Abstract: A programmable probe system for a machine includes a probe, an interface and a two-way optical communication link between them. The probe includes signal conditioning electronics, a power supply, a plurality of on/off switch circuits whereby the electronics may be connected to, and disconnected from, the power supply by a variety of means, for example, an optical signal, or a mechanical switch and a timing circuit. The probe also includes a microprocessor which can be externally programmed from the interface to select one or other of the on/off switch circuits. Where the probe includes a radio transmission for transmitting probe data to the interface, it is also provided with a synthesiser for generating different operating frequencies for the transmission system. The microprocessor can also be programmed from the interface to change the frequency of the system where required.

Abstract: A mount 10 for a part to be measured (e.g. a tooth 20 which is to have its surface measured) has three locators 14 which allow repeatable positioning of the mount on a holder 12. The mount 10 and its locators are manufactured in a low cost way e.g. by means of chemical etching, stamping, piercing, folding, embossing or moulding. The mount may be sheet material or a moulded plastics, and a support 22 for the part may be provided. The material of the mount may be magnetisable or have magnetic properties for its attraction and position securement to the holder 12. A mount transit system is described (FIGS. 10 and 11) for placing and removing a mount on the holder.

Abstract: An optical signal transmission circuit for a probe is switched on by an optical switch-on signal comprising a burst 42 of pulses having a predetermined length. This is detected by a circuit which discriminates whether an input signal is a genuine switch-on signal or an interference burst 44, on the basis of the duration of the switch-on signal.

Abstract: A touch probe has a stylus holder 16 which is supported on a radially extending flange 14 in a kinematic seat comprising pairs of balls 20 supporting rollers 24. To avoid the use of glue to fix the balls in position, the balls are located and clamped in recesses 22 on flange 14. Clamping pressure is provided by a plug 30 which is forced towards the flange by rolling a lip 54 over the protruding end of the plug. Other alternative constructions for providing the clamping force are described. An electrical circuit through the balls for producing a trigger signal includes a flexible member 40 on which electrical conducting elements 44 are formed. The member is positioned on the flange to overlie the recesses so that it is deformed into the recesses when the clamping force is applied. By making use of the clamping force in this way good electrical connections between the balls and the conducting elements is ensured and the need to connect wires to the balls is avoided.

Abstract: A magazine which retains tools within the working area of a machine tool has a storage port which is mounted to a base via a compliant mount which provides two degrees of rotational freedom, and two degrees of translational freedom. The mount enables the storage port to be brought into register with a chuck on the spindle of the machine as a result of mutual engagement between surfaces on the storage port and the chuck during a tool change operation. The tool is retained within the chuck by using hydraulic pressure chambers in the chuck to deform an interior wall of the chuck cavity, and thereby causing it to grip the sides of the tool. Such a retention mechanism requires a relatively small clearance of the tool within the chuck when the wall is underformed, thereby necessitating the compliantly mounted storage port and alignment surfaces.

Abstract: Apparatus which can be used to calibrate, or provide measurement data on, a machine. The apparatus comprises two structures each with three spherical supports spaced in a triangular array thereon. The supports may be balls or sockets. The structures are interconnected by six members and each support has the ends of two members connected to it. The members are passive extensible measuring bars and the structures are respectively connected to fixed and movable parts of a machine so that movement of the machine parts causes relative movement between the structures and varies the lengths of the measuring bars. From measurements of the lengths of the measuring bars the actual movement of the machine part can be determined. Calibration of the spherical supports is carried out using a measuring bar which is pre-calibrated in a Zerodur jig.

Abstract: A rotary bearing has a pair (32,40) of bearing members, one of which has convex (34) and planar (36) surface portions, and the other of which has concave (42) and planar (44) surface portions. The convex and concave surface portions and the planar surface portions of the two bearing members bear against each other via an interstitial bearing medium of air, with the axial forces between the convex and concave surfaces counteracting the axial forces between the planar surface portions. When incorporated into a drive mechanism, one of the bearing members is connected to a drive shaft via a first torsionally stiff flexible diaphragm (130), and the other bearing member is mounted to a motor (50) (which rotates the drive shaft) via a second torsionally stiff flexible diaphragm. During operation, flexing of the diaphragms (110,130) accommodates eccentricity in the mounting of the motor (50) without transmitting unwanted loads to the bearing.

