Probe head for a coordinate measuring machine

• US 20050229420A1
• Filed: 04/14/2005
• Published: 10/20/2005
• Est. Priority Date: 10/23/2002
• Status: Active Grant

• Current Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Inventors: Brenner, Kurt, Roth, Roland, Jenisch, Walter, Stacklies, Horst
• Granted Patent: US 7,284,337 B2
• Time in Patent Office: Days
• US Class Current: 33/558
• CPC Class Codes: G01B 7/012 Contact-making feeler heads therefor

Abstract

A probe head for a coordinate measuring machine has a stylus resiliently suspended in a housing. A sensor arrangement serves for detecting deflections of the stylus relative to the housing. The sensor arrangement comprises at least one Hall sensor having a magnet and a Hall element arranged in a vicinity to each other. When the stylus is deflected, the magnet is laterally passed by the Hall element in a direction defined from the North Pole to the South Pole of the magnet or vice versa. A Hall voltage of changing polarity can be tapped at the Hall element then. A preferably linear range around the polarity change is processed in order to determine the deflection of the stylus.

Claims

1. A probe head for a coordinate measuring machine, comprising:

a housing,

a stylus resiliently suspended in the housing, and

a sensor arrangement for detecting deflections of the stylus relative to the housing, the sensor arrangement comprising at least one Hall sensor having a magnet and having a Hall element arranged in a vicinity of the magnet,

wherein the magnet has a North Pole and a South Pole, and

wherein the magnet is arranged for laterally passing by the Hall element in a direction from the North Pole to the South Pole or vice versa, when the stylus is deflected, such that a Hall voltage having a polarity change and a voltage range around the polarity change is generated by the Hall element, and

wherein the sensor arrangement is adapted to process said voltage range for providing a continuous measure of the deflection of the stylus.

2. The probe head of claim 1, wherein the at least one Hall sensor is configured to generate the Hall voltage such that the voltage range is substantially linear.

3. The probe head of claim 1, wherein the sensor arrangement comprises at least one first Hall sensor having a first magnet and a first Hall element and at least one second Hall sensor having a second magnet and a second Hall element, with the first Hall sensor being designed for providing a first Hall voltage as a function of a deflection of the stylus in a direction perpendicular to the stylus, and with the second Hall sensor being designed for providing a second Hall voltage as a function of a deflection of the stylus in a direction parallel to the stylus.

4. The probe head of claim 3, wherein the first magnet is connected to the stylus and the first Hall element is connected to the housing.

5. The probe head of claim 3, comprising a plurality of first and second Hall sensors having a plurality of first and second magnets distributed around the stylus.

6. The probe head of claim 5, wherein the first magnets are aligned with their North Poles all facing in the same direction.

7. The probe head of claim 5, wherein the second magnets are aligned with their North Poles facing in opposite directions.

8. The probe head of claim 5, wherein at least two second magnets are provided at an axial spacing from one another.

9. The probe head of claim 3, wherein the stylus is suspended for swiveling about a fulcrum defining a radial plane perpendicular to the stylus, wherein the first magnet has a first symmetry plane defined between its North Pole and its South Pole, and wherein the first magnet is located with the first symmetry plane lying in the radial plane, when the stylus is in rest position.

10. The probe head of claim 3, wherein the first magnet has a longitudinal axis extending from the North Pole to the South Pole, with the first magnet being arranged with the longitudinal axis substantially parallel to the stylus.

11. The probe head of claim 9, further comprising a holder extending radially away from the stylus, wherein the first magnet is arranged on the holder.

12. The probe head of claim 9, wherein the housing comprises an axial inner wall extending in a direction parallel to the stylus, the first Hall element being arranged on the axial inner wall.

13. The probe head of claim 3, wherein the second magnet has a second symmetry plane defined between its North Pole and its South Pole, and wherein the second magnet is located with the second symmetry plane lying in the radial plane, when the stylus is in rest position.

14. The probe head of claim 3, further comprising an arm extending from the housing in a direction orthogonal to the stylus, wherein the second Hall element is arranged on said arm and the second magnet is arranged on the stylus.

15. The probe head of claim 3, further comprising a diaphragm for cardanically suspending the stylus in the housing.

16. The probe head of claim 15, wherein the diaphragm comprises at least one cutout, with the first and second magnets projecting into the cutout.

17. The probe head of claim 3, wherein the stylus is suspended for swiveling about a fulcrum defining a radial plane perpendicular to the stylus, and wherein the first magnet and the first Hall element are located with an axial spacing from the radial plane.

18. The probe head of claim 17, further comprising a holder extending radially away from the stylus, wherein the first magnet is arranged on the holder.

19. The probe head of claim 18, wherein the first magnet has a longitudinal axis extending from the North Pole to the South Pole, the first magnet being arranged with the longitudinal axis substantially orthogonal to the stylus.

20. The probe head of claim 17, wherein the housing comprises a radial inner wall extending in a direction orthogonal to the stylus, the first Hall element being arranged on the radial inner wall.

21. The probe head of claim 17, further comprising an arm extending from the housing in a direction orthogonal to the stylus, wherein the second Hall element is arranged on said arm and the second magnet is arranged on the stylus.

22. The probe head of claim 1, wherein the magnet and the Hall element each are provided with spherical surfaces for maintaining a constant air gap between the magnet and the Hall element during swiveling movement of the stylus.