US Patent 7516512 Castor having efficiently locking function

A castor includes a main body, two rollers each rotatably mounted on the main body, a stop member movable in the main body between a first position where the stop member is located at a height higher than that of each of the two rollers and a second position where the stop member is located at a height lower than that of each of the two rollers, a slide slidably mounted in the main body to move the stop member, and a control member pivotally mounted on the main body to move the slide. Thus, when the stop member is movable downward to rest on the ground, the two rollers are suspended in the air, so that the castor is locked exactly without slipping or moving on the ground.