Renishaw Plc

Renishaw Metrology Limited

David Wilson

David R McMurtry

Peter Kenneth Hellier

Gillies D Pitt

Peter Hajdukiewicz

Peter G Lloyd

Raymond J Chaney

Christopher C Dunning

Stephen I Gregorig

A touch probe includes a stylus module (54) and a sensing module (52) to which the stylus module is releasably securable by a magnetic coupling. The sensing module comprises a strain sensitive load cell on which the stylus module is supported, and which senses strain in the stylus on contact with a surface. The stylus module provides for overtravel of the probe; a stylus-supporting member being biased into a kinematic rest position with respect to the casing of the stylus module. The biasing force in the stylus module is chosen with regard to the length and configuration of stylus. This modular system enables automated stylus changing without the need to adjust the biasing force on the stylus-supporting member when different lengths of styli are employed.

Touch probe

Contact probes

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.

A touch-trigger probe is provided with a sensor (which may be a mirror (106), an optical fibre (206), or a bi-refringent element (307)) which changes state by vibrating or undergoing strain when a stylus connected to the probe contacts a workpiece. The sensor is typically provided on (in the case of the mirror (106)), or in (in the case of the optical fibre (206)) the stylus. The change of state of the sensor causes a change in the path length, polarization state, or intensity of light waves conveyed by the sensor. An interferometer may be provided to detect such changes. Other forms of electromagnetic waves may be used to the same effect.

Touch probe including a waveguide

Workpiece inspection

A scale is fixed to one part of a position determining apparatus, and a read head is relatively movable on the other part of the apparatus. Incremental scale marks are regularly spaced along the scale and are counted in a counter to give an indication of relative position of the scale and read head. The marks may for example be recorded magnetically. Some scales are distinguishable from the other, e.g., by having different amplitudes. Positioning information can then be encoded in a binary word. This can either be absolute position values, or error correction information.

Scales for position determining apparatus having marks of different

Position determination apparatus

The probe has a piezo-electric sensor (22A) for determining initial contact of a stylus (16) with a workpiece (4). It also has a kinematic support (18) made up of confronting electrical contacts (19, 20) which are connected to indicate displacement of the stylus from a rest position and correct reseating on the kinematic support. The sensor (22A) and the electrical contacts (19, 20) are connected to an electrical circuit (24) within the probe. The circuit (24) has only two terminals connecting it to an external interface (9), which both receives the signals from and supplies power to the sensor (22A) and the contacts (19, 20). This enables the receipt of a signal from the contacts (19, 20) to provide a fail-safe backup to the signal from the sensor (22A) and to indicate correct reseating of the probe, while maintaining the interface (9) compatible with prior art probes having only one workpiece-engagement sensing arrangement with two terminals.

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Stonehouse, United Kingdom

David Wilson