Ultrasonic Inspection Probes for Machine Tools

Abstract

The ultrasonic inspection probe includes a probe body and an elongated member having a datum surface for contacting an inspection object. The probe includes an ultrasonic transducer and an ultrasonic coupling assembly including a carrier shell including an ultrasonic coupling element having a transducer contact surface coupled to the ultrasonic transducer and an object contact surface for acoustically coupling to the inspection object. A bearing mechanism is configured to movably mount the ultrasonic transducer and ultrasonic coupling assembly to the elongated member, enable movement between an extended position in which the object contact surface of the ultrasonic coupling element extends beyond the datum surface and a measurement position in which the object contact surface of the ultrasonic coupling element is substantially flush with the datum surface, and guide the ultrasonic transducer along a linear axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to a surface normal of the datum surface.

Description

[Technical field]

[0001] The present invention relates to ultrasonic measurement equipment, and in particular to an improved ultrasonic inspection probe for use on machine tools. [Background technology]

[0002] Ultrasonic measuring devices for measuring industrial objects are known. Such devices range from simple handheld units that are manually pressed into contact with the object to be inspected by a user, to dedicated measuring systems that perform automatic measurements.

[0003] US Patent No. 5,399,633 describes a coordinate measuring machine (CMM) arranged to carry an ultrasonic test probe for measuring the thickness of an object. In one embodiment, the ultrasonic test probe is mounted via a gimbal that allows the ultrasonic test probe to align itself to the surface of the object being inspected. This self-alignment to the surface of the object allows the test probe to measure the wall thickness of the object along a line perpendicular to the surface, thereby maximizing the ultrasonic return signal. Acoustic coupling between the test probe and the object also requires the application of couplant gel, which may be applied manually or in an automated manner from a reservoir.

[0004] An alternative ultrasonic measurement device for use with a CMM, and in particular a robotic arm, is described in US Pat. No. 5,399,633. A spring-loaded ultrasonic transducer is carried by the robotic arm and pushed into engagement with the object to be measured. Deflection of the transducer elements is measured by a force or displacement sensor, providing a surface position measurement, whilst the ultrasonic transducer provides a simultaneous measurement of the object's wall thickness.

[0005] US Patent No. 5,399,633 describes an ultrasonic probe having a wireless transmitter for transmitting data collected by the probe. Thus, the wireless ultrasonic probe can be used not only in CMMs but also in computer numerically controlled (CNC) machining centers, where the lack of wired connections allows automatic exchange with tools or other measurement sensors.

[0006] US Pat. No. 5,399,433 describes a further wireless ultrasonic measurement probe for use with CNC machine tools. The device includes a tubular sleeve having an elastic carrier element protruding slightly from its distal end. The elastic carrier element is formed from an elastomer, such as Aqualene, which eliminates the need to apply an acoustic coupling liquid to the object being measured. The elastic carrier element is deformable such that when the device is pressed into engagement with a surface, the distal end of the elastic carrier element deforms and is displaced until it is flush with the end of the tubular sleeve. In a first embodiment, an annular gap is provided between the elastic carrier element and the inner surface of the tubular sleeve at the distal end of the tubular sleeve. This annular gap corresponds to the expansion of the elastic carrier element that occurs when the elastic carrier element is pressed into engagement with a surface, as shown in Figures 3 and 4 of US Pat. No. 5,399,433. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Publication No. 2009 / 0178482 [Patent Document 2] European Charter No. 2487455 [Patent Document 3] International Publication No. 2008 / 012535 [Patent Document 4] International Publication No. 2021 / 038106 Summary of the Invention [Problem to be solved by the invention]

[0008] The inventors have recognized that the above-mentioned devices have certain drawbacks when used in a machine tool environment. For example, the elastomer used as the carrier element in US Pat. No. 6,233,933 is likely to absorb the coolant typically used in CNC machine tools and thereby expand during use. The provision of an annular gap may also collect debris or coolant that may damage the elastomeric carrier element. Furthermore, surface contact forces are not precisely controlled and acoustic performance is compromised by the unconstrained outer surface of the elastomer. All of these effects reduce the performance of the device. [Means for solving the problem]

[0009] According to a first aspect of the present invention there is provided an ultrasonic inspection probe for a machine tool, the ultrasonic inspection probe comprising: A probe body; an elongate member extending from the probe body, the elongate member including a datum surface for contacting an object to be inspected; An ultrasonic transducer; an ultrasonic coupling assembly for acoustically coupling the ultrasonic transducer to the inspection object, the ultrasonic coupling assembly including a carrier shell including an ultrasonic coupling element, the ultrasonic coupling element including a transducer contact surface coupled to the ultrasonic transducer and an object contact surface for acoustically coupling to the inspection object; a bearing mechanism for movably mounting the ultrasonic transducer and the ultrasonic coupling assembly to the elongated member, the bearing mechanism enabling the ultrasonic transducer and the ultrasonic coupling assembly to move between an extended position in which the object contacting surface of the ultrasonic coupling element extends beyond the datum surface of the elongated member and a measurement position in which the object contacting surface of the ultrasonic coupling element is substantially flush with the datum surface of the elongated member; Including, The bearing mechanism is configured to guide the ultrasonic transducer along a linear axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to the surface normal of the datum surface.

[0010] Thus, an ultrasonic inspection probe, or ultrasonic probe for short, configured for use in a machine tool environment is provided. The ultrasonic probe comprises an elongated member protruding from a probe body. For example, a proximal end of the elongated member may be attached to the probe body. The elongated member may be permanently attached to the probe body, or may be integral with the probe body, or may form part of a stylus that is removably attachable to the probe body. The elongated member comprises a datum surface (i.e., a surface that functions as a reference or datum) configured to contact an object to be measured. In one embodiment, the datum surface may be provided at a distal end of the elongated tubular member. In such an example, the datum surface may include an annular surface or ring.

[0011] An ultrasonic transducer and an ultrasonic coupling assembly are also provided for generating and coupling ultrasonic waves to an object to be inspected. The ultrasonic coupling assembly, which may provide a so-called ultrasonic delay line, includes a carrier shell and an ultrasonic coupling element. The ultrasonic coupling element, or coupling element for short, is preferably formed from a material such as silicone rubber that is elastically deformable and is a good conductor of ultrasonic waves. As described below, the ultrasonic coupling element preferably includes a so-called dry or soft coupling material that allows ultrasonic coupling with the object without the need for an ultrasonic coupler gel or the like. The ultrasonic coupling element is at least partially contained within the carrier shell, and the object contacting surface of the ultrasonic coupling element extends from the carrier shell.

[0012] The ultrasonic transducer is acoustically coupled to the ultrasonic coupling assembly. In particular, the ultrasonic transducer is acoustically coupled to the ultrasonic coupling assembly by physical contact with the transducer contact surface of the ultrasonic coupling element. The physical contact may be direct or indirect (e.g., via an intermediate component such as an adhesive). The ultrasonic transducer may emit ultrasonic waves. The ultrasonic transducer may detect ultrasonic waves. The ultrasonic transducer may either emit or detect ultrasonic waves. Any suitable ultrasonic mode (e.g., transverse or longitudinal) may be generated and / or detected by the ultrasonic transducer. For example, the ultrasonic transducer may generate ultrasonic waves and detect returned ultrasonic waves to implement pulse-echo ultrasonic detection. Thus, the ultrasonic waves generated by the ultrasonic transducer may be coupled to the object to be inspected via the ultrasonic coupling assembly. The ultrasonic transducer and the ultrasonic coupling assembly together may enable measurements of thickness or defects of the object to be made, etc.

