GB2291694A

GB2291694A - Apparatus for limiting torque in a valve assembly

Info

Publication number: GB2291694A
Application number: GB9512270A
Authority: GB
Inventors: Keith Millward
Original assignee: Polypipe PLC
Current assignee: Polypipe PLC
Priority date: 1994-07-25
Filing date: 1995-06-16
Publication date: 1996-01-31
Anticipated expiration: 2015-06-16
Also published as: GB9512270D0; GB2291694B; GB9414954D0

Abstract

Apparatus for limiting torque in a valve assembly comprises a rotatable valve member 2 and an actuator 3 adapted to engage the valve member 2 for rotation thereof, the actuator 3 and the valve member 2 being adapted to disengage from one another when resistance to rotation of the valve member 2 in excess of the operating torque is encountered. The actuator 3 is provided at the end with a square socket 15 which snugly receives a shaft 10 of the valve member 2. The walls of the socket flex outwards when excessive torque is applied to the actuator, resulting in rotation of the actuator 3 relative to the valve member 2. <IMAGE>

Description

APPARATUS FOR LIMITING TOROUE IN A VALVE ASSEMBLY This invention relates to apparatus for limiting torque in a valve assembly, to a tap assembly including such apparatus, and to a kit of parts for providing such apparatus in an existing valve assembly. More particularly, the invention relates to apparatus which seeks to prevent damage to valve assemblies through the application of excessive force by an operator.

Problems have occurred in the past with valve assemblies due to the high torque which can be developed when the valve is closed against the valve seat if the valve handle continues to be turned; this effect is amplified if extension tools are used which fit over the valve handle to permit buried valves to be operated from a standing position. The hand grips of such an extension piece would typically be 300mm in width which gives a tremendous mechanical advantage compared to the cross section of the plastic spindle; and, in extreme cases, results in the spindle shearing at its smallest cross section which could result in failure or jamming of the valve. A similar effect can occur if the valve handle is turned when the valve is fully open.This problem has been addressed in the past by the provision of torque limiting systems, which seek to dissipate the force applied to the valve. It has been found however that in practice, such systems have a relatively short effective life, due to amongst other things wearing of the force-dissipating structures. The present invention seeks to mitigate disadvantages such as this.

Thus, according to a first aspect of the invention there is provided apparatus for limiting torque in a valve assembly, comprising a rotatable valve member and engagement means adapted to engage the valve member for rotation thereof, the engagement means and the valve member being adapted to disengage from one another when resistance to rotation of the valve member in excess of the operating torque is encountered.

The engagement means may include an engagement part adapted to receive a part of the valve member therein.

Alternatively, the valve member may include an engagement part adapted to receive a part of the engagement means therein.

The engagement part may comprise a resilient material.

The engagement part may comprise a socket, which may include a plurality of resilient walls. It is preferred that the socket includes four resilient walls.

The valve member may comprise a male part adapted to fit closely within the engagement part, and the male part may include means to allow rotation of the engagement part over the male part when resistance to rotation of the valve member in excess of the operating torque is encountered.

In the alternative, the engagement means may include a male part adapted to fit closely within the engagement part.

It is preferred that the male part may comprise a protuberance having at least three substantially planar surfaces, and it is most preferable that the male part comprises a square sectioned operating shaft.

The vertices of the shaft may be rounded off, such that the width of each planar surface is between 50 and 75cue and preferably 60etc of the total width of the shaft.

The apparatus may comprise securing means for securing the engagement means and valve member together. In one embodiment the securing means may rotatably secure them together, such as by a self tapping screw. In an alternative embodiment, the securing means may comprise a complementary nib and groove, or recess.

According to a second aspect of the invention there is provided a tap assembly, including apparatus as defined above.

According to a third aspect of the invention there is provided a kit of parts comprising a rotatable valve member for fitment into a valve assembly, and engagement means adapted to engage the valve member for rotation thereof, the engagement means and the valve member being adapted to disengage from one another when resistance to rotation of the valve member in excess of the operating torque is encountered.

