Apparatus and method for determining torque, presenting digital torque readout and automatic cycling and termination of wrench operation in a torque wrench system

Apparatus for automatic cycling and termination of operation of a fluid powered torque wrench supplied with operating fluid from a pump, including:

• flow control valve means between the pump and said wrench to direct pressurized fluid to said wrench to advance or retract said wrench;
• first valve control means connected to said flow control valve means to position said flow control valve means in either a null position or an advance position to deliver pressurized fluid to said wrench to advance said wrench;
• second valve control means connected to said flow control valve means to position said flow control valve means to either a null position or a retract position to deliver pressurized fluid to said wrench to retract said wrench;
• first control means for selecting a desired level of torque to be applied to a fastening element by the torque wrench and generating a first signal commensurate with a cut off pressure level of fluid supplied to said wrench which is commensurate with said desired level of torque;
• second control means connected to said first control means to receive said first signal from said first control means commensurate with said desired level of torque, said second control means being connected to operate said first and second valve control means and operating in response to an appropriate signal to operate said first valve control means to position said flow control valve means to deliver pressurized fluid to advance said wrench to tighten a fastener;
• pressure sensing means for sensing the pressure level of fluid delivered to said pump and generating a second signal commensurate with the torque imposed on a fastening element by said wrench;
• comparator means to compare said second signal with a series of pressure level signals from said second control means and generating a third signal to said second control means when the pressure in said pump equals a pressure level signal from said second control means;
• said first signal to said second control means establishing a cut off level, and said second control means functioning to operate said first valve control means to position said flow control valve means in a null position when said third signal from said comparator means is commensurate with the pressure in said pump being equal to said cut off pressure level;
• and
• said first control analyzing the pressure history of the tightening cycle of operation of the wrench to either terminate the tightening operation or cause said second control means to first operate said second valve control means to position said flow control valve means to deliver pressurized fluid to said wrench to retract said wrench and then operate said second valve control means to position said flow control valve means in a null position and then operate said first valve control means to position said flow control valve means to deliver pressurized fluid to said wrench for another cycle of operation to tighten the fastener.

A method for automatic cycling and termination of operation of a fluid powered torque wrench supplied with operating fluid from a pump, including the steps of:

• selecting in a first control means a desired level of torque to be applied to a fastening element by the torque wrench;
• delivering to a second control means connected to said first control means a first signal from said first control means commensurate with said desired level of torque to initiate a tightening cycle of operation of the wrench;
• monitoring the pressure of the operating fluid in said wrench and generating a second signal commensurate with the torque imposed on a fastening element by said wrench;
• comparing said first and second signals and delivering a third signal to said second control means to interrupt the operation of the wrench;
• and
• analyzing in said first control means the pressure history of the tightening cycle of operation of the wrench to initiate another cycle of tightening operation or terminate the tightening operation.