A piston rod seal unit. The piston rod seal unit includes a housing, a cylinder gland, and at least one floating rod seal assembly mounted in the cylinder gland, the floating rod seal assembly comprising at least one rod seal mounted onto the floating rod seal assembly.

A piston rod seal unit. The piston rod seal unit includes a housing, a cylinder gland, and at least one floating rod seal assembly mounted in the cylinder gland, the floating rod seal assembly comprising at least one rod seal mounted onto the floating rod seal assembly.

A sealing comprises a seal portion and a plate portion fixed to the seal portion. The seal portion can have an undulating configuration of at least one peak and at least one valley, and the plate portion can circumferentially surround the seal portion. The seal portion can be made of a first material and the plate portion can be made of a second material more rigid than the first material. The seal portion can have a radially inward facing contact surface that defines a central opening of the sealing.

A sealing comprises a seal portion and a plate portion fixed to the seal portion. The seal portion can have an undulating configuration of at least one peak and at least one valley, and the plate portion can circumferentially surround the seal portion. The seal portion can be made of a first material and the plate portion can be made of a second material more rigid than the first material. The seal portion can have a radially inward facing contact surface that defines a central opening of the sealing.

A disc brake including: a piston; a cylinder including a bore portion, which movably accommodates the piston, and a step portion formed on an opening end side of the bore portion; and a piston boot arranged between a tip side of the piston and a small diameter step portion of the cylinder. The piston boot includes: a large diameter annular fitting portion containing an annular metal member so as to be fitted to the small diameter step portion; a bellows portion, which extends from the large diameter fitting portion, is increased in its diameter from the large diameter fitting portion to an outer peripheral side, and is also deformed and extended from the large diameter fitting portion toward an inner peripheral side; and a small diameter fitting portion formed at an end portion of the bellows portion so as to fit to an outer periphery of the piston.

A disc brake including: a piston; a cylinder including a bore portion, which movably accommodates the piston, and a step portion formed on an opening end side of the bore portion; and a piston boot arranged between a tip side of the piston and a small diameter step portion of the cylinder. The piston boot includes: a large diameter annular fitting portion containing an annular metal member so as to be fitted to the small diameter step portion; a bellows portion, which extends from the large diameter fitting portion, is increased in its diameter from the large diameter fitting portion to an outer peripheral side, and is also deformed and extended from the large diameter fitting portion toward an inner peripheral side; and a small diameter fitting portion formed at an end portion of the bellows portion so as to fit to an outer periphery of the piston.

An impact on the tips of peaks of a metal bellows on contact is reduced, and deformation of the tips of the peaks even on contact is reduced to a minimum. In a free length state of a metal bellows 10 in an early stage of incorporation without extension and contraction, valleys each turn around in a U shape in cross section, peaks each turn around in an arc shape in cross section, the peaks are each provided in a position offset with respect to the center of a pitch between valleys adjacent to the peaks on both sides, and of bellies connected to the peaks on both sides, at least bellies located on the offset side are provided with a constriction protruding inward of the metal bellows.

An impact on the tips of peaks of a metal bellows on contact is reduced, and deformation of the tips of the peaks even on contact is reduced to a minimum. In a free length state of a metal bellows 10 in an early stage of incorporation without extension and contraction, valleys each turn around in a U shape in cross section, peaks each turn around in an arc shape in cross section, the peaks are each provided in a position offset with respect to the center of a pitch between valleys adjacent to the peaks on both sides, and of bellies connected to the peaks on both sides, at least bellies located on the offset side are provided with a constriction protruding inward of the metal bellows.

An external combustion engine including a burner element, a heater head, a piston cylinder containing a piston, a cooler and a crankcase. The crankcase includes a crankshaft, a piston rod connected to the piston, a drive mechanism for converting the linear motion of the piston rod to rotary motion of the crankshaft and a linear cross-head bearing that is connected rigidly to the piston rod at one end and to the drive mechanism at the other end. Also the external combustion engine includes a piston clearance seal and a piston rod seal unit that has floating rod seals. The piston includes a inner dome to reduce axial heat transfer via radiation and convection.

An external combustion engine including a burner element, a heater head, a piston cylinder containing a piston, a cooler and a crankcase. The crankcase includes a crankshaft, a piston rod connected to the piston, a drive mechanism for converting the linear motion of the piston rod to rotary motion of the crankshaft and a linear cross-head bearing that is connected rigidly to the piston rod at one end and to the drive mechanism at the other end. Also the external combustion engine includes a piston clearance seal and a piston rod seal unit that has floating rod seals. The piston includes a inner dome to reduce axial heat transfer via radiation and convection.