Position determining apparatus

Details Position determining apparatus Position determining apparatus

1990-12-05

1992-02-25

Cuchlinski, Jr., William A.

Geometrical instruments

Gauge

Having a movable contact probe

33558, 33559, 33561, G01B 700, G01B 728

Patent

active

050901311

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to position determining apparatus and has application, for example, in measuring probes.
Measuring probes are known, for example from UK Patent No. 1,455,977 in which a movable stylus carrier is supported on seats within the probe body in a rest position, when no force acts on the stylus. In a measuring operation the probe is moved by a machine until the stylus contacts a workpiece to be measured whereby a force is applied to the stylus causing the stylus to be displaced from the rest position by tilting or axial displacement.
It is important for accurate measurement of workpieces that the stylus carrier returns to its rest position with great precision after each displacement so that the stylus ball, which contacts the workpiece returns to the same position in space relative to the probe.
In a probe which uses a kinematic location for the stylus carrier the position to which the stylus carrier returns is influenced by friction at the seats. Thus the position of the stylus ball in space can vary after each displacement and the so-called rest position of the stylus may not be exactly the same prior to each measurement. A spring may be used to assist in overcoming the frictional forces at the seats, but this has been found not to completely solve the problem without unacceptably high spring forces.
A similar problem occurs in a variety of pieces of apparatus particularly in the measuring field where one member or part is to be repeatedly mounted on and removed from another part with great accuracy. Examples of such apparatus are robots; probe heads for mounting measuring probes, and in machine tools which carry probes for measuring workpieces.
This problem is solved in accordance with the invention in apparatus having a first member supported on a second member by determining in all directions the displacement of a part of the supported member which is caused by a change in the force applied by the supported member to a part of the support.
This is most conveniently done by measuring the forces on sufficient parts of the support or the supported member to enable the displacement of the supported member in all of the required directions to be determined.
In the case of a kinematically mounted stylus carrier in a measuring probe for example, in which six confronting support points are provided on each of the movable stylus carrier and the fixed structures, this can be achieved by determining the translational and rotational displacements about three orthogonal axes of each of the support points on the stylus carrier due to any change in the forces between the fixed and movable structures.
In preferred embodiments of the invention this determination is made by measuring variations in the forces on the fixed structure or the stylus carrier using strain measuring devices adjacent the support points thereon, although other methods are possible.
Examples of the invention will now be more particularly described with reference to the accompanying drawings in which:
FIG. 1 is a sectional elevation of a probe according to the present invention.
FIG. 2 is an enlarged view of one of the supports for the stylus carrier within the probe of FIG. 1 and showing the strain measuring devices.
FIG. 3 is an electrical circuit for producing an electrical signal from the strain measuring devices, and
FIG. 4 is a diagrammatic illustration of the electronics required for the analysis of the signals from the strain measuring devices.
FIGS. 5a and 5b are respectively an end elevation and cross-section of an alternative support arrangement for the stylus holder of a measuring probe, and
FIGS. 6a and 6b are respectively an end elevation and cross-section of a further alternative support arrangement for the stylus holder of a measuring probe.
FIGS. 7, 7a and 7b show the nomenclature for the calculations required by the computer.
Referring now to the drawings, a probe comprises a housing 2 which constitutes a fixed member of the probe. The housing has an axis 2A and which terminates in a shank 4 for connecting

REFERENCES:
patent: 4364180 (1982-12-01), Willhelm et al.
patent: 4513507 (1985-04-01), Laskowski
patent: 4550418 (1985-10-01), Deis
patent: 4567665 (1986-02-01), Ernst
patent: 4578873 (1986-04-01), Klingler et al.
patent: 4769919 (1988-09-01), Lloyd et al.
patent: 4815214 (1989-03-01), Enderle et al.
patent: 4854050 (1989-08-01), McMurtry
patent: 4897929 (1990-02-01), Ernst et al.
patent: 4934065 (1990-06-01), Hajdukiewicz

Affiliated with

Also associated with

Rating

Position determining apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Position determining apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Position determining apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1884449