Encoder

Abstract

A sealed encoder module for mounting to a machine to measure relative displacement of first and second portions of the machine. The sealed encoder module may include a scale, a read head including a scale signal receiver, and a one-piece protective housing encapsulating at least the scale and the scale signal receiver. The sealed encoder module may be configured to determine and output diagnostic information regarding a scale signal detected by the read head.

Description

[0001] This application is a divisional application of the Chinese patent application with application number 201680070951.3, application date December 1, 2016, and invention name Encoder.

[0002] The present invention relates to an encoder device. For example, the present invention relates to an encoder commonly known as a sealed encoder, also commonly known as a closed encoder.

[0003] Encoders are used in many industries to provide position (or a derivative thereof, such as velocity and / or acceleration) feedback to a machine's control system, for example, feedback control of the position / motion of one part of a machine relative to another part of the machine. As will be appreciated, typically a scale is provided on one part of the machine and a readhead for reading the scale is provided on another part of the machine, so that the relative position of the scale and the readhead (and therefore the relative position of the machine part) can be detected by the readhead along the measurement dimension of the encoder.

[0004] The technology used by such encoders may require that the environment in which they are used is clean and free from contamination such as dust, dirt and moisture (which may be oil and / or water based, for example). Contamination on the scale and / or readhead may adversely affect the performance of the encoder. In many industries, the machines in which the encoders are used operate in a reasonably clean environment, in which case encoders commonly referred to as "exposed encoders" (or "open encoders") may be used. The readhead of an exposed / open encoder may include a visual setting indicator (see, for example, TONiC available from Renishaw plc). TM and RESOLUTE TM encoder, and see also US 5241173 and US8505210).

[0005] However, there are instances, such as in the machine tool industry, where the working environment is not clean and where fluids and solid debris are prevalent. In such cases, there may be a need to protect the encoder's scale and readhead from such a hostile environment. As is known, this can be achieved by installing a protective cover on the exposed / open encoder (such as in the TONiC 1000 encoder available from Renishaw plc). TM or RESOLUTE TMThis is achieved by placing a cover on the encoder to provide a sealed barrier to protect the scale and readhead from such contamination. However, typically, in these cases, a different type of encoder is used, which is often referred to as a sealed (also known as a closed) encoder. Such a sealed / closed encoder includes a scale and readhead, and an integral protective housing encapsulating the scale and at least the scale signal receiving portion of the readhead, and the scale, readhead and integral protective housing are provided together and mounted as a single module.

[0006] The present invention provides an improved encoder device. Specifically, the present invention relates to an improvement of a sealed encoder. For example, according to the present invention, a sealed encoder module is provided, the module comprising: a scale, a read head and a protective housing (for example, an integrated protective housing).

[0007] According to a first aspect of the present invention, there is provided a sealed encoder module for mounting on a machine to measure the relative displacement of a first and a second part of the machine in a measurement dimension / degree of freedom (the measurement dimension / degree of freedom may be, for example, linear or rotational). The sealed encoder module may comprise: a scale, a read head comprising a scale signal receiver, and a protective housing encapsulating at least the scale and the scale signal receiver. The sealed encoder module may be configured to determine and output diagnostic information. The diagnostic information may indicate the relative arrangement of the scale and the scale signal receiver, specifically in at least one dimension / degree of freedom other than the measurement dimension / degree of freedom of the encoder module. Accordingly, the diagnostic information may depend on the relative arrangement of the scale and the scale signal receiver, specifically in at least one dimension / degree of freedom other than the measurement dimension / degree of freedom of the encoder module. The sealed encoder module may be configured to determine and output diagnostic information about a scale signal detected by the read head. Accordingly, as explained in more detail below, the scale signal detected by the readhead may depend on the relative arrangement of the scale and the scale signal receiver in at least one dimension / degree of freedom other than the measurement dimension / degree of freedom of the encoder module. As will be appreciated, the encoder module (e.g., the readhead) is also configured to determine and output information about the relative position of the scale and the readhead (i.e., position information in the measurement dimension / degree of freedom). Accordingly, the encoder module may be configured to determine and output both position information and diagnostic information.

[0008] Determining and outputting diagnostic information has been found to be particularly useful for monitoring the performance of a sealed encoder module and / or for assisting in the installation / setup of a sealed encoder module; for example, for those sealed encoder modules having a scale signal receiver arranged independently of the scale, as described in more detail below.

[0009] Accordingly, the sealed encoder module may include at least one processor configured to determine the diagnostic information. As will be appreciated, the processor may include a custom processor configured for a specific application (e.g., a field programmable gate array "FPGA") and a more general processor that may be programmed (e.g., via software) as needed for the application in which it is used. The at least one processor may be configured to analyze a scale signal detected by a read head in order to determine the diagnostic information. The at least one processor or at least another one of the processors may be configured to control the output of the diagnostic information. For example, the at least one processor or at least another one of the processors may be configured to control the operation of an output device (e.g., a visual output device) based on the results of the analysis of the scale signal. The position and diagnostic information may be determined by the same or different processors.

[0010] As will be appreciated, the encoder module may be configured such that the diagnostic information determined and output may include information about the quality of the scale signal detected by the readhead. The diagnostic information may provide a measure of the suitability of the representation to provide position information (e.g. in the measurement dimensions / degrees of freedom); and in particular, for example, reliable and / or accurate position information. Outputting the diagnostic information may include providing an output based at least in part on at least one parameter, the at least one parameter being determined according to a process configured to analyze the quality of the scale signal. For example, control of an output device (such as a visual output device) may be based on the at least one parameter.

[0011] The diagnostic information output may be limited to one of a plurality of predetermined categories. These categories may represent different quality levels of the detected scale signal. For example, the diagnostic information may be limited to indicating whether the detected scale signal is bad or good. As will be appreciated, additional / alternative categories may be available, such as acceptable and / or optimal. Accordingly, the encoder module may be configured to determine and output the category to which the scale signal belongs. For example, in an embodiment in which at least one parameter is determined via a process of analyzing the quality of the detected scale signal, the method may include (e.g., via the use of a predetermined threshold) determining which category the parameter belongs to. Optionally, one or more visual output devices (such as, a light emitter) may be controlled to reflect the determined category (e.g., the color of the emitted light may depend on the determined category).

[0012] As will be appreciated, the diagnostic information need not necessarily be limited to one of a plurality of predetermined categories. Instead, for example, in embodiments where at least one parameter is determined via a process of analysing the quality of the detected scale signal, the determined raw parameter may be output as diagnostic information.

[0013] As mentioned above, the diagnostic information may depend on (and therefore indicate) the relative arrangement of the scale and the scale signal receiver, specifically in at least one dimension / degree of freedom other than the measurement dimension of the encoder module. For example, the diagnostic information may depend on (and therefore indicate) any one, any combination, or all of the lateral position, ride height, pitch, roll, or yaw of the scale and the scale signal receiver relative to each other. Accordingly, for example, the diagnostic information may depend on (and therefore indicate) when the scale and the scale signal receiver are in or when they are not in a desired relative arrangement in at least one degree of freedom other than the measurement dimension. Such arrangement information may be particularly useful for providing those embodiments in which the scale signal receiver is arranged independently of the scale, as described in more detail below.

[0014] Optionally, the portion of the encoder module that is movable relative to the scale may be configured to determine and output the diagnostic information. For example, optionally, the read head may be configured to determine and output the diagnostic information. Accordingly, optionally, the read head may include the at least one processor.

[0015] Optionally, the encoder module is configured to output diagnostic information in the form of one or more human detectable signals. The sealed encoder module may include at least one output device for outputting the diagnostic information as a human detectable signal. The output device may output a signal indicative of the diagnostic information. The output device may include a visual output device. The output device may be configured to emit an optical signal. Optionally, the at least one output device is disposed on the reader. Optionally, the at least one output device is disposed on the protective housing. As described in more detail below, the reader may include a mounting block outside the protective housing, the mounting block being used to mount the reader to one of the first movable part and the second movable part of the machine, and the output device may be disposed on the mounting block.

[0016] Optionally, the encoder module is configured to output diagnostic information in the form of one or more electronic signals. For example, the encoder module can be configured to output diagnostic information to an external device. Accordingly, the encoder module can include an interface for transmitting the electronic signal (e.g., wirelessly or along a wire).

[0017] The scale signal may be a signal detected by one or more sensors (e.g. in a readhead) configured to (and used in use to) detect the scale in order to determine the measure of the relative displacement of the first and second parts of the machine (in a measurement dimension / degree of freedom). The scale signal may be a detected signal from a scale, the detected signal being used to determine the measure of the relative displacement of the first and second parts of the machine. The scale signal may be an incremental scale signal. Accordingly, the diagnostic information may be determined from the output of an incremental signal sensor of the readhead. The incremental scale signal may be an interference fringe. The scale signal may be a reference mark signal. Accordingly, the diagnostic information may be determined from the output of a reference mark signal sensor of the readhead. The scale signal may be an absolute scale signal. The scale signal may be an image of the scale (e.g. a one-dimensional or two-dimensional image of the scale). Accordingly, the diagnostic information may be determined from the output of an image sensor of the readhead. In other words, the diagnostic information may be determined from an image of the scale (e.g. a one-dimensional or two-dimensional image).

[0018] Optionally, the scale signal used to determine the diagnostic information is not a signal used to determine the measurement of relative displacement. Optionally, the scale signal that determines the diagnostic information is detected by at least one sensor other than the sensor(s) whose output is configured to determine the measurement of relative displacement of the first and second parts of the machine. Such a sensor may be referred to as a "diagnostic sensor". Accordingly, in other words, the encoder module may be configured such that the output of the diagnostic sensor is not used to determine the measurement of relative displacement of the first and second parts of the machine.

