Surface form measurement
First Claim
1. A method of determining information relating to the form of a surface of an object such as a workpiece, which method comprises sensing the surface using sensing means displaceable relative to a reference datum so as to follow the surface, effecting relative rotation about a rotation axis between the surface and the sensing means and using measurements made by the sensing means as the sensing means follows the surface during the relative rotation to determine information relating to the form of the surface, which method further comprises causing the sensing means to make a measurement at each of at least two positions equiangularly spaced apart around the axis of rotation so that the direction relative to the reference datum from which the sensing means senses the surface differs from each of the at least two positions and combining the measurements to compensate for error or deviation in the reference datum.
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Accused Products
Abstract
A nominally cylindrical surface of a workpiece is sensed by a stylus displaceable radially of an axis of rotation of the surface relative to a support column defining a reference datum so that the stylus follows the cylindrical surface at a given height along the surface. Relative rotation of the workpiece and the stylus about the axis of rotation of the surface is effected and the displacement of the stylus used to determine information relating to the radial form of the surface at that height. These measurements are represented at different heights along the surface so as to determine its cylindrical form. The displacement of the stylus from a given position on the surface at each height before and after rotation of the stylus and workpiece through 180° are measured and the resulting measurements used to compensate for any error or deviation in the reference datum.
67 Citations
54 Claims
- 1. A method of determining information relating to the form of a surface of an object such as a workpiece, which method comprises sensing the surface using sensing means displaceable relative to a reference datum so as to follow the surface, effecting relative rotation about a rotation axis between the surface and the sensing means and using measurements made by the sensing means as the sensing means follows the surface during the relative rotation to determine information relating to the form of the surface, which method further comprises causing the sensing means to make a measurement at each of at least two positions equiangularly spaced apart around the axis of rotation so that the direction relative to the reference datum from which the sensing means senses the surface differs from each of the at least two positions and combining the measurements to compensate for error or deviation in the reference datum.
- 2. A method of determining information relating to the form of a surface of an object such as a workpiece, which method comprises sensing the surface using sensing means displaceable relative to a reference datum so as to follow the surface, effecting relative rotation about a rotation axis between the surface and the sensing means and using measurements made by the sensing means as the sensing means follows the surface during the relative rotation to determine information relating to the form of the surface which method further comprises causing the sensing means to make a measurement of the displacement of a location on the surface from the reference datum when that location is at each of at least two positions equiangularly spaced apart around the axis of rotation and combining the measurements to compensate for error or deviation in the reference datum.
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6. A method of determining the form of a surface which is nominally symmetric about an axis, which method comprises sensing the surface using sensing means displaceable relative to a reference datum so as to follow the surface, effecting relative rotation of the surface and the sensing means and using the sensing means to make measurements at a number of different measurement distances or heights along the said axis of the surface to determine the form of the surface, which further comprises, for each measurement distance along the said axis, using the sensing means to obtain a first measurement of the displacement from the reference datum of a location on the surface, effecting relative rotation through 810°
- between the surface and the sensing means and then using the sensing means to obtain a second measurement of the displacement from the reference datum of the same location on the surface and using the mean of the first and second measurements to provide data representing that location.
- View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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17. Apparatus for determining information relating to the form of a surface of an object such as a workpiece, comprising:
- sensing means displaceable relative to a reference datum so as to follow the surface;
means for effecting relative rotation between the surface and the sensing means;
means for determining from measurements made by the sensing means as the sensing means follows the surface during the relative rotation information relating to the form of the surface; and
processing means for combining measurements made by the sensing means at each of at least two positions equiangularly spaced apart around the axis of rotation so that the direction relative to the reference datum from which the sensing means senses that location differs for each of the at least two positions to compensate for error or deviation in the reference datum. - View Dependent Claims (20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 40, 41, 43, 50, 51, 52)
- sensing means displaceable relative to a reference datum so as to follow the surface;
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18. Apparatus for determining information relating to the form of a surface of an object such as a workpiece, comprising:
- sensing means displaceable relative to a reference datum so as to follow the surface;
means for effecting relative rotation between the surface and the sensing means;
means for determining from measurements made by the sensing means as the sensing means follows the surface during the relative rotation information relating to the form of the surface; and
processing means for combining measurements made by the sensing means of the displacement of a location on the surface from the reference datum when that location is at each of at least two positions equiangularly spaced apart around the axis of rotation to compensate for error or deviation in the reference datum. - View Dependent Claims (19)
- sensing means displaceable relative to a reference datum so as to follow the surface;
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23. Apparatus for determining the form of a surface which is nominally symmetric about an axis, comprising:
- sensing means displaceable relative to a reference datum so as to follow the surface;
means for effecting relative rotation of the surface and the sensing means;
means for using the sensing means to make measurements at a number of different measurement distances or heights along the axis of the surface to determining the form of the surface;
control means for, for each measurement distance along the axis of the surface, using the sensing means to obtain a first measurement of the displacement from the reference datum of a location on the surface, causing relative rotation through 180°
between the surface and the sensing means then using the sensing means to obtain a second measurement of the displacement from the reference datum of the same location on the surface; and
processing means for determining the mean of the first and second measurements to provide data representing that location. - View Dependent Claims (42, 44, 45, 46, 47, 48, 49)
- sensing means displaceable relative to a reference datum so as to follow the surface;
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53. Apparatus for determining information relating to the form of a surface of an object such as a workpiece, the apparatus comprising:
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a body;
an arm pivotably mounted to the body;
a sensor carried by the arm;
means for effecting relative rotation between the sensor and the surface to cause the arm to pivot as the sensor follows the surface;
a transducer or providing a signal related to pivotable movement of the arm;
a drum rotatably mounted to the body;
a support eccentrically mounted on the drum;
a motor for rotating the drum; and
a biassing spring coupled between the support and the arm, whereby rotation of the drum by the motor adjusts the biassing of the arm by the biasing spring.
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54. Apparatus for determining the form of the surface which is nominally symmetric about an axis, comprising:
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a body;
an arm pivotably mounted to the body;
a sensor carried by the arm;
means for effecting relative rotation between the sensor and the surface to cause the arm to pivot as the sensor follows the surface;
a transducer for providing a signal related to pivotable movement of the arm;
means for determining from the signal provided by the transducer information relating the form of the surface;
a drum rotatably mounted to the body;
a support eccentrically mounted on the drum;
a motor for rotating the drum;
a biassing spring coupled between the support and the arm, whereby rotation of the drum changes the biassing on the arm from a first biassing condition to a second biassing condition; and
processing means for combining measurements made with the arm in the first biassing condition and the arm in the second biassing condition.
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Specification