A housing includes an accommodation space for a prime mover and a speed reducer. A rotational translation unit includes a rotation portion that rotates relative to the housing upon receiving torque outputted from the speed reducer, and a translation portion that moves relative to the housing in an axial direction according to rotation of the rotation portion. The accommodation space is between the rotation portion and the housing. A clutch in a clutch space allows or interrupts transmission of torque between a first transmission portion and a second transmission portion. The rotation portion is between the clutch space and the accommodation space. A sealing member has an annular shape in contact with the rotation portion, and maintains an air-tight or liquid-tight state between the accommodation space and the clutch space.

A micro-engine including a rotation structure, the rotation structure including a head portion, a rear portion, and a deformable portion connecting both portions. The deformable portion is deformable in elongation or compression along a main axis and includes a spring element displaying a free end. The free end of the spring element includes at least an abutment member. The deformable portion further includes a wheel-platform which displays a first and a second face, being configured to cooperate with the free end of the spring element in order to transform a back-and-forth movement of the at least one spring element into a rotational movement of the wheel-platform.

A micro-engine including a rotation structure, the rotation structure including a head portion, a rear portion, and a deformable portion connecting both portions. The deformable portion is deformable in elongation or compression along a main axis and includes a spring element displaying a free end. The free end of the spring element includes at least an abutment member. The deformable portion further includes a wheel-platform which displays a first and a second face, being configured to cooperate with the free end of the spring element in order to transform a back-and-forth movement of the at least one spring element into a rotational movement of the wheel-platform.

A power transmission apparatus includes a shift drum, a clutch, a clutch lifter, and a transmission body. The shift drum makes a dowel be extracted/inserted between a shifter and a shift gear. The clutch has first friction plates and second friction plates. The first friction plates rotate around a main shaft by receiving power from a crankshaft. The second friction plates are disposed alternately with the first friction plates and are relatively non-rotatably supported by the main shaft. The clutch lifter is displaced between a connection position at which power is transmitted by the clutch and a disconnection position at which the transmission of the power is disconnected. The transmission body transmits a driving force to the shift drum while the clutch lifter moves from the connection position to the disconnection position, in accordance with rotation of a shift spindle that rotates in accordance with a driving force.

A prime mover is provided in a housing, and can operate by energization and output a torque. A speed reducer can decelerate and output the torque of the prime mover. A rotational translation unit including a rotation portion that rotates relative to the housing when the torque output from the speed reducer is input, and a translation portion that moves relative to the housing in an axial direction when the rotation portion rotates relative to the housing and can change a state of a clutch to an engaged state or a non-engaged state. The speed reducer includes an output unit that outputs the decelerated torque of the prime mover to the rotation portion. The rotation portion is formed of a material different from that of the output unit separately, and is provided to be rotatable integrally with the output unit.

Provided is a linear movable rotary union including a driving shaft comprising a plurality of fluid supply paths; a hollow middle housing surrounding an outside of the driving shaft and comprising a plurality of first through holes in a sidewall; a plurality of first sealing members provided between the middle housing and the driving shaft to prevent leakage of a fluid; a hollow outer housing surrounding an outside of the middle housing and comprising a plurality of second through holes in a sidewall; and a plurality of second sealing members provided between the middle housing and the outer housing to prevent leakage of the fluid, and wherein the driving shaft is installed to be capable of rotational motion in the middle housing, and the middle housing is installed to be capable of reciprocating motion in an axial direction in the outer housing.

Provided is a linear movable rotary union including a driving shaft comprising a plurality of fluid supply paths; a hollow middle housing surrounding an outside of the driving shaft and comprising a plurality of first through holes in a sidewall; a plurality of first sealing members provided between the middle housing and the driving shaft to prevent leakage of a fluid; a hollow outer housing surrounding an outside of the middle housing and comprising a plurality of second through holes in a sidewall; and a plurality of second sealing members provided between the middle housing and the outer housing to prevent leakage of the fluid, and wherein the driving shaft is installed to be capable of rotational motion in the middle housing, and the middle housing is installed to be capable of reciprocating motion in an axial direction in the outer housing.

A linear drive has at least one rack which is arranged along a longitudinal axis and has a plurality of teeth, a drive shaft arranged in a transverse axis transversely to the longitudinal axis, and at least two propulsion elements, each having at least one propulsion tooth. The at least two propulsion elements are linearly movable in a stroke axis which is oriented transversely to the longitudinal axis and transversely to the drive shaft. The at least two propulsion elements are drivingly coupled to the drive shaft in such a manner that the at least two propulsion elements perform at least one cyclical stroke movement in the course of one rotation of the drive shaft and enter and exit the at least one rack to generate a propulsion in the longitudinal axis. The at least two propulsion elements enter and exit the at least one rack with a phase shift.

A linear drive has at least one rack which is arranged along a longitudinal axis and has a plurality of teeth, a drive shaft arranged in a transverse axis transversely to the longitudinal axis, and at least two propulsion elements, each having at least one propulsion tooth. The at least two propulsion elements are linearly movable in a stroke axis which is oriented transversely to the longitudinal axis and transversely to the drive shaft. The at least two propulsion elements are drivingly coupled to the drive shaft in such a manner that the at least two propulsion elements perform at least one cyclical stroke movement in the course of one rotation of the drive shaft and enter and exit the at least one rack to generate a propulsion in the longitudinal axis. The at least two propulsion elements enter and exit the at least one rack with a phase shift.

An actuator assembly is provided for converting rotation into linear displacement including a linear fluid dispensing tube for linear displacement. Hemispherical lugs are monolithically formed on the linear member. A primary gear includes a central bore having helix grooves formed into a surface of the central bore. The helix grooves receive the hemispherical lugs so that each helix groove mates with a respective hemispherical lug to reduce friction, so that hemispherical lugs slide smoothly within the respective helix grooves. Linear projections are formed on the exterior surface of the dispensing tube and extend longitudinally along the dispensing tube. A projecting portion has an aperture for receiving and guiding the dispensing tube through the linear displacement. Mating grooves are formed on an interior of the projecting portion for receiving and guiding the linear projections, thereby preventing the dispensing tube from rotating during travel.