[0019] As will be appreciated, the protective housing can be an integral part of a sealed encoder module. At least one of the scale and the reader can be mounted to the protective housing. The sealed encoder module can be configured so that at least one of the scale and the scale signal receiver is configured to be mounted to a part of a machine (the position of which will be measured by the sealed encoder module) via a protective housing. The housing can be configured to be mounted to a part of a machine. The protective housing may include one or more mounting features, and the scale and / or scale signal receiver are configured to be mounted to a part of a machine via the mounting features. Accordingly, optionally, the protective housing can be located between the scale and a part of the machine, and the encoder module is configured to be mounted to a part of the machine. Optionally, the protective housing can be located between the scale signal receiver and a part of the machine, and the encoder module is configured to be mounted to a part of the machine.

[0020] A seal (e.g., at least one sealing lip) may be provided between relatively movable parts of the sealed encoder module. For example, between the protective housing and a relatively movable read head (described in more detail below). Optionally, the protective housing comprises a plurality of (e.g., a first and a second) relatively movable parts. Optionally, the plurality of (e.g., a first and a second) relatively movable parts of the housing are configured to be mounted to respective different parts of a machine, the relative positions of the respective different parts to be measured by the sealed encoder module. A seal (e.g., at least one sealing lip) may be provided between relatively movable parts of the protective housing. Optionally, the scale is mounted to a first part of the protective housing, and the read head may be mounted to a second part of the protective housing.

[0021] Optionally, the scale or the scale signal receiver is mounted to a first portion of the protective housing (e.g., an axis portion), the first portion being configured to be mounted to an axis of the machine and being configured to be rotatable relative to a second portion of the protective housing, the other of the scale and the signal receiver being attached to the second portion. Optionally, at least one compliant sealing ring is disposed between the first portion and the second portion of the protective housing. Optionally, a first compliant sealing ring and a second compliant sealing ring are disposed between the first portion and the second portion of the protective housing. The first compliant sealing ring and the second compliant sealing ring may be disposed on opposite sides of the scale / scale signal receiver.

[0022] The scale signal receiver can be configured to be biased / abutted against the scale and / or a portion of the protective housing to which the scale is attached. Accordingly, the sealed encoder module can include an "integrated bearing" (and is therefore referred to as an "integrated bearing", or "guided" encoder module). However, this need not necessarily be the case. For example, the scale signal receiver can be arranged inside the protective housing independently of the scale and the protective housing. Accordingly, the encoder module can be described as an encoder module "without an integrated bearing" or "without bearings". Accordingly, as will be understood, the scale signal receiver can also be described as "externally restricted" or "non-guided". Viewed another way, the scale signal receiver remains suspended (in other words, in a suspended state) within the protective housing.

[0023] Optionally, the scale signal receiver and the protective housing are movable relative to each other along the measurement dimension of the scale. Optionally, the scale signal receiver may be located within (and protected by) the protective housing but not mounted to the protective housing. Optionally, a seal allows relative movement of the scale signal receiver and the protective housing along the measurement dimension of the scale. Accordingly, as described in more detail below, the seal may extend along the measurement dimension. The seal may also accommodate relative movement of the scale signal receiver and the protective housing in other dimensions.

[0024] Optionally, the arrangement of the scale and the scale signal receiver (in at least one degree of freedom other than along the encoder measurement dimension) is selectively adjustable. For example, optionally, at least one or any combination of the lateral position, ride height, pitch, roll or yaw of the scale and the scale signal receiver relative to each other can be selectively adjusted. Accordingly, optionally, the encoder module can include an adjustment mechanism for facilitating such adjustment. Additionally or alternatively, such adjustment can be facilitated by features via which the scale and / or the readhead are mounted to the respective part of the machine. For example, the features via which the scale and / or the readhead are mounted to the respective part of the machine can allow a certain flexibility in the positional relationship of the scale and the scale signal receiver in the at least one degree of freedom. Such adjustability can be particularly useful for those embodiments in which the arrangement of the scale signal receiver inside the protective housing is independent of the scale and the protective housing (e.g., "without integral bearing" / "non-guided" / "bearingless" / "externally restricted", etc.).

[0025] Optionally, the scale signal receiver is located within the protective housing (and protected by the protective housing), but is not mounted to the protective housing. In this case, the protective housing may include a seal through which the scale signal receiver can be connected to a portion outside the protective housing. As will be appreciated, the portion outside the protective housing (to which the scale signal receiver can be configured to be connected) may be a part of a machine, which will be determined relative to the position / movement of another portion of the machine (to which the scale is fixed). The scale signal receiver may be connected to a portion of the machine located outside the protective housing via a mounting member. In those embodiments (in which the arrangement of the scale signal receiver inside the protective housing is independent of the scale and the protective housing), the scale signal receiver may be rigidly connected to a portion of the machine located outside the protective housing. Accordingly, the mounting member may be a rigid mounting member. Accordingly, the rigid connection / rigid mounting member may be configured such that the position and orientation of the scale signal receiver within the protective housing may be specified (and controlled) in all six degrees of freedom by a portion external to the protective housing to which the scale signal receiver is configured to be attached. For example, in an embodiment where the reader includes a mounting feature (described below), the position and orientation of the scale signal receiver within the protective housing may be specified (and controlled) in all six degrees of freedom by the mounting feature (e.g., by a mounting block on which the mounting feature is disposed). For example, the scale signal receiver may be rigidly fixed to a rigid reader mounting member that passes through the seal. Accordingly, the position and orientation of the scale signal receiver on a first side of the seal (inside the protective housing) may be specified (and controlled) by the reader mounting member.

[0026] Optionally, the protective housing comprises at least one (eg elongate, preferably linear) compliant sealing member through which the scale signal receiver can be mounted to a part of the machine.

[0027] The mounting may be provided by a part of the machine to which the scale signal receiver is to be attached. For example, the machine itself may comprise a (rigid) mounting bracket which is inserted into the protective housing and connected to the scale signal receiver. Optionally, the read head may comprise a read head mounting comprising one or more mounting features located outside the protective housing, the one or more mounting features being used to secure the read head to a part of the machine. As will be appreciated, the read head may be configured to be releasably fastened to a part of the machine. The one or more mounting features may be provided on a mounting block. The mounting features may comprise, for example, holes through which releasable fasteners (e.g. bolts) may pass into and / or through (and preferably engage) the holes. As will be appreciated, the scale signal receiver of the read head may be rigidly connected to the read head mounting (as explained above, the read head mounting may be rigid so as to ensure a rigid connection between the scale signal receiver and a part outside the protective housing). As will be appreciated, the scale signal receiver, readhead mounting and blade may be formed as a single monolithic structure, or may comprise a plurality of separately formed units rigidly connected to each other.

[0028] The mounting member may include a (e.g., rigid) blade-shaped member that is configured to extend through the seal. In those embodiments where the read head includes a read head mounting member as described above, the blade-shaped member may extend through the seal between a scale signal receiver and a mounting feature, the scale signal receiver being located inside the protective housing, and the mounting feature being located outside the protective housing. The blade-shaped member may include a first edge and a second edge (in other words, a leading edge and a trailing edge). The blade-shaped member may taper toward the first edge and the second edge. The blade-shaped member may include an internal passage / channel for wires and / or air to pass between the interior and exterior of the protective housing, for example, between a scale signal receiver and a mounting block having one or more mounting features disposed thereon.

[0029] The protective housing may include one or more mounting features for mounting the protective housing to a portion of a machine (e.g., to different portions of the machine to which the scale signal receiver is configured to be mounted, the portions of the machine being relatively movable relative to each other). The one or more mounting features may be configured to facilitate releasable mounting of the protective housing. The mounting features may include holes into which releasable fasteners (e.g., bolts) may extend (and preferably engage) and / or pass.

[0030] As will be appreciated, the scale signal receiver may be part of a readhead located inside the protective housing and receiving a signal from the scale. The scale signal receiver may include one or more components for interacting with the scale signal, for example, to detect the scale signal and / or manipulate the scale signal before it is subsequently detected. For example, in the case of an optical encoder, the scale signal receiver may include one or more optical elements, such as a diffractive optical element and / or a refractive optical element. For example, the scale signal receiver may include one or more lenses and / or one or more diffraction gratings. The scale signal receiver may include one or more signal guides for guiding the scale signal to another component. For example, in the case of an optical encoder, the scale signal receiver may include a waveguide, such as an optical guide (e.g., an optical fiber). The signal guide may be configured to transmit the scale signal to a subsequent component that interacts with the scale signal, for example, to manipulate the scale signal. The signal guide may be configured to transmit the scale signal to one or more detectors / sensors (e.g., transducers) configured to detect the scale signal.

[0031] Optionally, the readhead includes one or more sensors for sensing the scale signal (which, as described above, may or may not be operated by one or more components in the readhead). The sensor may include a plurality of sensor elements (e.g., an array of sensor elements). The scale signal receiver may include (a plurality of) sensors. Optionally, the (a plurality of) sensors may be located elsewhere in the readhead. For example, the sensor may be located in a portion of the readhead that is external to the protective housing. For example, in those embodiments where the readhead includes a mounting block (described in more detail below), the (a plurality of) sensors (and indeed any other components described above) may be located in the mounting block.

[0032] In those embodiments where the scale signal receiver comprises a housing (described in more detail below), the scale signal receiver may include one or more features for enabling signals from the scale to enter the scale signal receiver. For example, in the case of an optical encoder, the scale signal receiver may include a window.

[0033] The readhead may include one or more transmitters for transmitting energy towards the scale. For example, the readhead may include at least one light source configured to illuminate the scale (e.g., using light in the infrared to ultraviolet range). The scale signal receiver may include the one or more transmitters. Optionally, the one or more transmitters may be provided by another part of the readhead (e.g., external to the protective housing, such as by a mounting block).

[0034] Optionally, the readhead, e.g. the scale signal receiver (e.g. its sensor(s)) is configured to detect a signal generated by light from the scale. Optionally, the light has been transmitted through the scale. Optionally, the light has been reflected from the scale. Accordingly, optionally, the readhead (e.g. the scale signal receiver) comprises an emitter (e.g. a light source) and a sensor. The emitter and sensor may be located on the same side of the scale. Accordingly, the encoder may be a reflective encoder device.

