GB2029887A

GB2029887A - Releasable clamping assembly

Info

Publication number: GB2029887A
Application number: GB7836977A
Authority: GB
Original assignee: TRENT VALVE CO Ltd
Current assignee: TRENT VALVE CO Ltd
Priority date: 1978-09-15
Filing date: 1978-09-15
Publication date: 1980-03-26
Also published as: GB2029887B

Abstract

A releasable clamping assembly, particularly for use in valve testing apparatus, comprises two plate members (10, 11) mounted for relative angular movement about an axis of the assembly and a plurality of clamping jaws (22) mounted on one of said plate members (10) for radial inward and outward movement relative thereto. The other plate member (11) has elongate means, such as an arcuate slot (17) operatively connected to each clamping member and extending transversely to the aforesaid radial direction of an associated clamping member. Upon relative angular movement of the two plate members the resulting angular movement between the elongate means and the clamping members will cause the clamping members to undergo radial inward or outward movement relative to the first member. <IMAGE>

Description

SPECIFICATION Releasable clamping assembly This invention relates to a releasable clamp ing assembly and has as its object the provision of such an assembly in a convenient form.

The invention provides a releasable clamping assembly comprising a first plate, a plural ity of clamping members mounted on said first plate for radially inward and outward movement relative thereto, and a second plate mounted with respect to the first plate for relative angular movement therebetween and having elongated means operatively connected to each clamping member and extending in a direction transverse to the aforesaid radial direction such that upon relative angular movement of the first and second plates the resulting relative angular movement between the elongated means and the clamping members will cause the clamping members to effect radially inward or outward movement relative to the first plate.

Preferably, each clamping member has an axially directed projection, e.g. a spigot which engages a radially directed slot or recess in the first plate and the associated elongated means.

Desirably, the elongated means comprise slots or recesses each of which conveniently defines an arc.

Preferably, the axially directed projection on each clamping member projects through both an associated radially directed slot in the first plate and an elongated slot, extending in a direction transverse to the aforesaid radial direction, in the second plate and co-operates with fastening means at its free end for axially retaining the clamping members relative to the first and second plates.

Advantageously, each clamping member has a radially inwardly directed jaw, the jaws and second plate being disposed on opposite axial sides of the first plate.

Conveniently, one of the plates has one or more axially directed projections and the other plate has one or more arcuate slots or recesses centred on the axis of relative angular movement of the plates co-operating with the axially directed projection(s) on said one plate for guiding the plates with respect to each other during relative angular movement therebetween.

Conveniently, the assembly further includes a head mounted axially inwardly of jaws of the clamping members and having associated dluid pressure actuated means for causing it to move along the axis of the assembly so as, in use, to axially engage the inner end of a device clamped by the clamping members.

The invention also provides valve testing apparatus including a releasable clamping assembly as hereinbefore described.

The invention will now be more particularly described with reference to and as shown in the accompanying drawings, wherein: Figure 1 is a rear view of one embodiment of a releasably clamping assembly according to the invention; and Figure 2 is a sectional side view partly of the embodiment shown in Fig. 1.

Referring to the drawings, the releasable clamping assembly shown therein comprises a stationary plate 10 and an angularly movable plate 11. The stationary plate 10 is secured to a stand 12 and has a first group of three radially inwardly extending elongated, through slots 13a, 136 and 13which are equiangularly spaced and a second group of two like slots 1 4a and 1 4b which are disposed diametrically opposite one another.The angularly movable plate 11 has three equi-angularly spaced arcuate through slots 1 spa, 1 5b and 1 5 c which lie on a common circle centred on the axis of relative angular movement of the plates 10 and 11 and each of which receives a spigot 16 projecting from the plate 10 in a direction parallel to said axis. The free ends of the spigots may be screw-threaded to receive internally screw-threaded nuts to prevent relative axial displacement of the two plates 10 and 11 whilst the spigots 16 support and guide the plate 11 during angular movement which movement is limited by the arcuate length of the slots 15.The plate 11 also has three elongated slots 1 7 a, 1 7 b and 17c of arcuate shape which each extend in a direction transverse but not normal to a radius of the plate 11 intersecting the slot 17. The outer ends of the slots 1 7 a, 1 7 b and 1 7 c are equi-angularly spaced and these slots 1 7a, 1 7 band 1 7 c communicate with the slots 1 3 a, 1 3 b and 1 3 c respectively for a reason which will become more apparent later. The plate 11 also has an additional and similar slot 18 which together with an inner portion of slot 1 7 b communicate respectively with slots 1 4a and 1 4b also for a reason which will become apparent later.

The plate 11 has a central aperture and is mounted about a cylinder of an hydraulic piston and cylinder unit 19 which is secured to the rear face of the plate 10 and which has a piston rod 20 which extends through a central aperture in the plate 10 and which carries at its free end a pressure head 21.

