Rotary Encoder

Abstract

A method of mounting a rotary scale member on a machine part configured to rotate 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, and at least three radially following flexures spaced about said scale axis. The method comprises: i) positioning the rotary scale member on the machine part such that the scale axis and the rotation axis are substantially parallel; ii) thereafter positioning at least a first radial adjustment device in contact with both the machine part and the rotary scale member, and manipulating the at least first radial adjustment device to radially displace the body of the rotary scale member. At least a majority of any radial reaction force generated as a result of interaction of at least one of said flexures with a radially urged radial stop member and applied by the rotary scale member to at least the first radial adjustment device against said radial displacement of the rotary scale member is directed to and reacted by the machine part via contact between at least the first radial adjustment device and the machine part.

Description

[Technical field]

[0001] The present invention relates to a method for mounting a portion of a rotary encoder, such as a rotary scale member, to a rotatable part of a machine. [Background technology]

[0002] Measuring scales are used to measure the position of parts of machines that can move relative to one another. A metrological scale typically has a series of features that are read by a readhead, which may provide a measurement of the position along or around the scale. The metrological scale may be mounted on one part of the machine and read by a suitable readhead attached to another part of the machine. Types of metrological 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 may be transmissive or reflective. Examples of optical scale configurations are also disclosed in US Pat. No. 5,399,433 and US Pat. No. 5,499,433.

[0003] To measure rotational displacement, such a scale may be provided on a member that rotates in use with a shaft or other rotating part relative to the readhead. In particular, the member having the scale features and that rotates in use with the shaft may be an annular body in the form of a disk or ring.

[0004] It may be desirable to be able to adjust the radial position of a rotary scale member during the process of mounting the rotary scale member to a machine component. Although techniques for adjusting the radial position of a rotary scale member are already known, such as that described in US Pat. No. 5,399,633, the present invention provides an effective alternative technique.

[0005] The present invention therefore relates to an improved / alternative method of mounting a rotary encoder, in particular a rotary scale member comprising a body (e.g. annular body) provided with a series of positional features defining a scale, and one or more flexures (in other words "springs"). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent Application Publication No. 0207121 [Patent Document 2] U.S. Pat. No. 4,926,566 [Patent Document 3] U.S. Patent No. 9,103,381 Summary of the Invention

[0007] According to a first aspect of the invention, there is provided a method of mounting a rotary scale member on a machine part configured to rotate 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, and at least three radially following bends spaced about said scale axis. The method may comprise i) positioning the rotary scale member on the machine part such that the scale axis and the rotation axis are substantially parallel. The method may further comprise ii) subsequently positioning at least a first radial adjustment device so as to contact both the machine part and the rotary scale member. Step ii) may further comprise manipulating the at least a first radial adjustment device to radially displace the body of the rotary scale member. At least a majority of any radial reaction force imparted by the rotary scale member to at least a first radial adjustment device in opposition to said radial displacement of the rotary scale member, generated / resulting from interaction of at least one of said bends with a radially pressed radial stop member, can be directed to and reacted by the mechanical part via contact between the at least first radial adjustment device and the mechanical part.

[0008] The present invention has been found to provide an effective method for adjusting the radial position of a body of a rotary scale member. For example, the method according to the present invention can provide predictable and controlled radial adjustment of a body of a rotary scale member. The provision of a radial stop member against which a flexure (spring) is radially biased to generate a radial reaction force opposing said radial displacement can be beneficial to help reverse any radial displacement effected by operation of the radial adjustment device.

[0009] As will be appreciated, the flexures are elastically flexible in the radial direction (relative to the rotary scale member) and therefore may be referred to as "springs" or "radial spring members."

[0010] In an optional embodiment of the invention, at least three flexures may be in an unflexed state in step i). Thus, when the rotary scale member is initially placed on the machine part, the at least three flexures may be in an unflexed (i.e. relaxed) state. This may be contrasted with and advantageous to an embodiment in which step i) comprises force-fitting the rotary scale member to a feature of the machine part, thereby moving at least one of said flexures radially out of its relaxed state, thereby engaging the rotary scale member with the machine part via a radial reaction force to form a friction fit with the part such that the body of the rotary scale member is self-positioned to an initial default radial position relative to the part. Thus, step ii) may comprise radially pressing at least one of the flexures against said stop member, thereby deforming / displacing it away from its unflexed / relaxed state.

[0011] As will be appreciated, the radial displacement of the body in step ii) may cause a change in the extent to which at least one of the flexures is pushed radially against the radial stop member (e.g. may cause a change in the extent to which at least one of the flexures is deformed / displaced away from its unflexed / relaxed state).

[0012] Said stop member may comprise an integral part of the machine part. For example, the stop member may comprise an integral hub or shaft, which may for example protrude from a surface / feature on which the rotary scale member is initially located in step i) (e.g. extending from a surface / feature that controls the axial position of the rotary scale member). In an optional but advantageous embodiment of the invention, the stop member is not an integral part of the machine part. This may be preferred / advantageous as it avoids the need for the machine part to provide a feature against which the flexure is radially pressed. For example, the invention may be used on machine parts that do not have a suitable protruding feature (e.g. hub or shaft) that extends from a surface / feature on which the rotary scale member is initially located (e.g. extending from a surface / feature that controls the axial position of the rotary scale member). Thus, preferably, the method further comprises providing (e.g. locating / fixing to the machine part) said radial stop member adjacent at least one of said flexures. Thus, the stop member may be a separate part to the machine part, for example to be removably fixed to the machine part.

[0013] The radial stop member may include or be a radial adjustment device. Thus, one and the same device can perform the functions of a radial stop member and a radial adjustment device. As will be understood, which function it is performing at any given time depends on how it is being used. For example, if the device itself is being manipulated (e.g., by an installer / operator) to perform a radial adjustment of the body of the rotary scale member, it is performing the function of a radial adjustment device. However, at another moment, other means (e.g., another radial adjustment device) may be used to perform a radial adjustment of the body of the rotary scale member, so that the device at that moment is merely functioning as a stop member. However, this does not necessarily have to be the case, and the stop member may be configured such that it can only function as a stop member and cannot be used to effect a radial displacement of the body of the rotary scale member.

[0014] It may be desirable to avoid significant deformation of at least a part of the body / substrate on which the series of positional features are provided, as such deformation may adversely affect metrology performance of the rotary scale member. Thus, preferably, the shape and size of at least a part of the body / substrate on which the scale is provided is not substantially altered by said manipulation of the radial adjustment device and said radial displacement of the rotary scale member. Rather, preferably, such manipulation / displacement primarily causes a change in the bending state of one or more of the at least three flexures. For example, said manipulation / displacement may change the degree of displacement or deformation of at least one of the at least three flexures from its / their rest position / configuration, thereby substantially isolating the scale from any deformation caused by the manipulation / displacement.

[0015] As will be appreciated, step i) may include locating the rotary scale member on a reference surface of a machine part such that the scale axis and the rotation axis are substantially parallel. As will be appreciated, the axial position of the rotary scale member (i.e. the position of the rotary scale member along the rotation axis) may be controlled / defined by the machine part in step i), in other words the rotary scale member may be supported / held in a predefined axial position by the machine part in step i). The reference surface may extend perpendicular to the rotation axis. The reference surface may be defined by a substantially flat plane. Optionally, the reference surface is defined by a plurality of separate pedestals (e.g. protrusions such as hemispherical members) configured to receive the rotary scale member. Such separate pedestals may be annularly spaced around the rotation axis, e.g. equiangularly spaced around the rotation axis.

[0016] The body of the rotary scale member may include an annular body. The body, e.g., annular body, may include a planar disk. The series of location features may be provided on a plane of the rotary scale member (e.g., planar disk) (as opposed to a peripheral edge more commonly associated with ring scales / encoders). Thus, the rotary scale member may include a disk scale member (which may also be interchangeably referred to as a scale disk member) (e.g., for disk encoders) that includes a planar surface on which a series of scale features defining a scale are or can be provided, with the scale axis extending perpendicular to the planar surface. Optionally, the planar disk is 5 mm or less thick, e.g., 3 mm or less thick, e.g., about 1 mm thick. Preferably, the at least three flexures are provided substantially flush with the planar disk. This provides a particularly compact rotary / disk scale member. The at least three flexures may be provided on a member (e.g., a hub) that is formed separately from the body of the rotary scale member but is attached to the body of the rotary scale member. For example, the scale features may be formed / provided on a glass disk substrate attached (e.g. bonded) to a member (e.g. hub) including said at least three flexures. Preferably, however, the at least three flexures are integrally formed on the body of the rotary scale member. For example, the body on which the scale tracks are provided or can be provided, and the at least three flexures may be formed from a single material. Again, this helps to provide a particularly compact rotary scale member and helps to ensure that radial reaction forces are contained in the plane of the body. For example, the body of the rotary scale member and the at least three flexures may be formed (e.g. cut) from a single sheet or plate of material (e.g. metallic material).

[0017] Preferably, the body comprises a metallic material, although it will be appreciated that other materials may be used.

[0018] At least a first radial adjustment device may be arranged to contact one of the flexures of the rotary scale member (e.g., a foot of one of the flexures, as described in more detail below). Thus, manipulating the at least a first radial adjustment device may cause a radial displacement of the flexure (e.g., its foot) and thereby a radial displacement of the body of the rotary scale member. Arranging the radial adjustment device to act in contact with the flexure (e.g., rather than directly contacting the body of the rotary scale member) may help to avoid deformation of the body of the rotary scale member. A radial reaction force may be generated by or as a result of an interaction of at least one other flexure of the flexure (e.g., a foot of at least one other flexure of the flexure) with a radial stop member against which it is radially pressed.

