Automatic alarm system for detecting obstacles behind a backing vehicle

An automatic alarm system for detecting obstacles behind a backing vehicle, comprising:

• a casing having a generally cylindrical form and comprising:
• an upper section having a first opening at the front, the upper and lower edges of said first opening including semi-circular upper and lower guide channels, a pair of mounting flanges being provided for installing the casing upon the rear of the vehicle such that said first opening faces rearwardly,
• a lower section carrying a motor and a microswitch, the motor including an output shaft projecting upwardly along a central axis line of said casing,
• a reduction gear assembly mounted above said motor,
• a revolving disc being located under said upper section of said casing and above said reduction gear assembly, said disc having its center fixed on an output shaft of said reduction gear assembly and having two electrical terminals provided thereon, said disc comprising:
• a vertical plate defining a funnel-shaped second opening,
• a supersonic transmitter and receiver mounted on said vertical plate within said second opening, said transmitter and receiver being simultaneously alignable with said first opening so that signals emitted from said transmitter deflect-off obstacles and are sensed by said receiver,
• a dust cover extending from opposite sides of the funnel-shaped second opening, an upper edge of said cover being slidably inserted into said upper guide channel, and a lower edge thereof being slidably inserted into said lower guide channel, and
• two electrical contacts projecting from a bottom surface of said disc and electrically coupled to said transmitter and receiver,
• a printed circuit plate fixed within said casing between said revolving disc and said reduction gear assembly, and containing a supersonic transmitting and receiving circuit, said printed circuit plate including two arc-shaped conductors contactible with said contacts on said disc to connect said circuit with said transmitter and receiver, and
• an alarm means connected to said circuit such that said transmitter transmits supersonic waves when said vehicle is backing, which waves deflect-off adjacent obstacles and are received by said supersonic receiver to activate said alarm means.