GB1598896A

GB1598896A - Fluid actuated valve

Info

Publication number: GB1598896A
Application number: GB18038/78A
Authority: GB
Original assignee: LEZIER A; LEZIER P
Current assignee: LEZIER A; LEZIER P
Priority date: 1977-05-06
Filing date: 1978-05-05
Publication date: 1981-09-23
Also published as: FR2389933A1; CH622111A5; DE2819876A1; FR2389933B1

Abstract

The regulator includes a linear-displacement shutoff unit constituted by a hollow cylindrical piston (9) interacting via its bevelled front edge (21) with an annular seat (10), the bottom (12) of this hollow cylindrical piston being isolated from the high-pressure chamber (5) by a stationary disc (15) integral with the casing (6). The hollow cylindrical piston (9) is controlled by a pressure prevailing in a control chamber (19) and acting on the bottom (12) of the piston, this pressure being a function of a characteristic pressure or of the flow rate of the fluid outflow to be regulated. This regulator is used in installations for distribution and irrigation and allows correct operation within a wide range of flow rates down to flow rates of almost zero. <IMAGE>

Description

(54) FLUID ACTUATED VALVE (71) We, PIERRE LEZIER and ANDRÉ LEZIER of "La Salle", 73290 La Motte Servolex, France, both French Citizens, 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: The invention relates to fluid controls and more particularly to controls for industrial fluid systems.

Various fluid flow control devices are known which control the fluid flow in a fluid system in response to a pressure in the system, for instance a downstream pressure, or in response to differential pressures wihch are dependent on the flow rate of the fluid flow.

Whatever the way the control is carried out, care must be taken of the problems of balancing the obturating valve member in the valve body depending upon the pressure due to flow rate ranges of the fluid to be controlled. Balancing problems are partially solved by making use of double-seated or double-plate valve memers or of additional balancing platens for said valve members in the case of linear lifting valves, or of double perforated cylindrical valve members in rotary valves. Such constrictions result obviously in sophisticated and fragile constructions for the moving parts, whereby not only the fabrication costs but also the risks of failure are increased.

Additionally, depending upon the control mode, the operating range of such valves are either from almost zero flow up to flow rates of about 2 m/second, or in speed ranges about 2 m/second but with a reduced efficiency about zero flow rate. Now, in large scale plants, such as town distributing systems or irrigating sys tems, the flow rates become progressively higher. Moreover, the possibility of regulating fluid systems at low flow rates allows con siderable cost savings.

Electronic thermo control valves have also been developed which show improved efficiency and which can be operated in broader operating ranges. However, such control devices require auxiliary power sources and are expensive both on purchase and on maintenance.

It is an object of the invention to overcome such disadvantages by providing a novel fluid flow control device using as a power source the fluid to be controlled, which may be simply, economically and conveniently constructed to cover a broad range of flow rates, including weak flow rates and zero flow rate.

It would be desirable to provide an improved control device which is not sensitive to the absolute values of the pressures within the fluid to be controlled, which includes a minimum number of movable parts and wherein the mechanical stresses created within said mov able parts are reduced to a minimum extent.

It would also be desirable to provide a control valve which is easy to operate and versatile, and which can be adapted to specific problems raised in designing a fluid flow control device in fluid systems with diversified utilizations parameters.

