GB995499A - Improvements in or relating to fluid powered gun for setting fasteners - Google Patents

Abstract

995,499. Fluid-pressure apparatus. TOWNSEND. CO. March 30, 1962, No. l2370/62. Heading F1P. [Also in Division B3] A fluid powered device for setting a tubular fastener comprises a body, a closed hydraulic system in the body including a work cylinder, a work piston in the cylinder, having a piston rod extending beyond the cylinder, a double acting hydraulic fluid pump including a cylinder connected at one end to said work-cylinder at one side of the work-piston and at the other end to the work-cylinder at the other side of the workpiston and means for moving the pump piston in each direction, said hydraulic system further including a fluid reservoir in the body, a first passage connecting the reservoir to one end of the pump cylinder and containing a check-valve which permits fluid to flow to that end of the cylinder when the piston moves away therefrom, and a second passage connecting the reservoir to the other end of the pump cylinder and containing a similar check-valve. The body 20 of the device is enlarged at its lower end to form the cylinder of a double-acting pneumatic piston and cylinder assembly 22 which comprises the means to drive the pump piston through a piston rod 89. The hydraulic fluid reservoir comprises the annular space between the body 20 and the sleeve 92 which forms the cylinder of the hydraulic pump, and which is open at its upper end, and at its lower end is sealed to the end wall of the pneumatic cylinder. The piston rod 89 slides through a packing 102. Mounted on the piston rod 89 is a piston 90 which is free to move axially on the rod between a retaining ring 106 and a shoulder 108. There is clearance between the bore of the piston and the piston rod to provide a fluid passage 110. At the upper end of the body is a cylinder 122 which contains a piston 138 which has a tubular extension 144, externally threaded at its righthand end for connection to the draw bolt of a fastener setting head. The left-hand end of the cylinder 122 is closed by a cap 134, a sleeve portion 136 of which forms a stop for the piston 138. When the pneumatic cylinder 22 is actuated by a control valve 82 the piston rod 89 moves down and fluid passes through the passage 110 until a valve face 112 on the shoulder 108 engages a valve seat 114 on the piston, and draws the piston down. Fluid displaced from the cylinder 92 passes through ports 118 and a passage 120 to the right-hand end of the cylinder 122 and moves the piston 138 to the left to set the fastener. The broken-off stem of the fastener mandrel passes through a bore 172 in the piston and is deflected downwards by a plate 186. The return stroke of the piston 138 is effected by a return piston assembly 188 which comprises an open-ended cylinder sleeve 190 screwed into the underside of the cylinder 122. The upper end of the cylinder sleeve 190 is connected by a port 194 with the left-hand end of the cylinder 122. Movable in the cylinder sleeve 190 is a return piston 196 which includes a sleeve 198 and a shoulder 200 against which bears a spring 202. Downward movement of the piston 196 is limited by a ring 204. During the latter part of the upward stroke of the pneumatic piston, the piston rod 89 engages the return piston 196 and moves it upwards thus forcing hydraulic fluid into the right-hand end of the cylinder 122. During the downward stroke of the piston 90 the return piston 196 is moved down by the spring 202 until it contacts the stop ring 204. The rate of movement of the return piston 196 is governed by the rate of flow of fluid from the reservoir 132 upward through the passage 211, at the same time fluid is pumped from the lefthand side of the piston 138 to the upper end of the cylinder sleeve 190 so that the space above the return piston is always full. The return piston 196 displaces a greater volume of fluid than is necessary to move the piston 138 to the right-hand end of its stroke and excess fluid passes by way of a check-valve 216 to the reservoir 132. The return piston arrangement described produces sufficient force to disengage the swaging anvil from the swaged collar of the fastener.