Crushable body for position adjustment

A piston assembly for engaging two selectively engageable parts comprising:

• a housing defining a piston cylinder;
• a piston;
• and
• an adjuster assembly comprising:
• a piston stroke limiter configured to limit the length of a return stroke of the piston from an extended stroke position and a retracted stroke position, the piston stroke limiter comprising a spring and a spring guide;
• and
• a crushable body, acting between the piston and the piston stroke limiter, the crushable body being arranged to reduce in axial length when a length of an extension stroke exceeds a length of a retraction stroke to maintain the length of the return stroke;
• wherein the crushable body comprises an inner crushable thin-walled tube surrounding at least a portion of the piston and an outer crushable thin-walled tube mounted around and radially outwards of the inner crushable tube, an end of the outer crushable tube connected to an end of the inner crushable tube, the thin-walled tubes configured to form a crushed body of reduced axial length compared to the axial length of the thin-walled tube when a predetermined force is applied to the thin-walled tube;
• and
• wherein each of the inner crushable tube and the outer crushable tube has a corrugated crushable body portion defined between two end portions, wherein the corrugated crushable body portion has a regular corrugated form along its axial length, and wherein the two end portions are formed as flat, non-corrugated sections.