Patent ID: 7331408

Claim:
A power tool comprising: an outer housing for gripping by a user; a motor disposed in the outer housing and including an output shaft; a transmission mechanism including: a hollow cylinder; a piston mounted for reciprocating motion within the cylinder; a ram mounted for reciprocating motion within the cylinder and located forward of the piston; and a space defined within the cylinder and between the piston and the ram and serving as an air spring for transmitting the reciprocating motion of the piston to the ram, a transmission housing located within the outer housing and substantially enclosing the transmission mechanism the transmission housing including an interior support structure for supporting the hollow cylinder within the transmission housing, and wherein the transmission housing, the hollow cylinder, and the piston substantially define a first chamber rearward of the support structure; and the transmission housing, the hollow cylinder, and the ram substantially define a second chamber forward of the support structure and separate from the first chamber; and a channel pneumatically connecting the first chamber and the second chamber in order to allow air flow between the first chamber and the second chamber to reduce pressure differences generated by the reciprocation of the piston within the first chamber.