[0019] In a preferred embodiment, at least the flexures in contact with the radial adjustment device being adjusted (e.g. at least the feet of the flexures) are not radially compressed between the radial adjustment device and any other part / member (e.g. during step ii)), e.g. between any other part of the machine part, and therefore the radial flexures can be freely moved / displaced by the radial adjustment device.

[0020] At least one (and optionally all) of the at least three flexures may include a foot. The radial adjustment device and / or stop member may be arranged / configured to contact the foot of the flexure. The foot may be attached to the body of the rotary scale member by one or more legs / legs. The foot and / or leg may be configured to be elastically flexible / deflectable / deformable. Thus, a radial displacement of the body of the rotary scale member may cause the foot and / or leg to bend / deflect / deform from its / their relaxed / unflexed state. A radial reaction force may be generated by the bending / deflection / deformation of the foot and / or leg.

[0021] Optionally, at least one (and optionally all) of the at least three flexures are configured to follow both radially and tangentially. For example, at least one (and optionally all) of the at least three flexures may include a foot configured to be opposed / engaged by a radial adjustment device or stop member, and the flexures are configured such that the foot follows radially and tangentially with respect to the body (of the rotary scale member). For example, the foot may be attached to the body by one or more legs / legs. For example, the foot may follow its own radial direction and one or more legs may provide tangential following. The radial and / or tangential following may be provided by bending the relevant part (e.g., by bending the foot along its length or by bending the legs along its (their) length). For example, the rotary scale member may include four radially and tangentially following flexures (e.g., equiangularly spaced around the scale axis).

[0022] Optionally, all of the at least three flexures are located radially outward of the series of location features defining the scale (e.g. the flexures may be located on or towards the periphery of the body (of the rotary scale member). Optionally, all of the at least three flexures are located radially inward of the series of location features defining the scale. However, this does not necessarily have to be the case and at least one of the at least three flexures may be located radially outward of the series of location features defining the scale and at least one of the at least three flexures may be located radially inward of the series of location features defining the scale.

[0023] The body of the rotary scale member may comprise a hole. The hole may be substantially centrally located within the body. At least one (and optionally all) of the at least three bends may be provided around the edge / periphery / border / circumference of the hole. Thus, at least one (and optionally all) of the at least three bends may face radially inwardly towards the center of the hole. The at least three bends may define the hole.

[0024] Optionally, at least one of the flexures (and optionally each) defines a flexure gap between the body of the rotary scale member and a portion of the flexure (e.g., the foot). The portion of the flexure (e.g., the foot) may be a portion configured to contact a radial stop member / radial adjustment device. For example, the portion of the flexure (e.g., the foot) may be a portion configured to be pressed radially against a radial stop member / radial adjustment device. In such a case, at least a portion of the radial stop member / radial adjustment device that contacts the flexure may be within the flexure gap (as opposed to being located outside the gap). Thus, the portion of the radial stop member / radial adjustment device needs to be at least radially smaller than the gap so as not to be pressed against the body of the rotary scale member.

[0025] The radial adjustment device may comprise a rotatable member. The rotatable member may be rotatable about a radial adjustment device axis. The method / radial adjustment device of the present invention may be configured / arranged such that a rotation of said rotatable member causes a change in radial displacement of the body of the rotary scale member. The method / radial adjustment device of the present invention may be configured / arranged such that a rotation of said rotatable member causes a change in radial displacement of at least a part of the flexure (e.g. a foot thereof) that the radial adjustment device contacts / acts / engages, thereby causing a radial displacement of the body of the rotary scale member. The method / radial adjustment device of the present invention may be configured / arranged such that a rotation of said rotatable member causes a change in the radial position of a contact point between the radial adjustment device and the rotary scale member. In step ii), the radial adjustment device axis may be arranged substantially parallel to the rotation / scale axis. The radial adjustment device may be referred to as a rotatable radial adjustment device.

[0026] The radial adjustment device (e.g., a rotatable radial adjustment device) may comprise a threaded member / part. For example, the radial adjustment device may comprise a bolt or a screw. As described in more detail below, the radial adjustment device may comprise an anchor portion, where the anchor portion may comprise a threaded member / part. The anchor portion / threaded member / part may be configured to engage with a corresponding threaded member (e.g., a threaded hole) on the mechanical part. Rotating the rotatable member of the radial adjustment device about the axis of the radial adjustment device may move the radial adjustment device along the axis. For example, rotating the radial adjustment device about the radial adjustment device axis may move the radial adjustment device further along the axis into (or out of, depending on the direction of rotation) a threaded hole in the part to which the rotary scale member is attached. If the mechanical part is a shaft, the threaded hole may be provided on a radially extending surface or protrusion (e.g., a ledge or flange) that may be attached to the shaft, for example, on an end face provided at the end of the shaft.

[0027] The radial adjustment device may comprise a tapered member (e.g., tapered along the radial adjustment device axis in step ii)) along the rotation axis / scale axis. The method / radial adjustment device of the present invention may be configured / arranged such that rotation of the rotatable member about said radial adjustment device axis changes the axial position of the tapered member along the radial adjustment device axis, which in turn controls the degree of radial displacement of the body of the rotary scale member. For example, in those embodiments in which the radial adjustment device is in contact with a flexure, the method / radial adjustment device of the present invention may be configured / arranged such that rotation of the rotatable member about said radial adjustment device axis changes the axial position of the tapered member along the radial adjustment device axis, which in turn controls the degree of radial displacement of the flexure it is in contact with. Such an arrangement has been found to be advantageous for providing a very fine degree of control over the radial adjustment. The tapered member may comprise a conical shape (which may be a straight or curved conical shape).

[0028] The rotatable member of the radial adjustment device can include a threaded member received by a threaded hole in a machine part such that rotation of the threaded member changes the axial position of the tapered member along the radial adjustment device axis. The threaded member can be an anchor portion (described in more detail below). In embodiments in which the radial adjustment device includes a tapered member and a threaded member, the tapered member and the threaded member can include a single part (e.g., made from a single material). The radial adjustment device can include / be a radial adjustment bolt, the head of the bolt including / is the tapered member.

[0029] The radial adjustment device may comprise an anchor portion. The radial adjustment device may be fixed to the machine part such that the radial adjustment device axis is radially fixed relative to the machine part. The anchor portion may include said screw member. Optionally, at least a majority of any (e.g. substantially all) radial reaction force applied to the radial adjustment device (e.g. applied to the rotary scale member operating portion, as described in more detail below) is reacted by the machine part via the anchor portion, thereby holding the radial adjustment device in a radially fixed position.

[0030] The radial adjustment device may include a cam member that may have a non-constant radius and / or may be eccentrically mounted such that the effective radius of the portion of the cam member that contacts the rotary scale member (e.g., contacts the flexure) is controlled by rotation of the cam member.

[0031] The tapered member, cam member, and / or rotatable member mentioned above may be configured to contact the rotary scale member. Optionally, the radial adjustment device includes an intermediate member disposed between the tapered member / cam member / rotatable member and the rotary scale member. The intermediate member may include, for example, an O-ring, a plug, or a sleeve. The intermediate member may be configured to deform, expand, and / or move when the radial adjustment device (e.g., the tapered member / cam member / rotatable member) is manipulated.

[0032] At least a first radial adjustment device may include a rotary scale member manipulation portion (e.g., a flexure manipulation portion) and an anchor portion. Such a radial adjustment device may be arranged in step ii) such that the rotary scale member manipulation portion (e.g., a flexure manipulation portion) contacts and acts on the rotary scale member (e.g., on the flexure), and the anchor portion is attached to the machine part, and the operation of the radial adjustment device causes a change in radial displacement of at least a portion (e.g., at least a portion of the flexure) of the rotary scale member on which the rotary scale member manipulation portion (e.g., the flexure manipulation portion) acts, thereby causing a radial displacement of the body of the rotary scale member. At least a majority of any (e.g., substantially all) radial reaction force applied to the rotary scale member manipulation portion (e.g., the flexure manipulation portion) may be reacted by the machine part via the anchor portion, thereby holding the radial adjustment device in a radially fixed position. As described above, the anchor portion may be fixed to the machine part such that a radial adjustment device axis of the radial adjustment device is radially fixed relative to the machine part.

[0033] Similarly, the radial stop member may comprise a rotary scale member engaging portion (e.g., a flexure engaging portion) and an anchor portion. Such a radial stop member may be configured such that in step ii), the rotary scale member engaging portion (e.g., a flexure engaging portion) contacts and acts on the rotary scale member (e.g., against a flexure thereof), and the anchor portion may be arranged to be attached to the machine part such that at least a majority of any (e.g., substantially all) radial forces applied to the rotary scale member engaging portion (e.g., the flexure engaging portion) are reacted by the machine part via the anchor portion, thereby holding the radial stop member in a radially fixed position.

[0034] With respect to the radial adjustment device and / or radial stop member described above, the rotary scale member manipulation / engagement portion (e.g., flexion / engagement portion) and its anchor portion may comprise a single portion (e.g., formed from / as a single portion). The rotary scale member manipulation portion (e.g., flexion / engagement portion) and the anchor portion may be rotatably fixed relative to one another. For example, rotating the radial adjustment device may include rotating the rotary scale member manipulation portion (e.g., flexion / engagement portion) and the anchor portion together. Optionally, the rotary scale member manipulation / engagement portion (e.g., flexion / engagement portion) and the anchor portion may comprise separate parts that are / can be connected. Optionally, the rotary scale member manipulation / engagement portion (e.g., flexion / engagement portion) is rotatable relative to the anchor portion. For example, rotating the radial adjustment device may include rotating the rotary scale member manipulation portion (e.g., flexion / engagement portion) relative to the anchor portion (e.g., the anchor portion may be rotationally fixed relative to a machine part).

