Method of installing rotating scale member

Abstract

A method of mounting a rotating scale member on a component rotatable about an axis of rotation, the rotating scale member including a body on which a series of scale features defining a scale extending about a scale axis are disposed or may be disposed. The method comprises: i) mounting one or more intermediate scale positioning members on the component and manipulating a radial configuration of the one or more intermediate scale positioning members until a desired radial configuration with respect to the axis of rotation is achieved; and ii) subsequently fitting the rotating scale member onto the one or more intermediate scale positioning members, whereby the body of the rotating scale member assumes a default radial position relative to the one or more intermediate scale positioning members.

Description

[0001] The invention relates to a method of mounting a rotary scale member for use with a rotary encoder on a component of an apparatus, for example a machine component.

[0002] A metrological scale is used for position measurement of relatively movable parts of a device (e.g., relatively movable parts of a machine). A metrological scale typically has a series of features on it that can be read by a read head so that the read head can provide a measure of its position along or around the scale. A metrological scale can be mounted on one part of a device and read by a suitable read head attached to another part of the device. The relative movement between two parts of a device can be measured by a read head. Types of metrological scales include: magnetic scales (wherein the scale features are provided by features having specific magnetic properties), capacitive scales (wherein the features are provided by features having specific capacitive properties), inductive scales (wherein the features are provided by features having specific inductive properties), and optical scales (wherein the features are provided by features having specific optical properties). An optical scale can be transmissive or reflective. An example of an optical scale configuration is disclosed in EP-A-0 207 121 and US-A-4,974,962.

[0003] In order to measure relative rotational displacement of a component of the apparatus about an axis of rotation, a scale may be provided on a rotating scale member mounted on one of the components of the apparatus, and a readhead configured to read the scale may be provided on the other component. Typically, the rotating scale member is in the form of a disc scale member or a ring scale member. In either case, the rotating scale member comprises a body on which is or may be provided a series of scale features defining a scale extending about the scale axis. Typically, the rotating scale member is mounted on a rotating component of the apparatus and the readhead is mounted on a stationary component of the apparatus, but this need not be the case and the reverse may also be possible.

[0004] Figure 1 shows a prior art configuration of an encoder device 2 (described in more detail in WO2021-116660) comprising a rotating scale member 4, which in the form shown is a disc scale member, and a readhead 10. The readhead 10 is mounted on a fixed assembly 12 of the device, and the disc scale member 4 is mounted on a shaft 6' of a part 6 of the device, which shaft can rotate about an axis of rotation A. The disc scale member 4 includes a substantially planar body 7, which has a scale track 8 on one of its planar surfaces, which extends completely annularly around the scale axis S. The scale track 8 includes a series of features that can be read by the readhead 10 (mounted on the assembly 12, which is fixed relative to the cylindrical shaft 6) to determine the relative position / movement of the disc scale member 4 and the readhead 10. A hole 14 is provided through the middle of the planar body 7, through which the cylindrical shaft 6' can extend when the disc scale member 4 is mounted on the cylindrical shaft 6'. The disc ruler member 4 further comprises three pairs of resiliently compliant members (cantilevered spring / flexure members in this embodiment) 16 spaced around the edge of the aperture 14 to engage with and radially locate the cylindrical shaft 6' when the cylindrical shaft is inserted through the aperture.

[0005] The three pairs of cantilever spring members 16 define a default inner diameter of the hole 14, which is smaller than the diameter of the shaft 6'. Accordingly, the disc scale member 4 needs to be press-fitted onto the shaft 6', whereby the shaft 6' engages with the side of each cantilever spring member 16 facing the middle of the hole 14 and causes each cantilever spring member to bend slightly radially outward. The elasticity of the material of the cantilever spring member 16 produces a radial reaction force on the shaft 6', thereby producing a radial self-positioning effect. If the reaction force provided by each cantilever spring member 16 is nominally the same, the disc scale member 4 will nominally self-center on the shaft 6'. Accordingly, if it is desired that the scale axis S and the rotation axis A are substantially coaxial, the disc scale member 4 should be configured so that the scale axis S is located on the following point / axis, and the cantilever spring member 16 centers the disc scale member on this point / axis.

[0006] If desired, the planar body 7 of the disc scale member 4 may be further secured to the shaft. For example, in the described embodiment, the planar body 7 includes three holes through which mechanical fasteners 28 (such as bolts 28) may pass to secure the planar body 7 to the shaft 6.

[0007] As schematically depicted in FIG1 , even with such self-locating (e.g. self-centering) functionality, and despite best efforts to manufacture the rotating scale member 4 and shaft 6′ as accurately as possible, it is likely that the relative positions of the rotation axis A and the scale axis S are not as expected / desired (e.g. not coaxial), which may result in measurement errors (if not corrected and / or compensated for). For example, for those embodiments where it is desired that the scale axis S and the rotation axis A are coaxial and the cantilever spring member 16 is configured to self-center the disc scale member 4, it is likely that there will be at least some deviation between the rotation axis A and the scale axis S. In many cases, this is at least primarily due to the geometric centers of the rotation axis A and the shaft 6′ not coinciding.

[0008] Accordingly, it is known to adjust a rotating scale member after it has been mounted on a device, such as described in EP 1094302 and WO 2004 / 008076. The present invention provides an effective alternative technique for improving the mounting of a rotating scale member on a component of a device.

[0009] According to a first aspect of the invention, there is provided a method of mounting a rotary scale member on a first part of an apparatus, wherein the first and second parts of the apparatus are relatively rotatable about an axis of rotation, the rotary scale member comprising a body on which a series of scale features defining a scale extending about the scale axis is or can be provided, the method comprising: i) mounting one or more intermediate scale positioning members on the first part of the apparatus, and manipulating the radial configuration of at least one of the one or more intermediate scale positioning members until a desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved; and ii) subsequently fitting the rotary scale member to the one or more intermediate scale positioning members, whereby the body of the rotary scale member is radially positioned at a default (in other words, "predetermined") radial position / location relative to the one or more intermediate scale positioning members.

[0010] As will be appreciated, the one or more intermediate scale locating members control / govern the radial position / location of the rotating scale member mounted thereto relative to the first part of the device. Accordingly, the one or more intermediate scale locating members may be referred to as one or more intermediate radial scale locating members, but for the sake of brevity are referred to herein as intermediate scale locating members. As will be appreciated, the one or more intermediate scale locating members may be mounted directly on the first part of the device or indirectly (e.g., via another member / device, such as a support member / device that is itself mounted directly on the first part of the device).

[0011] Benefits of the method of the present invention may include improved ease of manufacture of a rotary scale member and / or reduced risk of damage to scale bearing components of the rotary scale member, compared to known techniques for providing radial adjustability. For example, by the present invention, it is not necessary to provide the rotary scale member with features that facilitate radial adjustment thereof, thereby simplifying the rotary scale member and its manufacture. Furthermore, since the intermediate scale positioning member is manipulated until the desired radial configuration is achieved, it is not necessary to check the radial configuration of the rotary scale member. This may result in benefits of ease of manufacture of the rotary scale member (since it is not necessary to provide an accurate reference surface for checking on the rotary scale member) and / or may reduce / avoid the risk of damage to the rotary scale member that may result from such checking.

[0012] As will be appreciated and as described in more detail below, the rotating scale member and the one or more intermediate scale positioning members interact with each other (e.g., features thereof interact with each other) so as to thereby radially position the rotating scale member at a default (predetermined) radial position / location relative to the one or more intermediate scale positioning members.

[0013] As will be appreciated, according to the invention, it can be said that fitting the rotating scale member to the one or more intermediate scale positioning members causes the radial position of the body of the rotating scale member to be automatically radially positioned at said default radial position. The body of the rotating scale member can be said to (automatically) adopt (or "forced to adopt"), in other words, "take up"; for example, the body of the rotating scale member "rests in" or, for example, is "radially biased to" or "radially constrained in" said default (predetermined) radial position relative to the one or more intermediate scale positioning members.

[0014] As will be appreciated, the default (predetermined) radial position / location may be the radial position that the body of the rotating scale member will naturally / automatically reside in (and return to) relative to the one or more intermediate scale locating members in the absence of (or removal of) any external radial forces applied thereto. The default (predetermined) radial position / location may be referred to as a repeatable radial position / location (i.e., it is repeatable relative to the one or more intermediate scale locating members).

[0015] The device may be a machine. Accordingly, the first part of the device on which the rotary scale member is mounted may be a machine part. The device may include an encoder mounting (e.g., the encoder mounting is subsequently mounted to another device), for example, the device may include a housing for a closed encoder device. Accordingly, the first part may include a part of a housing for a closed encoder device.

[0016] The first component may be a component of the device that is configured to rotate about the rotation axis in use / operation, and the second component may be configured to remain stationary / rotationally fixed about the rotation axis. This may be preferred because a readhead for reading the scale on the rotating scale member may be attached to the stationary / rotationally fixed component, which may be easier from an assembly / wiring perspective. However, this need not necessarily be the case, and the second component may be a component of the device that rotates about the rotation axis in use / operation, and the first component (on which the rotating scale member is mounted) may remain stationary / rotationally fixed about the rotation axis.

[0017] The body of the rotating scale member may include an annular body. The body (e.g., annular body) may include a planar disk. Optionally, the thickness of such a planar disk is not greater than 5 mm, for example, not greater than 3 mm, for example, about 1 mm thick. This series of position features can be arranged on the plane surface of the body of the rotating scale member (e.g., arranged on the plane surface of the planar disk) (opposite to the peripheral edge of the axial extension associated with the more common ring scale / encoder). Accordingly, the rotating scale member may include a disc scale member (which may also be interchangeably referred to as a scale disc member) (e.g., for a disc encoder). The disc scale member includes a planar surface, on which a series of scale features defining a scale are arranged or can be arranged, and the scale axis extends orthogonally to the planar surface. Accordingly, the scale feature can be a radially extending scale feature. For example, the scale feature can be elongated in the radial direction, for example, each scale feature can include a radially extending line (relative to the scale axis). In an alternative embodiment, the rotating scale member includes an annular scale member, wherein a series of position features are arranged on the peripheral edge of the axial extension of the body.

[0018] The body of the rotary scale member may comprise a metallic material, but as will be appreciated, other non-metallic materials may be used.

[0019] The scale may include optical, capacitive, inductive and / or magnetic scale features. As will be appreciated, references to "optical" and "optical" herein encompass electromagnetic radiation (EMR) anywhere in the infrared to ultraviolet range. In particular, in the case of optical scale features, the scale may be a reflective or transmissive scale.