Accordingly, the present invention provides a control device for use in a fluid system com- prising: a valve body; inlet means for fluid connection to a first element of a fluid system; outlet means for fluid connection to a second element of said fluid system; a shiftable valve member in said valve body, engageable with an annular seat in said valve body, said seat lying in a plane perpendicular to the direction of displacement of said valve member and defining with an annular end portion of said valve member an annular variable restriction area establishing fluid communication between said inlet and outlet means, wherein said valve member consists in a hollow cylindrical piston having a flat rear wall and a cylindrical lateral wall, said lateral wall being uniformly thin relative to the piston diameter and being terminated by a bevelled front annular face opposite to said rear wall, said restriction area being defined between said bevelled. front annular face and said annular seat, said cylin drical piston being slidingly and sealingly received within a cylindrical chamber formed in said valve body, and wherein a stationary disk member is rigidly connected to a portion of said valve body opposite to said cylindrical chamber with respect to said annular seat, said stationary disk being provided with a peri pheral sliding seal for cooperation with the inner cylindrical surface of said cylindrical lateral wall of said cylindrical piston when said piston is moved with respect to said annular seat, a closed inner chamber is whereby defined between said rear wall of said piston and said disk member, means being provided for connecting said cylindrical chamber within which said piston is received to a first pressure which is dependent on a parameter of the fluid to be controlled, means being provided for connect ing said inner chamber to a second pressure, whereby providing for a balanced control piston governed by the said first pressure to auto matically control the fluid in the said fluid system.

The cylindrical hollow shape of the obturat ing valve member thus permits that surface of said valve member which is submitted to pressure variations in the valve to be reduced, only the relatively thin front edge of the obturating cylinder being submitted to the transitory pressure conditions between the upstream and downstream pressure within the control valve.

With the bevelled shape of said front annular face of the cylindrical piston, it is possible on one hand to determine accurately the annular surface of the obturating valve member which is permanently submitted to the upstream pressure between the open and closed positions of the valve member and, on the other hand, to improve the laminar flow of the fluid through the valve in the constriction area between said front edge of the valve member and the seat, thereby making the axial forces exerted on the valve member more independent of the fluid flow.

The stationary disk separates the rear of the cylindrical piston from the stream pressure in the valve body, preferably the upstream pressure, thereby freeing said valve member from the axial forces created by said pressure and providing for said valve member increased displacement flexibility and improved speed response independently of the absolute value of said pressure, even in the case of high upstream pressures. The obturating piston is only submitted to the differential pressures exerted on both sides of its rear face, i.e. the first and second pressures which may both be dependent on the reference pressures in the fluid to be controlled. Such a control device thus ensures a high response control with reduced transitory equilibrium pressure build-up within a flow rate range between 0 m/second up to 6 m/second and over.

Further objects, features and advantages of the invention will become more readily apparent when the following description is read with the accompanying drawings in which: Figure 1 schematically shows a control valve having an hollow cylindrical valve member in accordance with the invention; and Figure 2 schematically shows, at a larger scale, the constriction area between the seat and the valve member of the control valve.

The fluid control device of the invention typically comprises an inlet or supply pipe 1 provided with means for connection to an element of a fluid system, for instance a flange 2, and an outlet pipe 3 also provided with a flange 4 for connection to another element of a fluid system. The supply pipe 1 opens within a first or high pressure chamber 5 formed in the lower part of the valve body, said body being generally designated by reference numeral 6. Said first chamber 5 communicates with a second annular chamber 7 or low pressure chamber in the valve body through a cylindrical throat 8 and an annular constriction zone between a linearly shiftable obturating member 9 and an annular seat 10 lying in a plane substantially perpendicular to the axis of the cylindrical throat 8, said annular seat having an inner diameter greater than the diameter of said throat.

The linearly shiftable valve member 9 consists in an hollow cylindrical piston having a cylindrical longitudinally extending lateral wall 11 and a flat rear wall 12, the valve member 9 being in a concentric position with the throat 8 and adapted for sliding movements along its symmetric axis in the body 6 with the outer surface 14 of its lateral wall 11 in sliding contact with a stationary annular seal 13 mounted in the body 6. A stationary disk 15, rigidly mounted on the body 6, for instance by means of a stem 16, is received within the cylindrical hollow valve member 9 with its symmetry axis in the prolongation of the symmetery axis of said valve member, the outer diameter of the disk 15 being slightly lesser than the inner diameter of the cylindrical hollow piston 9 as defined by the inner surface 17 of its longitudinally extending lateral wall 11.The cylindrical piston 9 is adapted to move slidingly and sealingly with respect to the stationary disk 15, a sliding annular seal 18 being mounted on the periphery of the stationary disk 15.

