Patent ID: 7592769
Filing Date: 2009-09-22
Classification: F16H,H02K,Y10T

Abstract:
1. An electric cylinder comprising: a first thread nut and a second thread nut, the first thread nut being a ball thread nut in which a thread groove in an arc shape in section is formed, and second thread nut being a non-ball thread nut which is rotatable in synchronization with the ball thread nut and in which a thread groove in a rectangular or trapezoidal shape in section is formed; and a thread rod inserted through the first and second thread nut, wherein in the thread rod is a double-start thread in which the two kinds of thread grooves are formed at the same pitch, the thread grooves including a thread groove in an arc shape in section meshed with the ball thread nut through balls and a thread groove in a rectangular or trapezoidal shape in section meshed with the non-ball thread nut, and the electric cylinder is configured such that, wherein a width of the thread ridge of the non-ball thread nut is set smaller than a width of the thread groove for the non-ball thread nut of each thread rod so that a state is controllable and exchangeable between a state that the thread ridge of the non-ball thread nut is separated from the thread ridge of each thread rod and a state that they are in contact with each other.