The invention will further be described by way of example only, and with reference to the accompanying drawings in which, Figure 1 is a sectional view of a tap assembly including apparatus embodying the invention; Figure 2 is a side view of a valve spindle for use in apparatus embodying the invention; Figure 3 is a plan view of the spindle of Figure 2; Figure 4 is a longitudinal sectional view of a valve handle for use in apparatus embodying the invention; Figure 5 is a plan view of the handle of Figure 4; and Figure 6 is an underplan view of the handle of Figure 4.

Figure 7 is a sectional view of a tap assembly including a first alternative embodiment of apparatus embodying the invention and; Figure 8 is a sectional view of a tap assembly including a second alternative embodiment of apparatus embodying the invention.

Referring to the drawings there is shown apparatus 1 for limiting torque in a valve assembly, comprising a rotatable valve member 2 and rotation means 3 adapted to engage the valve member 2 for rotation thereof, the engagement means 3 and the valve member 2 being adapted to disengage from one another when resistance to rotation of the valve member 2 in excess of the operating torque is encountered.

The valve member 2 comprises a longitudinally extended cylindrical spigot, one end of which 4 is externally threaded 4a to cooperate with a riser 5 to seal a valve. The end 4 may be provided with a short lead-in part 6. The spigot 2 has two seal recesses 7 which are provided to accommodate two 'O'-ring seals to seal the spigot 2 with the valve head 8 which is fitted into the valve body 9 to operate the valve. At the top end (in use) of the spindle 2 there is provided a portion 10, which in the embodiment illustrated takes the form of a squaresectioned operating shaft.

The apices 17 of the shaft 10 are removed, in order to leave the corners rounded-off. The extent to which the apices 17 are removed determines how tightly the shaft 10 fits into the socket 15. It has been found that the best results are obtained if the apices 17 are removed, such that the width of the flat sides of the portion 10 are between 50 and 75%, typically 60% of the width of the sides of the shaft 10 prior to removal. In an alternative embodiment, the shaft 10 may be provided with recesses 18 on the rounded apices 17 which are adapted to engage with optional snap-fit nibs (not shown) provided on the internal surface of the bore 16 of the engagement part 14.

The rotation means 3 comprises a longitudinally extending cylindrical member 11 and is provided at one end with lugs 12 enabling it to be gripped by the user.

The opposite end has a frusto-conical part 13 upon which is mounted an engagement part 14. The engagement part 14 comprises a socket 15 having a substantially square profile in cross-section. The socket 15 has a longitudinally arranged square bore 16 which may be blind, or may communicate with the interior of the member 11. The bore 16 is dimensioned to receive the shaft 10 as a snug fit. The rotation means 3 is preferably formed from a resilient material. Examples of suitable materials are polypropylene and polyethylene.

In use with a valve for a water system for example, the rotation means 3 is applied to the shaft 10 of the spindle 2, such that the shaft is received within the socket 15, the sides of the shaft 10 abutting with the sides of the square bore 16.

When a rotation force is applied to the rotations means 3, via the lugs 12 for example, the square sides of the bore 16 grip the shaft 10 and hence cause the valve member 2 to rotate. If resistance to rotation of the spindle 2 is met which exceeds the operating torque, or if some other obstruction prevents the spindle 2 from rotating, the rotational force applied by the user causes the apices 17 of the shaft 10 to force the flat sides of the bore 16 outwards usually at their centres, facilitated by the flat inner and outer sides of the socket 15, and allowing the shaft to rotate within the socket 15. In this way the force is dissipated, without damage occurring to the spindle 2, valve assembly, or rotation means 3.

In an alternative embodiment, the valve member 2 and the rotation means 3 may be secured together when it is not desired to remove the rotation means, such that operation of the torque limiter is still possible. Referring to Figure 7, a securing means such as, as illustrated, a self tapping screw 19, may be provided which protrudes through a bore from the interior of the member 11 into the socket 15, and thence into biting engagement with the shaft 10. When secured in this way, the valve member 2 and rotation means 3 are held together, however as the rotation means 3 is free to rotate about the screw, it is still possible for the torque limiting arrangement described above to function properly, preventing damage occurring to the spindle 2, valve assembly, or rotation means.