[0035] Optionally, the rotary scale member includes a central axial opening extending therethrough, and the bend is disposed around an inner circumference / periphery of said central opening. According to an advantageous embodiment of the invention, the diameter of any portion of the machine part that extends at least part way through said central opening can be smaller than the smallest possible diameter of the central opening (e.g. as defined by the bend).

[0036] According to an advantageous embodiment of the invention, the rotary scale member is not radially clamped directly to the machine part. Thus, in an advantageous embodiment of the invention, the flexure is not radially pressed directly against the machine part. Rather, in an advantageous embodiment of the invention, the flexure is radially pressed directly against a radial adjustment member and / or a radial stop member that is not integral with the machine part.

[0037] The step of manipulating the radial adjustment device can be performed manually (e.g., via a human operator / installer) or automatically (e.g., via a robot). As will be appreciated, the radial adjustment device can be manipulated using a tool such as a screwdriver or a hex wrench or "Allen" key.

[0038] As will be appreciated, the body of the rotary scale member can be fixed / secured / maintained at the adjusted radial position. Thus, the method can include fixing / securing the body at its adjusted radial position. Thus, the method can include fixing / securing the radial position of the body relative to the machine part at the adjusted radial position via a fixing means, for example via one or more mechanical fasteners and / or adhesives. For example, the radial position of the body relative to the part at its adjusted radial position can be maintained by said at least one radial adjustment device. Optionally, the method includes fixing / securing the radial position of the body relative to the part at its adjusted radial position via a means other than the at least one radial adjustment device. For example, a substance other than the radial adjustment device (such as an adhesive) or a mechanical fastener may be used. In this case, the at least one radial adjustment device can be removed or left in place.

[0039] The flexures may be provided as single flexures or as clusters of commonly acting flexures, e.g., pairs of flexures. Preferably, the direction and magnitude of the radial reaction force of each flexure in a flexure cluster or pair is substantially / nominal the same. Thus, the above reference to at least three (e.g., at least four) flexures includes the above reference to a cluster (e.g., pair) of at least three (e.g., at least four) flexures.

[0040] The flexures may be cantilever flexures / spring members. This may be particularly preferred where the flexures are provided in pairs. Each of the flexure members of the pair may be configured such that their free ends are proximal to each other and their fixed (or "root") ends are distal to each other.

[0041] Preferably, the series of location features defining the scale are integrally formed on the body (as opposed to the series of location features defining the scale being formed on a separate substrate attached to the body. For example, the scale features may be formed on a flexible tape wrapped around the circumferential edge of the body of the rotary scale member).

[0042] Preferably, all of the at least three (eg, at least four) flexures are substantially identical to one another such that the magnitude of the radial reaction forces provided by them are nominally the same.

[0043] The flexures may be compliant / deflectable (eg, by bending) in a plane perpendicular to the scale axis (radially, and optionally also tangentially).

[0044] A radial adjustment device (e.g. manually operable) may be configured to act on the flexure to vary the degree of deflection of the flexure in said plane, thereby facilitating adjustment of the radial position of the rotary scale member relative to the part to which it is attached.

[0045] Optionally, the at least three flexures are annularly spaced about the scale axis. Optionally, the at least three flexures are substantially equiangularly spaced about the scale axis. For example, in one embodiment, the rotary scale member comprises three (or three pairs) of annularly spaced flexures disposed substantially 120° apart from each other.

[0046] The rotary scale member may include at least four radially following flexures. Thus, optionally, the rotary scale member comprises four (or four pairs) of annularly spaced flexures arranged substantially 90° apart from each other.

[0047] The scale may extend annularly around the scale axis. The scale may extend annularly continuously around the scale axis. The scale may include an incremental scale. The scale may include one or more reference markings. The scale may include an absolute scale. The scale may include optical, capacitive, inductive and / or magnetic scale features. The scale may include one or more tracks of scale features. In the case of a scale disc member, 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).

[0048] According to a second aspect of the invention, there is provided an apparatus comprising a rotary scale member and a mechanical part configured to rotate about a rotation axis. The rotary scale member may comprise 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 may comprise at least three radially following bends spaced about said scale axis. The rotary scale member may be arranged on the mechanical part such that the scale axis and the rotation axis are substantially parallel. The apparatus may comprise at least a first radial adjustment device that may be arranged to contact both the mechanical part and the rotary scale member. The at least a first radial adjustment device may be operable to radially displace the body of the rotary scale member. The apparatus may be configured such that at least a majority of any radial reaction force generated as a result of interaction of at least one of said bends with a radially pressed radial stop member and imparted by the rotary scale member to at least a first radial adjustment device in opposition to said radial displacement of the rotary scale member is directed to and reacted by the mechanical part via contact between the at least a first radial adjustment device and the mechanical part.

[0049] According to a third aspect of the present invention, there is provided a method of mounting a rotary scale member on a machine part configured to rotate 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 and at least three integral radially following radial adjustment flexures spaced about said scale axis, the method comprising: i) positioning the rotary scale member on the machine part such that the scale axis and the rotation axis are substantially parallel, and ii) thereafter manipulating at least a first radial adjustment device to adjust the radial position of the body of the rotary scale member relative to the machine part. The method may be characterised in that the at least first radial adjustment device comprises a flexure operating portion and an anchor portion, and in step ii) the flexure operating portion is configured to act on the radial adjustment flexures of the rotary scale member, the anchor portion being attached to the machine part, and operation of the radial adjustment device can cause a change in radial displacement of at least a part of the radial adjustment flexures acted upon by the flexure operating portion, thereby causing a radial displacement of the body of the rotary scale member. At least a majority of any radial reaction force applied to the bending portion may be reacted by the mechanical components through the anchoring portion, thereby holding the radial adjustment device in a radially fixed position.

[0050] According to a fourth aspect of the present invention, there is provided a method of mounting a rotary scale member to a mechanical part configured to rotate about a rotation axis, the rotary scale member comprising a body provided, or capable of providing, a series of position features defining a scale extending about a scale axis, and at least three integral radially compliant flexure members spaced about said scale axis, the method comprising i) positioning the annular rotary scale member on a plane of the mechanical part, said plane extending perpendicular to the rotation axis, said scale axis and said rotation axis being substantially parallel, ii) thereafter rotating one or more rotatable radial adjustment members to adjust the radial position of the rotary scale member body relative to the mechanical part. The method may be characterized in that the rotatable radial adjustment member includes a flexure engagement portion and an anchor portion, the flexure engagement portion abuts a flexure member of the rotary scale member, the anchor portion being attached to the machine part such that the flexure engagement portion can rotate about a radially fixed axis defined by the anchor portion, and rotation of the flexure engagement portion causes a radial displacement of the flexure member against which the flexure engagement portion abuts, thereby causing a radial displacement of the body of the rotary scale member. At least a majority of any radial reaction force applied to the flexure engagement portion may be reacted by the machine part via the anchor portion.

[0051] According to a further aspect of the invention there is provided a method of mounting a rotary scale member on a mechanical part configured to rotate 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 and at least three radially following bends spaced about said scale axis, the method comprising i) positioning the rotary scale member on the mechanical part such that the scale axis and the rotation axis are substantially parallel; ii) thereafter positioning at least a first radial adjustment device so as to contact both the mechanical part and the rotary scale member; and manipulating the at least first radial adjustment device to radially displace the body of the rotary scale member.

[0052] As will be appreciated, the features discussed above in relation to the first aspect of the invention are also applicable to the second, third and fourth aspects of the invention. [Brief description of the drawings]

[0053] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: [Figure 1] FIG. 1 is an isometric view of a shaft mounted disk scale member according to the present disclosure with a read head positioned to read the scale. [Diagram 2] FIG. 2 is a plan view of the arrangement of FIG. [Diagram 3] FIG. 2 is a side view of the arrangement of FIG. 1. [Figure 4] FIG. 2 is a plan view of the disk scale member of FIG. 1 shown in isolation. [Diagram 5] FIG. 5 is a detailed view of region M of the scale disc member of FIG. [Figure 6a] FIG. 6a is a cross-sectional view of a scale disc member attached to a shaft taken along line II of FIG. 2 according to one embodiment of the present invention. [Figure 6b]FIG. 6b is a cross-sectional view of a scale disc member attached to a shaft, taken along line II in FIG. 2, according to a variation of the embodiment shown in FIG. 6a. [Figure 7] FIG. 7 is a schematic diagram illustrating the steps of installing the scale disc members of FIGS. 1 to 6 of the present disclosure. [Figure 8a] FIG. 8a shows an isometric view of an alternative embodiment of a scale disc member mounted in accordance with the present invention. [Figure 8b] FIG. 8b shows an isometric view of an alternative embodiment of a scale disc member mounted in accordance with the present invention. [Figure 9] FIG. 9 is a plan view of the arrangement of FIG. 8b. [Figure 10a] FIG. 10a is a cross-sectional view of a scale disc member attached to a shaft taken along line II of FIG. 9 according to one embodiment of the present invention. [Figure 10b] FIG. 10b is a cross-sectional view of a scale disk according to a variation of the embodiment shown in FIG. 10a. [Figure 10c] FIG. 10c is a cross-sectional view of a further variation of the embodiment shown in FIGS. 10a and 10b. [Figure 11] FIG. 11 shows a plan view of an alternative embodiment of a scale disc member suitable for use in the method of the present invention. [Figure 12a] FIG. 12a is a cross-sectional view of the scale disc member attached to the shaft taken along line II in FIG. [Figure 12b] FIG. 12b is a cross-sectional view of the scale disc member attached to the shaft taken along line II-II of FIG. [Figure 13] FIG. 13 shows a plan view of an alternative embodiment of a scale disc member suitable for use in the method of the present invention. [Figure 14] FIG. 14 is a cross-sectional view of the scale disc member attached to the shaft taken along line II in FIG. [Figure 15] FIG. 15 is a plan view of an alternative embodiment of a scale disc member suitable for use in the method of the present invention. [Figure 16] FIG. 16 is an isometric view of the scale disc member of FIG. 1 attached to a different machine part 6'. [Figure 17a] FIG. 17a illustrates another alternative embodiment of the present invention which involves the use of multiple nudge blocks to adjust the radial position of the disc scale. [Figure 17b] FIG. 17b illustrates another alternative embodiment of the present invention which involves the use of multiple nudge blocks to adjust the radial position of the disc scale. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] 1-3 and 6, there is shown an encoder apparatus 2 mounted to a machine part 6 (e.g., a rotatable shaft 6) and a machine component 12 (not shown). The machine part 6 is configured to rotate about a rotation axis A. Figures 1-3 (and 6) show the encoder apparatus 2 after it has been mounted in accordance with the method of the present invention, which is described in more detail below.