In addition to the high pressure or stabilization chambers 5 and to the annular low pressure chamber 7, the valving device of the invention comprises a variable size upper or control chamber 19 in which the valve member 9 is slidingly received, i.e. defined between the upper face of the rear wall 12 of the cylindrical piston 9 and the upper part of the valve body and a variable size equalizing chamber 20 defined between the inner face of the rear wall 12 of the cylindrical piston 9 and the upper face of the stationary disk 15.

The annular front face of the longitudinally extending lateral wall 11 of the cylindrical piston 9 has a bevelled surface 21 which forms an acute angle with the inner surface 17 of the cylindrical piston 9, whereby the junction be tween said inner surface 17 and the outer surface 14 is constituted by a circular outer edge 22 having the same diameter as the internal diameter of the longitudinally extending lateral wall 11 of the cylindrical piston 9.

With such an arrangement, the constriction area between the high pressure zones and the low pressure zones in the control valve is accurately defined between the plane of the circular edge 22 and the plane of the upper surface of the annular seat 10 in the valve body.

An improved laminar flow is thereby achieved in the constriction area, as illustrated by the arrows on Figure 2. Additionally uncontrolled variations of the surface of the cylindrical piston submitted to the upstream pressure between the open and closed positions of the valve member are prevented, since said surface is substantially limited to the edge 22 of the front face of the cylindrical piston, the bevelled face 21 of the cylindrical piston being generally permanently submitted integrally to the downstream fluid pressure within the annular chamber 7 owing to the laminar pressure drop in the constriction area between the edge 22 and the annular seat 10.The rear wall 12 of the cylindrical piston 9 is separated from the high pressure within the inlet chamber 5 by the stationary disk 15 and from the low pressure within the annular or outlet chamber 7 by the seal 13, whereby the cylindrical piston 9 is prevented from being submitted to any axial force created by said pressures, the forces exerted on the longitudinally extending lateral wall 11 of cylindrical piston 9 being balanced due to the cylindrical symmetery of said valve member, whereby the possibilities of displace ment of said valve member along its symmetry axis are not affected.

The control of displacement, e.g. of position, of the obturating valve member 9 in response to reference parameters of the flowing fluid is achieved by the pressure within the control chamber 19. Said chamber 19 comprises an opening 23 which is connectable, for instance by a pipe 24 shown in dotted lines, either to a pressure port located in a zone of the fluid system where the fluid pressure is to be con trolled, for instance the downstream pressure in the outlet pipe 3, or to any other pressure source dependent on a characteristic pressure of the flowing fluid to be controlled.Assuming that the pipe 24 is connected to a pressure port downstream the control valve, any variation of the fluid flow in the fluid system results in a variation of said downstream pressure, and said pressure variation results in turn in a determined displacement of the obturating valve member 9 which modifies the area of the construction area so as to counterbalance said variation of the downstream pressure. The obturating valve member 9 is advantageously permanently biased by a mechanical biasing means, for instance a calibrated spring 25, the biasing force being transmitted to the valve member by a stem 26 secured to the rear wall 12, said stem passing through the upper wall of the chamber 19, a seal 27 being interposed therebetween.Instead of a spring 25, a counterweight assembly may be provided for balancing the force exerted on the obturating valve member 9 by the fluid under pressure in the control chamber 19. For achieving an improved balancing, the equalizing chamber 20 is connected through an opening 28 and a conduit 29, extending for instance through the stem 16, either to the surrounding atmosphere or to a source of gas under pressure, depending upon the average value of the control pressure in the control chamber 19.

