Metering device and corresponding method of operation

Abstract

A metrology apparatus comprising an indexed articulating joint comprising: a first body and a second body having mutually engageable engagement elements which can be locked together at a plurality of different angular orientations about a first axis to provide a plurality of angular index positions at which the first body and the second body can be locked relative to one another; the engagement elements of the first body and the second body being disengageable by axial relative movement of the first body and the second body along the first axis in a first direction so that the first body and the second body can be unlocked and relatively rotated about the first axis, and re-engageable by axial relative movement of the first body and the second body along the axis in a second direction; the indexed articulating joint further comprising at least one verification sensor configured to provide a measure of the relative spatial configuration of the first body and the second body when locked, and wherein the apparatus is configured so that with the first body and the second body locked together at an index position, the verification sensor is used to obtain a current measure of the relative spatial configuration of the first body and the second body, and wherein information derived from at least said current measure is compared with calibration information derived from at least one other measure of the relative spatial configuration of the first body and the second body obtained by the verification sensor when the first body and the second body were locked at said index position at an earlier point in time, in order to establish information about the locked state of the first body and the second body.

Description

[0001] This invention relates to an indexing articulated joint, particularly an indexing articulated joint for use in metrological equipment. For example, this invention relates to an indexing articulated joint for use in a hinge joint configured to support a measuring probe on a coordinate positioning device, such that the measuring probe can be arranged in multiple different rotational orientations.

[0002] As is well known in the field of coordinate positioning equipment, particularly in the field of coordinate measuring machines (CMMs), articulated joints (or rotary tables) for measuring probes (or objects) include articulated components that facilitate the reorientation of the measuring probe (or object) mounted thereon about at least one axis of rotation. Typically, an articulated joint will provide two orthogonal axes of rotation, but it may also provide fewer or more axes of rotation. Typically, a rotary table will provide one axis of rotation.

[0003] US 5185936 describes a hinge with one axis of rotation, and EP 2889573 and WO 2006 / 079794 describe hinges providing two orthogonal axes of rotation. As described in these documents, it is also known to provide hinges with an indexing mechanism that allows the relatively rotatable portions of the hinge to be locked into defined indexed positions. The indexing mechanism can be provided by providing two sets of interlocking members (one set on each relatively rotatable member). When the interlocking members engage, they lock, thus allowing relative rotation of the rotatable members. When the interlocking members disengage, the rotatable members rotate freely relative to each other, allowing them (and the measuring probe mounted thereon) to be repositioned to a new orientation before re-engaging, thereby locking the rotatable members (and the measuring probe mounted thereon) in the new orientation. Measurement operations can then be performed with the measuring probe held in a defined, known rotational orientation.

[0004] This invention relates to an improved articulated device.

[0005] According to a first aspect of the invention, a metrological device is provided comprising an indexing hinge joint, the indexing hinge joint comprising: a first body and a second body, the first body and the second body each having engagement elements capable of engaging each other, the engagement elements being lockable together about a first axis at a plurality of different angular orientations to provide a plurality of angular indexing positions in which the first body and the second body can be locked relative to each other; at least one verification sensor configured to provide a measurement of the relative spatial configuration of the first body and the second body in their locked state, and wherein the device is configured such that, when the first body and the second body are locked together at the indexing positions, the verification sensor is used to measure the relative spatial configuration of the first body and the second body, and wherein the information obtained from the measurement is compared with calibration information obtained from at least one other (in other words, previous) measurement of the relative spatial configuration of the first body and the second body when the first body and the second body are locked at the indexing position at an earlier time point (in other words, when the first body and the second body were previously locked at the indexing position) (e.g., by the verification sensor) to establish information about the engagement state of the first body and the second body.

[0006] The device configured according to the first aspect of the invention can help verify that the first and second bodies have been correctly locked together; for example, verifying that they have been locked together in substantially the same relative configuration as at a previous / earlier point in time, such as during the calibration phase. Accordingly, the device configured according to the first aspect of the invention can help verify the repeatability of the indexing position in which the first and second bodies are locked together.

[0007] The device can be configured to react in a predetermined manner based on the result of a comparison. For example, if the comparison result indicates that the first and second bodies are not properly locked together, the device can be configured to react by unlocking and relocking the first and second bodies at the same indexing position. Optionally, this may include relocking the first and second bodies from slightly different positions (e.g., from slightly different relative rotational orientations). Reacting in a predetermined manner may additionally or alternatively include recording and / or reporting (e.g., outputting to a controller device) error or warning status.

[0008] As will be understood, references to “previous measurement” and “previously locked at the graduation position” do not necessarily refer to the most recent or most recent measurements, or the most recent or most recent time they were locked at the graduation position. Rather, the terms “previous” and “previously” are used to mean at an earlier point in time. Accordingly, the first and second bodies may have been locked at the graduation position multiple times between the current time and the time the calibration information was obtained.

[0009] Preferably, the calibration information is obtained from at least one other measurement of the relative spatial configuration of the first body and the second body performed by the at least one verification sensor (when the first body and the second body are locked at the graduation position at an earlier time point).

[0010] The at least one verification sensor can be configured to measure the relative spatial configuration of the first and second bodies in only one dimension (e.g., at least two orthogonal dimensions, such as three orthogonal dimensions). The verification sensor can be configured to measure the relative height / space between the first and second bodies (e.g., along a rotation axis).

[0011] Optionally, the verification sensor can be configured to measure the relative configuration (e.g., lateral position and / or rotational orientation) of the first body and the second body in a plane perpendicular to the axis of rotation (i.e., the first axis). For example, the verification sensor can be configured to measure the relative lateral position of the first body and the second body (e.g., in at least one dimension perpendicular to the axis of rotation, such as in two orthogonal dimensions perpendicular to the axis of rotation). Optionally, the verification sensor can be configured to measure the relative rotational orientation of the first body and the second body about the first axis. Optionally, the at least one verification sensor can be configured to measure a combination of the above-described relative configurations.

[0012] As will be understood, the at least one verification sensor can be configured to provide a measurement of the relative configuration of the first and second bodies (in a plane perpendicular to the axis of rotation) at a resolution finer than the indexing increment of the engagement element, for example, at a resolution of at least 5 times, optionally at least 10 times, or, for example, at least 15 times, the indexing increment of the engagement element. Preferably, the verification sensor enables the establishment of the relative positions of the first and second bodies within 50 μm, for example, up to 10 μm, optionally up to 1 μm.

[0013] The device can be configured such that if a comparison result indicating that the current relative spatial configuration of the first and second bodies at the indexing position differs from the relative spatial configuration of the first and second bodies as indicated by calibration information by more than a predetermined threshold, it is determined that the first and second bodies are not properly locked together. The predetermined threshold may be no greater than 100 μm (micrometers), for example no greater than 50 μm, optionally no greater than 20 μm, but may be as small as no greater than 1 μm, for example no greater than 100 nm (nanometers), no greater than 50 nm, or no greater than 10 nm.

[0014] Preferably, the verification sensor includes an encoder device. The encoder device may include a rotating scale disposed on one of the first and second bodies, and at least one first reading head disposed on the other body for reading the rotating scale. Preferably, the encoder device of the verification sensor includes a second reading head configured to read the scale. Preferably, the second reading head is configured to read the scale at a position less than 180° from the position where the at least one first reading head reads the scale, for example, at a position between 45° and 135° from the position where the at least one first reading head reads the scale, and preferably at a position approximately 90° from the position where the at least one first reading head reads the scale. Accordingly, in embodiments where the verification sensor includes at least a first reading head and a second reading head, the device can be configured such that, when the first body and the second body are locked together at the graduation position, the first reading head and the second reading head are used to read the scale, and a first reading and a second reading obtained from the first reading head and the second reading head respectively are compared with corresponding first readings and second readings obtained by the first reading head and the second reading head when the first body and the second body are locked at the graduation position at an earlier time point, in order to establish information about the engagement state of the first body and the second body.

[0015] The encoder device for verifying the sensor may include an incremental encoder device comprising an incremental scale having a series of periodic scale features. In particular, the encoder device for verifying the sensor may include an optical encoder device.

[0016] The engaging elements of the first body and the second body can be disengaged by axial relative movement of the first body and the second body along the first axis in a first direction, such that the first body and the second body can be unlocked and rotated relative to each other about the first axis, and can be re-engaged by axial relative movement of the first body and the second body along the axis in a second direction.

[0017] The device may further include a motor for driving the first and second bodies about the first axis when the first and second bodies are unlocked.

[0018] The device may further include a main encoder device configured to monitor the relative rotational position of the first and second bodies about a first axis when the first and second bodies are unlocked. Optionally, this may be the same encoder device as the encoder device of the verification sensor. Optionally, the main encoder device may share some common parts with the encoder device of the verification sensor (e.g., they may share the same scale, wherein the main encoder device includes a readhead different from that of the verification sensor). However, it is preferable that the main encoder device is a completely different encoder device from the encoder device of the verification sensor, including a different readhead and a different scale.

[0019] The device may include a motor mechanism (“lock / unlock” motor mechanism) for actuating a first body and a second body between their locked and / or unlocked states. The lock / unlock motor mechanism may include a member (e.g., a strut) that can be actuated by a motor to disengage interlocking elements of the first and second bodies along a first axis. For example, the strut may be actuated between a retracted configuration in which the first and second bodies are in their locked state, and in an extended configuration in which the first and second bodies are held apart by the strut along the first axis, such that the interlocking elements are unlocked, thereby allowing relative rotation of the first and second bodies. For example, the first body may include the strut, and the strut and the second body may be magnetically biased toward each other to magnetically hold the first and second bodies. A supplementary biasing member (e.g., a magnetic material) may be configured to bias the strut toward its retracted configuration.

[0020] For example, the first body may include a component (e.g., a strut) that is rotatable relative to the first body about a first axis, at least in an unlocked configuration, and is configured to engage the second body and be fixed relative to the second body in a rotational sense when the first and second bodies are unlocked and rotated relative to each other (so that the relative rotational position of the first and second bodies about the first axis can be determined). The component may be actuated (e.g., by a motor) between a retracted configuration and an extended configuration, in which the first and second bodies are in their locked state, and in which the first and second bodies are held apart by the component / strut along the first axis in an extended configuration, thereby unlocking the first and second bodies and allowing relative rotation. A master encoder device may include a readhead on one of the first body and the component and a scale on the other, such that the readhead provides a measurement of the relative rotational position of the first body and the component. The device may be configured to use the output of the master encoder device to control the rotation of the first and second bodies when the first and second bodies are unlocked. The strut can be coupled to the second body when it is in its extended configuration (e.g., via a corresponding engagement feature described in more detail below), and disengaged from the second body when it is in its retracted configuration.

