GB2290367A

GB2290367A - Fluid flow regulator

Info

Publication number: GB2290367A
Application number: GB9511531A
Authority: GB
Inventors: Leon Phipson
Original assignee: Delta Fluid Products Ltd
Current assignee: Delta Fluid Products Ltd
Priority date: 1994-06-11
Filing date: 1995-06-07
Publication date: 1995-12-20
Also published as: GB9511531D0

Abstract

A gas flow regulator comprises a hollow body (10) having a control unit mounting aperture (12), a gas inlet (14) and a gas outlet (16). A valve member (62) cooperating with a valve seat (68) is mounted on a hollow valve spindle connected with diaphragms (38) and (48) in a control unit (24). The interior of the valve spindle (46) opens into the space between the diaphragms (38) and (48) and extends to the downstream side of the valve member (62) so as to open into the flow passage via inlets which open into the passage transversely of the direction of fluid flow therepast so that a venturi effect is used to monitor pressure and control movement of the valve member (62) relative to the valve seat (68). The control unit (24) has a stepped mounting ring (32) through which it is removably secured to the body (10) by set screws (86). An apertured flange (20) sealingly receives the valve seat (68), which is mounted on support legs (72) carried by the control unit (24). The legs (72) are a slight clearance fit in the ring (32) so as to enable correct alignment and sealing of the mounting ring (32) and valve seat (68) in the respective apertures. <IMAGE>

Description

FLUID FLOW REGULATOR This invention relates to a fluid flow regulator and is more particularly, though not exclusively, concerning with a gas flow regulator of a type which is intended to be used in industrial gas metering to enable accurate pressure regulation.

It has been previously proposed to provide a fluid flow regulator comprising a hollow body having a control unit mounting aperture, a fluid inlet, a fluid outlet and a fluid flow passage extending between the inlet and the outlet; and a control unit which is removably connected to the hollow body, the control unit including (a) a mounting ring sealingly engaged with the control unit mounting aperture (b) support legs carried by the mounting ring and extending into the fluid flow passage, (c) an annular valve seat carried by the support legs so as to be sealed with an internal annular surface in the body, (d) a valve member mounted in the fluid flow passage for movement relative to the valve seat in order to control the flow of fluid through the regulator in use, and (e) control means carried by the mounting ring and operably connected with the valve member for controlling movement of the latter relative to the valve seat. With such regulator, the control unit can be detached from the hollow body so that the whole of the control unit including the valve seat and the valve member can be readily serviced. However, it is difficult to ensure that a reliable seal is provided both between the mounting ring and the control unit mounting aperture and between the annular valve seat and the internal annular surface in the body at the stage when the control unit is connected to the hollow body without risk of damage either to the hollow body or to the control unit or both when the control unit is secured in position (usually by securing screws).

It is an object of a first aspect of the present invention to obviate or mitigate this disadvantage.

According to said first aspect of the present invention, there is provided a fluid flow regulator comprising a hollow body having a control unit mounting aperture, a fluid inlet, a fluid outlet and a fluid flow passage extending between the inlet and the outlet; and a control unit which is removably connected to the hollow body, the control unit including (a) mounting means sealingly engaged with the control unit mounting aperture, (b) support means carried by the mounting means and extending into the fluid flow passage, (c) a valve seat carried by the support means so as to be sealed with an internal surface in the body, (d) a valve member mounted in the fluid flow passage for movement relative to the valve seat in order to control flow of fluid through the regulator in use, and (e) control means carried by the mounting means and operably connected with the valve member for controlling movement of the latter relative to the valve seat; wherein the valve seat is mounted on the mounting means by way of the support means so as to be movable to a limited extent relative to the mounting means.

By mounting the valve seat in this way, it is possible to achieve sealing between the respective parts without stressing such parts despite any minor manufacturing tolerances which arise in the manufacture of the control unit and/or the hollow body.

Whilst the valve seat is mounted so as to be movable to a limited extent relative to the mounting means, it is to be appreciated that such movement is prevented or restricted once the control unit has been secured in position relative to the hollow body. Thus, the reference to "movable" in this context is to be interpreted herein accordingly.

In a preferred embodiment, this limited movement of the valve seat relative to the mounting means is enabled by loosely mounting the support means relative to the valve seat or to the mounting means or, possibly, both.

In a convenient embodiment, the support means comprises a multiplicity of support legs which are engaged with slight clearance in recesses in the mounting means or in the annular valve seat, but preferably in the former. Conveniently, the support legs are retained in the respective recesses by means of a spring clip.

In a particularly convenient embodiment, a ring seal is disposed between the outer periphery of the valve seat and the internal surface in the body so as to effect sealing between the valve seat and the body. Likewise, it is preferred for the mounting means to have a surface which is engaged within the control unit mounting aperture with a ring seal therebetween.

