Shut down apparatus and method for use with electro-pneumatic controllers

Abstract

A shut down unit for use with an electro-pneumatic controller includes an electronic switch configured to receive to a first signal from a control unit of the electro-pneumatic controller and to convey the first signal to an electro-pneumatic transducer of the electro-pneumatic controller. The electronic switch is further configured to receive a second signal associated with a control signal input and to cause the electronic switch to prevent the conveyance of the first signal to the electro-pneumatic transducer.

1 . A shut down unit for use with an electro-pneumatic controller, comprising: 
 an electronic switch configured to receive a first signal from a control unit of the electro-pneumatic controller and to convey the first signal to an electro-pneumatic transducer of the electro-pneumatic controller, wherein the electronic switch is further configured to receive a second signal associated with a control signal input and to cause the electronic switch to prevent the conveyance of the first signal to the electro-pneumatic transducer.    
   
   
       2 . A shut down unit as defined in  claim 1 , wherein the electronic switch includes one of a transistor and a relay.  
   
   
       3 . A shut down unit as defined in  claim 2 , wherein the transistor includes a gate terminal that is responsive to the second signal.  
   
   
       4 . A shut down unit as defined in  claim 1 , further comprising a comparator configured to compare the second signal to a reference voltage and to prevent the conveyance of the first signal to the electro-pneumatic transducer based on the comparison.  
   
   
       5 . An electro-pneumatic controller, comprising: 
 an electro-pneumatic transducer; and    a shut down unit operatively coupled to the electro-pneumatic transducer and configured to respond to a signal received by the electro-pneumatic controller and to cause the electro-pneumatic transducer to provide a pressure output associated with a shut-down condition when the magnitude of the signal crosses a threshold value.    
   
   
       6 . An electro-pneumatic controller as defined in  claim 5 , wherein the shut down unit includes a comparator configured to compare the signal received by the electro-pneumatic controller to the threshold value and based on the comparison vary a condition of the shut down unit to cause the electro-pneumatic transducer to provide the pressure output associated with the shut-down condition.  
   
   
       7 . An electro-pneumatic controller as defined in  claim 5 , wherein the shut down unit includes a switch configured to respond to the signal provided to the electro-pneumatic controller to cause the electro-pneumatic controller to provide the output pressure associated with the shut-down condition.  
   
   
       8 . An electro-pneumatic controller as defined in  claim 7 , wherein the switch includes one of a transistor and a relay.  
   
   
       9 . An electro-pneumatic controller as defined in  claim 5 , further comprising a selector configured to selectively enable the operation of the shut down unit.  
   
   
       10 . An electro-pneumatic controller as defined in  claim 9 , wherein the selector includes a manually actuated switch.  
   
   
       11 . An electro-pneumatic controller, comprising: 
 a control unit;    a shut down unit communicatively coupled to the control unit; and    an electro-pneumatic transducer communicatively coupled to the shut down unit, wherein the shut down unit is configured to cause an output pressure of the electro-pneumatic transducer to be at a pressure associated with a shut-down condition in response to a value of a control signal received by the electro-pneumatic controller.    
   
   
       12 . An electro-pneumatic controller as defined in  claim 11 , wherein the shut down unit includes a comparator and an electronic switch operatively coupled to the comparator.  
   
   
       13 . An electro-pneumatic controller as defined in  claim 12 , wherein the electronic switch includes one of a transistor and a relay.  
   
   
       14 . An electro-pneumatic controller as defined in  claim 11 , further comprising a shut down selector operatively coupled to the shut down unit and configured to selectively enable the operation of the shut down unit.  
   
   
       15 . A method of shutting down a pneumatically actuated device, comprising: 
 comparing a control signal received by an electro-pneumatic controller to a predetermined value;    interrupting a signal provided by a control unit of the electro-pneumatic controller to an electro-pneumatic transducer;    changing an output pressure provided by the electro-pneumatic controller in response to interruption of the signal to cause the shut down of the pneumatically actuated device.    
   
   
       16 . A method as defined in  claim 15 , wherein interrupting the signal provided by the control unit to the electro-pneumatic transducer includes opening an electrical path between the control unit and the electro-pneumatic transducer.  
   
   
       17 . A method as defined in  claim 15 , wherein interrupting the signal provided by the control unit to the electro-pneumatic transducer includes interrupting the signal only if a shut down selector has been set to an enabling condition.  
   
   
       18 . A method as defined in  claim 15 , wherein changing the output pressure provided by the electro-pneumatic controller includes reducing the output pressure to a substantially zero pressure.  
   
   
       19 . A method as defined in  claim 15 , wherein the pneumatically actuated device includes one of a valve and a damper.