[0013] Also provided is a bearing mechanism for movably mounting the ultrasonic coupling assembly and the ultrasonic transducer to the elongated member. In one example, the ultrasonic coupling assembly and the ultrasonic transducer are slidably mounted within the elongated tubular member. The ultrasonic coupling assembly can be moved relative to the elongated member between a measurement (retracted) position and an extended position. In the extended (i.e., non-measurement) position, the object contacting surface of the ultrasonic coupling element extends beyond the datum surface of the elongated member. Thus, the object contacting surface may be the most distal portion of the ultrasonic probe when in the extended position. In the measurement position, the object contacting surface is disposed to be substantially flush with the datum surface of the elongated member. Thus, in the measurement position, the object contacting surface is retracted compared to the extended position. Of course, other positions of the ultrasonic coupling assembly can be adopted. For example, further retraction beyond the measurement position and / or further extension beyond the extended position may be possible.

[0014] The bearing mechanism is configured to guide the ultrasonic transducer along the longitudinal axis of the elongated member. In other words, the bearing mechanism controls the movement of the ultrasonic transducer such that it is constrained to move only back and forth along the longitudinal axis of the elongated member to which it is movably mounted. Thus, the constraint provided by the bearing mechanism allows translational movement of the ultrasonic transducer along the longitudinal axis of the elongated member (i.e., movement in a straight line). Furthermore, the bearing mechanism is configured to maintain the orientation of the ultrasonic transducer relative to the normal to the datum surface as the ultrasonic transducer is translated along the longitudinal axis. In other words, the rotation or tilt of the transducer is constrained as necessary to ensure that the ultrasonic transducer maintains a substantially unchanged orientation relative to the normal to the datum surface. Taking the longitudinal axis as the direction of movement, this can be considered as preventing pitch and yaw of the ultrasonic transducer. The roll of the ultrasonic transducer does not change the orientation of the ultrasonic transducer relative to the normal to the datum surface. However, it is also possible (but not required) to fully or at least partially constrain the roll of the ultrasonic transducer.

[0015] In use, the datum surface is engaged with the surface of the object to be inspected. This engagement physically (mechanically) aligns the datum surface with the surface of the object. For example, the plane of the datum surface may then be positioned parallel to the plane of the surface it is placed in contact with. As the ultrasonic transducer translates back and forth along the longitudinal axis of the elongated member, the orientation of the ultrasonic transducer does not change relative to the normal of the datum surface. This means that the orientation of the ultrasonic transducer always remains fixed relative to the surface normal of the contacted object. Fixing the orientation of the ultrasonic transducer relative to the surface normal of the object thus controls the direction in which the ultrasonic waves generated by the ultrasonic transducer are coupled to and / or received from the object. In particular, changes in the position of the ultrasonic transducer along the longitudinal axis (which may occur, for example, due to expansion of the ultrasonic coupling element, etc.) do not change the orientation of the ultrasonic transducer relative to the surface normal of the object. This allows the ultrasonic probe to be used to collect more reliable and consistent ultrasonic measurements.

[0016] As will be explained below, the ultrasound probe of the present invention has many advantages over the prior art devices mentioned in the introduction above.

[0017] The '661 patent describes an ultrasonic transducer in which the angular orientation of the ultrasonic transducer can be changed relative to the distal end of a sleeve that contacts the object being measured. Unlike the present invention, the ultrasonic transducer of the '661 device must include a rigid coupling element, such as Rexolite®, to ensure perpendicular alignment with the surface of the object. This takes advantage of the couplant gel required to establish acoustic contact with the object of the '661 device, which is simply not practical in a machine tool environment.

[0018] Unlike the arrangement of US Patent No. 5,999,633, the ultrasonic probe of the present invention has a measurement location that is positioned such that the object contact surface is substantially flush with the distal end of the elongate member. Thus, the arrangement of the present invention better defines the alignment of the ultrasonic transducer with respect to the surface of the object and also provides control and consistency over the force with which the ultrasonic coupling element engages the object, thereby improving measurement accuracy.

[0019] Furthermore, unlike the ultrasonic probe of U.S. Patent No. 5,993,636, the probe of the present invention allows a well-controlled compressive force to be applied to the ultrasonic coupling element even if the material used for the ultrasonic coupling element expands or swells (e.g., due to exposure to coolants or lubricants in the machine tool). The avoidance of an annular expansion gap as described in certain embodiments of U.S. Patent No. 5,993,636 also prevents the collection of debris that could otherwise damage the coupling element.

[0020] As mentioned above, the elongated member includes a so-called datum surface. A datum surface is a surface that functions as a physical reference or datum. As explained above, the normal to the datum surface has a fixed (unchanging) direction with respect to the longitudinal axis along which the ultrasonic transducer can translate. The datum surface may lie in a plane in which the normal direction of the surface is perpendicular to the plane. In one example, the elongated member may be tubular and the distal end of the elongated (tubular) member may provide the datum surface. For example, if the elongated member is tubular and has a circular cross section, the distal annular end surface of the elongated tubular member may provide a planar datum surface. The datum surface may include a single continuous datum surface (e.g., an annular ring or plate) or may be formed from multiple (non-continuous) spaced apart surface sections (e.g., multiple partial ring segments). Preferably, the longitudinal axis of the ultrasonic transducer's motion is substantially parallel to the surface normal of the datum surface. In other words, the longitudinal axis may be substantially perpendicular to the plane that contains the datum surface. In this manner, the longitudinal axis about which the ultrasonic transducer is translated is also substantially perpendicular to the surface of the object placed in contact with the datum surface. Although it is preferable to provide such a perpendicular alignment, other (e.g., known) orientations of the plane containing the datum surface and the longitudinal axis may be provided.

[0021] Advantageously, the ultrasonic transducer emits and / or receives ultrasonic waves along at least a first acoustic axis. The ultrasonic transducer may also emit and / or receive ultrasonic waves along one or more further acoustic axes. In the case of an emitted signal, the acoustic axis is the direction of maximum emitted signal strength. In the case of a received signal, the acoustic axis is the direction of maximum sensitivity to the input ultrasonic signal. Also, there may be different acoustic axes for different ultrasonic modes. For example, there may be different acoustic axes for longitudinal and transverse modes. Preferably, the first acoustic axis is the acoustic axis of the ultrasonic mode that the device is configured to use for measuring.

