How to install rotary scale components

Abstract

A method of mounting a rotary scale member to a part, the part being rotatable about an axis of rotation, the rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending about the scale axis, the method comprising i) mounting one or more intermediate scale positioning members to the part and manipulating a radial configuration relative to the axis of rotation until a desired radial configuration is achieved, and ii) then mounting the rotary scale member to the one or more intermediate scale positioning members, whereby the body of the rotary scale member adopts a default radial position relative to the one or more intermediate scale positioning members.

Description

[Technical field]

[0001] The present invention relates to a method of mounting a rotary scale member to a piece of equipment, such as a machine, for use with a rotary encoder. [Background technology]

[0002] Measuring scales are used to measure the position of relatively movable parts of a device, for example a relatively movable part of a machine. A measuring scale typically has a series of features that are read by a readhead, which gives a measurement of its position along or around the scale. The measuring scale can be attached to one part of the device and is read by a suitable readhead attached to another part of the device. The relative movement between two parts of the device can be measured by the readhead. Types of measuring scales include magnetic scales (wherein the scale features are provided by features with specific magnetic properties), capacitive scales (wherein the features are provided by features with specific capacitive properties), inductive scales (wherein the features are provided by features with specific inductive properties) and optical scales (wherein the features are provided by features with specific optical properties). Optical scales can be transmissive or reflective. Examples of optical scale configurations are disclosed in US Pat. No. 5,399,233 and US Pat. No. 5,499,253.

[0003] To measure the relative rotational displacement of the parts of the apparatus about an axis of rotation, a scale may be provided on a rotary scale member attached to one of the parts of the apparatus and a readhead configured to read the scale may be provided on the other part. Typically the rotary scale member is in the form of a disk scale member or a ring scale member. In either case the rotary scale member may comprise a body on which is or can be provided a series of scale features defining a scale extending about the scale axis. Typically the rotary scale member is attached to the part of the apparatus which rotates, while the readhead is attached to the stationary part of the apparatus, although this does not necessarily have to be the case and may be reversed.

[0004] FIG. 1 shows a prior art arrangement of an encoder device 2 (described in more detail in US Pat. No. 5,399,633) comprising a rotary scale member 4, which is a disk scale member, and a read head 10. The read head 10 is mounted to a fixed part 12 of the device and the disk scale member 4 is mounted to a shaft 6' of a part 6 of the device, which is rotatable about a rotation axis A. The disk scale member 4 comprises a substantially planar body 7 having a scale track 8 in one of its planes, extending completely annularly around the scale axis S. The scale track 8 comprises a series of features which the read head 10 (mounted to a fixed part 12 relative to the cylindrical shaft 6) can read to determine the relative position / movement of the disk scale member 4 and the read head 10. A hole 14 is provided through the centre of the planar body 7, allowing the cylindrical shaft 6' to extend through the body when the disk scale member 4 is mounted on the cylindrical shaft 6'. The disk scale member 4 further comprises three pairs of resilient compliant members (cantilever springs / flexure members in this embodiment) 16 spaced around the edge of the hole 14 for engaging the cylindrical shaft 6' when inserted onto the cylindrical shaft 6' and radially positioning the disk scale member 4 relative to the cylindrical shaft 6'.

[0005] The three pairs of cantilever spring members 16 define a predetermined inner diameter of the hole 14 that is smaller than the diameter of the shaft 6'. The disk scale member 4 must therefore be press-fitted onto the shaft 6', whereby the shaft 6' engages the side of each of the cantilever spring members 16 that faces the center of the hole 14, bending each of them slightly radially outward. The elasticity of the material of the cantilever spring members 16 induces a radial reaction force on the shaft 6', thereby creating a radial self-positioning effect. If the reaction force exerted by each cantilever spring member 16 is nominally the same, the disk scale member 4 will nominally be self-centered on the shaft 6'. Thus, if it is desired that the scale axis S and the axis of rotation A are substantially coaxial, the disk scale member 4 must be configured such that the scale axis S is at the point / axis about which the cantilever spring members 16 center the disk scale member.

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

[0007] 1, even with such self-positioning (e.g., self-centering) features, and despite best efforts to manufacture the rotary scale member 4 and shaft 6' as accurately as possible, the relative position of the rotation axis A and the scale axis S may not be as intended / desired (e.g., not coaxial), which may lead to measurement errors if not corrected and / or compensated for. For example, in an embodiment where the scale axis S and the rotation axis A are coaxial and it is desired that the cantilever spring member 16 is configured to self-center the disk scale member 4, it is highly likely that there will be at least some offset between the rotation axis A and the scale axis S. Often this is at least primarily due to the geometric centers of the rotation axis A and the shaft 6' not coinciding. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent Publication No. 0207121 [Patent Document 2] U.S. Patent No. 4,926,566 [Patent Document 3] International Publication No. 2021-116660 [Patent Document 4] European Patent Publication No. 1094302 [Patent Document 5] International Publication No. 2004-008076 Summary of the Invention

[0009] It is therefore known to adjust the rotary scale member after it has been mounted on the apparatus, as described in US Pat. No. 5,399,623 and US Pat. No. 5,499,623. The present invention provides an effective alternative technique for improving the mounting of a rotary scale member on a piece of apparatus.

[0010] According to a first aspect of the present invention, there is provided a method of mounting a rotary scale member to a first part of an apparatus, the first part and a second part of the apparatus being relatively rotatable about an axis of rotation, the rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending about a scale axis, the method comprising the steps of: i) mounting one or more intermediate scale positioning members to the first part 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) then mounting 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 (i.e. "predetermined") radial position relative to the one or more intermediate scale positioning members.

[0011] As will be appreciated, the one or more intermediate scale positioning members control / direct the radial placement / position of the rotary scale member attached thereto relative to the first portion of the apparatus. Thus, the one or more intermediate scale positioning members may be referred to as one or more intermediate radial scale positioning members, but for brevity are referred to herein as intermediate scale positioning members. As will be appreciated, the one or more intermediate scale positioning members may be directly attached to the first portion of the apparatus or may be indirectly attached to the first portion of the apparatus (e.g., via another member / device, such as a support member / device that is itself directly attached to the first portion of the apparatus).

[0012] Advantages of the method of the present invention may include an increased ease of manufacture of the rotary scale member and / or a reduced risk of damage to the scale-carrying portion of the rotary scale member, as compared to known techniques that allow for radial adjustment. For example, the present invention does not require the rotary scale member to be provided with features that facilitate radial adjustment of itself, thereby simplifying the rotary scale member and its manufacture. Furthermore, there is no need to inspect the radial configuration of the rotary scale member, as it is the intermediate scale positioning member that is manipulated until the desired radial configuration is achieved. This may provide advantages in its ease of manufacture (as there is no need to provide an accurate reference surface thereon for inspection) and / or may reduce / avoid the risk of damage to the rotary scale member that may be caused by such inspection.

[0013] As will be understood, and as described in more detail below, the rotary scale member and the one or more intermediate scale positioning members interact with each other (e.g., their mechanisms interact with each other) to radially position the rotary scale member in a default (predetermined) radial arrangement / position relative to the one or more intermediate scale positioning members.

[0014] As will be appreciated, in accordance with the present invention, the attachment of a rotary scale member to one or more intermediate scale positioning members can be said to automatically radially position the radial position of the body of the rotary scale member at said default radial position. The body of the rotary scale member can be said to (automatically) accept (or "accept") or in other words "consider" and for example "stop" at a default (predetermined) radial position with respect to the one or more intermediate scale positioning members, or for example be "radially biased" to a radial position or "radially restrained" at a radial position.

[0015] As will be appreciated, a default (predetermined) radial arrangement / position may be a radial position to which the body of the rotary scale member naturally / automatically rests (and returns to) relative to the one or more intermediate scale positioning members when there is no radial external force acting thereon (or any external force is removed). The default (predetermined) radial arrangement / position may be referred to as a repeatable radial arrangement / position (i.e., it is repeatable with respect to the one or more intermediate scale positioning members).

[0016] The apparatus may be a machine. Thus, a first part of the apparatus to which the rotary scale member is attached may be a part of the machine. The apparatus may include an encoder mount (e.g., which is then attached to another device), for example, the apparatus may include a housing for an enclosed encoder apparatus. Thus, the first part may include a part of a housing for an enclosed encoder apparatus.

[0017] The first part may be a part of the apparatus that is configured to rotate around said axis of rotation during use / operation and the second part may be configured to remain stationary / rotationally fixed around said axis of rotation. This is preferred as the readhead for reading the scale of the rotary scale member may be mounted on the stationary / rotationally fixed part which may be easier from an assembly / cabling point of view. However, this does not necessarily have to be the case and the second part may be a part of the apparatus that rotates around said axis of rotation during use / operation and the first part (to which the rotary scale member is mounted) may remain stationary / rotationally fixed around said axis of rotation.

[0018] The body of the rotary scale member may include an annular body. The body, e.g. annular body, may include a planar disk. Optionally, the planar disk is 5 mm or less thick, e.g. 3 mm or less thick, e.g. about 1 mm thick. A series of position (scale) features may be provided on a plane of the body of the rotary scale member (e.g. on a plane of the planar disk) (as opposed to an axially extending peripheral edge typically associated with a ring scale / encoder). Thus, the rotary scale member may comprise (e.g. for a disk encoder) a disk scale member (which may also be interchangeably referred to as a scale disk member). The disk scale member includes a flat surface on which is or may be provided a series of scale features defining a scale, the scale axis extending perpendicular to the flat surface. Thus, the scale features may be radially extending scale features. For example, the scale features may be radially elongated, e.g. each scale feature may include a line extending radially (relative to the scale axis). In an alternative embodiment, the rotary scale member comprises a ring scale member having a series of location features provided on an axially extending peripheral edge of the body.

