Double-door gating safety protection device for a hydraulic power tong

Abstract

A power tong is disclosed for gripping a pipe, the power tong comprising: a frame with a pair of arcuate portions that define both an axial pipe passage and a throat for receiving a pipe laterally into the axial pipe passage; a hydraulic motor for rotating the pipe; a pair of doors for restricting access to the throat, each door mounted to a respective arcuate portion; a valve housing with an inlet port, an outlet port, a fluid chamber, and a valve member, the outlet port being connected to supply hydraulic fluid to the hydraulic motor; and a pair of valve actuators, each valve actuator responsive to the position of a respective door to operate the valve member to reduce fluid pressure through the outlet port when one or both doors are out of a closed position.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A power tong for gripping a pipe, the power tong comprising:
 a frame with a pair of arcuate portions that define both an axial pipe passage and a throat for receiving a pipe laterally into the axial pipe passage;   a hydraulic motor for rotating the pipe;   a pair of doors for restricting access to the throat, each door mounted to a respective arcuate portion;   a valve housing with a fluid chamber, an inlet port, an outlet port, and a valve member, the outlet port being connected to supply hydraulic fluid to the hydraulic motor; and   a pair of valve actuators, each valve actuator responsive to the position of a respective door to operate the valve member to reduce fluid pressure through the outlet port when one or both doors are out of a closed position.   
     
     
         2 . The power tong of  claim 1  in which the valve housing comprises a return port connected to bypass the hydraulic motor, in which the valve member diverts flow to the return port when one or both doors are out of the closed position. 
     
     
         3 . The power tong of  claim 2  in which the valve member comprises a pair of valve members, with each valve actuator responsive to the position of a respective door to operate a respective valve member to divert flow to the return port when the respective door is out of the closed position. 
     
     
         4 . The power tong of  claim 3  in which the valve members restrict flow to the return port when both doors are in the closed position. 
     
     
         5 . The power tong of  claim 4  in which:
 when one door is out of the closed position and the other door is in the closed position, the inlet port communicates with the outlet port and the return port; and 
 when both of the pair of doors are out of the closed position, fluid communication is cut off between the inlet port and the outlet port. 
 
     
     
         6 . The power tong of  claim 3  in which each valve member has a first sealing member and a second sealing member, and the fluid chamber defines a first zone, a second zone, and a third zone, with the first zone communicating with the inlet port, the second zone communicating with the outlet port, and the third zone communicating with the return port, in which, for each valve member:
 the first sealing member regulates fluid flow between the first zone and the second zone; 
 the second sealing member regulates fluid flow between the first zone and the third zone; 
 when the respective door is in the closed position, the first sealing member is unseated and the second sealing member is seated; and 
 when the respective door is out of the closed position, the first sealing member is seated and the second sealing member is unseated. 
 
     
     
         7 . The power tong of  claim 6  in which the fluid chamber comprises a pair of conduits that each connect the first zone, the second zone, and the third zone, and each valve member is disposed for axial movement within a respective conduit, with each respective conduit forming a first restriction surface for seating the first sealing member, and a second restriction surface for seating the second sealing member. 
     
     
         8 . The power tong of  claim 7  in which each of the first restriction surfaces and the second restriction surfaces form cylinders in which the first sealing members and second sealing members, respectively, are shaped to reciprocate. 
     
     
         9 . The power tong of  claim 7  in which each valve member forms a spool valve. 
     
     
         10 . The power tong of  claim 3  in which each valve member forms a gate valve. 
     
     
         11 . The power tong of  claim 1  in which the valve member comprises a pair of valve members, with each valve actuator responsive to the position of a respective door to operate a respective valve member to reduce fluid pressure through the outlet port when the respective door is out of the closed position. 
     
     
         12 . The power tong of  claim 1  in which each valve actuator connects by mechanical linkage to a respective door. 
     
     
         13 . The power tong of  claim 12  in which each mechanical linkage comprises a push and pull cable system. 
     
     
         14 . A method of operating the power tong of  claim 1 . 
     
     
         15 . The method of  claim 14  further comprising:
 closing the pair of doors; and 
 supplying hydraulic fluid through the valve housing to the hydraulic motor to grip and rotate a pipe within the axial pipe passage.