Actuator e.g. lift pad, operating apparatus for e.g. drill head, has actuator controlling earth working device, where working device is configured to advance along predefined drilling route

摘要

The apparatus has an actuator (1) e.g. lift pad, controlling an earth working device e.g. drill head. A valve assembly operates the actuator by utilizing pressure of a drilling fluid e.g. bentonite, where the valve assembly has a set of seat valves (3, 6, 8) actuated by a camshaft of the valve assembly. The working device is configured to advance along a predefined drilling route, and an expansion tool of the device corrects an advance of the earth working device. A drilling liquid pump (7) is switched on to build up the pressure in the actuator to raise the actuator. Independent claims are also included for the following: (1) a drilling or flushing medium for use in an operation of an actuator (2) a method for operating an actuator for controlling an earth working device.