Patent ID: 8839935

Claim:
A transmission device adapted to be coupled to a drive shaft that is pivotable about a pivot axis, said transmission device comprising: a mounting frame including an abutting member; a driving sleeve adapted to be sleeved on the drive shaft such that said driving sleeve co-rotates with the drive shaft, said driving sleeve having an annular outer surface formed with at least one spiral first guiding groove that has opposite first and second ends; a transmission wheel formed with an axial hole permitting extension of said driving sleeve thereinto such that said transmission wheel is sleeved rotatably on said driving sleeve, and at least one radially extending through hole in spatial communication with said axial hole and corresponding to said first guiding groove in said driving sleeve, said transmission wheel having a side surface formed with a curved second guiding groove that has opposite first and second ends, said second guiding groove having a depth increasing gradually toward said second end thereof; a connecting unit including at least one connecting post extending through said through hole in said transmission wheel and into said first guiding groove in said driving sleeve, and movable in said first guiding groove in said driving sleeve such that said transmission wheel is moved toward said abutting member of said mounting frame in a longitudinal direction parallel to the pivot axis by a first distance when said connecting post is guided by said first guiding groove in said driving sleeve from said second end of said first guiding groove to said first end of said first guiding groove in response to rotation of the driving sleeve driven by the drive shaft; a position-limiting member disposed movably on said side surface of said transmission wheel, formed with at least one ball-receiving hole corresponding to said second guiding groove in said side surface of said transmission wheel, and rotatable relative to said transmission wheel about the pivot axis between a first position, where said ball-receiving hole is disposed adjacent to said second end of said second guiding groove in said side surface of said transmission wheel, and a second position, where said ball-receiving hole is disposed adjacent to said first end of said second guiding groove in said side surface of said transmission wheel; and at least one ball disposed in said ball-receiving hole in said position-limiting member, and movable in said second guiding groove in said side surface of said transmission wheel such that said ball moves toward said abutting member of said mounting frame in the longitudinal direction by a second distance when said ball moves from said second end of said second guiding groove in said side surface of said transmission wheel to said first end of said second guiding groove in said side surface of said transmission wheel in response to rotation of said position-limiting member relative to said transmission wheel from the first position to the second position.