Extending and retracting device for vehicle step

1. An extending and retracting device for a vehicle step comprising:

a mounting bracket adapted to be fixed to a body of a vehicle;

a step bracket formed with a substantially U-shaped groove therein defining a pair of side walls of said groove;

an arc sliding member fixed to said step bracket, made in the form of an arc sliding block, and defining a pair of ends of said arc sliding member fixed in respective said pair of side walls of said groove;

a driving arm defining a pair of ends thereof pivotally connected to respective said mounting bracket and said step bracket; and

a supporting arm defining an upper end portion thereof pivotally connected to said mounting bracket and a lower end portion of said supporting arm located in said groove of said step bracket and defining at least one arc slot of said lower end portion, wherein said arc sliding member is adapted to pass through and fit into said arc slot so as to be slidable in said arc slot such that said lower end portion of said supporting arm is slidably connected to said step bracket.

2. An extending and retracting device for a vehicle step as set forth in claim 1 , wherein said arc sliding member is made in the form of a plurality of columnar bodies arranged in an arc array, said step bracket is formed with a substantially U-shaped groove defining a pair of side walls thereof, said lower end portion of said supporting arm is located in said groove, and said arc sliding member defines a pair of ends fixed in respective said pair of side walls of said groove such that said arc sliding member passes through and is slidably fitted into said arc slot.

3. An extending and retracting device for a vehicle step as set forth in claim 1 , wherein said step bracket includes a body portion and an extension portion formed with a step groove for fixing the vehicle step to said step bracket, said arc sliding member is located in said arc slot substantially at or adjacent to a lower end of said arc slot when said device is in an extended position, and said arc sliding member is located in said arc slot substantially at or adjacent to an upper end of said arc slot when said device is in a retracted position.

4. An extending and retracting device for a vehicle step as set forth in claim 1 , wherein said arc slot defines a pair of ends thereof and a curvature radius at said pair of ends of said arc slot is smaller than that at an intermediate portion of said arc slot.

5. An extending and retracting device for a vehicle step as set forth in claim 1 , wherein said arc slot defines a pair of ends thereof, a substantially uniform curvature radius, and at least one buffering pad disposed at a respective one of said pair of ends of said arc slot in order to reduce impact of said arc sliding member on said arc slot.

6. An extending and retracting device for a vehicle step as set forth in claim 1 , wherein said arc slot defines a curvature center thereof and said arc slot and curvature center are located to the same side of an imaginary line connecting with each other a pair of pivot points defined by respective said pair of ends of said driving arm.

7. An extending and retracting device for a vehicle step as set forth in claim 1 , wherein said lower end portion of said supporting arm is made in the form of an arc structure and defines a curvature center substantially coinciding with a curvature center defined by said arc slot.

8. An extending and retracting device for a vehicle step as set forth in claim 7 , wherein said step bracket includes a body portion and an extension portion formed with a step groove therein for fixing the vehicle step to said step bracket, said body portion is made in the form of a columnar structure defining a substantial center of circle thereof and sized to be adapted to match said arc structure of said supporting arm, and said arc slot defines a curvature center thereof substantially coinciding with said center of circle of said columnar structure.