Quick-action locking device for an electric power tool

1. A quick-action locking device for an electrical power tool and designed for securing a working tool ( 3 ) to a motor-driven hollow spindle ( 2 ) located in a housing ( 1 ) of the power tool, the quick-action locking device comprising a locking spindle ( 4 ) axially displaceable in the hollow spindle ( 2 ) of the electrical power tool; a resilient member ( 5 ) for axially restraining the locking spindle ( 4 ); a locking flange ( 7 ) cooperating with the locking spindle ( 4 ) for securing the working tool ( 3 ) to the spindle ( 2 ) for joint rotation therewith; and a locking lever ( 6 ) provided at an end of the locking spindle ( 4 ) remote from the working tool ( 3 ) and pivotable about a pivot axis ( 9 ) between a locking position, in which the working tool ( 3 ) is secured to the spindle ( 2 ), and an exchange position in which the working tool ( 3 ) can be replaced, the locking lever ( 6 ) having a slider ( 8 ) for applying a force to the locking spindle ( 4 ) for displacing the locking spindle ( 4 ) against a biasing force of the resilient member ( 5 ) upon a pivotal movement of the locking lever ( 6 ) from the locking position to the exchange position, the slider ( 8 ) having a contact region engageable with a contact surface ( 11 ) provided at the end of the locking spindle ( 4 ) remote from the working tool ( 3 ),

wherein the contact surface ( 11 ) of the locking spindle ( 4 ) has a length (K) corresponding to at least a distance (a) between a point of contact of the contact region of the slider ( 8 ) with the contact surface ( 11 ) of the spindle ( 4 ) in the locking position of the lever ( 6 ), and the pivot axis ( 9 ) of the locking lever ( 6 ), multiplied by sin (α) of an angle (α) formed by a line passing through the contact point and the pivot axis ( 9 ) of the locking lever ( 6 ), with a longitudinal axis of the spindle ( 4 ); and

wherein the slider ( 8 ) is formed as an annular support member having a predetermined constant radius (R) and an axis of which extends parallel to and spaced from the pivot axis ( 9 ) and wherein the radius R runs from the axis of the annular support member.

2. A quick-action locking device according to claim 1 , wherein the angle (α), which the passing line forms with the longitudinal axis of the locking spindle ( 4 ), amounts to from 30° to 120°.

3. A quick-action locking device according to claim 2 , wherein the angle (α) is equal to about 80°.

4. A quick-action locking device according to 1 , wherein the predetermined radius (R) of the slider-forming annular support member amounts to 0.2–9, of the distance (a) between the contact point and the pivot axis ( 9 ).

5. A quick-action locking device according to claim 4 , wherein the predetermined radius (R) amounts to about 0.4 of the distance (a) between the contact point and the pivot axis ( 9 ).

6. A quick-action locking device according to claim 1 , wherein in the exchange position of the locking lever ( 6 ), the passing line forms with the longitudinal axis of the locking spindle ( 4 ) an end angle (β) that amounts from about 5° to about 30°.

7. A quick-action locking device according to claim 6 , wherein the end angle (β) amounts to about 10°.

8. An electrical power tool, comprising a housing ( 1 ); a hollow motor-driven spindle ( 2 ) located in the housing ( 1 ); a working tool ( 3 ); and a quick-action locking device for securing the working tool ( 3 ) to the spindle ( 2 ), the quick-action locking device comprising a locking spindle ( 4 ) axially displaceable in the hollow spindle ( 2 ) of the electrical power tool; a resilient member ( 5 ) for axially restraining the locking spindle ( 4 ); a locking flange ( 7 ) cooperating with the locking spindle ( 4 ) for securing the working tool ( 3 ) to the spindle ( 2 ) for joint rotation therewith; and a locking lever ( 6 ) provided at an end of the locking spindle ( 4 ) remote from the working tool ( 3 ) and pivotable about a pivot axis ( 9 ) between a locking position, in which the working tool ( 3 ) is secured to the spindle ( 2 ), and an exchange position in which the working tool ( 3 ) can be replaced, the locking lever ( 6 ) having a slider ( 8 ) for applying a force to the locking spindle ( 4 ) for displacing the locking spindle ( 4 ) against a biasing force of the resilient member ( 5 ) upon a pivotal movement of the locking lever ( 6 ) from the locking position to the exchange position, the slider ( 8 ) having a contact region engageable with a contact surface ( 11 ) provided at the end of the locking spindle ( 4 ) remote from the working tool ( 3 ),

wherein the contact surface ( 11 ) of the locking spindle ( 4 ) has a length (K) substantially equal to a distance (a) between a point of contact of the contact region of the slider ( 8 ) with the contact surface ( 11 ) of the spindle ( 4 ) in the locking position of the lever ( 6 ) and the pivot axis ( 9 ) of the locking lever ( 6 ), multiplied by sin (α) of angle (α) formed by a line passing through the contact point and the pivot axis ( 9 ) of the locking lever ( 6 ), with a longitudinal axis of the spindle ( 4 ); and

wherein, the slider ( 8 ) is formed as an annular support member having a predetermined radius and an axis of which extends parallel to and spaced from the pivot axis.