A ratchet wheel having a locking device, comprising:
- a housing having first and second, axially opposite end wall means and peripheral wall means defining a receiving space;
- a ratchet wheel received in said space and journalled with respect to said housing for angularly reversible rotation about a longitudinal axis thereof, said ratchet wheel having a circumferentially extending series of ratchet teeth;
- a longitudinally extending flange provided on one end of said ratchet wheel and protruding out of said space through opening means provided in one of said end wall means, said flange being provided outside said housing with surface means which are engageable with an externable rotatable object so as to couple said ratchet wheel to the external rotatable object for rotation therewith;
- a braking member accommodated in said housing, said braking member comprising a pivot portion, a shank projecting from said pivot portion and having a wedge angle formed at an outer end thereof, said pivot portion being journalled with respect to said housing for pivotal movement about an axis parallel to said longitudinal axis between a first position in which said wedge angle of said shank effectively meshes with said teeth of said ratchet wheel for preventing rotation of said ratchet wheel, and therefore, said external rotatable object in one angular direction about said longitudinal axis, and a second position in which said wedge angle is effectively withdrawn from meshing engagement with said teeth of said ratchet wheel for permitting rotation of said ratchet wheel, and therefore said external rotatable object, in said one angular direction;
- a first resilient biasing means effectively engaged between said housing and said braking member for tending to return said braking member to said first position from said second position;
- a rotor means received in said housing;
- and
- a locking means received in said housing and including a lock core which, in use, is effectively coupled by said rotor means with said braking member, and journalled for rotation between a locking position which corresponds to said first position of said braking member and an unlocking position which corresponds to said second position of said braking member;
- said rotor means including:
- a rotor arranged for connection with said lock core for rotation therewith, said rotor having an outer peripheral surface;
- means defining a blind hole in said rotor through said outer peripheral surface;
- a pin slidingly socketed in said blind hole for greater and lesser projection beyond said outer peripheral surface of said rotor;
- a second resilient biasing means received in said blind hole and effectively engaged between said rotor and said pin for tending to urge said pin towards greater projection beyond said outer peripheral surface of said rotor;
- said pin being arranged to engaged said shank of said braking member for pivoting said braking member from said first position to said second position against biasing force provided by said first resilient biasing means upon rotation of said lock core to said unlocking position, and for effectively disengaging from said shank of said braking member for allowing said biasing force provided by said first resilient biasing force to pivot said braking member from said second position to said first position.