GB2255388A - Device containing a force-imparting means and equipped with safety means - Google Patents

Abstract

A device comprises a housing having a fixed end plate (2); means (4, 5) for imparting a force within the housing between the end plate (2) and retaining means (6) biased by the force imparting means (4, 5); safety means comprising a fixed ring (3, Fig 2) and a mounting plate (7) for clamping contact with the ring (3), the mounting plate (7) having keyhole shaped openings through which screw-threaded bolts (17, Fig. 2) extend. The bolts are received in screw-threaded holes (11, Fig. 2) in the ring (3), whereby the heads (16, Fig. 2) of the bolts (11) constitute a safety collar. <IMAGE>

Description

DEVICE CONTAINING A FORCE-IMPARTING MEANS AND EQUIPPED WITH 8AFETY MEAN8 DESCRIPTION This invention relates to a device containing forceimparting means and equipped with safety means.

Such a device is disclosed in Wo 87/05986 and comprising a housing including an end plate, means for imparting a force and captive within the housing between the end plate and retaining means biased by the force imparting means, a plurality of screw-threaded rods and safety means within the housing, the safety means having keyhole-shaped openings through which the respective screw-threaded rods extend and the rods each having a safety collar which in a first angular position of the safety plate can pass through the respective keyhole-shaped opening but in a second angular position of the safety means cannot pass through the keyhole-shaped opening.

The device in the above-mentioned prior disclosure is designed with the rods as tie rods with nuts removably holding the end plate in assembly in the housing. The retaining means is removable from the housing and the safety means comprises a safety plate disposed within the housing at a fixed spacing from the end plate but short of the retaining means at the closest approach of the retaining means to the end plate. The safety plate is a shaft rotatable in the end plate and adapted to be turned from outside the housing.

The prior device is effective from the standpoint of safety but suffers from a disadvantage where cost is an important factor.

The object of the invention is to provide a device which affords protection to personnel during dismantling, and at the same time is considerably less expensive than the prior device.

Accordingly, the device of the invention is characterised in that the end plate is permanently part of the housing, the safety means comprises a ring also permanently part of the housing but at the opposite end of the housing and a mounting plate for the housing for clamping contact with the ring, the mounting plate having the keyhole-shaped openings, and the rods being in the form of headed bolts with their screwthreaded shanks threadedly received in screw-threaded holes in the ring and the heads of the bolts constituting the safety collars.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig 1 is an axial section through a spring cartridge according to the invention; Fig 2 is an enlarged view of a detail in Fig 1; and Figs 3 and 4 show the detail of the cartridge in its locked and unlocked positions respectively.

In the drawings, a spring cartridge comprises a housing having a cylindrical wall 1, an end plate 2 welded to one end of the wall 1 and a ring 3 welded the opposite end of the wall 1. Two co-axial coil springs 4 and 5 of different spring rates are retained within the housing between the end plate 2 and a retaining plate 6 which itself is held captive and centred by the ring 3. The housing is mounted by means of a mounting plate 7 to a main unit 8 having a movable rod 9 slidable through a central opening in the plate 7 and engaging in a recess 10, whereby the rod 9 is biased by the springs 4 and 5.

The safety aspects of the invention are more clearly shown in Figs 2, 3 and 4. The ring 3 has screw-threaded holes 11 circumferentially spaced therearound. The holes 11 each have an annular relief 12 at the inner end of thereof. The mounting plate 7 has, correspondingly, keyhole-shaped openings circumferentially spaced therearound and each keyhole-shaped opening has a wide portion 13 and a narrow portion 14 which extends from a recess 15. A headed bolt is provided for each hole 11 and opening 13, 14 and comprises a socket head 16 dimensioned to seat in the recess 15. The shank 17 of its bolt is threaded to engage threadedly in the hole 11 and is also recessed at 18 near but spaced from its free end. The recess 18 receives collets 19 which are held against radial removal by a wire clip 20. The collets 19 and clip 20 are received in the relief 12.Sealing in effected by an '0' ring 21 between the ring 3 and the plate 7 and by a bonded ring 22 between the bolt shank 17 and the ring 3.

Before welding the ring 3 to the wall 1 the bolt has its shank 17 screwed fully home in the hole 11 so that the recess 18 emerges fully from the relief 12. The collets 19 are inserted into the exposed recess 18 and held together by the clip 20. The bolt is then unscrewed until the collets 19 engage the shoulder between the recess 18 and the hole 11.

The housing is thus presented to the mounting plate 7 with the heads 16 each fully extended for insertion through the wide portion 13 of the respective keyhole-shaped opening as shown in Fig 4. The housing is then turned bodily so that the heads 18 each register with a respective recess 15 as shown in Fig 3, and the shank 17 extending through the narrow portion 14. The bolts are then ready to be screwed tight as shown in Fig 2.

When attempting to remove the housing from the unit 8 one firstly unscrews the bolt as far as the collets 19 will allow.

If all the heads 16 are still seated in the recess 15 it will be evident that there remains residual spring pressure in the springs 4 and 5. This will require that the housing be pushed firmly towards the plate 7 and then turned before removal can take place.

Instead of a mechanical spring means, the force-imparting means may be pneumatic, hydraulic, electrical or magnetic.

Claims (7)

1. A device comprising a housing having a fixed end plate; means for imparting a force within the housing between the end plate and retaining means biased by the force imparting means; safety means comprising a fixed ring and a mounting plate for clamping contact with the ring, the mounting plate having keyhole shaped openings through which screw-threaded rods extend and are received in screw-threaded holes in the ring, the heads of the rods constituting a safety collar.

2. A device according to claim 1, wherein collets are located on a recessed portion of the rods and engage in annular reliefs in the holes in the ring.

3. A device according to claim 1 or 2, wherein the end plate is welded to the housing.

4. A device according to any one of the preceding claims, wherein the force imparting means is mechanical spring means, pneumatic means, hydraulic means, electrical means or magnetic means.

5. A device according to claim 4, wherein the force imparting means comprises two springs acting between the end plate and the retaining means.

6. A device according to claim 5, wherein the springs have different spring rates.

7. A device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.