Patent GB-800290-A (GB)
Title: Improvements in power operated gear shifting mechanisms for machine tools
Inventor: SASSEN BERNARD
IPC: B23Q5/14
Filed: 1957-02-08
Abstract: 800,290. Controlling change-speed gear. MONARCH MACHINE TOOL CO. Feb. 8, 1957, No: 4421/57. Class 80 (2). In a change speed gear having a brake on the output shaft, and power operated shifting mechanism, a selective device actuates a signal device for causing a signal when the gears are disengaged, the brake being engaged responsive to the signal and being prevented from engagement on the absence of the signal. A change speed gear 30, 34, 32, 36 between a driving shaft 24 and a driven shaft 38 of a machine tool is driven by a motor 12 through an hydraulically operated clutch 20, 22 actuated by leftward movement of a piston 28. Rightward movement of the piston 28 engages a friction brake 44, 46 on the shaft 24 which also carries a jogging clutch 40, 42 driven by a jogging mechanism 108 and engaged by a cylinder 112. The shaft 24 also drives a speed indicating unit 75 comprising a piston 80 driven by an eccentric 74 and supplying speed responsive pressure to a valve 95. The valve 95 is loaded by a spring 124 such that when the speed of the shaft 24 falls sufficiently and the speed responsive pressure from the unit 75 falls, the valve moves to the left to connect a line 110 from the jogger mechanism 108 to a line 114 to engage the jogger clutch 40, 42, and also passes pressure fluid from a pump 50 through pressure line 54 to a line 106 to release a positive detent 228 preventing movement of the shift mechanism linkwork under control of a shift control valve 192. Shift control valve has three positions " run," 11 shift " and " free spindle " and is prevented from being turned to " free spindle " position by a stop 225 before the gear train.is running below a certain speed. A selector valve 58 controls the admission of fluid to a cylinder 72 having a piston 70 on a rod 68 connected to a gear selector fork 66, the valve 58 being operated by a shaft 198 rotated by the output of a differential 200 having inputs 202, 204 carrying notched discs 206, 208. Except when the shift control valve 192 is in the " shift " position, linkwork 218, 210, 212 locks the discs 206, 208 by virtue of the detent 228. A detent line 134 is connected to the pump line 54 through a restriction 132 and to the jogging mechanism 108, as well as a spring-loaded detent valve 136 which opens the line 134 to the sump 52 when the gears are not in mesh. The detent line 134 is also connected to a line 142 which supplies pressure to a clutch brake valve 144 through relief valves 143, 145 which provide slow pressure build-up in the clutch or brake cylinders 48, 26 on appropriate movement of the lever 146. The shaft 38 carries a notched brake disc 178 engageable by a dog 180 under the action of a piston 184 controlled from a spool 170 acted on by a spring 172, and pressure in a line 160 connected to a valve 156 under the control of a spring 166, fluid pressure from detent line 134 and a sump drain through a port 194 in the shift control valve 192. Operation.-Under normal running conditions with the gears 32, 36 engaged, detent valve 136 is closed to produce high pressure in line 134 which through line 142 produces high pressure in the brake-clutch valve 144 and correspondingly in the clutch cylinder 26. With the shaft 24 rotating rapidly the speed pump 80, 82 causes the valve 95 to remain to the right, and thus prevent engagement of the jog-clutch 40, 42 by draining cylinder 112. The high pressure in line 134 indicates to the jogging mechanism 108 that the jog-motor should not run, and also depresses the spool 159 to cause draining of line 160 and consequent disengagement of the dog 180. To shift the gears the control valve 192 is moved to the " shift " position and the brakeclutch valve 144 to either the brake or neutral position. The shaft 24 slows and the output of the speed-pump 80, 82 passes through the resistance 92 to allow valve 95 to move to the right to allow communication between lines 54 and 106 and 110 and 114 to release the detent 228 to allow movement of the discs 206, 208 of the selector, and to engage the jogging clutch 40, 42. When the gear shifting starts the detent 138 is unseated and pressure in line 134 drops causing, through line 142, substantial release of the brake 44, 46. This pressure drop also indicates to the jog mechanism 108 that it should operate, and further through pressure drop in line 158 and communication between 164 and 160 to depress plunger 170 and cause engagement of the dog 180 with brake disc 178 to lock the shaft 38. On full engagement of the gears the detent 136 closes to restore high pressure in line 134 and results in disengagement of the jog-clutch 40, 42, and of detent 180. Movement of the shift control valve 192 to the " run " position moves the linkwork 218, 210, 212 into engagement with the discs 206, 208 and allows the detent 228 to lock the linkwork in this position. Engagement of the clutch 20, 22 causes rotation of shaft 24 and consequent movement, by virtue of the speed-pump 80, 82, of the valve 95 to the right. Should the operator require " free spindle " the shift control valve is moved to this position as soon as the shaft is running below a predetermined speed, and line 164 is connected through the groove 194 to a line 190 to cause depression of a ball 188 and spool 159 to cause disengagement of the dog 180.