Patent GB-393380-A (GB)
Title: Milling machines and like machine tools
IPC: B23C9/00
Filed: 1932-03-01
Abstract: 393,380. Milling-machines. HERBERT, SIR A., LLOYD, A. H., and JINMAN, C. H., Canal Road, Edgwick, Coventry. March 1, 1932, No. 6179. [Class 83 (iii).] Milling and like machines, wherein the table is automatically fed as by a worm connected with the spindle drive, have an arrangement wherein idle operations can be speeded up. The slidable member is driven by an electric motor with a control switch interlocked with the feed drive so that the motor cannot be energized for reverse operation so long as the feed drive is in operation. This may apply to the forward operation of the motor as well, or the feed drive may incorporate a one-way driving device or free-wheel. The interlocking may be mechanical or electrical and the motor is preferably reversible. When the motor is reversible the control switch can be set so that the latter will be automatically returned as soon as the feed drive is disconnected. In the case of a traverse-screw milling-machine,. Fig. 1, a control member in the form of a handle 2 can be raised to carry the driving worm into mesh to effect the automatic feed of the table as is well known. When raised the handle is retained till manually released by a pressbutton 4 or until an adjustable lug 5 on the table engages a releasing catch 6 on the stationary base 7 when milling is completed. A switch 8 is associated with the worm so as to be closed when the worm is disconnected and opened when the worm is in mesh. A stop and reversing main control switch 9, Fig. 2, is mounted on one side of the stationary base. The worm-controlled switch 8 is connected in series with the main control switch so that the motor cannot be energized as long as the feed drive is connected. An operating member 13 of the main control switch can be moved to three positions-forward, reverse, and off, Fig. 3 (a). Adjustable lugs 15, 16, 17 automatically operate the member 13 for slow feed, rapid feed or stop. Apart from automatic control the operator can move the main control as desirable to move the table in either direction rapidly provided the feed drive is disconnected. In some cases the table can be operated manually by a hand-wheel 18 adapted to drive a clutch and bevel gears in a casing 19. The first movement of the hand-wheel in a clutchengaging direction opens a switch 21 in circuit with the motor. This switch is in series with the main control 9. Normally after completion of the feed the table is returned automatically but the operator can prevent it by moving the hand-wheel to open the switch 21. In practice an electromagnetic contactor reversibly controlled by the series switches would be used. In a modification, Fig. 5, a power traverse is operated only manually and a motor 11 (reversible) is mounted on the left hand and the main switch is operable by a member 13 through a connecting-rod 24. A spring (not shown) tends to keep the operating handle 13 in the off position. A spring-loaded plunger carried by the handle co-operates with two collars 25 on the connecting-rod so that the handle can be fully raised only when the operating member 13 is in the off position. In a further modification, Fig. 7, provision is made for automatic control of the power traverse in both directions and for introducing power traverse intermittently during forward feed where sections in casting need no machining. A double-acting switch is used having a second member 8a to close contacts when the switch 8 is opened and vice versa. In this case there is no main control switch 9, 13, but in the position of the latter there is a normally closed limit switch 26. At the rear of the machine there are stop and start switches co-operating with adjustable stops on the table. The control circuit is shown at Fig. 10. In the loading position the hand-wheel switch 21 is closed and the feed drive disconnected. The switch 8 is closed and 8a open. The contactors are both open, bridging the lower contacts 32, 33. The stop switch 27 is closed and the start 28 is held closed by one of the adjustable stops and the limit switch is held open by the limit stop 16. The two parallel control circuits are then open at the switches 8a, 26 and the motor is de-energized. When the work is set up the operator completes the feed drive by raising the control 2 opening the switch and closing 8a, completing a circuit from the lead 31 through contacts 33 of the reverse contactor 23b through the stop 27, start 28 and handwheel switch 21 exciting the coil of the forward contactor 23a which therefore operates. As the worm has been raised to engage the worm wheel, the automatic feed drive is provided with a one-way device and free-wheel. After a determined forward movement an adjustable stop operates a stop switch 27 opening the circuit and de-energizing the forward contactor. Thus the automatic feed drive is effective whilst a milling operation is being carried out. When this is finished another of the adjustable stops engages the start switch 28 and thus operates the table again, and so on.