Patent GB-625972-A (GB)
Title: Improvements in or relating to metal cutting or similar machine tools
IPC: B23D37/06
Filed: 1946-02-26
Abstract: 625,972. Broaching. CINCINNATI MILLING MACHINE CO. Feb. 26, 1946, No. 5950. Convention date, Feb. 26, 1945. [Class 83 (iii)] In a duplex broaching or like machine, having a pair of work-holders alternately presentable to the cutting-tools, movement of the work-piece being operated on from its correct pre-determined position in its holder operates a safety-device to stop the machine. Work-holders.-Two work-holders 26, 27, Figs. 7 and 9, are each adjustable on a pivoted work-table 24 by a screw 49 and nuts 49a and have a pair of pivoted clamps 31 which are each clamped on the work W against the action of a spring 44 by a plunger 35 engaging a slope 37 on a piston 38 within a cylinder 39 in the holder. Fluid-pressure from a pump 52, Fig. 9, is directed to either end of the cylinder by a hand-operated valve 51 on each holder. The inside and one end of the work-piece are engaged by a pair of contacts 157, 158 in the left-hand holder and 159, 160 in the right-hand holder, each contact being mounted in a resilient insulating bush 162, Fig. 6, and having a hardened tip 161. Broaching.-The broaches are operated by hydraulic rams 14, 15 controlled by a main control and reversing valve 67 operated by a lever 63 having an intermediate stop position 63a, a start position 63b and a reverse position 63c. With the right-hand ram 15 performing a downward cutting stroke, as shown in Fig. 9, pressure fluid passes through the main valve 67, the direction valve 70, the line 72 and the righthand ram control valve 74 to the upper side of the ram piston 19. Return fluid from the lower side of the piston passes through the right and left-hand ram control valves 74, 81 to the lower side of the ram piston 18 and raises the lefthand ram 14. As the rams reach the end of their strokes, dogs 101 and 103 shift the valves 74 and 81 to right and left, respectively, and a dog 92 momentarily shifts an indexing valve 95 to the right so that the pressure line 72 is connected through lines 79, 105, 107, 97, 98 to an indexing ram 110, which rotates the work-table 24 to present the left-hand work-holder 26 in working position and withdraws the right-hand work-holder 27 for re-loading. A dog 111 on the ram 110 moves the direction valve 70 to the right and reverses the flow to the rams 14, 15. At the end of the ram strokes, a dog 117<SP>1</SP> on the ram 14 again momentarily shifts the indexing valve 95 to the right and dogs 119 and 120 restore the valves 74, 81 to their former positions. Fluid from a pressure line 68 then passes through lines 113, 115, 105, 122, 99 and 100 to restore the work-table to its former position at which point a dog 123 restores the direction valve 70 to its former position. Operation of safety device.-The motor 53 driving the pump 52 is started by pressing a push-button and, when fluid pressure has been built up, a switch PS1 is closed to maintain the connection initially established by the pushbutton. Assuming that the left-hand workholder 26 is empty while a work-piece is being broached in the right-hand holder 27, a workpiece is placed in the holder 26 and operates the contacts 159, 160 to energize a relay BW1 and an indicating light. The valve 51 is then operated to clamp the work and to close a pressure switch PS2. At the end of the downward stroke of the ram 15, the dog 101 operates a trip lever 102 to rock a cam 171 counterclockwise to operate switches LS1, LS2 and change the control of a circuit for solenoids SOL-1 and SOL-2 from the line containing a pressure switch PS3 for the right-hand workholder to that containing pressure-switch PS2, the switch LS2 being closed during the changeover to maintain the solenoids energized. If the work-piece which is in the operating position moves from its correct position in the workholder or its clamps are released, the solenoid circuit is broken at either the work-holder contacts or at the clamp pressure switches and the solenoids are de-energized. The plunger of solenoid SOL-1 moves down, allowing a spring-loaded plunger 132 to move up and rotate a bell-crank lever 139 to return the main control lever 63 to the stop position 63a and the plunger of solenoid SOL-2 moves down and places a block 147 against the lever 139 to prevent the lever 63 being returned to the start position until the cause of operation of the safety device has been remedied.