[0020] Preferably, the scale comprises a complete annular track of scale features (e.g. as opposed to just a partial arc). The scale features in the track may comprise incremental scale features (with or without one or more reference marks) or absolute scale features. The rotating scale member may comprise more than one series (e.g. more than one track) of scale features.

[0021] The method may further comprise: iii) subsequently tightening the body of the rotary scale member so as to fix the radial position / location of the body of the rotary scale member relative to the first part of the device. This may be achieved by tightening the body of the rotary scale member to the first part of the device. This may be achieved via one or more mechanical fasteners (e.g., one or more bolts and / or clamps) and / or via an adhesive. Preferably, the body of the rotary scale is tightened / fixed relative to the first part of the device, wherein the body of the rotary scale is in the default radial position it was in step ii) (i.e., before the tightening step of iii), the body of the rotary scale has not moved radially away from the default radial position). Of course, additional fine adjustment of the radial position of the body of the rotary scale member may be made before the body of the rotary scale member is fixed / fixed so as to move the body of the rotary scale member away from the default radial position it was in step ii), but this is generally undesirable and offsets at least some of the advantages of the present invention.

[0022] The method may further comprise: iv) removing one or more intermediate scale positioning members. As will be appreciated, the body of the rotating scale member may maintain its radial position / location because the body of the rotating scale member has been tightened in step iii) to fix its radial position / location. Removing one or more intermediate scale positioning members may provide the following benefit: the one or more intermediate scale positioning members may be reused. Removing one or more intermediate scale positioning members may also provide benefits in terms of reducing the mass on the first component of the device and / or improving the space / access to the first component (e.g., the one or more intermediate scale positioning members once removed no longer take up space and may therefore provide more space / better access to other components).

[0023] Step i) may include checking the radial configuration of at least one of the one or more intermediate scale positioning members. This may include determining the (e.g. radial) position of at least a portion / surface / feature of the one or more intermediate scale positioning members in order to determine the radial configuration of the portion / surface / feature. In particular, step i) may include determining (and e.g. directly measuring) the (e.g. radial) position of the (these) portion / surface / feature of the one or more intermediate scale positioning members (the rotating scale member is configured to engage against the one or more intermediate scale positioning members in order to be assembled on the one or more intermediate scale positioning members) in order to determine the radial configuration of the (these) portion / surface / feature.

[0024] The above-mentioned step of determining the (e.g. radial) position of at least a portion / surface / feature of the one or more intermediate scale positioning members may include measuring the (e.g. radial) position of at least a portion / surface / feature of the one or more intermediate scale positioning members in a plane extending perpendicular to the rotation axis (and, for example, may include directly measuring the position of the (these) portion / surface / feature of the one or more intermediate scale positioning members in said plane extending perpendicular to the rotation axis, against which the rotating scale member is configured to engage so as to be assembled on the one or more intermediate scale positioning members). Determining / measuring the position may include determining / measuring the radial position of at least a portion / feature / surface of the one or more intermediate scale positioning members (e.g. relative to the rotation axis).

[0025] Verifying / determining / measuring the position may include using an inspection tool / sensor. Verifying / determining / measuring the position may, for example, include directly measuring the (e.g. radial) position of the (these) part / surface / feature of one or more intermediate scale positioning members, against which the rotating scale member is configured to engage so as to be assembled on the one or more intermediate scale positioning members. The inspection tool / sensor may include a contact tool / sensor that contacts a part / surface / feature (e.g. an axially extending part / surface) of one or more intermediate scale positioning members. The inspection tool / sensor may include a non-contact tool / sensor (e.g., the non-contact tool / sensor obtains such a measurement result without contacting the one or more intermediate scale positioning members).

[0026] Step i) may comprise determining a change / difference in the apparent radius of at least a portion / surface / feature of the one or more intermediate scale locating members relative to the axis of rotation at at least three different circumferentially spaced positions (i.e. different spaced positions around the axis). Such measurements at different circumferentially spaced positions may be obtained by holding the inspection tool / sensor at a fixed rotational position about the axis of rotation and rotating the one or more intermediate scale locating members about the axis of rotation so that the inspection tool / sensor can obtain measurements of the one or more intermediate scale locating members at different circumferentially spaced positions.

[0027] The measurements described above may be performed / conducted while the first component of the apparatus and one or more intermediate scale positioning members mounted on the first component are rotating (if the first component is a rotatable component of the apparatus), or may be performed / conducted while the first component of the apparatus and one or more intermediate scale positioning members mounted on the first component are stationary.

[0028] The rotating scale member and the one or more intermediate scale positioning members can be configured to engage with each other at at least two, preferably at least three engagement positions (e.g., regions) spaced circumferentially around the axis of rotation. The at least two, preferably at least three engagement positions can be predetermined engagement positions (regions). (e.g., predetermined) at least two, preferably at least three engagement positions (regions) can be spaced circumferentially around the axis of rotation (e.g., substantially equiangularly). It has been found that three or four substantially equiangularly spaced engagement positions (regions) can be preferred. The method may include determining at least two, preferably at least three engagement positions (regions) on one or more intermediate scale positioning members (e.g., radial) positions so as to determine the radial configuration of the one or more intermediate scale positioning members. As will be understood, and as explained in more detail below, at any given engagement position (region), there may be more than one contact point between the rotating scale member and the one or more intermediate scale positioning members. For example, in an embodiment where the discrete mounting features comprise a pair of cantilevered spring members with their free ends close to each other, there will be two points of contact at the engagement position (one on each cantilevered spring member). However, even if there is more than one point of contact between the rotating scale member and one or more intermediate scale locating members at any given engagement position, it may be sufficient to perform only one measurement of the (radial) position of the engagement position (region), although of course more than one measurement may be performed if desired.

[0029] At least one of these engagement positions may be a rigid engagement position (e.g. provided by (e.g. radially) rigid non-compliant features / surfaces on the rotating scale member and one or more intermediate scale positioning members). At least one of these engagement positions may be a (e.g. radially) elastically compliant engagement position (e.g. provided by an elastically compliant member, e.g. disposed on the rotating scale member and / or one or more intermediate scale positioning members, as described in more detail below). A combination of rigid engagement positions and elastically compliant engagement positions may be provided. The elastically compliant engagement positions may be configured such that the body of the rotating scale member is biased by the elastically compliant engagement positions into / against the rigid engagement positions, such that the rigid engagement positions thereby define a default radial position of the body of the rotating scale member relative to the one or more intermediate scale positioning members. In a specific example, at least two of these engagement positions may be rigid engagement positions, and at least one of these engagement positions may be an elastically compliant engagement position. For example, as described below in combination with Figure 8 By way of example and in more detail, two of the engagement positions may be rigid engagement positions, and one of the engagement positions may be an elastically compliant engagement position. In other embodiments (e.g., as described below in conjunction with FIGS. 2 to 3), Figure 7As described in more detail below, all engagement locations may be resiliently compliant engagement locations. It has been found that three or four (e.g., substantially equiangularly) circumferentially spaced resiliently compliant engagement locations (regions) may be preferred. As described in more detail below, the resiliently compliant engagement locations may be provided by one or more resiliently compliant members (e.g., a single flexible portion, or multiple (e.g., pairs) of flexible portions / cantilever spring members acting together / as one).

[0030] The rotating scale member (and / or one or more intermediate scale locating members) may comprise a plurality of discrete mounting features configured such that at step ii), the rotating scale member and the one or more intermediate scale locating members engage with each other at at least two, preferably at least three (predetermined) engagement locations circumferentially spaced about the axis of rotation. The discrete mounting features may comprise rigid features / members or resiliently compliant features / members.

[0031] The rotating scale member may be assembled to the one or more intermediate scale positioning members via one or more resiliently compliant members (e.g., at least two, and in some instances, preferably three of four resiliently compliant members (or pairs of resiliently compliant members)) disposed at circumferentially spaced positions around the scale axis. The one or more resiliently compliant members may be configured to radially position / fix the rotating scale member relative to the intermediate scale positioning member at the default (predetermined) radial position / location. Such one or more resiliently compliant members may include radially compliant members and / or tangentially compliant members.

[0032] Discrete mounting features of the rotary scale member may include (eg radially and / or tangentially) resiliently compliant members.

[0033] In alternative embodiments, one or more of the intermediate scale locating members may comprise discrete mounting features, such as resiliently compliant members, against which the rotating scale member fits.

[0034] Discrete mounting features (particularly, discrete mounting features including elastically compliant members) may include spring members, such as flexible portions, such as cantilever spring members. Accordingly, for example, the rotating scale member may include at least three spring members (e.g. flexible portions, such as cantilever spring members). Discrete mounting features may include multiple mounting features that function together / as one; for example, discrete mounting features may include multiple (e.g., pairs of) (e.g., cantilever) spring members that are configured to provide (e.g., in magnitude and direction) a common spring force between one or more intermediate scale positioning members and the body of the rotating scale member. Accordingly, for example, the rotating scale member may be assembled to the one or more intermediate scale positioning members via (e.g., the rotating scale member may include) at least three groups (e.g., three pairs of) (e.g., cantilever) spring members. The pair of cantilevered spring members may extend in opposite directions from each other such that the free ends of the pair of cantilevered spring members are proximate to each other (e.g., sufficiently proximate such that the free ends may be considered to engage one or more intermediate scale positioning members at substantially the same engagement location and may be configured to provide substantially the same spring force (e.g., in magnitude and direction)).

[0035] The discrete mounting feature (e.g., elastically compliant member) may be integrally formed with the body of the rotating scale member (or integrally formed with one or more intermediate scale locating members). Although this may be preferred, this is not required. For example, the discrete mounting feature (e.g., elastically compliant member) may be formed separately from the body of the rotating scale member and separately from the one or more intermediate scale locating members. In such a case, the discrete mounting feature (e.g., elastically compliant member) may be provided for (e.g., secured to) the body of the rotating scale member, or provided for (e.g., secured to) one or more intermediate scale locating members (or a combination thereof). Alternatively, the discrete mounting feature (e.g., elastically compliant member) is provided separately from the rotating scale member and separately from the one or more intermediate scale locating members, and is inserted between the rotating scale member and the one or more intermediate scale locating members (e.g., after the rotating scale member and the one or more intermediate scale locating members have been placed / mounted on the first component). In preferred embodiments, discrete mounting features (e.g., resiliently compliant members) are provided on / by the rotating scale member (as opposed to being provided on / by one or more intermediate scale locating members, and as opposed to the rotating scale member and one or more intermediate scale locating members being provided completely separately), and in particularly preferred embodiments, the discrete mounting features (e.g., resiliently compliant members) are integrally formed with the body of the rotating scale member.