[0021] The metrology equipment may include a rotary table with an indexing hinge joint, on which the workpiece to be inspected is mounted. The metrology equipment may include a probe head with an indexing hinge joint. The probe head may be configured to support the measuring probe on a coordinate positioning device, such that the measuring probe can be arranged in multiple different indexing rotation orientations. Suitable measuring probes include contact and non-contact measuring probes. Suitable measuring probes include probes for measuring the dimensions of workpieces. Suitable measuring probes include touch-triggered measuring probes as well as scanning or “analog” measuring probes.

[0022] The measuring device (e.g., a rotary table / probe head) can be configured to be mounted on a positioning device, particularly a coordinate positioning device, such as a coordinate measuring machine (CMM). The measuring device (e.g., a rotary table / probe head) can be mounted on a positioning device configured to facilitate repositioning of the measuring device in at least two, for example, three orthogonal linear degrees of freedom. The measuring device (e.g., a rotary table / probe head) can be removably mounted to the positioning device (e.g., to the z-column or sleeve shaft of the CMM) via one or more releasable fasteners (e.g., one or more bolts).

[0023] The device may include a memory device containing calibration information. The memory device may be located in a portion of the device separate from the indexing articulated joint (e.g., within a controller). Preferably, a portion of the indexing articulated joint (e.g., a first body or a second body) includes the memory device. In embodiments where the device includes a probe head (or rotary table), the probe head (or rotary table) may include the memory device.

[0024] The device may include a processing unit configured to perform the comparisons described above. This processing unit may be located in a portion of the device separate from the indexing articulated joint (e.g., within a controller). Optionally, a portion of the indexing articulated joint (e.g., a first body or a second body) includes the processing unit. In embodiments where the device includes a probe head (or a rotary table), the probe head (or rotary table) may include the processing unit.

[0025] Accordingly, the device can be configured to perform the above comparison within a portion of the metrology equipment, including the indexing articulated joint itself (e.g., within the probe head or rotary table).

[0026] Calibration information can be stored in a lookup table. Optionally, calibration information can be represented by a function. Accordingly, the aforementioned memory device may include a lookup table and / or a function containing / representing calibration information. The lookup table may include calibration information for each possible graduation position in at least a subset of the possible graduation positions of the first and second bodies. The lookup table may include calibration information for each possible graduation position of the first and second bodies. For example, the lookup table may include at least one element / data unit for each graduation position. Each element / data unit may include calibration information for the graduation position associated with that element / data unit. The lookup table may include multiple elements / data units for each graduation position. This may be helpful when there is more than one verification sensor or when the verification sensor can provide multiple outputs / readings / measurements for the relative position of the first and second bodies (e.g., according to the embodiments of the verification sensor of the encoder device including at least two readheads described above and below).

[0027] "Information obtained from the measurement" and "calibration information" may include relative position information (e.g., relative to absolute position information).

[0028] As described above, the verification sensor may include an encoder device (e.g., a scale on one of the first and second bodies and one or more readheads on the other body, the readheads outputting signals dependent on the relative positions of the scale and the readheads). As will be understood, the scale may include a series of features, such as a series of generally periodic features. The scale may have a characteristic pitch distance (or, for some rotating systems, a “characteristic pitch angle,” such as a disc scale with features radially arranged on it). The readhead signal may also be used to interpolate between scale pitch intervals to produce position measurements with a much higher resolution than the scale pitch. (There are cases where the readhead generates spatially periodic signals, and in some embodiments, the readhead signal period has a higher frequency (shorter wavelength) than the scale period. In these cases, interpolation can still be used to produce position measurements with a much higher resolution than the signal period). Accordingly, “information obtained from the measurement” and “calibration information” may include relative position information with a resolution much finer than the scale period. This relative position information may be referred to as a “phase reading” because it relates to the “phase” position between the periodic features of the scale. Accordingly, the "information obtained from the measurement" and the "calibration information" may include phase readings. Accordingly, in such an embodiment, the device may be configured such that, when the first and second bodies are locked together at the graduation position, a reading head mounted on one of the first and second bodies is configured to read a scale mounted on the other body and compare the phase reading obtained therefrom with a phase reading obtained by the reading head when the first and second bodies were locked at the graduation position at an earlier time point, in order to establish information about the engagement state of the first and second bodies.

[0029] Accordingly, in embodiments where the verification sensor includes at least a first reading head and a second reading head, the device can be configured such that, when the first body and the second body are locked together at the indexing position, the first reading head and the second reading head are configured to read the scale, and compare the first phase reading and the second phase reading obtained from the first reading head and the second reading head respectively with the corresponding first reading and the second reading obtained by the first reading head and the second reading head when the first body and the second body were locked at the indexing position at an earlier time point, in order to establish information about the engagement state of the first body and the second body.

[0030] Calibration information (e.g., lookup tables or functions) can be updated over time. This can occur continuously or periodically. It can be done as part of a dedicated calibration process or during a measurement operation. For example, each time the first and second bodies lock together at any given graduation position and a comparison indicates that the first and second bodies have been correctly locked together (e.g., the comparison indicates that the current relative spatial configuration of the first and second bodies at that graduation position differs from the relative spatial configuration of the first and second bodies as indicated by the calibration information by no more than a predetermined threshold), information obtained from measurements of the current relative spatial configuration of the first and second bodies provided by a verification sensor, and readings output by the first readhead 160 and the second readhead (not shown), can be used to update (e.g., can be stored) the calibration information (e.g., can be used to update / replace information stored in a lookup table associated with that graduation position).

[0031] As will be understood, "information obtained from the measurement" can refer to information obtained from measurement results acquired by the verification sensor itself, or it can refer to information obtained from measurement results acquired by the verification sensor as well as from other data sources. Accordingly, the information is not necessarily obtained / derived from or solely from measurement results acquired by the verification sensor. However, it is preferable that "information derived at least from the current measurement" is solely from measurement results acquired by the verification sensor. Accordingly, "information obtained from the measurement" can be measurement results acquired by the verification sensor, for example, it can be solely from the output of the verification sensor.

[0032] Similarly, "calibration information obtained from at least one other / previous measurement of the relative spatial configuration of the first and second bodies" can refer to calibration information obtained from at least one other / previous measurement result obtained by the verification sensor itself, or it can refer to calibration information obtained from at least one other / previous measurement result obtained by the verification sensor as well as from other data sources. Accordingly, calibration information is not necessarily obtained / derived from or solely from at least one other / previous measurement result obtained by the verification sensor. However, it is preferable that the "calibration information" is only a measurement result obtained by the verification sensor at an earlier point in time. Accordingly, the "calibration information" can be a measurement result obtained by the verification sensor, for example, it can be solely from the output of the verification sensor.

[0033] Accordingly, the device can be configured to compare the current measurement of the relative spatial configuration of the first body and the second body obtained by the verification sensor with other / previous measurements of the relative spatial configuration of the first body and the second body taken by the verification sensor when the first body and the second body were locked at the indexing position at an earlier time point, in order to establish information about the engagement state of the first body and the second body.

[0034] As will be understood, such interlocking engagement elements can provide a plurality of predetermined angular indexing positions in which the first and second bodies can be locked relative to each other. The interlocking engagement elements / indexing mechanisms can provide indexing increments of 10° or less, such as 5° or less, for example, 4° or less. The interlocking engagement elements / indexing mechanisms can provide indexing increments of at least 0.5°, for example, at least 1°. For example, the interlocking engagement elements / indexing mechanisms can provide indexing increments of about 2.5°.

[0035] The device may include a motor (“reorientation” motor mechanism) configured to drive the first and second bodies about a rotation axis (first axis) when the first and second bodies are unlocked.

[0036] As will be understood, the interlocking engagement elements / indexing mechanism may include two sets of interlocking components / features, one set on each of the first and second bodies. The interlocking engagement elements / indexing mechanism may include, for example, a series of annular features on one of the first and second bodies (e.g., on the first body), such as a series of balls or a series of conical teeth (e.g., thus providing a face spline component). The other body of the first and second bodies (e.g., the second body) may also include a series of annular features, but preferably, the engagement elements of the other body (e.g., the second body) are configured such that, when locked, they engage only at a subset of the tooth series of the annular features on said one of the first and second bodies (e.g., on the first body) at a plurality of discrete, annularly spaced locations. The device may be configured such that, when locked (and for each possible indexing position), the engagement elements disposed on the other body of the first and second bodies engage with a subset of the tooth series of said one of the first and second bodies at three discrete, equiangularly spaced locations.

[0037] The device can be configured such that, when locked (and for each possible indexing position), engaging elements provide kinematic mounting / positioning / connection between the first and second bodies. As will be understood, a kinematic mount is a type of mount having elements on one portion arranged to cooperate with elements on another portion to provide highly repeatable positioning. These elements are arranged to cooperate with each other to constrain relative motion between these portions, preferably by six contact points or constraint points, in all six degrees of freedom (i.e., three vertical linear degrees of freedom and three vertical rotational degrees of freedom). In a particular embodiment, the elements on one of these portions may be arranged to provide a pair of converging surfaces at each of three spaced locations, thus providing a total of six contact points with elements on the other portion. This restricts six possible degrees of freedom of one portion relative to the other. Such kinematic mounts are sometimes referred to as Boys' supports and are described, for example, in H.J. Braddick's "Mechanical Design of Laboratory Apparatus," Chapman and Hall, London, 1960, pp. 11–30. Further details are provided below for example configurations used to provide this kinematic mounting / positioning / connection.

