Patent GB-856419-A (GB)
Title: Improvements in or relating to milling machines
Inventor: OBTRESAL ROBERT
IPC: B23C9/00
Filed: 1957-04-09
Abstract: 856,419. Milling-lathes. GESELLSCHAFT FUR FERTIGUNGSTECHNIK UND MASCHINENBAU G.m.b.H. April 9, 1957, No. 11462/57. Class 83 (3). A milling-lathe comprises a tool-carriage 1 fed by an hydraulic cylinder 3, a stop 8 to reduce the rate-of-advance after a predetermined travel, and a stop 9 engaged by the stop 8 to end the feed. The cylinder, with the carriage attached, is fed towards the work by the admission of oil under pressure to a port 6 on the right-hand side of the piston 4, which is held against movement. A switch 12 within the stop-sleeve 8 is operated by the end of the piston-rod 4a before this encounters the end of the stop-sleeve, the switch starting an electric motor which rotates a worm 11 meshing with a worm-wheel 10 engaging screw-threads on the stop-sleeve. Thus, contact between the pistonrod 4a and stop 8 reduces the speed-of-movement of the cylinder and tool-carriage to that of the stop 8 which, at the end of its traverse, engages the adjustable stop-screw 9, causing the worm to move axially and operate a switch stopping its motor and starting that for rotating the work. As applied to milling the crankpins 7a, Fig. 4, of a crank-shaft 7, as the shaft is rotated through one revolution about its journals, the carriage is advanced, beyond the position in which the stops 8, 9, are in contact and withdrawn by a crank 15 and a connecting- rod 14 so as to follow the orbital movement of the crank-pin. The crank and connecting- rod of variable length are connected to the outer end of the piston-rod 4a, and the work 7 and crank 15 are rotated together when the motor driving worm 11 is stopped. After the machining operation, the carriage is withdrawn rapidly by admission of oil under pressure to a port 5 at the left-hand side of the piston. At the end of this stroke, a switch 13 in the cylinder is operated by the piston and starts, in reverse, the motor driving the worm 11, which returns the stop 8 to the initial position before the motor is again stopped automatically. The movements of the carriage, effected by the crank mechanism, are assisted by an hydraulic cylinder 28, Fig. 6, on the carriage, and a stationary piston 29 controlled by a solenoidoperated valve 30, the cylinder also operating with cylinder 3. Movements of the carriage during the milling of non-cylindrical work, e.g. crank-webs, are controlled by a previouslymachined surface on the work, or by a template 43, Fig. 7, rotating with the work and engaged by the feeler 42a of a slide-valve 42 which may be connected into the hydraulic circuit of the cylinder 3. Fluid-pressure-control.-The cylinder 3 is supplied by a pump 18 through a slide valve 17 controlled by a solenoid-operated valve 16. As shown in Fig. 6, oil, fed to the valve 16 through a conduit 19, is supplied through conduit 20 to the left-hand side of valve 17 which, in this setting, feeds oil from pump-supplyconduit 21 to the port 6 of cylinder 3, the oil passing from conduit 21 into valve 17 through a valve 41 and conduits 22, 23. Oil discharged from port 5 passes through valve 17 to a conduit 24 and to exhaust at 25 through valve 41. In its other setting, valve 16 feeds oil to the right-hand side of valve 17, resetting the valve to supply oil to port 5 and connect port 6 to exhaust. The cylinder 28 for assisting the crank mechanism is supplied from a pump 31 and an hydraulic accumulator 40 loaded by compressed-air. In the forward traverse of the carriage, oil is fed to the right-hand side of the piston 29. For opposite traverse, oil is fed to both sides, the right-hand side of the piston having less effective area due to the piston-rod. During operation of the cylinder 28 with cylinder 3, the accumulator supplies the extra volume of oil required by the cylinder 28. Adjustable release valves 38, 39 are provided in the supply to cylinder 28. For control by the rotating template 43, valve 41 is re-set, Fig. 7, to connect to valve 17 conduits 44, 45, 46, from the valve 42. If feeler 42a is displaced, as shown, against the influence of the valve spring, oil from the pump 18 is fed to port 5 of cylinder 3 through conduit 22, valve 41, conduit 44, valve 42 and conduit 46 back to valve 41, from which it is fed through valve 17 to the port. Thus the carriage moves away from the work until valve 42 is returned by its spring and connects the pressure-line to port 6.