| 摘要 |
<p>A broaching machine (l0) having an upper crosshead (ll), a worktable (l4) and a lower crosshead (l2) is provided with drive interruption means to reduce the risk of breaking a broach during broaching of an undersized or misplaced work piece. The upper crosshead (ll) descends on a pair of rams, one of which has its piston rod (20) non-positively coupled to the crosshead (ll). A bobbin (25) rigid with the rod (20) may undergo movement relative to the crosshead (ll) if the latter is obstructed and this movement is detected by a proximity sensor (27) providing a signal to interrupt the crosshead lowering drive. The arrangement can optionally be used for the setting of upper and lower limit switches (3l) and (34) for the machine which are positioned by electric cylinders (32) having a lead screw and gear roller arrangement and incorporating pulse generating signal means. The upper limit switch is set for a particular broach by lowering the upper crosshead (ll) until the broach contacts the pull chuck (9). The electric cylinder (32) seeks the position of the crosshead (ll) and generates a control signal to position the upper limit switch accordingly. The same control signal can automatically be used to set the position of the lower limit switch (34) mounted on a second electric cylinder (35).</p> |
