Head brake release with memory and method of controlling a drill head

摘要

A control is provided for a drill head that is mounted on a drill mast. Hydraulic motors raise and lower the drill head and a hydraulically releasable brake holds the drill head in position on the mast. The control has a hoist line that connects the hydraulic motors to a source of hydraulic fluid under pressure. A brake release line is connected to the brake and a brake release valve normally connects the brake release to a tank. The brake release valve is electrically actuated to connect the brake release line to a source of hydraulic fluid under pressure to release the brake. A programmable logic controller with a memory storage controls the actuation of the brake release valve. A pressure transducer is connected to the hoist line and to the controller for providing a signal to the controller representative of the hoist line pressure and this signal is storable in the memory. The controller will actuate the brake release valve only after the hoist line pressure sensed by the transducer is as great as the pressure stored in memory. The control also includes a brake switch connected to the controller and actuated to set and release the brake. A timer in the controller is turned on for a predetermined time when the brake switch is actuated to set the brake, and the timer prevents the controller from actuating the brake release valve until the timer is turned off. While the timer is on, the existing hoist line pressure signals are stored in the memory. The controller ignores the pressure stored in memory when the mast is at a near horizontal angle as sensed by a mast angle sensor.