This invention relates to a power transmission device having a combined arrangement of balls and a screw for converting rotary to linear motion.
A variety of devices of the class have been known as circulatory fixed or other types. Any of the known devices operates to transmit power at a substantially equal reduction ratio in both directions counter to and toward the directions which a load is exerted (hereinafter called "counter-directional and non-counter-directional operation", respectively), so that a fairly great part of the work is rendered ineffective. The disadvantage of a loss of work is obvious particularly when such a transmission device is utilized to transmit power from a source for actuating movable elements in a reclining lounge, a jack or any other like appliances where the movable elements have to be actuated under a different load.