GB2222799A

GB2222799A - Guiding a press ram within a press enclosing housing

Info

Publication number: GB2222799A
Application number: GB8919497A
Authority: GB
Inventors: John Richard Dare; Denis Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-09-02
Filing date: 1989-08-29
Publication date: 1990-03-21
Also published as: GB8822168D0; GB8919497D0

Abstract

A hydraulic press 1 comprises a main pressing ram (4) working within a press housing 2 which acts as a cylinder (19), and thereby guides the pressing ram (4) during its working stroke. The ram counteracting means (9) is carried by a lid (3) fixed in position relative to the ram assembly, by a threaded ring (25), during a working stroke of ram (4) and means (eg. conduit 20, 21) are provided for supplying and draining hydraulic fluid to and from the housing (2) to that side (19) of the ram assembly opposite to the counteracting means, to apply the working pressure to moulds (7, 8), after a rapid closure stroke of the ram (4) has been effected, by a hydraulic piston/cylinder means (12, 11) within the ram 4. During pressing, vacuum is applied within the housing, via a tube 28, and the counteracting means (9) is supported by hydraulic pressure admitted within the lid (3). The housing chamber (19) enables a more accurate guiding of the ram (4) to be attained. <IMAGE>

Description

HYDRAULIC PRESS The present invention relates to a hydraulic press.

According to the present invention there is provided a hydraulic press comprising a main pressing ram assembly working within a press housing which acts as a cylinder for, and thereby guides, the pressing ram during its working stroke, ram counteracting means between which and the ram assembly articles are pressed, location means for locating the ram counteracting means fixed in position relative to the ram assembly during a working stroke thereof and means for supplying hydraulic fluid to and draining hydraulic fluid from the housing to that side of the ram assembly opposite to the counteracting means.

By providing the housing as a cylinder for the ram assembly the latter is accurately guided during its working stroke and any press-tools, eg. moulds, may be mounted on the ram assembly wholly within the bounds of its surface facing the counteracting means so that there will be no distortion of the press tools.

Preferably the ram counteracting means is provided in a lid removably mountable on the press housing. Preferably this lid has a cavity behind the ram counteracting means into which hydraulic fluid may be introduced and pressurised to counteract deflections produced by the main ram.

It is also preferred that a piston and cylinder arrangement is provided for effecting movement of the ram assembly between its retracted position (ie.

remote from the ram counteracting means) and its pressing position. In this case, hydraulic fluid behind the ram assembly is only pressurised during the actual pressing sequence thus avoiding the need for pressurising large quantities of hydraulic fluid whilst the ram is simply being moved to its pressing position. The cylinder of said position and cylinder arrangement may be provided within the main ram assembly and the piston fixed in position relative to the main ram assembly with its rod extending externally of the housing, means being provided (eg.

conduit in the rod) for supplying hydraulic fluid to one side or the other of the piston so as to effect movement of the ram assembly.

The press of the invention is particularly suitable for vacuum moulding operations, for which purpose the space between the ram assembly and the ram counteracting means is a closed space associated with means for creating the required vacuum therein.

The invention will be further described by way of example only with reference to the accompanying sectional view of one embodiment of press in accordance with the invention.

The illustrated press 1 comprises a generally cylindrical lower housing 2 closed by a dome-shaped lid 3. The main ram assembly 4 works within the lower housing 2 and comprises three main sections 4a, b and c, the upper one (4a) of which is provided with a layer 5 of- insulation and azi electrically heated platen 6. Once component 7 of the mould assembly is mounted on platen 6 for co-operation with a complimentary mould component 8 on a fixed ram counteracting assembly within the lid 3. This assembly includes a further electrically heated platen 9 and insulation 10.

A cylinder 11 is provided within the main ram assembly 4 and houses a piston 12 having a rod 13 extending downwardly out of the lower section 4c (of the ram assembly 4) and through the bottom of housing 2. This piston 12 is fixed in position relative to the ram assembly 4. A central passageway 14, (with a terminal port 14a) in the roc 13 allows hydraulic fluid to be fed to and from the chamber 15 (ie.

between the top of piston 12 and the underside of the upper section 4a of the ram assembly 4). An outer passageway 16 of the piston (with a terminal port 16a) allows hydraulic fluid to pass into and out of chamber 17 beneath piston 12. Thus upward movement of ram assembly 4 may be effected by introducing hydraulic fluid via passageway 14 into chamber 15 whilst draining fluid from chamber 17. Similarly the ram may be lowered (from its upper position) by the reverse of this sequence.

Unwanted rotation of ram assembly 4 is prevented by a peg 18 locating in an elongate groove 18a.

At the lowermost position of ram assembly 4, a chamber 19 remains at the bottom of the lower housing portion 2.

Associated with this chamber are two pre-fill inlets 20 each connected to a source of hydraulic fluid via valves (not shown) and also an inlet 21 communicating with a high pressure hydraulic fluid supply.

