GB690010A - Improvements in devices for imparting controlled displacements to a machine-tool carriage - Google Patents

Abstract

690,010. Lathes. COMPAGNIE GENERALE DE CONSTRUCTION DE LOCOMOTIVES (BATIGNOLIES-CHATILLON). March 22, 1951, No. 6911/51. Class 83 (iii). Means for imparting con. trolled displacements to the carriage 1 of a lathe &c. comprises a feed-screw 2, Fig. 3, journalled in the machine frame 4 parallel to the direction of movement of the carriage, a piston 6 rigid with the carriage and movable in a fixed cylinder 9, a pump 10 arranged to supply fluid to both ends of the cylinder, a valve chamber 5 mounted on the carriage and provided with a valve 7 reciprocable in a direction parallel to the feed screw for controlling the fluid supply to one end of the cylinder, means which react against the threads of the lead screw and are movable with the carriage with provision for slight axial displacement relatively thereto, and an integral feeler on the valve urged into axial contact with the reacting means whereby an increasing thrust against the reacting means causes movement of the valve in a direction to increase the relative pressure in opposite ends of the cylinder and corresponding movement of the carriage. Alternatively, the valve chamber 5, Fig. 7, is mounted on the fixed frame, the feed screw instead of the reacting means is mounted for slight axial displacement, and the valve feeler is urged into axial contact with the feed screw. In the construction shown in Figs. 3 and 5, the piston 6 is rigidly connected with a valve block 5 which is mounted on the underside of the carriage and comprises two spring-pressed valves 7, 18. The operation of the piston 6 is by pressure fluid supplied by the pump 10 to the right-hand end of the piston and passing therefrom to the valve 18 in the block 5 through a channel 16 in the piston-rod. The fluid then passes through a channel 17 in the piston-rod to the opposite end of the piston, the pressure there being determined by the valve 7 which controls the drain outlet 22 and is normally urged by a spring 8 to seal this outlet. This valve is controlled by a plunger 23 which is slidable in a part 72 on the underside of the carriage and urged by a spring 24 into contact with the valve feeler. The plunger is formed as an irreversible worm 23a engaging a gear 25 splined on a shaft 76 which is urged by a spring 79 so that it is coupled by a clutch 78, 80 with the shaft of a gear 27 meshing with the feed screw 2. The feed screw is driven from the headstock spindle 30 through mechanism which includes solenoid-controlled reduction and reversing gearing 32, pick-off gears 38, 39, clutch 4 and gears 40, 41. The movable member 42a of the clutch 4 is engageable with either a driving member 46 or brake member 47; normally a spring 52 urges the member 42a into braking position, but when a solenoid 51 is energized only weaker spring 48 is operative to move the member into driving position. In operation, the valve 7 is first set so that the pump 10 passes fluid to both sides of the piston 6 and, since the left-hand end of the latter is the larger, the carriage moves to the right; the gear 27 then rolls over the feed screw 2, causing the plunger 23 to actuate the valve 7 until the pressure on the two sides of the piston is the same. On rotation of the feed screw 2 by energizing the solenoid 51, the gear 27 is rotated and the plunger 23 controls the valve 7 and thereby pressure in the left-hand end of the cylinder 9 to move the carriage correspondingly. Rapid movement of the carriage to the right is effected by energizing a solenoid 83 so as to disengage the clutch 80, 81, whereby the gear 27 runs freely and the valve 7 is then urged by its spring 8 to seal the drain outlet 22; rapid movement in the opposite direction is effected by additionally energizing a solenoid 66 to withdraw the valve 7 and so open the drain outlet. The carriage may be displaced under manual control by using a hand wheel 73 to rotate the worm 23a. In the modification shown in Fig. 7, the valve block 5 is fixed in the machine frame, the valve 7 is controlled directly by the feed screw 2 which is capable of slight axial displacement and is normally urged to the left by a spring 87, and the gear 27 is again associated through the solenoid-controlled clutch 78, 80 with the worm gearing 23a, 25, which is of irreversible character. When rotated, the feed screw as a result of its engagement with tho fixed gear 27 moves axially and operates the valve. Rapid movement of the carriage in one direction is effected by energizing the solenoid 83 to disengage the clutch 78, 80, and in the other direction by additionally energizing the solenoid 66 to withdraw the feed screw from the valve. Alternative constructions, Figs. 1 and 2 (not shown), are described in which the feed screw is driven by a separate motor, the various clutches shown in Figs. 3 and 7 are omitted and the gear 27 and its supporting structure shown in Fig. 7 are replaced by a fixed finger depending from the carriage and engaging the feed screw.