Alternatively, in a second alternative embodiment illustrated in figure 8 a nib or nibs 21 are provided on the surface of the bore 16 which are adapted to cooperate with corresponding recesses 18 or a groove 22 on the portion 10. In a still further embodiment the nib or nibs may be located on the portion 10, and the recess or groove 18 may be located in the surface of the bore 16.

As will be appreciated, the valve member 2 and rotation means 3 may be adapted to disengage from one another by providing the rotation means 3 with a portion such as a square-sectioned operating shaft, as described above in relation to the valve member 2. Consequently the valve member 2 will be provided with a socket, as described above in relation to the rotation means 3.

Thus, using apparatus as shown in the drawings, embodying the invention, it has been found that where the flat width on the end of the spindle 2 is 60% of the width of the total width of the flats effective torque limitation is achieved when both opening and closing a valve. The 60% ratio permits sufficient torque to be applied to the spindle to close the valve against internal water pressure of say 12 bar.

The mechanism can be over-ridden repeatedly in alternate opening and closing operations whilst maintaining the valve functions.

Claims

1. Apparatus for limiting torque in a valve assembly, comprising a rotatable valve member and engagement means adapted to engage the valve member for rotation thereof, the engagement means and the valve member being adapted to disengage from one another when resistance to rotation of the valve member in excess of the operating torque is encountered.

2. Apparatus according to claim 1, wherein the engagement means includes an engagement part adapted to receive a part of the valve member therein.

3. Apparatus according to claim 1, wherein the valve member includes an engagement part adapted to receive a part of the engagement means therein.

4. Apparatus according to claim 2 or claim 3, wherein the engagement part comprises a resilient material.

5. Apparatus according to any of claims 2 to 4, wherein the engagement part comprises a socket.

6. Apparatus according to claim 5, wherein the socket includes a plurality of resilient walls.

7. Apparatus according to claim 5, wherein the socket includes four resilient walls.

8. Apparatus according to any claim 2, wherein the valve member includes a male part adapted to fit closely within the engagement part.

9. Apparatus according to any of claims 3 to 7, wherein the engagement means includes a male part adapted to fit closely within the engagement part.

10. Apparatus according to claim 8 or claim 9, wherein the male part includes means to allow rotation of the engagement part over the male part when resistance to rotation of the valve member in excess of the operating torque is encountered.

11. Apparatus according to any of claims 8 to 10, wherein the male part comprises a protuberance having at least three substantially planar surfaces.

12. Apparatus according to any of claims 8 to 10, wherein the male part comprises a square-sectioned operating shaft.

13. Apparatus according to claim 12, wherein the vertices of the shaft are rounded off, such that the width of each planar surface is between 50 and 75% of the total width of the shaft.

14. Apparatus according to claim 13, wherein the said width of each planar surface is 60% of the total width of the shaft.

15. Apparatus according to any preceding claim, including securing means for securing the engagement means and valve member together.

16. Apparatus according to Claim 15, wherein the securing means rotatably secures the engagement means and valve member together.

17. Apparatus according to Claim 16, wherein the securing means comprises a self tapping screw.

18. Apparatus according to Claim 15, wherein the securing means comprises a complementary nib and groove or recess.

19. Apparatus, substantially as hereinbefore described with reference to the accompanying drawings.

20. A tap assembly, including apparatus according to any of claims 1 to 19.

21. A tap assembly, substantially as hereinbefore described with reference to the accompanying drawings.

22. A kit of parts comprising a rotatable valve member for fitment into a valve assembly, and engagement means adapted to engage the valve member for rotation thereof, the engagement means and the valve member being adapted to disengage from one another when resistance to rotation of the valve member in excess of the operating torque is encountered.