[0019] The body of the rotary scale member may comprise a metallic material, although it will be appreciated that other non-metallic materials may also be used.

[0020] The scale may include optical, capacitive, inductive and / or magnetic scale features. As will be understood, "light" and "optical" herein encompass electromagnetic radiation (EMR) at any wavelength from infrared to ultraviolet. In particular, in the case of optical scale features, the scale may be a reflective or transmissive scale.

[0021] Preferably, the track of scale features includes a complete circular track of scale features (e.g., not just includes a partial arc). The scale features within a track may include incremental scale features (with or without one or more reference marks) or absolute scale features. A rotary scale member may include multiple series of scale features (e.g., multiple tracks).

[0022] The method may additionally include the step of iii) subsequently fixing the body of the rotary scale member to fix its radial arrangement / position relative to the first part of the apparatus. This may be achieved by fixing the body of the rotary scale member to the first part of the apparatus. This may be achieved via one or more mechanical fasteners (e.g. one or more bolts and / or clamps) and / or adhesives. Preferably, the body of the rotary scale is fixed / attached to the first part of the apparatus with the body of the rotary scale in the default radial position located in step ii) (i.e. not moving radially away from said default radial position prior to the fixing step iii). Of course, additional fine adjustments of the radial position of the body of the rotary scale member may be made before being fixed / attached away from the default radial position located in step ii), but this is generally undesirable and negates at least some of the advantages of the invention.

[0023] The method may further include the step of iv) removing the one or more intermediate scale positioning members. As will be appreciated, the body of the rotary scale member may maintain its radial arrangement / position since it has been fixed to fix its radial arrangement / position in step iii). The step of removing the one or more intermediate scale positioning members may provide an advantage that the one or more intermediate scale positioning members may be reused. Removing the one or more intermediate scale positioning members may also provide an advantage in terms of reducing the mass of the first part of the apparatus and / or improving space / access of the first part (e.g., once removed, the one or more intermediate scale positioning members no longer occupy space, thus allowing more space / better access for other components).

[0024] Step i) may comprise checking a radial configuration of at least one of the one or more intermediate scale positioning members. This may comprise determining a (e.g. radial) position of at least a portion / surface / feature of the one or more intermediate scale positioning members to determine its radial configuration. In particular, step i) may comprise determining (and e.g. directly measuring) a (e.g. radial) position of that / surface / feature(s) of the one or more intermediate scale positioning members configured to engage the rotary scale member for attachment thereto.

[0025] The above-mentioned step of determining the (e.g. radial) position of at least a part / surface / feature of the one or more intermediate scale positioning members may comprise measuring the (e.g. radial) position of at least a part / surface / feature of the one or more intermediate scale positioning members in a plane extending perpendicular to the axis of rotation (and may comprise, for example, directly measuring the position of (those) parts / surfaces / features of the one or more intermediate scale positioning members that the rotary scale member is configured to matingly engage thereon in said plane extending perpendicular to the axis of rotation). Determining / measuring the position may comprise determining / measuring the radial position (e.g. relative to the axis of rotation) of at least a part / feature / surface of the one or more intermediate scale positioning members.

[0026] Checking / determining / measuring the position may include using an inspection tool / sensor. Checking / determining / measuring the position may include, for example, directly measuring the (e.g., radial) position of that / their portion / surface / feature(s) of the one or more intermediate scale positioning members configured to engage the rotary scale member for attachment thereto. The inspection tool / sensor may comprise a contact tool / sensor that contacts a portion / surface / feature (e.g., an axially extending portion / surface) of the one or more intermediate scale positioning members. The inspection tool / sensor may include a non-contact tool / sensor (e.g., obtaining such measurements without contacting the one or more intermediate scale positioning members).

[0027] Step i) may comprise determining the change / difference in apparent radius of at least a portion / surface / feature of the one or more intermediate scale positioning members relative to the axis of rotation at at least three different annularly spaced positions (i.e. different spaced positions around the axis). Such measurements at the different annularly spaced positions may be obtained by keeping an inspection tool / sensor in a fixed rotational position about the axis of rotation and rotating the one or more intermediate scale positioning members about the axis of rotation such that the inspection tool / sensor is able to obtain measurements at the different annularly spaced positions of the one or more intermediate scale positioning members.

[0028] The above measurements may be performed / taken whilst the first part of the apparatus and one or more intermediate scale positioning members attached thereto are rotating (if the first part is a rotatable part of the apparatus) or may be performed / taken whilst the first part of the apparatus and one or more intermediate scale positioning members attached thereto are stationary.

[0029] The rotary scale member and the one or more intermediate scale positioning members may be configured to engage with each other at at least two, preferably at least three engagement positions (e.g., regions) annularly spaced about the axis of rotation. The at least two, preferably at least three engagement positions may be predetermined engagement positions (regions). The (e.g., predetermined) at least two, preferably at least three engagement positions (regions) may be annularly spaced (e.g., substantially equiangularly) about the axis of rotation. It has been found that three or four engagement positions (regions) substantially equiangularly arranged are preferred. The method may include determining (e.g., radial) positions of at least two, preferably at least three engagement positions (regions) of the one or more intermediate scale positioning members to determine their radial configuration. As will be appreciated, and as will be described in more detail below, at any given engagement position (region), there may be multiple contact points between the rotary scale member and the one or more intermediate scale positioning members. For example, in an embodiment where the individual mounting mechanisms include a pair of cantilevered spring members whose free ends are proximate to each other, there are two contact points at the engagement position, one on each cantilevered spring member. Nevertheless, even if there are more than one contact points between the rotary scale member and the intermediate scale positioning member or members at any given engagement position, it may be sufficient for only one measurement of the (radial) position of the engagement position (area) to be performed, although of course more than one measurement can be performed if desired.

[0030] At least one of the engagement positions may be a rigid engagement position (e.g., provided by rigid (e.g., radially) non-compliant features / surfaces of the rotary scale member and the one or more intermediate scale positioning members). At least one of the engagement positions may be an elastically-compatible engagement position (e.g., provided by an elastically-compatible member provided on the rotary scale member and / or the one or more intermediate scale positioning members, as described in more detail below). A combination of rigid and elastically-compatible engagement positions may be provided. The elastically-compatible engagement positions may be configured such that the body of the rotary scale member is biased to / against the rigid engagement position(s) by the elastically-compatible engagement positions, whereby the rigid engagement position(s) define a default radial position of the body of the rotary scale member relative to the one or more intermediate scale positioning members. In a particular example, at least two of the engagement positions may be rigid engagement positions and at least one of the engagement positions may be an elastically-compatible engagement position. For example, as will be described by way of example in more detail below in connection with FIG. 8, two of the engagement positions may be rigid engagement positions and one of the engagement positions may be a resiliently adapted engagement position. In other embodiments, all of the engagement positions may be resiliently adapted engagement positions (e.g., as will be described in more detail below in connection with FIGS. 2-7). It has been found that three or four substantially equiangularly spaced engagement positions (areas) are preferred. As will be described in more detail below, the resiliently adapted engagement positions may be provided by one or more resiliently adapted members (e.g., a single flexure, or multiple, e.g., a pair of flexures / cantilever spring members acting together).

[0031] The rotary scale member (and / or the one or more intermediate scale positioning members) may comprise a plurality of separate mounting mechanisms configured in step ii) for the rotary scale member and the one or more intermediate scale positioning members to engage with each other at at least two, preferably at least three (predetermined) engagement positions spaced annularly around the axis of rotation. The separate mounting mechanisms may comprise rigid or resiliently compliant mechanisms / members.

[0032] The rotary scale member may be attached to the one or more intermediate scale positioning members via one or more resilient compliant members, e.g. at least two, and in some examples preferably three out of four (or pairs thereof), provided at annularly spaced positions around the scale axis. The one or more resilient compliant members may be configured to radially position the rotary scale member in said default (predetermined) radial arrangement / position relative to the intermediate scale positioning member. Such one or more resilient compliant members may include radial and / or tangential compliant members.

[0033] The separate mounting features of the rotary scale members may comprise resilient compliant members (eg radial and / or tangential).

[0034] In any embodiment, the intermediate scale positioning member or members may include a separate mounting mechanism, for example a resilient compliant member, to which the rotary scale member is attached.

[0035] The separate mounting mechanism (particularly the separate mounting mechanism including the resilient compliant member) may include a spring member, e.g., a flexure member, e.g., a cantilever spring member. Thus, for example, the rotary scale member may include at least three spring members (e.g., flexures, e.g., cantilever spring members). The separate mounting mechanism may include multiple mounting mechanisms acting together / as one, e.g., the separate mounting mechanism may include multiple (e.g., pairs) (e.g., cantilever) spring members configured to provide a common spring force (e.g., in magnitude and direction) between the intermediate scale positioning member or members and the body of the rotary scale member. Thus, for example, the rotary scale member may be attached to the intermediate scale positioning member or members via at least three pairs (e.g., cantilever) spring members (e.g., the rotary scale member may include). The pair of cantilever spring members may extend in opposite directions from one another such that the free ends of the pair of cantilever spring members are proximal to one another (e.g., sufficiently proximal that they can be considered to engage with one or more intermediate scale positioning members at substantially the same engagement position, and may be configured to provide substantially the same spring force (e.g., in magnitude and direction).

