Probe head with indexing mechanism

Abstract

A probe head (10) includes a support (12) by which the probe head is retained on the quill of a coordinate positioning machine, and a rotor (14) which is magnetically retained on the support (12). The rotor (14) is rotatable between a plurality of indexed angular positions provided by a ring or balls (26) and three adjacently positioned pairs of rollers (24). A drive dog shaft (20) is linearly movable to disengage the balls (26) from the rollers (24), and rotatable to rotate the rotor (14) to a new indexed position, whereupon the drive dog shaft (20) is retracted to re-engage a set of three balls (26) with the rollers (24). Exchange of a measuring probe (16) is performed by removing the entire rotor (14), and exchanging it for a further rotor carrying a different measuring probe. The engagement elements provided by rollers (24) and balls (26) thus serve the functions of (a) indexing and (b) repeatably .[.retaining.]. .Iadd.positioning .Iaddend.a rotor (14) on the support (12). This reduces the number of kinematic locations required between the movable arm of the machine and the probe (16) during the course of normal operation of a probe head to which a number of probes (16) are releasably couplable.

I claim: 
     
       1. A probe head for orienting a probe relative to .[.the.]. .Iadd.a .Iaddend.movable arm of a coordinate positioning machine, comprising: a support by which the probe head is connectable to the arm of the machine;   a rotor for carrying a probe;   retaining means for releasably retaining the rotor on the support, to enable one rotor to be exchanged for another;   indexing means for providing a plurality of .Iadd.angularly .Iaddend.indexed .[.angular.]. positions of .[.the.]. .Iadd.said .Iaddend.rotor relative to .[.the.]. .Iadd.said .Iaddend.support, comprising a first set of engagement elements provided on one of .[.the.]. .Iadd.said .Iaddend.rotor and support, and a plurality of sets of second engagement elements provided on the other of .[.the.]. .Iadd.said rotor .Iaddend.and .Iadd.said .Iaddend.support, said first set of engagement elements being engageable with each set of said plurality of sets of second engagement elements to provide, at each .Iadd.angularly .Iaddend.indexed position .Iadd.of the plurality of angularly indexed positions.Iaddend., a stable.[.,.]. .Iadd.and .Iaddend.repeatable .[.rest.]. position of .[.the.]. .Iadd.said .Iaddend.rotor on .[.the.]. .Iadd.said .Iaddend.support;   coupling and decoupling means .Iadd.provided on said rotor and said support .Iaddend.for engaging and disengaging said first set of engagement elements with a set of said second engagement elements; and   driving means .Iadd.provided on said support .Iaddend.for rotating said rotor relative to said support substantially about an axis when said first and second engagement elements are disengaged, thereby to rotate said rotor from one .Iadd.angularly .Iaddend.indexed position to another.   
     
     
       2. A probe head according to claim 1, wherein said retaining means comprises a magnet provided on one of .[.the.]. .Iadd.said .Iaddend.rotor and .Iadd.said .Iaddend.support, and a ferromagnetic element provided on the other of .[.the.]. .Iadd.said .Iaddend.rotor and .Iadd.said .Iaddend.support to axially urge said first and .[.a.]. .Iadd.one of said plurality of sets of .Iaddend.said second .[.set of.].engagement elements into engagement. 
     
     
       3. A probe head according to claim 2, wherein said driving means are provided by .[.an axially movable and.]. .Iadd.a .Iaddend.rotatable drive dog on .[.the.]. .Iadd.said .Iaddend.support, said drive dog having a set of detent elements configured to engage a corresponding set of detent elements provided on said rotor. 
     
     
       4. A probe head according to claim 3, wherein said .Iadd.drive dog is axially moveable and said .Iaddend.coupling and decoupling means are provided by .[.said axially movable and rotatable.]. .Iadd.axial movement of said .Iaddend.drive dog. 
     
     
       5. A probe head according to claim 3, wherein said magnet and ferromagnetic element are each provided on one of .[.the.]..Iadd.said .Iaddend.drive dog and .Iadd.said .Iaddend.rotor. .Iadd. 
     
     
       6.  A probe head for orienting a probe relative to a moveable arm of a coordinate positioning machine, comprising: a support structure by which the probe head is connectable to the moveable arm of the machine;   a rotor rotatable relative to the support about an axis for carrying a probe;   an indexing device comprising first and second sets of mutually engageable indexing elements on the rotor and support structure respectively, engageable in a plurality of angular orientations about said axis, to provide a corresponding plurality of angularly indexed positions at which the rotor has a stable and repeatable position on the support;   a coupling and decoupling device for engaging and disengaging the first and second sets of indexing elements;   a driving device for rotating the rotor relative to the support structure when the first and second sets of indexing elements are disengaged, thereby to rotate the rotor from one angularly indexed position of the plurality of angularly indexed positions to another, the driving device including first and second sets of mutually engageable engagement elements provided on the rotor and support structure, and wherein means are provided for disengaging the engagement elements during coupling of the first and second sets of indexing elements. .Iaddend..Iadd.7. A probe head according to claim 6, wherein the coupling and decoupling device includes a magnetic element connected to one of the rotor and the support structure and a ferromagnetic element connected to the other of the rotor and the support structure. .Iaddend..Iadd.8. A probe head according to claim 7, wherein the coupling and decoupling device further comprises a motor and an axially movable drive dog, actuable by the motor and connected to the support structure for engaging the rotor, thereby to increase and decrease the separation between the magnetic and ferromagnetic elements. .Iaddend..Iadd.9. A probe head according to claim 8, wherein said engagement elements are provided on the drive dog and the rotor.   
     