[0038] The device may include a third body, wherein the third body and one of the first and second bodies have interlocking engagement elements that can be locked together with respect to a second axis at multiple different angular orientations to provide multiple angularly graduated positions in which the third body and the first or second body can be locked relative to each other. The features described above in conjunction with the first and second bodies also apply to the third body and to which the third body can be reoriented and mounted via the interlocking engagement elements. Accordingly, at least one verification sensor can be provided, configured to provide a measurement of the relative spatial configuration of the third body and the first or second body to which the third body can be reoriented via the interlocking engagement element, and the device can be configured such that, when the third body and the first or second body are locked together at an indexing position, the verification sensor is used to measure the relative spatial configuration of the third body and the first or second body, and wherein the information obtained from the measurement is compared with calibration information obtained from at least one other / previous measurement of the relative spatial configuration of the third body and the first or second body performed by the verification sensor when the third body and the first or second body were locked at the indexing position at an earlier time point, in order to establish information about the engagement state of the third body and the first or second body.

[0039] According to another aspect of the invention, a metrological device is provided including a graduated hinge joint, the graduated hinge joint comprising: a first body and a second body, the first body and the second body each having engaging elements that can be locked together about a first axis at multiple different angular orientations to provide multiple angular graduation positions in which the first body and the second body can be locked relative to each other; at least one verification sensor configured to provide an output that depends on the relative spatial configuration of the first body and the second body in their locked state; and a memory device containing predetermined calibration information obtained from the output of the at least one verification sensor for each graduation position in at least one subset of the graduation positions.

[0040] According to another aspect of the invention, a metrological device is provided including an indexing articulated joint comprising: a first body and a second body, the first body and the second body each having engaging elements that can be locked together about a first axis at multiple different angular orientations to provide multiple angular indexing positions in which the first body and the second body can be locked relative to each other; the engaging elements of the first body and the second body are disengaged by axial relative movement of the first body and the second body along the first axis in a first direction, such that the first body and the second body can be unlocked and rotated relative to each other about the first axis, and can be re-engaged by axial relative movement of the first body and the second body along the axis in a second direction, such that the first body and the second body can be locked in a new indexing position; the indexing articulated probe head further includes at least one verification sensor configured to measure and provide information depending on the relative spatial configuration of the first body and the second body in their locked state, and wherein the device is configured to compare at least the information derived from the verification sensor with predetermined information associated with a particular indexing position in which they are locked, and to react according to the result of the comparison.

[0041] Embodiments of the invention will now be described by way of example only with reference to the following accompanying drawings, in which:

[0042] Figure 1 An indexing head according to the invention, mounted on a coordinate measuring machine (CMM), is shown;

[0043] Figure 2 Shown separately Figure 1 Indexing head;

[0044] Figure 3 Showing Figure 1 A cross-sectional view of the indexing head in its locked configuration;

[0045] Figure 4 Showing Figure 1 A cross-sectional view of the indexing head in its unlocked configuration;

[0046] Figure 5a Showing Figure 1 The indexing mechanism of the indexing head;

[0047] Figure 5b Shown separately Figure 5a A part of the indexing mechanism;

[0048] Figure 6 yes Figure 5a Detailed view of the indexing mechanism shown;

[0049] Figure 7a , Figure 7b and Figure 7c Showing Figure 5b A single tooth of this part of the indexing mechanism shown;

[0050] Figure 8 yes Figure 1 An exploded view of the different parts of the indexing mechanism and unlocking mechanism of the indexing head.

[0051] Figure 9 and Figure 10a It shows Figure 1 Cross-sectional views of different parts of the indexing mechanism and unlocking mechanism of the indexing head;

[0052] Figure 10b It shows Figure 1 The bottom side of one of the hinged parts of the indexing mechanism of the indexing head;

[0053] Figures 11a to 11d It shows Figure 1 Schematic cross-sectional view of different parts of the indexing mechanism and unlocking mechanism of the indexing head at different stages during the unlocking and locking operations;

[0054] Figures 12 to 15 A schematic cross-sectional view of the indexing mechanism and unlocking mechanism according to alternative embodiments is shown, particularly of different portions with different magnet arrangements;

[0055] Figure 16 It is for display purposes Figure 3 , Figure 4 The graphs of support force and holding force of the three ring magnet embodiments shown in Figure 11;

[0056] Figure 17 It is for display purposes Figure 12 The graphs of the strut force and holding force of two embodiments of the ring magnet; and

[0057] Figure 18 It is a graph showing the strut force and starting torque of an embodiment using two disk magnets.

[0058] refer to Figure 1 The diagram shows a hinge joint 100 according to the invention mounted on a positioning device 200.

[0059] The positioning device 200 includes a moving structure, in this case, in the form of a coordinate measuring machine (“CMM”). The CMM 200 includes a base 202 supporting a frame 204, which in turn holds a bracket 206, which in turn holds a sleeve shaft 208 (or “Z-column”). A motor (not shown) is provided to move the sleeve shaft 208 along three mutually orthogonal axes X, Y, and Z (e.g., by moving the frame along the Y-axis, moving the bracket 206 along the X-axis, and moving the sleeve shaft 208 along the Z-axis).

[0060] The sleeve shaft 208 holds the hinge joint 100, which in turn holds the probe 300. In this embodiment, the hinge joint 100 facilitates the repositioning of the probe 300 mounted thereon about the first axis of rotation D and the second axis of rotation E, as explained in more detail below.

[0061] The combination of the two rotational axes (D, E) provided by the hinge joint 100 and the three linear translational axes (X, Y, Z) of the CMM 200 allows the probe 300 to move / position in five degrees of freedom (two rotational degrees of freedom and three linear degrees of freedom).

[0062] Although not shown, a measuring encoder may be provided for measuring the relative positions of the base 202, frame 204, bracket 206, sleeve shaft 208 and hinge joint 100, thereby determining the position of the measuring probe 300 relative to the workpiece located on the base 202.

[0063] A controller 220 is provided for controlling the operation of the CMM 200, such as controlling the position and orientation of the probe 300 within the CMM volume (manually, e.g., via an input device, such as a joystick 216; or automatically, e.g., under the control of an inspection procedure) and receiving information (e.g., measurement information) from the CMM 200. A display device 218 may be provided to assist the user in interacting with the controller 220. The controller 220 may be, for example, a dedicated electronic control system and / or may include a personal computer.

[0064] In the illustrated embodiment, probe 300 is a contact probe comprising a probe body 302 and a stylus 304. The stylus 304 has a spherical end 306 for contacting the workpiece to be inspected, and in this embodiment, the stylus 304 is deflectable relative to the probe body 302. The contact probe 300 may be a probe commonly referred to as a contact-triggered probe, or it may be a scanning (or analog) probe. As will be understood, other types of probes, including non-contact probes, may also be mounted on the hinge joint 100.

[0065] In the current embodiment, the hinge joint 100 includes a probe mount 108 to facilitate the changing of different probes thereon. Specifically, this can be a mount that facilitates the automatic changing of probes to or from a rack within the operating volume of the CMM. For example, the probe mount 108 and the probe body 302 may include magnets for holding the probe on the mount.

[0066] The hinge joint 100 may include built-in sensor components for detecting the deflection of the stylus 304 of the contact probe mounted thereon. However, in this embodiment, all such sensor components are housed within the body 302 of the probe 300 itself. The probe 300 is configured to send a stylus deflection signal to the controller 220. As is common practice, this is accomplished via a contact signal interface between the probe 300 and the probe mount 108, where such signals are then relayed to the controller 220 via wiring between the hinge joint 100 and the CMM 200. Such an interface can also be used to power the probe 300. Accordingly, as will be understood, the hinge joint 100 itself will have a signal interface with the sleeve shaft 208, which can be used to relay probe signals and receive power and motor control commands for controlling the hinge joint 100.

[0067] Now for reference Figures 2 to 18 The hinge joint 100 will now be described in more detail.

[0068] like Figure 2 As shown, the hinge joint 100 includes a first member 102 or "mounting plate", a second member 104 hinged / rotatable relative to the first member 102 about a first axis of rotation "D", and a third member 106 hinged / rotatable relative to the second member 104 about a second axis of rotation "E". The second axis of rotation "E" is orthogonal to the first axis of rotation "D". In the described embodiment, the first axis of rotation "D" is arranged parallel to the Z-axis of the CMM, but this is not necessarily the case.

[0069] The first component / mounting plate 102 includes holes 103 through which bolts can pass to fasten the hinge 100 to the sleeve shaft 208 of the CMM 200. The third component 106 includes a probe mount 108 on which a probe (e.g., a contact probe 300) can be interchangeably mounted.

[0070] In alternative embodiments, the third member 106 may be an interchangeable member. For example, the third member 106 may be configured as part of the probe rather than as part of the hinge 100, such that it can be (e.g., automatically) interchanged with the probe. In this case, the hinge 100 may include a mounting member 106' for the third member 106, which is hinged / rotatable relative to the second member 104 about a second axis of rotation "E". The mounting member 106' and the third member 106 may be provided with cooperating mounting features to allow the third member 106 to be detachably mounted to the mounting member 106'. For example, such cooperating mounting features may include features defining a kinematic mounting seat. One or more magnets may be provided to hold the third member 106 on the mounting member 106'.

[0071] Figure 3 and Figure 4 A cross-sectional view of the hinge joint 100 taken along the ZY plane is shown. Figure 3 and Figure 4 They are essentially the same and are common views of the same hinge joint, but in Figure 3 The diagram shows the hinge 100 when the first component / mounting plate 102 and the second body 105 are in their locked state, while... Figure 4 The diagram shows the hinge 100 when the first component / mounting plate 102 and the second body 105 are in their unlocked state.

[0072] Figure 4 Many reference numerals have been omitted from the accompanying drawings to aid in observing the various features of the hinge joint 100.

[0073] The locking / unlocking, rotation, and indexing mechanism of the first axis "D" (i.e., the first component / mounting plate 102 and the second component 104) will now be explained. In this embodiment, the locking / unlocking and indexing mechanism of the second axis "E" (i.e., the second component 104 and the third component 106) is substantially the same (but arranged perpendicular to the locking / unlocking and indexing mechanism of the first axis "D"), and therefore will not be described in detail again, and only some parts thereof will be discussed. Figure 3 and Figure 4 The diagram is shown schematically (and is labeled with the same reference numerals followed by an apostrophe ').