[0036] The separate mounting mechanism (e.g., the elastic compliant member) may be formed integrally with the body of the rotary scale member (or integrally with the one or more intermediate scale positioning members). While this may be desirable, it is not required. For example, the separate mounting mechanism (e.g., the elastic compliant member) may be formed separately from the body of the rotary scale member and formed separately from the one or more intermediate scale positioning members. In such a case, the separate mounting mechanism (e.g., the elastic compliant member) may comprise (e.g., be fixed to) the body of the rotary scale member or comprise (e.g., be fixed to) the one or more intermediate scale positioning members (or a combination thereof). Alternatively, the separate mounting mechanism (e.g., the elastic compliant member) may be provided separately from the rotary scale member and separately from the one or more intermediate scale positioning members and inserted therebetween (e.g., after the rotary scale member and the one or more intermediate scale positioning members have already been positioned / attached to the first portion). In preferred embodiments, a separate mounting mechanism (e.g., a resilient compliant member) is provided on / by the rotary scale member (as opposed to being provided on / by one or more intermediate scale positioning members, or completely separate from the rotary scale member and one or more intermediate scale positioning members), and in particularly preferred embodiments the separate mounting mechanism (e.g., a resilient compliant member) is integrally formed with the body of the rotary scale member.

[0037] As will be appreciated, all of the discrete attachment features (e.g., resilient compliant members) may be provided on / by the rotary scale member, or all of the discrete attachment features (e.g., resilient compliant members) may be provided on / by the intermediate scale positioning member, or the separate attachment features (e.g., resilient compliant members) may be provided via any combination of the rotary scale member, the intermediate scale positioning member(s), and being provided completely separately and interposed between the rotary scale member and the intermediate scale positioning member(s) after both are positioned on the first portion.

[0038] The separate attachment mechanism (e.g., resilient compliant members) may be provided radially inward of the series of scale features. In an alternative embodiment, the separate attachment mechanism (e.g., resilient compliant members) may be provided radially outward of the series of scale features.

[0039] The method can include press-fitting the rotary scale member and the at least one intermediate scale positioning member together. The rotary scale member and the one or more intermediate scale positioning members can be configured such that the action of press-fitting the rotary scale member and the at least one intermediate scale positioning member together moves one or more (e.g., at least two, and in some examples preferably three out of four) resilient compliant members (or pairs thereof) to thereby bring the rotary scale member into engagement with the one or more intermediate scale positioning members via a (e.g., radial) reaction force, and a body of the rotary scale member is radially disposed (e.g., received / rested / biased) in a default (predetermined) radial arrangement / position relative to the one or more intermediate scale positioning members.

[0040] Step i) may include disposing separate intermediate scale positioning members in the first part of the apparatus at at least two, e.g., at least three (e.g., substantially equiangular) annularly spaced positions about the axis of rotation, at least one radial configuration of which may be manipulated independently of the other(s) (and e.g., each radial configuration may be independently manipulated). In an alternative embodiment, in contrast to using such multiple (e.g., separate) intermediate scale positioning members, whose radial configurations may be independently manipulated, step i) may include disposing a single intermediate scale positioning member in the first part of the apparatus that provides a surface for receiving the rotary scale member at at least three (e.g., substantially equiangular) annularly spaced positions about the axis of rotation. As will be appreciated, a single intermediate scale positioning member may be comprised of multiple parts / components. A single intermediate scale positioning member comprised of multiple parts / components may, for example, be treated as one unit / member and, for example, may be located in the first part of the apparatus as one unit. The single intermediate scale positioning member may comprise, for example, an annular intermediate scale positioning member with a (continuous) annularly extending surface on which the rotary scale member is configured to be mounted at at least three (e.g. substantially equiangularly) annularly spaced positions around the axis of rotation. The continuous surface need not have a regular cross-sectional shape (viewed perpendicular to the axis of rotation / scale). In an embodiment, the annular intermediate scale positioning member may comprise a substantially circular intermediate scale positioning member that extends around the axis of rotation when mounted on the first part of the apparatus, such as a ring or disk-like intermediate scale positioning member. Thus, the annular single intermediate scale positioning member may comprise a substantially circular surface that extends around the axis of rotation when mounted on the first part of the apparatus for receiving the rotary scale member. The single intermediate scale positioning member may be configured such that manipulation of the radial configuration of the single intermediate scale positioning member causes all radial configurations of at least three annularly spaced positions where the radial configurations are manipulated around the same time / simultaneously.

[0041] Step i) may include inspecting an axially extending surface of the one or more intermediate scale positioning members to determine a radial configuration of the one or more intermediate scale positioning members. The axially extending surface may include an 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 (viewed perpendicular to the rotation / scale axis). When mounted to the first part of the apparatus, the axially extending surface of the intermediate scale positioning member may extend substantially parallel to the rotation axis. The axially extending surface may have, for example, a substantially cylindrical shape. In alternative embodiments, the axially extending surface may have a non-cylindrical shape, for example a substantially frusto-conical shape, or a substantially frusto-conical shape.

[0042] The desired radial configuration of the one or more intermediate scale positioning members may be a configuration that ensures that when the rotary scale member is attached thereto in step ii), the scale axis and rotation axis of the first part of the apparatus are in a desired positional relationship, e.g. substantially coaxial.

[0043] As discussed above, the rotary scale member and the one or more intermediate scale positioning members may be configured to engage with one another at at least two, and preferably at least three, engagement locations (e.g., regions) spaced annularly about the axis of rotation. A desired radial configuration may be one in which the center points of the at least three engagement locations are substantially coincident with the axis of rotation.

[0044] As will be appreciated, the scale features may be read by a readhead. Thus, the method may further include, at any suitable stage, mounting a readhead to a second part of the apparatus (e.g. machine) configured to read the scale features of the rotary scale member. Thus, the method may include a method of assembling or mounting an encoder, the encoder comprising a rotary scale member as described above and / or below, and a readhead.

[0045] According to a second aspect of the present invention, there is provided a method of mounting a rotary scale member to a first part (e.g. a machine part) of an apparatus, the first part and a second part of the apparatus being relatively rotatable about a rotation axis, the rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending about the scale axis, the method comprising the steps of: ii) mounting one or more intermediate scale positioning members to the first part of the apparatus in any suitable order; ii) mounting the rotary scale member to said one or more intermediate scale positioning members via (e.g. one or more) resilient compliant members configured to (automatically) radially position / position the rotary scale member in a default (predetermined) radial position / position relative to the intermediate scale positioning members; and iii) manipulating at least one radial configuration of the one or more intermediate scale positioning members mounted to the first part until a desired radial configuration of the one or more intermediate scale positioning members relative to the rotation axis is achieved. An advantage of this aspect of the invention is that the (e.g. one or more) resilient compliant members can help isolate the rotary scale member from any significant form or shape deformation that may be imparted to the rotary scale member (in the absence of such resilient compliant members) through manipulation of the radial configuration of the one or more intermediate scale positioning members, whilst ensuring that the rotary scale member (automatically) self-positions / accepts a default (predetermined) radial arrangement / position relative to the one or more intermediate scale positioning members. Following steps i)-iii), the method may comprise fixing the body of the rotary scale member to fix its radial position relative to the first part of the apparatus and then removing the one or more intermediate scale members.

[0046] As will be appreciated, according to this aspect of the invention, step ii) may occur during or before step iii), and further, according to this aspect of the invention, step ii) may occur before or after step i).

[0047] Step iii) may include checking a radial configuration of at least one of the one or more intermediate scale positioning members. The checking may include determining a position of at least a part of the one or more intermediate scale positioning members to determine the radial configuration of the one or more intermediate scale positioning members. In those embodiments in which a rotary scale member is attached to the one or more intermediate scale positioning members before or while at least one of the one or more intermediate scale positioning members is manipulated to a desired radial configuration, the radial configuration of the one or more intermediate scale positioning members may be determined / checked by inspecting the one or more intermediate scale positioning members and / or the rotary scale member.

[0048] The rotary scale member may be disposed on the first portion a) after the one or more intermediate scale positioning members are attached to the first portion, or b) when the one or more intermediate scale positioning members are attached to the first portion (i.e., the rotary scale member may be attached to the one or more intermediate scale positioning members before they are attached together to the first portion. In other words, optionally, the rotary scale member is not attached to the first portion before the one or more intermediate scale positioning members are attached to the first portion.

[0049] As will be appreciated, the features described above in relation to the first aspect of the invention are equally applicable to this aspect of the invention. Thus, for example, mounting the rotary scale to the one or more intermediate scale members may include press-fitting them together, whereby the (e.g. one or more) elastically compliant mounting features move, whereby a reaction force urges the rotary scale member into engagement with the one or more intermediate scale positioning members, such that the body of the rotary scale member is radially disposed (e.g. receives / rests / is biased) in a default (predetermined) radial disposition / position relative to the one or more intermediate scale positioning members. As described above in relation to the first aspect of the invention, the rotary scale member may include one or more elastically compliant members, and the one or more intermediate scale positioning members may include one or more elastically compliant members to which the rotary scale member is attached, and the elastically compliant members may be provided completely separate from the rotary scale member and the intermediate scale positioning member(s), or any combination of the above options is possible. The elastically compliant members may include flexures. The body of the rotary scale member may include a planar disk, with the series of location features provided on a plane of the planar disk.

[0050] According to a third aspect of the present invention, there is provided an apparatus comprising one or more intermediate scale positioning members mountable to a first part (e.g. a machine part) of a device having a first part and a second part relatively rotatable about a rotation axis, configured such that at least one radial configuration of the one or more intermediate scale positioning members is operable relative to the rotation axis, the apparatus comprising: a rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending about the scale axis, the rotary scale member being adaptable to the one or more intermediate scale positioning members via one or more resilient compliant members such that a radial position of the rotary scale member relative to the rotation axis is controlled / indicated by the one or more intermediate scale positioning members, the rotary scale member comprising a body and a member configured to (automatically) radially position the rotary scale member in a default (predetermined) radial arrangement / position relative to the intermediate scale positioning members when the rotary scale member is mounted to said one or more intermediate scale positioning members. The apparatus may further comprise means (e.g., mechanical fasteners and / or adhesive) for fixing the rotary scale member to the first portion of the device independently of the one or more intermediate scale positioning members, for example so that the one or more intermediate scale positioning members can then be removed.

