Patent ID: 7896100

Claim:
Valve device (V, 4 ′) for controlling the movement in a machine housing ( 2 ) of a reciprocating percussion piston ( 3 ) of a percussion device ( 1 ) for a rock drilling machine with a first chamber ( 5 ) that can be pressurized for forward driving of the percussion piston ( 3 ) and a second chamber ( 8 ) that can be pressurized for back-driving of the percussion piston ( 3 ), wherein the valve device includes a to and fro movable valve element ( 20 ), the movement of which being controlled as a response to the position of a valve portion (V) of the percussion piston in a valve housing portion by periodically pressurizing a signal chamber ( 21 ) actuating the movement of the valve element over signal conduit means ( 22 , 23 , 24 ), wherein: said signal conduit means includes at least two signal conduit portions ( 23 , 24 ), which are arranged for essentially simultaneous pressurizing through co-operation between a corresponding number of valve control edges ( 25 , 26 ) on the valve portion of the percussion piston and a number of edges ( 34 , 35 ) of control chambers in the machine housing, said number of valve control edges and said number of edges of control chambers corresponding to the number of signal conduit portions, said valve control edges of said percussion piston, said at least two signal conduit portions, and said edges of control chambers being arranged such that relative movement between said percussion piston and said machine housing results in said essentially simultaneous pressurizing of said at least two signal conduit portions.