| 摘要 |
A pneumatic screwdrive wherein the motor is started by opening a normally closed valve in automatic response to axial shifting of the tool spindle when the tip of the tool is pressed against a screw. The output device of the motor then drives a first coupling portion which drives a second coupling portion rotatably mounted on the tool spindle. The latter receives torque by way of an overload clutch having an annulus of balls mounted in the second clutch portion, a flanged sleeve movable axially of but rotatable with the spindle, a set of pins which are movable axially in a portion of the spindle, and an adjustable spring which determines the maximum torque to be transmitted to the tool spindle. The pins are driven by the balls, before the spring yields, to thereby rotate the sleeve. The valve is opened by a pair of spheres mounted in a diametral bore of the tool spindle and displacing a valve actuating rod when the spindle is moved toward the output device. The sleeve of the clutch has two radial bores which receive portions of the spheres to allow the valve to open when the spring yields in response to a predetermined resistance of the spindle to rotation with the output device. |