With such an arrangement, it is possible to retain the mounting means in position by means of retaining screws or other retaining means which extend radially relative to the control unit mounting aperture to engage in a peripheral groove in the mounting means. The peripheral groove may have an inclined side wall for cooperation with the retaining means to ensure that the mounting means and the valve seat are held at the correct axial position relative to the respective parts with which they are sealed.

Most preferably, the control means includes a housing which is disposed externally of the hollow body and which is detachably secured to the mounting means.

The fluid flow regulator is preferably of the type where the control means is of the diaphragm-type.

It is particularly preferred for the hollow body to have the fluid inlet and fluid outlet mutually inclined, most preferably mutually perpendicularly.

With such an arrangement, it is also preferred for the control unit mounting aperture, the fluid outlet and the internal surface to be located on a common axis.

Diaphragm-controlled fluid flow regulators are known which comprise a hollow body, a fluid inlet, a fluid outlet and a fluid flow passage extending between the inlet and the outlet, there being a valve member mounted in the fluid flow passage for movement relative to a valve seat in order to control the flow of fluid through the regulator in use. Control of the valve member is effected by means of a diaphragm connected with the valve member so that movement of the diaphragm effects movement of the valve member.The diaphragm is acted upon by pressure in the fluid flow passage via a pressure-transmitting passage which extends from a predetermined location in the fluid flow passage adjacent the outlet to a chamber to which one side of the diaphragm is exposed so that changes in pressure at said location in the fluid flow passage are transmitted to the chamber to act on the diaphragm so as to enable the pressure at the outlet to be controlled, usually to a constant value. In such previously proposed diaphragm-controlled fluid flow regulators, the pressure-transmitting passage opens into the fluid flow passage downstream of the moveable valve member and faces the outlet.

It is a disadvantage of this type of fluid flow regulator that the effectiveness of pressure sensing is reduced when low differential pressures occur across the valve member.

It is an object of a second aspect of the present invention to obviate or mitigate such disadvantage.

According to said second aspect of the present invention, there is provided a fluid flow regulator comprising a hollow body having a fluid inlet, a fluid outlet and a fluid flow passage extending between the inlet and the outlet, a valve member mounted in the fluid flow passage for movement relative to a valve seat in order to control flow of fluid through the regulator in use, a diaphragm connected with the valve member so that movement of the diaphragm effects movement of the valve member, a diaphragm chamber, and a pressure-transmitting passage providing communication between the diaphragm chamber and the fluid flow passage, wherein the pressure-transmitting passage has at least one inlet opening into the fluid flow passage in a direction transversely of the direction of fluid flow therepast whereby, in use, the venturi effect is used to monitor the pressure.

In a preferred embodiment, at least a pair of oppositely directed inlets are provided for the pressure-transmitting passage.

Preferably, the or each inlet to the pressure-transmitting passage is disposed nearer to the wall of the passage than to the centre.

This second aspect of the present invention is particularly applicable to regulators where the pressure-transmitting passage opens into the fluid flow passage downstream of the valve member.

Conveniently, said at least one inlet is defined by at least one inlet passage in part of the valve member.

Also according to the present invention there is provided a fluid flow regulator according to both of said first and said second aspects of the present invention.

An embodiment of the present 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 gas flow regulator according to the present invention, and Fig 2 is an axial section of part of the regulator showing a modification.

Referring now to Fig 1 of the drawings, the gas flow regulator, which is for mounting on a commercial gas meter, comprises a hollow body 10 having a control unit mounting aperture 12 which is internally stepped, a gas inlet 14 and a gas outlet 16. The cavity 18 of the hollow body 10 provides a gas flow passage which extends between the inlet 14 and the outlet 16. The body 10 is formed internally with a flange 20 which is apertured so as to define an internal annular surface 22 within the cavity 18. The body 10 is formed so that the aperture 12, the outlet 16 and the internal annular surface 22 lie on a common axis X-X.

The gas flow regulator further comprises a diaphragm-type control unit 24 which is removably secured to the hollow body 10. The control unit 24 comprises a housing defined by housing parts 26 and 28 secured together by screws 30. The control unit 24 additionally comprises a stepped mounting ring 32 which is disposed within the control unit mounting aperture 12 and to which the housing part 26 is secured by means of screws 34 individually fitted with O-ring seals 36. The control unit 24 further comprises a main diaphragm 38 whose central section is sandwiched between main diaphragm plates 40 and 42. The main diaphragm plates 40 and 42 have secured thereto a spacer 44 which is engaged with a valve spindle 46 so as to trap therebetween a secondary diaphragm 48 and secondary diaphragm plates 50 and 52.The outer periphery of the main diaphragm 38 includes a sealing flange 54 which seals the joint between the housing parts 26 and 28. The outer periphery of the secondary diaphragm 48 is likewise formed with an integral sealing flange 56 which serves to seal the joint between the mounting ring 32 and the housing part 26.