[0055] As shown, in this embodiment the encoder apparatus 2 comprises a scale disc member 4 which is planar in configuration and is mounted to a machine shaft 6. Figures 4 and 5 show the scale disc member 4 of the encoder apparatus 2 in isolation.

[0056] The scale disc member 4 comprises a body / substrate 5 (in this embodiment, a planar annular disc-shaped body 5) provided on one of its planar faces with a series of position features defining a scale 8 extending around a scale axis B, and a number of integral flexures 16a, 16b, 16c, 16d. In this embodiment, the body 5 provided with the scale tracks 8 and the number of flexures 16 are formed from / formed as a single material. Forming them from a single material can be advantageous for particularly thin planar scale discs, as it helps to ensure the compactness of the scale disc, as well as to ensure that the flexures 16 are contained within the same plane as the annular body 5. In particular, in this embodiment, the scale disc member 4 (i.e., the annular body and the flexures) is formed from a thin sheet of material, about 1 mm thick, in this embodiment stainless steel. For context, the diameter of the scale disc member 4 in this embodiment is about 55 mm. As will be understood, the present disclosure is not limited to discs of such size, and such dimensions are given merely as an example of a disc. Also, the discs can be made from other metallic materials, such as aluminum or plastic. Further, in alternative embodiments the flexures may be formed separately from the body / substrate 5 of the scale disc member, but provided on a member (e.g. a hub) which is attached to the body / substrate 5 of the scale disc member. However, it is preferred that the flexures 16 are integrally formed on the body / substrate 5 (in other words a body / substrate 5 on which the scale tracks are provided and on which the flexures are formed from a single piece of material is preferred) as this not only helps to provide a particularly compact rotary scale member, but also helps to ensure that radial reaction forces are contained in the plane of the body / substrate. For example the body / substrate and the flexures may be formed (e.g. cut) from a single sheet or plate of material (e.g. a metallic material).

[0057] As shown in Figure 1, the scale track 8 extends completely and continuously in a circular manner around the scale axis B. Although not shown in detail in Figure 1, the scale track 8 comprises a series of features which can be read by the readhead 10 to determine the relative position / movement of the scale disc 4 and the readhead 10.

[0058] The read head 10 is mounted on a fixed machine component 12 such that the shaft 6 can rotate relative to it about an axis of rotation A.

[0059] In the described embodiment, the encoder device 2 is an optical encoder device, but this does not necessarily have to be the case. For example, the encoder device could be a magnetic encoder device, an inductive encoder device, or a capacitive encoder device. Furthermore, in the described embodiment, the encoder device 2 is a reflective optical encoder device (wherein light from the readhead is reflected by the scale back to the readhead, and the illumination and scale detection parts of the readhead are on the same side of the scale). However, this does not necessarily have to be the case and the encoder device could be a transmissive optical encoder (or could be a magnetic, inductive, or capacitive encoder device, as discussed above).

[0060] In this embodiment, the encoder device 2 is an incremental encoder device. Thus, in this embodiment, the scale disc 4 is an incremental scale disc, the scale track 8 comprising a series of periodically arranged features that the read head 10 can read to provide a count of the relative position / movement of the scale disc 4 and the read head 10. As is common in the field of incremental encoder devices, the scale disc device 4 may comprise one or more reference marks that can be read by a read head passing the scale disc 4, whereby the read head may identify a reference position on the disc scale member. An example of a reference mark 15 is shown in FIG. 4. In this case, the reference mark 15 is shown in a separate track 17 from the incremental scale track 8, although this does not necessarily have to be the case. The reference mark 15 may be embedded within the incremental scale track 8. The encoder device may be an absolute encoder device. Thus, the scale disc 4 may be an absolute scale disc, the scale track on the scale disc 4 comprising features that define a series of unique absolute positions, such that the absolute position of the scale disc and the read head may be determined on start-up without requiring any relative movement of the disc scale member and the read head. As will be appreciated, the absolute scale disc may also include one or more incremental scale tracks.

[0061] The installer can attach the scale disc member 4 to the machine part 6 by placing the scale disc member 4 on the machine part such that the scale axis B and the rotation axis A of the machine part are substantially parallel. In this case, the scale disc member 4 is placed on a reference plane RP (see FIG. 3) defined by a flat end face 7 of the machine part 6. As will be appreciated, the reference plane RP does not have to be provided by a plane. Instead, for example, the reference plane RP can be provided by a projecting pedestal (e.g., three hemispheres equiangularly arranged around the rotation axis A) on which the scale disc member 4 rests. It is unlikely that the installer has placed the scale disc member 4 in an ideal radial position. For example, it may be desirable for the scale disc member 4 to be placed such that the scale axis B and the rotation axis A are substantially coaxial (or have some other preferred defined relationship / offset), which, if left unchanged, may cause errors (e.g., eccentricity errors) in the signal acquired by the read head 10. It may therefore be desirable for the installer to be able to fine-tune the radial position of the scale disc member 4.

[0062] The applications and devices in which the inventors' disks are likely to be used are unlikely to require adjustments of more than 500 μm, and the range of adjustments could be as small as a few microns, or even less than a micron. One must keep in mind not only the range in which minute adjustments are required, but also the need for the installer to be able to make such adjustments in a predictable and consistent manner. Being able to make such adjustments in a predictable and consistent manner means that the installer does not have to work on a trial and error basis, which can be very time consuming and degrade the setup. Below, several different ways of implementing such an improved arrangement for adjusting the radial position of the scale disk member 4 are described.

[0063] As shown most clearly in Figure 4, the scale disc member 4 includes a hole 14 through its centre. The scale disc member 4 includes four integral radially compliant flexures 16 (a, b, c, d) which are disposed in plane with the planar disc and are equiangularly spaced around the hole 14. The flexures 16 are elastically compliant in the radial direction (with respect to the scale disc member 4). The flexures 16 may therefore be referred to as "radial spring members". As will be explained in more detail below, the flexures may be referred to as radial adjustment flexures, as they are used to assist in adjusting the radial position of the scale disc member 4.

[0064] In the exemplary embodiment of Figs. 1-6, as well as the flexures 16 following radially (e.g., along direction "R" in Fig. 5), they are also configured to follow tangentially (e.g., along direction "T" in Fig. 5). In the currently described embodiment, the tangential following is achieved by providing a specially shaped flexure. As shown most clearly in Fig. 5, the flexures 16 include a "seat" or "foot" portion 18 with which a radial adjustment device 28 is configured to engage as described in more detail below. The foot 18 extends between a pair of elongated flexure legs 20, which themselves extend from the annular body 5 into the bore 14. The foot 18 and the flexure legs 20 are formed from the same material as the annular body 5 and define a flexure gap 22. As shown in Fig. 5, a contact surface 24 is provided on the gap side of the flexure legs 18. 6 and 7, the radial adjustment device 28 can be positioned through the bent gap 22 such that a tapered head 31 of the adjustment bolt 28 can engage and press against the contact surface 24 to adjust the radial position of the annular body 5 and thus the scale 8 and scale axis B formed thereon. In the described embodiment, the tapered head 31 has a conical shape / form.

[0065] The foot 18 elastically follows the radial direction R by being flexible along its length in the plane of the disc, and the foot 18 elastically follows the tangential direction T in the plane of the disc by being flexible along its length via a pair of bending legs 20.

[0066] The bend 16, and in particular the bend foot 18 and the elongated leg 20 (and the bend gap 22), may be formed, for example, by etching and / or machining (e.g., laser cutting) the annular body 5. Optionally, the annular body 5, together with its bend 16, is formed by molding, casting and / or additive processes.

[0067] The tangential tracking of the flexures is optional, and in fact some of the flexures in the embodiments described below are not configured to be tangential tracking. Optionally, if desired, the radial adjustment device may be configured to provide tangential tracking. For example, the radial adjustment device may comprise rollers that are radially stiff but allow the disk to slide laterally in the tangential direction.