[0035] As will be appreciated, the scale will have some form of features / markings which can be read by a readhead for determining displacement, position (or derivatives thereof, such as velocity and / or acceleration). Such features may define a pattern. For example, an incremental scale may include scale features / markings which define a periodic pattern and which may be used to generate a periodic signal at a readhead (e.g. when relative displacement occurs between the scale and the readhead). The scale may be elongate. The scale may include a substrate in and / or on which features / markings are formed.

[0036] Optionally, the encoder device is a diffraction-based encoder device. Optionally, the scale includes features configured to diffract light (in the ultraviolet to infrared range), which light is used to form a resulting signal on a sensor in the readhead. Optionally, the readhead includes one or more optical elements configured to interact with the light before and / or after the scale to form a signal on a sensor in the readhead assembly. Optionally, the readhead includes one or more lenses and / or one or more diffraction gratings. Optionally, the readhead includes a diffraction grating configured to interact with light from the scale to form interference fringes on a sensor in the readhead. Optionally, the sensor includes an electrical grating, which includes two or more groups of interdigital sensors, each group configured to detect a different phase of the interference fringes.

[0037] Optionally, the scale comprises absolute scale features defining a (eg continuous) series of uniquely identifiable positions along the length of the scale.

[0038] Optionally, the readhead is configured to detect an image of a scale. Optionally, the readhead (e.g., the scale signal receiver) comprises at least one imaging optical element configured to form an image of the scale on a sensor. Optionally, the readhead comprises at least one sensor suitable for capturing an image, for example, at least a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor.

[0039] As will be appreciated, references to optical and references to light in this application are intended to refer to electromagnetic radiation (EMR) in the ultraviolet to infrared range inclusive.

[0040] As will be appreciated, the readhead may be configured to determine and output information about the relative position of the scale signal receiver and the scale (referred to herein as "position information"). Optionally, the readhead comprises one or more processor devices configured to process outputs from one or more detectors / sensors, for example to form the position information. The position signal may be incremental position information. For example, the position signal may comprise a quadrature signal. Optionally, the position signal comprises absolute position information. The one or more processor devices may be located in the scale signal receiver and / or in another part of the readhead assembly (e.g. in a readhead mounting).

[0041] The encoder device may include a magnetic encoder device, an inductive encoder device, a capacitive encoder device and / or an optical encoder device. Accordingly, the scale may include a magnetic scale, an inductive scale, a capacitive scale and / or an optical scale. Optionally, the encoder device includes an optical encoder device.

[0042] The scale may comprise a rotating scale. The rotating scale may comprise what is commonly known as a disc scale (where the scale features are provided on the surface of the disc). The rotating scale may comprise what is commonly known as an annular scale (where the scale features are provided on the circumferential edge of the disc). Optionally, the scale is arcuate. Optionally, the scale may comprise a linear scale.

[0043] Optionally, the encoder module has a nominal ride height of not less than 0.1 mm (e.g. not less than 0.2 mm, e.g. not less than 0.5 mm). Optionally, the encoder device has a nominal ride height of not more than 5 mm (e.g. not more than 2 mm, e.g. not more than 1 mm). Optionally, the encoder module has an allowable ride height variation ("tolerance") of not less than + / - 50 μm (micrometers), optionally not less than + / - 75 μm (micrometers), e.g. at least + / - 100 μm (micrometers).

[0044] The protective shell may be elongated. The protective shell may be substantially straight. The protective shell may include a substantially tubular form. The cross-sectional shape of the tubular protective shell does not necessarily have to be circular, but may, for example, include other regular or irregular shapes. For example, the cross-sectional shape of the tubular protective shell may be substantially rectangular. Optionally, the protective shell is circular, such as a perfect circle, such as a ring.

[0045] The seal can extend along the measurement dimension of the encoder device. Optionally, the seal is provided by an airflow, for example, through a gap in the protective housing, and / or, for example, via a positive (e.g., air) pressure inside the protective housing. Optionally, the seal comprises a physical barrier. The seal may include a plurality of (e.g., a pair of) sealing members. For example, the seal may include a plurality of (e.g., a pair of) sealing lips (e.g., the sealing lips may be elongated or annular / ring-shaped). In those embodiments in which the scale signal receiver can be configured to be connected to a part of a machine located outside the protective housing via a mounting member, the mounting member may pass through the seal (e.g., between the sealing lips). For example, the above-mentioned blade-shaped member may pass through the seal (e.g., between the sealing lips).

[0046] Optionally, the seal (e.g., multiple sealing lips) is compliant. Optionally, the seal (e.g., multiple sealing lips) is elastic. For example, the seal (e.g., multiple sealing lips) is sufficiently compliant so that the relatively movable part of the encoder module can move relative to each other. For example, the seal can allow the scale / protective housing and the scale signal receiver to move relative to each other, for example by allowing the member (e.g., blade-shaped member) and the protective housing / seal to move relative to each other. Optionally, the seal (e.g., multiple sealing lips) is biased toward the sealing configuration, for example, by its elasticity. The seal (e.g., multiple sealing lips) can include, for example, polyurethane, such as thermoplastic polyurethane, and / or fluorinated elastomer.

[0047] The readhead may include at least one vibration control device. Such an apparatus may be particularly beneficial for those embodiments in which the scale signal receiver is arranged independently of the scale (e.g., the scale signal receiver is "externally constrained"), as described in more detail below. As will be appreciated, such a vibration control device may be configured to reduce the vibration susceptibility of the readhead (e.g., the scale signal receiver). The vibration control device may be a device configured to reduce the response of at least a part of the system (e.g., the scale signal receiver of the readhead) due to an external excitation. The vibration control device may include at least one component configured to vibrate independently of the readhead (e.g., independently of the scale signal receiver). The vibration control device may include at least one component configured with a resonant frequency, the resonant frequency being independent of the part of the readhead assembly (e.g., the scale signal receiver) located inside the protective housing. Optionally, the vibration control device includes at least one component configured with a resonant frequency that is different from the resonant frequency of the part of the readhead located inside the protective housing (e.g., different from the resonant frequency of the scale signal receiver).

[0048] The vibration control device may include a tuned mass damper. The tuned mass damper may be tuned so as to reduce the amplitude of vibrations of at least a portion of the tuned mass damper mounted in the read head assembly (e.g., at least at the scale signal receiver), the amplitude of vibrations being at and around the resonant frequency of the portion. The tuned mass damper may include at least one spring element. The tuned mass damper may include at least one damper element. The tuned mass damper may include at least one mass element. The stiffness "k" of the at least one spring, the damping coefficient "c" of the at least one damper, and the mass "m" of the at least one mass may be selected (in other words, "tuned") so as to reduce the amplitude of vibrations of at least a portion of the tuned mass damper mounted in the read head assembly (e.g., at least the scale signal receiver), the amplitude of vibrations being at and around the resonant frequency of the portion.

[0049] The scale signal receiver may include a housing. The housing may be configured to protect the components of the scale signal receiver located inside the protective housing from contamination (e.g., solids or fluids, such as swarf or coolant, or, for example, moisture) that happens to enter the protective housing. Specifically, the housing may be configured to provide protection from fluids (e.g., liquids). The housing may enclose the components. The components may include electrical components, including any wires and / or any printed circuit boards. The components may include the above-mentioned components configured to interact with the scale signal. The housing may be a sealed body, for example, a hermetic sealed housing.

[0050] Accordingly, the sensor element portion of the scale signal receiver may be housed within a sealed body / housing. In other words, the electrical and / or other component portions of the scale signal receiver used, for example, when detecting the scale signal may be housed within a sealed body / housing. For example, in the case of an optical encoder device, optical components (such as lenses, diffraction gratings, beam steering devices or beam splitters) may be housed within a sealed body / housing. The read head transmitter (e.g., a light transmitter) may be housed within a sealed body / housing. A window (e.g., a sealed window) in the sealed body / housing may be provided for allowing the scale signal to enter the sealed body / housing.

[0051] Other optional features of the housing are explained below in conjunction with the second aspect of the invention and are not repeated here for the sake of brevity, but are equally applicable to the first aspect and other aspects of the invention, and vice versa.

[0052] According to a second aspect of the present invention, there is provided a sealed encoder module for installation on a machine so as to measure the relative displacement between a first part and a second part of the machine, the sealed encoder module comprising: a scale, a read head comprising a scale signal receiver, and a protective shell encapsulating at least the scale and the scale signal receiver, wherein the scale signal receiver comprises a shell in which one or more components of the read head are accommodated.

[0053] Providing a housing to the scale signal receiver can help ensure that one or more components of the scale signal receiver (i.e. components for enabling detection of the scale signal, such as electronic components and / or other components for generating and / or interacting with, for example, sensing and / or manipulating a signal from the scale) are protected even when contamination manages to enter the protective housing. In particular, the housing may be configured to provide protection against fluids (e.g. liquids). This may improve the reliability and life of the encoder device. Such components may include electronic components, including any wires and / or any printed circuit boards. Such components may include sensors. Such components may include components that interact with the scale signal (e.g. for manipulating a signal from the scale before the scale signal is sensed by a sensor of a readhead). Such components may include a transmitter, such as a light transmitter, for example for illuminating the scale. In the case where the encoder device comprises an optical encoder device, the optical component(s) of the scale signal receiver may also be located inside the housing.

[0054] The housing may be a rigid housing. Such a rigid housing may be configured to protect the one or more components (including any wires and / or any printed circuit board) from solid objects entering the protective housing. The housing may be substantially box-shaped. For example, the housing may have a substantially rectangular cross-sectional profile. The housing may be provided with a gap / internal volume, and one or more components of the scale signal receiver are located within the gap / internal volume. The housing may provide a structure (e.g., a load-bearing structure) on which one or more components of the scale signal receiver are mounted. The housing may be (may be configured to be) mounted to one of the first and second parts of the machine. This may be via the protective housing. This may be via a readhead mounting, for example, as described above in conjunction with other aspects of the present invention. For example, the housing may be mounted to one of the first and second parts of the machine via a mounting block. In an embodiment where the protective housing includes a seal, the scale signal receiver may be connected to a portion of the exterior of the protective housing through the seal, and the housing may include a portion extending through the seal. For example, in an embodiment where there is a blade-shaped member (as described above), the blade-shaped member may be a part of the housing. Specifically, the blade-like member may contain and protect wires or other electronic / optical components from contaminants that enter the protective housing.

