GB191013716A - Improvements in Tools or Machine Operated by a Reciprocating Element and in Means for Driving them Electrically. - Google Patents

Abstract

13,716. Crawford, R. S., and Scott, J. June 7. Percussive drills.-The armature or plunger 15, Fig. 1, of an electrically-operated percussive rock or like drill is reciprocated by solenoids 11, 12, which are supplied with pulsating currents from a continuously-wound armature coil 7 through a collecting-device adapted to deflect the current from one to the other solenoid at the zero points of the voltage wave. Fig. 3 shows a rock drill having an impact-piece 28 which directs the blows of the hammer 15 on to the end of the tool steel 29. The solenoids 11, 12 are mounted between inner and outer casings 16, 18, and, for feeding the cutting tool, may be slid axially in an outer guide cylinder 31 by means of a feed-screw or by fluid pressure; the pressure air or water may be passed round the solenoids to cool them. To effect this, the solenoids are encased in copper or like sheathings 17 so as to leave inner and outer fluid - tight spaces 19, 20 which are perforated at 38, the rear cap 30 being provided also with perforations 39. The air or water entering at the inlet 41 flows through the spaces 19, 20 and perforations 39, and passes out through an outlet 42 into a flexible tube 43 provided with a tap 46 for regulating the feed; the fluid then enters an annular recess 44 in the impact-piece and flows through an axial duct to the cutting-nose of the tool, thus cleaning the drilled hole of chippings &c. The guide-tube 16 is furnished with grooves 16<b>, which cause air to be expelled from the front of the hammer on the forward stroke, but allow a certain amount of air to be pocketed at the end of the rear stroke so as to cushion the hammer. To allow adjustment, the outer cylinder 31 is gripped by a divided socket 48 provided with a clamping-bolt and having an undercut boss 50, which in turn is gripped by a split yoke made in two parts 51, 53 and adapted to be secured to the jack-pole; the part 53, either pivoted to the part 51 or left loose, is secured by means of a bolt 54. By this arrangement, the tool may be set at any angle, and may be brought close to the roof or floor.