GB980539A - Impulse tool - Google Patents

Abstract

980,539. Nut runners. THOR POWER TOOL CO. Jan. 7, 1964 [Jan. 8, 1963], No. 678/64. Heading B3N. A nut runner comprises a reversible rotary air motor 26, Fig. 2, controlled by a throttle valve 28, and an impulse unit 31, mounted in a casing 21, and including an output spindle portion 32. Unit 31, Figs. 5, 6, comprises a housing assembly 41 driven by motor 26 at 73, and an internal spindle 42, having the portion 32 projecting therefrom. Assembly 41 includes an outer casing 43, a bushing 47 having an eccentric bore 48 press-fitted into casing 43, and end caps 49, 51. Spindle 42 has a polygonal cross-sectioned portion 62, and a short stub shaft 63, journalled in cap 51. Bore 48 is filled with oil or the like through a plug 71, and has a pair of circumferential recesses 81, interrupted by lands 82, 83. Spindle portion 62 has a slot 86 which loosely carries a T-shaped blade 87 urged outwardly by springs 91. In operation, assembly 41 including bushing 47, Fig. 10, is being driven in a clockwise direction, and a nut is being tightened. The frictional engagement of blade 87 with bore 48, is sufficient to cause spindle 42 to rotate in a clockwise direction. When the torque resistance increases as the nut is tightened, assembly 41 rotates relative to spindle 42, and as the oil in bore 48 is free to flow through recesses 81, the pressure in the bore is uniform. As assembly 41 continues to rotate, the volume of bore 48 below spindle 42 gradually increases, and the volume above the spindle decreases. When lands 82, 83 are in engagement with blade 87, and spindle edge 84, the oil is no longer free to flow, and the pressure in the upper part of the bore increases and provides an impact to the spindle, which is repeated as assembly 41 is rotated. A small static leakage is provided between caps 49, 51, and spindle 42, and grooves in the caps may be provided for this purpose. Pressure under 0-ring 54, Fig. 5, is relieved by a bore 97, which passes into the low pressure part of bore 48. The pressure exerted by springs 91 is not sufficient to achieve a dynamic seal between blade 87 and land 82, therefore the high pressure fluid passes down slot 86, and acts on the inside end of the blade. In a modification, spindle 42 is driven by motor 26, and cap 49 mounts the tool. An adjustable pressure relief valve 109 is provided, and is connected to the HP and LP parts of bore 48 and an expansion chamber 126, Fig. 7, controlled by a piston 130, is provided for the oil. In a further modification, spindle slot 140 carries a close-fitting blade 141, Fig. 16.