Patent GB-586678-A (GB)
Title: Improvements in or relating to a broaching machine
IPC: B23D37/04
Filed: 1943-09-16
Abstract: 586,678. Broaching. STEVENS, A. H. (Cincinnati Milling Machine Co.). Sept. 16, 1943, No. 15210. [Class 83 (iii)] A broaching-machine has a fluid-operated ram to effect simultaneously initial broaching operations on one pair of work pieces and final broaching operations on another pair and is provided with two arms to transfer a pair of work pieces from the initial to the final stations, an interlock valve being provided to prevent operation of the ram whilst the work is being transferred. The machine is described in connection with the formation of flats 68, 59, Fig. 6, at opposite ends of a blank 66 during the initial operation and of spaced axial slots 71 in a flange 70 of the blank during the final operation. The base 10 of the machine has a pillar 12 on which the ram 14 together with a cylinder 15 is reciprocated relatively to a fixed piston 16 and carries a work support 82, Fig. 2, to hold the blank in a groove 88 for the initial operation by opposed tools 104 adjustably mounted by gibs 109 on a head 98, Figs. 1 and 3, vertically adjustable on the ram by a dovetail 99 and clamp 100. Hydraulic fluid is supplied from a pump 31 to the bottom of the cylinder 15, to lower the ram, by a central passage 18, Fig. 13, in the pistonrod and fluid passes to the upper end of the cylinder by an annular channel 19 in the rod. Flow and return to both ends of the cylinder are controlled by a reversing valve 23 and pipes 21, 25 with the interposition of check valves 261, 262 loaded by springs of unequal strength to prevent falling of the ram when the pressure of the supply falls. The reversing valve 23 is moved to its two end positions by a pilot valve 44 and pipes 39, 40, the fluid proceeding from the pump to the pilot valve through pipe 30, a channel 59 in the spool 55 of a relief valve 50 and pipe 48 and the valve being operated by cams 146, 226 adjustably mounted on the ram. The blank feeding and transferring mechanism is operated by a pneumatic cylinder 115 in the base of the machine which is supplied with air by a compressor 125<1> as controlled by a reversing valve 120 operated by a crank 122 and dogs 128, 129 adjustably mounted on the ram. The piston-rod 113, Fig. 2, is connected by a block 112 to a vertically sliding rod 93 engaging a lever 89 whose upper end actuates two parallel blank feeding slides 79, Figs. 2 and 3, through an equalising bar 94 having ball ends 95 which act through spring plungers 97. In operation, with the parts as shown in Fig. 13, fluid from the pump 31 proceeds through a chamber 51 in valve 50, reversing valve 23 and check valve 262 to the top of the ram cylinder 15 to raise the ram. As the ram approaches its upper position, the dog 129 engages the crank 122 to move the air reversing valve 120 to the right and admit air above the piston 114, thereby moving the rod 93 downwards and causing a cam plate 184, Fig. 2, attached to the block 112 to oscillate a lever 160, Fig. 13, which engages a dog 178 on the interlock valve 149. Counterclockwise rotation of this valve to the position shown connects pipe 39, through a branch 147 and a passage 151 in the valve, to an exhaust pipe 153 so that when the cam 146 on the ram moves the pilot valve 44 to the right at the top of the stroke the pipe 48 will be connected to exhaust and pressure in the chamber 60 of the relief valve 50 will fall. The pump pressure on the other side of the spool 55 will then move valve 50 to the left to open a needle valve 56 and allow all the pump delivery to pass to exhaust by pipes 58, 36. This brings the ram to rest at the top of its stroke and prevents the reversing valve 23 from being actuated. As the air piston 114 continues its downward movement, the feeding slides 79 are moved inwards so that each one picks up the lowermost blank from a hand-fed hopper 75 to feed it to the work-holding groove 88. Each slide 79 is guided by slots 85, 86, Fig. 2, and pins 83, 84, the latter engaging a cam 87 at the end of its slot to tilt the forward end of the slide upwards and clamp the blank in the groove 88. Simultaneously with the movement of the slides 79, transfer arms 155, 156, Fig. 3, are oscillated to pick up the blanks which have previously been operated upon in the grooves 88 and transfer them to spring fingers 216 ready for the final broaching operation. Each arm 155, 156 is keyed to a shaft .158 and a crank 166 on each shaft has a, pin 165 lying in the path of an arm 161 attached to a cross-head 163 on the rod 93 so that as the latter descends the arms are rotated in opposite directions to carry the partly finished blanks held in spring fingers 202 thereon to a position above the fingers 216. On reaching this position, a spring finger 214 on the arm engages a fixed abutment 215, whereby the blank is pushed into the fingers 216 where it is held until engaged by a plunger 222 attached to the broaching ram and pushed, on the next downward stroke of the ram, between radially held broaches in a head 154 fixed on the machine frame. At theend of the downward stroke, the finished blank is pushed out of the head into a shoot. On completion of the downward stroke of the air piston 114, the arms 161 ride off the cranks to allow the arms 155 to be returned by springs to the intermediate positions shown and the cam plate 184 rocks the lever 160 to rotate the interlock valve 149 clockwise. This shuts the exhaust passage 153 and thus allows the needle valve 56 to close due to the pump pressure acting on the larger area of the spool 55 moving it to the right. Pressure thereupon builds up in the pilot valve 44 and proceeds by pipe 39 to the reversing valve 23 which is moved to the right to start the ram on its next downward stroke during which it performs the initial operation on the blanks in the grooves 88 and pushes the partly finished blanks through the heads 154 for performing the final operation. The shafts 158 for the transfer arms carry cams 190, Figs. 3 and 13, engaging valves 200 pressed into contact therewith by springs. Whilst the broaching ram is moving the arms are held in the intermediate position by spring detents and in this position the cams allow the valves to assume the position shown in which a pipe 198 connected to the pressure supply of the pilot valve 44 is cut off from an exhaust line 199 so that reciprocation of the ram can take place, but if the arms 155 should fail to be brought to this intermediate position by their return springs, one or both of the valves 200 will be depressed and the pressure supply will be connected to exhaust to prevent movement of the ram. The cranks 166 are attached to the shafts 158 through spring-pressed balls engaging grooves in the shafts so that the balls may yield if movement of the arms 155 is obstructed. During the initial part of the upward movement of the air piston 114, the arms 161 engage the cranks 166 to swing the arms 155 downwardly from their intermediate positions so that the fingers 202 may grip the partly formed blanks which have been released by the slides 79 and which remain in the grooves 88 of the work holders. The arms 161 then ride off the cranks and the shafts 158 and arms 155 are returned to the intermediate position by their springs and held there by spring detents until acted upon by the arms 161 on the next downward movement of the piston 114. A valve 227, Fig. 13, operated by a. handle 234, is provided for connecting the pressure line 48 to exhaust and thus stopping the ram at any time or at the end of a cycle of operations. A silencer 133 receives the exhaust from the air cylinder 115.