GB1107640A - Improvements in feed control means for rock drills - Google Patents

Abstract

1,107,640. Percussive drills. ATLAS COPCO AKTIEBOLAG. 24 Feb., 1967 [2 March, 1966], No. 8851/67. Heading B4C. [Also in Divisions B3 and G3] A rotary-percussive rock drill is supported on a slide 38 movable on a guide frame 45 and provided with a drilling tool 27, means 30, 32 for rotating the tool, and a pressure fluid operated reversible feed motor 48 connected to the slide and adapted to be controlled in either a forward or reverse direction, via a valve 70, in dependence on the torque developed in the rotating means. The rock drill comprises a hammer piston 21 having external splines for connection with a chuck 28 and provided with a nut 29 formed with helical teeth adapted to co-operate with corresponding teeth formed on a bar 30 which is rotatably mounted in the housing 20 of the drill; the bar is provided with a head 32 in which are pivoted pawls 31 for engagement with teeth 33 in the housing. The housing is provided with a knob 59 adapted to engage a plunger 60 mounted in a cylinder 61 which is connected via a conduit 58 with a cylinder 62; a plunger 63 is mounted in the cylinder 62 and is connected to a yoke 84 adapted to operate a pair of spring-loaded ball valves 78 in the valve 70. Conduits 87, 88 lead from the valve 70 to the feed motor 48, pressure fluid being fed into the valve via a conduit 70. In operation, pressurized fluid is fed, via a pipe 24 and valve 26, into the cylinder 22 for the hammer piston 21 thereby causing the latter to reciprocate and rotate the chuck 28 by means of the helical teeth in the bar 30 and the pawls 31; fluid is also fed to the feed motor to cause it to advance the slide 38 via a chain drive 49. In the event of the drill jamming, the reaction, on the rotating mechanism causes the housing of the drill to pivot about bearings 36, 37 so that the knob 59 depresses the plunger 60. Hydraulic fluid in the conduit 58, then acts on the plunger 63 to reverse the position of the ball valves 78 so that the feed motor retracts the slide. In a modification the plunger 60 is mounted directly within the housing and is actuated by means of a lug formed on a member carrying the pawls. In the embodiment shown in Fig. 7, the pawls 31 engage with teeth formed on a ring 33 rotatably mounted in the housing and provided with an arm 100 for engaging the plunger 102; the latter plunger is formed with passages 123, 124 and throttling grooves 121, 122 for controlling the supply of compressed air fed, via a pipe 106, to a servo piston 109 arranged to control the valve 110 connected to the feed motor 48. In a still further embodiment (Fig. 8), the pawl-and-ratchet rotating mechanism is replaced by a separate fluidpressure driven rotary motor (130) connected via a chain-and-sprocket drive (135, 138, 139) to the chuck the reaction between the motor and chuck when a tool jams being transmitted by a lever (141) to a piston-and-cylinder device (145), the liquid in the latter then operating the valve 70 as described with reference to Fig. 1.