[0068] Now, with reference to FIG. 7, a method of mounting the scale disc member 4 of FIG. 1 to FIG. 6 on the machine part 6 will be described. As shown diagrammatically in FIG. 7(A) and FIG. 7(B), the method begins with the installer placing the scale disc member 4 on a reference plane RP (see FIG. 3), in this case the plane defined by the end face 7 of the machine part / shaft 6. At this point in the process, the flexures 16a, 16b, 16c, 16d are in an unflexed (i.e. relaxed) state. As shown in FIG. 7(A), the machine part 6, and in this embodiment in particular the end face 7, comprises a number of threaded holes 32, which are for receiving radial adjustment devices 28, as will be described in more detail below. As will become clear from the following description, in the embodiment of FIG. 1 to FIG. 7, each of the radial adjustment devices 28 also performs the function of a stop member. Thus, the items 28 may be referred to as radial adjustment devices / stop members 28, but for the sake of brevity, they will only be referred to as radial adjustment devices 28 in this specification.

[0069] As shown diagrammatically in Figure 7(B), the initial radial position of the scale disc member 4 is such that the rotation axis A and the scale axis B are not coaxial, but rather have a significant amount of offset such that if the scale disc member 4 were left in its initial radial position, substantial undesirable eccentricity errors would be introduced into the signal acquired by the read head 10.

[0070] Thus, once the scale disc member 4 is positioned on the reference surface RP / end face 7, the installer can verify the radial position of the scale disc member 4. This may be accomplished mechanically, for example using a dial test indicator (DTI) on the outer edge of the rotating disc. Optionally, optical methods may be used. For example, a microscope may be used to view the edge of the scale line. As another example, a pair of read heads may be configured to read the scale features, and the count difference between them may provide a measure of eccentricity. If the radial position is not satisfactory, the installer can fine-tune the radial position of the scale disc member 4. As shown in FIG. 7(C), this is achieved by the use of one or more radial adjustment devices 28, which in the described embodiment include adjustment bolts 28.

[0071] As shown in more detail in FIG. 6a, in this embodiment, the radial adjustment device 28 comprises a radial adjustment bolt 28a with an anchor portion 29 and a flexion-operated portion 31. In the illustrated embodiment, the anchor portion 29 comprises a threaded portion 29 and the flexion-operated portion 31 comprises a tapered head 31. As shown in FIG. 6, the radial adjustment bolt 28a can be received through the flexion gap 22 of the first flexion portion 16a such that the threaded portion 29 of the radial adjustment bolt 28a is received in a threaded hole 32 in the end face 7 of the shaft 6. In accordance with a typical threaded member, the radial adjustment bolt 28a can be rotated to change its axial position. FIG. 6a shows a configuration in which the radial adjustment bolt 28a is placed in the threaded hole 32 and rotated (e.g., clockwise) about the axis C until its axial position is such that the tapered side of the tapered head 31 contacts the contact surface 24 of the foot portion 18 (described above in connection with FIG. 5) of the first flexion portion 16a. As shown in Fig. 6a, the scale disc member 4 (particularly its gap 22), the machine part 6 (particularly its threaded hole 32) and the radial adjustment bolt 28a are configured such that the tapered head 31 of the adjustment bolt 28 contacts only the contact surface 24 of the foot portion 28, i.e. there is a gap between the tapered head 31 and the foot 20, and also between the tapered head 31 and the back surface 26 of the gap 22. Thus, as the radial adjustment bolt 28a rotates further about axis C to penetrate further into the threaded hole 32 (in the direction indicated by arrow P in Fig. 6a), the radial position of the radial adjustment bolt is fixed, and in particular the axis C about which it rotates is radially fixed, so that the tapered head 31 moves the contact surface 24 / foot portion 18 of the bend 16a radially inwards (in the direction indicated by arrow D), which in turn moves the body / substrate 5 of the scale disc member 4 accordingly (thereby moving the radial position of the scale 8 formed thereon and of the scale axis B accordingly).Any reaction force to such displacement (e.g. due to friction and / or resistance / reaction provided by another radial adjustment bolt / stop member, as described in more detail below) is directed to and reacted by the machine part 6 via contact between the anchor portion 32 of the radial adjustment bolt and the threaded portion of the hole 32 in the machine part, as shown diagrammatically by arrow R in FIG. 6a.

[0072] 6b shows an alternative embodiment that is substantially the same as that shown in FIG. 6a, except that the countersink feature at the mouth of the screw hole 32 of the machine part is configured to be smaller on its radial backside feature (e.g., on its right side feature 33, as seen in FIG. 6b) compared to its radial front feature (e.g., on its left side feature, as seen in FIG. 6b) such that the screw head 31 contacts the countersink feature on its backside but not on its front feature. Thus, when the radial adjustment bolt 28a rotates about axis C to penetrate it further into the screw hole 32 (in the direction shown by arrow P in FIG. 6b), the contact between the tapered head 31 and the backside 33 of the countersink feature forces the tapered head 31 radially inward, which causes the contact surface 24 / foot 18 of the bend 16a to move radially inward (in the direction shown by arrow D) and the body / substrate 5 of the scale disc member 4 to move accordingly (thereby causing the radial position of the scale 8 formed thereon and the scale axis B to move accordingly). Any reaction force to such displacement (e.g., due to friction and / or due to resistance / reaction provided by another radial adjustment bolt / stop member, as described in more detail below) is directed to and reacted by the machine part 6 via contact between tapered head 31 of the radial adjustment bolt and a countersunk feature in the mounting of hole 32 of the machine part, as illustrated diagrammatically by arrow R in FIG. 6b. As will be appreciated, in contrast to the embodiment of FIG. 6a, the radial adjustment bolt needs to have sufficient clearance within hole 32 or be sufficiently flexible / compliant so that the radial adjustment bolt can be positioned at different axial depths within hole 32 without locking up.

[0073] As shown in Figures 7(C) and 7(D), in a preferred method according to the invention, adjustment bolts 28 are also placed in the opposing flexure gaps and are initially (i.e. before any radial adjustment action is taken) set so that their tapered heads 31 contact the contact surface 24 of the foot 18 as described above in relation to Figure 6a. This is preferred because in such a configuration, the action of manipulating the "first" of the two opposing radial adjustment bolts (e.g. bolt 28a) to displace the contact surface 24 / foot 18 of the flexure it is engaging with (e.g. flexure 16a) then forces the contact surface 24 / foot 18 of the opposing flexure (e.g. flexure 16c) into the tapered head 31 of the opposing "second" radial adjustment bolt (e.g. bolt 28c). As the second radial adjustment bolt 28c is radially fixed / anchored to the machine part 6 / end surface 7 via its anchoring portion 29, it responds to said thrust. Thus, when the first radial adjustment bolt 28a is manipulated / rotated to effect a radial displacement of the body / substrate 5 of the rotary scale member 4, the second radial adjustment bolt 28c performs the function of a radial stop member. The opposing "second" flexure 16c therefore flexes to facilitate the displacement of the body / substrate 5 on which the scale is formed, but at the same time provides a radial resistance / reaction force to the displacement. This can be advantageous as it helps to provide a convenient controlled manner for the displacement D effected by manipulating the first flexure 16a by rotating the first radial adjustment bolt 28a in the opposite direction (e.g., counterclockwise) about the axis. Rotating the first radial adjustment bolt 28a in the opposite direction (e.g., counterclockwise) causes the radial adjustment bolt 28a to reverse out of the threaded hole 32, thereby reducing the extent to which its tapered head 31 displaces the contact surface 24 / foot 18 of the flexure 16a, and due to the radial reaction force provided by the opposing second radial adjustment bolt 28c, the contact surface 24 / foot 18 of the flexure 16a moves rearward (in the opposite direction to that indicated by arrow D), correspondingly displacing the body / substrate 5 of the scale disc member 4 rearward (i.e., radially outward in this embodiment).

[0074] As will be appreciated, in this embodiment, when the second radial adjustment bolt 28c is manipulated / rotated, it can also be used to effect radial displacement of the body 5 of the rotary scale member 4. As will be appreciated, during such manipulation / rotation of the second radial adjustment bolt 28a, the opposing first radial adjustment bolt 28a performs the function of a radial stop member.

[0075] To facilitate such reversibility / reversibility of radial displacement, it is not necessary that a device capable of performing the functions of both a stop member and a radial adjustment member be disposed against the opposing flexures. Instead, a dedicated stop member (i.e., one configured for the sole function of a radial stop member and not configured to be used as a radial adjustment device) may be disposed against the opposing flexures to provide such a radial reaction force. Such a dedicated stop member may comprise, for example, a rigid cylindrical peg having a cylindrical head sized to be inserted into a hole 32 in the machine part 6 / end face 7 and abut against the contact surface 24 / foot 18 of the opposing flexure. An exemplary embodiment in which a dedicated stop member is used is provided in connection with FIGS. 11 and 12.

[0076] Similar to the first 28a and second 28c radial adjustment bolts positioned relative to the opposing first 16a and second 16c bends (to provide radial adjustment in the first dimension (X dimension)) as shown in Figures 7(C) and (D), it may be necessary to position and use third 28b and fourth 28d radial adjustment bolts relative to the opposing third 16b and fourth 16d bends (to provide radial adjustment in the second dimension (Y dimension)).

[0077] In such a case, the control and predictability of radial adjustment of the disk scale member 4 in one dimension (e.g., the X dimension) via one opposing radial adjustment bolt and flexure (e.g., via the first 28a and second 28c bolts and the first 16a and second 16c flexures) may be improved by the above-mentioned tangential tracking of the other opposing flexure (e.g., the third 28b and fourth 28d flexures).

