Patent ID: 8529183

Claim:
A vehicle restraint system for preventing forward movement of a vehicle away from a loading dock, comprising: a. a base; b. an arm rotatably mounted to the base for rotating between a lowered position out of contact with the vehicle, an upright position wherein the arm may contact the vehicle to restrain the vehicle in a selected location relative to the loading dock suitable for loading or unloading and a range of partially elevated positions intermediate between the lowered and elevated positions wherein the arm contacts the vehicle when not in the selected position; c. an arm rotator for rotating the arm between the lowered and upright positions; d. a position sensor to detect the angular position of the arm throughout the range of motion of said arm, and within a continuous arcuate range for determining the position of the vehicle relative to the dock upon contact with said arm; e. a lock for locking the arm in an upright position wherein the vehicle may be blocked by said arm; f. a lock actuator for actuating the lock; and g. a controller responsive to the position sensor for: a) determining rotational movement of the arm and the rotational position of the arm within said continuous arcuate range, b) determining if rotation of the arm is prevented by contact between the arm and the vehicle, and c) determining from the rotational position of the arm when contacting the vehicle whether the vehicle is: i) located ahead of the selected location, ii) located behind the selected location or iii) located at the selected location to permit locking the arm in the upright position only when the vehicle is located at the selected location.