GB1564521A

GB1564521A - Fluid flow control valves

Info

Publication number: GB1564521A
Application number: GB2389076A
Authority: GB
Original assignee: Saunders Valve Co Ltd
Current assignee: Crane Process Flow Technologies Ltd
Priority date: 1977-06-01
Filing date: 1977-06-01
Publication date: 1980-04-10

Description

(54) IMPROVEMENTS IN AND RELATING TO FLUID FLOW CONTROL VALVES (71) We, SAUNDERS VALVE COMPANY LIMITED, a British Company of Cwmbran, Gwent, Wales do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to fluid control valves, and more particularly to fluid control valves suitable for controlling the flow of noxious or dangerous fluids.

Diaphragm valves are commonly used for the control of noxious or dangerous fluids, for example toxic, corrosive, or inflammable fluids.

Such a valve includes a flexible diaphragm movable by an operating mechanism between a closed position in which the diaphragm engages a seat in the bore of the valve to close the valve fluid flow, and an open position spaced from the seat. The diaphragm separates the operating mechanism from the fluid being controlled and is sealed to the body of the valve to prevent leakage of fluid from the bore of the valve. If, however, the diaphragm is perforated or ruptures, the controlled fluid can reach the region of the operating mechanism, and if the operating mechanism itself is not sealed, can escape from the mechanism to the exterior of the valve.

The operating mechanism of a typical prior art diaphragm valve comprises a compressor member coupled to the diaphragm and housed within a bonnet secured to the valve body, and a spindle coupled to the compressor member and extending through the wall of the bonnet to receive a handwheel. In order to seal the operating mechanism in such a valve it is necessary to provide a seal arrangement to prevent fluid escaping between the spindle and the bonnet.

According to the present invention there is provided a fluid flow control valve comprising a valve body defining a flow passage, a diaphragm secured to the valve body and movable by a compressor member to close the flow passage to fluid flow, a bonnet secured to the valve body and housing the compressor member, an operating spindle coupled to the compressor member for moving the compressor member to move the diaphragm, the operating spindle having a first portion in screw threaded engagement with the bonnet and a second portion extending from the first portion to the exterior of the bonnet, and seal means forming a fluid tight seal between the second portion of the spindle and the bonnet.

Preferably, the second portion of the spindle has a smooth cylindrical surface, in which case the seal means may comprise an 0-ring located in a groove formed in the neck of the bonnet. This arrangement is cheap and particularly advantageous in that the screw threads on the spindle are completely isolated from the atmosphere, and are thus not subject to atmospheric corrosion or to contamination, and grease provided for the screw threads of the spindle cannot escape to the exterior of the valve.

Preferably, in order to keep the stroke of the spindle, and thus the size of the bonnet and the overall size of the valve to a minimum, the spindle is coupled to the compressor member by a screw threaded third portion which screw threadedly engages the compressor member, the screw threads of the third portion being of opposite hand to those of the first portion.

The spindle may be provided with a handwheel to facilitate its rotation. Because the sealing between the spindle and the bonnet is effected by a seal located in the bonnet neck, the handwheel may be of a simple design, and does not require accurate machining. This provides a considerable cost advantage over prior art sealed bonnet valves in which the handwheel was accurately machined to form part of the sealing arrangement.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings, wherein: Figures 1 and 2 show a sealed bonnet diaphragm valve in a fully open and fully closed configuration respectively.

The valve 1 shown in the drawings comprises a valve body 2 and a diaphragm 3 movable by a compressor 4 between the open position shown in Figure 1 and the closed position shown in Figure 2. In the closed position the diaphragm is pressed against a seat 5 defined on the valve casing to close the flow passage 6 of the valve to fluid flow.

The compressor 4 is housed within a bonnet 7 and is provided with ribs which slidingly engage further ribs on the bonnet to prevent relative rotation of the compressor and bonnet.

The lower end of the bonnet is provided with a flange 8 which is clamped, for example by bolts, to the valve body, with the periphery of the diaphragm 3 sandwiched between the flange 8 and the valve body. This arrangement ensures that the diaphragm is sealed to the valve body and that the lower end of the cavity 9 defined by the bonnet 7 is sealingly closed.