The spacer 44 serves to maintain the desired spacing between the diaphragms 38 and 48 which are centred on the axis X-X and are biassed to the right (as viewed in the drawing) by a compression spring 58 acting between the main diaphragm plate 40 and a spring adjuster 60. The spring adjuster 60 is adjustably mounted in the housing part 28 for movement along axis X-X for setting the desired tension in the spring 58.

At the end of the valve spindle 46 remote from the spacer 44, there is mounted a movable valve member 62 which is held in position by means of a central extension tube 64 extending axially of the body 10.

The spacer 44 and valve spindle 46 are hollow and in communication with the extension tube 64 so as to define a pressure-transmitting passage 65 providing communication between the extension tube 64 and a chamber 66 within the housing part 26 between the diaphragms 38 and 48. As can be seen from the drawing, the extension tube 64 opens into the cavity 18 of the body 10 just upstream of the gas outlet 16. The movable valve member 62 is formed of two parts 62a and 62b which are held together by virtue of being trapped between the spindle 46 and the tube 64 which are in screw-threaded mutual engagement. The part 62b carries valve guides 62c. The valve member 62 is circular and has an O- ring seal 67 in a recess on its outer periphery.It will thus be appreciated that the valve member 62 is mounted on and supported by the diaphragms 38 and 40 so as to be movable therewith along axis X-X.

The valve member 62 also forms part of the removable control unit 24 and cooperates with an annular valve seat 68 forming a further part of the removable control unit 24.

The annular valve seat 68 has an inner peripheral surface of partly frustoconical form which provides a seating surface with which O-ring seal 67 can engage. The annular valve seat 68 has a cylindrical outer peripheral surface which cooperates with the internal annular surface 22 in the body, an O-ring seal 70 serving to seal the joint between these two parts.

The annular valve seat 68 is carried by the mounting ring 32 through the intermediary of three support legs 72 (only one of which is illustrated).

Each support leg 72 has a screw-threaded end portion 72a which is secured in a respective internally screw-threaded blind bore in the valve seat 68. Over its other end region, each leg 72 is of reduced diameter and engages with a definite slight clearance in a respective blind bore 74 in the mounting ring 32. The reduced diameter end region of each leg 72 also has an annular recess 76 therein. The inner periphery of the mounting ring 32 has a groove 78 therein in which is located a partcircular spring clip 80. The groove 78 is of a depth such that it opens into the bores 74 so that the spring clip 80 engages within the recesses 76 of all of the legs 72 to retain these against withdrawal from the respective bores 74. In this particular embodiment, the clearance between the reduced diameter end portion of each pillar 72 and the respective bore 74 is about 0.3 mm all round.Thus, it will be appreciated that the annular valve seat 62 is movable to a limited extent relative to the mounting ring 32 transversely of axis X-X. Such limited extent is sufficient to allow the annular valve seat 68 to align itself accurately within the aperture 22 upon mounting of the control unit 24 on the body 10 so that an effective seal can be achieved between the valve seat 68 and the surface 22 whilst at the same time permitting an effective seal between the mounting ring 32 and the aperture 12, without stressing the respective parts.

The control unit 24 is retained in engagement with the hollow body 10 simply by means of a set of four equi-angularly spaced socket set screws 86 which are engaged in internally screw-threaded, radially extending bores through the hollow body 10 in the region of the stepped aperture 12. Each screw 86 has a conical inner end engaged in an annular recess 88 around the outer periphery of the mounting ring 32. The inner side wall of the recess 88 is inclined so that tightening of the screws 86 serves to urge the mounting ring 32, and thus the whole of the control unit 24, into the desired position relative to the hollow body 10 so that the required seals are maintained. Thus, the servicing purposes, loosening of the screws 86 permits the whole of the control unit 24 including the valve member 62 and the valve seat 68 to be completely removed from the body 10.

The above-described gas flow regulator operates in a manner known per se to maintain a substantially constant gas pressure at the outlet 16. For this reason, the operation of the regulator will not be described in any great detail except to state that the effective area of the secondary diaphragm 48 is equal to the effective area of the valve member 62 so that there is no net force urging the valve member 62 in either axial direction as a result of the action of inlet gas pressure directly on these two parts. The spring 58 acts in a direction to open the valve member 62 relative to the valve seat 68.However, the gas pressure adjacent the outlet 16 and downstream of the valve member 62 acts on the main diaphragm 38 via the tube 64, valve spindle 46 and spacer 44 in opposition to the spring 58 so as to maintain a substantially constant pressure at the outlet 16 irrespective (a) of the demand for gas downstream of the outlet 16 and (b) inevitable slight fluctuations in the pressure of gas supplied to the inlet 14.

