DEVICE CONTAINING A FORCE-IMPARTING MEANS AND EQUIPPED WITH SAFETY MEANS

Abstract: A spring-containing device comprises a housing including a removable end plate (2). A plurality of screw-threaded tie rods (7) have nuts (10) holding the end plate (2) in assembly with the housing. A safety plate (13) is disposed within the housing against the end plate (2) and clear of a movable spring-retaining plate (8) at its closest approach to the end plate (2). The safety plate (13) is fast on a shaft (15) rotatable in the end plate (2) and adapted (at 18) to be turned from outside. The safety plate (13) has recesses (15) in its peripheral edge (14) through which recesses (15) respective tie rods (7) can pass. The tie rods (7) have recesses (19) which can receive the unrelieved edge (14) of the safety plate (13) when in a certain angular position and thus prevent longitudinal relative movement between the safety plate (13) and the tie rods (7).

Description: Device Containing a Force-Imparting Means and Equipped with Safety Means Description This invention relates to a device containing force-imparting means and equipped with safety means. Such a device is disclosed in WO 87/05986 and comprises 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 tie rods and nuts holding the end plate in assembly in the housing, and safety means comprising a safety plate within the housing between the end plate and the retaining means but clear of the latter at its closest approach to the end plate, the safety plate being fast on a shaft rotatable in the end plate and adapted to be turned from outside the housing, the safety plate and the tie rods having cooperating formations which in one angular position of the safety plate permit movement of the safety plate relative to the tie rods in a direction longitudinally thereof but in another angular position of the safety plate prevents such movement of the safety plate. In the device of the above-mentioned disclosure the cooperating formations are constituted by keyhole-shaped openings in the safety plate and through which openings the respective tie rods extend, and safety collars on the tie rods. In the one angular position of the safety plate the safety collars can pass through the respective keyhole-shaped openings. However in the other angular position of the safety plate the safety collars cannot pass through the respective keyhole-shaped openings. The provision of the keyhole-shaped openings in the safety plate and the safety collars on the tie rods imposes limitations on the degree to which the transverse dimensions of the housing can be reduced and thereby renders the device unsuitable in installations where space is at a premium. An object of the present invention is to obviate or mitigate the above disadvantages. Accordingly, the device of the invention is characterised in that the cooperating formations of the safety plate and the tie rods are constituted by a peripheral edge of the safety plate which edge is interrupted by recesses, one for each tie rod, and recesses .formed in what are the inner sides of the tie rods when in mutually assembled relationship, whereby in the one angular position of the safety plate the tie rods can pass through their respective recesses in the said edge of the safety plate, but in the other angular position of the safety plate the recesses in the plate are out of alignment with the tie rods and the unrelieved edge of the safety plate is receivable in the recesses in the tie rods. Preferably the peripheral edge of the safety plate is tapered and has flats therein adjacent to the recesses in the edge and the recesses in the tie rods are ramped, whereby when the safety plate is in the other angular position during dismantling of the device and the force in the force-imparting means has not been relieved, interengagement of the tapered edge of the safety plate or the flats in such edge with the ramps in the recesses of the tie rods causes the tie rods to become wedged between the safety plate and the end plate. The shaft may have fast thereon a flange which lies against the outer side of the end plate and has recesses in its peripheral edge, which recesses are so disposed relative to the recesses in the edge of the safety plate SUBSTITUTESHEET that only when the safety plate is in the other angular position the nuts can be removed from and applied to the screw-threaded tie rods. 