(a) Field of the Invention
The invention relates to a chuck of an electric drilling tool, more particular to an anti-slip type electric drill chuck.
(b) Description of the Prior Art
A conventional electric drill chuck structure generally has a body connected to a rotary shaft of a motor. The motor is externally provided with an adjusting housing for local rotation. The body has a plurality of slanting pawls annularly disposed thereon. The user can adjust the adjusting housing with his/her hand to control the advancement or retraction of the pawls in an oblique direction to thereby clamp or release a drill head.
Such a mechanism of using the hand to manipulate of the adjusting housing so as to control advancement or retraction of the pawls may, due to factors such as vibration of the drill head, torque, resistance on drill surface, etc. during the drilling operation, cause the engagement between the pawls and the drill head to become loosened so that it is necessary to stop the machine and lock the drill head again. Otherwise, the drill head will deviate and is likely to be damaged. The drill surface is also likely to be damaged.
The primary object of the invention is to provide an anti-slip type electric drill chuck, in which a front housing sleeve of a chuck unit is rotated by hand to control the chuck unit to clamp or release a tool such as drill head. When the chuck unit clamps the tool during operation, the chuck can prevent slippage of the drill head due to counteractions of vibration, torque, resistance, etc., resulting from the drilling operation.
In order to achieve the abovementioned object, an anti-slip type electric drill chuck of the present invention mainly includes a body which is obliquely provided with three pawls for clamping a drill head. The outer surface of one end of the three pawls is provided with a threaded surface for engaging a tapered threaded hole in a bearing nut, which has an outer end with teeth, an end portion provided with a ball ring. A check nut protective sleeve encloses the ball ring and bearing nut, and has elastic pointed portions engage the teeth. A drive annular block engages the inner wall of the bearing nut. A front housing sleeve engages the drive annular block and surrounds the aforesaid components.