Piston tube assembly for a spring brake actuator, and spring brake actuator

A spring brake actuator (1) for a commercial vehicle, the spring brake actuator comprising:

• a cylinder housing (2) having a housing base (5),
• a spring brake piston (9) disposed inside the cylinder housing (2),
• a compression spring (11) disposed inside the cylinder housing (2) between the housing base (5) and the spring brake piston (9), wherein the compression spring is effective to push the spring brake piston (9) away from the housing base (5), the spring brake piston (9) configured to transmit a brake force exerted by the compression spring (12), and
• a piston tube assembly (17) comprising:
• a first tubular body (35) having a contoured inside surface profile (55) for non-rotationally guiding a running nut (21) of a mechanical release mechanism (19, 21), and
• an internal breather valve (41) mounted to the piston tube assembly (17) for allowing fluid transport into and out of the piston tube assembly (17) and any volume in fluid communication therewith,
• a second tubular body (37) that is made of a different material than the first tubular body (35),
• wherein the second tubular body encloses the first tubular body (35) and mechanically supports the first tubular body (35),
• wherein the internal breather valve (41) is mounted to the first tubular body (35);
• wherein the second tubular body is longer than the contoured inner surface profile of the first tubular body;
• wherein the first tubular body (35) includes a head section (39) and a recess (51) disposed in the head section (39) for accommodating the internal breather valve (41).

A piston tube assembly (17) for a spring brake actuator (1), the piston tube assembly (17) comprising:

• a first tubular body (35) having a contoured inside surface profile (55) for non-rotationally guiding a running nut (21) of a mechanical release mechanism (19, 21), and
• an internal breather valve (41) mounted to the piston tube assembly (17) for allowing fluid transport into and out of the piston tube assembly (17) and any volume in fluid communication therewith,
• wherein the piston tube assembly (17) further comprises a second tubular body (37) that is made of a different material than the first tubular body (35),
• wherein the second tubular body encloses the first tubular body (35) and mechanically supports the first tubular body (35),
• wherein the internal breather valve (41) is mounted to the first tubular body (35);
• wherein the first tubular body defines at least one lateral ventilation hole in fluid communication with the internal breather valve;
• wherein an annular space is defined between the first tubular body and the second tubular body;
• wherein the annular space is in fluid communication with at least one lateral opening provided in the second tubular body, wherein fluid can pass through the at least one lateral opening, the annular space, and the at least one lateral ventilation hole from outside of the piston tube assembly.