[0036] As will be appreciated, all discrete mounting features (e.g., resilient compliant members) may be provided on / by the rotating scale member, or all discrete mounting features (e.g., resilient compliant members) may be provided on / by the intermediate scale positioning member. Alternatively, discrete mounting features (e.g., resilient compliant members) may be provided via any combination of: discrete mounting features provided on / by the rotating scale member; discrete mounting features provided on / by the intermediate scale positioning member; and discrete mounting features inserted completely and separately between the rotating scale member and the intermediate scale positioning member after both have been positioned on the first component.

[0037] Discrete mounting features (eg, resilient compliant members) may be disposed radially inwardly of a series of scale features. In alternative embodiments, discrete mounting features (eg, resilient compliant members) may be disposed radially outwardly of a series of scale features.

[0038] The method may include press-fitting the rotating scale member and at least one intermediate scale positioning member together. The rotating scale member and the one or more intermediate scale positioning members may be configured such that the action of press-fitting the rotating scale member and the at least one intermediate scale positioning member together causes one or more (e.g., at least two, and in some instances, preferably three of four) resiliently compliant members (or pairs of resiliently compliant members) to shift and thereby urge the rotating scale member into engagement with the one or more intermediate scale positioning members via a (e.g., radial) reaction force, such that the body of the rotating scale member is radially positioned at (e.g., adopts / rests at / biases to) a default (predetermined) radial position / location relative to the one or more intermediate scale positioning members.

[0039] Step i) may comprise arranging separate intermediate scale positioning members at at least two, for example at least three (e.g. substantially equiangular) circumferentially spaced positions around the axis of rotation on the first part of the device, the radial configuration of at least one of these intermediate scale positioning members being independently manipulable from the other intermediate scale positioning members (and, for example, the radial configuration of each of these intermediate scale positioning members being independently manipulable). In an alternative embodiment, and in contrast to the use of such a plurality of (e.g. separate) intermediate scale positioning members (whose radial configuration is independently manipulable), step i) may comprise arranging an integral intermediate scale positioning member on the first part of the device, the integral intermediate scale positioning member providing a surface for receiving a rotating scale member at at least three (e.g. substantially equiangular) circumferentially spaced positions around the axis of rotation. As will be appreciated, the integral intermediate scale positioning member may be composed of a plurality of components / assemblies. The integral intermediate scale positioning member composed of a plurality of components / assemblies may be, for example, treated as a unit / member, for example, positioned as a unit on the first part of the device. The integral intermediate scale positioning member may include, for example, an annular intermediate scale positioning member, the annular intermediate scale positioning member including a (continuous) annularly extending surface, the rotating scale member being configured to be mounted against the annularly extending surface at least three (e.g., substantially equiangular) annularly spaced positions around the axis of rotation. The continuous surface does not need to have a regular cross-sectional shape (perpendicular to the axis of rotation / scale axis observation). In one embodiment, the annular intermediate scale positioning member may include a substantially circular intermediate scale positioning member (such as an annular or disc-shaped intermediate scale positioning member), which extends around the axis of rotation when mounted on the first component of the device. Accordingly, the annular integral intermediate scale positioning member may include a substantially circular surface, which extends around the axis of rotation when mounted on the first component of the device, for receiving the rotating scale member. The integral intermediate scale positioning member may be configured so that the manipulation of the radial configuration of the integral intermediate scale positioning member enables manipulation of all radial configurations in at least three annularly spaced positions at the same time / simultaneously.

[0040] Step i) may include inspecting the axially extending surface of one or more intermediate scale positioning members to determine the radial configuration of the one or more intermediate scale positioning members. The axially extending surface may include the outer (e.g., outermost) periphery / edge (e.g., circumferential edge) of the intermediate scale positioning member. The axially extending surface may have a substantially circular cross-sectional shape (perpendicular to the axis of rotation / scale axis). When mounted on the first component of the device, the axially extending surface of the intermediate scale positioning member may extend substantially parallel to the axis of rotation. For example, the axially extending surface may have a substantially cylindrical form. In an alternative embodiment, the axially extending surface may have a non-cylindrical form, such as a substantially truncated cone form, or a substantially truncated spherical form.

[0041] The desired radial configuration of the one or more intermediate scale locating members may be one that ensures that when the rotary scale member is mounted thereon in step ii) the scale axis and the rotational axis of the first part of the apparatus are in a desired positional relationship, e.g. substantially coaxial.

[0042] As described above, the rotating scale member and the one or more intermediate scale positioning members can be configured to engage with each other at at least three engagement positions (e.g., regions) circumferentially spaced around the axis of rotation. The desired radial configuration can be a configuration where the center points of the at least three engagement positions substantially coincide with the axis of rotation.

[0043] As will be appreciated, the scale features may be read by a readhead. Accordingly, the method may further comprise mounting a readhead on a second part of the apparatus (e.g. a machine) at any appropriate stage, the readhead being configured to read the scale features of the rotating scale member. Accordingly, the method may comprise a method of assembling or mounting an encoder comprising a rotating scale member as described above and / or below, and a readhead.

[0044] According to a second aspect of the invention, there is provided a method of mounting a rotary scale member on a first part of an apparatus (e.g., on a machine part), wherein the first and second parts of the apparatus are relatively rotatable about an axis of rotation, the rotary scale member comprising a body on which a series of scale features defining a scale extending about the scale axis are or can be arranged, the method comprising, in any suitable order: i) mounting one or more intermediate scale positioning members on the first part of the apparatus; ii) assembling the rotary scale member to the one or more intermediate scale positioning members via (e.g., one or more) resiliently compliant members, the resiliently compliant members being configured to (automatically) radially position / set the rotary scale member relative to the intermediate scale positioning member at a default (predetermined) radial position / location; iii) manipulating the radial configuration of at least one of the one or more intermediate scale positioning members mounted on the first part of the apparatus until a desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved. A benefit of this aspect of the invention may be that (for example) the resiliently compliant members may help the rotating scale member escape any significant form or shape deformation that (in the absence of such resiliently compliant members) might otherwise be imposed on the rotating scale member via manipulation of the radial configuration of the one or more intermediate scale locating members, while ensuring that the rotating scale member (automatically) self-locates / adopts a default (predetermined) radial position / location relative to the one or more intermediate scale locating members. The method may comprise, after steps i) to iii), tightening the body of the rotating scale member so as to fix the radial position of the body of the rotating scale member relative to the first part of the apparatus, and then removing the one or more intermediate scale locating members.

[0045] As will be appreciated, according to this aspect of the invention, step ii) may be performed during or before step iii). Furthermore, according to this aspect of the invention, step ii) may be performed before or after step i).

[0046] Step iii) may include checking the radial configuration of at least one of the one or more intermediate scale positioning members. The checking may include determining the position of at least a portion of the one or more intermediate scale positioning members in order to determine their radial configuration. In those embodiments where the rotating scale member is assembled to the one or more intermediate scale positioning members before or during at least one of the one or more intermediate scale positioning members has been manipulated to the desired radial configuration, the radial configuration of the one or more intermediate scale positioning members may be determined / checked by checking the one or more intermediate scale positioning members and / or the rotating scale member.

[0047] The rotary scale member may be placed on the first component a) after the one or more intermediate scale positioning members have been mounted on the first component, or b) simultaneously with the one or more intermediate scale positioning members being mounted on the first component (i.e., the rotary scale member may be assembled to the one or more intermediate scale positioning members before or simultaneously with the one or more intermediate scale positioning members being mounted on the first component). In other words, optionally, the rotary scale member is not mounted on the first component before the one or more intermediate scale positioning members are mounted on the first component.

[0048] As will be appreciated, the features described above in conjunction with the first aspect of the invention are equally applicable to the second aspect of the invention. Accordingly, for example, fitting the rotary scale to one or more intermediate scale positioning members may include press-fitting them together, whereby (e.g. one or more) resiliently compliant mounting features are displaced, and thereby the rotary scale member is urged to engage with the one or more intermediate scale positioning members via a reaction force, so that the body of the rotary scale member is radially positioned at (e.g., adopted / rested at / biased to) a default (predetermined) radial position / location relative to the one or more intermediate scale positioning members. As described above in conjunction with the first aspect of the invention: the rotary scale member may include one or more resiliently compliant members; the one or more intermediate scale positioning members may include one or more resiliently compliant members, against which the rotary scale member is assembled; the resiliently compliant member may be arranged completely separately from the rotary scale member and the intermediate scale positioning member; or any combination of the above options is possible. The resiliently compliant member may include a flexible portion. The body of the rotary scale member may include a planar disc, wherein a series of position features are arranged on a planar surface of the planar disc.

[0049] According to a third aspect of the invention, there is provided an apparatus comprising: one or more intermediate scale positioning members which may be mounted on a first part of an apparatus (e.g. mounted on a machine part), the apparatus having said first and second parts which are relatively rotatable about a rotation axis, the one or more intermediate scale positioning members being configured such that a radial configuration of at least one of the one or more intermediate scale positioning members may be manipulated relative to the rotation axis; and a rotating scale member comprising a body on which a series of scale features defining a scale extending around the scale axis is or may be provided, the rotating scale member being mountable to the one or more intermediate scale positioning members such that a radial position of the rotating scale member relative to the rotation axis is controlled / dictated by the one or more intermediate scale positioning members, the rotating scale member being mountable to the one or more intermediate scale positioning members via one or more elastically compliant members, the one or more elastically compliant members being configured such that when the rotating scale member is mounted to the one or more intermediate scale positioning members, the rotating scale member is (automatically) radially positioned / set at a default (predetermined) radial position / location relative to the intermediate scale positioning member. The apparatus may further comprise means for securing (eg mechanical fasteners and / or adhesive) for securing the rotating scale member to the first part of the device independently of the one or more intermediate scale locating members, eg so that the one or more intermediate scale locating members may then be removed.

