Patent GB-293856-A (GB)
Title: Improvements in impact tools
IPC: B25D9/10
Filed: 1928-06-15
Abstract: 293,856. Pennsylvania Gasoline Drill Co., (Assignees of Schmidt, L. A.). July 14, 1927, [Convention date]. Percussive tools.-A two-stroke-cycle, internalcombustion, percussive tool, utilizing a transversely-mounted cam-operated rotor as described in Specification 219,202, has the body in three main parts, a combustion chamber 2, a cross-head guide 3, and a mixing chamber 5, the latter attached to an air-compressing chamber. All the parts are held together by longitudinal bolts 17, 19, 30, 55, the latter bolts also holding the oil chamber 52 in which lies the lower part 95 of the rotor 116, which is carried in ball bearings 110, 114 and co-operates with the cross-head rollers 83 by means of cam surfaces 105, 106. The several parts of the body are chrome nickel-steel drop forgings, each heat-treated to a different (stated) degree according to the wear required of it, the slots 47 in the guide 3 being case-hardened. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the following subject-matter. The chamber 6 is closed by a chuck 68 held by spring bolts 72 with locking ribs 341 on the springs, and supports a block 61 in which slides a pin 62 transmitting the blow to the tool. The chamber 6 is sealed by oil grooves 67 in the block 61 and air compressed in the chamber is conveyed by a bore 63 in the pin 62' to the hollow drill for clearing the bore hole. This cushioning pressure is controlled, so as to regulate the force of the blow, by an adjustable) relief valve 279 in a chamber 250 communicating with the chamber 6 by a port 246. Outside the chuck 68 are flanged collars 153, 156 held apart by a spring 155, and a drill retainer 163 is pivoted as shown. Above the rotor is fixed a cover plate 42 to which are bolted handles 122. A steadying framework of tubular rods 164 is also provided, together with a thigh piece 173. The cover 42 is formed with a pocket 124 to hold the ignition unit, comprising a primary coil 322, connected between a battery 319 and a timing contact 288, and a secondary coil 326 connected to the sparking plug 29 by a single short lead 126. A condenser 328 is provided, connected as shown. A recess 129 in the cover 42 accommodates the timing mechanism 117, which comprises a stationary contact screw 288 and a. movable contact 300 raised against a spring 306 by the action of two cams 133, formed on plates 132 mounted at opposite ends of a diameter on the upper surface of the rotor 116. Oil from the lower part 143 of the oil chamber 52 rises through tubes 144 to lubricate the rotor, being retained in the part 143 by a flange 142 when the tool is inclined to the vertical. The fuel tank 177 is bolted to the rod framework 164 and communicates by a pipe 186 with the carburettor 192, which is provided with a needle, valve 199 operated by an arm 206 working over a quadrant 210. Fuel passing the valve 199 proceeds by a passage 211 to the seat of the air inlet valve 213, and thence to the mixing chamber 5, the mixture charge being forced on the down stroke through a pipe 35 to the cylinder inlet port 32. A removable sleeve 244 is provided to adjust the capacity of the mixing chamber 5. Exhaust escapes from the cylinder by ports 33, and is deflected by plates 36 away from the operator's hands, This subject-matter is not described in detail in the Specification as accepted. In a modified construction (not shown) a single chamber is substituted for the two separate chambers 5, 6.