Preventing collision of moving parts - using transmitter and receiver for alternating electromagnetic fields to provide contact-free end switches

摘要

To prevent e.g. mobile bridge cranes which run at different levels from colliding, electromagnetic transmitters and receivers are used. When the two mobile elements approach each other, a spherical, alternating magnetic field is emitted from the transmitter. The receiver is such that it responds to spherical shaped magnetic fields. When the limit of the safe distance between the two mobile structures is reached, the receiver produces a command signal which stops the two driving motors. To avoid the possibility of coinciding sensitivity lobe characteristics both transmitter and receiver can be provided with two coils with their longitudinal axes positioned at right angles to each other.