Touch probe

• US 5,339,535 A
• Filed: 02/19/1992
• Issued: 08/23/1994
• Est. Priority Date: 02/23/1990
• Status: Expired due to Term

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw Metrology Limited (Renishaw PLC)
• Inventors: Hajdukiewicz, Peter, McMurtry, David R., Wilson, David, Hellier, Peter K.
• Primary Examiner(s): Will, Thomas B.
• Application Number:
  US07/836,729
• Time in Patent Office: 916 Days
• Field of Search: 33/556, 33/558, 33/557, 33/559, 33/560, 33/561
• US Class Current: 33/561
• CPC Class Codes: B23Q 5/58 Safety devices protecting the operator B23Q11/0089
• CPC Class Codes: G01B 5/012 Contact-making feeler heads therefor
• CPC Class Codes: G01B 7/002 Constructional details of contacts for gauges actuating one or more contacts G01B7/016 takes precedence
• CPC Class Codes: G01B 7/012 Contact-making feeler heads therefor

Abstract

A touch probe for use on a coordinate positioning machine includes a stylus module and a sensing module securable to a movable arm of the positioning machine for releasably supporting the stylus module. The sensing module can include a sensor for detecting contact between the stylus and a surface and/or for detecting displacement of the stylus module relative to the movable arm. The stylus includes a support structure, releasably supported by the stylus module, and a stylus-supporting member for supporting the stylus, with the stylus-supporting member being biased into a rest position with respect to the support structure. The stylus-supporting member is displaceable from the rest position and relative to the support structure when a deflection force acts on the stylus, and returns to the rest position when the deflecting force is removed.

Claims

1. A touch probe for use on a coordinate positioning machine, the probe comprising:

a stylus module having a support structure and a stylus-supporting member for supporting a stylus, the stylus-supporting member being biased into a rest position with respect to the support structure, from which position the supporting member is displaceable relative to the support structure when a deflecting force acts on the stylus, and to which position it may return when said deflecting force is removed;

a sensing module for supporting the stylus module, the sensing module being securable to a movable arm of the machine;

means, acting on the support structure of said stylus module, for releasably retaining said stylus module on said sensing module;

wherein said sensing module comprises means for detecting contact between the stylus and a surface.

2. A touch probe according to claim 1 wherein said means for detecting contact includes means for sensing strain, resulting from deformation of the stylus, and transmitted from said stylus to said sensing module via the support structure of the stylus module.

3. A touch probe according to claim 2 wherein said sensing module comprises a fixed structure by which said sensing module may be secured to the movable arm of the machine, and said means for sensing strain includes a load cell, said load cell having a first portion connected to said fixed structure, and a second portion on which, in use, said stylus module is retained, a relatively weak structure interconnecting the first and second portions, and means provided between the first and second portions for detecting strain in said relatively weak structure.

4. A touch probe according to claim 3 wherein said fixed structure is provided by a cylindrical housing defining an axis, and the support structure of the stylus module includes an upper and a lower casing rigidly connected to each other, the stylus module further comprising an intermediate cylindrical skirt, extending from the lower casing to the upper casing;

the skirt being axially movable between a first position in which the skirt rests on the lower casing, and a second position;

the skirt terminating at its upper end in a rim having a diameter which enables the skirt to abut the housing in said second position; and

wherein the skirt includes a catch member engageable by the stylus-supporting member when the stylus-supporting member is displaced axially from said rest position.

5. A touch probe according to claim 4, wherein when the skirt occupies the first position, the axial distance between the catch member and the upper casing is larger than the axial distance between the rim and the housing.

6. A touch probe according to claim 1, wherein said means for releasably retaining said stylus module on said sensing module includes means for magnetically retaining said stylus module on said sensing module.

7. A touch probe according to claim 6 wherein, in use, said stylus module is kinematically supported on said sensing module.

8. A touch probe for use on a coordinate positioning machine comprising:

a stylus module support structure and a stylus-supporting member for supporting a stylus, the stylus-supporting member being biased into a rest position with respect to the support structure, from which position the supporting member is displaceable relative to the support structure when a deflecting force acts on the stylus, and to which position it may return when said deflecting force is removed;

a sensing module for supporting the stylus module, said sensing module including a fixed structure by which said sensing module may be secured to a movable arm of the machine, and a suspension mechanism enabling displacement of the stylus module relative to the fixed structure;

means, acting on the support structure of said stylus module, for releasably retaining the stylus module on the suspension mechanism of said sensing module;

said sensing module comprising means for detecting displacement of the stylus module relative to the movable arm.

9. A touch probe according to claim 8 wherein said means for releasably retaining the stylus module on the suspension mechanism of said sensing module includes means for magnetically retaining said stylus module on said suspension mechanism of the sensing module.

10. A touch probe according to claim 9 wherein said stylus module is kinematically supported on said sensing module.

11. A stylus module for use in conjunction with a sensing module, to which said stylus module is releasably securable, as a touch probe on a coordinate positioning machine, said stylus module comprising:

a support structure having a set of engagement elements suitable for forming a kinematic support with a corresponding set of engagement elements provided on a sensing module;

a stylus supporting member, for supporting a workpiece contacting stylus, the stylus-supporting member being biased into a rest position with respect to the support structure, from which position the supporting member is displaceable relative to the support structure when a deflecting force acts on the stylus, and to which position the supporting member may return when said deflecting force is removed;

wherein no sensors for determining stylus-workpiece contact are provided on said stylus module.

12. A stylus module according to claim 11 further comprising at least one ferromagnetic element provided on said support structure, to enable magnetic retention of said stylus module on a sensing module.

13. A stylus module according to claim 11 wherein the support structure has an axis, and includes an upper casing and a lower casing rigidly connected to each other and axially spaced apart, the stylus module further comprising:

an intermediate cylindrical skirt extending from the lower casing to the upper casing;

the skirt being axially movable between a first position in which the skirt rests on the lower casing, and a second position; and

wherein

the skirt includes a catch member engageable by the stylus-supporting member when the stylus-supporting member is displaced axially from the rest position.