[0051] As will be appreciated, the features described above in relation to the first and second aspects of the invention are equally applicable to the third aspect of the invention. For example, the (e.g. one or more) elastically compliant members may comprise radially and / or tangentially compliant members. As described above in relation to the first aspect of the invention, the rotary scale member may comprise one or more elastically compliant members, and the one or more intermediate scale positioning members may comprise one or more elastically compliant members to which the rotary scale member is attached, the elastically compliant members may be provided completely separate from the rotary scale member and the intermediate scale positioning member(s), or any combination of the above options is possible. The rotary scale member may be compliant with the one or more intermediate scale mounting members via at least three different elastically compliant members, arranged, for example, at substantially equiangular positions around the scale axis. The elastically compliant members may comprise flexures. The rotary scale member may be attached to the one or more intermediate scale positioning members such that the radial arrangement / position of the rotary 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 include at least a first portion of the device (and optionally a second portion of the device), where one or more intermediate scale positioning members may be attached to the first portion of the device. The apparatus may include a readhead (e.g., attached to the second portion of the device) for reading the scale features. As will be appreciated, the apparatus may be configured such that the rotary scale member may be attached to one or more intermediate scale positioning members already attached to the first portion of the device.

[0052] According to a fourth aspect of the present invention, there is provided a method of mounting a rotary scale member to a first part of an apparatus, the first part and a second part of the apparatus being relatively rotatable about a rotation axis, the rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending about a scale axis, the method comprising the steps of: i) mounting, in any suitable order, one or more intermediate scale positioning members to the first part, at least one of which includes at least one resilient compliant member; ii) connecting the rotary scale member and the one or more intermediate scale positioning members via the one or more resilient compliant members; and the intermediate scale positioning member of the rotary scale member (thereby positioning the rotary scale member in 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 positioning members attached to the part such that a desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved; and iv) after steps i)-iii), fixing the body of the rotary scale member to fix its radial position relative to the first part and then removing the or a plurality of 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 relation to 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 rotary scale member may be positioned on the first part before steps i) and ii). As will be appreciated, the features described above in relation to the first, second and third aspects of the invention are equally applicable to the fourth aspect of the invention.

[0053] According to a fifth aspect of the invention, there is provided an apparatus comprising a rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending around a scale axis, one or more intermediate scale positioning members configured for attachment to a first part of a device having a first part and a second part relatively rotatable about the axis of rotation, a radial configuration of at least one of the one or more intermediate scale positioning members can be manipulated relative to the axis of rotation, at least one of the one or more intermediate scale positioning members including one or more resilient compliant members with which the rotary scale member can engage (and thereby attached to the one or more intermediate scale positioning members), means for fixing the rotary scale member such that the rotary scale member is biased towards a default radial position relative to the intermediate scale positioning members, and said part independent of the one or more intermediate scale positioning 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 positioning members. As will be appreciated, the features described above in relation to the first, second and third aspects of the invention are equally applicable to the fourth aspect of the invention.

[0054] The present application also describes a rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending around a scale axis, and a resilient compliant member (e.g., a flexure) for radially urging the body in a predetermined radial direction (e.g., in a radial direction) against one or more rigid stop surfaces provided by the rotary scale member. As will be appreciated, the resilient compliant member and the one or more rigid stop surfaces may be configured to engage with one or more features of a first part (e.g., a machine part) of an apparatus, the first part and the second part of the apparatus being relatively rotatable about the axis of rotation, and / or to engage with one or more intermediate (scale positioning) members attached to such first part of the apparatus (e.g., a machine). Such a configuration can provide highly repeatable positioning of the body of the rotary scale member relative to the part of the apparatus to which it is attached. Thus, a method of mounting a rotary scale member on a first part of the device (the first part being rotatable relative to a second part of the device about an axis of rotation) can include adapting the rotary scale member to a feature provided on the first part of the device (such a feature can be integrated in the first part, e.g., the shaft itself or can be an intermediate scale positioning member as described herein), whereby the elastically adapting member moves, thereby urging one or more rigid stop surfaces to engage with the feature provided on the first part of the device via a reaction force, such that the body of the rotary scale member is (automatically) positioned (e.g., to receive / bias) at 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 adapting member and the one or more rigid stop surfaces can be provided radially inward of the scale, e.g., around the edge of a hole extending axially through the body of the rotary scale member. The rotary scale member can comprise a disk scale member. The resilient compliant member may be integrally formed with a body of the rotary scale member. The resilient compliant member may include a leaf spring.The resiliently flexible member may include one or more cantilever spring members. [Brief description of the drawings]

[0055] Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which: [Figure 1] FIG. 1 shows a prior art arrangement of an encoder device which includes a self-positioning (specifically, self-centering) rotary scale member mounted on the shaft of the device. [Figure 2a] FIG. 2a shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a first embodiment of the invention. [Figure 2b] FIG. 2b shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a first embodiment of the invention. [Figure 2c] FIG. 2c shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a first embodiment of the invention. [Figure 2d] FIG. 2d shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a first embodiment of the invention. [Figure 2e] FIG. 2e shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a first embodiment of the invention. [Figure 3a] FIG. 3a shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a second embodiment of the invention. [Figure 3b] FIG. 3b shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a second embodiment of the invention. [Figure 3c] FIG. 3c shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a second embodiment of the invention. [Figure 3d] FIG. 3d shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a second embodiment of the invention. [Figure 4a] FIG. 4a shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a third embodiment of the invention. [Figure 4b] FIG. 4b shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a third embodiment of the invention. [Figure 4c] FIG. 4c shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a third embodiment of the invention. [Figure 4d] FIG. 4d shows an apparatus and the steps involved in mounting a rotary scale member on a piece of apparatus according to a third embodiment of the invention. [Figure 5a] FIG. 5a shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a fourth embodiment of the present invention. [Figure 5b] FIG. 5b shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a fourth embodiment of the present invention. [Figure 5c] FIG. 5c shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a fourth embodiment of the present invention. [Figure 5d] FIG. 5d shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a fourth embodiment of the present invention. [Figure 5e] FIG. 5e shows an apparatus and the steps involved in mounting a rotary scale member to a piece of apparatus according to a fourth embodiment of the present invention. [Figure 6] FIG. 6 is a flow chart of a method according to the present invention. [Figure 7] FIG. 7 shows an arrangement according to a fifth aspect of the invention. [Figure 8] FIG. 8 shows an arrangement according to a sixth embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] As described herein above, it may be desirable to be able to selectively control the radial arrangement / position of a rotary scale member mounted on a first part of an apparatus that is rotatable relative to a second part of the apparatus about an axis of rotation such that the rotary scale member has a desired radial configuration with respect to the axis of rotation. In particular, it may be desirable to have a scale axis of a scale provided on the rotary scale member arranged in a desired radial arrangement / position with respect to the axis of rotation. For example, it is quite typical, but not necessary, for the desired radial configuration to be such that the scale axis and the axis of rotation are substantially coaxial. In the following, various techniques according to the invention are described that aim to configure a rotary scale member such that its axis is substantially coaxial with the axis of rotation, but it will be appreciated that this is not necessarily the case and the methods of the invention can be used to provide different desired radial configurations.

[0057] Referring to Figures 2a-2e and 6 there is shown an apparatus and steps involved in attaching a rotary scale member (in this embodiment a disc scale member 4) to a part 106 of an apparatus according to a first aspect of the present invention.

[0058] 2a (showing an isometric view of the intermediate scale positioning member 103 attached to the portion 106), FIG. 2b (showing a cross-sectional view of the configuration of FIG. 2a taken in the ZX plane), and FIG. 6, the method begins in step 602 by placing an intermediate scale positioning member 103, in this embodiment a single intermediate scale positioning member in the form of an annular ring, on the shaft 106' of the portion 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 from other materials, such as plastic.

[0059] As shown in FIG. 2b, when the intermediate annular ring member 103 is mounted on the shaft 106′, the tapered inner peripheral surface 105 of the intermediate annular ring member 103 engages with the tapered surface 109 of the mating shaft 106′. The radial configuration of the intermediate annular ring member 103 can be determined / checked by measuring the intermediate annular ring member 103. For example, measurements of the position of the cylindrical outer peripheral surface 107 can be made at multiple points around the intermediate annular ring member 103. This can be done in a variety of ways including, for example, using a sensor such as a Dial Test Indicator (DTI) that interacts with the axially extending cylindrical outer peripheral surface 107 to measure any change in the radial position of the cylindrical outer peripheral surface 107 at different rotational positions of the intermediate annular ring member 103. Such measurements can be taken while the intermediate annular ring member 103 is rotating about the axis of rotation A. Alternatively, such measurements can be taken by moving the intermediate annular ring member 103 in different rotational orientations about the axis of rotation A and taking measurements when the intermediate annular ring member 103 is stationary. In these two methods described above, the sensor may be held at a fixed position about the axis of rotation A. In another embodiment, such measurements may be obtained by keeping the intermediate annular ring member 103 stationary throughout the process of determining the radial configuration and varying the position about the axis of rotation A at which the sensor interacts with the cylindrical circumferential surface 107 (e.g., by moving the same sensor or by using multiple different sensors). As will be apparent, rather than directly measuring the axially extending cylindrical circumferential surface 107, its position may also be inferred by measuring different portions of the intermediate annular ring member 103.