[0050] As will be appreciated, the features described above in conjunction with the first and second aspects of the invention are equally applicable to the third aspect of the invention. For example, (e.g., one or more) resiliently compliant members may include radially compliant members and / or tangentially compliant members. As described above in conjunction with other aspects of the invention: the rotating scale member may include one or more resiliently compliant members; one or more intermediate scale positioning members may include one or more resiliently compliant members, against which the rotating scale member is assembled; the resiliently compliant member may be arranged completely separate from the rotating scale member and the intermediate scale positioning member; or any combination of the above options is possible. The rotating scale member may be assembled to one or more intermediate scale mounting members via at least three resiliently compliant members, the at least three resiliently compliant members being positioned at different positions around the scale axis, for example at substantially equiangular positions. The resiliently compliant member may include a flexible portion. The rotating scale member may be assembled to one or more intermediate scale positioning members, so that the radial position / position of the rotating scale member relative to the rotation axis is controlled by the one or more intermediate scale positioning members. As will be appreciated, the apparatus may comprise at least a first part of the apparatus (and optionally a second part of the apparatus), in which case one or more intermediate scale locating members may be mounted on the first part of the apparatus. The apparatus may comprise a readhead for reading scale features (e.g. mounted on the second part of the apparatus). As will be appreciated, the apparatus may be configured so that the rotating scale member may fit onto one or more intermediate scale locating members already mounted on the first part of the apparatus.

[0051] According to a fourth aspect of the invention, there is provided a method of mounting a rotary scale member on a first component of an apparatus, wherein the first and second components of the apparatus are relatively rotatable about a rotation axis, the rotary scale member comprising a body on which a series of scale features defining a scale extending about the scale axis is or can be provided, the method comprising in any suitable order: i) mounting one or more intermediate scale positioning members on the first component, at least one of the intermediate scale positioning members comprising at least one resiliently compliant member; ii) engaging the rotary scale member and the one or more intermediate scale positioning members with each other via the one or more resiliently compliant members (thereby radially positioning the rotary scale member at a default radial position relative to the intermediate scale positioning members); iii) manipulating the radial configuration of at least one of the one or more intermediate scale positioning members mounted on the components until a desired radial configuration of the one or more intermediate scale positioning members relative to the rotation axis is achieved; and iv) after steps i) to iii), tightening the body of the rotary scale member so as to fix the radial position of the body of the rotary scale member relative to the first component, and then removing the one or more intermediate scale positioning members. Optionally, step ii) is performed before or during step iii). Optionally, step ii) is performed before step i). As will be appreciated, the features described above in conjunction with the first, second and third aspects of the invention are equally applicable to the fourth aspect of the invention. In this embodiment of the invention, the rotating scale member may be placed on the first component before steps i) and ii). As will be appreciated, the features described above in conjunction with the first to third aspects of the invention are equally applicable to the fourth aspect of the invention.

[0052] According to a fifth aspect of the invention, there is provided an apparatus comprising: a rotating scale member comprising a body on which a series of scale features defining a scale extending around a scale axis is or can be provided; one or more intermediate scale positioning members, the one or more intermediate scale positioning members being configured for mounting on a first part of a device having the first and second parts relatively rotatable about the rotation axis so that the radial configuration of at least one of the one or more intermediate scale positioning members can be manipulated relative to the rotation axis, wherein at least one of the one or more intermediate scale positioning members comprises one or more resiliently compliant members against which the rotating scale member can be engaged (and thereby mounted to the one or more intermediate scale positioning members) so that the rotating scale member is biased towards a default radial position relative to the intermediate scale positioning member; and means for securing the rotating scale member to the part independently of the one or more intermediate scale positioning members so that the radial position of the body of the rotating scale member is maintained after the one or more intermediate scale positioning members are removed. As will be appreciated, the features described above in conjunction with the first to fourth aspects of the invention are equally applicable to the fifth aspect of the invention.

[0053] The present application also describes a rotating scale member, the rotating scale member comprising: a body on which a series of scale features defining a scale extending around a scale axis is or can be provided; and a (e.g., radial) resiliently compliant member (e.g., a flexible portion) for radially urging the body in a predetermined radial direction against one or more rigid stop surfaces provided by the rotating scale member. As will be appreciated, the resiliently compliant member and the one or more rigid stop surfaces can be configured to engage one or more features of a first component of an apparatus (e.g., a machine component) and / or to engage one or more intermediate (scale positioning) members mounted on such a first component of the apparatus (e.g., a machine), the first and second components of the apparatus being relatively rotatable about the axis of rotation. Such a configuration can provide highly repeatable positioning of the body of the rotating scale member relative to the component of the apparatus to which the body of the rotating scale member is to be mounted. Accordingly, a method of mounting a rotating scale member on a first part of a device (the first part is relatively rotatable about a rotation axis relative to a second part of the device) may include press-fitting the rotating scale member onto a feature provided on the first part of the device (wherein such a feature may be integral with the first part, for example may be the shaft itself, or may be an intermediate scale positioning member, such as those described herein), whereby the elastically compliant member is displaced and thereby one or more rigid stop surfaces are urged via a reaction force to engage with the feature provided on the first part of the device, so that the body of the rotating scale member is (automatically) radially positioned (e.g., adopted / biased to) a default (predetermined) radial position relative to the feature provided on the first part of the device, the default (predetermined) radial position being defined by the one or more rigid stop surfaces. The elastically compliant member and the one or more rigid stop surfaces may be disposed radially inwardly of the scale, for example around the edge of a hole extending axially through the body of the rotating scale member. The rotating scale member may include a disc scale member. The elastically compliant member may be integrally formed with the body of the rotating scale member. The elastically compliant member may include a leaf spring. The resiliently compliant member may include one or more cantilevered spring members.

[0054] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

[0055] FIG1 shows a prior art configuration of an encoder device comprising a self-positioning (particularly, self-centering) rotating scale member mounted to a shaft of the device;

[0056] Figure 2a to Figure 2e There is shown the apparatus and stages involved in mounting a rotary scale member to a component of an apparatus according to a first aspect of the invention;

[0057] Figures 3a to 3dThere is shown the apparatus and stages involved in mounting a rotary scale member to a component of an apparatus according to a second aspect of the invention;

[0058] Figures 4a to 4d There is shown the apparatus and stages involved in mounting a rotary scale member to a component of an apparatus according to a third aspect of the invention;

[0059] Figure 5a to Figure 5e There is shown the apparatus and stages involved in mounting a rotary scale member to a component of an apparatus according to a fourth aspect of the invention;

[0060] Figure 6 is a flow chart of a method according to the present invention;

[0061] Figure 7 A configuration according to a fifth aspect of the present invention is shown; and

[0062] Figure 8 A configuration according to a sixth aspect of the present invention is shown.

[0063] As mentioned earlier in this document, it may be desirable to be able to selectively control the radial position / location of a rotating scale member mounted to a first part of an apparatus (which is relatively rotatable about an axis of rotation relative to a second part of the apparatus) so that the rotating scale member has a desired radial configuration relative to the axis of rotation. In particular, it may be desirable to arrange the scale axis of a scale provided on the rotating scale member at a desired radial position / location relative to the axis of rotation. For example, it is quite typical, but not necessarily the case, that the desired radial configuration is such that the scale axis and the axis of rotation are substantially coaxial. Various techniques according to the invention are described below, the purpose of which is to configure a rotating scale member so that its axis of rotation is substantially coaxial with the axis of rotation, but as will be appreciated, this need not necessarily be the case, and the methods of the invention may be used to provide different desired radial configurations of the rotating scale member.

[0064] refer to Figure 2a to Figure 2e as well as Figure 6 , shows the apparatus and stages involved in mounting a rotary ruler member, in this embodiment a disc ruler member 4, to a component 106 of an apparatus according to a first aspect of the invention.

[0065] refer to Figure 2a (showing an isometric view of the intermediate scale positioning member 103 mounted on component 106), Figure 2b (shown Figure 2a A cross-sectional view of the configuration taken in the ZX plane) and Figure 6, the method begins at step 602 by positioning the intermediate scale locating member 103 (in this embodiment, a unitary intermediate scale locating member in the form of an annular ring) on ​​the shaft 106' of the component 106. In this embodiment, the intermediate annular ring member 103 comprises a metal ring having a tapered inner circumferential surface 105 and a cylindrical outer circumferential surface 107. As will be appreciated, the intermediate annular ring member 103 may be made of other materials, such as plastic.

[0066] like Figure 2b As shown, when the intermediate annular ring member 103 is mounted on the shaft 106', the tapered inner circumferential surface 105 of the intermediate annular ring member 103 engages the opposite tapered surface 109 of the shaft 106'. The radial configuration of the intermediate annular ring member 103 can be determined / verified by measuring the intermediate annular ring member 103. For example, the measurement of the position of the cylindrical outer surface 107 can be performed at multiple points around the intermediate annular ring member 103. This can be done in various ways, including, for example, using a sensor, such as a dial test indicator (DTI), which interacts with the axially extending cylindrical outer surface 107 to measure any changes in the radial position of the cylindrical outer surface 107 at different rotational positions of the intermediate annular ring member 103. Such measurements can be obtained when the intermediate annular ring member 103 rotates around the rotation axis A. Alternatively, such measurements can be obtained by moving the intermediate annular ring member 103 to different rotational orientations around the rotation axis A and measuring when the intermediate annular ring member 103 is stationary. In both of the above methods, the sensor may be maintained at a fixed position about the rotation axis A. In another embodiment, such measurements may be obtained by maintaining the intermediate annular ring member 103 stationary throughout the process of determining the radial configuration and varying the position about the rotation axis A at which the sensor interacts with the cylindrical outer surface 107 (e.g., by moving the same sensor or using multiple different sensors). As will be appreciated, rather than measuring the axially extending cylindrical outer surface 107 directly, the position of the axially extending cylindrical outer surface may be inferred by measuring different portions of the intermediate annular ring member 103.

[0067] If the radial configuration of the intermediate annular ring member 103 does not match the desired radial configuration, the radial configuration of the intermediate annular ring member 103 may be manipulated, as described in more detail below, until the desired radial configuration is achieved in step 604. In this embodiment, the desired radial configuration of the intermediate annular ring member 103 is a radial configuration in which it is expected that the rotary scale member 4, which will subsequently be mounted on the intermediate annular ring member (as described in more detail below), will automatically radially position (e.g., adopt) a desired radial position relative to the rotation axis A (e.g., such that the scale axis of the rotary scale member is substantially coaxial with the rotation axis A) when mounted on the intermediate annular ring member 103.

