Actuator with dual drive

Abstract

A manually operated actuator is provided with an over-travel feature. The over-travel feature may be realized with a controlled thread backlash or with a biasing member such as a Belleville spring. When used with a flow control device such as a diaphragm valve, the over-travel feature allows the valve to open and close at actuator positions other than full stop positions. Embodiments for manual actuators and hybrid actuators are presented.

We claim: 
     
         1 . An actuator comprising an actuator stem that is moveable between a first position and a second position, an actuator drive member coupled to said actuator stem to move said actuator stem between said first position and said second position, a biasing member that applies a first force on said actuator stem when said actuator stem is in said first position, said actuator drive member applies a second force on said actuator stem when said actuator stem is in said second position. 
     
     
         2 . The actuator of  claim 1  wherein said actuator stem comprises a first portion and a second portion, and a coupling between said first portion and said second portion, said coupling transfers said first force from said biasing member to said first portion of said actuator stem when said actuator stem is in said first position. 
     
     
         3 . The actuator of  claim 2  wherein said coupling transfers said second force from said actuator drive member to said second portion of said actuator stem when said actuator stem is in said second position. 
     
     
         4 . The actuator stem of  claim 3  wherein said actuator drive member provides a direct drive to said second portion of said actuator stem when said actuator stem is in said second position. 
     
     
         5 . The actuator of  claim 1  wherein said actuator drive member comprises a handle that is rotatable about an axis. 
     
     
         6 . The actuator of  claim 1  in combination with a valve that is operated by movement of said actuator stem. 
     
     
         7 . The actuator of  claim 6  wherein said valve comprises a diaphragm valve. 
     
     
         8 . The actuator of  claim 6  comprising a pneumatic actuator that is operable to open and close said valve. 
     
     
         9 . The actuator of  claim 8  wherein said actuator drive member can be operated to override operation of said pneumatic actuator. 
     
     
         10 . The actuator of  claim 3  wherein said coupling comprises a threaded connection between said biasing member and said first portion of said actuator stem, said threaded connection comprising a controlled thread backlash. 
     
     
         11 . The actuator of  claim 10  wherein said controlled thread backlash causes an over-travel condition between said actuator drive member and said actuator stem position. 
     
     
         12 . The actuator of  claim 1  wherein said biasing member causes an over-travel condition between said actuator drive member and said actuator stem position. 
     
     
         13 . The actuator of  claim 12  wherein said biasing member comprises a biasing member. 
     
     
         14 . The actuator of  claim 1  wherein said actuator stem comprises a first portion and a second portion, and a coupling between said first portion and said second portion, said coupling comprising a threaded connection between said biasing member and said first portion, said threaded connection comprising a controlled thread backlash. 
     
     
         15 . The actuator of  claim 14  wherein said controlled thread backlash causes an over-travel condition between said actuator drive member position and said actuator stem position. 
     
     
         16 . The actuator of  claim 14  in combination with a valve that is operated by movement of said actuator stem. 
     
     
         17 . An assembly of a valve and an actuator that can be connected so that the actuator controls operation of the valve, comprising:
 a valve comprising a valve member having a valve open position and a valve closed position,   said actuator comprising an actuator stem that is moveable between an actuator stem first position that corresponds to said valve open position and an actuator stem second position that corresponds to said valve closed position, an actuator drive member coupled to said actuator stem to move said actuator stem between said actuator stem first position and said actuator stem second position, a biasing member that applies a first force on said actuator stem when said actuator stem is in said actuator stem first position, said actuator drive member applies a second force on said actuator stem when said actuator stem is in said actuator stem second position.   
     
     
         18 . The assembly of  claim 17  wherein said actuator stem is moveable to a third position that provides an over-travel from said valve closed position. 
     
     
         19 . The assembly of  claim 18  wherein said actuator stem is moveable to a fourth position that provides an over-travel from said valve open position. 
     
     
         20 . The assembly of  claim 17  wherein said actuator stem comprises a first portion and a second portion, and a coupling between said first portion and said second portion, said coupling comprising a threaded connection between said biasing member and said first portion, said threaded connection comprising a controlled thread backlash. 
     
     
         21 . The assembly of  claim 17  wherein said biasing member causes an over-travel condition between said actuator drive member and said actuator stem position. 
     
     
         22 . The assembly of  claim 21  wherein said biasing member comprises a spring. 
     
     
         23 . The assembly of  claim 17  wherein said valve comprises a diaphragm valve. 
     
     
         24 . The assembly of  claim 17  wherein said actuator comprises a pneumatic actuator that is operable to move said valve member between said valve open position and said valve closed position. 
     
     
         25 . The assembly of  claim 24  wherein said actuator drive member is manually operable and can be used to override operation of said pneumatic actuator. 
     
     
         26 . The actuator of  claim 2  wherein said second portion of said actuator stem is threadably coupled to an actuator housing and said coupling provides a threaded connection between said first portion of said actuator stem and said second portion of said actuator stem. 
     
     
         27 . The actuator of  claim 26  wherein said second portion of said actuator stem is threadably coupled to the actuator housing with a first thread orientation and said coupling comprises a thread orientation that is opposite said first thread orientation. 
     
     
         28 . The actuator of  claim 20  wherein said second portion of said actuator stem is threadably coupled to an actuator housing and said coupling provides a threaded connection between said first portion of said actuator stem and said second portion of said actuator stem. 
     
     
         29 . The actuator of  claim 28  wherein said second portion of said actuator stem is threadably coupled to the actuator housing with a first thread orientation and said coupling comprises a thread orientation that is opposite said first thread orientation. 
     
     
         30 . An actuator and valve assembly comprising:
 a valve comprising a valve member that can be moved in an axial direction,   an actuator comprising an actuator stem and an actuator drive member, said actuator drive member being manually operable with said actuator stem to move said valve member,   a dual drive coupling for said actuator drive member and said actuator stem that provides greater axial stroke of said actuator stem as compared with axial stroke of said actuator stem without said dual drive coupling.   
     
     
         31 . The assembly of  claim 30  wherein said dual drive coupling comprises a first threaded connection and a second threaded connection, said first threaded connection comprising a first thread orientation and said second threaded connection comprising a second thread orientation that is opposite said first thread orientation. 
     
     
         32 . An actuator comprising an actuator stem that is moveable between a first position and a second position, said actuator stem comprising a first portion and a second portion, an actuator drive member coupled to said actuator stem to move said actuator stem between said first position and said second position, a threaded coupling between said actuator stem first portion and said actuator stem second portion, said threaded coupling comprising a controlled thread backlash. 
     
     
         33 . The actuator of  claim 32  in combination with a flow control device having open and closed positions, wherein said controlled thread backlash provides axial over-travel for one or both of said valve open and closed positions.