[0022] The position and / or orientation of the first acoustic axis may be known and / or fixed with respect to the longitudinal axis along which the ultrasonic transducer can move back and forth. In this way, the normal to the datum surface of the elongated member also has a fixed orientation with respect to the first acoustic axis. Advantageously, the first acoustic axis is configured to be substantially parallel to the longitudinal axis (i.e. the axis along which the ultrasonic transducer is guided). The longitudinal axis and the first acoustic axis may be offset laterally. Advantageously, the longitudinal axis and the first acoustic axis are substantially coincident. When the longitudinal axis is arranged to be substantially perpendicular to the plane containing the datum surface, the first acoustic axis may also be configured to be substantially perpendicular to the plane containing the datum surface. Thus, the first acoustic axis of the ultrasonic inspection probe may be configured to be substantially perpendicular to the datum surface. In this way, it may be ensured that ultrasonic waves are coupled into the surface of the object from a direction perpendicular to the surface of the object (i.e. because the acoustic axis is also substantially perpendicular to the surface of the object in contact). Directing sound at an object along the normal to its surface typically maximizes the returned signal and can also ensure that any measurement, e.g. the thickness of the object, corresponds to a known position within the object.

[0023] Advantageously, the first acoustic axis is aligned to the normal of the datum surface within 1°. More preferably, the first acoustic axis is aligned to the normal of the datum surface within 0.5°. Advantageously, the first acoustic axis is aligned to the normal of the datum surface within 0.2°. More preferably, the first acoustic axis is aligned to the normal of the datum surface within 0.1°. In one embodiment, the first acoustic axis may be aligned to the normal of the datum surface with a tolerance of about 0.08° or less. Thus, as discussed above, in one embodiment, these tolerances also define the tolerance within which the first acoustic axis is aligned relative to the surface normal of the object being inspected.

[0024] Advantageously, the ultrasonic probe also comprises a biasing mechanism for urging the ultrasonic coupling assembly towards the extended position. The biasing mechanism may include a compression spring or the like. The provision of such a biasing mechanism results in the extended position being adopted when no external force is applied, such as before contacting the ultrasonic probe with the object to be measured. Thus, the act of engaging the datum surface of the elongated tubular member with the object to be inspected causes the object to apply an external force to the object contacting surface of the ultrasonic coupling element by the object. This external force moves the ultrasonic coupling assembly to the measurement position relative to the elongated member against a biasing force provided by the biasing mechanism. The biasing mechanism also acts to urge the object contacting surface into physical engagement with the object to be inspected when in the measurement position. This biasing force ensures good acoustic coupling between the ultrasonic coupling element and the object. The strength of the applied biasing force can also be selected to ensure that such acoustic coupling is optimized and consistently applied during a series of measurements. Importantly, the compressive force applied to the ultrasonic coupling element can be set by the biasing mechanism and is not dependent on controlling the position of the ultrasonic probe relative to the inspection object. Additionally, the biasing mechanism can be configured such that the compressive force is largely independent of the size, and particularly the length, of the coupling element, for example by using springs with low spring rates and high preloads.

[0025] The biasing mechanism can directly or indirectly engage with the ultrasonic coupling assembly to provide the biasing force. Advantageously, the biasing mechanism applies a biasing force to the ultrasonic coupling assembly via the ultrasonic transducer. As described above, the object contact surface of the ultrasonic coupling element is configured to contact the object being measured while the transducer contact surface of the ultrasonic coupling element contacts the ultrasonic transducer. Thus, the biasing mechanism can bring the ultrasonic transducer into contact with the transducer contact surface of the ultrasonic coupling element, thereby engaging the object contact surface of the ultrasonic coupling element with the object. In other words, the biasing force applied to the ultrasonic coupling element by the biasing mechanism passes through the ultrasonic transducer. A biasing force of the same magnitude then brings the transducer into contact with the transducer contact surface and also brings the object contact surface into contact with the object.

[0026] As described above, in the absence of contact with the inspected object, the biasing mechanism urges the ultrasonic coupling assembly into an extended position. When the ultrasonic probe contacts the object, the biasing force is overcome and the ultrasonic coupling assembly is retracted. However, the datum surface of the elongated member limits the retraction (i.e., the measurement position is thus adapted), and then the biasing mechanism solely controls the magnitude of the force with which the ultrasonic transducer is pushed into engagement with the ultrasonic coupling element of the ultrasonic coupling assembly. Furthermore, by passing the biasing force through the transducer, the biasing mechanism also controls the overall magnitude of the compressive force applied to the ultrasonic coupling element. This configuration makes the measurement more repeatable, as it does not depend on precisely positioning the ultrasonic probe relative to the object to ensure that a constant force is applied to the inspected object and / or that the coupling element is exposed to a constant compressive force. In addition, the force applied by the biasing mechanism can be configured to be minimally dependent on the thickness of the coupling element. For example, the biasing mechanism can be equipped with a spring with a low spring rate and a high preload. Such an arrangement allows the coupling element to expand a significant amount in oil without affecting the applied compressive force.

[0027] The bearing mechanism guides the movement of the ultrasonic transducer and the ultrasonic coupling assembly. The bearing mechanism may include a single bearing arrangement for guiding a single module comprising both the ultrasonic transducer and the ultrasonic coupling element. The entire single module may then maintain a substantially invariant orientation relative to the surface normal of the datum surface when guided back and forth along the longitudinal axis of the elongated member. Alternatively, the bearing mechanism may guide the movement of the ultrasonic transducer, and the ultrasonic coupling assembly may be attached to the transducer and thereby also guided (indirectly) by the bearing mechanism. Conversely, the ultrasonic transducer may be indirectly guided when attached to the ultrasonic coupling assembly which is directly guided by the bearing mechanism.

[0028] Advantageously, the ultrasonic transducer and ultrasonic coupling assembly are mounted to the elongate member by separate portions of the bearing mechanism, which is advantageous because it allows relative (linear) movement of the ultrasonic transducer and ultrasonic coupling assembly and allows the compressive force applied to the ultrasonic coupling element to be controlled by a biasing force applied via the ultrasonic transducer.

[0029] Thus, the bearing mechanism may include a first bearing portion for guiding the movement of the ultrasonic transducer relative to the elongated member. This first bearing portion may guide the ultrasonic transducer along the longitudinal axis of the elongated member to ensure that the ultrasonic transducer maintains a substantially invariant orientation relative to the normal to the datum surface. The bearing mechanism may further comprise a second bearing portion for guiding the movement of the ultrasonic coupling assembly relative to the elongated member. The second bearing portion may guide the ultrasonic coupling assembly along the longitudinal axis of the elongated member to ensure that the ultrasonic coupling assembly maintains a substantially invariant orientation relative to the normal to the datum surface. However, the tolerance of guidance provided by the second bearing portion may be lower than that provided by the first bearing portion. In particular, it is less critical to maintain the angular orientation of the ultrasonic coupling assembly as it is guided back and forth along the longitudinal axis. Slight deviations of the ultrasonic coupling assembly away from a straight path and / or any angular changes (pitch, yaw or roll) in the orientation of the ultrasonic coupling assembly relative to the normal to the datum surface are unlikely to significantly affect the acoustic path between the transducer and the inspection object. In other words, the "play" of the second bearing part can be substantially higher than the play of the first bearing part without affecting the overall measurement performance.

[0030] The bearing mechanism of the ultrasonic probe may include any suitable bearing configuration or arrangement that provides the necessary control over the movement of the ultrasonic transducer and ultrasonic coupling assembly. In one embodiment, a slide bearing is provided that includes one or more bearing surfaces formed on each of the ultrasonic coupling assembly, the ultrasonic transducer, and the inner surface of the elongated member. Alternatively, a ball bearing slide may be provided.