An operating spindle 10 has a first portion 11 screw threadedly engaged with a screw threaded portion of the bonnet and a second smooth cylindrical portion 12 extending from the first portion 11 through the neck 13 of the bonnet to the exterior of the bonnet. A third portion 14 of the spindle is provided with screw threads of the opposite hand to the screw threads of the first portion 11 and is screw threadedly engaged with a central bore in the compressor. A handwheel 20 is secured to the top of the spindle 10 to facilitate its manual rotation.Because of the opposite screw threads on the first and third portions of the spindle, as the spindle is rotated clockwise (as viewed from above) from the position shown in Figure 1, the spindle moves downwardly relative to the bonnet and the compressor moves downwardly relative to the spindle with the result that the axial displacement of the compressor is greater than the axial displacement of the spindle. In the embodiment shown, the threads on the first and third portions are of equal pitch, and the axial displacement of the compressor is twice that of the spindle.

In order to provide a fluid-tight seal between the spindle and the bonnet an 0-ring 15 is located in a groove 16 machined in the neck 13 of the bonnet. The 0-ring is of a material chemically resistant to the controlled fluid, and may, for example be of nitrile rubber, butyl rubber or vitor as appropriate. The 0-ring 15 permits rotational and translational movement of spindle 12,but prevents the escape of fluid between the spindle and the bonnet from the cavity 9 in the event of diaphragm failure, and prevents contamination and atmospheric corrosion of the threads of the spindle. A grease reservoir 17 is preferably provided just below the seal groove 16, and in this case the 0-ring 15 also prevents escape of grease from the reservoir to the exterior of the valve.

A brightly coloured plastics sleeve 18 is preferably secured over the bonnet neck in such a manner that when the valve is fully closed (Figure 2) the sleeve 18 is substantially completely covered by a skirt 19 depending from the handwheel. In this way, the amount of the sleeve 18 which is exposed to view provides an indication of how far the valve is open.

It will be noticed that, since the handwheel plays no part in forming the seal between the spindle and the bonnet, it need not be accurately machined and may, for example, be a simple casting. If desired, the sleeve 18 may be provided with a lip seal 21 which cooperates with the inner surface of skirt 19 to prevent ingress of grit, water, etc into the cavity defined by the skirt 19 when the valve is open.

It will be appreciated that, although the above described valve is particularly intended for use in controlling noxious or dangerous fluids, it may be used for controlling any suitable fluid.

WHAT WE CLAIM IS: 1. A fluid flow control valve comprising a valve body defining a flow passage, a diaphragm secured to the valve body and movable by a compressor member to close the flow passage to fluid flow, a bonnet secured to the valve body and housing the compressor member, an operating spindle coupled to the compressor member for moving the compressor member to move the diaphragm, the operating spindle having a first portion in screw threaded engagement with the bonnet and a second portion extending from the first portion to the exterior of the bonnet, and seal means forming a fluid tight seal between the second portion of the spindle and the bonnet.

2. A fluid flow control valve according to claim 1 wherein the second portion of the spindle has a smooth cylindrical surface, and the seal means comprises an 0-ring located in a groove formed in the bonnet.

3. A fluid flow control valve according to claim 1 or claim 2 wherein a grease reservoir is located between the seal means and the screw threads of the bonnet which engage the first portion of the spindle.

4. A fluid flow control valve according to any preceding claim wherein the spindle has a screw threaded third portion in screw threaded engagement with the compressor, the screw threads of the third portion being of opposite