[0078] In particular, when the radial position of the scale disc member 4 is changed along the X dimension, for example by manipulation of the first radial adjustment bolt 28a, the third 16b and fourth 16d flexures bend / distort laterally in the X dimension (in particular the flexure legs 20 of the third 16b and fourth 16d flexures bend along their lengths in the plane of the scale disc member) to accommodate the change in radial position of the annular body 4 in the X dimension. Such bending of the flexures 16 means that the radial position of the annular body 5 relative to the shaft 6 can be adjusted without having to overcome static friction between the third 28b and fourth 28d radial adjustment bolts and the corresponding feet 18 of the third 16b and fourth 16d flexures.

[0079] When the scale disc member 4 is in the desired radial position, it can be fixed in place. This can be achieved, for example, by clamping and / or gluing the scale disc member 4 to the machine part 6 / end face 7. For example, one or more auxiliary fastener holes 9 can be provided through the body / substrate 5 on which the scale is provided, through which a fastener such as a clamping bolt can be passed and fixed to the shaft (e.g. via a hole in the end face 7) to clamp the annular body 5 in place. If required, the radial adjustment bolts 28 can then be removed.

[0080] An alternative embodiment of the invention will now be described with reference to Figures 8 to 10. Similar to the embodiment described above, this embodiment comprises a disk scale member 104 mounted on a machine part 6 including an end face 7 with a number of threaded holes 32 for receiving a radial adjustment device, as will be explained in more detail below. The disk scale member 104 comprises a body / substrate 105 (in this embodiment a planar annular disk-shaped body 5) provided on one of its planar faces with a series of position features defining an optical incremental scale 108 extending around a scale axis B. According to the previous embodiment, the body 105 provided with the scale tracks 108 and the number of flexures 116 are formed from a single material. The scale disk member 104 comprises a hole 114 through its centre and four integral radially following flexures 116 (a, b, c, d) provided in the plane of the planar disk and equiangularly arranged around the hole 114. The compliant bends 116 (a, b, c and d) are formed by providing openings / voids 122 in the body 105 closer to its inner circumference than its outer circumference to provide a radially weakened wall section.

[0081] The scale disc member 104 is initially positioned on the machine part 6 / end face 7 such that the scale axis (around which the scale extends) and the axis of rotation of the machine part are substantially parallel and the bends 116 (a, b, c and d) are in an unbent state. As shown in Figures 8b and 9, a radial adjustment device, in the form of a radial adjustment bolt 28 in this embodiment as in the embodiment described above, is then placed in contact with the machine part 7 and the scale disc member 104 and can then be operated to adjust the radial position of the scale disc member 104 in a controlled and predictable manner. In particular, as shown in Figure 10a, the threaded anchor portion 29 of the radial adjustment bolt 28a is received within the threaded hole 32 and rotated (e.g., clockwise) about axis C until its tapered head 31 touches the bend 116a. Thereafter, when the radial adjustment bolt 28a is rotated (e.g., clockwise) about axis C, because the radial position of the radial adjustment bolt 28 is fixed, and in particular the axis C about which it rotates is radially fixed, the tapered head 31 displaces the bent portion 116a radially outward (in the direction indicated by arrow D), which in turn displaces the body / substrate 105 of the scale disc member 4 accordingly. Any reaction force to such displacement (e.g., due to friction and / or due to resistance / reaction force provided by another radial adjustment bolt / stop member) is directed to and reacted by the machine part via contact between the anchor portion 32 of the radial adjustment bolt and the threaded hole 32 of the machine part, as shown diagrammatically by arrow R in FIG. 10a. As with the above embodiment, a suitably configured adjustment bolt 28c (or stop member) positioned against the opposing flexure means that a reaction / resistance force is generated against such displacement, thereby facilitating easy and controllable reversal of any such displacement by simply rotating the radial adjustment bolt 28a in the opposite direction (e.g., counterclockwise). Thus, this embodiment is very similar to that described above, except that in this embodiment, the radial adjustment device is not received within the flexure gap 122, and the flexure is not designed to provide substantial tangential tracking.In accordance with the above-described embodiments, one or more auxiliary fastener holes 109 may be provided through the body / substrate 105 on which the scale is provided, through which a fastener such as a clamp bolt can be passed and secured to the shaft (e.g. via a hole in the end face 7) to clamp the annular body 105 in place.

[0082] FIG. 10b illustrates an alternative embodiment that is substantially the same as that shown in FIG. 10a, except that the mechanical part 6 includes a raised central hub 6a that is engaged by a tapered head 31. Furthermore, in an embodiment, the radial adjustment device 28 further comprises a sleeve 27 located around the tapered head 31 of the radial adjustment bolt 28a. The sleeve 27 can be configured to rotate with the radial adjustment bolt 28a or can be configured to prevent the radial adjustment bolt 28 from rotating about the axis C. The sleeve 27 can be made from a different material than the tapered head 31, and thus can be made from a material such as a plastic material, to reduce friction experienced when rotating the bolt 28a about the axis C. As will be appreciated, the provision of such a sleeve or similar member is not limited to the embodiment of FIG. 10b, but is equally applicable to other embodiments described above and below. Furthermore, as will be appreciated, in other embodiments, a lubricant can be placed at the contact points between the radial adjustment device and the mechanical part to reduce friction therebetween.

[0083] When the radial adjustment bolt 28a rotates about axis C to cause it to penetrate further into the threaded hole 32 (in the direction indicated by arrow P in FIG. 10b), contact between the radial adjustment device 28 (particularly in this embodiment, its tapered head 31 / sleeve 27) and the central hub 6a causes the tapered head 31 / sleeve 27 to be pushed radially outward, which in turn displaces the bent portion 116a radially outward (in the direction indicated by arrow D), which in turn displaces the body / substrate 105 of the scale disc member 4 accordingly. Any reaction force to such displacement (e.g. due to friction and / or due to resistance / reaction force provided by another radial adjustment bolt / stop member) is directed to and reacted by the machine part 6 via contact between the radial adjustment device 28 and the central hub 6a of the machine part, as shown diagrammatically by arrow R in FIG. 10b. As will be appreciated, in contrast to the embodiment of FIG. 10a, the radial adjustment device 28 needs to have sufficient clearance within the bore 32 or be sufficiently flexible / compliant so that the radial adjustment bolts can be positioned at different axial depths within the bore 32 without locking up.

[0084] FIG. 10c shows an alternative embodiment that shares some similarities with the embodiment of FIGS. 10a and 10b, in particular in that the disk scale member 104 of FIG. 10c is identical to that of FIGS. 10a and 10b. As with the embodiment of FIG. 10b, the shaft 6 comprises a central hub 6a that extends through the hole 114 of the disk scale member 104. However, in this embodiment, the radial adjustment member 328 simply comprises a wedge-shaped member 31′ that can be press-fit between the central hub 7a and the flexure 116a so as to contact both of them. Due to the wedge shape of the radial adjustment member 328, the further it is pressed axially downwards (in the direction shown in FIG. 10c), the more it displaces the flexure 116a radially outward (in the direction shown by arrow D), which in turn displaces the body / substrate 105 of the scale disk member 4 accordingly. Any reaction force to such displacement (e.g. due to friction and / or due to resistance / reaction force provided by another radial adjustment bolt / stop member) will be directed to and reacted by the machine part 6 via contact between the radial adjustment member 328 and the central hub 6a of the machine part, as shown diagrammatically by arrow R in FIG. 10c.

[0085] 11 and 12 show another alternative embodiment of a disk scale member 204. Similar to the embodiment described above, this embodiment comprises a disk scale member 204 mounted on a machine part 6 including an end face 7 with a number of holes 232 for receiving a radial adjustment device. The disk scale member 204 comprises a body / substrate 205 (in this embodiment a planar annular disk-shaped body 205) provided in one of its planes with a series of position features defining an optical incremental scale 8 extending around a scale axis B. The scale disk member 204 comprises a hole 214 through its centre and four integral radially following flexures 216 (a, b, c, d) provided in the plane of the planar disk and equiangularly arranged around the hole 214. According to the previous embodiment, the body 205 in which the scale tracks 8 are provided, and the number of flexures 216 are formed from a single material. The flexures 216 of this embodiment are similar to those of the first embodiment (of Figures 1 to 6), except that they do not include legs 20, and therefore provide little or no substantial tangential compliance. According to the above embodiment, one or more auxiliary fastener holes 209 may be provided through the body / substrate 205 on which the scale is provided, through which fasteners such as clamp bolts can be passed and secured to the shaft (e.g. via holes in the end face 7) to clamp the annular body 205 in place. According to the other embodiments above, the scale disc member 204 is initially positioned on the machine part 6 / end face 7 such that the axis of the scale (i.e. the axis along which the scale features extend) and the axis of rotation of the machine part are substantially parallel, and the flexures 216 (a, b, c and d) are in a non-flexed state. As shown in Figures 12a and 12b, the radial adjustment device 228 is then placed into contact with the machine part 6 and the scale disc member 204 and is thereafter used to adjust the radial position of the scale disc member 204 in a controlled and predictable manner.

