Patent GB-346749-A (GB)
Title: Improvements relating to the feed mechanism of planing and like reciprocating machine tools
IPC: B23D7/00
Filed: 1930-01-08
Abstract: 346,749. Planing &c. machines. CLOWES, S., 1, Horwood Crescent, Withington, Manchester, STOTT, S. H., Milford, Woodville Grove, South Reddish, and CRAVEN BROS. (MANCHESTER), Ltd., Vauxhall Works, Reddish, both in Lancashire. Jan. 8, 1930, No. 699. [Class 83 (iii).] In a feed mechanism for a reciprocating machine such as a planing machine an electric motor which actuates the feed is started at the correct time by the usual reversing dogs and switches, and after rotating for a predetermined number of revolutions is stopped by a rotary switch which is driven through variable speed gearing from the motor. The number of revolutions performed by the motor is determined by the variable speed gearing and the rotary switch sets itself ready for the next period of operation. The motor drives a shaft c, Fig. 1, through a chain and sprocket b, the shaft c serving to drive a parallel shaft d through a clutch j and either a direct drive f or a reverse drive h. The shaft d drives a shaft t through one of the gear pairs k, p .. o, s which is selected by a sliding key in the shaft t and a rack w operated by a pinion x and a handle y. The rotary switch 25 comprises contact segments 5, 6, 7 secured to a shaft z which is coupled to the shaft t by a loose coupling 13, Fig. 3, which, in conjunction with a notched cam 11 and a spring plunger 12 allows the segments to move in advance of the shaft t at each half revolution and thereby cause a quick make-or-break with the stationary contact fingers 8, 9 or 10. A main switch 39, Fig. 6, for the motor a is provided and the direction of rotation of the motor is selected by a reversing switch 52. A switch 24, Figs. 1 and 6, is actuated by a rack-bar 22 and a toothed segment having a lug lying in the path of the handle y so that when the latter is moved into any position causing the rotary switch 25 to be coupled to the motor, as indicated by a pointer j<1>, the switch will be moved to the lower position in Fig. 6 to institute automatic control of the feed through the rotary switch 25, whereas when the handle y is moved to disengage the key from any of the gears p .. s the switch will be moved to the upper position to cut out the switch 25 and enable control to be effected through pushbuttons 48. A switch 31 is hand operated in conjunction with a change-gear lever, to throw the automatic control to a switch 35 for tool-box feed and table traverse or to a switch 46 for table feed and tool-box cross traverse. In operation, with the rotary switch 25 connecting contacts 8, 9, the switch 35 is oscillated by the reversing dogs of the table to close contacts 34, 34a, thereby connecting a supply lead 26 to a coil 36 which closes a switch 36a and completes the armature and series field circuit 37 of the motor. The shunt field circuit 38 being closed by the main switch 39, the motor rotates until the switch 25 has been rotated half a revolution, the time taken for this depending on which of the gears p .. s is engaged. The relay circuit to the coil 36 is thus broken at 8, 9, but a resistance 43 remains connected by the contacts 41, 42 across the armature of the motor to constitute a dynamic brake and bring the motor to rest immediately. Simultaneously with the breaking of the contacts 8, 9, the rotary switch 2 connects contacts 9, 10 before coming to rest so that the next oscillation of the switch 35 by the reversing dogs will again complete the relay circuit through contacts 34, 34b to start the motor in the same direction for the next feed movement. Actuation of the switch arm 28, 40 to give hand control of the motors a through pushbuttons 48 cuts out the braking resistance 43 and short circuits a portion 51 of the motor series resistance to give a higher speed for hand setting. The reversing clutch j, Fig. 1, enables the rotary switch to be actuated always in the same direction when the feed is reversed by reversal of the motor a. Limit switches (not shown) are provided to stop the feed and driving motors if the part being fed or traversed should over-run.