Patent GB-947548-A (GB)
Title: Improved rotary latch mechanism
IPC: F15B21/00
Filed: 1962-03-26
Abstract: 947,548. Turning. CROSS CO. March 26, 1962 [Nov. 2, 1961], No. 11443/62. Heading B3T. [Also in Divisions F2 and H2] A rotary latch mechanism (see Division F2) for stopping or holding machine spindle assemblies (e.g. the spindle assembly of a machine tool), comprises a latch plate 36 rotatable with a spindle assembly 30 and having a locking portion 64 so that the latch 54 is engageable with the looking portion 64 to hold the latch plate 36 in a rotatably locked position, the latch 54 being moved into and out of engagement with the latch plate 36 by means of a fluid pressure system constituted by a pump 98 feeding fluid through a solenoidoperated four-way valve 106 to a fluid motor 78 operatively connected to the latch member 54, and a pressure relief device 144 communicates with the fluid motor and is operative when the locking portion 64 engages the latch 54 to relieve pressure in the fluid motor sufficiently to permit the latch plate 36 partly to override the locked position against the action of the latch 54 and the fluid motor 78 so as to reduce the impact shook of engagement but not sufficiently to permit the locking portion 64 of the latch plate to override and disengage the latch 54 completely or to prevent the latch and the fluid motor from pulling the overriding latch plate back to the locked position. Fig. 1 shows the apparatus at the end of an operating cycle with the latch 54 engaged to locate the spindle 30 in a selected predetermined rotative position. When the main switch 150 is actuated to close the contacts 150A and to open the contacts 150B the operating cycle of the machine and latching apparatus is commenced. The closing of contacts 150A completes a circuit through a forward starter coil 154 to close a gang switch 176 and energize a reversible electric motor 20 for forward rotation of the spindle assembly 30 driven through gearing 26, 28. Closure of gang switch 176 completes a circuit through a contact 184 to operate solenoid 112 to shift the hydraulic valve 106 to the left. This actuates the fluid motor 78 to disengage the latch 54 from the latch plate 36 and permit forward rotation of the spindle assembly 30. As the latch 54 is disengaged from the latch plate 36 the abutment 274 on the latch 54 separates from a button 272 to open an orifice 270 and close an air-operated switch 168. As soon as the machine completes its cycle, the main switch 150 is moved to open the contacts 150A and simultaneously to close the contacts 150B so that the forward starter 154 is de-energized and a gang switch 176 is opened. A reverse starter coil 162 is then energized and closes a gang switch 186 to apply a reverse torque to the motor 20 which slows the forward rotation of the spindle 30, stops it and then reverses its direction of rotation. The hydraulic valve 106 is not shifted immediately upon actuation of the main switch 150 as the solenoid 112 remains energized through a plugging switch 232. This switch remains closed so long as the spindle 30 is rotating at relatively high speed. When the forward rotational speed of the spindle 30 drops below a predetermined value the plugging switch 232 opens and de-energizes the solenoid 112 permitting the spring 110 to shift the hydraulic valve 106 to the position shown in Fig. 1. This connects hydraulic pressure from the pump 98 to the cylinder 80 ahead of the piston 86 to actuate the hydraulic motor 78 and move the latch 54 into engagement with the latch plate 36. If the latch 54 engages the latch plate 36 while the spindle 30 is rotating in a forward direction it ratchets over the stop shoulder 70 without entering the recess 64. The air operated switch 168 remains closed as the abutment 274 is held away from the button 272 until such time as the latch 54 actually enters the recess 64 in the latch plate 36 fully. Full engagement causes air pressure to build up in the cylinder 260 ahead of the piston 258 sufficiently to overcome the resistance of spring 262 and open the air-operated switch 168 to interrupt the circuit through the reverse starting coil 162 and de-energize the motor 20, the latter then remains de-energized until such time as the main switch 150 is actuated to close the contact 150A.