[0086] The radial adjustment devices 228a, 228b provided with this embodiment are different from those of the above-mentioned embodiment. As shown in Figures 11 and 12, the radial adjustment device 228 comprises a cam member 231 arranged to engage the contact surface 24 of the flexure 216a and configured to rotate about a radially fixed axis C, such that the degree to which the contact surface 24 of the flexure 216a is displaced can be controlled by the degree of rotation of the cam member 231. In this case, the cam member 231 is provided by an elliptical head portion 231 attached to an anchor portion 229. The anchor portion comprises a peg that is received in a hole 232 in the machine part 6 / end surface 7. The cam member / elliptical head portion 231 and the anchor portion 229 can be formed from a single material and configured to rotate together, in which case the anchor portion 229 and the hole 232 should have a circular cross-sectional shape (e.g., they can both be cylindrical or conical). Alternatively, the cam member / elliptical head portion 231 may be attached to the anchor portion 229 such that the cam member / elliptical head portion 231 can rotate relative to the anchor portion 229. In such a case, optionally the anchor portions 229 may be configured not to rotate within the bores 231, which may be achieved, for example, by providing them with a non-circular cross-sectional shape. FIG. 12a shows the cam member / elliptical head portion 231 in two rotational positions, with the solid lines showing the cam member / elliptical head portion 231 in the position shown in FIG. 11 (i.e., its short radius is in contact with the contact surface 24) and the phantom lines showing the cam member / elliptical head portion 231 rotated 90° (i.e., its long radius is in contact with the contact surface 24), which causes the contact surface 24, and therefore the flexure 16, to move radially inwards in the direction shown by arrow D. As with the other embodiments, any radial reaction force (e.g., due to another radial adjustment device 228b mounted to engage the opposing flexure 216c) is reacted by the machine part 6 / end face 7 via the anchor portion, as shown diagrammatically by arrow R in FIG. 12a.

[0087] In this embodiment, instead of a separate radial adjustment device being attached to the machine part 6 / end face 7 to act against the opposing flexure 216c, a dedicated stop member 250 is instead attached to the machine part 6 / end face 7 to act against the opposing flexure 216c. The dedicated stop member 250 comprises an anchor portion 252 that is received within a hole 232 in the machine part 6 / end face 7, and a cylindrical flexure stop portion 254 configured to fit snugly against the flexure 216c. Similar to the second radial adjustment bolt 28c described above in connection with Figures 7(C) and 7(D), the dedicated stop member 250 provides a radial reaction force against the radial displacement caused by the radial adjustment device, thereby facilitating an easy and controllable reversal of the radial displacement caused by the radial adjustment device 228 (i.e., can be achieved by simply rotating the radial adjustment device 228 in the opposite direction (e.g., counterclockwise)). However, in contrast to the second radial adjustment bolt 28c described above in relation to Figures 7(C) and 7(D), the dedicated stop member 250 is not configured to effect any radial displacement of the disc scale member (e.g., any manipulation / rotation of it does not cause any radial displacement).

[0088] In the above embodiment, the flexures 16 / 116 / 216 are located radially inward of the scale 8. In particular, in the above embodiment, the body / substrate 5 / 105 / 205 includes a hole 14 / 114 / 214 through its center, and the flexures 16 / 116 / 216 are located around the edge of the hole. However, this is not necessarily the case. For example, as shown in Figures 13 and 14, a scale disk member 304 is provided that is located on an end face 307 of a machine part / shaft 306. The machine part / shaft 306 is configured to rotate about a rotation axis A. The scale disk member 305 comprises a body / substrate 305 provided on one of its planar faces with a series of location features that define a scale 8 extending around a scale axis B, and a plurality of integral flexures 316a, 316b, 316c. In this embodiment, the body / substrate 305 does not include a hole extending through its center around which the flexures are provided. Instead, flexures 316a, 316b, 316c are provided radially outward of the scale 8. The flexures 316(a, b, and c) are formed by providing openings / voids 322 in the body / substrate 305 adjacent its periphery so as to provide radially weakened wall sections.

[0089] As in the above-described embodiment, the scale disk member 304 is initially placed on the machine part 306 / end face 307 such that the bends 316 (a, b, and c) are in an unbent state. Thereafter, a radial adjustment device, in this embodiment in the form of the same radial adjustment bolt 28 as in the above-described embodiment according to Figures 1 to 10, is placed on the machine part 306 so as to contact the machine part 306 and the scale disk member 304, and can then be operated to adjust the radial position of the scale disk member 304 in a controlled and predictable manner. In particular, as shown in Figure 14, the threaded anchor portion 29 of the radial adjustment bolt 28a is received in a threaded hole 332 in the machine part 306 / end face 307 and rotated (e.g., clockwise) about axis C until its tapered head 31 touches the bends 316a. Further rotation of the radial adjustment bolt 28a about axis C (e.g., in a clockwise direction) will cause the radial adjustment bolt 28a to penetrate further into the threaded hole 332 in the direction of arrow P, and because the radial position of the radial adjustment bolt 28 is fixed, and in particular the axis C about which it rotates is radially fixed, the tapered head 31 will displace the bent portion 316a radially inwards (in the direction shown by arrow D) and accordingly the body / substrate 305 of the scale disc member 304. Any reaction force to such displacement (e.g., due to friction and / or due to resistance / reaction provided by another radial adjustment bolt / stop member) will be reacted by the machine part via the radial adjustment bolt's anchor portion 32, as shown diagrammatically by arrow R in FIG. As with the above embodiment, a suitably configured adjustment bolt 28c (or stop member) positioned against another opposing bend means that a reaction / resistance force is generated against such displacement, thereby facilitating easy and controllable reversal of such displacement by simply rotating the radial adjustment bolt 28a in the opposite direction (e.g. counterclockwise).

[0090] FIG. 15 shows another alternative embodiment of a disk scale member 404. Similar to the embodiment described above, this embodiment comprises a disk scale member 404 mounted on a machine part 6 including an end face 7 having a plurality of holes 32 for receiving a radial adjustment device 28. The disk scale member 404 comprises a body / substrate 405 (in this embodiment a planar annular disk-shaped body 405) provided in one of its planes with a series of location features defining an optical incremental scale 8 extending about a scale axis. The scale disk member 404 comprises a hole 414 through its centre and three integral radially compliant flexure pairs 416 (a, b, c) flush with the planar disk and equiangularly arranged around the hole 414. The scale disk member is thus similar to that described above, except that each radially compliant flexure is provided via a pair of cantilevered flexures rather than comprising a single flexure. Such flexure pairs could also be used, for example, in place of the single flexure structure shown in the other embodiments above. According to the above-mentioned embodiment, the scale disc member 404 is first placed on the machine part 6 / end face 7 such that the flexures 416(a, b, c) are in an unflexed state. Thereafter, a radial adjustment device, in this embodiment in the form of the same radial adjustment bolt 28 as in the above-mentioned embodiment according to Figs. 1 to 10, is then placed in contact with the machine part 6 and the scale disc member 404 (in this embodiment the flexure pairs 416a, 416c) and can then be operated to adjust the radial position of the scale disc member 404 in a controlled and predictable manner. According to the above-mentioned embodiment, one or more auxiliary fastener holes 409 may be provided through the body / substrate 405 on which the scale is provided, through which a fastener such as a clamping bolt can be passed and fixed to the shaft (e.g. via a hole in the end face 7) to clamp the annular body 405 in place.

[0091] FIG. 16 shows an embodiment in which the disk scale member 4 according to FIG. 1 is mounted on a machine part 6′ having a part 6″ extending through a central hole 14. However, the diameter of the part 6″ extending through the central hole is smaller than the smallest possible diameter that can be defined by the flexures 16. As in the above-mentioned embodiment, the scale disk member 4 is first placed on the machine part 6 / end face 7 such that the flexures 16 (a, b, c, d) are in a non-flexed state. Thereafter, a radial adjustment device, in this embodiment in the form of a radial adjustment bolt 28 the same as in the above-mentioned embodiment according to FIGS. 1 to 10, is then placed in contact with the machine part 6 and the scale disk member 4 (in this embodiment, the flexures 16) and is then operated to adjust the radial position of the scale disk member 4 in a controlled and predictable manner. Thus, as in all the above-mentioned embodiments, the flexures are not directly radially compressed between the radial adjustment device and any part of the machine part, and therefore the rotary scale member is not directly radially clamped to the machine part by the flexures.

[0092] In the above embodiment, the radial adjustment member is in direct contact with the flexures, in particular with the feet of the flexures. However, this is not necessarily the case. For example, the radial adjustment member could be in contact with the body of the rotary scale member (e.g. its outer circumferential surface / periphery) and one or more stop members could be arranged to contact one or more flexures.

[0093] Figures 17a and 17b show an alternative embodiment. The scale disc member 1300 of this embodiment comprises a planar annular body 1302 with a scale track 1304 provided in one of its planar faces and a hole 1306 through its centre through which the central hub portion 6a of the shaft 6 can extend when the scale disc 1300 is attached to the shaft 6. As in the embodiment of Figure 15, the scale disc member 1300 comprises three pairs of radially compliant cantilever spring members 1308a, 1308b, 1308c that are flush with the planar scale disc 1300 and equally spaced around the edge of the hole 1306. A flexure gap 1310a, 1310b, 1310c is provided directly behind each pair of cantilever spring members 1308a, 1308b, 1308c.

[0094] In contrast to the above embodiment, the flexures 1308 are shaped and sized such that the effective diameter of the holes 1306 is slightly smaller than the diameter of the central hub portion 6a of the shaft 6 to which it is attached. The scale disc member 1300 must therefore be forcefully attached to the central hub 6a, thereby radially deflecting the flexures 1308 into their respective flexure gaps 1310. When the scale disc member 1300 is forcefully attached to the central hub 6a, there is a natural / default / automatic interference fit between them.