[0031] Advantageously, the first bearing portion is provided by a molded outer surface of the ultrasonic transducer, which is in sliding contact with the inner surface of the elongated member. For example, the outer surface of a layer of adhesive (e.g., epoxy) that surrounds (e.g., encapsulates) the ultrasonic transducer may provide such a molded outer surface. Advantageously, the molded outer surface of the ultrasonic transducer fits (i.e., conforms to the contour of) the inner surface of the elongated member. Preferably, this is achieved by forming the molded outer surface in the elongated member (e.g., by curing the adhesive when the ultrasonic transducer is placed in the elongated member). In this way, the inner surface of the elongated member serves as a mould for the molded outer surface. The molded outer surface of the ultrasonic transducer thus accurately reproduces the shape of the inner surface of the elongated member, thereby providing a high-precision sliding bearing.

[0032] The second bearing portion may be provided by a protrusion (e.g., an O-ring) on ​​the outer surface of the carrier shell which is in sliding contact with the inner surface of the elongated member. Such a protrusion-based arrangement typically has more play than the molded arrangement described above, but has been found to provide adequate linear guidance of the ultrasonic coupling assembly.

[0033] The bearing mechanism (e.g., the first bearing portion) may be configured to allow the angular orientation of the ultrasonic transducer relative to the normal of the datum surface to be adjusted. It is noted that once adjusted, the angular orientation of the ultrasonic transducer should remain unchanged relative to the normal of the datum surface when translated back and forth along the longitudinal axis. As described above, ultrasonic energy from the ultrasonic transducer can be directed along a first acoustic axis having a particular orientation relative to the longitudinal axis along which the ultrasonic transducer is guided. The device may be arranged to allow the orientation of the first acoustic axis to be adjusted without adjusting the angular orientation of the ultrasonic transducer, as defined by the first bearing portion. For example, the ultrasonic transducer may include an internal adjustment mechanism for steering the direction of the first acoustic axis. This internal adjustment mechanism may be mechanical or electronic, allowing the angle of the first acoustic axis to be adjusted relative to the normal of the datum surface. In this manner, the angle at which ultrasonic waves are directed to the surface of the object being inspected can be adjusted.

[0034] Any adjustment of the orientation of the ultrasonic transducer or the first acoustic axis relative to the normal of the datum surface may only be possible during the initial manufacturing or configuration of the ultrasonic probe. In other words, the end user may not be able to make such adjustments. Alternatively, the orientation of the ultrasonic transducer or the first acoustic axis relative to the normal of the datum surface may be adjusted as needed. For example, such adjustments may be made during periodic calibration procedures to ensure that the ultrasonic waves are directed in a defined direction (e.g., vertical) of the surface of the object being inspected.

[0035] The elongated member protruding from the probe body may have any shape. Advantageously, the elongated member comprises an elongated tubular member. The elongated member may thus be provided in the form of a tube, preferably including a hollow internal cavity. The ultrasonic transducer and ultrasonic coupling assembly may then be movably mounted within the elongated tubular member. In other words, a bearing mechanism may mount the ultrasonic transducer and ultrasonic coupling assembly for movement within the hollow internal cavity of the tube. The longitudinal axis along which the ultrasonic transducer translates may correspond to the longitudinal axis of the elongated tubular member.

[0036] The elongated tubular member may have any suitable cross-sectional shape or profile. For example, it may have a square, rectangular, or elliptical cross-section. Advantageously, the elongated tubular member has a substantially circular cross-section. Preferably, at least a portion of the elongated tubular member is hollow. The ultrasonic transducer and / or ultrasonic coupling assembly may be at least partially housed within the hollow portion of the elongated tubular member. The cross-sectional shape of the ultrasonic coupling assembly and / or ultrasonic transducer is preferably the same as the cross-sectional shape of the hollow portion of the elongated tubular member. For example, the elongated tubular member, the ultrasonic coupling assembly, and / or the ultrasonic transducer may each have a substantially circular cross-sectional shape. As mentioned above, this allows a slide bearing arrangement to be provided to allow linear translation of the ultrasonic coupling assembly relative to the elongated tubular member.

[0037] The elongated tubular member may comprise a single piece or tube (i.e., provided as a single component). Alternatively, the elongated tubular member may be formed from multiple sections. The sections may be permanently attached (e.g., bonded) to one another. Alternatively, such sections may be removably attached to one another to allow for removal or replacement of sections as needed. The ability to disassemble the elongated tubular member may be advantageous for repair purposes.

[0038] The proximal end of the elongated member may be permanently attached to the probe body or may otherwise be integral with the probe body (i.e., the elongated member is not removable during normal use by a user). Alternatively, the proximal end of the elongated member may be releasably attachable to the probe body. For example, a threaded attachment may be used to attach the proximal end of the elongated member to the probe body. In such a removable configuration, the elongated member (e.g., elongated tubular member) and various components attached to and / or contained within the elongated member (e.g., ultrasonic coupling assembly, ultrasonic transducer, etc.) may together provide an ultrasonic stylus assembly that may be removably attached to the probe body.

[0039] Advantageously, the carrier shell of the ultrasonic coupling assembly comprises a substantially rigid material. Preferably, the substantially rigid material at least partially restrains the ultrasonic coupling element. For example, the carrier shell may be sufficiently rigid to prevent or inhibit the material forming the ultrasonic coupling element from expanding in a particular direction. Thus, there may be direct contact (i.e., no gap) between the carrier shell and the ultrasonic coupling element. The carrier shell may comprise an ultrasonic absorbing material. The carrier shell may be formed from a plastic material such as PTFE. The carrier shell may comprise a metal such as aluminum. Aluminum is advantageous because it is easy to machine and does not deform when a compressive force is applied to the ultrasonic coupling element it contains. The carrier shell may include internal serrations or ridges (e.g., to suppress ultrasonic reflections). The carrier shell and the ultrasonic coupling element may be formed as a single component. For example, the carrier shell may be formed by hardening an outer region of a material surrounding the ultrasonic coupling element. Alternatively, the ultrasonic coupling element may be inserted, cast, and / or bonded to a separate (separate) carrier shell.

[0040] The ultrasonic coupling assembly may have any suitable shape. As described above, the object contact surface and the transducer contact surface may be provided at opposite ends (e.g., the front and rear) of the ultrasonic coupling element. The transducer contact surface may be substantially parallel to the object contact surface.

[0041] The object contact surface and / or the transducer contact surface may be dome-shaped. All of the ultrasonic coupling elements may be disposed between the transducer contact surface and the object contact surface. The faces (ends) of the ultrasonic coupling elements may also protrude slightly from the carrier shell provided on the sides or around the sides of the ultrasonic coupling elements. The constraint provided by the carrier shell preferably prevents radial expansion of the ultrasonic coupling elements, but allows longitudinal movement of the ultrasonic coupling elements. In other words, a compressive force applied to the object contact surface and the transducer contact surface may distort the ultrasonic coupling elements without there being any radial expansion of that coupling element. For example, the dome-shaped surface may be flattened when the compressive force is applied. This configuration therefore allows for the application of high compressive forces, for example 10 N or more, to the object contact surface and the transducer contact surface without any radial expansion of the ultrasonic coupling elements occurring. Furthermore, the object contact surface may conform to the shape of the surface of the object, thereby improving acoustic coupling without affecting the acoustic alignment. This high contact force may therefore provide an ultrasonic signal with lower signal attenuation.