[0074] The indexing mechanism of the first axis "D" includes an arrangement of interlocking engagement elements disposed on the first member / mount plate 102 and the second member 104. Specifically, a first annular member 110 with a series of continuous conical teeth 112 is provided (see, for example, detailed views). Figure 5a and Figure 6 The teeth 112 extend substantially radially, as their extent extends primarily along the radial direction (relative to the radius of the first annular member; also relative to the first axis "D"). Accordingly, in this embodiment, the first annular member 110 is in the form of an "end-face spline member," and will be referred to thereafter as such (note in particular that, in the described embodiment, the end-face spline member has the configuration of an end-face toothed joint member). The teeth of the end-face spline member 110 are radially elongated and have a generally tapered cross-sectional profile (cut perpendicular to its length). In this embodiment, each side 111 of the teeth 112 is substantially flat / planar, although this is not necessarily the case (e.g., they can be curved or crown-shaped, such as the crown tooth 118 described below).

[0075] The indexing mechanism / interlocking engagement element further includes a second annular member 114, which is characterized by being configured to mesh with the teeth 112 of the end face spline member 110. The second annular member 114 is characterized by being configured to engage only a subset of a continuous series of teeth provided on the end face spline member 110 (see detailed view). Figure 5b and Figure 6 Accordingly, instead of providing a series of continuously engaging teeth, the second annular member 114 includes only features configured to engage with the teeth 112 of the end face spline member 110 at three discrete, equiangularly spaced (120°) locations 116. In this specific embodiment, at each of the locations 116, only a single feature in the form of a crown tooth 118 is provided. Each crown tooth 118 is radially elongated and has a generally tapered profile (cut perpendicular to its length) and thereby provides two curved engagement side surfaces 120 configured to engage the side surfaces 111 of the teeth 112 on the end face spline member 110.

[0076] like Figures 7a to 7c As shown, the engagement side surface 120 of the crown tooth 118 extends along its length (in this embodiment along the radial dimension, or along the X-axis, as shown in the figure). Figure 7a and Figure 7c As shown) and in their cross-sectional profiles (perpendicular to their length / radial dimension, such as Figure 7bThe crown tooth 118 (as shown) bends in the face spline member 110. This configuration (i.e., the crown tooth 118 engaging with the flat / planar tooth 112 on the face spline member 110) ensures that each engaging side surface 120 of the crown tooth 118 presents a vertex region 122. It is this vertex region 122 that will tend to engage with the side surface 111 of the tooth 112 on the face spline member 110. It has been found that providing a vertex region will provide a more repeatable placement position between the first annular member / face spline member 110 and the second annular member 114. This is because providing vertex region 112 means that for any given tooth pair on the first annular member / end-face spline member 110 and the second annular member 114, it is significantly more likely that the teeth in the pair will engage at the same area on their side surfaces 111, 120 each time they come together (compared to the case where the side surfaces 111, 120 of the teeth on both the first annular member / end-face spline member 110 and the second annular member 114 are substantially flat / planar), thereby helping to ensure that the first annular member / end-face spline member 110 and the second annular member 114 are positioned together in the same location each time they come together at a given angular orientation. In particular, this configuration helps to provide kinematic connection between the first annular member / end-face spline member 110 and the second annular member 114.

[0077] Furthermore, when the indexing increment becomes small (e.g., less than 7.5°, and particularly less than 5°, such as close to 2.5°), the described configuration has been found to be significantly superior to the ball and roller indexing mechanism described in WO 2006 / 079794. This is because the smaller the indexing increment, the smaller the intermeshing characteristics. Not only may it be difficult to accurately manufacture and assemble a ring of balls with a much smaller diameter, but the Hertzian contact pressure will be extremely high due to the very small contact point between the very small-diameter balls and the corresponding rollers, causing them to bear excessive pressure, which in turn will lead to excessive wear and / or failure of the indexing mechanism.

[0078] For example, in the embodiment described herein, the first annular member / end-face spline member 110 and the second annular member 114 have an outer diameter of 75 mm and are provided with teeth sized to provide 2.5° indexing increments, and the hinge joint 100 is configured such that when in the locked position, the first annular member / end-face spline member 110 and the second annular member 114 will be held together by a force of approximately 120 N (Newtons). The crown teeth are in a plane perpendicular to their length (e.g., in…) Figure 7b The radius of curvature R' intercepted in the ZY plane is 1.8 mm, and the coronal tooth is in a plane along its length (e.g., in the ZY plane). Figure 7cThe radius of curvature R” intercepted in the ZX plane is 23 mm. In contrast, if spherical balls are used instead of crown teeth, the balls would have to have a radius of curvature of <0.75 mm to fit between the teeth 112 of the first annular member / end face spline member. Not only would it be difficult to assemble such small balls into the hinge joint, but they would also provide very small contact points, resulting in extremely high Hertzian contact pressure.

[0079] As will be understood, the same effect can be achieved by making the teeth 112 on the first annular member / end-face spline member 110 crown-shaped and providing teeth 118 with flat sides on the second annular member 114, although this may be more difficult to manufacture. Alternatively, the teeth 112, 118 on the first annular member / end-face spline member 110 and the second annular member 114 can both be crown-shaped, but with the increase in manufacturing difficulty, the tooth dimensions will need to be adjusted (especially increased) to avoid undesirable Hertzian contact pressure.

[0080] The mechanism for locking and unlocking the indexing mechanism of the first axis "D" will now be described. In summary, in the specific embodiment described, the locking / unlocking mechanism relies solely on a magnet to provide the retaining force between the first annular member / end-face spline member 110 and the second annular member 114 having crown teeth 118, and uses a motor-driven actuator to push the first member / mount plate 102 and the second member 104 away from each other to separate the first annular member / end-face spline member 110 and the second annular member 114 having crown teeth 118. This mechanism will now be described in more detail.

[0081] In the described embodiment, the locking / unlocking mechanism comprises a set of three stacked magnets. Specifically, a first ring magnet 140 is disposed on the top surface 115 of the housing 105 of the second member 104, a second ring magnet 142 is disposed on the contact plate 134 of the support post 130 (described in more detail below), and a third magnet 144 is disposed on the first member / mounting plate 102. The first ring magnet 140, the second ring magnet 142, and the third ring magnet 144 are identical in shape and size, stacked coaxially with each other, and arranged such that both the first ring magnet 140 and the third ring magnet 144 attract the second magnet 142 sandwiched between them. The magnetic poles of the ring magnets are axially arranged (i.e., such that two magnetic poles are located on the top and bottom of the flat surface of the ring). In particular, the ring magnets are configured such that the north pole of the first magnet 140 faces the south pole of the second magnet 142, and the north pole of the second magnet 142 faces the south pole of the third magnet 144. As explained in more detail below, when in the locked and unlocked positions, the second member 104 is held solely by magnetic attraction, and in particular solely by magnetic attraction between the third magnet 144, the second magnet 142, and the first magnet 140.

[0082] The locking / unlocking mechanism includes a strut 130 comprising a shaft 132 and a "head" or "contact plate" 134. The shaft 132 of the strut 130 is supported within a linear cylindrical bearing housing 107 provided by a top surface 115 member of the housing 105 of the second member 104. Bearings (in this case, an array of ball bearings 109) are disposed between the shaft 132 and the cylindrical bearing housing 107 to facilitate relative linear and rotational movement (i.e., along and about the first axis "D") between the shaft 132 and the cylindrical bearing housing 107. The contact plate 134 includes a radially extending surface sandwiched between the body of the first member / mount plate 102 and the body of the second member 104.

[0083] A motor-driven lever 170 is provided to achieve the linear / axial movement of shaft 132 along the first axis "D". Lever 170 is pivotally mounted at its first end to a flexure 178, which is anchored via a mounting block 179 to the housing 105 of the second member (anchored to a top plate 115 in this embodiment). Lever 170 is attached at its second end to a lead screw mechanism 172, which is configured to raise and lower the second end of lever 170. The lever is attached at a point between its first and second ends via a spool 146 to the end of shaft 132 remote from contact plate 134 (this facilitates relative rotation of shaft 132 and lever 170). A motor (not shown) is configured to drive lead screw mechanism 172. Specifically, a motor (not shown) is configured to rotate the lead screw 174 via a drive gear 173, which, upon rotation, causes a nut 176 (attached to a lever 170 via a pin 175) to travel axially along the lead screw 174. The lead screw 174 is also anchored to the housing 105 of the second component (in this embodiment, to a cylindrical bearing housing 107) via a mounting bracket 177 and a bearing 179, such that the lead screw can rotate about its axis of rotation, but is fixed relative to the housing 105 of the second component in the Z dimension (e.g., ...). Figure 3 and Figure 4 (As shown).

[0084] It may be advantageous that the drive mechanism for the strut 130 resists reverse drive (in other words, it is not easily reversed manually), especially if the three-magnet design described below is not employed. This is because, if the net external force on the strut 130 is sufficiently low, a drive mechanism that is not easily reversed manually will tend to maintain its position, even when the motor / power supply is not activated. This avoids the need for a servo drive mechanism / motor to maintain a fixed position and thus reduces the power consumption of the articulation. Consequently, this reduces the heat generated by the drive mechanism / motor, which in turn improves the metering performance of the articulation by reducing thermal deformation. A lead screw mechanism with a high gear pitch is an example of a drive mechanism that is not easily reversed.

[0085] As explained in more detail below, a second motor (not shown) with gears is provided, which is configured to engage a drive gear 148 disposed on shaft 132 and drive the drive gear toward the end of the shaft remote from contact plate 134, and can be operated to rotate / spin the housing 105 of the first member 104 (and everything anchored to it) about the first axis “D” about shaft 132. A first (or “master”) rotary encoder device 135 (e.g., a magnetic absolute rotary encoder device) is provided to monitor the relative angular position of the housing 105 of the first member 104 and shaft 132 about the first axis “D”.

[0086] The contact plate 134 of the strut and the first component / mounting plate 102 have corresponding engagement elements. Specifically, the corresponding engagement elements include features configured to provide a repeatable, particularly kinematic, connection between the contact plate 134 of the strut and the first component / mounting plate 102 upon engagement. In the described embodiment, the contact plate 134 of the strut includes three engagement balls 152 positioned 120° apart from each other, and the first component / mounting plate 102 has three pairs of engagement balls 154 positioned 120° apart from each other (see [link to documentation]). Figure 10b Each pair of engagement balls 154 on the first component / mounting plate 102 defines a channel or groove for receiving one of the engagement balls 152 located on the contact plate 134.

