Ultrasonic inspection probe and corresponding inspection method - Patents.com

Abstract

An ultrasonic inspection probe is described for use with a coordinate positioning apparatus, such as a machine tool. The probe includes a probe body for mounting to the coordinate positioning apparatus and an elongated member extending from the probe body. The elongated member includes an ultrasonic transducer assembly and a datum surface at its distal end. A movable joint () connects a proximal end of the elongated member to the probe body, the movable joint being configured to allow the proximal end of the elongated member to move both laterally and rotationally relative to the probe body, and the elongated member () can rotate about its distal end to angularly align the datum surface with the surface of the inspection object. In this manner, the datum surface is aligned with the surface of the inspection object and acoustic coupling is optimized.

Description

[Technical field]

[0001] The present invention relates to an ultrasonic inspection probe for use on a coordinate positioning apparatus such as a machine tool, etc. In particular, the present invention relates to an ultrasonic measurement probe having an improved moveable joint for aligning an ultrasonic transducer with the surface of an object being inspected. [Background technology]

[0002] Ultrasonic measurement devices are known that can be mounted on coordinate positioning apparatus such as machine tools or coordinate measuring machines (CMMs). Such devices enable automated ultrasonic measurements, for example to measure the thickness of an object or to identify defects in the object.

[0003] US Pat. No. 5,399,633 describes a coordinate measuring machine (CMM) arranged to carry an ultrasonic test probe for measuring the thickness of an object. As shown in FIG. 2 of US Pat. No. 5,399,633, the test probe is secured to an indexable probe head of the CMM by a connector. The test probe also includes a pair of gimbal mechanisms located near an ultrasonic (delay line) transducer. The gimbal mechanisms allow the angular alignment of the ultrasonic transducer to vary relative to the probe head, thereby self-aligning with the surface of the object being inspected. This self-alignment with 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. US Pat. No. 5,399,633 describes an ultrasonic measurement device having a spherical bearing that allows the face of the ultrasonic transducer element to self-align with the surface of the test object.

[0004] US Patent No. 5,399,633 describes an alternative arrangement in which an ultrasonic probe is attached to a CMM by a two-axis rotating head, which allows the angle of the ultrasonic probe relative to the object's surface to be fine-tuned in real time, thereby maximizing the ultrasonic return signal.

[0005] US Patent No. 5,399,633 describes a wireless ultrasonic measurement probe for use with CNC machine tools. In one embodiment, the device includes a tubular sleeve having an elastic carrier element that protrudes slightly from its distal end. 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. The tubular sleeve is also linearly movable relative to the base of the measurement probe (i.e., movable back and forth along the longitudinal axis of the tubular sleeve). A sensor is provided that detects such linear motion and thereby indicates when the distal end of the tubular sleeve is engaged with the object to be inspected.

[0006] A variety of other non-ultrasonic based measurement devices are also used for automated inspection of objects using coordinate positioning apparatus. For example, US Pat. No. 5,399,433, US Pat. No. 5,499,466, US Pat. No. 5,523,636 and US Pat. No. 5,523,663 describe touch-trigger probes that sense when a stylus contacts an object, allowing the position of a point on the surface of the object to be measured. The stylus is attached to the body of the touch-trigger probe by a spring-like moveable joint that only allows angular (tilting) movement of the proximal end of the stylus away from a repeatable rest position. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2009 / 0178482 [Patent Document 2] US Patent Application Publication No. 2013 / 0074601 [Patent Document 3] International Publication No. 2016 / 051147 [Patent Document 4] International Publication No. 2021 / 038106 [Patent Document 5] U.S. Patent No. 4,153,998 [Patent Document 6] U.S. Patent No. 5,146,691 [Patent Document 7] U.S. Patent No. 5,212,872 Summary of the Invention [Problem to be solved by the invention]

[0008] The inventors have recognized that the ultrasonic measurement devices described above have certain drawbacks. For example, they have found that the gimbal mechanism described in US Pat. No. 6,399,433 is very bulky and needs to be placed as close as possible to the distal end of the ultrasonic device to reduce the amount of lateral movement of the ultrasonic transducer across the surface of the object when self-aligning. The spherical bearing arrangement of US Pat. No. 6,399,433 is also relatively large and heavy. This can prevent measurement of certain objects where access to the surface is limited (e.g., in boreholes or on complex turbine blade arrangements). The two-axis rotating head of US Pat. No. 6,399,433 allows for precise alignment of the ultrasonic device, but is also bulky and unsuitable for use in machine tool applications where real-time position feedback is typically not possible. The linear (non-orbiting) motion of the tubular sleeve described in US Pat. No. 6,399,433 is more compact and prevents damage to the device when engaging a surface, but requires the device to be angularly aligned to the surface with very high precision. [Means for solving the problem]