[0068] In the depicted embodiment, the radial configuration of the intermediate annular ring member 103 can be manipulated via a plurality of adjustment bolts 111 (a, b, c). Figure 2b As shown, an adjustment bolt (e.g., adjustment bolt 111a) passes through an axially extending hole 113 in the intermediate annular ring member 103 and threadedly engages a threaded hole 115 in the component 106. Tightening the adjustment bolt by rotation of the adjustment bolt 111a will eventually cause the head 117 of the adjustment bolt 111a to engage the upper surface of the intermediate annular ring member 103, and further tightening of the adjustment bolt 111a will cause at least the portion of the intermediate annular ring member 103 adjacent the adjustment bolt 111a to be manipulated to be displaced axially downward (in an upward direction). Figure 2b As will be appreciated, due to the engagement of the corresponding tapered surfaces 105, 109 of the intermediate annular ring member 103 and the shaft 106', any downward axial displacement of the intermediate annular ring member 103 will also cause the portion of the intermediate annular ring member 103 adjacent the adjustment bolt 111a to be manipulated to displace radially outward, thereby changing the radial configuration of the intermediate annular ring member 103.

[0069] As will be appreciated, in this embodiment, the shape of the intermediate annular ring member 103 is deformed as a result of manipulation of the adjustment bolts described above (i.e., the action described above will cause the intermediate annular ring member 103 to stretch). In alternative embodiments, the geometry of the shaft 106' and the inner surface of the intermediate annular ring member 103 may be configured (e.g., with mating truncated spherical forms) such that when the adjustment bolts 111a are manipulated, the intermediate annular ring member 103 tends to rotate (i.e., roll) on the shaft, wherein the degree of rolling of the intermediate annular ring member 103 causes an effective change in the radial configuration of the surface against which the rotating scale member 4 will abut when assembled. Figure 2c to Figure 2d1 , the rotary scale member 4 to be assembled on the intermediate annular ring member 103 may be the same as the rotary scale member described above in connection with FIG. 1 and therefore like parts share the same reference numerals. As will be appreciated, this need not necessarily be the case and the rotary scale member may take a different form, such as a ring scale member. Assuming that the rotation axis A and scale axis S are nominally coaxial as desired, in this embodiment the intermediate annular ring member 103 may be manipulated until at least the following point of the cylindrical outer surface 107 of the intermediate annular ring member 103 is centered relative to the rotation axis A: the point at which the cantilever spring member 16 of the disc scale member 4 is configured to engage.

[0070] Once the operator / installer is satisfied that the intermediate annular ring member 103 is in the desired radial configuration relative to the axis of rotation A, the disc scale member 4 may then be assembled to the intermediate annular ring member 103 ( Figure 6 Step 606). This Figure 2c , which shows a disc scale member 4 assembled onto an intermediate annular ring member 103. In this embodiment, since the inner diameter of the hole 14 defined by the cantilever spring member 16 is smaller than the diameter of the cylindrical outer surface 107 of the intermediate annular ring member 103, the rotating scale member 4 is press-fitted onto the intermediate annular ring member, whereupon the cantilever spring member 16 will radially engage the cylindrical outer surface 107 of the intermediate annular ring member 103 and be radially displaced outwardly by the cylindrical outer surface of the intermediate annular ring member, whereby the body 7 of the disc scale member 4 (and therefore the scale 8 and the scale axis S) will automatically be radially positioned relative to the intermediate annular ring member 103 (e.g., the body of the disc scale member will automatically adopt / bias to / constrained to) a default (predetermined) radial position / location. In this embodiment, the default (predetermined) radial position / location relative to the intermediate annular ring member 103 will be governed / controlled by the relative elasticity of the cantilever spring member 16. In a preferred embodiment, the cantilever spring members 16 are nominally identical and nominally have the same elasticity so that the body will self-center on the intermediate annular ring member 103. In accordance with the intent described above, due to the configuration of the disc ruler member 4 and due to the previous intentional manipulation of the radial configuration of the intermediate annular ring member 103 at step 604, when the disc ruler member 4 has adopted (i.e., positioned in) its default (predetermined) radial position / location relative to the intermediate annular ring member 103, the scale axis S should be in a predetermined desired position / location relative to the component 6 and its rotational axis A, such as being substantially coaxial with the rotational axis. Accordingly, no further adjustment of the radial configuration of the disc ruler member 4 is required.

[0071] Figure 6Step 608 is an additional optional step that involves further attaching the substrate to the substrate, for example, via an adhesive (not shown) and / or via mechanical fasteners (such as bolts 28 (see Figure 2e )) The mechanical fasteners fasten the body 7 of the disc ruler member 4 to the component 6, these mechanical fasteners pass through the holes 26 in the body 7 of the disc ruler member 4 and threadingly engage the threaded holes 129 in the component 106 (see Figure 2a and Figure 2b ). Figure 6 Step 610 is another optional step involving removing the intermediate annular ring member 103. This may be beneficial because the intermediate annular ring member 103 may be reused, and / or because the space previously occupied by the intermediate annular ring member 103 may be used for other purposes.

[0072] Figures 3a to 3d A variation of the apparatus shown in Figure 2 is depicted which is suitable for use with the present invention. Identical parts share the same reference numerals. Figures 3a to 3d Equipment and Figure 2a to Figure 2e The device of FIG. 20 is different in that the shaft 206' and the intermediate annular ring member 203 do not have mating opposing tapered surfaces. Instead, in this embodiment, the intermediate annular ring member 203 comprises an oversized annular ring that fits on the shaft 206' (i.e., the inner diameter of the oversized annular ring is greater than the diameter of the shaft 206', so that the oversized annular ring is a loose fit on the shaft) and is axially supported / retained on the shoulder 119 of the device component 206. Because the intermediate annular ring member 203 is a loose fit on the shaft 206', the intermediate annular ring member can be easily moved laterally (in the XY plane) to change its radial configuration.

[0073] In this embodiment, an adjustment tool 210 is provided to help the operator / installer precisely control the manipulation of the radial configuration of the intermediate annular ring member 203. The adjustment tool 210 includes a second annular ring member 212 that fits tightly on the shaft 206' and is located on top of the intermediate annular ring member 203. The second annular ring member 212 includes a first elongated slot 214 and a second elongated slot 216, the centers of which are annularly spaced 90° from each other, and the first elongated slot and the second elongated slot are formed near the outer edge of the second annular ring member 212 to create a first flexible portion 218 and a second flexible portion 220.

[0074] A first bolt 222 having a conical head is provided. The shank of the bolt 222 is received through the center of the first slot 214 and threadedly engages a threaded hole 224 provided in the intermediate annular ring member 203. The first bolt 222 is tightened until its conical head contacts the top surface of the second annular ring member 212. Thereafter, further tightening of the first bolt 222 will drive its conical head into the slot 214, and due to the radial reaction force between the first bolt 222, the second annular ring member 212 and the shaft 206', the first bolt 222 will be pushed radially outward (in Figure 3a and Figure 3b The first flexible portion 218 is flexed radially outward (in the Y dimension shown), which in turn will cause the first flexible portion 218 to flex radially outward (in the Y dimension). Due to the connection between the first bolt 222 and the intermediate annular ring member 203, any such radial outward movement of the first bolt 222 will be exerted on the intermediate annular ring member 203, thereby radially shifting the radial position of the intermediate annular ring member 203 (in the Y dimension).

[0075] As will be appreciated, due to the resistance to radial displacement of the first flexible portion 218, if / when the first bolt 222 reverses and leaves the first slot 214, the first flexible portion 218 will cause the first bolt 222 to be pulled radially inward, thereby reversing the radial displacement of the intermediate annular ring member 203 (along the Y dimension).

[0076] A second bolt 230 is positioned through the second slot 216 and is configured and operated in the same manner as the first bolt 222 to facilitate adjustment of the radial position of the intermediate annular ring member 203 (in Figure 3a and Figure 3b As will be appreciated, third and fourth slots (not shown) and corresponding bolts (not shown) may be provided at diametrically opposed locations from the first and second slots 214, 216 to facilitate radial adjustment of the intermediate annular ring member 203 along the X and Y dimensions in a direction opposite to that provided by the first and second slots 214, 216 and corresponding bolts 222, 230.

[0077] As with the first embodiment described in conjunction with FIG. 2 , the radial configuration of the intermediate annular ring member 203 can be checked (e.g., measured) to verify that the intermediate annular ring member has the desired radial configuration. If it does not have the desired radial configuration, the intermediate annular ring member 203 can be further manipulated until the intermediate annular ring member has the desired radial configuration. Once the intermediate annular ring member has the desired radial configuration, then as Figure 3cAs shown, the disc scale member 4 can be assembled onto the cylindrical outer surface 205 of the intermediate annular ring member 203. According to the embodiment of FIG. 2 , the default inner diameter of the hole 14 defined by the cantilever spring member 16 of the disc scale member 4 is smaller than the diameter of the cylindrical outer surface 205 of the intermediate annular ring member 203. Accordingly, in this embodiment, assembling the rotary scale member 4 onto the intermediate annular ring member 203 includes press-fitting the rotary scale member 4 onto the intermediate annular ring member 203. Upon said assembly, the cantilever spring member 16 will radially engage the cylindrical outer surface 205 of the intermediate annular ring member 203 and be radially displaced outwardly by the cylindrical outer surface of the intermediate annular ring member, whereby the body 7 of the disc scale member 4 (and therefore the scale 8 and the scale axis S) will be automatically radially positioned (in other words, forced to adopt / biased to / constrained to) a default (predetermined) radial position relative to the intermediate annular ring member 203. According to the intention described above, due to the configuration of the disc ruler member 4 and due to the previous intentional manipulation of the radial configuration of the intermediate annular ring member 203, when the disc ruler member 4 is positioned in / adopts its default (predetermined) radial position relative to the intermediate annular ring member 203, the ruler axis S should be in a predetermined desired position relative to the rotation axis A, for example substantially coaxial with the rotation axis. Accordingly, no further adjustment of the radial configuration of the disc ruler member 4 is required.

[0078] like Figure 3d As depicted, the body 7 of the disc ruler member 4 may be secured to a component 206 of the apparatus, if desired, for example via an adhesive (not shown) and / or via mechanical fasteners such as bolts 28 which may threadingly engage threaded holes 129 in the component 206 (see FIG. Figure 3a and Figure 3b ). Additionally, optionally, the intermediate annular ring member 203 and / or associated tool 210 may be removed.

[0079] Figures 4a to 4d Another variation of an apparatus suitable for use with the present invention is depicted. Like components share like reference numerals. In this embodiment, component 306 does not include a protruding shaft. Accordingly, in this embodiment, rather than providing a single integral intermediate scale positioning member, three separate intermediate scale positioning members 303 are provided at circumferentially spaced locations around the axis of rotation A, the radial configuration of each intermediate scale positioning member being independently manipulable as described in more detail below.