[0042] Preferably, the carrier shell is substantially tubular. Suitably, the carrier shell is substantially tubular and has a circular cross section. In such an example, the ultrasonic coupling element may be radially constrained by the tubular carrier shell. Thus, a cylindrical ultrasonic coupling assembly may be provided. The ultrasonic coupling element may be configured to not inhibit (i.e., to allow) axial (longitudinal) expansion of the ultrasonic coupling element. The acoustic axis of the ultrasonic transducer may be approximately coincident with the longitudinal axis of the carrier shell.

[0043] The ultrasonic coupling element may be formed from any material that allows ultrasonic waves to pass through. The ultrasonic coupling element preferably comprises an elastic ultrasonic coupling element. The ultrasonic coupling element preferably comprises an elastically deformable ultrasonic coupling element. The ultrasonic coupling element is preferably elastic (soft) enough to deform to the surface of the object. For example, the ultrasonic coupling element may include a material that forms a direct acoustic bond with a flat (Ra<0.8 μm) metal piece, such as aluminum, when exposed to an average pressure not exceeding 3 MPa. The material may also be elastic enough to reversibly deform up to a maximum of 1° misalignment of its surface. Preferably, the hardness of the ultrasonic coupling element is less than 100 Shore A. More preferably, the hardness of the ultrasonic coupling element is less than 90 Shore A. More preferably, the hardness of the ultrasonic coupling element is less than 50 Shore A. For example, the hardness of the ultrasonic coupling element may be about 30 Shore A. Advantageously, the material is highly deformable with an elongation at break of more than 50%. This is in contrast to hard ultrasonic coupling materials such as Rexolite®, which has a Shore A hardness of 100 (i.e., on the Shore A scale) and an elongation at break of 2-3%. Advantageously, the material forming the ultrasonic coupling element has an acoustic attenuation of less than 20 dB / mm at 5 MHz. More preferably, the material forming the ultrasonic coupling element has an acoustic attenuation of less than 10 dB / mm at 5 MHz. More preferably, the material forming the ultrasonic coupling element has an acoustic attenuation of less than 5 dB / mm at 5 MHz. More preferably, the material forming the ultrasonic coupling element has an acoustic attenuation of less than 2.5 dB / mm at 5 MHz. More preferably, the material forming the ultrasonic coupling element has an acoustic attenuation of less than 1 dB / mm at 5 MHz.

[0044] Advantageously, the ultrasonic coupling element comprises a dry elastic ultrasonic coupling element. A dry elastic ultrasonic coupling element may also be referred to as a soft elastic coupling element (as opposed to a hard coupling element). A dry ultrasonic coupling element, by definition, can be acoustically coupled to an object without requiring the use of a couplant liquid or gel. This differs from so-called wet (or hard) coupling elements, such as those formed from Rexolite, which require the application of such a couplant liquid or gel to provide acceptable acoustic coupling with the object.

[0045] The ultrasonic coupling element may be formed from any suitable material. The ultrasonic coupling element may include heat cured silicone rubber. Heat cured silicones, also known as high concentration rubber (HCR), are advantageous because they are relatively inexpensive to mold. Such HCRs can also be molded and bonded to the carrier shell in one operation, eliminating the need to glue the rubber to the housing or shell. An example of such an HCR is the Aquasilox material sold by Innovation Polymers of Kitchener, Ontario, Canada. Other silicones, such as liquid silicone rubber (LSR), may also be used. For example, the LSR material "Ultrasonic Drying Couplant" is manufactured by Sonemat Ltd, Warwik UK.

[0046] Advantageously, the elongated member is attached to the probe body via a movable joint. Such a movable joint allows the elongated member to reorient when a datum surface at its distal end contacts the surface of an object to be inspected. The movable joint may also allow linear (axial) displacement of the elongated tubular member relative to the probe body. This may help to absorb so-called over-travel, thus providing an over-deflection protection mechanism that prevents damage to the ultrasonic probe when it is moved into contact with a surface by a machine tool.

[0047] A deflection sensor may also be provided to sense deflection of the elongated member relative to the probe body. The deflection sensor may be provided to sense movement at the movable joint. The deflection sensor may be optical, capacitive, or electrical. The deflection sensor thus allows detection of deflection of the elongated tubular member relative to the probe body, thereby allowing a signal to be output by the probe indicating that contact has been made with an object. Such a signal may be used to stop movement of the ultrasonic probe relative to the object.

[0048] The ultrasonic inspection probe is configured for use with a machine tool. Machine tools, such as machining centers, milling machines, lathes, etc., typically have high rates of coolant and cutting debris discharged. Thus, machine tools, unlike measurement-only coordinate measuring machines or inspection robots, are typically used in clean environments, such as temperature-controlled inspection rooms. The ultrasonic probe is therefore resistant to contaminants present in the machine tool environment. Preferably, the ultrasonic probe is substantially sealed against ingress of cooling water or cutting debris. Advantageously, the ultrasonic inspection probe comprises an internal battery. This eliminates the need for trailing wires and allows the ultrasonic probe to be stored in a tool change carousel adjacent to the machine tool enclosure and automatically exchanged for cutting tools, etc., when in use.

[0049] Conveniently, the ultrasonic probe (e.g., the probe body) includes a wireless communication portion for wirelessly communicating acquired ultrasonic measurements to a remote probe interface. The wireless communication portion may transmit and / or receive measurements over an optical link. The wireless communication portion may transmit and / or receive measurements over a radio frequency (RF) link (e.g., a spread spectrum link such as a frequency hopping spread spectrum link). An apparatus may be provided that includes an ultrasonic probe and such a probe interface. The ultrasonic probe may be attachable or attached to a tool shank.

[0050] According to a second aspect of the present invention there is provided an ultrasonic inspection probe for a machine tool, the ultrasonic inspection probe comprising: A probe body; an elongate member extending from the probe body, the elongate member including a datum surface for contacting an object to be inspected; An ultrasonic transducer; an ultrasonic coupling element having a transducer contact surface coupled to the ultrasonic transducer and an object contact surface for acoustically coupling to the inspection object, the ultrasonic coupling element comprising an elastically deformable material; Including, The ultrasonic inspection probe comprises a bearing mechanism for movably mounting the ultrasonic transducer to the elongated member, the bearing mechanism being configured to guide the ultrasonic transducer back and forth along the longitudinal axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to the surface normal of the datum surface.

[0051] Thus, the ultrasonic inspection probe according to the second aspect of the present invention includes a bearing mechanism configured to provide linear motion (i.e., motion along the longitudinal axis) of the ultrasonic transducer relative to the elongated member. In this way, the ultrasonic transducer maintains a substantially invariant orientation relative to the surface normal of the datum surface as it translates back and forth. Such linear motion of the ultrasonic transducer may be used to accommodate translation of the ultrasonic coupling element within the elongated member and / or expansion or contraction of the ultrasonic coupling element (e.g., occurring when the datum surface contacts the object being inspected). This linear translation of the ultrasonic transducer has been found to be advantageous as it allows a predefined force to be applied to the ultrasonic coupling element via the ultrasonic transducer during a measurement. In other words, the compressive force applied to the ultrasonic coupling element during a measurement may remain invariant even as the ultrasonic coupling element expands (e.g., due to expansion as a result of exposure to a refrigerant) and / or moves relative to the datum surface. Applying a substantially invariant compressive force to the elastically deformable material of the ultrasonic coupling element also helps ensure consistency between ultrasonic measurements.