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 sectional view of a spring- containing device equipped with safety means and in the unlocked condition; Fig 2 is similar to Fig 1 but in the locked condition; Fig 3 is a section on line Ill-Ill in Fig l; Fig 4 is a section on line IV-IV in Fig 2; Fig 5 is an end view of Fig 1; Fig 6 is an end view of Fig 2; and Fig 7 is similar to Fig 6 and also includes a nut- locking plate. In the drawing a spring-containing device comprises a housing which in turn comprises a cylindrical casing 1 to one end of which an end plate 2 is welded. A ring 3 is welded to the other end of the casing 1 and the ring 3 seats on a plate 4 secured to a main unit generally indicated by reference numeral 5. Suitably shaped, eg eccentric heads 6 of tie rods 7 are captive within recesses in the plate 4 so as to prevent rotation of the tie rods which extend through openings in a movable spring-retaining plate 8 and the end plate 2. The tie rods 7 terminate in screw-threaded portions 9 receiving nuts 10. A force-imparting means in the form of a compression spring 11 is captive within the housing between the end plate 2 and the plate 8. A movable rod 12 of the main unit 5 is biased by the spring 11 via the plate 8. The single spring 11 may be replaced by a plurality of compression springs equi-angularly spaced around and within the housing. SUBSTITUTE SHEET The device is equipped with safety means which comprises a safety plate 13 having a tapered peripheral edge 14 interrupted by recesses 15, one for each tie rod 7. The edge 14 may have a flat machined therein adjacent to each recess 15. The plate 13 is screwed on a shaft 16 and made fast thereon by dowels 17 or by any other keying means. Alternatively, the plate 13 may be welded on the shaft 16. The shaft 16 is rotatable in the plate 2 and adapted to be turned from outside the housing at 18 where a hexagonal end is provided. Each tie rod 7 has a ramped recess 19 formed therein on the inner side when the tie rods 17 are in their assembled relationship. In a modification the edge 14 of the safety plate 13 may be replaced by a planar annular shoulder for direct abutment with a shoulder in the recess 19, which replaces the ramp and lies in a plane normal to the axis of the tie rod 7. The shaft 16 has fast thereon a flange 20 which lies against the outer side of the end plate 2 and has recesses 21 in its peripheral edge, one for each nut 10. Also in its peripheral edge the plate 20 has a further recess 22 which cooperates with a pin 23 outstanding from the plate 2 to determine two angular positions of the plate 13. In one angular position of the safety plate 13, as shown in Figs 1 and 3, the tie rods 7 can pass through their respective recesses 15 in the edge of the plate 13. In this position, as shown in Fig 5, the nuts 10 cannot be applied to the screw-threaded portions 9 of the tie rods 7. In the other angular position of the safety plate 13, as shown in Figs 2 and 4, the recesses 15 are out of alignment with the tie rods 7 and the unrelieved edge 14 of the plate 13 is receivable in the recesses 19 in the tie rods 7. In this position, as shown in Fig 6, the nuts 10 can be removed from and applied to the screw-threaded portions 9 of the tie rods SUBSTITUTE SHEET 7. Also, as shown in Fig 7, a nut-locking plate 24 is removably applied about the exposed hexagonal end 18 of the shaft 16 and has flats which register with flats on the nuts 10 when the plate 13 is in the latter position. When the device is properly assembled the unrelieved edge 14 of the plate 13 is received in the recesses 19 in the tie rods 7, the nuts 10 are received in the recesses 21 in the edge of the flange 20 and the plate 24 is applied to lock the nuts 10. In order to dismantle the device it is first necessary to remove the plate 24. Thereafter the nuts 10 are removed and if there is no residual spring force remaining in the spring 11 there will be no resistance to turning the shaft 16, the flange 20 and the safety plate 13 so as to align the recesses 15 with the tie rods 7, whereupon dismantling can be completed. If however, there is a residual spring force remaining in the spring 11 after the nuts 10 are removed, the interengagement of the tapered edge 14 with the ramps of the recesses 19 wedges the tie rods 7 between the safety plate 13 and the end plate 2. This will be apparent, and particularly so if flats are machined in the edge 14, when attempting to turn the shaft 16, the flange 20 and the safety plate 13 in order to complete the dismantling. With the inclusion of flats in the tapered edge 14 there would be not only a friction and wedging action to overcome but also a camming action against the residual spring force. If there was a large residual spring force it would be difficult if not impossible to apply sufficient torque to the hexagonal end 18 to exercise the said camming action. In this case, further dismantling requires the end plate 2 to be pushed back a little so as