[0009] According to a first aspect of the present invention there is provided an ultrasound inspection probe comprising: a probe body for mounting to a coordinate positioning apparatus; an elongate member extending from the probe body, the elongate member including an ultrasonic transducer assembly and a datum surface at a distal end thereof; a moveable joint connecting a proximal end of the elongate member to the probe body; Equipped with the movable joint is configured to permit lateral and rotational movement of the proximal end of the elongated member relative to the probe body such that the elongated member can rotate about its distal end to permit the datum surface to be angularly aligned with a surface of an object to be inspected; the movable joint includes a carrier member, a seat, and a biasing mechanism, the carrier member being provided at the proximal end of the elongated member, the probe body including the seat, and the biasing mechanism urging the carrier member into engagement with the seat in the absence of an applied external force, thereby defining a repeatable resting position of the elongated member relative to the probe body; The movable joint is configured such that an applied axial movement of the elongated member relative to the probe body causes the carrier member to at least partially disengage the seat, thereby enabling lateral movement of the proximal end of the elongated member relative to the probe body.

[0010] There is thus provided an ultrasonic inspection probe, or ultrasonic probe for short, configured for use with a coordinate positioning apparatus such as a machine tool, coordinate measuring machine, or industrial robot. The ultrasonic probe is attached or attachable to the coordinate positioning apparatus and comprises a probe body having an elongated member extending or projecting from the probe body. The elongated member comprises an ultrasonic transducer assembly, which is described in more detail below. Also, as described below, the elongated member or a portion of the elongated member may be permanently attached to the probe body via a moveable joint, or may be removably attached to the probe body.

[0011] The elongated member has a datum surface at its distal end (i.e., the datum surface is provided at the distal end of the elongated member). The distal end of the elongated member is the end of the elongated member furthest from the probe body. In one embodiment, the reference surface may be an annular surface or ring provided at the distal end of the elongated member having a tubular form. The datum surface functions as a physical reference or datum configured to contact the object to be measured. In particular, the datum surface provides a reference surface that mechanically aligns the elongated member with the surface of the object to be inspected. For example, the plane of the datum surface may be arranged parallel to the plane of the surface it is arranged to contact. As explained below, this allows the ultrasonic waves to be coupled to the object along a particular direction (e.g., along the surface normal of the object) to optimize the measurement. 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). In a preferred embodiment, the elongate member may be a tubular sleeve and a distal end of the elongate (tubular) member may provide the datum surface. For example, if the elongate member is tubular and has a circular cross-section, a distal annular end face of the elongate tubular member may provide a planar datum surface.

[0012] The elongated member is movably attached to the probe body via a movable joint. The movable joint thus allows the elongated member to move (deflect) relative to the probe body, thereby reducing the need to precisely align the entire ultrasound inspection probe with the object to provide acoustic contact. In particular, the movable joint connects the proximal end of the elongated member to the probe body. As described below, the movable joint may be provided within the probe body. In other words, the proximal end of the elongated member may be fully or partially disposed within the probe body, and the elongated member may then protrude from the probe body. It should also be noted that the probe body may have any suitable shape and may optionally be longer than the elongated member. For example, the probe body may include an elongated, substantially cylindrical casing or housing through which the elongated member extends. The probe body may also include an elongated protrusion having a movable joint disposed at its distal end. For example, the movable joint may be disposed at the distal end of an elongated stem or extension piece of the probe body.

[0013] The movable joint is configured to allow both lateral and rotational movement of the proximal end of the elongated member relative to the probe body. Lateral (side to side) movement permitted is movement of the proximal end of the elongated member in a direction transverse (orthogonal) to the longitudinal axis of the elongated member. Rotational movement permitted is angular (e.g., tilting or pivoting) movement of the proximal end of the elongated member relative to the probe body. The movable joint may also allow the elongated member to rotate about its own axis and / or may allow translational movement (i.e., moving back and forth) along the longitudinal axis of the elongated member.

