Patent ID: 6112832
Filing Date: 2000-09-05
Classification: E21B

Abstract:
A method for measuring pulses acting against a drill bit during the drilling of rock by a drilling machine comprising a frame, a percussion piston provided in the frame and reciprocable in a longitudinal direction thereof, a shank arranged in front of the piston to receive percussive impacts therefrom, and a secondary piston arrangement comprising at least one secondary piston that is provided in the frame movably in the axial direction thereof, the secondary piston arrangement arranged to act forwardly on the shank to push the shank forwardly in response to a pressure medium acting on a rear surface of the secondary piston, whereby during the drilling the pressure of said pressure medium is such that the total force of the secondary piston arrangement acting on the shank and pushing it forward exceeds the feed force acting on the drilling machine during the drilling, so that as the shank rests against the secondary piston arrangement it is situated at its optimum point of impact, the method comprising the steps of:A) imparting percussive impacts from the percussion piston to the shank during a rock drilling operation to cause return pulses to be reflected back to the secondary piston arrangement, while the secondary piston is acted upon by the pressure medium;B) measuring a pressure of the pressure medium behind the secondary piston arrangement during step A; andC) detecting the return pulses in the form of pressure pulses sensed in the pressure medium during step B.