[0052] The ultrasonic coupling element may be attached directly to the elongated member. For example, the ultrasonic coupling element may be formed as a plug or block of material at least partially secured within the distal end of the elongated member. The object contacting surface of the ultrasonic coupling element may extend beyond the datum surface of the elongated member, and the ultrasonic coupling element may deform when pressed into contact with the object (i.e., until the datum surface contacts the object being inspected).

[0053] Alternatively, the ultrasonic coupling element may be provided as part of an ultrasonic coupling assembly. Such an ultrasonic coupling assembly may include a carrier shell that includes the ultrasonic coupling element. In such a configuration, a bearing mechanism may also be provided that allows the ultrasonic coupling assembly to move relative to the elongated member. In particular, the ultrasonic coupling assembly may be movable between an extended position, in which the object contacting surface of the ultrasonic coupling element extends beyond the datum surface of the elongated member, and a measurement position, in which the object contacting surface of the ultrasonic coupling element is substantially flush with the datum surface of the elongated member.

[0054] The ultrasound inspection probe according to the second aspect of the invention may also include any one or more of the features described in relation to the first aspect of the invention.

[0055] Also provided herein is an ultrasonic inspection stylus for attachment to a probe body, the stylus comprising an elongated member having a proximal end for attachment to the probe body, the elongated member including a datum surface for contacting an inspection object, an ultrasonic transducer, an ultrasonic coupling assembly for acoustically coupling the ultrasonic transducer to the inspection object, the ultrasonic coupling assembly including a carrier shell including an ultrasonic coupling element, the ultrasonic coupling element including a transducer contact surface coupled to the ultrasonic transducer and an object contact surface for acoustically coupling to the inspection object, and a carrier shell including an ultrasonic coupling element and an ultrasonic coupling element for acoustically coupling to the inspection object. and a bearing mechanism for movably mounting the ultrasonic coupling assembly to the elongated member, the bearing mechanism enabling the ultrasonic transducer and the ultrasonic coupling assembly to move between an extended position in which the object contacting surface of the ultrasonic coupling element extends beyond the datum surface of the elongated member and a measurement position that is substantially flush with the datum surface of the elongated member, the bearing mechanism being configured to guide the ultrasonic transducer along a longitudinal axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to the normal to the datum surface. The stylus may be attached or attachable to the probe body. The stylus may have any of the features described above.

[0056] An ultrasonic inspection probe is described herein. The ultrasonic inspection probe may be suitable for a machine tool. The ultrasonic inspection probe may include a probe body. The ultrasonic inspection probe may include an elongated member. The elongated member may extend from the probe body. The elongated member may include a datum surface. The datum surface may be for contacting an object to be inspected. The probe may include an ultrasonic transducer. The probe may include an ultrasonic coupling assembly. The ultrasonic coupling assembly may be for acoustically coupling the ultrasonic transducer to the inspection object. The ultrasonic coupling assembly may include a carrier shell. The carrier shell may include an ultrasonic coupling element. The ultrasonic coupling element may include a transducer contact surface. The transducer contact surface may be coupled to the ultrasonic transducer. The ultrasonic coupling element may include an object contact surface. The object contact surface may be for acoustically coupling to the object to be inspected. The probe may include a bearing mechanism. The bearing mechanism may movably mount the ultrasonic transducer and / or the ultrasonic coupling assembly to the elongated member. The bearing mechanism may enable the ultrasonic transducer and / or ultrasonic coupling assembly to move to an extended position. In the extended position, an object contacting surface of the ultrasonic coupling element may extend beyond a datum surface of the elongated member. The bearing mechanism may enable the ultrasonic transducer and / or ultrasonic coupling assembly to move to a measurement position. In the measurement position, an object contacting surface of the ultrasonic coupling element may be substantially flush with a datum surface of the elongated member. The bearing mechanism may be configured to guide the ultrasonic transducer along a longitudinal axis of the elongated member. This guidance provided by the bearing mechanism may be such that the ultrasonic transducer maintains a substantially invariant orientation relative to a normal to the datum surface. The probe may have any of the above features. [Brief description of the drawings]

[0057] [Figure 1] FIG. 1 shows an ultrasonic probe mounted on a spindle in a CNC machine tool. [Diagram 2] FIG. 2 illustrates the ultrasonic coupling assembly and transducer arrangement of the probe of FIG. [Diagram 3] FIG. 3 illustrates the ultrasonic coupling assembly and transducer of FIG. 2 mounted within an elongated tube prior to contact with an object. [Figure 4] 3 shows the ultrasonic coupling assembly and transducer of FIG. 2 mounted within an elongated tube and in contact with an object. [Diagram 5] FIG. 5 illustrates the movably mounting of the elongated tubular member to the probe body. [Figure 6] FIG. 6 shows an epoxy bearing used to mount an ultrasonic transducer to an elongated tube. [Figure 7a] FIG. 7a is a more detailed view of the ultrasound probe of the present invention. [Figure 7b] FIG. 7b is a more detailed view of the ultrasound probe of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] With reference to FIG. 1, a machine tool is shown. The machine tool comprises a housing 2 including a spindle 4 movable relative to a bed 3. The spindle 4 can be moved relative to the bed 3 under the control of a computer numerical controller (CNC) 6. To cut or process an object 8 placed on the machine tool bed 3, the spindle can carry a cutting tool (not shown). Measurement sensors can also be mounted on the spindle 4 instead of the cutting tool, allowing the object 8 to be measured before or after a cutting procedure. Typically, such measurement sensors and tools can be automatically loaded on the spindle 4 under the control of the CNC 6, allowing a desired cutting and measuring sequence to be implemented. In FIG. 1, an ultrasonic measurement probe 10 is shown mounted on the spindle 4. The measurement information is transmitted wirelessly (e.g. via an optical or radio link) to a probe interface 12 which transfers such measurements to the controller 6. As will be explained below, the ultrasonic measurement probe 10 allows to measure internal properties of the object 8, such as the thickness of the object.

[0059] 2, there is shown a schematic representation of the ultrasonic sensing device components of measurement probe 10. Ultrasonic coupling assembly 20 comprises a resilient ultrasonic coupling element 22 contained partially within an outer tubular carrier shell 24. Tubular carrier shell 24 is made from a substantially rigid material that prevents resilient coupling element 22 from expanding radially (i.e., resilient coupling element 22 is radially constrained by tubular carrier shell 24), but allows longitudinal expansion.

[0060] A proximal (rear) face 26 of the elastic coupling element 22 protrudes from the proximal end of the tubular carrier shell 24. An ultrasonic transducer 28 is biased (pushed) into contact with the proximal (rear) face 26 of the elastic coupling element 22 by a compression spring 30. A distal (front) face 32 of the elastic coupling element 22 protrudes from the distal end of the tubular carrier shell 24. This distal (front) face 32 of the elastic coupling element 22 is configured to be urged into contact with an object 34 to be measured.