[0014] Importantly, the lateral and rotational movement of the proximal end of the elongated member relative to the probe body permitted by the movable joint allows the datum surface to be angularly aligned with the surface of the object being inspected. In particular, the movable joint is configured such that the constraint imposed by the movable joint on the lateral and rotational movement of the proximal end of the elongated member is low enough to allow the elongated member to rotate (e.g., pivot) about its distal end. In other words, releasing the lateral constraint of the elongated member at the movable joint allows it to rotate about a point at or near the distal end of the elongated member. Such rotation about the distal end of the elongated member (i.e., where the datum surface is located) results in no significant lateral movement of that distal end during reorientation of the elongated member, thereby preventing the datum surface from having to move (laterally) along the surface of the object as it is being reoriented to align with that surface. In this manner, surface damage (e.g., scratches that may result when moving a datum surface across a surface) is reduced or eliminated. Furthermore, ultrasonic measurements can be made at desired points on the surface of the object to ensure perfect engagement and alignment of the datum surface with the surface of the object, even if the elongated member must be reoriented.

[0015] The movable joint comprises a carrier member provided at the proximal end of the elongated member. In one embodiment, the carrier member can be removably attached to the remainder of the elongated member. For example, the carrier member can be provided as a stylus holder forming part of the movable joint, and the remainder of the elongated member can be provided as an ultrasonic stylus (e.g., an elongated tubular sleeve including an ultrasonic transducer assembly) that can be removably attached to the stylus holder. The movable joint also comprises a seat. In particular, the probe body comprises the seat. For example, the seat can be formed on or within the probe body. The seat can be in a fixed position relative to the remainder of the probe body. The carrier member and the seat are configured to adopt a repeatable rest position when they engage with each other. The movable joint also comprises a biasing mechanism, such as a spring, that engages the carrier member with the seat in the absence of an applied external force, thereby defining a repeatable rest position of the elongated member relative to the probe body. The biasing mechanism thus exerts a spring or biasing force (returned to the probe body) on the carrier member that urges (e.g., pushes or pulls) the carrier member into engagement with the seat. In this way, the elongate member adopts the same (repeatable) rest or reference position relative to the probe body when it does not move away from its rest position due to external forces (e.g., due to deflection resulting from contact with an object).

[0016] The movable joint is also configured such that an imparted axial movement of the elongated member relative to the probe body (i.e., movement of the elongated member relative to the probe body along the direction of the longitudinal axis of the elongated member) causes the carrier member to at least partially disengage the seat. Such axial movement may be in addition to or caused by an angular movement (rotation) of the elongated member. This allows for lateral movement of the proximal end of the elongated member relative to the probe body. In other words, an imparted axial movement (including a movement having an axial component) partially or completely disengages or unseats the carrier member from the seat. This in turn allows for lateral movement of the proximal end of the elongated member. In this way, the elongated member maintains a well-defined rest position relative to the probe body until the movable joint is disengaged by an imparted axial movement of the elongated member relative to the probe body. Such axial displacement of the elongated member relative to the probe body may also be used to help absorb so-called overtravel, thus providing an over-deflection protection mechanism that prevents damage to the ultrasonic probe when it is moved into contact with a surface.

[0017] It can thus be seen that the ultrasonic inspection probe of the present invention has various advantages over the prior art devices described above. For example, the present invention eliminates the need to place a bulky gimbal mechanism or spherical ball joint near the distal end of the elongated member, as described in U.S. Pat. No. 5,399,433 and U.S. Pat. No. 5,499,623, respectively. The present invention is also advantageous over U.S. Pat. No. 5,499,433 because there is no need to lubricate the spherical bearing to reduce friction, nor to route electrical signals through the spherical bearing. In accordance with U.S. Pat. No. 5,499,433, the need to use a two-axis rotating head to align the ultrasonic probe has also been eliminated. Similarly, the tight angular alignment tolerances required when using the linear slide mechanism of U.S. Pat. No. 5,499,433 are avoided.

