Measuring and testing – Surface and cutting edge testing
Reexamination Certificate
2000-10-26
2002-12-10
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Surface and cutting edge testing
C073S105000
Reexamination Certificate
active
06490912
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a probe for sensing and measuring the shape, undulations, or roughness of a surface.
BACKGROUND OF THE INVENTION
Probes of the pertinent type are publically known. Depending on the design, they make it possible to sense and measure the shape, undulations, or roughness of a surface. In the following description, the term “characteristics” includes all three sensing and measuring options.
A probe for sensing the characteristics of a surface of a workpiece is known from DE 26 60 993 C2. This probe contains an electromechanical measuring transducer; the probe arm of the measuring transducer is provided with a probe tip and is prestressed in the sensing direction. The entire measuring probe is mounted on a feed unit that guides the probe tip of the measuring transducer over the surface to be examined. The measuring transducer transforms the movements of the probe tip in the direction of the tip (Z-direction) into corresponding measurement data. Since the feed unit moves the measuring transducer at constant speed, the measurement data can be recorded, e.g., on a paper tape that also runs at a constant speed as a function of time. In this case, a linear dependence is always assumed; however, a constant feed movement is a prerequisite for such a linear dependence, so that there are strict requirements for maintaining the feed movement constant. This means that a feed unit which meets these strict requirements must be provided. In addition, such a feed unit requires special measures to maintain the electromechanical measuring transducer within its operation region, e.g., such as those described in DE 27 25 072 A1 and DE 41 32 724 A1, if the surface to be sensed is not flat due to the shape of the workpiece to be sensed or due to excessive undulations, i.e., if a change in the direction of the advance movement is necessary. However, the shape or undulations, of the surface are not reflected in the form of a measuring voltage by the measuring transducer; thus, the shape or undulations, of the surface are lost.
DE 35 43 906 A1 discloses a probe for sensing the features of a workpiece surface with a probe tip that is arranged on a probe arm that can be pivoted essentially in the direction of the tip about a pivot bearing, with the probe tip being arranged at a certain distance from the pivot bearing. This probe also contains a transducer for transforming the movements of the probe tip into corresponding measurement data.
DE 35 43 906 A1 also describes a probe for sensing the features of a workpiece surface and contains a base body, a means for realizing a uniform linear movement of the base body in the sensing direction, a probe arm that is arranged on the base body and that can be pivoted about a pivot bearing, a probe tip that is arranged on the probe arm at a distance from the pivot bearing, and a measuring transducer for generating a measurement signal as a function of the movements of the probe tip in the direction of the tip while sensing a surface.
DE 196 37 554 A1 discloses a device for sensing the characteristics of a surface of a workpiece which contains a movably held probe tip, transducers for transforming the movements of the probe tip into corresponding measuring values and additional transducers for transforming the movements of the measurement probe that carries the probe tip into corresponding measurement data. The additional transducers consist of acceleration transducers, some of which are realized in the form of rotary acceleration transducers, which transform the pertinent measurement data into acceleration data. These transducers are connected without rotational play to the measuring probe, where an integrator that performs a double integration of the acceleration data over time as used to form the longitudinal dimensions that correspond to the positions of the measuring probe. Acceleration transducers only serve for measuring the portion of the probe tip movement that the probe tip carries out due to the movement of the measuring probe that carries the probe tip, primarily for measuring and correcting a generally undesirable relative movement between the measuring probe and the object to be measured.
U.S. Pat. No. 4,422,322 discloses a device for sensing the features of a road surface. A measuring vehicle with its wheels that roll on the road surface to be sensed serves as the measuring element. A transducer serves for transforming the movements of the measuring vehicle perpendicular to the road surface into corresponding measurement data, where the transducer consists of an acceleration transducer that transforms the measurement data into acceleration data and is rigidly connected to the spring-suspended mass of the measuring vehicle. An integrator performs a double integration of the acceleration data with respect to time [sic; with respect to distance] in order to form longitudinal measurement data that correspond to the features of the sensed road surface. This known device is not suitable for sensing the surface of a workpiece.
U.S. Pat. No. 5,850,289 discloses a device for sensing an object in order to determine its shape and three-dimensional surface characteristic. In this case, the sensing device is freely moved relative to the object and the movement or position data of the sensing device is determined by means of an acceleration transducer. The sensing takes place in such a way that a visual pattern is projected onto the surface of the object and the changes in the pattern are visually examined, with a signal for correcting the movement of the sensing device being formed therefrom. This known device is not suitable for sensing the roughness of the surface of a workpiece.
OBJECTS AND SUMMARY OF THE INVENTION
The invention is based on the objective of developing a probe for sensing the features of a workpiece surface, i.e., the shape, undulations, or roughness, which makes it possible to sense and transform into corresponding measurement data arbitrary irregularities of the workpiece surface, i.e., its shape, undulations, or roughness.
The basic idea of the invention consists of measuring the accelerations or speeds caused by the excursions rather than measuring the excursions of a probe tip during the sensing of the surface, with the value of the excursion subsequently being determined from said accelerations or speeds by means of an integration with respect to time.
According to one embodiment of the invention, linear accelerations are evaluated for this purpose. According to the present invention, the first transducer is realized in the form of a first acceleration transducer that transforms the measurement data into acceleration data, where said acceleration transducer is movably held and prestressed in the direction of the tip (Z-direction) and rigidly connected to the probe tip. Consequently, this first acceleration transducer is able to measure a wide range of movements, i.e., substantial differences in height that correspond to the shape of the surface, less substantial differences in height that correspond to undulations, of the surface, and minute differences in height that correspond to roughness of the surface. The desired measuring values can be separated from one another by means of a downstream filter, namely, a low-pass filter for the shape, a bandpass filter for the undulations, and a high-pass filter for the roughness.
According to an additional refinement of this embodiment of the invention, a second acceleration transducer is provided for transforming the movements of the probe in the longitudinal direction (X-direction), which is essentially perpendicular to the direction of the tip (Z-direction), into corresponding acceleration data. A second integrator that performs a double integration of the movements of the second acceleration transducer with respect to time and thus transforms the movements into longitudinal movement data, is connected in series with this second acceleration transducer. In this context, the term “movement” refers to a movement of the probe
Hommelwerke GmbH
Larkin Daniel S.
Shlesinger & Arkwright & Garvey LLP
LandOfFree
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