[0060] If the radial configuration of the intermediate annular ring member 103 does not match the desired radial configuration, then in step 604 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 reached. In this embodiment, the desired radial configuration of the intermediate annular ring member 103 is a radial configuration such that when the rotary scale member 103 is mounted on the intermediate annular ring member 103 (e.g. such that the scale axis of the rotary scale member is substantially coaxial with the axis of rotation A), a rotary scale member 4 subsequently mounted thereon (as described in more detail below) is expected to be automatically radially positioned (e.g. received) at a desired radial position relative to the axis of rotation A.

[0061] In the described embodiment, the radial configuration of the intermediate annular ring member 103 can be manipulated via a number of adjustment bolts 111(a, b, c). As shown in Fig. 2b, an adjustment bolt (e.g., adjustment bolt 111a) passes through an axially extending hole 113 in the intermediate annular ring member 103 and threadingly engages with a threaded hole 115 of portion 106. Tightening of the adjustment bolt 111a by its rotation eventually causes a head 117 of the adjustment bolt 111a to engage an upper surface of the intermediate annular ring member 103, and further tightening of the adjustment bolt 111a manipulates at least a portion of the intermediate annular ring member 103 adjacent the adjustment bolt 111a to move axially downward (in the direction shown in Fig. 2b). As will be apparent, due to engagement of the corresponding tapered surfaces 105, 109 of the intermediate annular ring member 103 and shaft 106', any downward axial displacement of the intermediate annular ring member 103 will also displace the portion of the intermediate annular ring member 103 adjacent the adjustment bolt 111a radially outwardly, thereby changing the radial configuration of the intermediate annular ring member 103.

[0062] As will be apparent, in this embodiment, the shape of the intermediate annular ring member 103 is distorted by the operation of the adjustment bolts described above (i.e., the intermediate annular ring member 103 is stretched by the action described above). In an alternative embodiment, the geometry of the shaft 106' and the inner surface of the intermediate annular ring member 103 can be configured (e.g., with mating truncated spherical shapes) such that when the adjustment bolts 111a are operated, the intermediate annular ring member 103 tends to rotate or roll on the shaft, the degree of rotation of the intermediate annular ring member 103 causing an effective change in the radial configuration of the surface on which the rotary scale member 4 is mounted.

[0063] As shown in Figures 2c-d, the rotary scale member 4 attached to the intermediate annular ring member 103 may be the same as that described above in relation to Figure 1, and therefore similar parts share the same reference numerals. Obviously, this need not necessarily be the case and the rotary scale member may take different forms, such as, for example, a ring scale member. Assuming that it is desired that the rotation axis A and the scale axis S are nominally coaxial, in this embodiment the intermediate annular ring member 103 may be manipulated until the radial position of at least a point on the cylindrical outer circumferential surface 107 of the intermediate annular ring member 103 with which the four cantilever spring members 16 of the disk scale members are configured to engage is centered with respect to the rotation axis A.

[0064] Once the operator / installer has verified that the intermediate annular ring member 103 is in the desired radial configuration with respect to the axis of rotation A, the disk scale member 4 may then be attached to the intermediate annular ring member 103 (step 606 in FIG. 6). This is illustrated in FIG. 2c, which shows the disk scale member 4 attached to the intermediate annular ring member 103. In this embodiment, because the inner diameter of the hole 14 defined by the cantilever spring member 16 is smaller than the diameter of the cylindrical outer circumferential surface 107 of the intermediate annular ring member 103, the rotary scale member 4 is press-fit mounted in the hole, where the cantilever spring member 16 radially engages with the cylindrical outer circumferential surface 107 of the intermediate annular ring member 103 and displaces radially outward, thereby automatically positioning (e.g., automatically receiving / biasing / constraining) the body 7 (and thus the scale 8 and scale axis S) of the disk scale member 4 in a default (predetermined) radial arrangement / position with respect to the intermediate annular ring member 103. In this embodiment, the default (predetermined) radial arrangement / position relative to the intermediate annular ring member 103 is determined / controlled by the relative elasticity of the cantilevered spring members 16. In a preferred embodiment, these cantilevered spring members 16 are nominally identical and have nominally the same elasticity, and thus the body self-centers in the intermediate annular ring member 103. By prior intentional manipulation of the configuration of the disc scale member 4 and the radial configuration of the intermediate annular ring member 103 in step 604 in accordance with the above intent, when the disc scale member 4 has received (i.e., positioned) its default (i.e., predetermined) radial arrangement / position relative to the intermediate annular ring member 103, the scale axis S should be at the predetermined desired arrangement / position relative to the portion 6 and its rotation axis A, e.g., substantially coaxial therewith. Therefore, no further adjustment of the radial configuration of the disc scale member 4 should be necessary.

[0065] Step 608 of Figure 6 is an additional optional step involving further fastening the body 7 of the disc scale member 4 to the portion 6, for example by adhesive (not shown) and / or by mechanical fasteners such as bolts 28 (see Figure 2e) that pass through holes 26 in the body 7 of the disc scale member 4 and threadably engage threaded holes 129 (see Figures 2a and 2b) in the portion 106. Step 610 of Figure 6 is a further optional step involving removing the intermediate annular ring member 103. This may be beneficial as the intermediate annular ring member 103 may be reused and / or the space previously occupied by the intermediate annular ring member 103 may be used for other means.

[0066] 3a-3d show a variation of the device shown in FIG. 2 suitable for use with the present invention. Like parts use like reference numerals. The device of FIGS. 3a-3d differs from the device of FIGS. 2a-2e in that the shaft 206′ and the intermediate annular ring member 203 do not have opposing tapered surfaces. Rather, in this embodiment, the intermediate annular ring member 203 comprises an oversized annular ring that fits over the shaft 206′ (i.e., its inner diameter is larger than the diameter of the shaft 206′ and fits loosely thereto) and is axially supported / held on the shelf 119 of the portion 206 of the device. Because the intermediate annular ring member 203 is a loose fit with the shaft 206′, it can be easily moved laterally (in the XY plane) to change its radial configuration.

[0067] In this embodiment, an adjustment tool 210 is provided to help an operator / installer precisely control manipulation of the radial configuration of the intermediate annular ring member 203. The adjustment tool 210 comprises a second annular ring member 212 that fits snugly onto the shaft 206' and sits on top of the intermediate annular ring member 203. The second annular ring member 212 includes elongated first and second slots 214, 216 whose centers are formed proximal to the outer edge of the second annular ring member 212 such that they are annularly spaced 90° from each other to form first and second curved portions 218, 220.

[0068] A tapered head first bolt 222 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 in the intermediate annular ring member 203. The first bolt 222 is tightened until its tapered head contacts the top surface of the second annular ring member 212. Further tightening of the first bolt 222 then drives its tapered head within the slot 214 and the radial reaction force between the first bolt 222, the second annular ring member 212 and the shaft 206' pushes the first bolt 2222 radially outward (in the Y dimension shown in Figures 3a and 3b) and thereby bends the first bend 218 radially outward (in the Y dimension). Such radial outward movement of the first bolt 222 is imparted to the intermediate annular ring member 203 by the connection between the first bolt 222 and the intermediate annular ring member 203, thereby displacing the radial position of the intermediate annular ring member 203 in the radial direction (in the Y dimension).

[0069] As can be seen, due to the resistance to radial displacement of the first curved portion 218, the first curved portion 218 pulls the first bolt 222 radially inward as the first bolt 222 reverses out of the first slot 214, thereby reversing the radial displacement of the intermediate annular ring member 203 (along the Y dimension).

[0070] A second bolt 230 is provided through the second slot 216 and is configured and operates similarly to the first bolt 222 to facilitate adjustment of the radial position (X dimension shown in Figures 3a and 3b) of the intermediate annular ring member 203. As will be apparent, third and fourth slots (not shown) and corresponding bolts (not shown) may be provided at diametrically opposite locations relative to the first and second slots 214, 216 to facilitate radial adjustment of the intermediate annular ring member 203 in opposite directions along the X and Y dimensions to that provided by the first and second slots 214, 226 and corresponding bolts 222, 230.

[0071] Similar to the first embodiment described in relation to FIG. 2, the radial configuration of the intermediate annular ring member 203 can be checked, e.g. measured, to ensure that it has the desired radial configuration. If not, further manipulation of the intermediate annular ring member 203 can be performed until it has the desired radial configuration. Once it has the desired radial configuration, the disk scale member 4 can be attached to the outer cylindrical surface 205 of the intermediate annular ring member 203, as shown in FIG. 3c. According to the embodiment of FIG. 2, the default inner diameter of the hole 14, defined by the cantilever spring member 16 of the disk scale member 4, is smaller than the diameter of the outer cylindrical surface 205 of the intermediate annular ring member 203. Thus, in this embodiment, attaching the rotary scale member 4 to the intermediate annular ring member 203 includes force-fitting the rotary scale member 4 into the intermediate annular ring member 203. Once this engagement is achieved, the cantilever spring member 16 radially engages with the outer cylindrical surface 205 of the intermediate annular ring member 203 and displaces radially outward, thereby automatically positioning (i.e., accepting / biasing / restricting) the body 7 (and thus the scale 8 and scale axis S) of the disk scale member 4 in a default (i.e., predetermined) radial position relative to the intermediate annular ring member 203. In accordance with the above intent, by the configuration of the disk scale member 4 and by prior intentional manipulation of the radial configuration of the intermediate annular ring member 203, when the disk scale member 4 is positioned in / accepts the default (i.e., predetermined) radial position relative to the intermediate annular ring member 103, the scale axis S is in a predetermined desired position relative to the rotation axis A, e.g., substantially coaxial therewith. Therefore, no further adjustment of the radial configuration of the disk scale member 4 should be necessary.

