Patent ID: 8087561
Filing Date: 2012-01-03
Classification: B25C

Abstract:
1. A powder-actuated fastener-driving device comprising: a housing having a front open end; a barrel mounted movably in said housing, and having a rear end portion that defines a powder load chamber adapted for accommodating powder load therein, and a barrel wall formed with a through hole extending from said rear end portion in an axial direction, and a vent hole extending radially from an inner annular surface thereof, disposed adjacent to said rear end portion and in spatial communication with said through hole, said vent hole cooperating with said through hole to constitute an exhaust passage; a driving piston mounted movably within said barrel and adapted for driving a fastener upon detonation of the powder load in said powder load chamber, said driving piston having a rear end portion that has a small-diameter section disposed adjacent to said rear end portion of said barrel and having a diameter slightly smaller than an inner diameter of said barrel such that an annular gap is defined between said small-diameter section and said inner annular surface of said barrel wall, and a large-diameter section having a diameter larger than that of said small-diameter section and substantially equal to the inner diameter of said barrel such that said large-diameter section abuts against said inner annular surface of said barrel wall, a firing chamber being defined between said rear end portion of said barrel and said small-diameter section of said rear end portion of said driving piston, and communicating with said vent hole through said annular gap upon detonation of the powder load in said powder load chamber; and a power adjusting unit for adjusting power acted on said driving piston by controlling venting of combustion gases from said firing chamber, said power adjusting unit including an adjusting member disposed movably in said housing and having a control end portion extending into said through hole in said barrel wall; wherein said adjusting member is operable to move said control end portion within said through hole in said barrel wall so as to control an effective open area of said exhaust passage such that combustion gases discharge from said firing chamber through said annular gap and the effective open area of said exhaust passage, thereby controlling venting of combustion gases from said firing chamber.