In an alternative embodiment, for having the control device of the invention acting as a flow regulator, the conduits 24 and 29 of the chambers 19 and 20, respectively, may be connected to pressure ports of a flow metering device such as a venturi or restrictor, disposed in a portion of the fluid system to be controlled so as to displace the valve member 9 in response to pressure variations resulting from a variation in fluid flow rate.

In order to prevent high flow rates provoking in the constriction area, more particularly due to their laminar characteristics, abnormal wear of the seat 10, for instance due to cavitation effects, the annular seat is mounted in its receiving groove 30 so that the upper annular face 31 of the seat lies in a plane substantially offset from the plane 32 of the downstream edge of the throat 8 in the surrounding body portion where the groove 30 is formed, whereby the constriction area is defined between said plane 32 and the edge 22 of the obturating valve member 9.

The invention is not limited to the particular details of constructions as illustrated, and it is contemplated that other modifications and applications will occur to those skilled in the art. It is intended that the claims shall cover such modifications and applications that do not depart from the scope of the invention.

WHAT WE CLAIM IS: 1. A control device for use in a fluid system comprising: a valve body; inlet means for fluid connection to a first element of a fluid system; outlet means for fluid connection to a second element of said fluid system; a shiftable valve member in said valve body, engageable with an annular seat in said valve body, said seat lying in a plane perpendicular to the direction of displacement of said valve member and defining with an annular end portion of said valve member an annular variable restriction area establishing fluid communication between said inlet and outlet means, wherein said valve member consists in a hollow cylindrical piston having a flat rear wall and a cylindrical lateral wall, said lateral wall being

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. tween said inner surface 17 and the outer surface 14 is constituted by a circular outer edge 22 having the same diameter as the internal diameter of the longitudinally extending lateral wall 11 of the cylindrical piston 9. With such an arrangement, the constriction area between the high pressure zones and the low pressure zones in the control valve is accurately defined between the plane of the circular edge 22 and the plane of the upper surface of the annular seat 10 in the valve body. An improved laminar flow is thereby achieved in the constriction area, as illustrated by the arrows on Figure 2. Additionally uncontrolled variations of the surface of the cylindrical piston submitted to the upstream pressure between the open and closed positions of the valve member are prevented, since said surface is substantially limited to the edge 22 of the front face of the cylindrical piston, the bevelled face 21 of the cylindrical piston being generally permanently submitted integrally to the downstream fluid pressure within the annular chamber 7 owing to the laminar pressure drop in the constriction area between the edge 22 and the annular seat 10.The rear wall 12 of the cylindrical piston 9 is separated from the high pressure within the inlet chamber 5 by the stationary disk 15 and from the low pressure within the annular or outlet chamber 7 by the seal 13, whereby the cylindrical piston 9 is prevented from being submitted to any axial force created by said pressures, the forces exerted on the longitudinally extending lateral wall 11 of cylindrical piston 9 being balanced due to the cylindrical symmetery of said valve member, whereby the possibilities of displace ment of said valve member along its symmetry axis are not affected. The control of displacement, e.g. of position, of the obturating valve member 9 in response to reference parameters of the flowing fluid is achieved by the pressure within the control chamber 19. Said chamber 19 comprises an opening 23 which is connectable, for instance by a pipe 24 shown in dotted lines, either to a pressure port located in a zone of the fluid system where the fluid pressure is to be con trolled, for instance the downstream pressure in the outlet pipe 3, or to any other pressure source dependent on a characteristic pressure of the flowing fluid to be controlled.Assuming that the pipe 24 is connected to a pressure port downstream the control valve, any variation of the fluid flow in the fluid system results in a variation of said downstream pressure, and said pressure variation results in turn in a determined displacement of the obturating valve member 9 which modifies the area of the construction area so as to counterbalance said variation of the downstream pressure. The obturating valve member 9 is advantageously permanently biased by a mechanical biasing means, for instance a calibrated spring 25, the biasing force being transmitted to the valve member by a stem 26 secured to the rear wall 12, said stem passing through the upper wall of the chamber 19, a seal 27 being interposed therebetween.Instead of a spring 25, a counterweight assembly may be provided for balancing the force exerted on the obturating valve member 9 by the fluid under pressure in the control chamber 19. For achieving an improved balancing, the equalizing chamber 20 is connected through an opening 28 and a conduit 29, extending for instance through the stem 16, either to the surrounding atmosphere or to a source of gas under pressure, depending upon the average value of the control pressure in the control chamber 19. In an alternative embodiment, for having the control device of the invention acting as a flow regulator, the conduits 24 and 29 of the chambers 19 and 20, respectively, may be connected to pressure ports of a flow metering device such as a venturi or restrictor, disposed in a portion of the fluid system to be controlled so as to displace the valve member 9 in response to pressure variations resulting from a variation in fluid flow rate. In order to prevent high flow rates provoking in the constriction area, more particularly due to their laminar characteristics, abnormal wear of the seat 10, for instance due to cavitation effects, the annular seat is mounted in its receiving groove 30 so that the upper annular face 31 of the seat lies in a plane substantially offset from the plane 32 of the downstream edge of the throat 8 in the surrounding body portion where the groove 30 is formed, whereby the constriction area is defined between said plane 32 and the edge 22 of the obturating valve member 9. The invention is not limited to the particular details of constructions as illustrated, and it is contemplated that other modifications and applications will occur to those skilled in the art. It is intended that the claims shall cover such modifications and applications that do not depart from the scope of the invention. WHAT WE CLAIM IS:

