Valve actuator

Abstract

A fluid pressure operated actuator assembly comprising a tubular body ( 110 ) having a wall, with an interior surface and an exterior surface and enclosing a main passage ( 112 ) which extends generally parallel to a longitudinal axis of the tubular body, an actuator ( 118 ) located in and movable along the main passage, a first direction chamber ( 138 a ) formed between the wall of the tubular body and the actuator, and at least one second direction chamber ( 138 b, c ) formed between the tubular body and the actuator, wherein the assembly is configured such that when the pressure of fluid in the first direction chamber exceeds the pressure of fluid in the or each second direction chamber by a predetermined amount, the pressure of fluid in the first direction chamber exerts a force on the actuator which acts to push the actuator in a first direction relative to the tubular body, and when the pressure of fluid in the or at least one of the second direction chamber(s) exceeds the pressure of fluid in the first direction chamber by a predetermined amount, the pressure of fluid in the second direction chamber(s) exerts a force on the actuator which acts to push the actuator in a second direction relative to the tubular body, characterised in that the exterior surface of the tubular body is provided with a first port ( 140 a ) which communicates with a passage ( 139 a ) extending through the wall of the tubular body from the first port to the first direction chamber, a second port ( 140 b ) which communicates with a passage ( 139 b ) extending through the wall of the tubular body from the second port to the or one of the second direction chamber(s), and a third port ( 140 c ) which communicates with a passage ( 139 c ) extending through the wall of the tubular body from the third port to the or another one of the second direction chamber(s), the first port lying on a first plane, the second port lying on a second plane and the third port lying on a third plane, the first plane, second plane and third plane being generally parallel to one another and the first plane lying between the second plane and the third plane.

1 - 26 . (canceled) 
     
     
         27 . A fluid pressure operated actuator assembly comprising:
 a tubular body having a wall, with an interior surface and an exterior surface and enclosing a main passage which extends generally parallel to a longitudinal axis of the tubular body;   an actuator located in and movable along the main passage;   a first direction chamber formed between the wall of the tubular body and the actuator; and   at least one second direction chamber formed between the tubular body and the actuator,   wherein the assembly is configured such that when the pressure of fluid in the first direction chamber exceeds the pressure of fluid in the or each second direction chamber by a predetermined amount, the pressure of fluid in the first direction chamber exerts a force on the actuator which acts to push the actuator in a first direction relative to the tubular body, and when the pressure of fluid in the or at least one of the second direction chamber(s) exceeds the pressure of fluid in the first direction chamber by a predetermined amount, the pressure of fluid in the second direction chamber(s) exerts a force on the actuator which acts to push the actuator in a second direction relative to the tubular body, and   wherein the exterior surface of the tubular body is provided with a first port which communicates with a passage extending through the wall of the tubular body from the first port to the first direction chamber, a second port which communicates with a passage extending through the wall of the tubular body from the second port to the or one of the second direction chamber(s), and a third port which communicates with a passage extending through the wall of the tubular body from the third port to the or another one of the second direction chamber(s), the first port lying on a first plane, the second port lying on a second plane and the third port lying on a third plane, the first plane, second plane and third plane being generally parallel to one another and the first plane lying between the second plane and the third plane.   
     
     
         28 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the longitudinal axis of the tubular body extends generally normal to the first plane, second plane and third plane. 
     
     
         29 . The fluid pressure operated actuator assembly according to  claim 27 , wherein one or both of the first and second directions is/are generally parallel to the longitudinal axis of the tubular body. 
     
     
         30 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the first direction is generally opposite to the second direction. 
     
     
         31 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the actuator is connected to a main valve member in such a way that movement of the actuator in the first direction and second direction causes the valve member to move. 
     
     
         32 . The fluid pressure operated actuator assembly according to  claim 31 , wherein the main valve member is movable between a closed position in which the main valve member closes the main passage of the tubular body and an open position in which the main passage of the tubular body is open. 
     
     
         33 . The fluid pressure operated actuator assembly according to  claim 31 , wherein the main valve member moves to the closed position when the actuator moves in the first direction and to the open position when the actuator moves in the second direction. 
     
     
         34 . The fluid pressure operated actuator assembly according to  claim 31 , wherein the actuator is connected to a main valve member by means of a track and pin arrangement whereby a pin extends from on of the valve member or actuator into a slot or groove provided in the other of the valve member or actuator, the pin moving along the slot or groove as the actuator slides in the tubular body and the valve member rotates. 
     
     
         35 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the tubular body is provided with a side passage which extends through the wall of the tubular body from the exterior of the tubular body into the main passage, and the actuator is movable between a closed position in which the actuator substantially prevents flow of fluid along the side passage, and an open position in which flow of fluid along the side passage is permitted. 
     
     
         36 . The fluid pressure operated actuator assembly according to  claim 35 , wherein movement of the actuator in the first direction brings the actuator into the open position, and movement of the actuator in the second direction brings the actuator into the closed position. 
     
     
         37 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the passage from the third port connects to the passage from the second port into the or one of the second direction chamber(s). 
     
     
         38 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the first direction chamber and the or each second direction chamber are formed in a space between an exterior surface of the actuator and an interior surface of the wall of the tubular body. 
     
     
         39 . The fluid pressure operated actuator assembly according to  claim 38 , wherein this space is divided into the first direction chamber and second direction chamber by means of a seal which substantially prevents flow of fluid between the chambers whilst allowing the actuator to move along the main passage of the tubular body. 
     
     
         40 . The fluid pressure operated actuator assembly according to  claim 38 , wherein this space is divided into the first direction chamber and two second direction chambers by means of a seal arrangement which substantially prevents flow of fluid between the chambers whilst allowing the actuator to move along the main passage of the tubular body. 
     
     
         41 . The fluid pressure operated actuator assembly according to  claim 40 , wherein the first direction chamber located between the two second direction chambers. 
     
     
         42 . The fluid pressure operated actuator assembly according to  claim 40 , wherein the passages from the first port, second port and third port into their respective chamber extend through the tubular body generally perpendicular to its longitudinal axis. 
     
     
         43 . The fluid pressure operated actuator assembly according to  claim 40 , wherein at least one of the passages from the first port, second port and third port into their respective chamber extends through the tubular body generally at an angle of less than 90° to its longitudinal axis. 
     
     
         44 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the actuator assembly is configured such that if the pressure in the first direction chamber equals the pressure in the or both second direction chamber(s), there is no net force acting on the actuator, if the pressure in the first direction exceeds the pressure in the or both the second direction chamber(s), there is a net force acting on the actuator pushing the actuator in the first direction, and if the pressure in the first direction chamber is less than the pressure in the or either one of the second direction chamber(s), there is a net force acting on the actuator pushing the actuator the second direction. 
     
     
         45 . The fluid pressure operated actuator assembly according to  claim 27 , wherein the actuator assembly is configured such that when the pressure in the first direction chamber equals the pressure in the or both second direction chamber(s), there is a net force acting on the actuator. 
     
     
         46 . The fluid pressure operated actuator assembly according to  claim 45 , wherein the actuator assembly is configured such that this net force tends to push the actuator in the second direction.