[0018] In a preferred embodiment, the carrier member and the seat are configured to provide a kinematically defined rest position. In other words, each of the six degrees of freedom of movement of the carrier member relative to the seat is constrained. The absence of excessive constraints ensures that the same rest position is reached with a high level of repeatability. The carrier member may advantageously include three radially extending rollers, and the seat includes three pairs of balls, each pair of balls defining a gap for receiving one of the rollers. Such an arrangement of balls and rollers has been found to provide a kinematic joint with high precision. Any axial movement of the carrier member (which may result from a rotation or pivoting of the carrier member) disengages (or lifts off) one or more rollers from their gaps, thereby allowing lateral movement of the carrier member relative to the seat. It is also possible that the seat of the probe body includes three radially extending rollers, and the carrier member includes three pairs of balls for receiving the rollers.

[0019] As mentioned above, a biasing mechanism is provided to engage the carrier member with the seat. Thus, a rest (neutral) position defined by the carrier member and the seat is provided in the absence of applied external forces. Any suitable biasing mechanism may be used. For example, the biasing mechanism may include one or more springs. Advantageously, the biasing mechanism comprises a compression spring. Such a spring may be returned to the probe body. The compression spring may be a coil spring.

[0020] The probe body may also include a guide channel in which the compression spring is at least partially housed or accommodated. The guide channel may be coaxial with the compression spring when the elongated stylus is in a rest (neutral) position. The guide channel may be dimensioned (e.g., it may have an inner diameter slightly larger than the outer diameter of the compression spring) to prevent or inhibit lateral movement of a portion or portions of the compression spring when the elongated member is deflected from its rest or neutral position. For example, the guide channel may be configured to prevent at least a portion of the compression spring from buckling or moving laterally when there is lateral movement at the movable joint. In a preferred embodiment, the guide channel is provided to accommodate a proximal section of the compression spring (i.e., the section of the compression spring that is attached to the probe body and is furthest from the movable joint). Thus, the guide channel helps ensure that the compression spring does not buckle or bend in a manner that applies unpredictable or undesirable forces to the elongated member when the elongated member is deflected relative to the probe body (e.g., acting to stop the distal end of the elongated member from aligning with the object being inspected).

[0021] Conveniently, the biasing mechanism engages with the probe body and / or carrier member via a conical member (e.g. a member having a conical or partially conical tip). The tip of the conical member may engage with an engagement mechanism such as a plate, cup or recess. The conical member may be provided as part of the biasing mechanism and the engagement mechanism may be provided as part of the carrier member or the probe body, or vice versa. In a preferred embodiment, the biasing mechanism comprises a compression spring, and the conical member is provided (e.g. attached) to a distal end of the compression spring. The carrier member may then comprise an engagement mechanism such as a plate or cup, and the tip of the conical member is pressed by the compression spring, thereby biasing the carrier member into the seat. This arrangement reduces Hertzian stresses. Alternatively or additionally, the conical member may be provided at a proximal end of such a compression spring. The probe body may then comprise an engagement mechanism against which the conical member is pressed. The use of such a configuration (i.e., one or more conical members pressed into contact with one or more engagement features) allows for a linear (axial) biasing force to be applied to the carrier member without imparting or inhibiting rotational or pivotal motion of the carrier member. In this way, the compression spring itself does not constrain or cause pivotal or angular motion of the carrier member.

[0022] Advantageously, the conical member and the engagement feature are formed from materials having different hardness. Advantageously, the hardness of the material providing the engagement feature is higher than the hardness of the conical member. For example, the engagement feature may comprise a tool steel. Such a tool steel may have a hardness of about 60 RHC (Rockwell Hardness C). The conical member may comprise a hardened steel. Such a hardened steel may have a hardness of about 40 RHC. This difference in hardness reduces mechanical wear.

[0023] Preferably, the movable joint allows for at least 0.5 mm of lateral movement of the proximal end of the elongated member. More preferably, the movable joint allows for at least 0.75 mm of lateral movement of the proximal end of the elongated member. More preferably, the movable joint allows for at least 0.5 mm of lateral movement of the proximal end of the elongated member. More preferably, the movable joint allows for at least 1.5 mm of lateral movement at the proximal end of the elongated member. The amount of rotation that can occur at the distal end of the elongated member depends on the amount of lateral movement of the proximal end of the elongated member and the length of the elongated member. Preferably, the permitted lateral movement of the proximal end of the elongated member allows the distal end of the elongated member to rotate (i.e., tilt) at least 0.25°. More preferably, at least 0.4° of rotation (i.e., tilt) is provided. More preferably, at least 0.5° of rotation is provided. More preferably, at least 0.6° of rotation is provided. Advantageously, the elongate member is at least 2cm in length, more preferably at least 5cm in length, more preferably at least 10cm in length.