Abstract: A coordinate positioning machine comprises a fixed structure including a table and a supporting frame (314), rigidly connected together. A moveable arm (310) is suspended from the frame by means of three powered telescopic struts (316), each of which is universally pivotally connected to both the arm and the frame. As a consequence the moveable arm is able to move with three rotational degrees of freedom. Movement of the arm with each of these degrees of freedom is constrained by a passive device (340), connected to the arm and the fixed structure, and which eliminates all rotational movement of the arm, while simultaneously permitting translation thereof.

Abstract: Velocity dependent measurement errors made by coordinate measuring machines (CMMs) are corrected by deriving a polynomial expression which relates components of the errors to the relative velocity between the probe and the workpiece. A calibration is performed to establish the constant of the polynomial for different stylus configurations of the probe and these constants are stored. During a measuring process the probe produce analogue output signals from which a trigger signal is generated to latch the output signals of the machine measuring devices. The probe and machine output signals are monitored and recorded at clocked intervals over a range of positions within which lies the position at which the machine readings were latched. Actual relative velocity values are calculated at each position and, using these values and the stored constants, the errors in the machine readings at each position can be calculated from the polynomial.

Abstract: An opto-electronic scale reading apparatus includes a scale 10 and a readhead 14 movable one relative to another. The readhead produces a pair of quadrature pulses which enable the generation of an incremental count corresponding to the displacement of the readhead 14 relative to a reference mark 80. The reference mark 80 is a permanent magnet mounted on the scale substrate inside a non-ferromagnetic casing 90. A pair of differential Hall sensors 62A,B within the readhead, and associated processing circuitry generate a step-change ZERO pulse when the readhead 14 and scale 10 are in a particular relative position. This relative position can be adjusted to enable corresponding adjustment of the relative phase of the quadrature pulses emitted from the readhead and the ZERO pulse, by means of a ferromagnetic adjusting screw 92.

Abstract: A rotary bearing has a pair (32,40) of bearing members, one of which has convex (34) and planar (36) surface portions, and the other of which has concave (42) and planar (44) surface portions. The convex and concave surface portions and the planar surface portions of the two bearing members bear against each other via an interstitial bearing medium of air, with the axial forces between the convex and concave surfaces counteracting the axial forces between the planar surface portions. When incorporated into a drive mechanism, one of the bearing members is connected to a drive shaft via a first torsionally stiff flexible diaphragm (130), and the other bearing member is mounted to a motor (50) (which rotates the drive shaft) via a second torsionally stiff flexible diaphragm. During operation, flexing of the diaphragms (110,130) accommodates eccentricity in the mounting of the motor (50) without transmitting unwanted loads to the bearing.

Abstract: A coordinate measuring machine carries a modular touch trigger probe 100, via an adaptor 200, on its movable arm 10. The probe 100 consists of a retaining module 102 which is mounted to the adaptor 200, and a stylus module 104 which is magnetically connected to the retaining module 102 in a manner which enables the exchange of one stylus module 104 for another. The adaptor consists of a pair of coupling members 202,204 which are urged into mutual engagement by magnets 212. Automatic exchange of stylus modules occurs by using movement of the arm 10 to disengage a stylus module 104 from the retaining module 102. Similarly, the exchange of one probe for another is carried out by using movement of the arm 10 to disengage the lower coupling member 204 from the upper coupling member 202.

Abstract: A laser interferometer measuring system generates a series of digital output quadrature pulses corresponding to movement of a retroreflector 18. The output pulses are intended for receipt by a master counter containing an incremental count corresponding to displacement of the retroreflector 18. Errors present in the output pulses due to environmental or geometrical error sources in the interferometer may be compensated for by scaling the output pulses in accordance with a correction factor K. The output pulses are stored in a first counter 30, 130; a series of secondary pulses, being either the output pulses as scaled, or independently generated by a signal generator 200, are sent both to the master counter and a second counter 80, 180. A processor 50, 150 continually monitors the value of the second counter, and compares this with an actual value of displacement, equal to the product of the correction factor and the instantaneous value of the first counter.

Abstract: A system is disclosed enabling the automated exchange of touch probes (34,38) on an articulating probe head 40. The touch probes are mounted to adaptors 32, and are housed in storage ports 20 of a magazine. An adaptor 32 is repeatably located upon the retaining module by the mutual engagement of kinematic support elements 50,52 on the probe head 40 and adaptor 32 respectively. The support elements 50,52 are urged into mutual engagement by a locking mechanism having a spigot 60 on the probe head 40 which engages a cam 62 on the adaptor 32; rotation of the cam 62 locks/unlocks the support elements into mutual engagement. During an exchange operation the cam 62 is rotated by a screwdriver 80 in the storage port. Rotation of the screwdriver 80 is caused by relative movement of the storage port and the support plate 14, which is part of the support structure of the magazine.