The assembly also includes three clamping members 22 each of which has at one end a radially inwardly directed jaw 23 and at its opposite end an axially directed projection which as shown comprises a spigot 24. Each spigot 24 projects through one of the slots 13a, 1 3 b, 1 3 c and then through the slot 1 7 a, 17 b, 17e communicating therewith. The free end of each spigot 24 is screw-threaded and co-operates with an internally screw-threaded nut 25 to retain the clamping member in an axial direction with respect to the plates 10 and 11.

Each clamping member has a second spigot 30 which as shown and by way of example is mounted radially outwardly of the spigot 24.

The spigot 30 is shorter than the spigot 24 and projects only into radially directed slot 13a, 13b, 13cto prevent angular movement of the associated clamping member about the axis of the spigot 24.

As shown in the drawings the slots 13a, 136 and 13e communicate with the outer ends of the slots 1 7 a, 1 7 b and 1 7 c respectively and as a result the clamping members 22 are at their radially outmost position. Angular movement of the plate 11 in a clockwise direction as viewed in Fig. 1 will cause the clamping members 22 to move progressively radially inwards along the slots 13a, and 13c by virtue of the interengagement between the spigots 24 and the edges of the slots 17a, 1 7 6 and 17c.

In the specific embodiment shown the assembly is used to support flanged valves so that they may be tested. The valve is located between the clamping members whilst the latter are in a outer radial position whereupon the plate 11 is moved in a clockwise direction until the jaws 23 grip the valve body with the flange of the valve located axially inwardly of the jaws 23. Hydraulic fluid is then applied to the piston of the unit 19 in a sense to move the pressure head 21 into engagement with the flanged end of the valve so as to trap the flange of the valve between the pressure head 21 and the inner axial end of the jaws 23.

The valve may be released by reversing this procedure.

The pressure head 21 has a radial passage 26 communicating with an axial passage 27 for supplying hydraulic fluid under pressure to the valve for testing purposes. An adaptor 28 of desired axial length is connected to the pressure head 21 by mutually engagable screw-threads and one or more 'O'-ring seals or another suitable seal 29 is preferably carried by both the pressure head 21 and the adaptor 28.

The assembly as described above provides for three point clamping, but if for particular applications, two point clamping is preferred, then the lowest clamping member 22 is left in position whilst the other two are rearranged with their associated spigots 24 projecting through radial slots 14a and 14b and arcuate slots 18 and 1 7 b respectively. Although, the lowest clamping member is not removed only two point clamping will be effected since the lowest member will not become operative due to the two diametrically opposite members being initially closer to the central axis of the assembly than the lowest member.

Claims

1. A releasable clamping assembly comprising first and second members mounted for relative angular movement about an axis, and a plurality of clamping members mounted on said first member for radial inward and outward movement relative thereto, the second member having elongate means operatively connected to each clamping member and extending transversely to the aforesaid radial direction of an associated clamping member such that upon relative angular movement of the first and second members the resulting relative angular movement between the elongate means and the clamping members will cause the clamping members to undergo radial inward or outward movement relative to the first member.

2. An assembly as claimed in claim 1, wherein each clamping member has an axially directed projection which engages a radially directed slot or recess in the first member and the associated elongate means.

3. An assembly as claimed in claim 1 or claim 2, wherein the elongate means associated with each clamping member comprises a slot or recess.

4. An assembly as claimed in claim 3, wherein each slot or recess of the elongate means defines an arc.

5. An assembly as claimed in claim 3 or claim 4 when dependent on claim 2, wherein the axially directed projection on each clamping member projects through both an associated radially directed slot in the first member and an elongate slot, extending transversely to the aforesaid radially directed slot, in the second member and has means whereby it is axially retained relative to the first and second members.

6. An assembly as claimed in claim 5, wherein each clamping member has a further axially directed projection spaced radially from the first mentioned projection and extending only into the associated radially directed slot in the first member to prevent twisting of the clamping member about its first mentioned projection.

7. An assembly as claimed in any one of the preceding claims, wherein one of the members has one or more axially directed projections and the other member has one or more arcuate slots or recesses, which is/are centred on the axis of relative angular movement of the members, co-operating with the axially directed projection(s) on said one member for guiding the members with respect to each other during relative angular movement therebetween.

8. An assembly as claimed in any one of the preceding claims, further comprising a head mounted axially inwardly of jaws of the clamping members and having associated fluid pressure actuated means for causing it to move along the axis of the assembly so as, in use, to axially engage the inner end of a device clamped by the clamping members.

9. A releasable clamping assembly, sub stantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

10. Valve testing apparatus including a releasable clamping assembly as claimed in any one of the preceding claims.