[0055] As will be appreciated, the housing may comprise a plurality of components, for example a body and a cover, which together define an interior volume within which one or more components of the readhead are contained.

[0056] The housing may enclose at least all of the electronic components of a scale signal receiver (including any wires and any printed circuit board) located within the protective housing. In the case of an optical encoder, the housing may enclose all of the optical components (e.g. any combination of one or more lenses, diffraction gratings, beam splitters, light sources and beam redirectors) for detecting scale signals except for the outside of one or more windows through which the scale signal enters the housing and / or light from a light emitter passes through the outside of the one or more windows and leaves the housing towards the scale. Accordingly, as will be appreciated, any such window may form part of the housing. Alternatively, any electronic components including a protective shell or body (e.g. bare electronics shielding the electronic components) may themselves form part of the housing.

[0057] The encoder device may comprise a reflective optical encoder device. In such an embodiment, the light source for illuminating the scale and the detector for detecting the scale may be located on the same side of the scale. In such an embodiment, the same (eg single) housing may comprise the light source and the detector.

[0058] Preferably, the housing provides at least 4 levels of solid particle protection and at least 4 levels of liquid inlet protection according to the International Protection Marking (also known as the Ingress Protection Marking) of the International Electrotechnical Commission (IEC) standard 60529. In other words, preferably, the housing has an IP rating of at least IP44. The housing may provide at least 5 levels of solid particle protection, optionally at least 6 levels. The housing may provide at least 5 levels of liquid inlet protection, optionally at least 6 levels, such as at least 7 levels. In other words, the housing may have an IP rating of IPxy, wherein x (which relates to solid particle protection) is at least 4 (e.g., 4 to 6) and y (which relates to liquid inlet protection) is at least 4 (e.g., 4 to 7). As will be appreciated, the above and following features explained in conjunction with other aspects of the invention are equally applicable to this aspect of the invention, and vice versa.

[0059] According to a third invention of the present invention, there is provided an encoder device, the encoder device comprising a scale and a readhead assembly movable relative to each other, the readhead assembly comprising a scale signal receiver, the scale and the scale signal receiver being located within a protective housing, the protective housing being configured to protect the scale and the scale signal receiver from contamination located outside the protective housing, and comprising a seal, through which the scale signal receiver can be connected to a portion of the exterior of the protective housing, wherein the arrangement of the scale signal receiver inside the protective housing is independent of the scale and the protective housing. As will be appreciated, the above and following features explained in conjunction with other aspects of the present invention are equally applicable to this aspect of the present invention, and vice versa.

[0060] According to a fourth invention of the present invention, there is provided a readhead assembly for an encoder device (e.g., comprising at least one sensor for sensing a scale feature), the readhead assembly comprising at least one vibration control device, the vibration control device being configured to reduce the vibration susceptibility of at least a portion of the readhead assembly (e.g., a scale signal receiving portion). Accordingly, the present application describes a readhead for an encoder device, the readhead comprising at least one sensor for sensing a scale feature and at least one vibration control device configured to vibrate independently of the rest of the readhead. Providing the readhead with at least one vibration control device can control vibrations from a machine on which the readhead is mounted and transmitted to the readhead. This is particularly useful when the readhead is mounted to the machine via a structure susceptible to vibration (e.g., via an elongated member). As will be appreciated, the above and following features explained in conjunction with other aspects of the present invention are equally applicable to this aspect of the present invention, and vice versa. Accordingly, for example, the readhead may comprise a scale signal receiver. The scale signal receiver may comprise at least one vibration control device. In those embodiments where the scale signal receiver is mounted via an elongate blade, the scale signal receiver and / or the elongate blade may include at least one vibration control feature.

[0061] According to a fifth aspect of the invention there is provided a machine comprising an encoder device and / or a readhead as described above.

[0062] According to another aspect of the present invention, there is provided a method of setting a sealed encoder module, the sealed encoder module for measuring the relative position of two relatively movable parts of a machine in a first degree of freedom, the sealed encoder module comprising: a scale, a read head including a scale signal receiver, and an integral protective housing encapsulating at least the scale and the scale signal receiver, wherein the sealed encoder module is configured to determine and output diagnostic information, the method comprising using the diagnostic information to determine whether the scale and the scale signal receiver are in a desired relative position relationship in at least one degree of freedom other than the first degree of freedom. The method may include: an operator adjusting the relative position of the scale and the scale signal receiver in response to an indication that the scale and the scale signal receiver are not in a desired relative position relationship in at least one degree of freedom other than the first degree of freedom. According to the above and below descriptions, the diagnostic information may be presented to the operator via a light emitter. Accordingly, the method may include: the operator adjusting the relative position of the scale and the scale signal receiver in response to the output of the light emitter (e.g., in response to the color of light emitted by the light emitter).

[0063] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0064] Figure 1a Schematically illustrates a sealed encoder according to an aspect of the present invention;

[0065] Figure 1b Schematically shows Figure 1a A sealed encoder, wherein a portion of the protective housing is cut away to show a scale and a scale sensor assembly located inside the protective housing;

[0066] Figure 1c It runs through Figure 1a Cross section of a sealed encoder device;

[0067] Figure 1d Schematically shows Figure 1a A sealed encoder, wherein a portion of the protective housing is cut away to show a scale and a scale sensor assembly located inside the protective housing;

[0068] Figure 2a and Figure 2b is a schematic diagram of another embodiment of a sealed encoder device according to one aspect of the present invention, wherein a portion of the protective housing is cut away to show a scale and a scale signal receiver located inside the protective housing;

[0069] Figure 2c It runs through Figure 2a and Figure 2b Cross section of a sealed encoder device;

[0070] Figure 2d is a cross section through an alternative embodiment of a sealed encoder device;

[0071] Figure 3 is an illustration of another alternative embodiment of a read head assembly suitable for use with a sealed encoder, wherein a portion of a signal receiving module is cut away to expose internal components thereof;

[0072] Figure 4 yes Figure 3 A diagram of a signal receiving module of a sealed encoder device;

[0073] Figure 5 yes Figure 3 and Figure 4 An illustration of a tuned mass damper for a signal receiving module;

[0074] Figure 6a and Figure 6b An alternative way of implementing a vibration control device on a read head assembly is shown;

[0075] Figure 7a and Figure 7b Still another way of implementing a vibration control device on a read head assembly is shown;

[0076] Figures 8a to 8c Schematically shows a further way of implementing a vibration control device;

[0077] Figure 9a and Figure 9b schematically illustrates a rotating embodiment of the present invention; and

[0078] Fig.10a and Fig.10b An alternative embodiment of a rotary encoder implemented according to the invention is shown.

[0079] First reference Figure 2a to Figure 2d, there is a sealed encoder module 102 according to the present invention. The sealed encoder module 102 comprises a scale 104 having a plurality of features (not shown) and a read head assembly 103, the read head assembly comprising a scale signal receiver 106 for receiving signals from the scale. In the described embodiment, the sealed encoder module 102 is an optical encoder, wherein the read head assembly 103 uses electromagnetic radiation (EMR) in the infrared to ultraviolet range to read the scale 104. Specifically, in this embodiment, the position measuring encoder device is an optical absolute encoder. Accordingly, the scale comprises a series of uniquely identifiable features (e.g., a code) that the read head assembly 103 can read and process in order to determine a unique position along the length of the scale 104. However, as will be appreciated, the position measuring encoder device is not necessarily an absolute encoder. For example, it may be an incremental optical encoder. Furthermore, the encoder device is not necessarily an optical encoder, for example the encoder device may be a magnetic encoder, or for example an inductive encoder.

[0080] The read head assembly 103 communicates with an external processor device (not shown) (e.g., a controller) via a communication channel, which in the described embodiment includes a physical connection (e.g., cable 105) rather than a wireless connection. The communication channel can be bidirectional, such that the read head assembly 103 can receive data (e.g., instructions) from the external processor device and send data (e.g., position information / signals) to the external processor device. Power to the read head assembly 103 can also be supplied via a physical connection (e.g., via cable 105). However, this need not necessarily be the case. For example, the read head assembly 103 can include an internal power source such as a battery.

[0081] The scale 104 and the scale signal receiver 106 are located inside a protective housing 108, which protects them from contaminants outside the protective housing. The scale 104 is fixed to the protective housing 108, and the scale signal receiver 106 can move along the length of the scale 104 within the protective housing 108. In use, the protective housing 108 will be fastened to a first part of the machine (not shown), and the scale signal receiver 106 will be fastened to a second part of the machine (not shown). As will be understood, the first part and the second part of the machine can move relative to each other. The read head assembly further includes a mounting block 114 and a blade 116, the mounting block will be directly fastened to the second part of the machine (for example, via one or more releasable fasteners, such as bolts passing through holes 115), and the blade is connected to the mounting block 114 and the scale signal receiver 106 and extends between them. A light source 113 is provided on one end of a mounting block 114 and is used (as explained in more detail below in conjunction with other embodiments of the invention) to relay diagnostic information about the encoder to an operator / installer.

[0082] The protective housing 108 further includes a seal 111 in the form of a pair of sealing lips 112, which seals the interior of the protective housing 108 where the scale 104 and the scale signal receiver 106 are located from external contaminants. A blade 116 passes between the pair of sealing lips 112. The sealing lips 112 are compliant so as to be able to separate to allow the blade 116 and therefore the scale signal receiver 106 to move along the length of the protective housing 108 and therefore along the scale 104, but also have sufficient elasticity to close together around the blade 116, thus forming a physical barrier to solid and fluid (particularly liquid and moisture) contaminants. In other words, when the blade 116 moves between the sealing lips 112 along the length of the seal, the blade separates the sealing lips 112, and the sealing lips have sufficient elasticity to close together when there is no blade 116.