[0087] For example Figure 3 and Figure 4 As shown, a second rotary encoder device is provided, comprising an annular scale 162 disposed on the bottom side of the first component / mounting plate 102 and a first read head 160 and a second read head (not shown) disposed on the top surface 115 of the housing 105 of the second component 104 (although, as will be understood, they may be arranged in reverse order). In the described embodiment, the first read head 160 and the second read head (not shown) are circumferentially spaced 90° apart from each other. In the described embodiment, the second rotary encoder device is an incremental optical rotary encoder device. In a particular embodiment described, the second encoder device is a high-resolution encoder that enables the establishment of the relative positions of the bodies 105 of the first component / mounting plate 102 and the second component 104 within 10 nm (nanometers). Its purpose will be described in more detail later in this document.

[0088] The unlocking / reorientation / locking process of the first component / mounting plate 102 and the second component 104 will now be described. Figure 3The first component / mounting plate 102 and the second component 104 are shown in a locked state. In the locked state, the probe 300 mounted on the probe mount 108 can be held in a stable and defined angular position, making it usable for inspecting articles during measurement operations. However, it may be desirable to reorient the probe mounted on the probe mount 108, for example, for tactile reasons. For this, it will be necessary to unlock the first component / mounting plate 102 and the second component 104, reorient them relative to each other, and then lock them together in the new orientation.

[0089] Unlocking the first component / mounting plate 102 and the second component 104 involves axially driving the strut 130 along the first axis "D" toward the first component / mounting plate 102. In the described embodiment, this is achieved by operating a motor (not shown) to drive the lead screw 174 upward in the Z dimension to drive the lead screw nut 176 (in) Figure 3 and Figure 4 (As shown in the orientation). After a short distance, the engagement ball 152 on the contact plate 134 will contact and engage the paired engagement ball 154 on the first component / mounting plate 102. Continued actuation of the lead screw 174 will cause the lever 170 and the lead screw mechanism 172 to push the housing 105 (to which the cylindrical bearing housing 107 is anchored via the lead screw 174) axially downwards, thereby causing the housing 105 of the second component 104 to separate from the first component / mounting plate 102. The lead screw 174 is operated to separate the second component 104 and the first component / mounting plate 102 by a controlled, predetermined amount sufficient to disengage the crown tooth 118 from the tooth 112, but not too large, as it is expected that the first magnet 140 will remain sufficiently close to the second magnet to exert a reasonable amount of pull on the second magnet 142 even in the unlocked state. Figure 4 The indexing head 100 is shown in this unlocked state.

[0090] When in the unlocked state, the motor (not shown) driving the lead screw mechanism 172 stops, and the motor (not shown) engaging with the drive gear 148 of shaft 132 operates to change the rotational position of the second member 105 of the hinge joint 100. As described above, in the unlocked state, the support 130 engages with the first member / mounting plate 102 via engagement balls 152, 154, and is therefore fixed relative to it in a rotational sense (in the unlocked state). Accordingly, when the motor (not shown) engaging with the drive gear 148 of shaft 132 operates, it causes the entire housing 105, 107, 115 of the second member 104 (and all parts anchored thereto, including the aforementioned motor) to be driven about shaft 132, and thus causes the entire housing 105, 107, 115 of the second member 104 (and all parts anchored thereto) to rotate about the first axis "D".

[0091] The relative rotational positions of i) the housings 105, 107, and 115 of the second member 104 and ii) the shaft 132 (and thus the first member / mount plate 102) are known from the first (“master”) encoder device 135. Accordingly, the controller 220 can use the output from the first encoder device 135 to control a motor (not shown) engaged with the drive gear 148 of the shaft, thereby bringing the first member / mount plate 102 and the second member 104 to the desired relative orientation. As will be understood, the rotational position needs to be controlled with sufficiently high precision such that, when in the new desired relative orientation, the crown tooth 118 on the second annular member 114 is valley-aligned with the tooth 112 on the first annular member / end-face spline member 110, such that when they are locked together, the crown tooth 118 is perfectly positioned between the two teeth 112 of the first annular member / end-face spline member 110.

[0092] The process of locking the first component / mounting plate 102 and the second component 104 will now be described. In the described embodiment, this is achieved as follows: an actuating motor (not shown) drives the lead screw 174 to drive the lead screw nut 176 downward. Figure 3 and Figure 4 (As shown in the orientation). This will cause the housing 105 of the second member 104 to be pulled upward toward the first member / mounting plate 102 until the crown teeth 118 on the second annular member 114 engage the teeth 112 of the end face spline member 110. Continued operation of the motor thereafter will cause the strut 130 to retract away from the first member / mounting plate 102, thereby disengaging the engagement balls 152, 154 disposed on the contact plate 134 and the first member / mounting plate 102. Accordingly, at the disengagement point of the engagement balls 152, 154, the first member / mounting plate 102 and the second member 104 are held by kinematic constraints provided by six contact points between the three crown teeth 118 and the teeth 112 of the first annular member / end face spline member 110.

[0093] Reference Figures 11a to 11d The figures depict the interaction between the first magnet 140, the second magnet 142, and the third magnet 144. These figures schematically show the shaft 132 and contact plate 134 of the support, the top plate 115 of the second component, the first component / mounting plate 102, the second annular component 114 (which has three crown teeth 118), the first annular component / end face spline component 110 (which has a continuous series of teeth 112), and the first annular magnet 140, the second annular magnet 142, and the third annular magnet 144. Figure 11a The first component / mounting plate 102 and the second component 104 are shown in the locked position; that is, at this time, the teeth 112 on the first annular component / end face spline component 110 are fully engaged with the teeth 118 on the second annular component 114. Figure 11b The first component / mounting plate 102 and the second component 104 are shown in the locked position, but at this time the support 130 has been actuated to the point that the engagement ball 152 on the contact plate 134 has engaged the engagement ball 154 on the first component / mounting plate 102 and is about to begin separating the tooth 112 on the first annular component / end face spline component 110 from the tooth 118 on the second annular component 114. Figure 11c The first component / mounting plate 102 and the second component 104 are shown, where they have begun to separate but have not yet reached their fully unlocked configuration. Figure 11d The first component / mounting plate 102 and the second component 104 are shown in the unlocked position, wherein the teeth 112 on the first annular component / end face spline component 110 and the teeth 118 on the second annular component 114 are completely disengaged from each other, such that the housings 105 of the first component / mounting plate 102 and the second component 104 are freely rotatable relative to each other about the first axis "D".

[0094] exist Figure 11a In the illustrated configuration, the third magnet 144 is attracted to both the second magnet 142 and the third magnet 144, thereby pulling the first component / mounting plate 102 toward the housing 105 of the support column 130 and the second component 104. In the described embodiment, the device is configured such that when in the locked position, there is a total locking force of approximately 120 N between the first component / mounting plate 102 and the second component 104 (this, combined with appropriate head size, particularly the indexing mechanism and the diameter and position of the ring magnet, provides a starting torque of 2 Nm). As will be understood, the starting torque is the torque that can be applied before the first and second bodies begin to peel away from each other. This can be important because hinged joints are often subjected to eccentric loading.

[0095] As will also be understood, the starting torque depends on factors other than holding force / retaining force / locking force, such as the diameter of the end face spline member 110 or the diameter of this ring of engagement balls 152, 154.

[0096] To transition to the unlocked state, the support column 130 needs to move toward the first component / mounting plate 102. While it may seem that the presence of the first magnet 140 will at least initially increase the work required by the motor to do so (compared to the absence of the first magnet), it should be noted that the device is configured such that... Figure 11aIn the locked state shown, the contact plate 134 of the support is held in a predetermined position, which places the second magnet 142 between the first magnet 140 and the third magnet 144. This ensures that the pulling force of the first magnet 140 on the second magnet 142 is significantly less than the pulling force when they are in contact with each other. Moreover, the third magnet 144 has a certain degree of magnetic pull on the second magnet 142. Accordingly, the work / power required to move the second magnet (and therefore the contact plate 134) away from the first magnet 140 is significantly less compared to when the first magnet 140 and the second magnet 142 are in contact.

[0097] Specifically, in the described and illustrated embodiment, the contact plate 134 of the support post is held in a predetermined position, which positions the second magnet 142 approximately midway between the first magnet 140 and the third magnet 144, but such that the second magnet 142 is slightly closer to the first magnet 140 than the third magnet 144. This means that the magnetic forces exerted on the second magnet by the first magnet 140 and the third magnet 144 are almost (but not completely) balanced. Accordingly, the motor requires very little work / power to move the support post 130 toward the first component / mounting plate 102. In fact, once the second magnet 142 has reached the midpoint between the first magnet 140 and the third magnet 144, the magnetic pull of the third magnet 144 on the second magnet 142 will be greater than the magnetic pull of the first magnet 140. As the contact plate 134 advances toward the first component / mounting plate 102, the magnetic pull of the third magnet 144 on the second magnet 142 gradually increases.

[0098] When pillar 130 has been moved to Figure 11b In the configuration shown, the motor must then pull the teeth 118 on the body 105 / 115 of the second member 104 away from the teeth 112 on the first member / mount plate 102. Although there is a sufficiently large holding / retaining force (at least 160 N) to hold the second member 104 on the first member / mount plate 102 (via engaging balls 152, 154), the motor needs to apply a force smaller than this holding / retaining force, because only a sufficient force (approximately 95 N in this embodiment) is needed to overcome the attraction of the first magnet 140 pulling the second magnet 142 and the third magnet 144.

[0099] The motor continues to drive the strut 130 until the housing 105 of the second component 104 has moved away from the first component / mounting plate 102 by an amount sufficient to disengage the teeth 112 of the first annular component 110 from the teeth 118 on the second annular component 114. Figure 11d As shown. At this time, the holding force that secures the support column 130 and the housing 105 of the second component 104 to the first component / mounting plate 102 is approximately 160 N. By controlling the gap between the first magnet 140, the second magnet 142, and the third magnet 144, and with Figure 11a In comparison, Figure 11d The configuration shown achieves higher holding power. Specifically, although in Figure 11d In the unlocked state, there is a relatively large gap between the first magnet 140 and the second magnet 142, but a relatively small gap between the second magnet 142 and the third magnet 144 (compared to the state when in the unlocked state). Figure 11a The gap between the first magnet 140 and the second magnet 142 is smaller in the locked state than in the locked state, thus achieving a higher total holding force. A higher total holding force is expected in the unlocked position because the diameter S of the rings of the engagement balls 152, 154 is smaller than the diameter S' of the first annular member 110 and the second annular member 114, which means they require a higher pulling force / holding force to ensure the same or similar starting torque of about 2 Nm (Newton-meter).

