas from said closed chamber when so desired. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a sectional elevation through a moulding press incorporating a two part shroud in accordance with the invention, the shroud being shown in a partially open position, Figure 2 is a plan view of the lower part of the shroud, and Figure 3 corresponds to Figure 2 but illustrates an alternative shroud construction. Referring to the drawings, and firstly to Figure 1 thereof, that Figure shows a shroud, consisting of two main parts, an upper part 1 and a lower part 3, in a partially open position, the parts 1 and 3 being attached to fixed and moving press tables 2 and 4 respectively with corresponding half moulds 5 and 6 contained therein. The upper shroud part 1 is attached to the fixed press table 2 by screws (not illustrated) and the upper half mould 5 is sealingly attached to a base plate la of the shroud part 1. The lower shroud part 3 is attached to the hydraulically movable press table 4 by screws (not illustrated} and the lower half mould 6 is sealingly attached to a base plate 3e of the shroud part 3. The lower shroud part 3 has a groove 7 machined around its inner surface and this groove houses a flexible seal 8 made in a heat resisting material which is capable of withstanding the highest temper aturesthat are likely to be encountered during any moulding operation. A commercially available elastomeric, but heat resistant, rubber material has proved to be suitable for this purpose. An internally screw-threaded connection 9 provides a coupling location for a pipe from a vacuum pump or other source of vacuum (not illustrated). The upper shroud part 1 has an inwardly sloping taper 10 machined on its lower edge. Referring now to Figure 2, that Figure shows in plan view the lower shroud part 3 which consists of four successively perpendicular side members 3a, 3b, 3c and 3d attached to the base plate 3e. The upper shroud part 1 is similarly constructed but is smaller in outside dimensions so that it can slide telescopically within the inner confines of the lower shroud part 3.The taper 10 on the other side members of the upper shroud part 1 gradually compresses the flexible seal 8 as the moulding press is closed and the lower shroud part 3 slides upwardly around the upper shroud part 1 and is arranged to provide a vacuum-tight seal so that at least partial evacuation of air or other gas from the closed chamber which is thus formed can be made thereby consequentially wholly or partly removing air or other gas from mould cavities 11 and 12 (defined between the abutting half moulds 5 and 6) during the moulding process. Referring now to Figure 3, that Figure shows in plan view a lower shroud part 3 of alternative construction which consists of four successively perpendicular side members 3u, 3w, 3x and 3y joined together at their ends by four rounded corner or quadrant members 3v, all eight members 3u to 3y being sealingly attached to a base plate 3z. The upper shroud part (not illustrated) is similarly constructed, having quadrant-shaped corners, but is smaller in outside dimensions so that it can slide telescopically within the inner confines of the lower shroud part 3.The employment of the quadrantshaped corners that are embodied in the members 3v and in similar members in the upper shroud part (not shown), can result in a reduction in the rate of wear and in the incidence of consequent air leaks as compared with the embodiment of Figures 1 and 2 of the drawings where the upper and lower shroud parts 1 and 3 and the seal 8 each have four sharp 900 angular corners. CLAIMS

3. A press as claimed in claim 1 or 2, wherein said two shroud parts are both of substantially rectangular shape, the dimensions of one of them being larger than those of the other whereby said other part can slide telescopically within said one part.

4. A press as claimed in claim 3, wherein the four corners of each substantially rectangular shroud part are sharp 900 angular corners.

5. A press as claimed in claim 3, wherein the four corners of each substantially rectangular shroud part are rounded or quadrant-shaped corners.

6. A press as claimed in any one of claims 3 to 5, wherein said seal is located in a groove formed in the internal surface of the wall of said one or larger part of the two part shroud.

7. A press as claimed in claim 6, wherein an edge region of said other or smaller shroud part is formed with an inwardly sloping taper for gradually compressing co-operation with said seal during closure of the press.

8. A press as claimed in any preceding claim, wherein the means operble at least partially to evacuate gas from said closed chamber when so desired comprises a vacuum pump that is coupled by a pipe to at least one screw-threaded connection in a wall of on of said two shroud parts.

9. A press as claimed in claim 8 when read as appendant to claim 3, wherein the or each screwthreaded connection is in the form of an internally screw-threaded hole in a wall of said one or larger of the two parts of the shroud.

10. A moulding ordiecasting press of the type set forth, substantially as hereinbefore described with reference to either of the embodiments that are illustrated in the accompanying drawings.