Patent GB-629199-A (GB)
Title: Improvements in or relating to preselecting gear mechanisms for lathe headstocks andlike purposes
IPC: B23Q5/18
Filed: 1947-09-15
Abstract: 629,199. Controlling change-speed gearing. WARD & CO., Ltd., H. W., and HOOSON, G. C. Sept. 15, 1947, No. 25171. [Class 80 (ii)] A lathe headstock or like change-speed gear has slidable gear elements each actuated by an individual hydraulic unit controlled by its own manually-operated preselection valve, separate manual means being provided which both operates a single main executive valve and releases a main clutch having a driven shaft brake. A centrifugally-operated valve may prevent forward-reverse executive action above a predetermined speed of the corresponding gear elements. Power inching during gear changing may be effected hydraulically or mechanically. As shown applied to a lathe or other machine tool headstock in which slidable pinion groups a, b, c combine to give twelve speeds and a further forward-neutral-reverse group d conveys the resultant drive to the chuck or work spindle, sliding of the groups is effected by hydraulic pistons f, m, p, i operated by pressure fluid supplied by pumps P1 ... P5 and controlled by preselective plunger valves f1, m1 p1, i1 and an executive plunger valve 8. The valves f1, m1, p1, i1 are operated, preferably against springs (not shown) through rotary cams 10 ... 12 and 15 by control knobs 14, 18 respectively, and may be pre-set whilst the machine is running, the speed selected being rendered effective only when the change-speed mechanism has been disconnected from the power source and brought to rest as follows. Whilst the machine is running, the valve 8 connects the pumps P1 ... P5 through its hollow interior to exhaust as shown, and prevents operative pressure building up in the control system. The valve 8 has a lost-motion connection to an extension 6 on a cam 2 rotated by a hand lever 3 having a transverse pivotal connection 4 to the cam shaft and moving in a slotted gate 5. Initial movement of the lever 3 to the right acts through a cam follower z and a rod x to disengage the main pulley-driven clutch s, t. Continued movement to the right, allowed by transverse movement of the lever into a second slot, brings the driven clutch member first into connection with a brake. member w and then into a central neutral position. The lost-motion in the connection 6, 8 has now been taken up, and a final movement of the lever 3 closes the valve 8 to render the pressure fluid effective on the control system according to the setting of the valves f1, m1, p1, i1 as follows. Pumps P1, P2 constantly supply pressure fluid directly to both sides of the piston f, which has a gearing operative position at the middle, as well as at either end, of its stroke. Preselective movement of the valve f1 to the position shown connects ports 20, 21 to exhaust ports E1, E2 and, when the valve 8 is closed, centralizes the piston f to bring in the corresponding speed. Subsequent preselective movement of the valve f1 in either direction connects one or other of the pumps P1, P2 to an exhaust port E3 and prevents the pressure fluid from that pump becoming operative when the .valve 8 is closed, so that the piston f moves correspondingly to one or other end position. Operation of the piston i is effected similarly in conjunction with the pumps P4, P5 and the valve i1. Each piston m, p has only two gearing operative positions, one at either end of its stroke, opposite sides of each piston being connected alternately to the pump P3 and to an exhaust port E4 respectively by movement of the corresponding valves m1, p1. To prevent inadvertent actuation of the valves f1, m1, p1, i1 when the valve 8 is closed an interlock (not shown) may be provided between the lever 3 and the spindles 13, 16 of the knobs 14, 18. The gate 5 may co-act with the extension 6 in which case the extension may be formed in one with the lever 3. To prevent operation of the piston i when the pinion group d is rotating too rapidly, centrifugal weights 25 thereon act on a valve 27 to connect the pumps P4, P5 to exhaust above a pre-determined speed of the group. Power inching of a pinion group, as the group a, during gear changing, may be effected by tight engagement of the main clutch, or by rotating the gears through turbine means associated therewith, as from a pump P6. According to the Provisional Specification, such inching may be effected by a light spring pad disposed in the main clutch, by jets of oil impinging at high pressure on one or more gears in the train, or by the employment of fluid flywheel or like devices.