Patent GB-453800-A (GB)
Title: Improvements in or relating to drilling machines having electric feed mechanism
IPC: B23Q16/00
Filed: 1935-07-31
Abstract: 453,800. Drilling machines. HERRMANN, R., 22, H÷lderlinstrasse, Stuttgart, Germany. July 31, 1935, No. 21679. Convention date, July 31, 1934. [Class 83 (iii)] [See also Group XXXVII] An automatic drilling-machine, particularly for long holes, of the kind in which the drilling spindle is rapidly retarded a predetermined number of times during the drilling operation and each time advanced to the depth previously reached, and in which an auxiliary electric motor for varying the feed operates on the spindle through a differential gear, has a reversing switch with positions for reverse running, forward running and stoppage of the auxiliary electric motor and a locking device which locks the switch in the " off " position during the drilling feed. The drill 42 is rotated through toothed gearing by the main electric motor A, Fig. 1, a secondary drive from this motor rotates through worm gears 17, 18 and pick-off wheels 20, 21, Fig. 2, the bevel wheel 23 of a differential train, the planet-carrying wheel 28 of which is driven from the auxiliary motor V. The differential train drives through the spur wheels 25, 35, the pinion 36 engaging the feed rack 37 on the spindle sleeve. A further pinion 43 engages the rack and this is arranged to drive through spur gears a shaft 47 on the ends of which the stops for operating the motor switches are arranged. Three switches E, S, H, Fig. 15, are provided these are respectively-the reversing switch for the auxiliary motor ; a safety switch adapted to operate only when the drill is overloaded and the main switch. The latter is adapted in both " on positions to supply current for forward rotation of the motor A, but in the upper position the safety switch and auxiliary motor circuits are switched in. The switches E and H are " snap switches and are adapted to be held in their intermediate " off " positions by releasable stops 73, 74, Fig. 3. At the start of a working cycle the stop 74 is released by hand or electromagnetic means and allows the switch arm 63 to fly over to a position opposite to that shown in Fig. 3, the bridle of the snap switch also occupies a position opposite that shown ; the main driving motor is thus set in motion the switch being against the contacts 60 of Fig. 15. A stop 87 fastened to a carrier 48 keyed to the shaft 47 rotates anticlockwise, Fig. 3, and, almost immediately the main motor is started, throws over the switch H into the position shown and thus completes the circuit to the auxiliary motor which has been moved previously into the forward feed position. The feed of the spindle then takes place at high speed until a stop 91 engages the switch arm 93 which moves the switch E to its inoperative position ; through the differential gear, the feed is thus reduced to a cutting one and the drill enters the work at this point. The stop 91 does not move on further with the carrier 48 to which it is connected by friction discs, but is held stationary during cutting by a rocking stop 106, pivoted to it at 105, contacting an adjustable stop 108. Adjustable stops 123, Fig. 4, arranged on a disc fixed to the other end of the shaft 47 rock a lever 124 which after a double movement releases the stop 73, Fig. 3, allowing the switch E to move over to effect a rapid withdrawal of the drill to the surface of the work corresponding to a further stop 90 which again reverses the switch E and starts another cycle with a rapid forward feed. The stop 91 in slipping has been moved back a distance equal to the depth of hole drilled so that rapid feed is continued until the undrilled part of the work is reached. After a predetermined number of cycles a stop 114 on the shaft 47 strikes a stop 112 on the rocking lover 106 rotating it anticlockwise and releasing, through a tripping mechanism (not shown), the pivoted stop 90 so that the latter swings back and is ineffective in moving the switch E over to the reverse position ; retraction of the spindle is thus continued until the stop 87 moves the switch member 89 to throw the main switch H into its " off " position and stop the machine. The stop 91 is returned to its initial position by a stop 110 holding it against rotation through the lever 106 while the stop carrier 48 is rotated clockwise during the return movement of the spindle. A safety device against overloading of the drill is provided, the feed pinion 36, Fig. 2, having oblique teeth which cause it to move laterally against the pressure of a spring 39, this movement is transmitted by levers to the safety switch S which is thrown out to stop the machine. This arrangement is also adapted to operate on the torque exceeding a predetermined amount by providing a friction clutch 41, Fig. 1, between the drilling spindle and the drill.