GB942311A - Improvements in or relating to pneumatically driven tool for marking, carving and light hammering - Google Patents

Abstract

942,311. Percussive tools. PNEUMATIC TOOL SALES & REPAIR CO. Inc. March 11, 1960, No. 8669/60. Heading B4C. A percussive tool comprises a casing having a bore of increased diameter at an intermediate portion, a piston reciprocable in the intermediate portion and having an end projecting externally of the casing, a spring urging the piston in a direction opposite to its projecting end, and a valve integral with the piston to supply compressed air to the face opposite the projecting end to drive the piston in a working stroke and to cut off the air supply during the end portion of the working stroke to permit the spring to return the piston to its initial position. As shown, the casing comprises two portions 1, 2 joined by bolts 5 in the enlarged portions 3, 4 and has a bore 9, a counter-bore 9<SP>1</SP> of larger diameter, an increased diameter bore comprising a bore 8 of larger diameter than the bore 9<SP>1</SP> and a bore 7 of diameter between those of bores 8 and 9<SP>1</SP>, a bore 18 and a bore 22 of larger diameter than bore 18. A discshaped piston 12 is supported in the bore 7 and has a rod-shaped part 11 extending externally of the casing 1 and a rod portion 20 extending on the opposite side through the bore 18. The portion 20 has a flat 19 such that the bore 18 is open to the bore 22 at the end of the return stroke, as shown, but is closed to the bore 22 when the piston 12 has moved nearly to the end of the working stroke. A spring 13 returns the piston to the shown position at the end of the working stroke. Pressure air enters the bore 22 through a manually controlled valve 28, drives the piston against the spring until the piston enters the bore 8 when air may escape round the periphery of the disc and exhaust to atmosphere through vents 27. The disc may be guided on a pin 24 and the end of the rod extending through the casing may be provided with a chuck 15.