1. A control device for use in a fluid system comprising: a valve body; inlet means for fluid connection to a first element of a fluid system; outlet means for fluid connection to a second element of said fluid system; a shiftable valve member in said valve body, engageable with an annular seat in said valve body, said seat lying in a plane perpendicular to the direction of displacement of said valve member and defining with an annular end portion of said valve member an annular variable restriction area establishing fluid communication between said inlet and outlet means, wherein said valve member consists in a hollow cylindrical piston having a flat rear wall and a cylindrical lateral wall, said lateral wall being

uniformly thin relative to the piston diameter and being terminated by a bevelled front annular face opposite to said rear wall, said restriction area being defined between said bevelled front annular face and said annular seat, said cylindrical piston being slidingly and sealingly received within a cylindrical chamber formed in said valve body, and wherein a stationary disk member is rigidly connected to a portion of said valve body opposite to said cylindrical chamber with respect to said annular seat, said stationary disk being provided with a peripheral sliding seal for cooperation with the inner cylindrical surface of said cylindrical lateral wall of said cylindrical piston when said piston is moved with respect to said annular seat, whereby a closed inner chamber is defined between said rear wall of said piston and said disk member, means being provided for connecting said cylindrical chamber within which said piston is received to a first pressure which is dependent on a parameter of the fluid to be controlled, means being provided for connecting said inner chamber to a second pressure, whereby providing for a balanced control piston governed by the said first pressure to automatically control the fluid in the said fluid system.

2. A control device according to claim 1, wherein said hollow cylindrical piston is biased by a return means acting in a direction opposite to the force exerted onto said cylindrical piston and created by said first pressure.

3. A control device according to claim 1 or 2, wherein said second pressure depends on the flow rate of the flowing fluid to be controlled.

4. A control device according to claim 3, wherein said first and second pressures are differential pressures which depend on the flow rate of the flowing fluid to be controlled.

5. A control device according to any of claims 1 to 4, wherein said bevelled front annular face defines for said piston an outer circular edge of a diameter equal to the inner diameter of said cylindrical lateral wall of said piston.

6. A control device according to any of claims 1 to 5, wherein said annular seat is disposed within a recess in the valve body in such a manner that the face of the seat which cooperates with the edge of the bevelled face of the hollow cylindrical piston is slightly offset from the plane defined by the edges of said recess.

7. A control device substantially as des cribbed with reference to the appended drawings.