GB816523A - Broaching machine - Google Patents

Abstract

816,523. Broaching. DETROIT BROACH & MACHINE CO. Jan. 14, 1957 [Jan. 16, 1956], No. 1319/57. Class 83 (3). A pull-boraching machine comprises safety means to render the machine inoperative when a handling slide 72 attempts to push the broach B through the work. Tool-holders; tools.-When the broach-carrying slide 21 is moved downwardly by hydraulic means 64, 66, a spring 44, Fig. 6, moves a sleeve 38 upwardly to cam four pins 60 into engagement with a groove 61 on the borach. The pins are released on a return-stroke when a collar 36 is arrested by the bottom of the work-table 12. The upper end of the broach is gripped frictionally by a spring-pressed bevelled plunger engaging a bevelled groove in the broach. The plunger is housed in a block 82 on the handling- slide 72, which is secured to hydraulicallyoperated rods 108 by a pair of pins adapted to shear at a given load. When the broach is in its correct upper position it engages a rod 126 depending from a fixed-bracket of the machine and actuates a switch LS7 to enable a cycle of operations to be initiated. At the beginning of an operation, a switch LS5 is also closed by the slide 21 in its upper position. When a startbutton is pressed, a solenoid-valve is actuated to cause the handling-slide 72 to move the bottom of the broach down through the work W. Actuation of a switch by a cam on the handling- slide causes a solenoid-valve to be operated to move the slide 21 downwardly. The handling- slide continues to move down by a small amount, and a switch is actuated by the pressure build-up when the slide reaches its lower limit of movement. When a cam 181 on the slide 21 actuates a switch LS2, the handling-slide is moved to its upper position. Speed-controlling.-Before the broach starts to cut, a check-valve prevents too-rapid movement of the slide 21, but when pressure rises, as the broach engages the work, a pressure-operated solenoid-valve by-passes the check valve. Movement of the slide 21 ceases when a further cam on the slide operates a switch LS3. The broach is then clear of the work, which may be removed. When a start-button is again pressed, the handling-slide moves down, the main slide moves up, and a cam thereon operates a switch LS4 to cause the handling-slide to move up again. The slides then continue to their upper positions. If the slide 21 slips down, the switch LS5 is released and causes it to be raised again. Stop-motions.-If the slide 21 moves down without gripping the broach, the handling-slide will first rise to its upper position and then, as it continues to move down with the slide 21, will attempt to push the broach through the work. The shear-pins then break and the handling- slide is pushed upwardly on the slide 21 so that a cam on the slide 72 closes a switch LS6 (not shown), which stops the machine and illuminates a warning-light. A manual switch must then be operated before the machine can be restarted. A manually-operated lever 230 serves to stop the machine at any time.