[0100] When in Figure 11d In the unlocked state shown, the first component 102 and the second component 104 can rotate relative to each other about the D-axis to a new relative rotational position / orientation. As described above, this involves driving a motor (not shown) that engages the drive gear 148 of the shaft to rotate the body 105 of the second component 104 about the shaft 132. The output of the first encoder device 135 is used to monitor the relative position of the body 105 of the second component 104 and the shaft 132 (and therefore the first component / contact plate 102, whose rotational orientation about D is fixed). When the output of the first encoder device 135 indicates that the body 105 of the second component 104 is now in the desired indexing position, the motor stops, and the first component 102 and the second component 104 are locked together, as described below.

[0101] To lock the first component 102 and the second component 104 in their new rotational position / orientation, a motor is operated to drive the lead screw mechanism 172 so as to drive the lead screw nut 176 downward along the lead screw 174. This initially causes the housing 105 of the second component 104 to be pulled upward toward the first component / mounting plate 102. As will be understood, the motor requires very little power because the housing 105 of the second component 104 has already been pulled toward the first component / mounting plate 102 by the first magnet 140, the second magnet 142, and the third magnet 144. This continues until the teeth 112 of the first annular component 110 engage the teeth 118 of the second annular component 114. Figure 11b As shown), at this point, the motor and lead screw mechanism 172 must begin to resist the magnetic force to separate the contact plate 134 of the support from the first component / mounting plate 102. However, at this point, the first magnet 140 is much closer to the second magnet 142, thus the first magnet exerts a relatively large force on the second magnet. In fact, at this point... Figure 11bIn the illustrated state, the net force on the second magnet 142 is only 95 N. Accordingly, the motor and lead screw mechanism 172 are assisted by the magnet and can more easily pull the second magnet 142 (and thus the support 130) away from the third magnet 144 (and thus away from the first component / mounting plate 102) until the contact plate 134 reaches it. Figure 11a The predetermined axial position / Z position is shown.

[0102] The output of the first rotary encoder 135 indicates the indexing rotation position of the first component / mount plate 102 and the second component 104. It may also be useful to check that the first component / mount plate 102 and the second component 104 are correctly locked together. This can be achieved in various ways, such as by using one or more sensors that can check the gap between the opposing surfaces of the first component / mount plate 102 and the second body 105, and if this gap is greater than a fixed threshold amount (which is the same for all indexing positions), corrective measures can be taken (e.g., an error / warning can be reported and / or measures can be taken to try to correct the problem, such as by attempting an unlocking / relocking operation, for example from a different position / or orientation, and / or requesting recalibration).

[0103] In this described embodiment, a sensor (hereinafter referred to as a "verification" sensor, used to check / verify that the first component / mount plate 102 and the second body 105 are correctly locked together) is provided, configured to measure the relative spatial configuration of the first and second bodies in their locked states and provide information about this relative spatial configuration. The output of the verification sensor is compared with predetermined information associated with a specific graduation position in which they are locked. If the difference between the output of the verification sensor and the predetermined information exceeds a predetermined amount, corrective measures can be taken.

[0104] In the specific embodiment described, the verification sensor is the aforementioned second rotary encoder device. Accordingly, the outputs of the first read head 160 and the second read head (not shown) of the second rotary encoder device are used to ensure that the first component / mount plate 102 and the second component 104 are correctly locked together. Specifically, when locked, the outputs of the first read head 160 and the second read head (not shown) are passed to electronics 400 within the read heads, which includes, for example, a processing device 402 (e.g., a CPU (Central Processing Unit), FPGA (Field-Programmable Gate Array), or ASIC (Application-Specific Integrated Circuit)) and a memory 404. The processing device 402 compares the values ​​received from the first read head 160 and the second read head (not shown) with values ​​stored in a lookup table located in the memory 404. Specifically, the processing device 402 compares the outputs of the first read head 160 and the second read head (not shown) to determine whether their outputs are substantially the same as those values ​​stored in the elements of a lookup table associated with a specific graduation position. If the output of either or both of the first read head 160 or the second read head (not shown) differs significantly from the value stored in the lookup table (e.g., a difference greater than 100 nm), this may indicate a problem, such as: the first component / mount plate 102 and the second body 105 are not properly locked together; the teeth 112 / 118 are damaged; there is debris between the teeth 112 / 118; there is excessive wear between the teeth / 118, etc. Accordingly, the device (e.g., the controller) can then take corrective measures in this situation. Such corrective measures may include: unlocking and relocking the first component / mount plate 102 and the second body 105 again; outputting a warning signal to the operator and / or other processes; stopping the current operation, etc.

[0105] As described above, the second rotary encoder device is an incremental encoder device. Therefore, the outputs of the first readhead 160 and the second readhead (not shown) do not include any absolute position information. Accordingly, the processor 402 compares relative (position) data / information instead of absolute position information. Specifically, for example, as those skilled in the art of position measurement encoders will understand, the scale of an incremental position encoder typically comprises an array of regularly spaced features arranged at a specific interval or "period" (which is 20 μm in the described embodiment, but as will be understood, scales with other periods can be used). The readhead can read these features (e.g., optically, magnetically, inductively, depending on the technology used), and the readhead or its output is typically used to "calculate" the relative position of the readhead and the scale as they move relative to each other. It is also well known that the signals received by and / or output by the readhead can be interpolated to provide a measurement of the relative position of the readhead and the scale with a resolution much finer than the actual period of the scale. This interpolated reading is commonly referred to as a "phase" reading. For example, typically, orthogonal (e.g., SIN and COS) signals are generated from a scale signal and / or output by a readhead. Such orthogonal (e.g., SIN and COS) signals can be interpolated to provide such "phase" readings. In the described embodiment, processor 402 uses the interpolated or "phase" reading and compares it with pre-stored "phase" readings stored in elements of a lookup table associated with a particular value.

[0106] Accordingly, when the first 104 component / mount plate 102 and the second body 105 move relative to each other as the indexing position changes, the first reading head 160 or the second reading head (not shown) need not read the scale 162 (but may do so if the configuration allows). More specifically, when the locking operation has been completed, the first reading head 160 and the second reading head (not shown) can acquire and output a single reading, and the interpolated or “phase” values ​​of these readings can be compared with pre-stored “phase” readings stored in elements of a lookup table associated with a particular value. If one or both of the phase readings differ by more than a predetermined amount (e.g., 100 nm in the example above), corrective measures can be taken as described above.

[0107] Accordingly, the data elements in the lookup table can be described as “phase-signatures” for each calibration graduation position, and corrective measures can be taken if the phase readings of the first read head 160 and the second read head (not shown) are sufficiently different from the phase-signatures in the lookup table for a given graduation position.

[0108] Before performing measurement operations using the articulated joint 100, a lookup table is filled (e.g., it can be filled during a calibration procedure). This may include the following steps: locking the first 104 component / mount plate 102 and the second body 105 relative to each other at a given graduation position, and recording / storing the phase readings of the first read head 160 and the second read head (not shown) in an element / data cell associated with the given graduation position. This step is then repeated for each of the articulated joint's graduation positions (or at least for the graduation positions where the head will be used and such verification is expected).

[0109] Optionally, the lookup table can be updated over time to allow for a small degree of drift. This can occur continuously or periodically. This can be done as part of a dedicated calibration process or during a measurement operation. For example, each time the first component / mount plate 102 and the second body 105 successfully lock together at any given graduation position (e.g., they pass the 100nm test described above), the phase readings output by the first readhead 160 and the second readhead (not shown) can replace the previous values ​​and be stored in the lookup table.

[0110] As will be understood, if necessary, a function describing the values ​​in a lookup table can be used instead of the lookup table. However, a lookup table may be preferred because it is easy to generate and because it is easy to keep it up-to-date.

[0111] As will be understood, in addition to two reading heads, a single reading head may be used, or more than two reading heads may be used. Multiple reading heads need not be positioned 90° apart from each other around scale 162. However, it has been found particularly advantageous to provide multiple reading heads that are not exactly opposite each other (i.e., not at 180°), as this can provide information about the spatial configuration of the first component / mounting plate 102 and the second body 105 in multiple dimensions, and setting them at approximately 90° may be preferred for efficiency and optimal performance.

[0112] The aforementioned second rotary encoder device is an incremental encoder, but as will be understood, it can be replaced by an absolute encoder device.

[0113] In the above embodiment, the verification sensor is a rotary encoder device. However, this is not necessarily the case. Other types of sensors can be used, such as a position-sensitive device (PSD), whose output depends on the relative spatial position of the first component / mount plate 102 and the second body 105 when locked together. In this case, a lookup table can be populated during the calibration phase to record the PSD output for each graduation position of interest (e.g., all graduation positions or only those intended for use during subsequent measurement operations). Subsequently, in use, when the first component / mount plate 102 and the second body 105 are locked at a specific graduation position, the PSD can provide an output to the processor 402, which is then compared with the value stored in a specific element of the lookup table stored in memory 404 associated with that specific graduation position. If the outputs of the PSD differ by more than a threshold amount, corrective measures can be taken.

[0114] In an alternative embodiment, the verification sensor is configured to measure only the relative height / gap between the first and second bodies (e.g., via a capacitive sensor). However, advantageously, when the first and second bodies are locked together, the output of the verification sensor is compared with a pre-stored value in an element of a lookup table associated with a specific graduation position when the first and second bodies are locked together.

[0115] As will be understood, further variations and alternative embodiments of the articulated joint described above are possible. For example, one or two of the first magnet 140, the second magnet 142, and the third magnet 144 may be replaced with a magnetically attractive (e.g., ferrous) material. This would provide an effect similar to (albeit weaker) that of providing three magnets. Accordingly, the remaining one or two magnets would need to be stronger, and therefore larger, which may (depending on the configuration) mean a greater peak motor force is required.

