Patent ID: 8590905
Filing Date: 2013-11-26
Classification: B25D,Y10T

Abstract:
1. A chuck mechanism of a striking tool, comprising: a cylindrical tool holder in which a rear end of a bit is inserted from a front end of the holder; two balls configured to roll through a predetermined distance in an axial direction of the tool holder in a pair of accommodation holes provided in the tool holder and are configured to move through a predetermined distance in a radial direction of the tool holder; a contacting member which is externally mounted on the tool holder to force the balls to respective front positions of the accommodation holes by at least one biasing device; an operation sleeve which is externally mounted on the tool holder so as to be movable back and forth between a lock position, in which a pressing ring provided at an inner periphery of which is located on an outside of the balls at the front positions to project the balls radially inwardly from the tool holder, and an unlock position, in which the pressing ring retracts rearward from the outside of the balls at the front positions to allow the balls to retract radially outwardly from the tool holder; and a holding device configured to hold the pressing ring and the operation sleeve at an advance position, wherein when the rear end of the bit is inserted into the tool holder, each ball is rolled rearward by contact of the rear end of the bit and pushed in between the pressing ring and the contacting member and retracted radially outwardly from the tool holder, in a state where the pressing ring is held at the advance position by the holding device, wherein the contacting member is configured to allow one of the two balls to retract radially outwardly from the toolholder before the other of the two balls in response to the rear end of the bit coming into contact with the balls and rolling the two balls rearward.