[0080] like Figure 4a and Figure 4bAs shown, the intermediate scale positioning member 303 of this embodiment includes a bolt 305 and a ring 307. The bolt 305 includes a conical head 309 and a threaded shank 311. The ring 307 includes a cylindrical outer surface 308 and a conical inner surface 310, against which the conical head 309 engages. The threaded shank 311 of each bolt 305 is threadedly engaged with a corresponding threaded hole 313 in the component 306, wherein the ring 307 is clamped between the conical head 309 of the bolt 305 and the component 306. The cylindrical outer surfaces 308 of the three intermediate scale positioning members 303 together provide an arrangement on which the disc scale member 4 can be assembled.

[0081] Accordingly, according to the present invention, it is desirable to manipulate the radial configuration of the three intermediate scale positioning members 303 into a desired radial configuration (e.g., by manipulating at least one of the intermediate scale positioning members 303 in a manner described below), so that when the disc scale member 4 is assembled to the three intermediate scale positioning members 303, the disc scale member 4 will be positioned at a desired radial position / location relative to the rotation axis A of the component (e.g., so that the scale axis S and the rotation axis A are substantially coaxial).

[0082] The radial configuration of each intermediate scale locating member 303 can be manipulated by tightening its bolts 305. Tightening of the bolts 305 causes the bolts 305 to be driven axially further into the component (in the Z dimension), which will cause the ring 307 to stretch outwardly, thereby increasing the effective diameter of the ring and thereby changing the radial position of the junction of the ring 307 and the disc ruler member 4 (when it is assembled on the ring).

[0083] As with the first and second embodiments described above in conjunction with FIGS. 2 and 3 , the radial configurations of the intermediate scale positioning members 303 may be checked (e.g., measured) to verify that the intermediate scale positioning members provide the desired radial configuration. If the desired radial configuration is not provided, one or more of the intermediate scale positioning members 303 may be further manipulated until the intermediate scale positioning members provide the desired radial configuration. Once the intermediate scale positioning members provide the desired radial configuration, then as Figure 4cAs shown, the disc scale member 4 can be assembled onto the cylindrical outer surface 308 of the ring 307 of the three intermediate scale positioning members 303. According to the embodiment of Figures 2 and 3, the default inner diameter of the hole 14 defined by the cantilever spring member 16 of the disc scale member 4 is smaller than the effective diameter defined by the radially outermost point of the cylindrical outer surface 308 of the ring 307 of the three intermediate scale positioning members 303. Accordingly, in this embodiment, assembling the rotating scale member 4 onto the three intermediate scale positioning members 303 includes press-fitting the rotating scale member 4 onto the ring 307 of the intermediate scale positioning member 303. Upon said assembly, the cantilever spring member 16 will radially engage the rings 307 of the three intermediate scale positioning members 303 and be displaced radially outwardly by the rings of the three intermediate scale positioning members, thereby causing the body 7 of the disc ruler member 4 (and hence the scale 8 and the scale axis S) to automatically adopt (in other words, be radially positioned / biased to / constrained to) a default (predetermined) radial position / location relative to the three intermediate scale positioning members 303. In accordance with the above-described intent of the method of the present invention, due to the configuration of the disc ruler member 4 and due to the deliberate manipulation of the radial configuration of the three intermediate scale positioning members 303, when the disc ruler member 4 adopts its default (predetermined) radial position / location relative to the three intermediate scale positioning members 303, the scale axis S should be in a predetermined desired position / location relative to the rotation axis A, e.g. substantially coaxial with the rotation axis. Accordingly, no further adjustment of the radial configuration of the disc ruler member 4 is required.

[0084] like Figure 4d As depicted, the body 7 of the disc ruler member 4 may be secured to the component 306, if desired, for example via an adhesive (not shown) and / or via mechanical fasteners such as bolts 28 which may threadingly engage threaded holes 129 in the component 306 (see Figure 3a and Figure 3b ). In addition, optionally, the three intermediate scale positioning members 303 may be removed.

[0085] In the embodiment described above, three intermediate scale positioning members 303 are used, but as will be appreciated, only two intermediate scale positioning members may be used, or more than three intermediate scale positioning members may be used, if desired. The plurality of intermediate scale positioning members 303 may also take different forms, which enables the radial configuration of these intermediate scale positioning members to be manipulated in other ways. For example, these intermediate scale positioning members may take the form of offset cam members, as described below in conjunction with Figure 5. In other embodiments, the intermediate scale positioning members 303 may be interconnected via a rigid linkage mechanism, so that these intermediate scale positioning members may be handled and / or mounted to a component as a whole (but wherein, for example, the radial configuration of these intermediate scale positioning members may still be manipulated independently of one another). In another embodiment, not all intermediate scale positioning members need to be radially adjustable, such as described below in conjunction with Figure 8 Described embodiments.

[0086] Figure 5a to Figure 5e Another variant of the device suitable for use with the present invention is depicted. The same components share the same reference numerals. In this embodiment, component 406 does not include a protruding shaft, nor does it include a suitable surface / body to which one or more intermediate scale positioning members are directly mounted. Instead, component 406 is a hollow annular member. Accordingly, in this embodiment, a support device 450 is provided, as described in more detail below, which can be fastened to component 406 and a support plate 452 is provided, to which one or more intermediate scale positioning members (in this case, three intermediate scale positioning members 403) can be fastened, and the radial configuration of these intermediate scale positioning members can be manipulated. Accordingly, in this embodiment, one or more intermediate scale positioning members are indirectly arranged / mounted on the component via support device 450.

[0087] like Figure 5aAs shown, the support device 450 includes a support plate 452, a radially expandable clamping part 454, a tapered member 456 and a bolt 458. The bolt passes through the support plate 452, the radially expandable clamping part 454 and is threadedly engaged with the threaded hole in the tapered member 456. The three intermediate scale positioning members 403 can be pre-installed on the support plate 452 or can be provided and installed separately. The support device 450 is installed on the component 406 by inserting the support plate 452, the radially expandable clamping part 454 and the tapered member 456 into the hollow shaft 406. The bolt 458 is then tightened, whereby, due to the axial position of the bolt being fixed by the interaction between its head and the support plate 452, the tapered member 456 is pulled axially upward (in the Z dimension), which in turn causes the expandable clamping part 454 to expand radially outward until it engages with the component 406, thereby radially clamping the support device 450 to the interior of the component 406.

[0088] In this embodiment, the intermediate scale positioning members 403 each include an offset cam member. Accordingly, each intermediate offset cam member 403 includes a cylindrical head 407 and a cylindrical pin portion 409. The cylindrical pin portion 409 is received in a hole 411 in the support plate and can rotate in the hole so that the intermediate offset cam member 403 can rotate about an axis C. The axis C is offset from the geometric center of the cylindrical head 407. Accordingly, the radial position of the radially outermost point of the cylindrical head 407 (relative to the rotation axis A of the component 406) can be changed by rotating the intermediate scale positioning member 403 about the rotation axis C of the intermediate scale positioning member.

[0089] As with the first, second, and third embodiments described above in conjunction with FIGS. 2 , 3 , and 4 , the radial configuration of the intermediate scale positioning members 403 can be checked (e.g., measured) to verify that the intermediate scale positioning members provide the desired radial configuration. If the desired radial configuration is not provided, one or more of the intermediate scale positioning members 403 can be further manipulated until the intermediate scale positioning members provide the desired radial configuration. Once the intermediate scale positioning members provide the desired radial configuration, then as Figure 5dAs shown, the disc ruler member 4 can be assembled onto the head 407 of the intermediate offset cam member 403. According to the embodiment of Figures 2, 3 and 4, the default inner diameter of the hole 14 defined by the cantilever spring member 16 of the disc ruler member 4 is smaller than the effective diameter defined by the radially outermost point of the head 407 of the intermediate offset cam member 403. Accordingly, in this embodiment, assembling the rotating ruler member 4 onto the intermediate offset cam member 403 includes press-fitting the rotating ruler member 4 onto the head 407 of the intermediate offset cam member 403. Upon said assembly, the cantilever spring member 16 will radially engage the head 407 of the intermediate offset cam member 403 and be radially displaced outwardly by the head of the intermediate offset cam member 403, whereby the body 7 of the disc ruler member 4 (and therefore the scale 8 and the scale axis S) will automatically adopt (in other words, radially position / bias to / constrained to) a default (predetermined) radial position / location relative to the intermediate offset cam member 403. According to the above-described intent of the method of the present invention, due to the configuration of the disc ruler member 4 and due to the deliberate manipulation of the radial configuration of the intermediate offset cam member 403, when the disc ruler member 4 adopts its default (predetermined) radial position / location relative to the intermediate offset cam member 403, the ruler axis S should be in a predetermined desired position / location relative to the rotation axis A, for example substantially coaxial with the rotation axis. Accordingly, no further adjustment of the radial configuration of the disc ruler member 4 is required.

[0090] like Figure 5e As depicted in FIG. 1 , if desired, the body 7 of the disc scale member 4 may be secured to the component 406, for example via an adhesive (not shown) and / or via mechanical fasteners such as bolts 28 which may threadingly engage threaded holes 129 in the machine component 406 (see FIG. 1 ). Figure 5a , Figure 5b and Figure 5c ). In addition, optionally, the intermediate offset cam member 403 may be removed.

[0091] In the embodiment described above, three intermediate offset cam members 403 are used, but it should be understood that if necessary, only two intermediate scale positioning members can be used, or more than three intermediate scale positioning members can be used. The intermediate scale positioning members 403 can also take different forms, which makes it possible to manipulate the radial configuration of these intermediate scale positioning members in other ways, such as by taking the form of the intermediate scale positioning members shown in Figure 4. In addition, the intermediate scale positioning members 403 do not need to be the same, but a combination of different types of intermediate scale positioning members can be used. Further, instead of arranging multiple separate intermediate scale positioning members on the support device 450 of Figure 5, the support device 450 can be configured to only receive an integral intermediate scale positioning member, such as the intermediate annular ring member of Figure 2 or Figure 3 (for example, the support plate 452 can include a protruding shaft, and the intermediate annular ring member of Figure 2 or Figure 3 can be received on this protruding shaft).

[0092] In the embodiment described above, the mounting features of the rotating scale member (e.g. the cantilever spring 16) are provided radially inwardly of the scale track 8. However, as will be appreciated, this need not necessarily be the case and the mounting features may be provided radially outwardly of the scale track 8. Accordingly, in contrast to the embodiment described above, the disc scale member may be fitted to the at least one intermediate scale locating member such that the disc scale member is located radially inwardly of the space defined by the at least one intermediate scale locating member.