[0061] 3, the ultrasonic coupling assembly 20, transducer 28, and compression spring 30 are shown diagrammatically as movably mounted within an elongated tubular member 40. A proximal end of the elongated tubular member 40 is attached to a probe housing (not shown), and a distal end 42 of the elongated tubular member 40 provides an annular datum (reference) surface 44. The transducer 28 and ultrasonic coupling assembly 20 are configured to move linearly (i.e., translate back and forth) within the elongated tubular member 40. As described in more detail below, the formation of an adhesive-based longitudinal bearing surface may provide control over such linear motion.

[0062] The ultrasonic coupling assembly 20, and in particular the transducer 28, are aligned during manufacture such that the acoustic axis 46 (i.e., the axis along which the ultrasonic waves are directed) is substantially perpendicular to a plane 47 that includes the annular datum surface 44. In other words, the acoustic axis 46 is aligned such that it is substantially parallel to a normal to the datum surface 44. This alignment may include, for example, adjusting the orientation of the transducer 28 relative to the elongated tubular member 40 on which the transducer 28 is carried. The acoustic axis 46 is also aligned with a longitudinal axis of translation of the ultrasonic coupling assembly 20 within the elongated tubular member 40. This ensures that when the annular datum surface 44 engages the surface of an object, the ultrasonic waves are directed to the object along a direction perpendicular to the surface. It is noted that adjustment of the orientation of the acoustic axis 46 relative to the normal to the datum surface 44 may be possible after manufacture. For example, this may allow adjustment of the acoustic axis 46 during a repair or recalibration procedure.

[0063] 3 shows the ultrasonic coupling assembly 20 biased by the compression spring 30 to its (fully) extended position (note that the mechanical stop defining this fully extended position is not shown). In this configuration, the distal (front) face 32 of the resilient coupling element 22 extends beyond the annular datum (reference) surface 44. This configuration is employed when the ultrasonic measurement probe 10 is not positioned to engage an object to be inspected (e.g., when it is in free space prior to measurement).

[0064] 4, the measurement probe shown in FIG. 3 is shown as being pushed into engagement with an object 50 to be measured. In this configuration, the annular datum surface 44 of the elongated tubular member 40 is brought into contact with the object 50. The action of bringing the annular ultrasonic coupling assembly 20 into contact with the surface of the object 50 pushes the ultrasonic coupling assembly 20 and the transducer 28 rearwardly into the elongated tubular member 40 until the distal (front) surface 32 of the elastic coupling element 22 is flush with the annular datum surface 44. In other words, the ultrasonic coupling assembly 20 adopts a stored (measurement) position in which the acoustic axis 46 is substantially perpendicular to the surface of the object 50. Thus, ultrasonic waves are coupled into the object 50 in a direction perpendicular to the surface normal.

[0065] The force with which the distal (front) face 32 of the elastic coupling element 22 is pressed against the surface is governed by the strength of the bias provided by the compression spring 30. Furthermore, since the ultrasonic transducer 28 is also pressed into contact with the proximal (rear) face 26 of the elastic coupling element 22 by the compression spring 30, the compressive force experienced by the elastic coupling element 22 is also controlled by the compression spring 30. This arrangement means that any expansion of the elastic coupling element 22, which must be a linear (non-radial) expansion due to the tubular carrier shell 24, does not substantially affect the compressive force applied to the elastic coupling element 22 during measurement (i.e., when in the retracted / measurement position). This enhances repeatability between measurements, even if the elastic coupling element 22 expands significantly due to absorption of refrigerant, etc.

[0066] Referring to FIG. 5, there is shown diagrammatically how the elongated tubular member 40 is movably mounted to a portion of the probe body, i.e., the illustrated housing portion 60. The housing portion 60 includes a movable joint 61 that allows the elongated tubular member 40 to move relative to the housing portion 60. This configuration allows the elongated tubular member 40 to tilt and also move (translate) toward the housing portion 60 (i.e., the proximal end of the elongated tubular member 40 can be retracted into and retracted from the housing portion 60). A bias is also provided to urge the elongated tubular member 40 to a rest position in which the elongated axis 70 of the housing portion 60 is aligned with the acoustic axis 46 (which in this example is aligned with the longitudinal axis of the elongated tubular member 40). Note that the deflected position is shown in FIG. 5, not the rest position.

[0067] In use, the distal end of the elongated tubular member 40 is moved into contact with the object 76 to be measured. The movable joint 61 provided between the housing portions 60 allows the elongated tubular member 40 to move so that the annular datum surface 44 sits flat on the surface of the object. This movement, which is greatly exaggerated in FIG. 5, ensures that the annular datum surface 44, and thus the acoustic axis 46 of the ultrasonic probe, is aligned normal to the surface of the object. In this particular example, this ensures that the acoustic axis 46 of the ultrasonic probe is perpendicular to the surface of the object 76 during measurement. The translational movement of the movable joint 61 also functions as an "overtravel" mechanism to take up any excess movement of the probe towards the object. Importantly, the movement provided by the movable joint 61 does not affect the force with which the elastic coupling element 22 is pushed to engage the surface of the object.

[0068] 6, it is illustrated how slide bearings can be implemented to guide the ultrasonic transducer 28 relative to the elongated tubular member 40. Components of the ultrasonic probe that correspond to similar components described with reference to 5 are assigned like reference numerals.

[0069] The ultrasonic transducer 28 is partially encapsulated in a layer of cured epoxy 90 that provides a bearing surface that slidably engages the inner surface 92 of the elongated tubular member 40. Thus, a sliding bearing is provided that guides the ultrasonic transducer 28 back and forth along the longitudinal axis. This sliding bearing arrangement ensures that the ultrasonic transducer 28 maintains a fixed orientation relative to the normal to the annular datum surface 44 even when translated back and forth. In other words, a bearing mechanism is provided to limit movement of the transducer element to maintain a fixed transducer orientation relative to the normal to the annular datum surface 44. In particular, at least pitch and yaw of the ultrasonic transducer 28 is substantially prevented.

[0070] The process for forming the sliding bearing shown in FIG. 6 includes the following steps. First, the (inner) bearing surface 92 of the elongated tubular member 40 is coated with a wax release agent. The ultrasonic transducer 28 is then held in the required position and orientation within the elongated tubular member 40. A two-part epoxy is injected into the space between the transducer 28 and the inner bearing surface of the elongated tubular member 40, and the epoxy is allowed to solidify. The transducer 28 and the fixed epoxy are slid out of the elongated tubular member 40, and the wax is removed from the (inner) bearing surface 92 of the elongated tubular member 40. The transducer 28 and attached (i.e., fixed or cured) epoxy 90 are then placed back onto the elongated tubular member 40 with appropriate lubrication to form a high-precision sliding (linear) bearing.

[0071] 7a and 7b, there is shown an ultrasonic inspection probe including a probe body 96 and an ultrasonic stylus 98. Figure 7b provides an enlarged view of the distal end of the inspection probe of Figure 7a.

