Mechanism for transforming linear movement of one member into arcuate or angular movement of another member or vice versa with particular reference to screw and nut typesteering gears

摘要

580,096. Screw-and-nut gearing. DOUGLAS, J. G. Feb. 7, 1944, No. 2184. [Class 80 (i)] In screw-and-nut mechanism the axially translative movement of the nut is applied to a rocker arm by inter-engaging means which prevent rotation of the nut to any substantial degree the said interengaging means having a substantially straight line path during movement of the nut and arcuate movement of the rocker arm. As applied to a steering gear, a nut a mounted on the screw-threaded end b of the steering column d slides in a bore e of a casing c and, at one side, has a recess l engaged by a partly spherical peg k mounted eccentrically on the inner face of a toothed sector j carried by a spindle i rotatably mounted in the rocker arm h on rocker shaft g. The sector j meshes with a toothed gear m secured to the inner face of the casing c with its pitch circle concentric with the axis of the shaft g. In the central position of the gear, the axes of the peg k, spindle i and shaft g all lie on a straight line at right angles to the axis of the nut a. When the column d is rotated, the nut moves axially but is prevented from rotating by the peg k. The gear j rolls upon the gear m causing the spindle i to rotate in an epicyclic manner and, with appropriate dimensions, the axis of the peg k and of the recess l will follow a substantially straight line path parallel to the axis of the nut. The leverage distance from the axis of the peg to that of the shaft g remains substantially constant. The position of the rocker arm h becomes advanced ahead of the peg k and therefore a smaller travel of the nut is required for a given angular movement of the rocker arm. In a modification, the spindle i is of conical form and has a control gear fast with its outer end meshing with a fixed toothed sector secured to the inner face of the cover .plate p. Axial adjustment of shaft g is effected by shims n between the plate p and the casing, or by a pressure-screw. Balls may be circulated in the grooves of screw and nut as described in Specification 490,938.