A linear drive apparatus is provided. The linear drive apparatus may include an outer tube, a sealing end cap provided at the end of the outer tube, a screw provided in the outer tube, a drive nut provided on the screw in a threaded fit, an extension rod provided between the outer tube and the screw, a sealing assembly provided between the extension rod and the sealing end cap, and a waterproof and oil-proof ventilation stopper provided on the outer tube. One end of the screw may be connected to a drive mechanism. One end of the extension rod may be connected to the drive nut. The other end of the extension rod may pass through the sealing end cap.

An electric linear actuator has a housing, an electric motor, a speed reduction mechanism and a ball screw mechanism. The ball screw mechanism has a nut and screw shaft. A blind bore is formed on the housing. The blind bore contains an end of the screw shaft. An anti-rotation mechanism for the screw shaft has a sleeve and guide pin. The sleeve is press-formed from steel sheet and fit into the blind bore of the housing. The guide pin is mounted on the end of the screw shaft, via a through aperture formed in the screw shaft. The guide pin axially movably engages the sleeve.

An actuator includes M supports to support the rotary shaft, M being an integer equal to or more than 2; and M speed reducers. The Nth support out of the M supports is located at the opposite side of the moving body across the (N1)th support, N being an integer which is equal to or more than 2 and equal to or less than M. The first speed reducer is connected to the moving body and the first support, receives a movement of the moving body in the axial direction as an input and drives the first support with a reduced drive force that is reduced from the input, and the Nth speed reducer is connected to the (N1)th support and the Nth support, receives a movement of the (N1)th support in the axial direction as an input and drives the Nth support with a reduced drive force.