GB286600A - Improvements in or relating to electric drilling apparatus - Google Patents

Abstract

286,600. Contal. C., and Krettly, P. March 5, 1927, [Convention date]. Drilling-machines.-In a portable electric drilling- machine the armature shaft 5 is coaxial with the chuck 20 and carries at one end a cooling fan 6 and at the other end a bevel pin on 10 engaging a similar pinion 11 on a transverse shaft 12. The latter is of non-circular section, preferably square, and is mounted by ball bearings in an opensided pressed steel frame 9. A toothed wheel 14, slidable, on the shaft 12, is adapted to engage one of a concentric series of circular rows of perforations in a disc 15, the row which is engaged determining the speed at which the chuck 20 is rotated. A hollow shaft 16 secured to the disc is received within a hollow shaft 19 carrying the chuck and the drive is transmitted from one shaft to the other by a key 18 passing completely through the central shaft and entering elongated slots in the outer shaft. A spring 17 in the inner shaft normally presses the key against a cap 22 secured to the outer sleeve, but to change the speed of the drive the disc may be depressed against the pressure of the spring. In a modification the disc and chuck are secured at opposite ends of a single solid shaft which is rotated within a sleeve attached to the frame 9 by a screw-thread, bayonet joint or similar connection to allow the disc to be raised and lowered. The casing 2 which supports the motor may be secured to the frame 9 with the interposition of a member 8 which carries the commutator brushes 7a, or the frame 9 m ay be extended upwardly to enclose the motor aad the transmission shafts. A breast pad 4 is rotatably attached to the cover 3 of the casing 2 and a pair of handles are pivotally attached to the member 8 or the frame 9.