[0072] 3d, if desired, the body 7 of the disc scale member 4 can be secured to the portion 206 of the apparatus, for example, via an adhesive (not shown) and / or via a mechanical fastener, such as a bolt 28 (see FIGS. 3a and 3b), which can threadably engage a threaded hole 129 in the portion 206. Additionally, optionally, the intermediate annular ring member 203 and / or associated tooling 210 can be removed.

[0073] Figures 4a-d show another variation of an apparatus suitable for use with the present invention. Like reference numbers are used for like parts. In this embodiment, part 306 does not include a protruding shaft. Thus, rather than a single, integral intermediate scale positioning member being provided, in this embodiment there are three separate intermediate scale positioning members 303 provided at annularly spaced locations about the axis of rotation A, each radial configuration of which can be independently manipulated, as will be described in more detail below.

[0074] As shown in Figures 4a and 4b, the intermediate scale positioning members 303 of this embodiment include bolts 305 and rings 307. The bolts 305 include a tapered head 309 and a threaded shank 311. The ring 307 includes an outer cylindrical surface 308 and an inner tapered surface 310 that the tapered head 309 engages. The threaded shank 311 of each bolt 305 is in threaded engagement with a corresponding threaded hole 313 in the portion 306 with the ring 307 trapped between the tapered head 309 of the bolt 305 and the portion 306. Together, the outer cylindrical surfaces 308 of the three intermediate scale positioning members 303 are ready for the disk scale members 4 to be attached. Thus, in line with the present invention, when the disk scale member 4 is attached to the three intermediate scale positioning members 303, it may be desirable to manipulate the radial configuration of the three intermediate scale positioning members 303 to a desired radial configuration (e.g., by manipulating at least one of the intermediate scale positioning members 303 in the manner described below) so that the disk scale member 4 is positioned in a desired radial arrangement / position relative to the rotation axis A of the part (e.g., so that the scale axis S and rotation axis A are substantially coaxial).

[0075] The radial configuration of each of the intermediate scale positioning members 303 can be manipulated by tightening its bolts 305. Tightening of the bolts 305 drives the bolts 305 axially further into the section (in the Z dimension) stretching the ring 307 outwardly, thereby increasing its effective diameter and altering the radial location of the engagement point of the ring 307 with the disc scale member 4 when the disc scale member 4 is attached to it.

[0076] Similar to the first and second embodiments described above in relation to Figures 2 and 3, the radial configurations of the intermediate scale positioning members 303 can be checked, e.g. measured, to verify that they provide the desired radial configuration. If not, further manipulation of one or more of the intermediate scale positioning members 303 can be performed until they provide the desired radial configuration. Once they provide the desired radial configuration, the disk scale member 4 can be attached to the outer cylindrical surface 308 of the ring 307 of the three intermediate scale positioning members 303, as shown in Figure 4c. 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 disk scale member 4 is smaller than the effective diameter defined by the radially outermost point of the outer cylindrical surface 308 of the ring 307 of the three intermediate scale positioning members 303. Thus, in this embodiment, attaching the rotary scale member 4 to the three intermediate scale positioning members 303 includes attaching the rotary scale member 4 to the ring 307 of the intermediate scale positioning members 303 with a force fit. In this press fit, the cantilever spring member 16 radially engages with the ring 307 of the three intermediate scale positioning members 303 and displaces radially outward, whereby the body 7 (and thus the scale 8 and scale axis S) of the disk scale member 4 automatically assumes (in other words, is radially disposed / biased / constrained in) its default (predetermined) radial arrangement / position relative to the three intermediate scale positioning members 303. In line with the intent of the method of the present invention described above, due to the configuration of the disk scale member 4 and the intentional manipulation of the radial configuration of the three intermediate scale positioning members 303, when the disk scale member 4 assumes its default (predetermined) radial arrangement / position relative to the three intermediate scale positioning members 303, the scale axis S should be in a predetermined desired arrangement / position relative to the rotation axis A, e.g., substantially coaxial therewith. Therefore, no further adjustment of the radial configuration of the disk scale member 4 is required.

[0077] 4d, if desired, the body 7 of the disk scale member 4 can be secured to the portion 306 of the apparatus, for example, via an adhesive (not shown) and / or via a mechanical fastener such as a bolt 28 (see FIGS. 3a and 3b) that can threadably engage a threaded hole 129 in the portion 306. Additionally, optionally, the three intermediate scale positioning members 303 can be removable.

[0078] In the embodiment described above, three intermediate scale positioning members 303 are used, although it will be apparent that only two or more than three intermediate scale positioning members could be used, if desired. The intermediate scale positioning members 303 could also take different forms, thereby allowing for manipulation of their radial configurations in other ways. For example, they could take the form of offset cam members as described in connection with FIG. 5 below. In other embodiments, the intermediate scale positioning members 303 could be interconnected via a rigid linkage such that they are handled and / or attached to the part as one (although their radial configurations could still be manipulated independently of one another, for example).

[0079] In alternative embodiments, not all of the intermediate scale positioning members need be radially adjustable, such as, for example, the embodiment described below in connection with FIG.

[0080] 5a-5e show another variation of an apparatus suitable for use with the present invention. Similar parts are provided with similar reference numbers. In this embodiment, part 406 does not include a protruding shaft or a suitable surface / body for directly mounting one or more intermediate scale positioning members. Rather, part 406 is a hollow ring-like member. Thus, in this embodiment, a support device 450 is provided, which is fixed to part 406 and comprises a support plate 452 to which one or more intermediate scale positioning members (in this case three intermediate scale positioning members 403) capable of manipulating a radial configuration can be mounted, as will be explained in more detail below. Thus, in this embodiment, one or more intermediate scale positioning members are indirectly disposed / mounted to the part via support device 450.

[0081] As shown in FIG. 5a, the support apparatus 450 includes a support plate 452, a radially expandable clamping portion 454, a tapered member 456, and a bolt 458. The bolt passes through the support plate 452, the radially expandable clamping portion 454, and threadedly engages a threaded hole in the tapered member 456. The three intermediate scale positioning members 403 can be pre-attached to the support plate 452 or can be provided and attached separately. The support apparatus 450 is attached to the section 406 by inserting the support plate 452, the radially expandable clamping portion 454, and the tapered member 456 into the hollow shaft 406. Bolt 458 is then tightened, whereby the axial position of the bolt is fixed by the interaction between its head and support plate 452, thereby pulling tapered member 456 axially upwards (in the Z dimension), causing expandable clamping portion 454 to expand radially outward until it engages portion 406, thereby clamping support device 450 radially inside portion 406.

[0082] In this embodiment, each intermediate scale positioning member 403 comprises an offset cam member. As a result, each intermediate offset cam member 403 comprises a cylindrical head portion 407 and a cylindrical pin portion 409. The cylindrical pin portion 409 is received within and is rotatable within a support plate hole 411 such 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. As a result, the radial position of the radially outermost point of the cylindrical head 407 (relative to the portion 406 rotation axis A) can be changed by rotating the intermediate scale positioning member 403 about the intermediate scale positioning member rotation axis C.

[0083] Similar to the first, second and third embodiments described above in relation to Figures 2, 3 and 4, the radial configurations of the intermediate scale positioning members 403 can be checked, e.g. measured, to verify that they provide the desired radial configuration. If not, further manipulation of one or more of the intermediate scale positioning members 403 can be performed until they provide the desired radial configuration. Once they provide the desired radial configuration, the disk scale member 4 can be attached to the head 407 of the intermediate offset cam member 403, as shown in Figure 5d. 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 disk scale 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. Thus, in this embodiment, attaching the rotary scale member 4 to the intermediate offset cam member 403 includes attaching the rotary scale member 4 to the head 407 of the intermediate offset cam member 403 with a press fit. In this press fit, the cantilever spring member 16 radially engages with the head 407 of the intermediate offset cam member 403 and displaces radially outward, whereby the body 7 (and thus the scale 8 and scale axis S) of the disk scale member 4 automatically assumes (in other words, is radially disposed / biased / constrained in) its default (predetermined) radial arrangement / position relative to the intermediate offset cam member 403. In line with the intent of the method of the present invention described above, due to the configuration of the disk scale member 4 and the intentional manipulation of the radial configuration of the intermediate offset cam member 403, when the disk scale member 4 assumes its default (predetermined) radial arrangement / position relative to the intermediate offset cam member 403, the scale axis S is in a predetermined desired arrangement / position relative to the axis of rotation A, e.g., is substantially coaxial therewith. Therefore, no further adjustment of the radial configuration of the disk scale member 4 should be necessary.

[0084] As shown in Figure 5e, if desired, the body 7 of the disk scale member 4 can be secured to the portion 406, for example, via an adhesive (not shown) and / or via a mechanical fastener such as a bolt 28 (see Figures 5a, 5b and 5c) that can threadably engage a threaded hole 129 in the mechanical portion 406. Additionally, optionally, the intermediate offset cam member 403 can be removed.

[0085] In the embodiment described above, three intermediate offset cam members 403 are used, but it will be apparent that only two or more than three intermediate scale positioning members can be used, if desired. The intermediate scale positioning members 403 can also take different forms, which allows for manipulation of their radial configuration in other ways, for example, by taking the form of the intermediate scale positioning members shown in FIG. 4. Furthermore, the intermediate scale positioning members 403 do not have to be identical, but rather a combination of different types of intermediate scale positioning members can be used. Furthermore, rather than providing multiple separate intermediate scale positioning members in the support device 450 of FIG. 5, the support device 450 can be configured to accept only a single intermediate scale positioning member, such as the intermediate annular ring member of FIG. 2 or FIG. 3 (e.g., the support plate 452 can be provided with a protruding shaft that can accept the intermediate annular ring member of FIG. 2 or FIG. 3).