Reference is now made to the lid 3 which is hinged at point A and is such that it is lifted vertically (eg. by 100mm) from its closed position illustrated in the drawing before being pivoted about A opening of the press. The lid 3 is located on the lower housing 2 of the press by a trapezoidal ridge 20 on the housing 2 locating in a complimentary groove on the undersurface of the rim of the lid. An O-ring seal 21 is provided as shown.

Although not shown in the drawings, the top of housing 2 is castellated with six 'cut outs' spaced equally round its circumference. The outer faces of the merlons are provided with a left hand buttress thread 23. A right hand buttress thread 24 is provided continuously around the lid 3.

A locking ring 25 is provided as shown around the joint between the housing 2 and lid 3. The upper portion of ring 25 has continuous internal screw threads 26 complimentary with threads 24. The lower portion of ring 25 is castellated (not shown) and the inner faces of the merlons are provided with screw threads 27 complimentary with thread 23.

Thus by rotation of ring 25 so that its merlons register with the crenels in housing 2, the aforementioned pivotal opening of the lid 3 is permitted. The locking ring 25 serves of course to move the lid 3 into engagement with the housing 2.

Further features of the illustrated apparatus are an air bleed and vacuum extraction tube 28 extending from externally of the lid 3 through the fixed assembly therein and into the pressing chamber between the mould sections 7 and 8. Additionally the chamber 29 in lid 3 behind the fixed assembly is filled with hydraulic oil which may be pressurised (by means not shown) as that in chamber 19.

At the start of a moulding operation, lid 3 is engaged with housing 2 by the locking ring 25 and the ram assembly 4 is in its lowermost position. This assembly 4 is now raised rapidly by supplying hydraulic fluid to the chamber 15 above piston 12, as previously described. As ram assembly 4 is raised hydraulic fluid is drawn into chamber 19 through prefill inlets 20. During this operation, air between in the pressing chamber passes out through tube 28 until such time as the mould is closed and a vacuum pump is then used to pump air out of the pressing chamber through tube 28 until the required degree of vacuum is obtained.

The pre-fill inlets 20 are now closed and high pressure oil is introduced into chamber 19 through inlet 21 so as to pressurise the main ram assembly 4.

Simultaneously, the hydraulic fluid in chamber 29 is pressurised to the same pressure as that in chamber 19. This ensures that there is no distortion of mould component 18 relative to mould component 7.

The illustrated arrangement has the significant advantage that the pivotal lid 3 provides easy and complete access to the moulding chamber.

Claims

1. A hydraulic press comprising a main pressing ram assembly working within a press housing which acts as a cylinder for, and thereby guides, the pressing ram during its working stroke, ram counteracting means between which and the ram assembly articles are pressed, location means for locating the ram counteracting means fixed in position relative to the ram assembly during a working stroke thereof and means for supplying hydraulic fluid to and draining hydraulic fluid from the housing to that side of the ram assembly opposite to the counteracting means.

2. A press as claimed in Claim 1 wherein the ram counteracting means is provided in a lid removably mounted on the press housing.

3. A press as claimed in Claim 2 wherein the lid is pivotally mounted relative to the housing and may be secured relative thereto by a locking ring mounted on the lid, wherein the top of the housing and the lower region of the locking ring have complimentary projections spaced by recesses whereby rotation of the locking ring will bring the projections of the locking ring into register with the recesses of the housing and vice versa to permit pivotal opening of the lid.

4. A press as claimed in Claim 1 wherein the projection and recess formations comprise castellations.

5. A press as claimed in Claim 2 or 3 wherein the lid has a cavity behind the ram counteracting mean into which hydraulic fluid may be introduced and pressurised.

6. A press as claimed in any one of Claims 1 to 4 wherein a piston and cylinder arrangement is provided for effecting movement of the ram assembly between its retracted position (ie. remote from the ram counteracting means) and its pressing position.

7. A hydraulic press as claimed in Claim 6 wherein the cylinder of said piston and cylinder arrangement is provided within the main ram assembly and the piston is fixed in position relative to said assembly with its rod extending externally of the housing, and means are provided for supplying hydraulic fluid to one side or other of the piston so as to effect movement of the ram assembly.

8. A press as claimed in Claim 6 wherein the hydraulic fluid is supplied and exhausted along the rod of the piston.

9. A press as claimed in any one of Claim 1 to 7 wherein, when the ram assembly is in its retracted position, there is a chamber defined between the ram assembly and the associated end of the housing and said chamber is in communication with a supply of hydraulic fluid which is supplied to the chamber to pressurise the main ram assembly.

10. A press as claimed in any one of Claims 1 to 8 adapted for vacuum moulding operations wherein the space between the ram assembly and the ram counteracting means is a closed space associated with means for creating the required vacuum therein.

11. A press as claimed in any one of the preceding claims wherein the ram counteracting means and/or the main ram assembly are provided with heated platens.