GB540239A - Impact wrench - Google Patents

Abstract

540,239. Screwing up nuts &c. CHICAGO PNEUMATIC TOOL CO. July 25, 1940, No. 12151. Convention date, Nov. 22, 1939. [Class 83 (iii)] An impact wrench for operating nuts &c. by means of a series of hammer-like blows is constructed with a socket 76, Fig. 1, connected to a spindle 35 fitted with an impact clutch comprising anvil-like extensions 37 which are adapted to be engaged by pivoted hammer dogs 60 connected by pivot pins 61 to a squirrel-cage mounting 50, 55 adapted to be driven by the rotor shaft 30 of a rotor 31 driven by an air motor 23, mounted in a portable housing 20 fitted with a pistol-grip handle 21 and having attached to it a housing 19 for the clutch members. The dogs 60 are driven by a cam 51 splined to the shaft 30 which engages a groove in each dog and imparts momentum to the driving part of the clutch prior to the engagement of the driving and driven surfaces 67, 68, Fig. 10. These remain in driving engagement if little resistance is encountered, but in case of a frozen nut the resistance causes declutching of the driving-dogs 60 due to a slight rebound of the driving-member and the continued motion of the cam 51 acting to rotate the dog 60 counter clockwise. This action is resisted by friction and by centrifugal force and is due to constructing each dog 60 so that its centre of gravity is below the axis of its pivot 61. Cam surfaces 65 on the dogs 60 and 66 on the driven member maintain the dogs in declutched position as shown in Fig. 14, until finally the cam surfaces 65, 37 move the dogs into clutching position as shown in Fig. 12 in which position a hammer blow is about to be delivered. The wrench socket 76 is driven by a polygonal projection 74 of the spindle 35 and is fitted with a locking pin 78 which fits tightly in the projection and loosely in the socket head and is held therein by an elastic band 81. The shank 36 of the tool head is mounted in a steel bushing 39 surrounded by a resilient sleeve 40 of oil resisting synthetic rubber "Neoprene" (R.T.M.) which is formed with an annular groove 46 to permit grease inserted through an opening normally closed by a plug 45 to pass through ports to an annular groove 47 in the inner surface of the bushing 39. The dogs 60 and their mounting are symmetrical and can be inverted so as to change the driving edges to allow of longer wear.