04291557 is referenced by 25 patents and cites 6 patents.

An anti-theft device secured by sliding the device over a ball-connector type trailer hitch which automatically engages the hitch by means of a spring loaded bolt, to obstruct access by the ball and prevent unauthorized use of the trailer. The device is removed by retracting the bolt using only a conventional key. No tools or auxiliary parts are required to attach or remove this device.

Title
Trailer hitch lock
Application Number
6/144773
Publication Number
4291557
Application Date
April 28, 1980
Publication Date
September 29, 1981
Inventor
Dale A Johnson
6336 19th Ave. S.,, Richfield, 55423
MN, US
Marshall Bulle
918 Third St., Farmington, 55024
MN, US
Agent
Donald A Jacobson
IPC
B60D 1/12
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