to disengage to edge 14 or the flat therein from the recesses 19 so as to free the shaft 18 for turning. SUBSTITUTE SHEET Conversely, when re-assembling the device the safety plate 13 must be initially in its unlocked position so that the tie rods 7 can pass through the recesses 15. However, in this position the flange 20 prevents the application of the nuts 10 to the portions 9 of the tie rods 7. Thus, once the recesses 19 in the tie rods 7 are aligned with edge 14, the flange 20 and the safety plate 13 are turned to the locked position. In this position the unrelieved edge 14 can be allowed to seat in the recesses 19 with any spring forces held captive preparatory to further assembly. Also in this position the recesses 21 permit the nuts 10 to be applied. " When the nuts are fully tightened the edge 14 is no longer seated in the recesses 19 and finally the plate 24 is applied and removably secured to the end 18 so as to lock the nuts 10. Instead of a mechanical spring, the force-imparting means may be pneumatic, hydraulic, electrical and magnetic. SUBSTITUTESHEET

Claims: Claims 1. A device containing force-imparting means and equipped with safety means, the device comprising a housing including an end plate (2) , means (11) for imparting a force and captive within the housing between the end plate (2) and retaining means (8) biased by the force imparting means(11), a plurality of screw-threaded tie rods (7) and nuts (10) holding the end plate (2) in assembly in the housing, and safety means comprising a safety plate (13) within the housing between the end plate (2) and the retaining means (8) but clear of the latter at its closest approach to the end plate (2) the safety plate (13) being first on a shaft (16) rotatable in the end plate (2) and adapted to be turned from outside the housing, the safety plate (13) and the tie rods (7) having co-operating formations (15, 19) which in one angular position of the safety plate (13) permit movement of the safety plate (13) relative to the tie rods (7) in a direction longitudinally thereof but in another angular * position of the safety plate (13) prevents such movement of the safety plate 13, characterised in that the co¬ operating formation of the safety plate (13) and the tie rods (7) are constituted by a peripheral edge (14) of the safety plate (13) which edge (14) is interrupted by recesses (15) , one for each tie rod (7) and recesses (19) formed in what are the inner sides of the tie rod (7) when in mutually assembled relationship, whereby in the one angular position of the safety plate (13) the tie rods (7) can pass through their respective recesses (15) in the said edge (14) of the safety plate (13) , but in the other angular position of the safety plate (13) the recesses (15) in the plate (13) are out of alignment with the tie rods (7) and the unrelieved edge (14) of the safety plate (13) is receivable in the recesses (19) in the tie rods (7). 2. A device according to claim 1, characterised in that the peripheral edge (14) of the safety plate (13) is tapered and has flats therein adjacent to the recesses (15) in the edge (14) and the recesses (19) in the tie SUBSTITUTESHEET (15) in the edge (14) and the recesses (19) in the tie rods (7) are ramped, whereby when the safety plate (13) is in the other angular position during dismantling of the device and the force in the force-imparting means (11) has not been relieved, interengagement of the tapered edge (14) of the safety plate (13) or the flats in such edge (14) with the ramps in the recesses (19) of the tie rods (7) causes the tie rods (7) to become wedged between the safety plate (13) and the end plate (2) . 3. A device according to claim 1 or 2, characterised in that the shaft (16) has fast thereon a flange (20) which lies against the outer side of the end plate (2) and has recesses (21) in its peripheral edge, which recesses (21) are so disposed relative to the recesses (15) in the edge (14) of the safety plate (13) that only when the safety plate (13) is in the other angular position the nuts (10) can be removed from and applied to the screw-threaded tie rods (7) . 4. A device according to any preceding claim, characterised in that a nut-locking plate (24) is removably keyed to the shaft (16) for rotation therewith and has flats thereon for registering with flats on the nuts (10) when the safety plate (13) is in the other angular position.

Inventors: CALVERT MICHAEL ARNOLD, SHRIVE CHRISTOPHER PAUL, CALVERT, MICHAEL, ARNOLD, SHRIVE, CHRISTOPHER, PAUL
Applicants: PRIME ACTUATOR CONTROL SYSTEMS, PRIME ACTUATOR CONTROL SYSTEMS LTD
Application year: 1991
Main classification: F16P3
IPC codes: B01J3, F16F15, F16J13, F16P3, F17C13