[0072] The ultrasonic stylus 98 comprises an elongated tubular structure formed from a first section 100, a second section 102, and a third section 104. The first section 100 comprises a proximal end of the stylus and includes a threaded recess configured to attach the stylus 98 to a corresponding threaded protrusion of the probe body 96. The second section 102 comprises a hollow tube connecting the first section 100 to the third section 104. The three sections 100, 102, and 104 are releasably connected to one another to allow for easy disassembly, although, alternatively, they may be permanently joined to one another. It is also possible for the stylus to be formed as an integral (e.g., single piece) tubular structure. In other words, a modular or integral stylus may be provided.

[0073] An annular datum surface 106 provides a distal face of the third section 104 of the stylus. The ultrasonic coupling assembly 110 and ultrasonic transducer 112 are slidably mounted within the third section 104 of the stylus 98. A sliding (linear) bearing for the ultrasonic transducer 112 is provided by an epoxy layer 130 that slides against a corresponding inner surface 113 of the third section 104 of the stylus. The ultrasonic coupling assembly 110 includes an outer O-ring 132 that slides against a corresponding inner surface of the third section 104 of the stylus. As mentioned above, the ultrasonic coupling assembly 110 includes an ultrasonic coupling element 114, which in this example includes a high consistency rubber. The ultrasonic coupling element 114 is radially constrained within a carrier shell 115 and has a dome-shaped object-contacting (front) surface 116 that protrudes (extends) through an opening defined by the annular datum surface 106 (in the absence of external forces). The ultrasonic transducer 112 is biased by a spring 119 into contact with a transducer contacting (rear) surface 118 of the ultrasonic coupling element 114. During use, the annular datum surface 106 engages the surface of the object and the object contacting (front) surface 116 of the ultrasonic coupling assembly 110 is retracted so that it is flush with the annular datum surface 106. As described above, the spring 119 controls the force applied to the ultrasonic coupling element 114. A wire 120 passes from the ultrasonic transducer 112 through the stylus 98 and into the probe body.

[0074] The stylus 98 is removably attached to the probe body 96 via a threaded connection provided by a threaded recess and a corresponding threaded protrusion. The deflectable stylus carrier of the probe body 96 is attached to the remainder of the probe body by a movable joint providing a deflection mechanism. Deflection of the stylus carrier relative to the casing of the probe body 96 is measured by a suitable sensor. In this way, deflection of the stylus 98 due to contact with the surface of the object can be sensed and used by the machine tool to stop the movement of the ultrasonic probe. Any overtravel of the ultrasonic probe can also be absorbed by the deflection mechanism preventing damage to the stylus 98. The probe body 96 in this example also includes a processing unit including a processor for analyzing the ultrasonic signal and a wireless communication unit for transmitting the ultrasonic measurements to the associated probe interface. In this example, these are provided on one or more circuit boards located within the probe body 96.

[0075] It should be noted that the above are merely examples of the present invention. Those skilled in the art will appreciate the various different ways in which the present invention can be implemented.

Claims

1. 1. An ultrasonic inspection probe for a machine tool, the ultrasonic inspection probe comprising: A probe body; an elongated member extending from the probe body, the elongated member having a datum surface for contacting an object to be inspected; an ultrasonic transducer; an ultrasonic coupling assembly for acoustically coupling the ultrasonic transducer to the inspection object, the ultrasonic coupling assembly including a carrier shell including an ultrasonic coupling element, the ultrasonic coupling element including a transducer contact surface coupled to the ultrasonic transducer and an object contact surface for acoustically coupling to the inspection object; a bearing mechanism for movably mounting the ultrasonic transducer and the ultrasonic coupling assembly to the elongated member, the bearing mechanism enabling the ultrasonic transducer and the ultrasonic coupling assembly to move between an extended position in which the object contacting surface of the ultrasonic coupling element extends beyond the datum surface of the elongated member and a measurement position in which the object contacting surface of the ultrasonic coupling element is substantially flush with the datum surface of the elongated member; Including, an ultrasonic inspection probe, wherein the bearing mechanism is configured to guide the ultrasonic transducer along the longitudinal axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to the surface normal of the datum surface;

2. The ultrasonic inspection probe of claim 1 , wherein the longitudinal axis is substantially parallel to the surface normal of the datum surface.

3. The ultrasonic inspection probe of claim 1 , wherein the ultrasonic transducer is configured to emit ultrasonic waves along at least a first acoustic axis, the first acoustic axis being substantially parallel to the longitudinal axis.

4. The ultrasonic inspection probe of claim 1 , further comprising a biasing mechanism for urging the ultrasonic coupling assembly toward the extended position.

5. The ultrasonic inspection probe of claim 4 , wherein the biasing mechanism provides the bias to the ultrasonic coupling assembly via the ultrasonic transducer.

6. 10. The ultrasonic inspection probe of claim 1, wherein the bearing mechanism further comprises a first bearing portion for guiding the ultrasonic transducer relative to the elongated member, the first bearing portion being provided by a shaped outer surface of the ultrasonic transducer and in sliding contact with a surface of the elongated member.

7. The ultrasonic inspection probe of claim 6 , wherein the bearing mechanism comprises a second bearing portion for guiding the ultrasonic coupling assembly relative to the elongate member.

8. The ultrasonic inspection probe of claim 1 , wherein the elongated member comprises an elongated tubular member, and the ultrasonic transducer and the ultrasonic coupling assembly are movably disposed on the elongated tubular member.

9. The ultrasonic inspection probe of claim 8 , wherein the elongated tubular member has a substantially circular cross-section.

10. The ultrasonic inspection probe of claim 1 , wherein the carrier shell comprises a substantially rigid material that at least partially compresses the ultrasonic coupling element.

11. 10. The ultrasonic inspection probe of claim 1, wherein the carrier shell is substantially tubular and has a circular cross-sectional area, and the ultrasonic coupling element is radially compressed by the tubular carrier shell.

12. 10. The ultrasonic inspection probe of claim 1, wherein the ultrasound coupling element comprises a dry, resilient ultrasound coupling material that acoustically couples to an object without requiring the use of a couplant liquid or gel.

13. 10. The ultrasonic inspection probe of claim 1, wherein the elongated member is attached to a probe body via a movable joint, the ultrasonic inspection probe including a deflection sensor that senses deflection of the elongated member relative to the probe body.

14. 10. The ultrasonic inspection probe of claim 1, further comprising an internal battery and a wireless communication unit for wirelessly communicating acquired ultrasonic measurements to a remote probe interface, the ultrasonic probe being substantially sealed against ingress of cooling water or cutting debris.

15. 1. An ultrasonic inspection probe for a machine tool, the ultrasonic inspection probe comprising: A probe body; an elongated member extending from the probe body, the elongated member having a datum surface for contacting an object to be inspected; an ultrasonic transducer; an ultrasonic coupling element having a transducer contact surface coupled to the ultrasonic transducer and an object contact surface for acoustically coupling to the inspection object, the ultrasonic coupling element comprising an elastically deformable material; Including, The ultrasonic inspection probe includes a bearing mechanism for movably mounting the ultrasonic transducer to the elongated member, the bearing mechanism being configured to guide the ultrasonic transducer back and forth along the longitudinal axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to the surface normal of the datum surface.

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