Patent ID: 7891437
Filing Date: 2011-02-22
Classification: E21B

Abstract:
1. A method for breaking rock to be drilled in rock drilling, in which method the rock to be drilled is subjected to successive stress pulses by using the pressure of a pressure fluid via a tool in such a way that the energy of the stress wave transmitted from the tool to the rock causes the rock to be broken, wherein the stress waves being generated by subjecting the tool periodically to compressive force so that the compressive force generates a stress wave in the tool, the compressive force being generated by causing the pressure of the pressure fluid to directly or indirectly affect the end of the tool for the period of time of generating the stress pulse in such a way that the force generated by the pressure compresses the tool, the stress pulses being exerted on the rock at a high frequency and by a load proportion of at least 0.075, wherein the load proportion is determined based on the frequency and the length of time to which the compressive force is applied to the tool during each application of the compressive force, wherein the frequency of the stress waves is at least 250 Hz and the amplitude of the stress waves is at least 25 MPa.