In accordance with said second aspect of the present invention, the extension tube 64 is provided at its open or downstream end with a Tpiece 90 having open ends 92 disposed nearer to the wall of the body 10 than to the axis of the latter. This locates the pressure sensing regions in an area of flow downstream of the valve member 62 that is much less prone to turbulence caused by the valve member 62 than is the case where the T-piece 90 is omitted and pressure sensed on the axis of the hollow body by the open end of the tube 64. It is to be appreciated that the T-piece 90 uses the venturi effect to monitor the outlet pressure since gas flow occurs across the open ends 92. This is particularly advantageous at low inlet pressures and enables the regulator to operate satisfactorily under a wider range of inlet pressures.

In the modification illustrated in Fig 2, the extension tube 64 with T piece 90 is omitted and, instead, valve member part 62a is formed with a transversely extending passage therein which defines open ends 92 and which communicates with the interior of valve spindle 46. A domed nut 94 secures the parts 62a and 62b on the spindle 46.

Claims

1. A fluid flow regulator comprising a hollow body having a fluid inlet, a fluid outlet and a fluid flow passage extending between the inlet and the outlet, a valve member mounted in the fluid flow passage for movement relative to a valve seat in order to control flow of fluid through the regulator in use, a diaphragm connected with the valve member so that movement of the diaphragm effects movement of the valve member, a diaphragm chamber, and a pressure-transmitting passage providing communication between the diaphragm chamber and the fluid flow passage, wherein the pressure-transmitting passage has at least one inlet opening into the fluid flow passage in a direction transversely of the direction of fluid flow therepast whereby, in use, the venturi effect is used to monitor the pressure.

2. A regulator as claimed in claim 1, wherein at least a pair of oppositely directed inlets are provided for the pressure-transmitting passage.

3. A regulator as claimed in claim 2, wherein the or each inlet to the pressure-transmitting passage is disposed nearer to the wall of the passage than to the centre.

4. A regulator as claimed in any one of claims 1 to 3, wherein the pressure-transmitting passage opens into the fluid flow passage downstream of the valve member.

5. A regulator as claimed in any one of claims 1 to 4, wherein said at least one inlet is defined by at least one passage in part of the valve member.

6. A regulator as claimed in claim 1, substantially as hereinbefore described with reference to Fig 1 or Figs 1 and 2 of the accompanying drawings.

7. A fluid flow regulator comprising a hollow body having a control unit mounting aperture, a fluid inlet, a fluid outlet and a fluid flow passage extending between the inlet and the outlet; and a control unit which is removably connected to the hollow body, the control unit including (a) mounting means sealingly engaged with the control unit mounting aperture, (b) support means carried by the mounting means and extending into the fluid flow passage, (c) a valve seat carried by the support means so as to be sealed with an internal surface in the body, (d) a valve member mounted in the fluid flow passage for movement relative to the valve seat in order to control flow of fluid through the regulator in use, and (e) control means carried by the mounting means and operably connected with the valve member for controlling movement of the latter relative to the valve seat; wherein the valve seat is mounted on the mounting means by way of the support means so as to be movable to a limited extent relative to the mounting means.

8. A regulator as claimed in claim 7, wherein the support means is loosely mounted relative to the valve seat and/or to the mounting means.

9. A regulator as claimed in claim 7 or 8, wherein the support means comprises a multiplicity of support legs which are engaged with slight clearance in recesses in the mounting means or in the annular valve seat.

10. A regulator as claimed in claim 9, wherein the support legs are retained in the respective recesses by means of a spring clip.

11. A regulator as claimed in any one of claims 7 to 10, wherein a ring seal is disposed between the outer periphery of the valve seat and the internal surface in the body so as to effect sealing between the valve seat and the body.

12. A regulator as claimed in any one of claims 7 to 11, wherein the mounting means has a surface which is engaged within the control unit mounting aperture with a ring seal therebetween.

13. A regulator as claimed in any one of claims 7 to 12, wherein the control means includes a housing which is disposed externally of the hollow body and which is detachably secured to the mounting means.

14. A regulator as claimed in any one of claims 7 to 13, wherein the control means is of the diaphragm-type.

15. A regulator as claimed in any one of claims 7 to 14, wherein the fluid inlet and fluid outlet are mutually inclined.

16. A regulator as claimed in claim 15, wherein the control unit mounting aperture, the fluid outlet and the internal surface are located on a common axis.

1 7. A fluid flow regulator as claimed in any one of claims 7 to 16 further including the features of the regulator as claimed in any one of claims 1 to 6.