Patent ID: 7861641

Claim:
Impulse generator for a rock breaking tool, the impulse generator ( 2 ) comprising a main chamber ( 4 ) for receiving a first pressurizeable fluid volume ( 6 ), and an impulse piston ( 8 ) received in the main chamber ( 4 ) and arranged for transfer of pressure energy in the fluid volume ( 6 ) into impulses in the tool ( 10 ), and a prepressurizing chamber( 12 ) situated on the side of the impulse piston opposite the main chamber for receiving a second pressurizeable fluid volume ( 14 ), wherein the impulse generator ( 2 ) further comprises a pressure relief chamber ( 16 ) situated on the side of the impulse piston opposite the main chamber for receiving a third pressurizeable fluid volume ( 18 ), wherein the relationship between the pressurizing pressures in the fluid volume ( 6 , 14 , 18 ) and the relationship between the areas of the impulse piston ( 8 ) facing the chambers ( 4 , 12 , 16 ) are such that pressurizing of at least the prepressurizing chamber ( 12 ) displaces the impulse piston ( 8 ) in the direction towards the main chamber ( 4 ), the pressure in the main chamber ( 4 ) moving said impulse piston in a direction towards said prepressurizing and pressure relief chambers for increasing the pressure in the pressure relief chamber ( 16 ) when the prepressurizing chamber ( 12 ) is depressurized, and thereafter transferring a pressure impulse into the tool ( 10 ) when the pressure relief chamber ( 16 ) is thereafter depressurized.