Abstract: A coordinate measuring machine carries a modular touch trigger probe 100, via an adaptor 200, on its movable arm 10. The probe 100 consists of a retaining module 102 which is mounted to the adaptor 200, and a stylus module 104 which is magnetically connected to the retaining module 102 in a manner which enables the exchange of one stylus module 104 for another. The adaptor consists of a pair of coupling members 202,204 which are urged into mutual engagement by magnets 212. Automatic exchange of stylus modules occurs by using movement of the arm 10 to disengage a stylus module 104 from the retaining module 102. Similarly, the exchange of one probe for another is carried out by using movement of the arm 10 to disengage the lower coupling member 204 from the upper coupling member 202.

Abstract: A readhead (18) measures movement in the direction of arrow (20) with respect to a scale (10). The readhead (18) comprises an index grating (12), which interacts with light from the scale (10) to produce fringes in the vicinity of an analyzer grating (14). The resulting light modulations are detected by photodetectors (16). In order to reduce the sensitivity of the apparatus to changes in the ride height (h) of the readhead above the scale, at least two different optical path lengths are provided for light travelling from the scale (10) to the index grating (12), and/or from the index grating (12) to the analyzer (14). Various ways to achieve this are disclosed, e.g. a plate (22) of a refractive medium placed in one optical path, or tilting one of the gratings.

Abstract: The presence of Semtex plastic explosive in a sample such as a fingerprint is detected by Raman spectroscopy. RDX and PETN, the active chemical ingredients of Semtex, have strong Raman peaks at 885 cm.sup.-1 and 874 cm.sup.-1 respectively. Consequently, both these peaks can be detected in a Raman spectroscopic system by employing a filter having a narrow passband centered on 880 cm.sup.-1 and with a bandwidth of 20 cm.sup.-1. Such a filter is used in a Raman system used to scan airport boarding cards, or in a Raman microscope which produces images of fingerprints.

Abstract: A coordinate positioning machine comprises a fixed structure including a table and a supporting frame (314), rigidly connected together. A moveable arm (310) is suspended from the frame by means of three powered telescopic struts (316), each of which is universally pivotally connected to both the arm and the frame. As a consequence the moveable arm is able to move with three rotational degrees of freedom. Movement of the arm with each of these degrees of freedom is constrained by a passive device (340), connected to the arm and the fixed structure, and which eliminates all rotational movement of the arm, while simultaneously permitting translation thereof.

Abstract: Apparatus is provided for mounting a ball bar on a machine such that the ball bar can be rotated through 360.degree. in three orthogonal planes which intersect the center of a single ball (22) to calibrate relative movement between the spindle and a table of machine in all three planes. The apparatus consists of amounting device in the form of a block (10) on the machine table from which extends a rod (18) terminating in a socket (20) for supporting the ball (22). The rod extends from the block at a compound angle of 45.degree. to each of the three planes. The ball supports a socket on one end of a ball bar (34). A second mounting device is provided on the machine spindle in the form of a tool arm (26) from which extends a rod (28) terminating in a socket (30) for supporting a ball on the other end of the ball bar (34). The rod (28) extends at a compound angle of 45.degree. to all three planes. The ball bar is thus able to lie in any one of the three orthogonal planes and to be rotated through 360.degree.

Abstract: A touch trigger probe incorporates piezoelectric sensors 50, whose outputs are processed by an interface circuit. The interface circuit discriminates between signals generated from the piezoelectric sensors 50 as a result of machine vibration and those generated as a result of a genuine measurement event, by the use of a timing circuit 90. The timing circuit 90 compares the time intervals (t1-t2);(t2-t3) between attainment of first 11 and second 12, and second 12 and third 13 output signal levels from the sensor 50, and upon the basis of this comparison validates (or rejects) measurements made with the probe. Additionally, the interface determines whether measurements made with the probe are taken upon the basis of outputs generated by the sensors 50 due to a shock wave in the stylus 24 of the probe, or as a result of strain in the stylus 24; as an alternative, measurements may be made only on the basis of strain.