[0086] In the above described embodiments, the mounting mechanism for the rotary scale member (e.g. the cantilever spring 16) is provided radially inward of the scale track 8. However, as will be apparent, this does not necessarily have to be the case and the mounting mechanism can also be provided radially outward of the scale track 8. Thus, in contrast to the above described embodiments, the disk scale member can be mounted to the at least one intermediate scale positioning member such that it is radially located within a space defined by the at least one intermediate scale positioning member.

[0087] In the above described embodiments, the rotary scale member comprises a disk scale member, with the scale tracks and features provided on a planar surface thereof. Obviously, this does not necessarily have to be the case. For example, the rotary scale member may comprise a ring scale member, with the scale tracks and features provided on the outer circumference of an axially extending cylinder of the rotary scale member body.

[0088] In the above-described embodiment, the rotary scale member comprises an integral resilient compliant (e.g. spring) member (particularly a cantilever spring / flexure) on the body of the rotary scale member, configured to automatically assume (i.e. be radially positioned / biased / restrained in) a default (predetermined) radial arrangement / position relative to the one or more intermediate scale positioning members. As will be apparent, other configurations are possible to achieve the same function. For example, a non-integral resilient compliant member (e.g. a resilient compliant member formed separately on and attached to the body of the rotary scale member or intermediate scale positioning member(s)) can be provided. Furthermore, in another embodiment, the one or more intermediate scale positioning members may include a resilient compliant member. For example, such an embodiment is shown in FIG. 7, which is an improved version of the embodiment of FIG. 2, with similar parts being assigned similar reference numbers. Thus, similar to the embodiment of FIG. 2, the intermediate scale positioning member 103′ of FIG. 7 comprises a metal ring having a tapered inner circumferential surface and a generally cylindrical outer circumferential surface. 7 embodiment, however, three radially protruding leaf spring flexures 104 are provided on a generally cylindrical outer circumferential surface of the intermediate-scale positioning member 103' at annularly spaced locations and are resiliently displaceable radially into an elongated bore 121 extending axially through the intermediate-scale positioning member 103'. The tapered inner circumferential surface is attached to an opposing tapered surface of the shaft 106'. Thus, in the same manner as described above in connection with FIG. 2, the radial configuration of the intermediate-scale positioning member 103' can be adjusted by tightening one or more adjustment bolts 111.Once the operator is satisfied with the radial configuration of the intermediate scale positioning member 103', the rotary scale member 4 (in this embodiment, a scale disk member having a flat circular inner circumferential surface) is press-fitted onto the three radially protruding leaf spring flexures 104 of the intermediate scale positioning member 103', whereby the three radially protruding leaf spring flexures 104 are displaced radially inward and, in response, the rotary scale member 4' engages with the intermediate scale positioning member 103' via reaction forces such that the body 7 of the rotary scale member 4' automatically adopts a default (predetermined) radial arrangement / position relative to the intermediate scale positioning member 103' (in other words, is radially arranged / biased to / constrained in that position).

[0089] As is evident, in most of the above-described embodiments, the elastically compliant members include cantilevered springs / flexures, but non-cantilevered flexures can be used instead of cantilevered flexures, for example leaf flexures such as those used in the second annular ring member 212 of FIG. 3c or the intermediate scale member 103′ of FIG. 7. Furthermore, other types of elastically compliant members can be used, such as helical springs. Furthermore, it is not essential that the mounting mechanism of the rotary scale member is an elastically compliant member, since there are other ways to ensure that the body 7′ (and thus the scale 8 and scale axis S) of the rotary scale member 4 automatically adopts a default (predetermined) radial arrangement / position with respect to its one or more intermediate scale positioning members. For example, referring to the embodiment of FIG. 2, the outer peripheral surface 107 of the intermediate annular ring member 103 and the inner peripheral surface of the disk scale member 4 can have opposing tapered surfaces that mate with each other in a default (predetermined) radial arrangement / position, in a manner similar to the corresponding tapered surfaces 105, 107 of the intermediate annular ring member 103 and shaft 106′.

[0090] In the above-described embodiment, three resilient compliant members are provided on the rotary scale member or intermediate scale positioning member(s). However, this is not necessarily limited to this form. For example, FIG. 8 shows an embodiment in which only a single resilient compliant member is provided. In this embodiment, the part 306 is the same as that shown in and described above in connection with FIG. 4. In this embodiment, a cam-shaped first intermediate scale positioning member 503 and a cam-shaped second intermediate scale positioning member 504 and a third intermediate scale positioning member 505 are provided, which are threadedly engaged in the threaded hole 313 of the part 306. As with the offset cam member of FIG. 5, the radial positions (relative to the part 306 rotation axis A) of the radially outermost points of the heads 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 members about 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. Rather, the third intermediate scale positioning member 505 comprises a flat round head bolt having a fixed, unalterable diameter. However, it will be appreciated that in another embodiment, the radial configuration of the third intermediate scale positioning member 505 may be manipulable, for example, by being a cam member. In other embodiments, the rotary scale member 4'' of FIG. 8 may be used with any of the intermediate scale positioning members described above.

[0091] In the embodiment of FIG. 8, the rotary scale member 4″ differs from those described above in that it comprises a first rigid surface 20 and a second rigid surface 21 that engage with the first cam-shaped intermediate scale positioning member 503 and the second cam-shaped intermediate scale positioning member 504 (when the rotary scale member 4″ is attached to the intermediate scale positioning member) and a flexion member 22 that engages with the third intermediate scale positioning member 505. As in the above-described embodiment, the rotary scale member 4″ is attached to the intermediate scale positioning member by a force fit, whereby the flexion member 22 is radially displaced in a space / hole 23 provided behind the flexion member 22, and the reaction force engages the rotary scale member 4″ with the intermediate scale positioning members 503, 504, 505, such that the body 7″ of the rotary scale member automatically adopts (in other words is radially positioned / biased / constrained at) a default (predetermined) radial position with respect to the intermediate scale positioning member or members. This is defined / controlled in this embodiment by the first rigid surface 20 and the second rigid surface 21. As will be apparent, in an alternative embodiment the third intermediate scale positioning member may be omitted and the flexion member 22 may engage with an integral part (e.g. a shaft or protruding pin) of the portion 306 extending through the hole 14 of the rotary scale member 4''. In an alternative embodiment, in a similar manner to the embodiment of Figure 7, the third intermediate scale positioning member 505 may include a resilient compliant member, in which case the disk may be a fully rigid disk (i.e. the flexion member 22 is replaced with a third rigid surface).

[0092] In the described embodiment, the rotary scale member 4 is an optical rotary scale member, but this does not necessarily have to be the case. For example, the rotary scale member may be a magnetic, inductive or capacitive rotary scale member. Furthermore, in the described embodiment, the rotary scale member 4 is a reflective optical rotary scale member (light from the readhead is reflected by the scale member towards the readhead, and the illumination and graduation sensing parts of the readhead are on the same side of the scale member). However, this does not necessarily have to be the case, and the rotary scale member may also be a transmissive rotary scale member.

[0093] In the described embodiment, the rotary scale member is an incremental rotary scale member. The scale track therefore comprises a series of periodically arranged features that can be read by the readhead 10 to count the relative position / movement of the rotary scale member and the readhead. As is common in the field of incremental encoder devices, the rotary scale member may include one or more reference marks that can be read as the readhead passes over it, thereby allowing the readhead to identify a reference position on the rotary scale member. Exemplary reference marks 9 are shown in the figures showing the rotary scale member (see, for example, Figures 2c, 2d, 2e). In this case, the reference marks 9 are shown in the same track 8 as the incremental graduation features, although this need not be the case. The reference marks 9 may also be provided in a separate track adjacent to the incremental graduation track 8 (as shown, for example, in Figure 7). Of course, the rotary scale member could be an absolute rotary scale member instead of an incremental rotary scale member, with the scale track 8 provided with features defining a series of unique absolute positions such that the absolute position of the rotary scale member and readhead can be determined at start-up without requiring relative movement of the rotary scale member and the readhead.

[0094] In the above-mentioned embodiment, according to the main and first aspect of the present invention, the rotary scale members are attached to one or more intermediate scale positioning members after the intermediate scale positioning members have been manipulated to their desired radial configuration. By doing so, a simple and effective way for the operator / installer to compensate for the offset between the axis of rotation and the geometric center of the part / shaft to which the rotary scale members are attached is provided. For example, the manipulation (and any checking) of the radial configuration can be performed without the rotary scale members being in place, which can facilitate access for the manipulation (and any checking) of the radial configuration and help to avoid damage to the rotary scale members during the manipulation (and any checking) of the radial configuration. Also, the ease of manufacture of the rotary scale members can be improved since there is no need to provide a precise surface thereon to check the radial configuration.

[0095] According to a different second aspect of the invention, the rotary scale members may be attached to the one or more intermediate scale positioning members via a resilient compliant member configured to radially position / position the rotary scale member in a default (predetermined) radial arrangement / position relative to the intermediate scale positioning members during or prior to manipulation (and optional 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 attached to a part of the apparatus, and then the rotary scale members may be attached to the one or more intermediate scale positioning members (via a resilient compliant member configured to radially position / position the rotary scale member in a default (predetermined) radial arrangement / position relative to the intermediate scale positioning members), and then the radial configuration of at least one of the one or more intermediate scale positioning members may be manipulated until a desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved. Alternatively, the rotary scale member may be attached to the one or more intermediate scale positioning members (via a resilient compliant member configured to radially position / locate the rotary scale member in a default (predetermined) radial arrangement / position relative to the intermediate scale positioning members) before the one or more intermediate scale positioning members are attached to the part. Although this second aspect of the invention does not have the above-mentioned advantages of the main and first aspects of the invention, the second aspect has advantages over existing known techniques for attaching rotary scale members. In particular, the resilient compliant member may help to isolate the rotary scale member from any significant form or shape deformation that may otherwise be imparted to the rotary scale member through manipulation of the radial configuration of the one or more intermediate scale positioning members while ensuring that the rotary scale member self-positions / accommodates in the default (predetermined) radial arrangement / position relative to the one or more intermediate scale positioning members.

