Patent GB-677085-A (GB)
Title: Hydraulic follow-up control system
IPC: B23Q35/18
Filed: 1949-10-24
Abstract: 677,085. Copy-turning &c. FISCHER AKT.-GES., G. Oct. 24, 1949 [May 20, 1949], No. 27287/49. Class 83 (iii). A hydraulically-operated copying lathe or other machine-tool has two pumps which are driven by a constantly-running motor 20 and are geared to a rotatable machine part, such as an irreversible drive formed by a lead screw 33 operating the tool-holder 6, the output of at least one of the pumps being throttled by a control member 12 so that the difference in torque between the two pumps causes rotation of the machine part. A pair of bevel-wheels 26, 27 journalled on a bearing 25 in a housing 18 are driven by the motor 20 and attached to each bevel wheel is a distance-plate 29 and coverplate 23. The pair of oppositely-running pumps are formed by a pair of gears 36 on the lead screw spindle 33, each engaged by a set of three gears 31 journalled in each bevel wheel and cover-plate. The pump outputs pass through pipes 46 and 47 to a valve 11 having a spring- loaded piston 12 engaged by an arm 15 of a pivoted feeler 17. The valve 11, pump housing 18 and the tool-holder are carried by a longitudinal slide 4, the valve 11 being adjustable transversely on a slide 9 and the transverse position of the tool-holder 6 being initially adjustable on its slide 5 by a hand-crank on the squared end of the spindle 33. When the feeler is in contact with a straight part of the pattern 3 carried by the lathe bed 1, the valve throttles the pump outputs equally into the chamber 53, whence the fluid returns to an injector 58 in the sump 19. The two pumps rotate round the stationary spindle 33 until the feeler contacts a rise or fall of the pattern, when the piston 12 throttles one output more than the other and the consequent difference in torque between the two pumps causes the spindle 33 to rotate and move the tool-holder in the appropriate direction. For copying from a pattern with rightangled steps, the feeler, tool-holder and pump housing may be adjustable on the slide 4 so that they lie at an angle to the work axis. In a modification, Fig. 5, a central rotor shaft 84 is driven by a motor 77 and, in each pump, a pair of outer rotors 97 are journalled in the pump cover 98 and in a bevel-wheel 95 attached to the pump housing 92, which is rotatable in bearings 93. Fluid is drawn in through holes 99 in the pump housing and delivered by a pipe 100 to a sleeve valve 109 surrounding ports in the lead screw 102. The position of the valve sleeve is constantly regulated by hand, according to the movement required of the machine part, by gearing 115. If the sleeve 109 is rotated so that the pump outputs are unequally throttled, the pump housings rotate in opposite directions and this rotation is transmitted to the spindle by bevel-wheels 85, 95 and 101 until it is again in the central position with regard to the valve sleeve. In either embodiment, the part of the pumps which is continuously rotated may be interchanged and the output of one pump only may be controlled by the feeler valve, while the other pump operates against a spring-loaded valve. The lead screw may be replaced by a rack and pinion.