| 摘要 |
This invention concerns a self-tightening friction drive device for the conversion of a rotary motion into an axial motion. The device comprises two or more ball bearing jaws retained in angularly spaced position around a shaft, each of the jaws having at least one recess for receiving and supporting a respective ball bearing or roller bearing of larger internal diameter than the external diameter of the shaft extending through the bearings and engaging with the inner rings thereof an inclined angle. Each of the recesses presents in a section perpendicular to the axis of the respective bearing a curve whose radii of curvature are greater than the outer radius of the bearing. In consequence of the inclined position of the bearings relative to the shaft, the bearings will be wedged between the shaft and the bottom of the recesses in response to an axial load on the shaft and will exert an increased pressure against the shaft in response to an increased axial load on the shaft, the pressure being greater when the effective wedge angle is small. The invention further comprises control means adapted to pivot a jaw about a line parallel to the shaft and not merging with the axis of curvature of the supporting recesses, whereby the wedge angle can be controlled in addition to the effect of the actual shape of the recesses. |
