System to control tension in a cable during underground placement

摘要

A tractor provided with a cable reel at one end and a plow at the trailing end includes a system to monitor tension applied to the cable during underground placement. A capstan engages the cable while driven by a hyraulic motor and the pressure of the fluid supply to the motor is monitored by a pressure transducer. An electrical signal from the pressure transducer is fed to a control which also receives a setpoint signal corresponding to a maximum allowable tension on the cable. An output signal from the control is used to slow down or stop advancing movement of the vehicle and a second signal is used to operate a valve to divert fluid pressure from the hydraulic motor. Tension on the cable extending between the capstan and the reel can be monitored as well as tension on the cable between the capstan and the plow.