[0083] The arrangement of the scale signal receiver 106 within the protective housing is independent of the scale 104 or the protective housing 108. The scale signal receiver is rigidly connected to the mounting block 114. Specifically, the scale signal receiver 106 is rigidly connected to the blade 116, which in turn is rigidly connected to the mounting block 114. Accordingly, the position of the scale signal receiver 106 in all degrees of freedom is specified by the position of the mounting block 114, and therefore by the position of the second part of the machine (the position of the second part of the mounting block 114 is fixed in use), rather than by the position of the scale 104 or other parts inside the protective housing 108.

[0084] In the described embodiment, the position and movement of the scale signal receiver 106 are not restricted or guided in any way by the scale 104 or the protective housing 108. Due to the rigid mounting between the scale signal receiver 106 and the mounting block 114, the position and movement of the scale signal receiver 106 in all six degrees of freedom are restricted and guided by the position and movement of the mounting block 114, and therefore by the position and movement of the part of the mounting block 114 that is fixed to the machine. Accordingly, the position and movement of the scale signal receiver 106 can be described as "externally restricted". In addition, the scale signal receiver 106 does not rest against the scale 104. Accordingly, this sealed encoder can be described as "without an integral bearing", or "bearingless". We believe this to be a novel arrangement for a sealed encoder (and is the subject of a co-pending PCT patent application entitled "Encoder Apparatus" having the same priority date and priority as the present application) and in contrast to known arrangements such as sealed "integral bearing" linear encoders which bias / abut the scale signal receiver against the scale and provide a compliant coupling between the scale signal receiver and its mounting block. Figure 1a to Figure 1d The embodiment shown in describes an example of such an "integrated bearing" arrangement. This arrangement can be described as being "internally constrained".

[0085] As will be appreciated, if desired, an adjustment mechanism may be provided for adjusting the relative position of the scale signal receiver 106 relative to the mounting block 114 (e.g., the scale signal receiver may be connected to the blade 116, and / or the blade 116 may be mounted to the mounting block 114 via a joint that facilitates selective adjustment of its relative position in at least one linear degree of freedom and / or one rotational degree of freedom, such as by manipulation of a micro / flat head screw). Such a selective adjustment mechanism may be useful to assist in the set-up / alignment of the encoder device. However, as will be appreciated, such a selective adjustment mechanism will still provide a rigid connection between the scale signal receiver 106 and the readhead mount 114, and therefore a rigid connection between the scale signal receiver 106 and the portion of the machine to which it is mounted (i.e., such that during use / operation, the position / orientation of the scale signal receiver 106 in all degrees of freedom is still controlled / dictated by the second portion of the machine to which the mounting block 114 is mounted).

[0086] In the described embodiment, the scale signal receiver 106 does not contact the scale 104 at all, nor does it contact the protective housing 108. Accordingly, there is always a gap around the scale signal receiver 106, between the scale signal receiver and the scale 104 and the inside of the protective housing 108. In fact, as shown, in the described embodiment, the only contact between the readhead assembly 103 (which includes the scale signal receiver 106 and the readhead mount 110) and the protective housing 108 is between the blade 116 and the pair of sealing lips 112. As will be appreciated, the pair of sealing lips 112 are compliant and resilient in behavior and yield to accommodate the blade 116, and therefore do not restrict or control the position of the scale signal receiver 106.

[0087] Furthermore, in the described embodiment, the scale signal receiver 106 comprises a housing 107, inside which the electronic components of the scale signal receiver are positioned. A sensor of the scale signal receiver 106 for detecting the scale signal from the scale 104 and any associated components (e.g., optical components, such as lenses, diffraction gratings and / or mirrors) for forming the scale signal on the sensor may also be provided inside the housing 107 of the scale signal receiver. The housing 107 is configured (e.g., sealed) such that if contamination does inadvertently pass through the lip seal 112, the components of the scale signal receiver 106 (particularly the electronic components and optical components) inside the housing 107 are protected.

[0088] As will be appreciated, in embodiments providing a housing 107, a window (e.g. Figure 3 and Figure 4 108) so as to enable the scale signal to reach the sensor located inside the housing 107. Optionally, the window has no substantial effect on the scale signal (e.g. its sole purpose may be to simply allow the signal from the scale to enter the housing 107 without contributing to the form of the signal received at the read head sensor). Optionally, the window may be configured to redirect the signal from the scale (e.g. the window may include a reflector). Optionally, the window may be configured to interact with the signal from the scale to produce the desired signal detected at the sensor. For example, the window may include a diffraction grating and / or a lens. In any case, as will be appreciated, the exterior of the window 232 will not be sealed from any contamination entering the protective housing 108, as it forms part of the housing 107, but the interior of the window and any other components (e.g. optical components) configured to manipulate the signal from the scale 104 are protected from contamination.

[0089] The benefits of providing the scale signal receiver 106 with a housing 107 may be beneficial not only for embodiments where the scale signal receiver 106 is arranged independently relative to the scale (e.g. "bearingless", or "externally constrained"), but also for embodiments where the scale signal receiver is biased against the scale (e.g. mounted to the readhead mount via an articulated link, and the position of the scale signal receiver is "internally constrained") (including "integrated bearings") (e.g. in conjunction with Figure 1a to Figure 1d Accordingly, as will be appreciated, in conjunction with this aspect, a method such as combining Figure 1a to Figure 1d described articulated linkage. However, while the provision of the housing 107 may improve the resilience of an enclosed encoder having an "integrated bearing" (e.g. an encoder having an "internally confined" scale signal receiver), if contamination does penetrate the sealing lip 12 and lands on the scale, this may adversely affect the performance of the encoder device. For example, if sufficient contamination lands on scale features, this may adversely affect the signal from the scale. Additionally, if solid contamination such as swarf enters the protective housing and lands on the track(s) along which the read head bearing 20 travels, this may adversely affect the relative position / orientation of the scale signal receiver and the scale because the scale signal receiver rides over the dirt. Of course, an enclosed encoder having a scale signal receiver that is arranged independently of the scale (e.g. "externally confined") has the additional benefit of not being affected by such problems.

[0090] As explained in more detail below in conjunction with other embodiments of the present invention, the scale signal receiver 106 receives a signal from the scale that is processed to provide a position signal to an external device (such as a machine controller), for example via the cable 105. For example, the processing for determining the position may be performed by one or more processor devices in the scale signal receiver 106 and / or by one or more processor devices in another part of the readhead assembly (such as the mounting block 114). Optionally, the blade 116 includes one or more channels to enable wires to pass between the scale signal receiver 106 and the mounting block 114. Alternatively, wireless communication may be used, or a wired connection external to the blade 116 may be used. If the blade 116 includes one or more channels, air (e.g., supplied via the air supply line 109) may pass through the blade 116 (e.g., via a hole in the blade 116) to the scale signal receiver through the interior of the protective housing 108.

[0091] As will be understood, Figures 2a to 2dis schematic, and typically the separation between the scale 104 and the scale signal receiver 106 (commonly referred to as the ride height) may be much smaller than shown. The desired ride height will depend on the encoder, but for example, a typical ride height for an optical encoder may be in the range of 0.24 mm to 2 mm. In the particular example described, the nominal ride height is 0.8 mm with a tolerance of + / - 0.15 mm.

[0092] Figures 2a to 2d The sealed encoder module 102 shown in FIG. 1 may be used in any orientation. Figures 2a to 2d , the mounting block 114 is shown as being positioned directly above the scale signal receiver 106 and the protective housing 108. However, this need not necessarily be the case. For example, the sealed encoder module 102 may be mounted on its side or even inverted (so that the mounting block 114 is positioned directly below the scale signal receiver 106 and the protective housing 108). In fact, such an arrangement may be advantageous because any external contamination will tend to fall off the lip seal 112 of the protective housing 108 due to gravity.

[0093] Likewise, it is not necessary to arrange the pair of sealing lips 112 directly on the side of the protective housing 108 opposite to the side of the protective housing 108 where the scale is located. Figure 2c In the orientation shown in FIG. 1 , the sealing lip 112 can be disposed on one of the vertical sides of the protective housing so that the blades 116 extend horizontally rather than vertically. Alternatively, the sealing lip can be disposed between the two sides along one of the corners / edges of the protective housing, such as Figure 2d As shown (as shown in this embodiment, the sealing member 111 includes two pairs of sealing lips 112).

[0094] Reference now Figures 3 to 5 , another read head assembly 203 is shown. Figures 3 to 5 The read head assembly 203 shares many similarities with the read head assembly 103 of Figure 2, and includes, for example, a scale signal receiver 206, a mounting block 214, a light emitter 213, and a blade 216 that provides a rigid connection between the scale signal receiver 206 and the mounting block 214 (correspondingly, the scale signal receiver 206 is "externally constrained"). Figure 3 The read head assembly 203 is shown separately, but as will be appreciated, the read head assembly 203 is intended for reading a scale located inside a protective housing, such as Figures 2a to 2d Accordingly, it is also intended that the scale signal receiver 206 will also be located inside the protective housing, and the blade 216 will pass through an elongated seal in the protective housing, such as a pair of sealing lips. Figures 2a to 2dAs in the embodiment of FIG. 2 , the scale signal receiver 206 is an optical read head, but this need not necessarily be the case.

[0095] Like the scale signal receiver 106 of FIG. 2 , Figure 3 and Figure 4 The scale signal receiver 206 includes a protective housing 207. In this case, the components within the scale signal receiver 206 are protected (e.g., sealed) by the protective housing 207 and a mounting surface 217 disposed at the end of the blade 216 near the scale signal receiver 206, and the scale signal receiver 206 is mounted to the blade 216 via the protective housing and the mounting surface. A sealing member may be provided at the interface between the housing 207 and the mounting surface 217 (e.g., a gasket may be sandwiched between the housing 207 and the mounting surface 217 of the blade 216).