[0116] In another similar embodiment, the first magnet 140 is located elsewhere. For example, the first magnet 140 may be located at / towards the end of the shaft 132 away from the contact plate 134. Again, this will provide a similar effect to the auxiliary motor during the locking / unlocking process, but because the first magnet 140 is located away from the first member / mounting plate 102, it will provide a very small holding force (if any), thus requiring a larger / stronger second magnet 142 and / or third magnet 144.

[0117] Figure 12An alternative embodiment is illustrated schematically, in which the first magnet 140 is omitted, such that the second member 104 is magnetically held on the first member / mounting plate 102 by only a pair of magnets (i.e., a third magnet 144 disposed on the first member / mounting plate 102 and a second magnet 142 disposed on the contact plate 134 of the support post 132). While this is possible, the second magnet 142 and the third magnet 144 themselves would need to provide all the locking / holding force, and therefore either or both of them would need to be much stronger than the arrangement of the three magnets described above. This, in turn, would require a motor during the locking process, when the contact plate 134 of the support post is to be pulled away from the first member / mounting plate 102 (i.e., from...). Figure 11b Transform to Figure 11a (At times) it works even harder. Moreover, without the first magnet 140, all the forces holding the housing 105 of the second component 104 to the first component / mounting plate 102 must be borne by the strut 130, lever 170, and lead screw mechanism 172, as well as the associated bearings. This would require these parts to be larger / stronger, and ideally, a motor to prevent reverse drive would be needed.

[0118] Figure 13 Another alternative embodiment is shown in which the third magnet 144 is omitted, such that the second member 104 is magnetically held onto the first member / mounting plate 102 by only a pair of magnets (i.e., a first magnet 140 disposed on the top plate 115 of the housing and a second magnet 142 disposed on the contact plate 134 of the support). In this case, the first member / mounting plate 102 (at least a portion thereof) must be made of a material that can be attracted by magnets (e.g., an iron-containing material). The disadvantage of this embodiment is that the holding / retaining and starting torque is lower compared to the case with the third magnet (therefore, a larger / stronger first magnet 140 and / or second magnet 142 is required if the same holding / retaining and starting torque is desired).

[0119] Figure 14 Another alternative embodiment is shown in which the second magnet 144 is omitted, such that the second member 104 is magnetically held on the first member / mounting plate 102 by only a pair of magnets (i.e., a first magnet 140 disposed on the top plate 115 of the housing and a third magnet 144 disposed on the first member / mounting plate 102). A disadvantage of this embodiment is that the holding / retaining and starting torque is lower compared to the case with the second magnet present (therefore, a larger / stronger first magnet 140 and / or third magnet 144 would be required if the same holding / retaining and starting torque is desired). In this embodiment, the contact plate 134 may include a material that can be attracted by a magnet (e.g., an ferrous material) to assist in magnetic holding, but this is less desirable than a contact plate 134 including a magnet.

[0120] Figure 15 Another alternative embodiment is shown. In this embodiment, the magnets do not necessarily need to be stacked directly in a straight line. For example, Figure 15 Alternative locations for the first magnet 140 and / or the third magnet 144 are shown (e.g., they may be located further radially than the second magnet 142).

[0121] Magnets can also be used in a mutually repelling arrangement to provide the necessary locking / holding force.

[0122] However, it has been found that the described basis Figures 1 to 1 The arrangement of at least three stacked magnets in a straight line (all magnets arranged to attract each other) in embodiment 1 can be advantageous. In particular, it has been found that this significantly reduces the work required by the motor controlling the linear position of the strut when the strut 130 is in its locked state, and can help reduce the peak work required by the motor during the locking action. This not only reduces the size of the required motor and helps keep the hinge compact and lightweight, but also reduces the motor's heat output (which in turn improves the metering performance of the hinge by reducing / avoiding thermal deformation). Indeed, when Figures 1 to 1 In embodiment 1, the magnet can be configured to provide a pulling force of 120 N when locked and 160 N when unlocked (in order to provide a starting torque of 2 Nm). Due to the three stacked magnets in a straight line, the motor only needs to generate a peak force of 95 N.

[0123] Figure 16 It is a display Figure 3 , Figure 4 The graphs of support force and holding force of the three magnet embodiments in Figure 11 are shown. Figure 17 It is a display Figure 12 The graphs of the strut force and holding force of the two magnet embodiments are identical in all respects except for the omission of the first magnet 140. The holding force (also referred to above as “holding force” or “locking force”) is the net force that pulls the first member 102 and the second member 104 together. The strut force is the net magnetic force experienced / applied to the strut 130. Accordingly, this is the magnetic force that must be overcome in order to hold the strut 130 in place. This force can be overcome by a combination of the force applied to the strut by the motor and any frictional force in the gearing / motor / strut system (as will be understood, if frictional forces in the gearing / motor / strut system are excluded, the strut force is proportional to the work required by the motor; for example, proportional to the motor current).

[0124] like Figure 16As shown, when the first component / mounting plate 102 and the second component 104 are in their locked state, the strut force is very low (less than 10 N). Accordingly, the force required to hold the strut 130 in place is low. In fact, it is so low that, depending on the gear mechanism / motor / strut system, friction may be sufficient to hold the strut 130 in place (e.g., if it is very resistant to reverse drive). Consequently, very little or even zero motor power is required to hold the strut 130 in place. Furthermore, as stated above, Figures 1 to 1 The configuration of 1 is arranged such that, in the locked position, the support 130 is positioned such that the magnetic force biasing the second magnet 142 toward the first magnet 140 is greater than the magnetic force biasing the second magnet 142 toward the third magnet 144. Accordingly, even if the motor controlling the linear position of the support 130 is turned off, and even if the frictional force is insufficient to resist the magnetic bias and hold the support 130 in place, all that will happen is that the support 130 will retract further until the contact plate 134 abuts against the top surface 115 of the housing, which will not adversely affect the engagement of the teeth 112, 118 of the first component / mounting plate 102 and the second component 104.

[0125] This is Figure 12 In the embodiment of the two magnets, the support force experienced by the support column 130 forms a contrast. For example... Figure 17 As shown, when in a locked state (as shown in the image) Figure 12 In the state shown, a significant net magnetic force (approximately 110 N) biases the second magnet 142 toward the third magnet 144. Accordingly, in the locked position, the motor requires significant work / power to hold the strut 130 in place. In fact, the strut force is so large that even the frictional force of the lead screw mechanism, which is very resistant to reverse drive, is insufficient to overcome the strut force. Therefore, if the motor is de-energized, the strut 130 will creep toward the first component / mounting plate 102 until they come into contact, which then interferes with the engagement of the teeth 112, 118 of the first component / mounting plate 102 and the second component 104.

[0126] As from Figure 16 and Figure 17 As can be seen from the graph, the three-magnet embodiment has some drawbacks because there is a significant support force when the support 130 and the first component / mounting plate 102 are engaged. Accordingly, significant motor work / power is required to push the support force away from the first component / mounting plate 102 to separate it from the second body 104 (e.g., in...). Figure 11b and Figure 11d Between the states shown, the first component / mounting plate 102 and the second body 104 will also be held in their unlocked state (e.g., Figure 11d (The state shown). In contrast, for Figure 12In the embodiment of the two magnets, the strut force is zero, so once the strut 130 and the first component / mount plate 102 have been joined, only a very small amount of motor work / power is needed to separate the first component / mount plate 102 from the second body 104.

[0127] However, under normal circumstances, the amount of time the hinge spends in its unlocked state is significantly less than the amount of time the hinge spends in its locked state. Therefore, the benefit of the three-magnet embodiment requiring significantly less (or even zero) motor power in the locked state outweighs the cost of needing to work harder in the unlocked state.

[0128] Figures 1 to 1 The three-magnet embodiment of 1 also has the advantage that its required peak motor power is less than that of the two-magnet embodiment. In the two-magnet embodiment, the maximum amount of power required by the motor occurs when it relocks the first component / mounting plate 102 and the second body 104, and specifically when the teeth 112, 118 of the first component / mounting plate 102 and the second body 104 engage and the motor attempts to separate the contact plate 134 of the strut from the first component / mounting plate 102. At this time, the motor must overcome the attractive pull of the second magnet 142 and the third magnet 144 entirely on its own (and overcome any frictional forces in the gear mechanism / motor / strut system), thus requiring a force greater than 150N. In contrast, for the three-magnet embodiment, the peak motor power is required during the locking operation when the teeth 112, 118 of the first component / mounting plate 102 and the second body 104 engage and the motor attempts to separate the contact plate 134 of the strut from the first component / mounting plate 102 (i.e., in Figure 11b As shown in the figure, the first magnet 140 and the second magnet 142 have moved closer together (as they are when they are as shown in the figure). Figure 11d (Compared to when fully unlocked). Accordingly, the first magnet 140 is brought close enough to the second magnet 142 to apply a significant amount of tension to the second magnet 142, and thus the auxiliary motor separates the contact plate 134 of the strut from the first component / mounting plate 102. This allows the motor to apply only about 95N to achieve this separation (see...). Figure 16 Point A in the middle).

[0129] As will be understood, alternative means may be provided to hold the first component / mounting plate 102 and the second component 104 together. For example, one or more mechanical levers (such as those described in US 7213344) may be used to pull the housing 105 of the second component 104 and the first component / mounting plate 102 together. Alternatively, a mechanical spring may be used to pull the housing 105 of the second component 104 and the first component / mounting plate 102 together. However, it has been found that magnets are preferred over such mechanical solutions due to the potential for hysteresis problems caused by friction (magnets eliminate the need for any moving parts between the first component / mounting plate 102 and the second component 104).

[0130] Advantageously, the above embodiments rely on the use of ring magnets. It is possible that one or more of the ring magnets could be replaced by disk magnets; however, somewhat counterintuitively, the inventors have discovered that ring magnets have a substantially different force / distance distribution compared to disk magnets, which is significantly advantageous in this case (in particular, ring magnets appear to offer a more efficient design for a given surface area compared to disk magnets). Indeed, it has been found that in this configuration, ring magnets can provide significantly greater force (approximately 50% more) than disk magnets of the same outer diameter and depth (measured orthogonally to the diameter of the ring). Figure 18 This is a graph illustrating the strut force and starting torque of an embodiment with two disc magnets. Except that the second magnet 142 and the third magnet 144 are disc magnets instead of ring magnets (where the outer diameter of the disc magnet is the same as the outer diameter of the ring magnet), they are identical in all aspects to... Figure 12 The equivalent shown is that, as illustrated, the strut force and, crucially, the starting torque are significantly smaller than in the equivalent toroidal magnet embodiment.

