Patent ID: 8434465
Filing Date: 2013-05-07
Classification: F41B

Abstract:
1. A blowback assembly for a gun having a muzzle at a first end and a hammer at a second, opposite end, the blowback assembly comprising: a valve body having an aperture extending therethrough, substantially axially the aperture having a stepped profile defining (i) a valve stem chamber, (ii) a gas expansion chamber on the muzzle-side of the valve stem chamber having a cross-sectional area smaller than a cross-sectional area of the valve stem chamber, (iii) a gas expulsion chamber arranged on the muzzle-side of the gas expansion chamber having a cross-sectional area smaller than the cross-sectional area of the gas expansion chamber, and (iv) a blowback opening arranged on a hammer-side of the valve stem chamber having a cross-sectional area smaller than the cross-sectional area of the valve stem chamber: a gas supply port formed through the valve body to supply a compressed gas to the valve stem chamber; and a valve stem disposed in and movable with respect to the valve body, the valve stem having a stepped outer profile defining an annular valve seat intermediate a forward section and a rearward section, the annular valve seat having a cross-sectional area larger than a cross-sectional area of the forward section and larger than a cross-sectional area of the rearward section, the forward section extending into the gas expansion chamber of the valve body and the rearward section extending into the blowback opening, a clearance being formed between the blowback opening and the rearward section of the valve stem, the valve stem further comprising an internal passageway including an axial bore that terminates at an opening in a front end of the valve stem, the opening being coaxial with the valve stem, and at least one orifice, connecting an opening in a sidewall of the rearward section of the valve stem to the axial bore, wherein the valve stem is movable in an axial direction relative to the valve body from a normal position in which the annular valve seat is biased against a back wall of the valve stem chamber to a firing position in which the annular valve seat is spaced from the back wall of the valve stem chamber.