Spring brake actuator for use in a commercial vehicle, release bolt, and use of such a bolt in said spring brake actuator

The invention relates to a spring brake actuator (1), in particular parking or emergency spring brake actuator, for use in a commercial vehicle, said actuator comprising a cylinder housing (3) having a cylinder housing base, a spring brake piston (11) located in said cylinder housing for applying a braking force, a compression spring (9) located between the cylinder housing base and the spring brake piston, said compression spring being effective to push the spring brake piston away from the base, a brake release bolt (19), preferably a half-release bolt, having a threaded portion (37), a running nut (21) engaging the threaded portion (37), said running nut being adapted to move the spring brake piston against the force of the compression spring, wherein the spring brake piston comprises a flange portion (23) adapted for abutting against the running nut, and a static nut (31) fixedly attached to the bolt, said static nut being effective to move the running nut along the threaded portion. In particular, the actuator comprises a protrusion (27) inside the cylinder housing extending away from the cylinder housing base, and a stopper (25) located on the release bolt at a position between the running nut and the static nut, said stopper being adapted to abut against the protrusion (27) at a predetermined stroke position of the spring brake piston (11).