[0024] The elongated member projecting from the probe body may have any suitable shape. Advantageously, the elongated member comprises an elongated tubular member. For example, the elongated member may be provided in the form of a tube or tubular sleeve. The elongated member may be substantially straight. Alternatively, the elongated member may not be straight. For example, the elongated member may include an angled joint, a twist, a curved portion, or a dog-leg connection. At least a portion of the elongated member may be hollow or may include a hollow internal cavity. The elongated member may have any suitable cross-sectional shape, such as a square, rectangular, or elliptical cross-section. Advantageously, the elongated member has a substantially circular cross-section. The elongated member may comprise a single section or tube (i.e., may be provided as a single component). Alternatively, the elongated member may be formed from multiple sections (e.g., multiple tubular 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 sections to be removed or replaced as required. The ability to disassemble the elongate tubular member can be advantageous for maintenance or repair purposes.

[0025] The elongated member comprises an ultrasonic transducer assembly used to measure the object being inspected. The ultrasonic transducer assembly may be at least partially mounted or housed within a cavity defined by the elongated member. The ultrasonic transducer assembly preferably comprises an ultrasonic transducer. The ultrasonic transducer may emit ultrasonic waves. The ultrasonic transducer may detect ultrasonic waves. The ultrasonic transducer may both emit and 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.

[0026] The ultrasonic transducer assembly may also include an ultrasonic coupling element. The ultrasonic coupling element may be provided as part of the ultrasonic coupling assembly. In other words, the ultrasonic transducer assembly may include an ultrasonic coupling assembly including an ultrasonic transducer and an ultrasonic coupling element. The ultrasonic coupling assembly may also be referred to as an ultrasonic delay line.

[0027] The ultrasonic coupling element, or coupling element for short, may be made of any material that is a sufficiently good conductor of ultrasonic waves. 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.

[0028] The ultrasonic coupling element may be formed from any suitable ultrasonic transmission material. Conveniently, the ultrasonic coupling element includes so-called dry or soft coupling materials that allow ultrasonic coupling with the object without the need for the use of ultrasonic couplant gel or the like. In other words, the ultrasonic coupling element may include an elastic (i.e. elastically deformable) ultrasonic coupling element. The ultrasonic coupling element is preferably sufficiently elastic (soft) to deform to the surface of the object. For example, the ultrasonic coupling element may include a material that forms a direct acoustic coupling with a flat (Ra<0.8 μm) piece of metal, such as aluminum, when exposed to an average pressure not exceeding 3 MPa. The material may also be sufficiently elastic 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 to break of over 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 to break of 2-3%.

[0029] The elastically deformable ultrasonic coupling element may comprise a 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 Dry Couplant" is manufactured by Sonemat Ltd, Warwik UK.

[0030] The ultrasonic transducer assembly may include an ultrasonic transducer acoustically coupled to the ultrasonic coupling element described above. In particular, the ultrasonic transducer is conveniently positioned to be in physical and acoustic contact with the transducer contact surface of the ultrasonic coupling element. Such physical contact may be direct or indirect (e.g., via an intermediate component such as an adhesive). Thus, ultrasonic waves generated by the ultrasonic transducer may be coupled to the object to be inspected via the ultrasonic coupling element. The ultrasonic transducer and the ultrasonic coupling element together may enable measurements such as of thickness or defects of the object to be made.

[0031] In one embodiment, an ultrasonic coupling assembly may be provided that includes a carrier shell and an ultrasonic coupling element. The ultrasonic coupling element may be at least partially contained within the carrier shell. An object contacting surface of the ultrasonic coupling element may extend from the carrier shell. Advantageously, the carrier shell of such an ultrasonic coupling assembly includes a substantially rigid material. Preferably, the substantially rigid material at least partially constrains 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.

[0032] The carrier shell may include an ultrasonic absorbing material. The carrier shell may be formed from a plastic material such as PTFE. The carrier shell may include 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.

[0033] 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.

