US Patent 7121121 Locking device for trailer hitches and method therefor

A method and apparatus to secure the coupler section of a trailer provides a locking device that includes a lock housing having a hitch ball element to engage the recess in the coupler, a shackle member lockable to the housing and having a bridge section that spans the hitch ball element, and a latch assembly to latch and unlatch the shackle member. The shackle member is shown to be U-shaped with legs that extend through and secure to the lock housing. The latch assembly provides a ratchet-type engagement to allow adjustable locking. A rotatable lock mechanism drives a cam based latch mechanism between a latch state and an unlatch state.