Patent ID: 7735584
Filing Date: 2010-06-15
Classification: E21B

Abstract:
1. A percussion hammer for enlarging drilled holes comprising an external outer wear sleeve ( 5 ), an inner cylinder ( 7 ) mounted co-axially within the outer wear sleeve ( 5 ), a tubular torque shaft ( 3 ) disposed axially and centrally of the hammer assembly, and extending longitudinally through the assembly, a sliding piston ( 6 ) mounted for reciprocating movement within the inner cylinder ( 7 ) and outer wear sleeve ( 5 ) and about the tubular torque shaft ( 3 ) to strike a hammer bit ( 1 ) for reciprocal movement in a chuck ( 4 ) adjacent a forward end of the hammer assembly, the hammer bit ( 1 ) having a central bore ( 46 ) through which the torque shaft ( 3 ) extends, such that the torque shaft ( 3 ) protrudes forwardly of the hammer bit ( 1 ), characterised in that a) an adaptor ( b) the rearward end of the torque shaft ( c) the rear end of the wear sleeve ( d) the forward end of the wear sleeve (