Patent ID: 7464635
Filing Date: 2008-12-16
Classification: B25D

Abstract:
1. A percussion device comprising: first and second percussion pistons alternately making a percussion motion and a control valve for controlling the percussion pistons, where both percussion pistons are provided with a first pressure space and both percussion pistons comprise a first pressure surface facing a tool and communicating with said first pressure space, both percussion pistons comprise at the back end thereof a second pressure space and both percussion pistons comprise a second pressure surface directed backwards and with a surface area that is larger than that of the first pressure surface communicating with the second pressure space, whereby the pressure of the pressure fluid is constantly high in the first pressure space during the operation of the percussion device, and whereby the second pressure space of both percussion pistons is connected to a high pressure channel and correspondingly a discharge channel in order to alternately obtain a percussion motion and correspondingly a return motion, and control means for controlling the control valve with the percussion motion of both percussion pistons, whereby the control valve comprises a slide affected by a force in the direction of motion thereof so that the slide is generally in a first position thereof, wherein in the first position of the slide the control valve connects the high pressure channel to a channel leading to the second pressure space of the first percussion piston and connects the discharge channel to a channel leading to the second pressure space of the second percussion piston, wherein the control means are connected to act on the slide of the control valve at the end of the percussion motion of the first percussion piston so that the slide moves from the first position to a second position, whereby the control valve connects the second pressure space of the first percussion piston to the discharge channel of the pressure fluid and connects the high pressure channel to a channel leading to the second pressure space of the second percussion piston, and wherein the control means are connected at the end of the percussion motion of the second percussion piston to act on the slide of the control valve so that the slide again moves from the second position to the first position; wherein the control means comprise first and second grooves on first and second percussion pistons, respectively, each of said percussion pistons being part of the control means, the slide of the control valve comprises a pressure surface, a pressure of the pressure fluid acting on the pressure surface causes an opposite force in relation to the force affecting the slide, wherein a first control channel leads from the first percussion piston to the control valve that communicates through the first groove at the end of the percussion motion of the first percussion piston with the high pressure of the pressure fluid so that said pressure is able to act upon the pressure surface of the slide of the control valve in order to move the slide from the first position to the second position, and wherein a second control channel leads from the second percussion piston to the control valve that communicates at the end of the percussion motion of the second percussion piston through the second groove with the discharge channel of the pressure fluid so that the high-pressure pressure fluid affecting the slide of the control valve can be discharged onto the discharge channel and the slide moves again to the first position thereof.