US 2010/0059242 A1Published application

Percussion device

AssigneeSandvik Mining and Construction Oy

InventorsAntti Koskimäki, Ari Kotala

Life of this patent

Estimating the term…

Abstract

The invention relates to a percussion device having a body and a percussion piston moving therein, pressure fluid spaces in the rear and front ends of the percussion piston and pressure fluid channels for feeding pressure fluid into the percussion device. The percussion piston and the control valve comprise surfaces, which, when aligned, substantially close the pressure fluid flow from the pressure fluid space locating behind the percussion piston in front of the control valve, whereby the produced pressure displaces the control valve to another position.

Claims10

Dependent claims

A percussion device comprising a body and therein a percussion piston that moves longitudinally in a reciprocating manner by action of pressure fluid, in the body a first and a second pressure fluid space in the rear end and correspondingly in the front end of the percussion piston, and a control valve that is substantially sleeve-like, locating around the rear end of the percussion piston and movably mounted in the longitudinal direction of the percussion piston, as well as pressure fluid channels for feeding pressurized pressure fluid in and out of the percussion device, wherein

in the rear end of the percussion piston there is an annular surface facing the control valve, and correspondingly, on the inner surface of the control valve there is an annular surface facing the percussion piston so that as the annular surfaces are aligned they substantially throttle the pressure fluid flow between the percussion piston and the control valve,
as the reverse stroke of the percussion piston starts the control valve is in its rearmost position and closes access of the pressure fluid to a second pressure fluid space in the rear end of the percussion piston, whereby the pressure fluid is able to flow from the second pressure fluid space via a pressure fluid channel in front of the control valve away from the percussion device, and
the percussion piston having shifted rearwardly to a predetermined position the annular surface in its rear end will be in alignment with the annular surface on the inner surface of the control valve, and consequently as the reverse stroke of the percussion piston continues the pressure in the second pressure fluid space rises decelerating the reverse stroke of the percussion piston and at the same time as pressure is acting on the surfaces of the control valve on the side of the second pressure fluid space of the control valve it makes the control valve move towards the front end of the percussion device, whereby the annular surfaces of the percussion piston and of the control valve will move apart so that the pressure fluid in the front end of the control valve is able to flow into the second pressure fluid space in the rear end of the percussion piston and the control valve closes the pressure fluid flow through the channel out of the percussion device.

Dependencies are inferred from the claim text.

patentgrep

Loading patent…

Abstract

in the rear end of the percussion piston there is an annular surface facing the control valve, and correspondingly, on the inner surface of the control valve there is an annular surface facing the percussion piston so that as the annular surfaces are aligned they substantially throttle the pressure fluid flow between the percussion piston and the control valve,
as the reverse stroke of the percussion piston starts the control valve is in its rearmost position and closes access of the pressure fluid to a second pressure fluid space in the rear end of the percussion piston, whereby the pressure fluid is able to flow from the second pressure fluid space via a pressure fluid channel in front of the control valve away from the percussion device, and
the percussion piston having shifted rearwardly to a predetermined position the annular surface in its rear end will be in alignment with the annular surface on the inner surface of the control valve, and consequently as the reverse stroke of the percussion piston continues the pressure in the second pressure fluid space rises decelerating the reverse stroke of the percussion piston and at the same time as pressure is acting on the surfaces of the control valve on the side of the second pressure fluid space of the control valve it makes the control valve move towards the front end of the percussion device, whereby the annular surfaces of the percussion piston and of the control valve will move apart so that the pressure fluid in the front end of the control valve is able to flow into the second pressure fluid space in the rear end of the percussion piston and the control valve closes the pressure fluid flow through the channel out of the percussion device.