Patent ID: 7784561
Filing Date: 2010-08-31
Classification: E21B

Abstract:
1. A pneumatic hammer for rock drilling in which a piston strikes a button bit while being operated by compressed air in a cylindrical casing, the pneumatic hammer comprising: a cylindrical casing; a back head that is screw-engaged with an upper portion of the casing, the back head having a guide installed in the inner hollow space of the back head, the guide including a lower shaft portion, an intermediate anvil portion configured to be inserted into the inner peripheral edge portion of the back head, and a check valve receiving portion formed opposite the lower shaft portion; a check valve configured to be received in the check valve receiving portion of the guide and elastically supported by a coil spring; a piston adapted to ascend and descend in the casing, the piston including a chuck adapted to prevent escape of the piston from the casing and formed integrally with a bushing portion, the chuck having a button bit having a variable compressed air chamber formed between an outer periphery of the piston and an inner periphery of the casing.