Steering gear with varying transmission ratio

A gear coupling comprisng:

• a first tooth carrier linearly shiftable in a predetermined plane and provided with a first set of identically profiled involute teeth;
• and
• a second tooth carrier swingable about a pivotal axis transverse to said plane and provided with a second set of identically profiled involute teeth, each of said tooth carriers having a base line with a constant radius of curvature in said plane, at least one of said radii being of finite magnitude, said first and second sets of teeth meshing with each throughout a range of displacement between two limiting positions flanking a midposition in which the centers of curvature of the base lines of said first and second sets of teeth are offset from said pivotal axis on a line perpendicular to the direction of shift of said first tooth carrier, said first and second sets of teeth engaging each other with clearances which are substantially zero in said misposition but which progressively increase toward said limiting positions and with a transmission ratio varying substantially monotonically between said midposition and each of said limiting positions.