[0096] As shown, in addition to the blade 216 extending vertically between the scale signal receiver 206 and the mounting block 214 (as in the configuration of FIG. 2 ), in this embodiment, the blade extends at a non-vertical angle (e.g., approximately 45 degrees) between the scale signal receiver 206 and the mounting block 214. This allows the blade to be oriented so that any liquid that falls on it will fall off the sealing lip, regardless of whether the sealed encoder module is mounted vertically or horizontally.

[0097] like Figure 3 and Figure 4As shown, an optical unit 230 including components of a scale signal receiver for detecting a scale signal is shown. Specifically, the optical unit includes a light source 252 for illuminating the scale, a lens 254 configured to image the scale, a sensor 256 (e.g., a one-dimensional or two-dimensional CCD or CMOS sensor) on which the image falls and configured to detect the image, and a beam redirector 258 configured to direct light from the light source onto the scale. As shown, the sensor 256 can be mounted on a printed circuit board (PCB) 240. A cable (not shown) connects the PCB 240 to a processor device inside the mounting block 214. When the sensor obtains an image, the image is transmitted to a processor device located inside the mounting block 214, which processes the image in order to determine a position (in a known manner, for example, as explained in US2012 / 072169, the contents of which are incorporated herein by reference). The determined position is then communicated to an external device (such as, for example, a machine controller) via one or more signals transmitted along the cable 205. As will be appreciated, other arrangements are possible. For example, all processing may be performed by one or more processor devices located in the scale signal receiver 206. In another alternative embodiment, a sensor device (e.g., CCD or CMOS) may be located in the mounting block and may receive the scale signal via a light guide (e.g., optical fiber) extending through the blade 216. Accordingly, in this case, the scale signal receiver 206 simply collects the signal / light from the scale and passes it to a sensor located elsewhere in the readhead assembly.

[0098] As described above, an optical transmitter 213 ( Figure 2a to Figure 2d 113 in the embodiment of the present invention). Such a light emitter can be used to relay diagnostic information to the operator / installer. For example, the color and / or brightness of the light emitted by the light source is controlled to replay the diagnostic information. Optionally, the light emitter can be configured to flash in a specific manner to relay the diagnostic information. Accordingly, for example, during the setting of the encoder, which may occur at the installation or at a subsequent point (for example, at a subsequent point it may be necessary to set the encoder again), the diagnostic information (for example, the output of the light emitter) can be used by the operator / installer to ensure that the encoder is correctly set. Specifically, for those embodiments in which the scale signal receiver is arranged independently of the scale, the operator can use the diagnostic information to check whether the scale signal receiver has been arranged at the desired position relative to the scale (in degrees of freedom other than the measurement dimension), and if not, adjust the positional relationship accordingly.

[0099] For example, the light emitter may be controlled so as to emit a visual signal that depends on the relative setting of the readhead (e.g. scale signal receiver) and the scale. This may be particularly useful during installation of the encoder module in order to confirm that the readhead is receiving a good signal from the scale. For example, the encoder module may be configured so that the color of the light emitter 213 depends on the relative setting (e.g., green light may be emitted when the readhead is receiving a good / strong scale signal, and red light may be emitted when the readhead is receiving a poor / weak signal). Such a visual indication of the relative setting of the readhead and scale may be useful for both "independently arranged" and "internally constrained" encoder modules. Such a visual indication of the relative setting of the readhead and scale may be particularly useful when (as described above) an adjustment mechanism is provided to adjust the relative setting position of the scale signal receiver relative to the mounting block.

[0100] In the described embodiment, the processor inside the mounting block 214 for determining position is also configured to process the image detected by the sensor 256 in order to determine diagnostic information (however, as will be appreciated, this need not be the case; a separate processor may be used). In the described embodiment, the processor is configured to determine diagnostic information based on the signal quality detected by the sensor. In this particular embodiment, the processor is configured to perform a Fourier Transform on the image obtained by the sensor at the fundamental spatial frequency ω characteristic of the scale (which may be set during the setup of the encoder module or by analyzing the image). The Fourier transformed magnitude A is then established. As will be appreciated, the Fourier transform provides a real part R and an imaginary part T, and the magnitude A may be calculated by the following equation:

[0101] A = or A 2 = [R(F(ω))] 2 + [T(F(ω))] 2 (1)

[0102] Where F(ω) represents the Fourier transform at the spatial frequency ω.

[0103] Since calculating square roots is computationally intensive, it is understandable that using A 2 Instead of A, it may be preferable to determine that the setting indicator output may be preferred. The method then includes setting A (or A 2 ) is compared with a threshold value to determine how to control the light emitter 213. For example, when A (or A 2 ) has a value lower than the threshold, the light emitter can be controlled to output red light, and when A (or A 2 ) has a value higher than the threshold, the light emitter can be controlled to output green light.

[0104] As will be appreciated, A (or A 2 ) depends on the amplitude of the feature obtained in the representation. This in turn is affected by the setting of the readhead relative to the scale (which is to be determined). A (or A 2 ) also depends on the number of features in the representation. Accordingly, if there is a significant variation in the density of features along the scale, the method may include a step of compensating for this. For example, this compensation may be achieved by changing A (or A 2 ) divided by the number of features in this representation.

[0105] In the described embodiment, the method involves Fourier transforming a representation that is substantially at the fundamental spatial frequency of the feature. The Fourier transform may use an assumed fundamental spatial frequency of the feature based on the scale it is using. Even if the assumed fundamental frequency is not exactly correct, the method may still provide a useful indication of the quality of the representation. Optionally, the fundamental spatial frequency of the feature may be determined by analyzing the image prior to performing the Fourier transform. This may be useful in embodiments where the actual fundamental spatial frequency of the feature as imaged varies significantly due to ride height / magnification effects.

[0106] Furthermore, as will be appreciated, it is not necessarily the case that the Fourier transform is performed substantially at the fundamental spatial frequency of the feature. For example, the method may involve performing the Fourier transform at some other frequency (e.g., at a harmonic of the spatial frequency). Alternatively, the method may involve performing the Fourier transform at one or more frequencies and comparing the magnitude of the Fourier transform at different spatial frequencies.

[0107] Additional details of how images of an absolute scale may be processed to determine diagnostic information are described in US 8505210, the contents of which are incorporated herein by reference. As will be appreciated, there are other ways in which diagnostic information may be determined. For example, as described in US 8505210, the relative amplitudes of different types of scale features as imaged may be determined, which relative amplitudes may be indicative of the quality of the detected scale signal.

[0108] As shown, in this embodiment, the scale signal receiver 206 also includes a vibration control device (in fact, this embodiment includes multiple vibration control devices), which in this particular embodiment includes a tuned mass damper 260. We, the inventors, have found that the use of at least one vibration control device can improve the life and / or metrological performance of the encoder device. This is particularly the case when the scale signal receiver is rigidly mounted to the structure via a member that is susceptible to vibration (e.g., a member that transmits and / or amplifies vibrations), such as a slender arm or thin blade to which the scale signal receiver is rigidly mounted. For example, in the case of the "externally constrained" scale signal receiver of the above embodiment, vibrations are transmitted to the scale signal receiver via a rigid mounting arrangement. The vibration control device provides a way to control the unwanted vibrations to which the scale signal receiver is exposed.

[0109] As will be appreciated, a vibration control device may be a device configured to reduce the response of a system (e.g., a scale signal receiver) due to an external excitation. As described above, in this particular example, the vibration control device includes a tuned mass damper 260 that is tuned to reduce the amplitude of vibration in the system in which it is installed at and around the resonant frequency of the system. As will be appreciated, a tuned mass damper includes a spring, a damper, and a mass. The spring stiffness "k", the damping coefficient "c" of the damper, and the mass "m" of the mass are selected (in other words "tuned") to reduce the amplitude of vibration in the system in which it is installed at and around the resonant frequency of the system. In this embodiment, the tuned mass damper includes a pair of elastic rings 262 (e.g., rubber rings) that provide spring and damping elements and a body 264 that provides a mass element. Accordingly, each elastic ring 262 acts as a spring and a damper by absorbing energy and converting the energy into heat. The body 264 comprises a sufficiently dense material (eg, brass) such that the body 264 has a sufficiently small size while providing a suitably high mass.

[0110] Typically, the mass of the tuned mass damper needs to account for a significant percentage of the mass of the system it is intended to attenuate (in this case, the portion of the readhead assembly located within the protective housing, in particular the scale signal receiver 206). For example, in this case, the mass of the tuned mass damper 260 may be at least 1% of the mass of the scale signal receiver 206, optionally at least 2% of the mass of the scale signal receiver 206, such as approximately 5% of the mass of the scale signal receiver 206. For example, in this case, the mass of the tuned mass damper 260 may be configured such that it does not exceed 30% of the mass of the scale signal receiver 206, optionally does not exceed 25% of the mass of the scale signal receiver 206.

[0111] like Figure 4As shown, the tuned mass damper 260 is located inside the cylindrical hole provided by the scale signal receiver 206. Although not shown, in the particular embodiment described, the side of the cylindrical hole includes a plurality of elongated and axially extending ridges (or "splines") so that the outer periphery of the elastic ring 262 engages the ridges, thereby reducing the contact area between the elastic ring 262 and the interior of the hole. This helps to reduce the stiffness of the elastic ring 262, which in turn helps to reduce the natural frequency of the tuned mass damper 260. This configuration avoids the need to use a larger mass 264 or a softer elastic ring 262 to obtain the desired damping effect.

[0112] As will be appreciated, the cylindrical hole in which the resilient ring 262 and the tuned mass damper 260 are located can be shaped and sized so that the resilient ring 262 is squeezed / compressed within the hole. As will be appreciated, even in such a case, the mass element 264 will move / vibrate around independently of the scale signal receiver 206. Alternatively, the cylindrical hole in which the resilient ring 262 and the tuned mass damper 260 are located can be shaped and sized so that the resilient ring 262 is not squeezed / compressed within the hole. Accordingly, the cylindrical hole in which the resilient ring 262 and the tuned mass damper 260 are located can be shaped and sized so that the resilient ring 262 is free to rock / bounce around within the hole.

