Q Will you please explain the difference between "spring brakes" and "lock actuators"? Also what are self-energizing brakes?
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AA spring brake is an actuator with two
sections, one operating as a normal unit and the other containing a diaphragm and heavy spring. For normal running air pressure is applied to the second diaphragm chamber to compress the spring and the main chamber used for braking, but for parking or in emergency the pressure holding oft the spring is discharged and the energy of the spring is applied to the actuator rod to apply the brakes.
In the case of a lock actuator there are normally two diaphragms (separated), one for main and one for secondary braking. and there is a locking mechanism incorporated which holds the actuator shaft in the "on" position when required.
Usually there is a combined secondary – and parking – valve and when the former position is engaged the secondary diaphragm is pressurized and when the latter, the locking system comes into use also.
Self-energizing brakes are not used on any commercial vehicle at present but the principle is that application Of the shoes to the drum (Or disc) has the effect of increasing the pressure.