[0034] Advantageously, the ultrasonic coupling element may have an object contact surface and a transducer contact surface provided at opposite ends (e.g., front and rear) of the ultrasonic coupling element. The transducer contact surface may be substantially parallel to the object contact surface. The object contact surface and / or the transducer contact surface may be dome-shaped. All of the material of the ultrasonic coupling element may be located between the transducer contact surface and the object contact surface. The faces (ends) of the ultrasonic coupling element may also protrude slightly from a carrier shell provided at or around the sides of the ultrasonic coupling element. The constraint provided by the carrier shell preferably prevents radial expansion of the ultrasonic coupling element but allows longitudinal movement (expansion or deflection) of the ultrasonic coupling element. In other words, a compressive force applied between the object contact surface and the transducer contact surface may distort the ultrasonic coupling element without there being any radial expansion of that coupling element. For example, a dome-shaped surface may be flattened when a compressive force is applied. This configuration therefore allows for the application of high compressive forces, e.g., 10 N or more, to the object contact surface and the transducer contact surface without any radial expansion of the ultrasonic coupling element. Furthermore, the object contact surface can conform to the shape of the object's surface, thereby improving acoustic coupling without affecting acoustic alignment. This high contact force can therefore provide an ultrasonic signal with lower signal attenuation.

[0035] In a preferred embodiment, the elongated member comprises a tubular sleeve that houses the ultrasonic transducer assembly. In such a configuration, the distal end of the tubular sleeve may provide a datum surface. In other words, the datum surface may be provided by a face or other feature of the elongated member. The elastically deformable ultrasonic coupling element may then move and / or deform sufficiently upon contact with the object to allow the datum surface to engage and align with the object. In this way, deformation or movement of the elastically deformable ultrasonic coupling element means that it does not affect the alignment of the elongated member with the surface of the object being measured.

[0036] Advantageously, the ultrasonic transducer assembly is movably mounted to the elongated member. In particular, the ultrasonic probe may include a bearing mechanism that movably mounts the ultrasonic transducer assembly (e.g., ultrasonic coupling assembly and ultrasonic transducer) to the elongated member. For example, the ultrasonic coupling assembly and ultrasonic transducer may be slidably mounted within the elongated member.

[0037] The bearing mechanism may be advantageously provided so as to be configured to guide the ultrasonic transducer along the linear axis of the elongated member. In other words, the bearing mechanism may control the movement of the ultrasonic transducer such that it is constrained to move only back and forth along the linear axis of the elongated member to which it is movably mounted. The constraint provided by such a bearing mechanism thus preferably allows translational movement of the ultrasonic transducer along the linear 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 when the ultrasonic transducer is translated along the longitudinal axis. In other words, the rotation or tilt of the transducer may be constrained as necessary by the bearing mechanism to ensure that the ultrasonic transducer maintains a substantially unchanged orientation relative to the normal to the datum surface. Taking the linear axis as the direction of movement, this can be considered as preventing pitch and yaw of the ultrasonic transducer. 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.

[0038] 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 a plane that includes the datum surface. In this way, the longitudinal axis about which the ultrasonic transducer translates is also substantially perpendicular to the surface of the object that is 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 that includes the datum surface and the longitudinal axis may be provided.

[0039] The bearing mechanism may guide the movement of all or a portion of the ultrasonic transducer assembly. For example, the bearing mechanism may guide the movement of the ultrasonic transducer and / or the ultrasonic coupling assembly. The bearing mechanism may include a single bearing arrangement for guiding a single ultrasonic transducer assembly module that includes both the ultrasonic transducer and the ultrasonic coupling element. The bearing mechanism may be configured to maintain a substantially invariant orientation relative to the surface normal of the datum surface when the entire single module is 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 ultrasonic 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 that is directly guided by the bearing mechanism.

[0040] The ultrasonic transducer and the ultrasonic coupling assembly may be attached to the elongated member by separate parts of the bearing mechanism. This is advantageous because it allows relative (linear) movement of the ultrasonic transducer and the 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. Thus, the bearing mechanism may include a first bearing part for guiding the movement of the ultrasonic transducer relative to the elongated member. This first bearing part guides the ultrasonic transducer along the linear axis of the elongated member, thus ensuring that the ultrasonic transducer maintains a substantially invariant orientation relative to the normal of the datum surface. The bearing mechanism may further comprise a second bearing part for guiding the movement of the ultrasonic coupling assembly relative to the elongated member. The second bearing part may guide the ultrasonic coupling assembly along the linear axis of the elongated member, thus ensuring that the ultrasonic coupling assembly maintains a substantially invariant orientation relative to the normal of the datum surface. However, the tolerance of guidance provided by the second bearing part may be lower than that provided by the first bearing part. In particular, it is not 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 that of the first bearing part without affecting the overall measurement performance.