[0093] In the embodiments described above, the rotating scale member comprises a disc scale member, wherein the scale track and features are provided on a planar surface of the disc scale member. As will be appreciated, this need not necessarily be the case. For example, the rotating scale member may comprise a ring scale member, wherein the scale track and features are provided on an axially extending cylindrical periphery of the body of the rotating scale member.

[0094] In the embodiments described above, the rotating scale member includes an integral resiliently compliant (e.g., spring) member (particularly a cantilevered spring / flexure) that is configured such that the body of the rotating scale member automatically adopts (in other words, is radially positioned / biased to / constrained to) a default (predetermined) radial position / location relative to one or more intermediate scale positioning members. As will be appreciated, other configurations may also achieve the same functionality. For example, a non-integrated resiliently compliant member may be provided (e.g., a resiliently compliant member formed separately from and attached to the body of the rotating scale member or the intermediate scale positioning member). Further, in another embodiment, one or more intermediate scale positioning members may include a resiliently compliant member. For example, such an embodiment in Figure 7(which is a modified version of the embodiment of FIG. 2 ), wherein the same components share the same reference numerals. Accordingly, similar to the embodiment of FIG. 2 , Figure 7 The intermediate scale positioning member 103' comprises a metal ring having a tapered inner circumferential surface and a generally cylindrical outer circumferential surface. Figure 7 In the embodiment of the present invention, three radially protruding leaf spring flexible portions 104 are arranged at circumferentially spaced positions on the generally cylindrical outer circumferential surface of the intermediate scale positioning member 103' and can be radially elastically displaced into an elongated hole 121, which extends axially through the intermediate scale positioning member 103'. The tapered inner circumferential surface is mounted on the opposite tapered surface of the shaft 106'. Therefore, the radial configuration of the intermediate scale positioning member 103' can be adjusted by tightening one or more of the adjustment bolts 111 in the same manner as described above in conjunction with Figure 2. Once the operator is satisfied with the radial configuration of the intermediate scale positioning member 103', the rotating scale member 4' (in this embodiment, a scale disk member having a flat circular inner circumferential surface) can be press-fitted onto the three radially protruding leaf spring flexible portions 104 of the intermediate scale positioning member 103', whereby the three radially protruding leaf spring flexible portions 104 are radially displaced inwardly and in response push the rotating scale member 4' into engagement with the intermediate scale positioning member 103' via a reaction force, so that the body 7 of the rotating scale member 4' automatically adopts (in other words, is radially positioned / biased to / constrained to) a default (predetermined) radial position / position relative to the intermediate scale positioning member 103'.

[0095] As will be appreciated, although in most of the above described embodiments the resilient compliant member comprises a cantilevered spring / flexure, a non-cantilevered flexure may be used in place of the cantilevered flexure, for example, a spring / flexure as in Figure 3c on the second annular ring member 212 or on Figure 7 The sheet flexible portion used on the intermediate scale positioning member 103'. Further, other types of elastic compliant members, such as coil springs, may be used. In addition, the mounting feature of the rotating scale member does not have to be an elastic compliant member, because there are other ways to ensure that the body 7' (and therefore the scale 8 and the scale axis S) of the rotating scale member 4 automatically adopts a default (predetermined) radial position / position relative to one or more of its intermediate scale positioning members. For example, with reference to the embodiment of Figure 2, in a manner similar to the corresponding tapered surfaces 105, 109 of the intermediate annular ring member 103 and the shaft 106', the outer circumferential surface 107 of the intermediate annular ring member 103 and the inner circumferential surface of the disc scale member 4 can have relative tapered surfaces, which will cause the intermediate annular ring member and the disc scale member to be assembled together at a default (predetermined) radial position / position relative to each other.

[0096] In the embodiments described above, three elastically compliant members are provided on the rotating scale member or the intermediate scale positioning member. However, this need not necessarily be the case. For example, Figure 8 An embodiment in which only a single elastic compliant member is provided is shown. In this embodiment, component 306 is identical to the component shown in FIG. 4 and described above in conjunction with the figure. In this embodiment, a first cam-shaped intermediate scale positioning member 503 and a second cam-shaped intermediate scale positioning member 504 and a third intermediate scale positioning member 505 are provided, which are threadedly engaged to the threaded hole 313 in component 306. Similar to the offset cam member of FIG. 5, the radial position of the radially outermost point of the head (relative to the rotation axis A of component 306) of the first cam-shaped intermediate scale positioning member 503 and the second cam-shaped intermediate scale positioning member 504 can be changed by rotating the intermediate scale positioning member around the rotation axis C of the cam-shaped intermediate scale positioning member. In this embodiment, the radial configuration of the third intermediate scale positioning member 505 is not manipulable. Instead, the third intermediate scale positioning member 505 includes a flat round head bolt having a fixed and unchangeable diameter. However, as will be appreciated, in another embodiment, the radial configuration of the third intermediate scale positioning member 505 may be manipulable, for example by acting as a cam member. Figure 8 The rotating scale member 4" may be used with any of the intermediate scale positioning members described above.

[0097] exist Figure 8In the embodiment, the rotating scale member 4" differs from those described above in that it is configured with a first rigid surface 20 and a second rigid surface 21 engaging the first cam-shaped intermediate scale positioning member 503 and the second cam-shaped intermediate scale positioning member 504 (when the rotating scale member 4" is assembled to the intermediate scale positioning member), and a flexible member 22 engaging the third intermediate scale positioning member 505. Similar to the above embodiments, the rotating scale member 4" is press-fitted into the intermediate scale positioning member, whereby the flexible member 22 will be radially displaced in the space / hole 23 provided behind the flexible member 22, and will therefore push the rotating scale member 4" into engagement with the intermediate scale positioning members 503, 504, 505 via a reaction force, so that the body 7" of the rotating scale member automatically adopts (in other words, is radially positioned / biased to / constrained to) a default (predetermined) radial position relative to one or more intermediate scale positioning members, which in this embodiment is defined / controlled by the first rigid surface 20 and the second rigid surface 21. As will be appreciated, in alternative embodiments, the third intermediate scale positioning member may be omitted, and the flexible member 22 may engage an integral portion of the component 306 (e.g., a shaft or protruding pin) extending through the hole 14 in the rotating scale member 4". In alternative embodiments, in a manner similar to Figure 7 In an alternative embodiment, the third intermediate scale positioning member 505 may comprise a resilient compliant member, in which case the disc may be a fully rigid disc (ie, the flexible member 22 is replaced by a third rigid surface).

[0098] In the described embodiment, the rotating scale member 4 is an optical rotating scale member, but this need not necessarily be the case. For example, the rotating scale member may be a magnetic, inductive or capacitive rotating scale member. Furthermore, in the described embodiment, the rotating scale member 4 is a reflective optical rotating scale member (where light from the readhead is reflected back to the readhead by the scale, and where both the illumination and scale detection components of the readhead are on the same side of the scale).

[0099] However, this does not necessarily have to be the case, and the rotary scale member may be a transmissive rotary scale member.

[0100] In the described embodiment, the rotating scale member is an incremental rotating scale member. Accordingly, the scale track includes a series of periodically arranged features that can be read by the readhead 10 to provide a count of the relative position / movement of the rotating scale member and the readhead. As is common in the field of incremental encoder devices, the rotating scale member may include one or more reference marks that can be read by the readhead as it passes the readhead so that the readhead can identify a reference position on the rotating scale member. In the figures showing the rotating scale member (e.g., see Figure 2c , Figure 2d , Figure 2e ). In this case, the reference mark 9 is shown in the same track 8 as the incremental scale feature, but this need not be the case; the reference mark 9 may be provided in a separate track adjacent to the incremental scale track 8 (e.g., as shown in FIG. Figure 7 Of course, the rotary scale member may be an absolute rather than incremental rotary scale member, in which the scale track 8 includes features defining a series of unique absolute positions so that the absolute position of the rotary scale member and readhead can be determined on start-up without requiring relative movement of the rotary scale member and readhead.

[0101] In the embodiments described above, according to the main and first aspect of the invention, the rotary scale member is assembled to one or more intermediate scale positioning members after the intermediate scale positioning members have been manipulated into their desired radial configuration. This provides the operator / installer with a simple and effective way to compensate for any deviation between the axis of rotation and the geometric center of the component / shaft to which the rotary scale member is to be assembled. For example, manipulation (and any verification) of the radial configuration can be carried out without the rotary scale member being in position, which can make the manipulation (and any verification) of the radial configuration easier and can help avoid damage to the rotary scale member during manipulation (and any verification) of the radial configuration. Moreover, the ease of manufacture of the rotary scale member can be improved because it is not necessary to provide an accurate surface on the rotary scale member to verify the radial configuration.

[0102] According to a different second aspect of the invention, a rotating scale member may be assembled to one or more intermediate scale positioning members via resilient compliant members configured to radially position / fix the rotating scale member relative to the intermediate scale positioning members at a default (predetermined) radial position / location prior to or during manipulation (and any verification) of the radial configuration of the one or more intermediate scale positioning members. For example, the one or more intermediate scale positioning members may be mounted on a component of the device, the rotating scale member may then be assembled to the one or more intermediate scale positioning members (via resilient compliant members configured to radially position / fix the rotating scale member relative to the intermediate scale positioning members at a default (predetermined) radial position / location), and the radial configuration of at least one of the one or more intermediate scale positioning members may then be subsequently manipulated until the desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved. Alternatively, the rotating scale member may be fitted to the one or more intermediate scale locating members (via resilient compliant members configured to radially position / fix the rotating scale member at a default (predetermined) radial position / location relative to the intermediate scale locating members) prior to mounting the one or more intermediate scale locating members on the component. Although this second aspect of the invention does not have the above-mentioned benefits of the main and first aspects of the invention, the second aspect has benefits compared to the prior known techniques for mounting rotating scale members. In particular, the resilient compliant members may help the rotating scale member escape any significant form or shape deformation (which may otherwise be imposed on the rotating scale member via manipulation of the radial configuration of the one or more intermediate scale locating members) while ensuring that the rotating scale member self-positions / adopts a default (predetermined) radial position / location relative to the one or more intermediate scale locating members.