[0131] This discovery enables them to provide very high holding / locking forces for articulated joints, which in turn allows the joints to withstand higher loads / higher torques before magnetic coupling failure. For example, it may be desirable to support very heavy probes (such as camera / video probes) and / or very long styluses, which provide large torques in magnetic coupling, especially during probe insertion. In the past, the need for such large forces forced designers of articulated joints suitable for supporting large loads / torques to abandon the use of magnets. For example, articulated joints disclosed in US 7263780 and US 9494403 use mechanical rods to provide locking forces. However, the inventors have discovered that using ring magnets can provide adequately large holding loads without requiring physically large magnets, and therefore can be appropriately fitted into articulated joints to be mounted on positioning devices (such as CMMs).

[0132] As an alternative to continuous ring magnets, a series of small disk magnets arranged in a ring shape can offer advantages over a single disk magnet with the same diameter as the ring shape, but continuous rings have been found to provide the most efficient design (for a given surface area).

[0133] As described above, the planar teeth 112 of the first annular member / end-face spline member 110 and the crown teeth 118 of the second annular member 114 provide stable and repeatable positioning of the first member / mounting plate 102 and the second member 104. When locked, the only physical / mechanical constraint between the first member / end-face spline member 102 and the second member 104 is the contact point between the planar teeth 112 of the first annular member / end-face spline member 110 and the crown teeth 118 of the second annular member 114. A particular advantage of this configuration is that, at each indexing position, the second member 104 is constrained relative to the first member / mounting plate 102 in all six degrees of freedom by the six contact points provided by the crown teeth 118 of the second annular member 114 and the planar teeth 112 of the first annular member / end-face spline member 110, thus providing kinematic constraints. This is true for every possible indexing position. This provides maximum position repeatability for the probe 300 mounted on the hinge joint 100 at each indexing position. Furthermore, the end face spline member 110 and the second annular member 114 have the dual function of being an indexing element and a retaining element.

[0134] If it is possible Figure 3 and Figure 4 As seen in the diagram, a safety catch 136, or "pin," is provided. The safety catch 136 serves solely as a safety mechanism to prevent the first member 102 from completely disengaging from the second member 104 in the event of failure of the magnetic holding mechanism (e.g., due to overload of the second member 104, such as due to a collision). One end of the safety catch 136 is fixed to the contact plate 134 of the support post, while the other end is loosely positioned within a gap 138 in the first member / mounting plate 102. Because it is loosely positioned within the gap in the first member / mounting plate 102, it does not act as a constraint between the first member / mounting plate 102 and the support post 130 / second member 104 (and therefore does not interfere with the aforementioned kinematic connection between the first member / mounting plate 102 and the second member 104 in the locked configuration, nor with the kinematic connection between the first member / mounting plate 102 and the support post 130 in the unlocked configuration). However, the safety stop 136 has an enlarged head member 137 that, in the event of a failure of the magnetic coupling between the second magnetic ring 142 and the third magnetic ring 144, engages the lug 139 in the gap, thereby preventing further separation of the first component / mounting plate 102 from the second component 104.

[0135] In the above embodiment, the end face spline member 110 is disposed on the second member 104 of the hinge joint, and the crown tooth 118 is disposed on the first member / mounting plate 102. However, this is not necessarily the case, and they can be disposed in the opposite manner.

[0136] In the above embodiment, the first component / mounting plate 102 and the second component 104 are magnetically held together by an arrangement of magnets, meaning that no mechanical means (e.g., an arm / lever) are required to pull and hold the first component / mounting plate 102 and the second component 104 together. Accordingly, when in the locked state, the only mechanical constraint between the first component / mounting plate 102 and the second component 104 is provided by the teeth of the end-face spline component 110 and the teeth of the second annular component 114. Therefore, when in the locked configuration, the strut 130 is decoupled from the first component / mounting plate 102, so that the strut 130 does not interfere with the aforementioned kinematic connection between the first component / mounting plate 102 and the second component 104. However, this is not necessarily the case. For example, in other embodiments, a mechanical push / pull lever arm mechanism may be provided, wherein one end of the arm is enclosed in a bearing of the first component / mounting plate 102 and the other end of the arm is enclosed in a bearing of the second component 104.

[0137] In the above embodiment, the first component / mounting plate 102 and the second component 104 are magnetically held together by an arrangement of magnets, meaning that no mechanical means (e.g., an arm / lever) are required to pull and hold the first component / mounting plate 102 and the second component 104 together. Accordingly, when in the locked state, the only mechanical constraint between the first component / mounting plate 102 and the second component 104 is provided by the end-face spline component 110 and the second annular component 114. Accordingly, when in the locked configuration, the strut 130 is decoupled from the first component / mounting plate 102 such that the strut 130 does not interfere with the aforementioned kinematic connection between the first component / mounting plate 102 and the second component 104. However, this is not necessarily the case. For example, in other embodiments, a mechanical push / pull lever arm mechanism may be provided, wherein one end of the arm is enclosed in a bearing of the first component / mounting plate 102 and the other end of the arm is enclosed in a bearing of the second component 104.

Claims

1. A metering device including an indexing hinge joint, the indexing hinge joint comprising: A first body and a second body that can be reoriented relative to each other, the first body and the second body each having a coupling element that can engage with each other, the coupling element being able to lock together with multiple different angular orientations about a first axis in order to provide multiple angularly graduated positions for the first body and the second body; At least one verification sensor is configured to provide a measurement of the relative spatial configuration of the first body and the second body when they are in their locked state, and The device is configured such that, when the first body and the second body are locked together at the indexing position, the verification sensor is used to measure the relative spatial configuration of the first body and the second body, and wherein the information obtained from the measurement is compared with calibration information obtained from at least one other measurement of the relative spatial configuration of the first body and the second body when the first body and the second body were locked at the indexing position at an earlier time point, in order to establish information about the engagement state of the first body and the second body.

2. The device as claimed in claim 1, wherein the device is configured to respond in a predetermined manner based on the result of the above comparison.

3. The device as described in claim 2, wherein, The predetermined response includes unlocking and relocking the first body and the second body at the same indexing position.

4. The device of claim 3, wherein the device is configured to unlock and relock the first and second bodies at the same indexing position if the comparison indicates that the current relative spatial configuration of the first and second bodies at the indexing position differs from the relative spatial configuration of the first and second bodies indicated by the calibration information by more than a predetermined threshold.

5. The device as claimed in claim 4, wherein, The predetermined threshold is no greater than 20 μm.

6. The device as claimed in claim 1, wherein, The verification sensor includes an encoder device, which includes a rotating scale disposed on one of the first body and the second body, and at least one first reading head disposed on the other of the first body and the second body for reading the rotating scale.

7. The device as claimed in claim 6, wherein, The encoder device of the verification sensor includes a second read head configured to read the scale.

8. The device as claimed in claim 7, wherein, The second reading head is configured to read the scale at a position 90° away from the position where the at least one first reading head reads the scale.

9. The device as claimed in any one of claims 6 to 8, wherein, The encoder device for the verification sensor includes an incremental encoder device, which includes an incremental scale having a series of periodic scale features.

10. The device as claimed in any one of claims 6 to 8, wherein, The encoder device for the verification sensor includes an optical encoder device.

11. The device of any one of claims 1 to 8, the device further comprising a motor for driving the first body and the second body about the first axis during unlocking.

12. The device of any one of claims 1 to 8, the device further comprising a main encoder device configured to monitor the relative rotational position of the first body and the second body about the first axis during unlocking.

13. The device as claimed in any one of claims 1 to 8, wherein, The first body includes a rotatable member configured to engage the second body and be rotatably fixed relative to the second body when the first body and the second body are unlocked and rotated relative to each other.

14. The device as claimed in claim 12, wherein, The first body includes a rotatable member configured to engage the second body and be rotatably fixed relative to the second body when the first body and the second body are unlocked and rotated relative to each other. The main encoder device includes a read head on one of the first body and the member and a scale on the other, such that the read head provides a measurement of the relative rotational position of the first body and the member.

15. The device of claim 12, wherein the device is configured to use the output of the main encoder device to control the rotation of the first body and the second body during unlocking.

16. The device as claimed in any one of claims 1 to 8, wherein, The calibration information is stored in a lookup table.

17. The device as claimed in any one of claims 1 to 8, wherein, The calibration information is obtained from at least one other measurement of the relative spatial configuration of the first body and the second body obtained by the verification sensor.

18. The device as claimed in any one of claims 1 to 8, wherein, The information obtained from the measurement is the current measurement obtained by the verification sensor.

19. The device as claimed in claim 17, wherein, The calibration information is a measurement obtained by the verification sensor when the first and second bodies were locked at the graduation position at an earlier time point.

20. The device as claimed in any one of claims 1 to 8, wherein, The device includes a probe head having the indexing hinge joint, the probe head being configured to support a measuring probe on a coordinate positioning device, such that the measuring probe can be arranged in multiple different indexing rotation orientations.

21. The device according to any one of claims 1 to 8, the device comprising a memory device including the calibration information.

22. The device as claimed in claim 21, wherein, The device includes a probe head having the indexing hinge joint, the probe head being configured to support a measuring probe on a coordinate positioning device such that the measuring probe can be arranged in multiple different indexing rotation orientations, the probe head including the memory device.

23. A method of operating a metering device including an indexing hinge joint, the indexing hinge joint comprising: A first body and a second body each have engaging elements that can be locked together about a first axis at multiple different angular orientations, so as to provide multiple angularly graduated positions in which the first body and the second body can be locked relative to each other. The method includes at least one verification sensor configured to provide an output that depends on the relative spatial configuration of the first body and the second body in their locked states. This locks the first body and the second body together at the indexing position; Acquire readings from the at least one verification sensor; and Compare i) information derived at least from the readings with ii) calibration information derived at least from at least one other reading of the relative spatial configuration of the first and second bodies obtained by the verification sensor when the first and second bodies were locked at the graduation position at an earlier time point.

Images