GB616289A - Improvements in or relating to a transmission and control mechanism for machine tools - Google Patents

Abstract

616,289. Variable-speed gearing. CINCINNATI MILLING MACHINE CO. Feb. 27, 1946, No. 6094. Convention date, March 5, 1945. [Class 80 (ii)] In a variable-speed drive from the motor 14 to, for example, the cutter spindle 10 of a milling machine in which sliding gears are arranged on a series of parallel countershafts to provide a large number of speed ratios, a separate auxiliary drive from the motor is provided to drive the gearing at a slow speed when a main driving clutch is disengaged to facilitate the correct meshing of the gears, As shown, the motor drives a pulley 17 which is connected to a shaft 24 of the gearing through a friction clutch (not shown) arranged within the pulley. Sliding gears 85 and 88 on a shaft 47 coupled to shaft 24, gears 90 and 94 on a shaft 89, and gears 102 and 106 on a shaft 101 are adapted to be selectively actuated by hydraulic shifting devices 118 under control of a selector valve 111. A control shaft 133 of this valve is adapted to be actuated by power from an auxiliary drive from the pulley 17 to a shaft 124 and bevels 126, 127, a clutch member 128 being engaged with either of these bevels, to operate the selector valve shaft for an increase or decrease in speed ratio, by actuation of a speed control lever 137 in one direction or the other. The actuation of the main drive clutch contained within pulley 17 is effected by hydraulic pressure on a piston member 56 controlled by a valve 51 operated by a clutch control lever 55. This piston member also actuates a brake (not shown) for arresting the shaft 47 and the gearing when the clutch is disengaged. An interlocking device 140 between sliding rods 135, 142 connected to the control levers 137 and 55 respectively ensures that a gear change cannot be effected whilst the clutch is in or that the clutch cannot be put in whilst. a change is being effected. The slow speed drive when the clutch is disengaged is obtained from the auxiliary drive shaft 124 through a sliding gear 149 driving a gear 150 which drives the shaft 47 through a one-way clutch device 151, the latter facilitating engagement of the gears 149, 150 and preventing damage if the transmission gearing has not completely come to rest. The engagement of gears 149, 150 is effected automatically whenever the speed control lever 137 is moved from a neutral position 138a to positions 138b or 138c, for either an increase or decrease of speed, by means of a piston valve 158 connected to the rod 135 of lever 137 which supplies pressure fluid to operate a shuttle valve 162 which controls the supply of pressure fluid to a shifter cylinder 167 to actuate the sliding gear 149. This shifting device also controls through a valve portion 180 the fluid pressure operating the brake on the transmission shaft 47 so that the transmission is freed when the slow drive is engaged. The shuttle valve 162 provides a delay action in the disengagement of gear 149 of the slow speed drive after the speed control lever 137 has been returned to neutral on the desired speed selection being obtained. This delay action is effected by controlling the escape of pressure fluid from the left-hand end of the shuttle valve through a resistance path 186 and ensures the completion of the desired change. The valve portion 180 of shifter 167 moreover delays the supply of pressure fluid through pipe 115d to the clutch operating servo device 56 and valve 51 to prevent engagement of the clutch until the change is completed. A cam 202 on the control shaft 133 of the selector valve 111 is adapted to operate a limit switch LS1 in the motor circuit to bring in relays to ensure that the motor does not operate above a certain output in the low-speed ranges whilst allowing the full output of the motor in the high-speed ranges. Specification 369,899, [Group XXII], is referred to.