[0113] Figure 6a , Figure 6b , Figure 7a and Figure 7b A further alternative implementation of a suitable vibration control device is shown. Figure 6a and Figure 6b , the vibration control device comprises a mass element 364 connected to the housing 207 of the scale signal receiver 206 via a spring and damping element 362. In this case, the spring and damping element 362 is a block of elastomeric material such as rubber. The mass element 364 is thus able to vibrate independently of the scale signal receiver 206 by means of the flexibility of the spring and damping element 362 (which acts as a spring and damper by absorbing energy and converting it into heat).

[0114] Figure 7a and Figure 7b Another alternative embodiment is shown comprising a tuned mass damper 460. In this case, the tuned mass damper 460 comprises a mass 464 formed as an integral part of the housing 207 of the scale signal receiver 206 (e.g. via a single moulding). The tuned mass damper also comprises a spring element 466, which is also formed as an integral part of the housing 207 of the scale signal receiver 206. Figure 7bAs shown in the cross-sectional view of FIG. 2 , the material of the spring element 466 provided by the housing 207 is thin enough and flexible enough to enable the mass 464 to move and vibrate relative to the rest of the scale signal receiver 206. In this embodiment, a separate damping element 462 (such as Figure 7b ), the damping element comprises an elastic ring 462 which extends around a groove in the housing 207 due to the presence of an integrally formed spring element 466.

[0115] As will be understood, Figure 6b and Figure 7b Also shown is how the blades 216 may be hollow for passing wires (not shown) and / or air (as explained above). These figures also show how the mounting block 214 may include space for components such as at least one processor device 242 (as explained in more detail above).

[0116] like Figure 8a Schematically shown, the spring and damping portions of a tuned mass damper need not be provided by common portions. For example, an example tuned mass damper 560 may include a mass 562 and one or more (in this case four) springs 566 (which have little or no significant damping effect) and one or more (in this case four) damping elements 564.

[0117] In the above-described embodiments, the vibration control device comprises a tuned mass damper. However, as will be appreciated, this need not necessarily be the case. For example, the vibration control device may comprise a vibration damper 660, wherein Figure 8b An example of a vibration absorber is shown in . As schematically shown, the vibration absorber 660 may include a mass element 662 and one or more springs 666 (four springs 666 in this example) that enable the mass 662 to move / vibrate independently of the housing 207 and the rest of the scale signal receiving unit 206.

[0118] exist Figure 8a and Figure 8b In the depicted embodiment, the vibration controller 560, 660 is located in a recess provided in the housing 207 of the scale signal receiver 206, but as will be appreciated, other arrangements are possible. Figure 8c As shown, a vibration controller 770 (including a mass element 762 , a spring 766 and an optional damping element 764 ) may be connected to a side of the housing 207 of the scale signal receiving unit 206 .

[0119] In the above described embodiments, the encoder and scale are linear. However, as will be appreciated, the invention is equally applicable to non-linear encoders / scales, such as rotary encoders (eg discs) and / or ring encoders. Figure 9a , Figure 9b , Fig.10a and Fig.10b Exemplary implementations of these embodiments are schematically shown. Figure 9a In the embodiment of FIG. 8 , the scale 804 is disposed on the surface of the disk (shown in phantom) and is contained within a cylindrical protective housing 808. A circular seal 811 through which the blades 216 of the read head assembly can pass is disposed on the end face of the cylindrical protective housing 808 (although as will be appreciated, it may be disposed on the cylindrical side of the cylindrical protective housing 808 if desired). Figure 9b In the embodiments of the present invention, the scale 904 is disposed on the circumferential side of the ring (as shown in phantom) and is contained within a cylindrical protective housing 908. A circular seal 911 through which the blade 216 of the read head assembly can pass is disposed on the cylindrical side of the cylindrical protective housing 908 (although as will be appreciated, it can be disposed on the end face of the cylindrical protective housing 908 if desired). In these embodiments, the read head assembly (including the scale signal receiver 207, the mounting block 214 and the blade 216) can be the same as described above (although in Figure 9a In the embodiment of , it may be beneficial for the blades to bend to follow the curvature of the seal 811). In both embodiments, a light emitter 213 is provided on the mounting block 214, and the encoder is configured to control the light emitter to relay diagnostic information.

[0120] Fig.10a and Fig.10b An alternative embodiment of a sealed rotary encoder module 302 according to the present invention is shown. In this embodiment, the sealed rotary encoder module 302 includes (eg, a cross-sectional Fig.10b A scale 304 (best shown in FIG. 1 ) having a plurality of features (not shown) and a readhead including a scale signal receiver 306 for receiving signals from the scale 304.

[0121] The scale 304 and the scale signal receiver 306 are located inside the protective housing 308, which protects them from contaminants outside the protective housing. In this embodiment, the protective housing includes a first part 308a and a second part 308b. The scale signal receiver 306 is mounted to the first part 308a of the protective housing, and the scale 304 is mounted to the second part 308b of the protective housing. The first and second sealing lips 312 provide a seal between the first part 308a and the second part 308b, while allowing the first part 308a and the second part 308b of the protective housing to move relative to each other about the rotation axis A. Accordingly, for example, the second part 308b of the protective housing can be mounted (e.g., clamped) to a rotatable shaft (not shown) of a machine, and the first part 308a of the protective housing can be mounted (e.g., clamped) to a stationary part (not shown) of the machine.

[0122] As in the above-described embodiments, the scale signal receiver 306 includes a housing 307, in which the optical and electrical components of the scale signal receiver are housed and protected. In addition, as in the above-described embodiments, the encoder module 302 communicates with an external processor device (not shown) (e.g., a controller) via a communication channel, which in the described embodiment includes a physical connection (e.g., cable 305). Specifically, the position signal can be transmitted to the external processor device via a cable. In this embodiment, the scale signal receiver 306 includes a sensor and a processor for detecting and processing the scale signal to form position information. However, as will be appreciated, another portion of the encoder module 302 may include a sensor and / or a processor (e.g., a separate component located at other locations along the first portion 308a of the protective housing).

[0123] As with the above embodiments, the seal rotation module 302 includes a light emitter 313 for relaying diagnostic information to the operator / installer. Such a light emitter 313 may be controlled by a processor (e.g., the same processor used to process the detected scale signal) according to the methods described above in conjunction with other embodiments of the invention.

[0124] As with the above embodiments, the encoder module 302 comprises an optical absolute encoder, but this need not necessarily be the case.

[0125] In the embodiments described above in conjunction with Figures 1 to 9, the read head assembly includes a scale signal receiver 106, 206, a mounting block 114, 214, and a blade 116, 216. However, as will be appreciated, the read head assembly may include only a scale signal receiver. For example, the blade may be provided by a machine on which the scale signal receiver is to be mounted. For example, in conjunction with the embodiments described above, a sealed encoder module may be supplied without a mounting block and / or blade, but only with a scale signal receiver (or to be) located inside a protective housing. During setup, the scale signal receiver may be connected to a blade or equivalent provided by a machine on which the encoder device is to be mounted.

[0126] In the above embodiments, the encoder is a reflective optical encoder (e.g. the readhead detects the scale by light reflected from the scale, and the light source and detector(s) / sensor(s) of the readhead are located on the same side of the scale). As will be appreciated, the encoder may be a transmissive optical encoder (in which case the light source and detector(s) / sensor(s) of the readhead are on opposite sides of the scale). It will also be appreciated that the invention is applicable to non-optical encoders (e.g. magnetic encoders, inductive encoders and / or capacitive encoders).

[0127] As described above, the scale includes features for providing a signal detectable by a sensor of the readhead assembly. In the embodiments described above, the encoder / scale includes an absolute encoder / scale. The readhead decodes the acquired image to determine the absolute position. However, this need not necessarily be the case. For example, the encoder / scale may be an incremental encoder / scale (with or without reference marks). As is well known, the readhead may be configured to output a quadrature signal that may be used to determine the relative motion and / or position of the scale and the readhead. In this case, alternative techniques may be used to determine diagnostic information that may be used to determine how to control the light emitter 13, 113, 213. For example, an encoder module (e.g., a readhead) may be configured to determine whether the quadrature signal level is above or below a given threshold level to determine how to control the light emitter 13, 113, 213. Further details of this process are described in US 5241173, the contents of which are incorporated herein by reference.

[0128] The encoder may be diffraction based, for example, the signal detected by the sensor of the scale sensor assembly is formed by the scale (and one or more diffraction gratings in the scale sensor assembly) diffracting light (for example forming interference fringes at the sensor of the scale sensor assembly).

[0129] As will be appreciated, references to light in this application include electromagnetic radiation (EMR) in the ultraviolet to infrared range.

[0130] In the above-described embodiments of Figures 2 to 9, a vibration control device is used to reduce the vibration susceptibility of the scale signal receiver. However, as will be appreciated, the vibration control device is optional. For example, the embodiment of Figure 10 does not include a vibration control device. There may be a variety of reasons why a vibration control device may not be required. For example, depending on the vibration frequency to which the encoder will be exposed and the resonant frequency of the scale signal receiver, a vibration control device may not be required. Optionally, any vibration induced in the scale signal receiver may be small enough so as not to affect the structural stability of the scale signal receiver and / or not produce measurement errors within the desired tolerance. In addition, in those embodiments of the present invention where the encoder device is not arranged independently relative to the scale (for example, including an "integrated bearing"), a vibration control device may not be required because the scale signal receiver is biased against the scale. The following is combined with Figure 1a to Figure 1d This exemplary embodiment of the present invention is described.

[0131] The above-described embodiments of Figures 2 to 10 include a scale signal receiver that is arranged independently of the scale. However, as will be appreciated, the present invention is equally applicable to sealed encoder modules (e.g., including "integrated bearings") that do not arrange the scale signal receiver independently of the scale. Figure 1a to Figure 1d Such an embodiment of the present invention is described.

