HEAVY DUTY ELECTRONIC BRAKE STROKE INDICATOR

摘要

Electronic stroke indicators have sensor structures (34, 60, 80, 110) which are incorporated into a stone shield (28, 62, 82, 116) for a brake actuator (20). The incorporation of the sensor (34, 66, 119) stone shield (28, 62, 116) protects the sensor (34, 60, 119) and its associated wires (50, 69, 121) and contacts from damage by the other components in the brake actuator (20). In particular, the spring is typically maintained out of contact with any of the electric portions of the electronic stroke indicator, thus prolonging the life of the electronic stroke indicator. In further features of this invention, a magnetic sensor (34) may monitor the position of magnetic portions (36) on a piston rod (32). Alternatively, a pair of electric contact switches (96, 98) may be serially contacted by a structure on the piston rod (94) as the broke moves further out of stroke. The two electric contacts (96, 98) provide different signals to an operator in a vehicle cab such that signals of the level of out-of-stroke conditions are provided to the operator. In a further embodiment, a load cell (119) monitors the compression in a spring (112) in the brake housing (111) to provide an indication of an out-of-stroke condition.