Patent GB-921741-A (GB)
Title: A machine tool
IPC: B23Q16/00
Filed: 1960-10-31
Abstract: 921,741. Milling. KEARNEY & TRECKER CORPORATION. Oct. 31, 1960 [Dec. 7, 1959], No. 37293/60. Class 83 (3). A machine tool comprises a movable cutter on a spindle 20 and a reciprocable work-table 22 carrying dogs, including a stop dog, to actuate switches on the machine base to cause the support to move at different speeds and in different directions, and manual means for effecting continued movement of the table after a switch has been actuated by the stop dog. The cutter is rotated by a motor through an electromagnetic clutch and change-speed gear and is carried in a vertically-adjustable spindle head 18 having over-arms 19. The dogs are mounted in a groove 28a on the table 22 and co-operate with four switches each mounted at a different level on a support 34 which also carries pushbuttons 35L, 35R, for initiating left and right table movement, and a rapid traverse button 36. Dogs 53R, 53L, Fig. 5, are over-travel safety switches. The table 22 is moved by a screw 23 rotated by a second motor 24 through changespeed gearing, an electromagnetic feed clutch, an electromagnetic rapid traverse clutch, which rotates oppositely from the feed clutch, and two electromagnetic reversing clutches. The two latter clutches may be simultaneously actuated to lock the table, the other clutches being disengaged. Both motors are switched off automatically if any electrical overload should occur in the machine control circuit. The motors are controlled from a box 37. Push-button 39A starts both motors, energizes the reversing clutches and a spindle brake, button 39B stops both motors, button 39C stops the table, button 39D stops the spindle, switch 38A controls the direction of rotation of the spindle motor, switch 38B is set to give continuous rotation of the spindle or to prevent rotation of the spindle during rapid traverse movements of the table, switch 38C sets the spindle motor for " jog " or " run," and switch 38D gives manual or automatic control. In a typical cycle illustrated in Fig. 6 depression of the button 35R starts table movement to the right, and an indicator lamp to light up, the cycle continuing until the button 39C is actuated. The table moves to the right at feed speed, although this portion of the travel in subsequent cycles occurs at rapid speed,- being changed to feed speed when the dog 46 engages the switch 32. The table commences a rapid return left when switches 30, 32, 33 are sequentially actuated by dogs 44, 45. (If the dog 44 were to be omitted, the table would travel left at feed rate.) Rapid traverse left continues until the dog 50 engages the switch 31 causing an immediate change to feed rate. The immediate change is due to the effect of braking in the transmission due to the reversely-rotating feed and rapid traverse clutch members. Subsequently, the dogs 51, 52 actuate the switches 33, 31, 30 and the table reverses at rapid rate. At reversal, both directional clutches are engaged momentarily to provide a braking effect. Each dog thus affects the feed only in one direction, it being inoperative when moving in the opposite direction. Depression of the button 39C stops the cycle at any point with the reversing clutches engaged to lock the table. By inserting a dog 60, Fig. 5, at the centre of the slot 28a, the table is stopped in its central position by actuation of switches 30, 33 and may be started at rapid rate in alternate directions by depression of buttons 35L, 35R. Workpieces at opposite ends of the table may thus be machined alternately, with a safety check stop being made between operations. A similar function may be performed by dogs actuating switches 31, 32. With the switch 38D set for manual control, depression of the buttons 35L, 35R moves the table at feed rate which can be changed to rapid traverse by the button 36. The table is stopped by button 39C. The table is also stopped by the automatic stopping dogs such as 60 or by the safety limit dogs 53R,. 53L which render the associated buttons 35R, 35L inoperative. The table can also be handcranked by moving a crank arm to engage a clutch and to actuate a switch to de-energize the reversing clutches. The clutches may be replaced by hydraulically operated plate or tooth clutches.