Impulse generator and method for impulse generation

1. 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.

2. Impulse generator as claimed in claim 1 , wherein the main chamber ( 4 ) is under an essentially constant pressure.

3. Impulse generator as claimed in claim 2 , including a pressure source ( 5 ) inside or outside the impulse generator ( 2 ) for establishing said essentially constant pressure.

4. Impulse generator as claimed in claim 1 , wherein the area of the impulse piston ( 8 ) towards the main chamber ( 4 ) is larger than the area of the impulse piston ( 8 ) towards the pressure relief chamber ( 16 ).

5. Impulse generator as claimed in claim 1 , wherein a control device ( 20 ) controls depressurization of the pressure relief chamber ( 16 ).

6. Impulse generator as claimed in claim 5 , wherein said control device comprises means for controlling the extent to which the control valve ( 20 ) is opened.

7. Impulse generator as claimed in claim 6 , wherein the control valve ( 20 ) comprises at least one opening ( 22 ) for controlling said depressurization by discharge of a pressure medium ( 18 ) contained in the pressure relief chamber ( 16 ) during operation.

8. Impulse generator as claimed in claim 7 , wherein the control valve ( 20 ) comprises several openings ( 22 ).

9. Impulse generator as claimed in claim 5 , wherein said control device comprises means for controlling said depressurization by controlling a throttle valve connectable to the pressure relief chamber.

10. Impulse generator as claimed in claim 1 , wherein said pressure relief chamber ( 16 ) comprises several outlets, said outlets being arranged to be opened in a controllable manner, said depressurization being controllable by opening and closing of one or more of said several outlets.

11. Impulse generator as claimed in claim 10 , wherein said outlets have different diameters.

12. Impulse generator as claimed in claim 11 , wherein said outlets are connected to one or more reservoirs ( 24 ) with one or more flow paths, wherein said reservoirs ( 24 ) in operation can be pressurized to different pressures, whereby a step-by-step and/or a continuous depressurization of the pressure relief chamber can be obtained by opening of said outlets.

13. Impulse generator as claimed in claim 10 , wherein said outlets are connected to one or more reservoirs ( 24 ) with one or more flow paths, wherein said reservoirs ( 24 ) in operation can be pressurized to different pressures, whereby a step-by-step and/or a continuous depressurization of the pressure relief chamber can be obtained by opening of said outlets.

14. Impulse generator as claimed in claim 1 , wherein the main chamber ( 4 ) has a circular cross-section.

15. Impulse generator as claimed in claim 1 , wherein the main chamber ( 4 ), the prepressurizing chamber ( 12 ), and the pressure relief chamber ( 16 ) are adapted to receiving fluid volume from a fluid from the group: water, silicone oil, hydrolic oil, mineral oil, and non-combustible hydraulic fluid.

16. Method for generation of impulses in 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 ) which is 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 ),

the steps of said method comprising,

pressurizing the prepressurizing chamber ( 12 ) for moving the impulse piston ( 8 ) in a direction towards the main chamber ( 4 ),

pressurizing the pressure relief chamber ( 16 ),

thereafter depressurizing the prepressurizing chamber ( 12 ) whereby the pressure in the main chamber ( 4 ) effects the impulse piston ( 8 ) so that the pressure in the pressure relief chamber ( 16 ) is further increased, and

thereafter depressurizing the pressure relief chamber ( 16 ) whereby a pressure impulse is transferred into the tool ( 10 ).

17. Method as claimed in claim 16 , further comprising the step of controlling the depressurization in said pressure relief chamber ( 16 ).

18. Method for generation of impulses in 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 ) which is 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 area of the impulse piston towards the main chamber ( 4 ) is smaller than the sum of the areas of the impulse piston ( 8 ) towards the prepressurizing chamber ( 12 ) and the pressure relief chamber ( 16 ) but larger than the area of the impulse piston ( 8 ) towards the pressure relief chamber ( 16 ), the steps of said method comprising,

pressurizing the main chamber ( 4 ), the prepressurizing chamber ( 12 ), and the pressure relief chamber ( 16 ) with the same pressure for moving the impulse piston ( 8 ) in a direction towards the main chamber ( 4 ),

thereafter depressurizing the prepressurizing chamber ( 12 ) whereby the pressure in the main chamber ( 4 ) effects the impulse piston ( 8 ) so that the pressure in the pressure relief chamber ( 16 ) is further increased, and

thereafter depressurizing the pressure relief chamber ( 16 ) whereby a pressure impulse is transferred into the tool ( 10 ).

19. Method as claimed in claim 18 , further comprising the step of controlling the depressurization in said pressure relief chamber ( 16 ).

20. An 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 ) which is 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 ), said impulse generator further comprising,

means for pressurizing the prepressurizing chamber ( 12 ) for moving the impulse piston ( 8 ) in a direction towards the main chamber ( 4 ),

means for pressurizing the pressure relief chamber ( 16 ),

means for thereafter depressurizing the prepressurizing chamber ( 12 ) whereby the pressure in the main chamber ( 4 ) effects the impulse piston ( 8 ) so that the pressure in the pressure relief chamber ( 16 ) is further increased, and

means for thereafter depressurizing the pressure relief chamber ( 16 ) whereby a pressure impulse is transferred into the tool ( 10 ).

21. An 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 ) which is 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 area of the impulse piston towards the main chamber ( 4 ) is smaller than the sum of the areas of the impulse piston ( 8 ) towards the prepressurizing chamber ( 12 ) and the pressure relief chamber ( 16 ) but larger than the area of the impulse piston ( 8 ) towards the pressure relief chamber ( 16 ), said impulse generator further comprising,

means for pressurizing the main chamber ( 4 ), the prepressurizing chamber ( 12 ), and the pressure relief chamber ( 16 ) with the same pressure for moving the impulse piston ( 8 ) in a direction towards the main chamber ( 4 ),

means for thereafter depressurizing the prepressurizing chamber ( 12 ) whereby the pressure in the main chamber ( 4 ) effects the impulse piston ( 8 ) so that the pressure in the pressure relief chamber ( 16 ) is further increased, and

means for thereafter depressurizing the pressure relief chamber ( 16 ) whereby a pressure impulse is transferred into the tool ( 10 ).