Patent ID: 6888451

Claim:
A method of monitoring the condition of a power spring of a pneumatic spring brake actuator of a vehicle braking system, said spring brake actuator including a housing having a power spring chamber and a service chamber, a power spring in said power spring chamber biased against a piston and said piston operatively engaging a push rod in said service chamber, a pneumatic port in said power spring chamber normally supplying pneumatic pressure to said power spring chamber and compressing said power spring, and a pneumatic port in said service chamber independently supplying pneumatic pressure to said service chamber upon actuation of said vehicle braking system, extending said push rod to actuate said braking system, said method comprising the following steps: (a) periodically supplying pneumatic pressure to said service chamber and determining a stroke of said push rod; (b) periodically releasing pneumatic pressure from said power spring chamber and determining a stroke of said push rod; and (c) periodically comparing said stroke of said push rod from steps (a) and (b) to determine said condition of said power spring.