Patent GB-219202-A (GB)
Title: Improvements in impact or percussive tools of the explosive motor type
IPC: E21B1/34
Filed: 1923-09-03
Abstract: 219,202. Somervell, C. S. Sept. 3, 1923. Percussive tools.-In an internal-combustion percussive tool the return stroke of the hammer piston 16, which is the compression stroke of the motor piston 15, is effected by a flywheel 127 which rotates on ball bearings 52, 81 and carries two pairs of cams 57, 77 engaging rollers 66, 71 on a pin 18 mounted on a central cross-head 17 sliding in slots in the cylinder wall and rigidly connected to both pistons. The lower cams 77 acting on the rollers raise the cross-head during the action of the parts f of the cams, whilst the cross-head drives the fly-wheel during the action of the parts b, and parts d of the cams are so shaped as to leave the cross-head free during the last part of the power stroke up to the moment of impact. The upper cams 57 are provided for effecting initial compression at starting, by the action of the parts k. Fuel is forced from a tank 36, by means of a hand-operated air compressor 166, to an inlet 35 in the seat of an airinlet valve 33 leading to the fuel-mixing chamber 29 in front of the motor piston. Fuel and air are transferred to the explosion chamber by a pipe 40, and exhaust takes place through a port 42. Ignition is effected by means of a contact 192 connected to the primary winding of an induction coil 164 and adapted to be engaged by a movable contact 193 when the latter is raised bv a cam 194 carried bv the fly-wheel 127. The contacts 192, 193 are mounted in a housing 197 adjustable longitudinally for varying the time of ignition. The induction coil 164 and condenser 165 of the ignition system are housed in recesses in the fuel tank 36. Lubrication is effected bv inclined tubes 209 in the fly-wheel, which pick up lubricant from a pan 87 and discharge it against the working parts, a return duct 210 being provided. The pan 87 has an oil-tight joint 90 and is locked by a washer 91 with prongs 95 which are bent into notches on the pan and in a nut 92. The cylinder head is secured by T-headed bolts 6. The motor piston is hollow and stiffened by a stud 45. The motor cylinder is closed by an annular packing disc 21 held by rings of screws 24, 27. The cross-head pin 18 may be secured by means of a screw 76 with a notched head, locked by bending up one or more prongs 17<d> on a locking washer 17<c>. The lower end of the hammer cylinder forms an air-compression chamber 129, being closed by a block 97 held in place by the tool holder 100 and spring bolt 101. A sliding pin 112 transmits the blow to the tool, and is arranged to project above the block a distance equal to the average advance of the tool at each blow. The tool is retained by a yoke 119 and springs 122. The hammer piston 16, in ascending, draws air in through a passage 134 provided with a filter 135 and a port 130, and, in descending, forces part of the air through a passage in the pin 112 and through the hollow drill to clear the bore. The degree of cushioning in the space 129 is controlled by an adjustable relief valve 140, and the escaping air is led by a passage 152 back to the air-inlet passage 134, and acts to blow dust out of the filter 135. An additional port may be provided whereby air is taken from the space 129 through a removable pipe to cool the cylinder head. The pin 112 may be solid, in which case an outside pipe is provided for conveying the compressed air to the hollow drill. The tubes 159 which support the fuel tank 36 also carry a plate 176 adapted to rest against the operator's leg. A modified construction is described wherein the fuel mixing chamber is at the lower end of the tool cylinder and the air compression chamber at the upper end.