     
        .Iaddend..Iadd.10.  A probe head according to claim 8, wherein the magnetic element is provided on one of the drive dog and the rotor and the ferromagnetic element is provided on the other of the drive dog and the 
     
     
        rotor. .Iaddend..Iadd.11.  A probe head for orienting a probe relative to a movable arm of a coordinate positioning machine, comprising: a support by which the probe head is connectable to the arm of the machine;   a rotor, rotatable relative to the support about an axis, for carrying a probe;   an indexing device comprising first and second sets of mutually engageable indexing elements provided on the rotor and the support respectively, engageable in a plurality of angular orientations about the axis to provide a corresponding plurality of angularly indexed positions at which the rotor has a stable and repeatable position on the support;   coupling and decoupling device for engaging and disengaging the first and second sets of indexing elements;   a driving device for rotating the rotor relative to the support when the first and second sets of indexing elements are disengaged, thereby to rotate the rotor from one indexed position to another; and   a retaining device for releasably retaining the rotor on the support to   
     
     
        enable one rotor to be exchanged for another. .Iaddend..Iadd.12.  A probe head according to claim 11, wherein said retaining device comprises a magnet provided on one of the rotor and the support and a ferromagnetic element provided on the other of the rotor and the support to axially urge the first and second sets of indexing elements into engagement. 
     
     
        .Iaddend..Iadd.13.  A probe head according to claim 12, wherein the coupling and decoupling device comprises an axially movable drive dog on the support. .Iaddend..Iadd.14. A probe head according to claim 12, wherein the axially movable drive dog is rotatable and comprises sets of mutually engageable driving elements provided on the drive dog and rotor 
     
     
        thereby to provide the driving device. .Iaddend..Iadd.15.  A probe head according to claim 14, wherein means are provided for disengaging the sets of driving elements on the drive dog and the rotor during coupling of the 
     
     
        first and second sets of indexing engagement elements. .Iaddend..Iadd.16. A probe head according to claim 13, wherein the magnet and ferromagnetic element are each provided on one of the drive dog and rotor. 
     
     
        .Iaddend..Iadd.17.  A probe head for orienting a probe relative to a moveable arm of a coordinate positioning machine, comprising: a support by means of which the probe head is connectable to the moveable arm of the machine;   a rotor for carrying a probe, the rotor is rotatable relative to the support about an axis;   an indexing device comprising first and second sets of mutually engageable indexing elements on the rotor and the support respectively, engageable at a plurality of angular orientations about the axis to provide a corresponding plurality of angularly indexed positions at which the rotor has a stable and repeatable position on the support;   a coupling and decoupling device for engaging and disengaging the first and second sets of indexing elements comprising a magnetic element provided on one of the rotor and the support and a ferromagnetic element on the other of the rotor and the support, for axially urging the first and second sets of indexing elements into engagement, and an axially moveable member provided on the support for axially displacing the rotor relative to the support thereby to effect the disengagement; and   a driving device for rotating the rotor relative to the support substantially about the axis when the first and second sets of indexing elements are disengaged, thereby to rotate the rotor from one indexed   
     
     
        position to another. .Iaddend..Iadd.18.  A probe head according to claim 17, wherein the one of the magnetic element and the ferromagnetic element on the support is provided on the axially movable member. 
     
     
        .Iaddend..Iadd.  .  A probe head according to claim 18, wherein the axially moveable member is a rotatable drive dog, and first and second sets of mutually engageable driving elements are provided upon the drive dog and the rotor respectively, the driving device being provided by the drive dog, the driving elements, and a motor for rotating the drive dog. .Iaddend..Iadd.20. A probe head for orienting a probe relative to a moveable arm of a coordinate positioning machine, comprising: a support by means of which the probe head is connectable to the moveable arm of the machine;   a rotor for carrying a probe, the rotor rotatable relative to the support about an axis;   an indexing device comprising first and second sets of mutually engageable indexing elements on the rotor and the support respectively, engageable at a plurality of angular orientations about said axis to provide a corresponding plurality of angularly indexed positions at which the rotor has a stable and repeatable position on the support;   a biasing device for axially biasing the rotor into engagement with the support;   an axially moveable drive dog on the support which is engageable with the rotor, and a motor for actuating the drive dog, the drive dog being actuable by the motor to increase and decrease the axial separation of the rotor and support and, thereby, in cooperation with the biasing device, correspondingly disengage and engage the indexing elements;   the drive dog being additionally rotatable substantially about the axis, and having a first set of driving elements on an end thereof engageable with a second set of driving elements on the rotor, to enable rotation of the rotor by the drive dog relative to the support when the indexing   
     
     
        elements are disengaged. .Iaddend..Iadd.21.  A probe head according to claim 20, wherein the biasing device comprises a magnetic element provided on one of the rotor and the support and a ferromagnetic element provided on the other of the rotor and the support, the motor increases and decreases the separation between the magnetic elements. .Iaddend.