Wheel assembly with a wheel lock structure

A wheel assembly, comprising:

• a base frame comprising a chamber and a stem downwardly suspending from a top side of said chamber;
• a mounting frame located atop said base frame, a wheel pivotally mounted in said base frame and partially protruding from a bottom open side of said chamber;
• and
• a wheel lock structure mounted in said chamber operable to lock and unlock said wheel;
• wherein said wheel lock structure comprises:
• a holder frame comprising two rail blocks and a retaining channel defined between said rail blocks;
• a lift frame arranged in said holder frame, said lift frame comprising an axle hole;
• a crank arm, said crank arm comprising an axle located on one end thereof and coupled to the axle hole of said lift frame and a locating pin located on an opposite end thereof;
• a control knob mounted in said lift frame, said control knob comprising two lock pins selectively engaging respective lock holes on said wheel to lock said wheel to said base frame and an axle hole selectively coupled to the stem of said base
• a compression spring supported between the axle of said crank arm and a bottom wall of said holder frame to impart an upward pressure to said lift frame and said control knob in supporting said crank arm in a locking position where the locating pin of said crank arm is disengaged from the retaining channel of said holder frame and the lock pins of said control knob are respectively engaged into the respective lock holes of said wheel;
• said control knob is operable to lower said lift frame and said crank arm, moving the locating pin of said crank arm into the retaining channel of said holder frame and disengaging the lock pins of said control knob from the respective lock holes of said wheel for allowing free rotation of said wheel relative to said base frame.