[0096] In the above-described embodiment according to the first aspect of the invention, the one or more intermediate scale positioning members are attached to the first part before the rotary scale member is attached to the intermediate scale positioning member (and thus before the rotary scale member is disposed on the first part). However, according to another aspect of the invention, the rotary scale member may be disposed on the first part before the intermediate scale positioning member is attached to the first part. Optionally, the one or more intermediate scale positioning members may comprise one or more resilient compliant members with which the rotary scale member engages such that when the intermediate scale positioning member is attached to the first part and engaged with the rotary scale member, the rotary scale member is biased towards a default radial position relative to the intermediate scale positioning member (and thus relative to the axis of rotation). The resilient compliant members may be integrally formed with the intermediate scale positioning member or may be formed separately from the intermediate scale positioning member and comprise the intermediate scale positioning member.

[0097] In the above-described embodiments, the elastic compliant member comprises the rotary scale member and / or the one or more intermediate scale positioning members (either integrally formed therewith or separately formed and attached / fixed thereto). As will be appreciated, this does not necessarily have to be the case. For example, the elastic compliant member(s) may be provided completely separately on the rotary scale member and the one or more scale positioning members. For example, the rotary scale member may be positioned on the first portion and the one or more intermediate scale positioning members may be attached to the first portion (in either order), and then the elastic compliant member may be positioned / placed between the rotary scale member and the one or more intermediate scale positioning members to engage both the rotary scale member and the one or more intermediate scale positioning members, thereby radially positioning the rotary scale member at a default radial position relative to the intermediate scale positioning member. The step of manipulating the radial configuration of at least one of the one or more intermediate scale positioning members may be performed before / after the elastic compliant member is positioned / placed between the rotary scale member and the one or more intermediate scale positioning members. Further, for example, manipulating the radial configuration of at least one of the one or more intermediate scale positioning members may be performed before or after the rotary scale member is positioned in the first portion.

[0098] It will also be appreciated that combinations of the above-mentioned optional configurations are possible rather than all of the elastic compliant members being provided on the rotary scale member, all of the elastic compliant members being provided on the intermediate scale position member(s), or all of the elastic compliant members being provided completely separately (e.g. at least one elastic compliant member can be provided on / by the rotary scale member, and / or at least one elastic compliant member can be provided on the intermediate scale position member(s), and / or at least one elastic compliant member can be provided completely separately).

Claims

1. 1. A method of mounting a rotary scale member to a first part of an apparatus, the first and second parts of the apparatus being relatively rotatable about an axis of rotation, the rotary scale member including a body provided or capable of being provided with a series of scale features defining a scale extending about a scale axis, the method comprising: i) attaching one or more intermediate scale positioning members to the first portion 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; ii) then mounting 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 , further comprising the step of: iii) subsequently fixing a body of the rotary scale member to define a radial position relative to the portion.

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

4. 4. The method of claim 1, wherein step i) comprises checking the radial configuration of at least one of the one or more intermediate scale positioning members.

5. 5. The method of claim 4, wherein the checking step comprises determining positions of at least a portion of the one or more intermediate scale positioning members to determine the radial configuration of the one or more intermediate scale positioning members.

6. The method of claim 1 , wherein the rotary scale member is attached to the one or more intermediate scale positioning members via one or more resilient compliant members.

7. 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 rotary scale member engages with the one or more intermediate scale positioning members via a reaction force such that the one or more resilient compliant members are displaced, whereby a body of the rotary scale member is radially positioned at the default radial position relative to the one or more intermediate scale positioning members.

8. 8. The method of claim 1, wherein step i) comprises disposing separate intermediate scale positioning members on said portion at at least two annularly spaced locations about the axis of rotation, and wherein a radial configuration of at least one of the separate intermediate scale positioning members is manipulated independently of the other(s).

9. 8. The method according to claim 1, wherein step i) comprises disposing a single intermediate scale positioning member providing a surface for receiving the rotary scale member in at least three annularly spaced locations on the portion about the axis of rotation.

10. The method of claim 9 , wherein the single intermediate scale positioning member comprises an annular intermediate scale positioning member having a substantially circular surface for receiving the rotary scale member.

11. 11. The method according to claim 1, wherein the desired radial configuration of the one or more intermediate scale positioning members is a configuration that ensures that the scale axis and the rotation axis of the portion are substantially coaxial when the rotary scale member is attached to the intermediate scale positioning member in step ii).

12. 1. A method of mounting a rotary scale member to a first part of an apparatus, the first and second parts of the apparatus being relatively rotatable about an axis of rotation, the rotary scale member including a body provided or capable of being provided with a series of scale features defining a scale extending about a scale axis, the method comprising: i) attaching one or more intermediate scale positioning members to the first portion; ii) attaching the rotary scale member to the one or more intermediate scale positioning members via one or more resilient compliant members configured to radially position the rotary scale member at a default radial position relative to the intermediate scale positioning members; iii) manipulating a radial configuration of at least one of the one or more intermediate scale positioning members attached to the first portion until a desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved; and iv) following steps i) to iii), fixing the body of the rotary scale member to fix its radial position relative to the first portion and then removing the one or more intermediate scale positioning members.

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

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

15. a) after the one or more intermediate scale positioning members are attached to the first portion; or b) mounting the one or more intermediate scale positioning members in the first portion together with The method of claim 12 , wherein the rotary scale member is disposed on the first portion.

16. 16. The method of claim 12, wherein step iii) comprises checking the radial configuration of at least one of the one or more intermediate scale positioning members.

17. 17. The method of claim 16, wherein the checking step comprises determining positions of at least a portion of the one or more intermediate scale positioning members to determine the radial configuration of the one or more intermediate scale positioning members.

18. 18. The method of 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 resilient compliant members to which the rotary scale member is attached.

19. 20. The method of claim 12, wherein the resilient compliant member includes a bend.

20. 20. A method according to any one of claims 12 to 19, wherein the body of the rotary scale member comprises a planar disk, and the series of scale features are provided on a plane of the planar disk.

21. one or more intermediate scale positioning members configured to be attached to a first portion of a device having a first portion and a second portion, the first portion and the second portion being relatively rotatable about an axis of rotation, the intermediate scale positioning members being configured such that at least one radial configuration of the one or more intermediate scale positioning members is operable relative to the axis of rotation; a rotary scale member comprising a body provided or capable of being provided with a series of scale features defining a scale extending around a scale axis, the rotary scale member being attachable to one or more intermediate scale positioning members such that a radial position of the rotary scale member relative to the axis of rotation is controlled by the one or more intermediate scale positioning members, the rotary scale member being attachable to the one or more intermediate scale positioning members via one or more resiliently compliant members configured to radially position the rotary scale member at a default radial position relative to the intermediate scale positioning members when the rotary scale member is attached to the one or more intermediate scale positioning members; means for fixing the rotary scale member to the first part independently of the one or more intermediate scale positioning 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 positioning members; An apparatus comprising:

22. 22. The apparatus of claim 21 , wherein the rotary scale member is attachable to the one or more intermediate scale positioning members via at least three resiliently compliant members arranged at different, e.g. substantially equiangular, positions around the scale axis.

23. 23. The apparatus of claim 21 or 22, wherein the resilient compliant member includes a bend.

24. 24. The apparatus of claim 21, wherein the rotary scale member includes the resilient compliant member.

25. 24. The apparatus of any one of claims 21 to 23, wherein the one or more intermediate scale positioning members comprise the one or more resiliently compliant members to which the rotary scale member is attached.

26. 26. An apparatus according to any one of claims 21 to 25, configured such that the rotary scale member can be attached to one or more intermediate scale positioning members already attached to the first part of the device.

27. 1. A method of mounting a rotary scale member to a first part of an apparatus, the first and second parts of the apparatus being relatively rotatable about an axis of rotation, the rotary scale member including a body provided or capable of being provided with a series of scale features defining a scale extending about a scale axis, the method comprising: i) attaching one or more intermediate scale positioning members to the first portion; ii) engaging the rotary scale member and the one or more intermediate scale positioning members with one another via one or more resilient compliant members; iii) manipulating the radial configuration of at least one of the one or more intermediate scale positioning members attached to the portion until a desired radial configuration of the one or more intermediate scale positioning members relative to the axis of rotation is achieved; iv) following steps i) to iii), fixing the body of the rotary scale member to fix its radial position relative to the first portion and then removing the one or more intermediate scale positioning members; A method comprising:

28. 30. The method of claim 27, wherein at least one of the one or more intermediate scale positioning members includes at least one of the one or more resilient compliant members.

29. 29. The method according to claim 27 or 28, wherein said step ii) is carried out before or during said step ii).

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

31. a rotary scale member having a body provided, or capable of being provided, with a series of scale features defining a scale extending about a scale axis; one or more intermediate scale positioning members configured to be attached to a first portion of a device having a first portion and a second portion such that at least one of the one or more intermediate scale positioning members can be manipulated relative to an axis of rotation, the one or more intermediate scale positioning members comprising one or more resilient compliant members with which the rotary scale member can be engaged such that the rotary scale member is biased to a default radial position relative to the one or more intermediate scale positioning members; means for fixing the rotary scale member to the part independently of the one or more intermediate scale positioning 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 positioning members; An apparatus comprising:

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