Involute interpolation method

Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems

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Details

318570, 36447431, G05B 19415

Patent

active

049356810

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an involute interpolation method for machining operations in a numerical control apparatus, and more particularly to an involute interpolation method in which an involute curve depicted intermediately of two involute curves is subjected to interpolation.


BACKGROUND ART

In a curve interpolation in association with a numerical control apparatus, interpolation of an involute curve has particularly been needed for machining gears, vanes of pumps and the like, and it has been a general practice to interpolate the involute curve with a computer or an NC program producing system which is distinctly provided from the numerical control apparatus to analyze a curve data into straight line data, whereupon numerical control machinings are performed with the use of a tape.
The same applicant filed Japanese patent application No. 62-157303 in which it is proposed to readily interpolate an involute curve in a numerical control apparatus.
In practical machinings, however, an involute curve is sometimes necessary such that it starts with one involute curve and ends with another involute curve in which two involute curves, not a single involute curve, are involved. Such type of involute curve cannot be interpolated according to the proposal stated above.


SUMMARY OF THE INVENTION

An object of this invention is to provide an involute interpolation method in which such a combined involute curve can be interpolated.
In order to resolve the above-noted problem, the invention provides an involute interpolation method for use in machining operations by a numerical control apparatus, which comprises the steps of:
instructing a rotational direction of an involute curve, a center position of a base circle, and a radius (R) of the base circle;
further instructing a curve start point of a first involute curve resulting from the base circle and a curve start point of a second involute curve resulting from the base circle; and
wherein an interpolation is performed with respect to an involute curve having a start point on the first involute curve and an end point on the second involute curve.
A start angle of the involute curve is set at the start of the interpolation to a start angle of the first involute curve and at the end of the interpolation to a start angle of the second involute curve, wherein the interpolation is performed while proportionally dividing a distance between the first involute curve and the second involute curve.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an involute curve according to one embodient of the present invention; and
FIG. 2 is a block diagram showing a numerical control apparatus according to one embodiment of the present invention.


DESCRIPTION OF THE PREFERRED EMBODIMENT

One embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 illustrates an example of an involute curve according to the embodiment of the invention. In the figure, there is depicted a base circle C for the involute curve which has a center represented by a coordinate O (X.sub.0, Y.sub.0) and a radius R.
A first involute curve IC1 starts with a point P.sub.1 (X.sub.1, Y.sub.1) and an angle .theta.1 is formed by a line connecting the points P.sub.1 and O with respect to an X-axis.
A second involute curve IC2 starts with a point P.sub.2 (X.sub.2, Y.sub.2) and an angle .theta..sub.2 is formed by a line connecting the points P.sub.2 and O with respect to the X-axis.
An involute curve required as a result of interpolation is such that a point P.sub.s (X.sub.x, Y.sub.s) on the first involute curve IC1 is a start point for interpolation and a point P.sub.e (X.sub.e, Y.sub.e) on the second involute curve IC2 is an end point for interpolation, in which a moderate curve IC connectes between the start and end points as indicated by a dotted line.
Now, a tangential line is drawn from the point P.sub.s (X.sub.s, Y.sub.s) to the base circle C and the point of contact of this tangential line with the base circle is plotted

REFERENCES:
patent: 4736086 (1988-04-01), Obara
patent: 4791575 (1988-12-01), Watts, Jr. et al.

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