[0095] In contrast to the embodiment of Figure 15, the flexure gap 1310 is not configured to receive an adjustment bolt that can adjust the radial position of the disk. In contrast, in the embodiment shown in Figures 17a and 17b, the radial adjustment device comprises one or more nudge blocks 1320a, 1320b, 1320c and associated grub screws 1326. The nudge blocks comprise rigid blocks having a threaded hole 1322 extending therethrough and an abutment feature in the form of a lip 1324 having a thickness sufficient to fit into the gap between the central hub 6a and the inner edge of the hole 1306 of the scale disk member 1300. To adjust the radial position of the scale disc member 1300, the nudge block 1320 is positioned such that its lip 1324 is received in the gap between the shaft 6 and the inner edge of the bore 1306 of the scale disc member 1300, and then the grub screw 1326 is inserted into the threaded hole 1322 and tightened via the tool 1328 until it engages the central hub 6a. At that point, further tightening of the grub screw 1326 forces the nudge block radially outward, resulting in the lip 1324 radially displacing the scale disc member 1300. Such radial displacement causes a change in the bending state of the flexure 1308, and thus a change in the extent to which the flexure 1308 is pressed against the central hub 6a, and therefore the magnitude of the radial reaction force opposing the displacement generated by the flexure 1308 varies depending on the degree of radial displacement of the scale disc member 1300 from its initial radial position. As can be seen, in this embodiment the stop against which the flexures 1308 are pressed radially is provided by an integral part of the machine part, i.e. the central hub 6a. The radial reaction force to the displacement (e.g. due to friction and / or due to the resistance / reaction force provided by one or more of the flexures 1308 pressing against the central hub 6a) is then directed to and reacted by the machine part 6 via contact between the grub screw 1322 of the radial adjustment device and the central hub 6a.

[0096] As will be appreciated, in the embodiment shown, two nudge blocks 1320a, 1320b are shown in place / engaged with the scale disc member 1320 and shaft 6. A third nudge block 1320c is shown out of engagement with the scale disc member 1320 and shaft 6 illustrating its various portions as well as the grub screw 1326 and tool 1328. It may be that only one nudge block is required to provide the desired radial adjustment. Optionally, three nudge blocks may be used if desired.

[0097] 11, 13, and 15 show configurations in which at least one of the flexures does not have a radial adjustment member or stop member disposed thereagainst. While this is feasible, it is also feasible for those embodiments to have such a radial adjustment member or stop member disposed thereagainst, if desired.

[0098] Although the above described embodiments relate to a disk-scale type rotary scale member, in which the scale features are provided on a planar surface of the rotary scale member, this does not necessarily have to be the case: instead, for example, the rotary scale member could be of a ring-scale type, in which the scale features are provided on an axially extending surface, for example on a circumferential (e.g. cylindrical) edge of the rotary scale member.

[0099] In the above embodiment, the radial adjustment device is operated by rotating it about an axis (axis C). However, this is not necessarily the case. For example, the radial adjustment device may include a press-fit device. For example, the radial adjustment device may comprise a plunger member having a bend-operating portion in the form of a tapered head and an anchor portion in the form of an elongated stem (e.g., like a conventional golf tee). The anchor portion may be configured to fit snugly within the hole 32, 232, 332 of the machine part 6, 206, 306 / end face 7, 207, 307 to radially fix the radial adjustment device relative to the machine part 6, 206, 306 / end face 7, 207, 307, and the depth of the radial adjustment device may be controlled (e.g., via a push or pull force) to control the extent to which the tapered head displaces the bend portion.

Claims

1. 1. A method of mounting a rotary scale member to a machine component configured to rotate about a rotation axis, the rotary scale member comprising a body provided, or capable of providing, a series of scale features defining a scale extending about a scale axis, and at least three radially following bends spaced about the scale axis, the method comprising: i) positioning the rotary scale member on the machine component such that the scale axis and a rotation axis are substantially parallel; ii) thereafter, positioning at least a first radial adjustment device in contact with both the mechanical part and the rotary scale member, and manipulating the at least a first radial adjustment device to radially displace the body of the rotary scale member; Including, wherein at least one of the bends is generated as a result of interaction with a radially biased radial stop member, and at least a majority of any radial reaction force imparted by the rotary scale member on the at least first radial adjustment device in opposition to the radial displacement of the rotary scale member is directed to and reacted by the mechanical part via contact between the at least first radial adjustment device and the mechanical part.

2. The method of claim 1 , wherein in step i), the at least three bends are in an unbent state.

3. The method of claim 1 or 2, further comprising fixing the radial stop member to the machine part adjacent at least one of the bends.

4. The method of claim 1 , wherein the radial stop member comprises a radial adjustment device.

5. 5. The method according to claim 1, wherein the at least a first radial adjustment device is arranged to contact one of the flexures of the rotary scale member, and wherein manipulating the at least a first radial adjustment device causes a radial displacement of the flexure and thereby a radial displacement of the body of the rotary scale member, and the radial reaction force is generated by interaction of at least one other of the flexures with a radial stop member against which it is radially pressed.

6. 6. The method of claim 5, wherein at least the flexures in contact with the radial adjustment device being manipulated are not in radial compression between the radial adjustment device and any portion of the machine component.

7. 7. The method according to claim 1, wherein at least one of the flexures defines a flexure gap between the body of the rotary scale member and the portion of the flexure configured to contact a radial stop member / radial adjustment device.

8. The method of claim 7 , wherein the portion of the radial stop member / radial adjustment device that contacts the flexure resides within the flexure gap.

9. 9. The method according to claim 1, wherein the radial adjustment device comprises a rotatable member rotatable about a radial adjustment device axis, the rotatable member being configured such that rotation of the rotatable member causes a change in the radial displacement of the body of the rotary scale member.

10. 10. The method of claim 9, wherein the radial adjustment device comprises a tapered member configured such that rotation of the rotatable member about the radial adjustment device axis changes the axial position of the tapered member along the radial adjustment device axis which in turn controls an extent of radial displacement of the body of the rotary scale member.

11. 11. The method of claim 10, wherein the rotatable member of the radial adjustment device includes a threaded member received by a threaded hole in the machine component, and rotation of the threaded member changes the axial position of the tapered member along the radial adjustment device axis.

12. The method of claim 11 , wherein the tapered member and the threaded member are a single piece.

13. 13. The method according to any one of claims 9 to 12, wherein the radial adjustment device is fixed to the machine part such that an axis of the radial adjustment device is radially fixed relative to the machine part.

14. 14. The method of any one of claims 1 to 13, wherein the rotary scale member comprises a disk scale member including a plane on which the series of scale features defining a scale are or can be provided, and the scale axis extends perpendicular to the plane.

15. 1. An apparatus comprising: a rotary scale member; and a mechanical part configured to rotate about a rotation axis, 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, and at least three radially following flexures spaced about the scale axis, the rotary scale member being arranged on the mechanical part such that the scale axis and the rotation axis are substantially parallel, the apparatus further comprising at least a first radial adjustment device arranged to contact both the mechanical part and the rotary scale member and configured to be operated to radially displace the body of the rotary scale member, wherein a displacement of the at least first radial adjustment device by the rotary scale member generated as a result of interaction of at least one of the flexures with a radially pressed radial stop member, opposing the radial displacement of the rotary scale member, is directed towards and reacted by the mechanical part via the contact between the at least first radial adjustment device and the mechanical part.

16. The apparatus described in claim 15, wherein the radial stop member is provided with a radial adjustment device.

17. An apparatus as described in claim 15 or 16, wherein the at least a first radial adjustment device is arranged to contact one of the flexures of the rotary scale member, the at least a first radial adjustment device is configured to be operable to cause radial displacement of the flexure, thereby causing radial displacement of the body of the rotary scale member, and the radial reaction force is generated by interaction of at least one other of the flexures with a radial stop member against which it is radially pressed.

18. The apparatus of claim 17, wherein at least the flexure in contact with the radial adjustment device being manipulated is not radially compressed between the radial adjustment device and any portion of the mechanical component.

19. An apparatus as described in any one of claims 15 to 18, wherein at least one of the flexures defines a flexure gap between the body of the rotary scale member and the portion of the flexure configured to contact a radial stop member / radial adjustment device.

20. The apparatus of claim 19, wherein the portion of the radial stop member / radial adjustment device that contacts the flex portion is located within the flex gap.

21. An apparatus as described in any one of claims 15 to 20, wherein the radial adjustment device comprises a rotatable member rotatable about a radial adjustment device axis, the rotatable member being configured such that rotation of the rotatable member causes a change in the radial displacement of the body of the rotary scale member.

22. The apparatus of claim 21, wherein the radial adjustment device comprises a tapered member, wherein rotation of the rotatable member about the radial adjustment device axis changes the axial position of the tapered member along the radial adjustment device axis, which in turn controls the degree of radial displacement of the body of the rotary scale member.

23. The apparatus described in claim 22, wherein the rotatable member of the radial adjustment device includes a threaded member received by a threaded hole in the mechanical part, and rotation of the threaded member changes the axial position of the tapered member along the radial adjustment device axis.

24. The apparatus of claim 23, wherein the tapered member and the threaded member are a single part.

25. An apparatus as described in any one of claims 21 to 24, wherein the radial adjustment device is fixed to the mechanical part such that an axis of the radial adjustment device is radially fixed relative to the mechanical part.

26. An apparatus as described in any one of claims 15 to 25, wherein the rotary scale member includes a disk scale member including a plane in which the series of scale features defining the scale are or can be provided, and the scale axis extends perpendicular to the plane.

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