[0132] In the above embodiment, the scale signal receiver includes a housing that encapsulates the scale signal receiver components. However, this need not be the case. For example, electronic and / or other (e.g., optical) components may be exposed. For example, the PCB 240 may be exposed within the protective housing 108. Figure 1a to Figure 1d This exemplary embodiment of the present invention is described.

[0133] The above embodiments illustrate that the method of the sealed encoder device of the present invention configured to determine and output diagnostic information about a scale signal can be implemented in conjunction with a novel type of sealed encoder (specifically, wherein the scale signal receiver is arranged within a protective housing independently of the scale; in other words, it is "externally constrained"). However, as will be appreciated, the enclosed encoder device of the present invention configured to determine and output diagnostic information about a scale signal can also be used in conventionally configured sealed encoder devices, such as those encoder devices in which the readhead is constrained relative to the scale, which encoder devices can be described as "internally constrained" (e.g., such as the encoder described in US4595991).

[0134] Figure 1a to Figure 1d An example of an "internally confined", "integrated bearing" sealed encoder module 2 according to an aspect of the invention is schematically shown in Figure 1. As shown, the sealed encoder module 2 includes a scale 4 and a read head assembly, which includes a scale signal receiver 6. The scale 4 and the scale signal receiver 6 are located inside a protective housing 8, which protects them from contaminants outside the protective housing. The scale 4 is fixed to the protective housing 8, and the scale signal receiver 6 of the read head assembly can move along the length of the scale 4 within the protective housing 8. In use, the protective housing 8 will be fastened to a first part of the machine (not shown), and the read head assembly will be fastened to a second part of the machine, which second part can be moved along the x-axis relative to the first part. In practice, during use, the first part of the machine (and therefore the protective housing / scale) can be configured to move, and / or the second part of the machine (and therefore the read head) can be configured to move.

[0135] The readhead assembly comprises a mounting block 14 which is secured directly to the second part of the machine (e.g. via bolts passing through bolt holes 15 in the mounting block 14); a blade 16; and an articulated link 18 which connects the scale signal receiver 6 to the blade 16 (described in more detail below). An optical transmitter 13 is provided on the mounting block for relaying diagnostic information in the same manner as described in connection with the above embodiments.

[0136] The protective housing 8 further comprises a seal in the form of a pair of sealing lips 12 which seals the interior of the protective housing 8 where the scale 4 and scale signal receiver 6 are located from external contaminants. The blade 16 passes through the seal (between the pair of sealing lips 12) and the sealing lips 12 allow the blade 16 and therefore the scale signal receiver 6 to move along the length of the protective housing 8 / scale 4.

[0137] The position of the scale signal receiver 6 relative to the scale 4 in all degrees of freedom except along the length of the scale is strictly controlled by a bearing 20 (e.g. a roller bearing) in the scale signal receiver 6, which engages and abuts against the scale 4 (but as will be appreciated, it may additionally / alternatively abut against the interior of the protective housing). A spring (not shown) biases the bearing 20 of the scale signal receiver against the scale 4. Any misalignment in the axes of the first and second parts of the machine is accommodated by an articulated link 18. In this embodiment, the articulated link 18 is provided by a joint including at least one pivot point. The articulated link allows the scale signal receiver 6 to pitch, roll and yaw (i.e. rotational movement around three mutually perpendicular axes) relative to the mounting block 14 and allows the scale signal receiver 6 to move laterally relative to the mounting block 14 in a direction perpendicular to the measurement dimension (scale length). Accordingly, except along the measurement dimension (along the x-axis in the illustrated embodiment), the position and movement of the scale signal receiver 6 is constrained by the scale 4. In other words, the scale signal receiver 6 is guided by the scale 4. Thus, the articulated link 18 separates the scale signal receiver 6 and the mounting block 14 in all degrees of freedom except along the measuring dimension of the encoder device (which should coincide with the direction of movement of the first and second parts of the machine), which in the embodiment shown in Figure 1 is along the x-axis. As will be appreciated by those skilled in the art, for example, the manner in which a readhead is constrained relative to a scale is known.

[0138] Also like Figure 1b As shown, a power / communication cable 5 may be provided to enable the read head assembly to be powered and to facilitate communication between the read head assembly and an external processor device (e.g., a machine controller). In addition, an air supply line 9 may be provided for supplying air into the protective housing 8, thereby generating a positive pressure within the protective housing 8. Accordingly, in the event that the sealing lip 12 does not form a complete seal (particularly in the event that the lip seal is separated by the blade 16), the air will easily flow out of the protective housing 8 due to the positive pressure. Thus, the positive pressure provides further resistance to physical contamination attempting to enter the protective housing 8. As will be appreciated, such contamination may include solid contamination and / or fluid contamination, examples of which include chips, liquids (e.g., coolants) and / or moisture carried by the air. As also shown, another air supply line 7 may be provided, which supplies air into the protective housing via the read head assembly (e.g., via a conduit passing through the mounting block 14 and the blade 16).

[0139] In the described embodiments, light emitters 13, 113, 213, 313 are provided on the encoder module for relaying diagnostic information. In other embodiments, such light emitters are provided in addition or alternatively, and the encoder module can be configured to determine diagnostic information in the form of one or more electronic signals, for example via cables 105, 205, 305, and output it to an external device (e.g., a controller). For example, diagnostic information about the quality of the scale signal detected by the readhead can be determined and output by the encoder module. For example, an external device receiving the information can display the information to an operator. Such diagnostic information may be useful for helping an operator determine the status of the encoder module, for example, to determine whether the encoder module is operating normally, and if not (e.g., stopping the machine on which the encoder module is installed and / or replacing the encoder module), taking action.

[0140] In most of the above described embodiments, the light emitter 13, 113, 213 is provided on the read head. However, as will be appreciated, this need not necessarily be the case. Figure 1a , Figure 1b and Figure 1d As shown, the light emitter 13 may be disposed on a protective housing 8. In this case, the protective housing 8 may include an internal power source (e.g., a battery) for powering the light emitter and / or may be connected to an external power source. In addition, the protective housing 8 may be configured to receive diagnostic information from the read head to determine how to control the light emitter. Optionally, the protective housing 8 is configured to receive a scale signal detected by the read head and is configured to determine diagnostic information by itself in order to determine how to control the light emitter. In any case, the protective housing may include its own processor device, which is configured to determine how to control the light emitter (e.g., in response to the received diagnosis and / or thereafter determine the diagnostic information itself).

[0141] As will be appreciated, the placement of the light emitter on the protective housing is not Figure 1a to Figure 1d The present invention is not exclusive to the type of encoder device shown in the figure, but is equally applicable to the embodiments described above in conjunction with other figures. Figure 2a , Figure 2b , Figure 9a and Figure 9b As shown, the light emitter 113, 213 may be disposed on the protective housing 108, 808, 908 in addition to or in lieu of the readhead. Additionally, as described above, the embodiment of FIG. 10 includes the light emitter 313 on the protective housing 308.

[0142] It will also be appreciated that a bracket (eg, a "transport bracket") or the like may be used to maintain the read head assembly and protective housing in a predetermined physical relationship, (ie, such as when they are not mounted on a machine).

Claims

1. A sealed encoder module, the sealed encoder module being used to be mounted on a machine to measure a relative displacement of a first part and a second part of the machine, the sealed encoder module comprising: Ruler; A reading head, the reading head comprising a scale signal receiver; and a protective shell, the protective shell encapsulating at least the scale and the scale signal receiver, wherein the scale signal receiver comprises a shell, and one or more components of the read head are contained in the shell.

2. The sealed encoder module of claim 1, wherein: Electronic components of the scale signal receiver located inside the protective housing are contained within the housing and are thereby protected from contaminants that enter the protective housing of the sealed encoder module.

3. The sealed encoder module of claim 1, wherein: The scale signal receiver includes optical components for sensing the scale, the optical components being contained within the housing such that the optical components are protected from contaminants that enter the protective casing of the sealed encoder module.

4. The sealed encoder module of claim 3, wherein: The housing encapsulates all optical components of the scale signal receiver for detecting a scale signal, except for the outside of one or more windows, through which the scale signal enters the rigid housing and / or light from the light emitter leaves the rigid housing toward the scale.

5. The sealed encoder module according to claim 3 or 4, wherein: The optical component includes at least one of the following: a sensor, a transmitter, a lens, a diffraction grating, a beam steering device, a beam splitter, and a mirror.

6. A sealed encoder module as claimed in any preceding claim, wherein: The housing provides a void within which the one or more components are located.

7. A sealed encoder module as claimed in any preceding claim, wherein: The housing provides a structure to which the one or more components are mounted.

8. A sealed encoder module as claimed in any preceding claim, wherein: The housing comprises a rigid shell.

9. A sealed encoder module as claimed in any preceding claim, wherein: The housing encloses at least all electronic components of the scale signal receiver located within the protective casing, including any wires and any printed circuit boards.

10. A sealed encoder module as claimed in any preceding claim, wherein: The protective housing includes a seal, and the scale signal receiver can be connected to a portion outside the protective housing through the seal.

11. The sealed encoder module of claim 10, wherein: The read head comprises a blade-like member extending through a seal of the protective housing, and wherein the blade-like member comprises an internal passage for passing any wires between the interior and the exterior of the protective housing.

12. A sealed encoder module as claimed in any preceding claim, wherein: The encoder device comprises a reflective optical encoder device comprising a light source for illuminating the scale and a detector for detecting the scale, the detector being located on a same side of the scale, wherein the same housing comprises the light source and the detector.

13. A sealed encoder module as claimed in any preceding claim, wherein: The housing has an IP rating of at least IP44.

14. A sealed encoder module as claimed in any preceding claim, wherein: The housing has an IP rating of at least IP65.

15. A sealed encoder module as claimed in any preceding claim, wherein: The housing has an IP rating of at least IP67.

16. A sealed encoder module as claimed in any preceding claim, wherein: The housing is a rigid housing.

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