US Patent 7533474 Caliper gauge

A caliper gauge (1) includes a feeding mechanism (12) that moves a slider (11) along a main scale (10), in which the feeding mechanism (12) includes: an outer roller (121); an inner roller (122) provided in a manner rotatable around a rotary axis of the outer roller (121) to be in contact with the main scale (10); and a constant-pressure unit (123) that transmits the rotation of the outer roller (121) to the inner roller (122) and allows free rotation of the outer roller (121) relative to the inner roller (122) when more than a predetermined load is applied on the inner roller (122), the constant-pressure unit (123) including: saw-toothed projections provided on an inner circumference of the outer roller (121); and a plate spring fixed on an outer circumference of the inner roller (122) at a midsection thereof and contacted with the saw-toothed projections of the outer roller (121) on both ends thereof.