| 摘要 |
Two generally flat, circular plates, one having an attached threaded male cylindrical shaped extension and the other an attached mating threaded female cylindrical shaped extension are threaded together through the ring of a trailer hitch tongue until the plates are in contact with the ring and held locked in threaded engagement by a latch to prevent the unauthorized use of the trailer. The latch is spring loaded and is extended through an opening in the side of the male cylinder to engage any one of a number of internal grooves coaxial with the cylinder, cut in the female cylinder, to provide the locking function. A single lobe cam contained within the male cylinder is mounted on the end of a conventional lock cylinder which, in turn, is rotated by a matching key. Rotated to a first position by the key, the cam will permit the spring to urge the latch through the side opening in the male cylinder to engage the grooves in the female cylinder and provide the locking action and in a second position the cam will withdraw the latch into the male cylinder to permit either threading the two extensions together prior to locking, or to permit the removal of the lock after use.
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