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the handwheel may be of a simple design, and does not require accurate machining. This provides a considerable cost advantage over prior art sealed bonnet valves in which the handwheel was accurately machined to form part of the sealing arrangement. The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings, wherein: Figures 1 and 2 show a sealed bonnet diaphragm valve in a fully open and fully closed configuration respectively. The valve 1 shown in the drawings comprises a valve body 2 and a diaphragm 3 movable by a compressor 4 between the open position shown in Figure 1 and the closed position shown in Figure 2. In the closed position the diaphragm is pressed against a seat 5 defined on the valve casing to close the flow passage 6 of the valve to fluid flow. The compressor 4 is housed within a bonnet 7 and is provided with ribs which slidingly engage further ribs on the bonnet to prevent relative rotation of the compressor and bonnet. The lower end of the bonnet is provided with a flange 8 which is clamped, for example by bolts, to the valve body, with the periphery of the diaphragm 3 sandwiched between the flange 8 and the valve body. This arrangement ensures that the diaphragm is sealed to the valve body and that the lower end of the cavity 9 defined by the bonnet 7 is sealingly closed. An operating spindle 10 has a first portion 11 screw threadedly engaged with a screw threaded portion of the bonnet and a second smooth cylindrical portion 12 extending from the first portion 11 through the neck 13 of the bonnet to the exterior of the bonnet. A third portion 14 of the spindle is provided with screw threads of the opposite hand to the screw threads of the first portion 11 and is screw threadedly engaged with a central bore in the compressor. A handwheel 20 is secured to the top of the spindle 10 to facilitate its manual rotation.Because of the opposite screw threads on the first and third portions of the spindle, as the spindle is rotated clockwise (as viewed from above) from the position shown in Figure 1, the spindle moves downwardly relative to the bonnet and the compressor moves downwardly relative to the spindle with the result that the axial displacement of the compressor is greater than the axial displacement of the spindle. In the embodiment shown, the threads on the first and third portions are of equal pitch, and the axial displacement of the compressor is twice that of the spindle. In order to provide a fluid-tight seal between the spindle and the bonnet an 0-ring 15 is located in a groove 16 machined in the neck 13 of the bonnet. The 0-ring is of a material chemically resistant to the controlled fluid, and may, for example be of nitrile rubber, butyl rubber or vitor as appropriate. The 0-ring 15 permits rotational and translational movement of spindle 12,but prevents the escape of fluid between the spindle and the bonnet from the cavity 9 in the event of diaphragm failure, and prevents contamination and atmospheric corrosion of the threads of the spindle. A grease reservoir 17 is preferably provided just below the seal groove 16, and in this case the 0-ring 15 also prevents escape of grease from the reservoir to the exterior of the valve. A brightly coloured plastics sleeve 18 is preferably secured over the bonnet neck in such a manner that when the valve is fully closed (Figure 2) the sleeve 18 is substantially completely covered by a skirt 19 depending from the handwheel. In this way, the amount of the sleeve 18 which is exposed to view provides an indication of how far the valve is open. It will be noticed that, since the handwheel plays no part in forming the seal between the spindle and the bonnet, it need not be accurately machined and may, for example, be a simple casting. If desired, the sleeve 18 may be provided with a lip seal 21 which cooperates with the inner surface of skirt 19 to prevent ingress of grit, water, etc into the cavity defined by the skirt 19 when the valve is open. It will be appreciated that, although the above described valve is particularly intended for use in controlling noxious or dangerous fluids, it may be used for controlling any suitable fluid. WHAT WE CLAIM IS:

1. A fluid flow control valve comprising a valve body defining a flow passage, a diaphragm secured to the valve body and movable by a compressor member to close the flow passage to fluid flow, a bonnet secured to the valve body and housing the compressor member, an operating spindle coupled to the compressor member for moving the compressor member to move the diaphragm, the operating spindle having a first portion in screw threaded engagement with the bonnet and a second portion extending from the first portion to the exterior of the bonnet, and seal means forming a fluid tight seal between the second portion of the spindle and the bonnet.

hand to the screw threads of the first portion.

5. A fluid flow control valve according to any preceding claim wherein a handwheel is secured to a spindle to facilitate manual rotation of the sprindle, and a skirt depends from the handwheel to cooperate with a marker on the bonnet to provide a visual indication of the state of opening of the valve.

6. A fluid flow control valve according to claim 5 wherein the marker comprises a plastics sleeve secured to the bonnet, the colour of the sleeve contrasting with that of the skirt, and wherein the sleeve carries a lip seal which sealingly engages the inwardly facing surface of the skirt.

7. A fluid flow control valve, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.