Methods and apparatus for measuring transverse dimensions of workpieces
AssigneeNational Research Development Corporation
InventorRoger I. Grosvenor
Life of this patent
Estimating the term…
Abstract
In computer control of machine tools there is a need to measure the diameters of cylindrical workpieces automatically and preferably without touching the workpiece. For this purpose an inductive proximity sensor is mounted for circular or linear movement along a path adjacent to a cylindrical workpiece and in a plane normal to a radius of the workpiece. A discrete fast Fourier transform (FFT) is carried out on the output of the sensor as it moves along the path and the amplitude of the second ac component of the FFT is an indication of the workpiece diameter. By calibrating with workpieces of different diameters, the said amplitude can be used as a measure of workpiece diameter.
Claims29
A method of deriving a dimension of an object transverse to an axis of the object and at least partly defined by a surface of the object, the method comprising the steps of:
- moving a non-contacting distance-measuring sensor along a predetermined path while repeatedly measuring a distance between said surface and the sensor, said path being substantially within a predetermined plane orthogonal to a line which intersects said axis orthogonally and the path being, at least at times, at an angle to a line in said plane which is parallel to said axis,
- analyzing, using a predetermined analytical method, a relationship between distances measured and a position of the sensor in the path, and
- deriving an indication of said dimension from the analyzing and from a previous calibration relating analysis carried out by the predetermined analytical method to a known dimension normal to said plane for sensor movement along said path.
An apparatus for deriving a dimension of an object transverse to an axis of the object and at least partly defined by the surface of the object, comprising:
- means for mounting an object with an axis thereof transverse to a dimension to be measured in a predetermined position,
- a non-contacting sensor for measuring a distance between the sensor and a surface of the object which at least partly defines said dimension,
- means arranged to move the sensor along a predetermined path while repeatedly measuring the distance between said surface and the sensor, said path being substantially within a predetermined plane orthogonal to a line which intersects said axis orthogonally and said path being, at least at times at an angle to a line in said plane which is parallel to said axis, and
- means for analyzing, using a predetermined analytical method, a relationship between distances measured by the sensor and a position of the sensor in the path and for deriving an indication of said dimension from said analyzing.
Dependencies are inferred from the claim text.