A trailer hitch assembly including a tow-carrying upstanding ball and an adaptor removably mounted on the ball to increase the effective diameter of the ball. The socket of a coupler of a trailer is mounted over the adaptor.

An interchangeable trailer ball apparatus provides an elongated hollowed pin which is attached normally to the bumper or drawbar of a vehicle. The bumper provides an internal elongated longitudinal bore with a lateral bore intersecting the longitudinal bore at one end portion. Disposed within the lateral bore is a locking element which is moveably mounted between retracted and projected positions. Disposed slideably within the longitudinal bore of the bumper pin is an actuating rod which is moveably mounted between positions which alternatively allow the locking element to assume an inward retracted position and abut the locking element to move it into the projected position. A trailer ball having a closed end bore is removably attachable to the bumper pin when the locking element is in the retracted position and is secured to the bumper pin by the locking element when it assumes the projected position. The trailer ball can have an annular recess for receiving thereinto the locking element.

A hitch ball (20) with a mating first set of shells (25a and 25b) and optionally a second set of shells (27a and 27b) to increase the diameter of the ball to accommodate various sized hitch assemblies (11) are described. In a preferred form detents (25e and 25f) in the first set of shells are provided in a recess (23) in the ball. Detents (27c and 27d) are provided on the detents (25e and 25f) of the first set of shells. The invention provides safe and effective mounting of the sets of shells on the hitch ball and prevents the shells being used on a conventional hitch ball which might not be rated for the increased capacity provided by the larger ball size.

An improved trailer hitch assembly to be attached to a drawbar for towing a trailer, the assembly including an upright elongated hitch post threaded at the lower end by which it is attached to a drawbar, the upper end being of cylindrical external configuration and the post having a central passageway therein communicating with the bottom end, a grease fitting threadably received in an opening in the bottom end communicating with the passageway and the upper end of the passageway communicating with the external cylinder surface, and a ball having an opening therethrough rotatably received on the hitch post and a keeper ring secured to the upper end of the hitch post to retain the ball in position, grease being deposited from the grease fitting through the passageway to lubricate the cylindrical surface between the hitch post and the ball.

A ball-exchange trailer bitch system having a post for receiving a ball where the ball is removable from the post for exchangeability with different size balls. The system includes at least a double locking feature between the ball and post. The double lock consists of a side pin lock and a ball and cage lock. The system may also include a third lock which includes threads on the post and the ball.