Digital tire caliper

Abstract

Tires can be accurately and quickly measured by using a tire caliper that outputs data in digital form. A measuring instrument determines the diameter of automotive tires, preferably automotive race tires, and displays the circumference or the diameter at the users option, The tool of this invention has a digital display including a relatively elongate caliper body formed with a measuring part adapted to make measuring engagement with the tire to be measured. A member freely slidable in a longitudinal direction of the caliper body and formed with a measuring part disposed opposite to the measuring part of the caliper. In one preferred embodiment, the measuring instrument is marked with a transparent linear scale fixedly disposed on the caliper body with its axis extending in the longitudinal direction of the caliper body and a transparent index scale is mounted on the slider with its calibrated face disposed opposite to the calibrated face of the linear scale and slightly spaced apart relationship. In this embodiment, a measuring circuit including a digital display element is mounted in the slider and is electronically connected to a light emitting element and a light receiving element mounted in the slider. The light emitting element and the light receiving element are disposed opposite to each other with the linear scale and the index scale interposed therein between. In the preferred embodiment, the measuring circuit converts the measured tire diameter into the tire circumference measurement, which is digitally displayed on the LCD. In one particularly preferred embodiment, the circuitry allows the measurements of the front, right rear, left front and left rear tires to be recorded for a later reading of those measurements.