[0103] In the embodiments described above according to the first aspect of the invention, one or more intermediate scale positioning members are mounted on the first component before the rotating scale member is mounted on the intermediate scale positioning member (and therefore before the rotating scale member is placed on the first component). However, according to another aspect of the invention, the rotating scale member can be placed on the first component before the intermediate scale positioning member is mounted on the first component. Optionally, one or more of the intermediate scale positioning members may include one or more elastic compliant members, against which the rotating scale member engages, so that when the intermediate scale positioning member is mounted on the first component and engages with the rotating scale member, the rotating scale member is biased toward a default radial position relative to the intermediate scale positioning member (and therefore relative to the axis of rotation). The elastic compliant member may be formed integrally with the intermediate scale positioning member, may be formed separately and is provided for one or more intermediate scale positioning members.

[0104] In the embodiments described above, the elastic compliant member is provided for: the rotating scale member and / or one or more intermediate scale positioning members (formed integrally with the rotating scale member and / or one or more intermediate scale positioning members, or formed separately and attached / fastened to the rotating scale member and / or one or more intermediate scale positioning members). As will be appreciated, this need not necessarily be the case. For example, the elastic compliant member may be provided completely separately to the rotating scale member and the one or more scale positioning members. For example, the rotating scale member may be placed on a first component, the one or more intermediate scale positioning members may be mounted on the first component (in either order), and then the elastic compliant member may be positioned / placed between the rotating scale member and the one or more intermediate scale positioning members so as to engage both the rotating scale member and the one or more intermediate scale positioning members, thereby causing the rotating scale body to be radially positioned relative to the intermediate scale positioning members at a default radial position. The step of manipulating the radial configuration of at least one of the one or more intermediate scale positioning members may be performed before or after the elastic compliant member has been positioned / placed between the rotating scale member and the one or more intermediate scale positioning members. Furthermore, for example, the step of manipulating the radial configuration of at least one of the one or more intermediate scale positioning members may be performed before or after placing the rotary scale member on the first component.

[0105] As will also be understood, not all resilient compliant members are provided on the rotating scale member, or not all resilient compliant members are provided on the intermediate scale positioning member, or not all resilient compliant members are provided entirely separately, but combinations of the above options are possible (for example, at least one resilient compliant member may be provided on / by the rotating scale member, and / or at least one resilient compliant member may be provided on the intermediate scale positioning member, and / or at least one resilient compliant member may be provided entirely separately).

Claims

1. A method of mounting a rotary scale member on a first component of an apparatus, wherein: The first and second parts of the apparatus are relatively rotatable about a rotational axis, the rotating scale member comprising a body on which is or can be provided a series of scale features defining a scale extending about the scale axis, the method comprising: i) mounting one or more intermediate scale locating members on the first component and manipulating the radial configuration of at least one of the one or more intermediate scale locating members until a desired radial configuration of the one or more intermediate scale locating members relative to the rotational axis is achieved; and ii) subsequently fitting the rotary scale member to the one or more intermediate scale positioning members, whereby the body of the rotary scale member is radially positioned at a default radial position relative to the one or more intermediate scale positioning members.

2. The method of claim 1, comprising: iii) subsequently tightening the body of the rotary scale member so as to fix the radial position of the body of the rotary scale member relative to the component.

3. The method of claim 2, comprising: iv) subsequently removing the one or more intermediate scale positioning members.

4. A method as claimed in any preceding claim, wherein: Step i) comprises checking the radial configuration of at least one of the one or more intermediate scale positioning members.

5. The method of claim 4, wherein: The checking includes determining a position of at least a portion of the one or more intermediate scale locating members so as to determine a radial configuration of the one or more intermediate scale locating members.

6. A method as claimed in any preceding claim, wherein: The rotating scale member is mounted to the one or more intermediate scale positioning members via one or more resilient compliant members.

7. The method of claim 6, wherein: Step ii) comprises press-fitting the rotary scale member and the at least one intermediate scale positioning member together, whereby the one or more elastic compliant members are displaced and thereby push the rotary scale member into engagement with the one or more intermediate scale positioning members via a reaction force, so that the body of the rotary scale member is thereby radially positioned at the default radial position relative to the one or more intermediate scale positioning members.

8. A method as claimed in any preceding claim, wherein: Step i) comprises arranging separate intermediate scale locating members at at least two circumferentially spaced apart positions about the rotational axis on the component, at least one of the intermediate scale locating members being of a radial configuration manipulable independently of the other intermediate scale locating members.

9. The method according to any one of claims 1 to 7, wherein: Step i) comprises arranging on said component an integral intermediate scale locating member providing a surface for receiving said rotating scale member at at least three circumferentially spaced locations about said axis of rotation.

10. The method of claim 9, wherein: The integral intermediate scale locating member comprises an annular intermediate scale locating member including a substantially circular surface for receiving the rotating scale member.

11. A method as claimed in any preceding claim, wherein: The desired radial configuration of the one or more intermediate scale positioning members is one that ensures that, when the rotating scale member is assembled on the one or more intermediate scale positioning members in step ii), the scale axis and the axis of rotation of the component are substantially coaxial.

12. A method of mounting a rotary scale member on a first component of an apparatus, wherein: The first and second parts of the apparatus are relatively rotatable about a rotation axis, the rotating scale member comprising a body on which is or can be provided a series of scale features defining a scale extending about the scale axis, the method comprising, in any suitable order: i) installing one or more intermediate scale positioning members on the first component; ii) mounting the rotating scale member to the one or more intermediate scale positioning members via one or more resilient compliant members, the one or more resilient compliant members being configured to radially position the rotating scale member at a default radial position relative to the intermediate scale positioning member; iii) manipulating the radial configuration of at least one of the one or more intermediate scale locating members mounted on the first component until a desired radial configuration of the one or more intermediate scale locating members relative to the rotational axis is achieved; and iv) After steps i) to iii), tightening the body of the rotary scale member to fix the body of the rotary scale member relative to the radial position of the first component and then removing the one or more intermediate scale positioning members.

13. The method of claim 12, wherein: Step ii) is performed during or before step iii).

14. The method of claim 13, wherein: Step ii) is performed before or after step i).

15. The method of claim 12, wherein: The rotary scale member is placed on the first component at the following times: a) after the one or more intermediate scale locating members have been mounted on the first component, or b) simultaneously with mounting said one or more intermediate scale locating members on said first component.

16. The method according to any one of claims 12 to 15, wherein: Step iii) comprises checking the radial configuration of at least one of the one or more intermediate scale positioning members.

17. The method of claim 16, wherein: The checking includes determining a position of at least a portion of the one or more intermediate scale locating members so as to determine a radial configuration of the one or more intermediate scale locating members.

18. The method according to any one of claims 12 to 17, wherein: At least one of the one or more intermediate scale positioning members comprises the one or more resiliently compliant members against which the rotating scale member fits.

19. The method according to any one of claims 12 to 18, wherein: The elastically compliant member includes a flexible portion.

20. The method of any one of claims 12 to 19, wherein: The body of the rotary scale member comprises a planar disc, wherein the series of position features are provided on a planar surface of the planar disc.

21. A device comprising: one or more intermediate scale positioning members configured to be mounted on a first component of a device having the first and second components relatively rotatable about an axis of rotation, the one or more intermediate scale positioning members being configured to enable manipulation of a radial configuration of at least one of the one or more intermediate scale positioning members relative to the axis of rotation; a rotating scale member comprising a body on which is or can be provided a series of scale features defining a scale extending about a scale axis, the rotating scale member being mountable to the one or more intermediate scale positioning members such that a radial position of the rotating scale member relative to the rotation axis is controlled by the one or more intermediate scale positioning members, the rotating scale member being mountable to the one or more intermediate scale positioning members via one or more resiliently compliant members, the one or more resiliently compliant members being configured to radially position the rotating scale member relative to the intermediate scale positioning members at a default radial position when the rotating scale member is mounted to the one or more intermediate scale positioning members; as well as Means for securing the rotary scale member to the first component independently of the one or more intermediate scale locating members such that the radial position of the body of the rotary scale member is maintained after removal of the one or more intermediate scale locating members.

22. The apparatus of claim 21, wherein: The rotating scale member can be mounted to the one or more intermediate scale positioning members via at least three resiliently compliant members, the at least three resiliently compliant members being positioned at different positions, for example substantially equiangular positions, about the scale axis.

23. The apparatus of claim 21 or 22, wherein: The elastically compliant member includes a flexible portion.

24. The apparatus of any one of claims 21 to 23, wherein: The rotary scale member includes the elastic compliant member.

25. The apparatus of any one of claims 21 to 23, wherein: The one or more intermediate scale positioning members include one or more resiliently compliant members to which the rotating scale member is mounted.

26. Apparatus as claimed in any one of claims 21 to 25 configured so that the rotary scale member can be fitted to one or more intermediate scale locating members already mounted on the first part of the apparatus.

27. A method of mounting a rotary scale member on a first component of an apparatus, wherein: The first and second parts of the apparatus are relatively rotatable about a rotation axis, the rotating scale member comprising a body on which is or can be provided a series of scale features defining a scale extending about the scale axis, the method comprising, in any suitable order: i) installing one or more intermediate scale positioning members on the first component; ii) engaging the rotating scale member and the one or more intermediate scale positioning members with each other via one or more resilient compliant members; iii) manipulating the radial configuration of at least one of the one or more intermediate scale locating members mounted on the component until a desired radial configuration of the one or more intermediate scale locating members relative to the rotational axis is achieved; and iv) After steps i) to iii), tightening the body of the rotary scale member to fix the radial position of the body of the rotary scale member relative to the first component, and then removing the one or more intermediate scale positioning members.

28. The method of claim 27, wherein: At least one of the one or more intermediate scale positioning members comprises at least one of the one or more resiliently compliant members.

29. The method of claim 27 or 28, wherein: Step ii) is performed before or during step iii).

30. The method of any one of claims 27 to 29, wherein: Step ii) is performed before step i).

31. An apparatus comprising: a rotating scale member comprising a body on which is disposed or capable of being disposed a series of scale features defining a scale extending about a scale axis; one or more intermediate scale positioning members configured to be mounted on a first component of a device having the first and second components relatively rotatable about a rotational axis such that a radial configuration of at least one of the one or more intermediate scale positioning members can be manipulated relative to the rotational axis, wherein at least one of the one or more intermediate scale positioning members includes one or more resiliently compliant members against which the rotating scale member is engageable such that the rotating scale member is biased toward a default radial position relative to the one or more intermediate scale positioning members; as well as Means for securing the rotary scale member to the component independently of the one or more intermediate scale locating members such that the radial position of the body of the rotary scale member is maintained after removal of the one or more intermediate scale locating members.

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