| 摘要 |
1,043,387. Impact screwdriver. ROBERT BOSCH G.m.b.H. Sept. 13, 1963 [Sept. 15, 1962], No. 36102/63. Heading B3N. [Also in Division F2] A hand held electrically driven rotary impact screwdriver comprises a hammer 26 having claws 27, 28 which co-operate with claws 30, 31 on an anvil 29, and a shaft 21 rotatable from a motor 10 through gears 15-20 and carrying claws 23 for engagement with claws 49 on a shaft 32, the latter being connected to hammer 26 by balls 34a, 34b. Shaft 32 has two grooves 35a, 35b for the balls and carries a loosely mounted hub 42, slidable in the bore 45 of hammer 26. The latter is urged downwardly to engage the anvil by a spring 33, and the balls engage grooves 46a, 46b, in the bore 41 of the hammer. A spring 47 located in a blind bore 36 of shaft 32 engages shaft 21 to maintain disengagement of lugs 23, 49. In operation with a wrench placed on the end 48 of the anvil, pressure is applied to the tool, thus axially displacing the anvil, and shaft 32, against spring 47, and engaging claws 23, 49. When the resistance offered by the screw reaches a value which overcomes the spring 33, the hammer is retarded. It moves upwardly to compress spring 33, balls 34a, 34b roll from the ends 50 of grooves 35a, 35b towards ends 51, and are held along the axial wall of grooves 46a, 46b in the hammer, thus causing the hammer to disengage claws 30, 31 from claws 27, 28. As soon as the disengagement occurs spring 33 is relieved, causing the balls to move to ends 50 of the grooves and imparting a rotary acceleration to the hammer. The hammer moves axially to engage the anvil and imparts a tangential blow to the latter. Grooves 35a, 35b each extend over a circumferential angle of 200 degrees so that as the hammer recoils the balls are prevented from reaching the ends of the grooves and allow shaft 32 to take the hammer along with it. |