[0041] The bearing mechanism may be implemented in a variety of ways. In particular, the ultrasonic probe may include any suitable bearing configuration or arrangements that provide the necessary control over the movement of the ultrasonic transducer and / or 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.

[0042] In a preferred embodiment, the bearing mechanism comprises a first bearing portion provided by a molded outer surface of the ultrasonic transducer in sliding contact with the inner surface of the elongated member. For example, the outer surface of a layer of adhesive (e.g., epoxy) surrounding (e.g., encapsulating) 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 disposed within the elongated member). In this way, the inner surface of the elongated member serves as a mold for the molded outer surface. Thus, the molded outer surface of the ultrasonic transducer accurately reproduces the shape of the inner surface of the elongated member, thereby providing a high-precision sliding bearing. The bearing mechanism may also include a second bearing portion comprising a protrusion (e.g., an O-ring) provided on the outer surface of the carrier shell in sliding contact with the inner surface of the elongated member. Such a protrusion-based arrangement typically has more play relative to the first bearing portion than the molded arrangement described above, but has been found to provide suitable linear guidance of the ultrasonic coupling assembly.

[0043] As mentioned above, the bearing mechanism can guide components of the ultrasonic transducer assembly, such as the ultrasonic transducer, along the longitudinal axis of the elongated member. The ultrasonic transducer forming part of the transducer assembly can emit (direct) or receive (collect) ultrasonic energy along an acoustic axis having a specific orientation with respect to the longitudinal axis mechanically defined by the bearing mechanism. 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.

[0044] 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 tatum plane of the elongated member may also have 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 along which the ultrasonic transducer is guided. The linear axis and the first acoustic axis may be offset laterally. Advantageously, the linear axis and the first acoustic axis are substantially coincident. When the linear 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 can 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 ultrasound at an object along the normal to its surface typically maximizes the return signal and can ensure that any measurement, such as the thickness of the object, corresponds to a known location within the object.

[0045] 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. These tolerances may therefore also define the tolerance within which the first acoustic axis is aligned relative to the surface normal of the object being inspected.

[0046] The ultrasonic probe may be arranged to allow the orientation of the first acoustic axis to be adjusted relative to the linear (mechanical) axis of motion of the ultrasonic transducer. 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 motion of the mechanical axis, i.e., relative to the normal of the datum surface. In this way, the angle at which the ultrasonic waves are directed to the surface of the object to be inspected can be adjusted.

[0047] If the bearing mechanism is provided (e.g., including the first and second bearing portions described above), it may be configured to allow mechanical adjustment of the angular orientation of the ultrasonic transducer relative to the normal of the datum surface. It should be noted that once adjusted, the angular orientation of the ultrasonic transducer preferably remains unchanged relative to the normal of the datum surface when translated back and forth along a linear axis. This mechanical adjustment of the bearing mechanism may be in lieu of, or in addition to, any adjustment of the angle of the first acoustic axis relative to the mechanical axis of motion. 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 manufacture 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.

[0048] In a preferred embodiment, the ultrasonic probe comprises a transducer assembly comprising an ultrasonic transducer and an ultrasonic coupling assembly, each movably mounted on an elongated member. The ultrasonic probe is conveniently configured such that 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. The object contacting surface may therefore be the most distal part of the ultrasonic probe when in the extended position. In the measurement position, the object contacting surface is arranged to be substantially flush with the reference surface of the elongated member. In the measurement position, the object contacting surface is therefore retracted compared to the extended position. Of course, other positions of the ultrasonic coupling assembly may be adopted. For example, further retraction beyond the measurement position and / or further extension beyond the extended position may be possible.

[0049] The ultrasonic probe may further comprise a second biasing mechanism for urging the ultrasonic coupling assembly towards the above-mentioned extended position. It should be noted then that the above-mentioned biasing mechanism provided separately as part of the movable joint may be referred to as the first biasing mechanism. The second biasing mechanism may include a compression spring or the like. The second biasing mechanism may directly or indirectly engage with the ultrasonic coupling assembly to provide the bias. Advantageously, the second biasing mechanism applies a bias to the ultrasonic coupling assembly via the ultrasonic transducer. For example, 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 is in contact with the ultrasonic transducer. Thus, the second biasing mechanism may 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 second biasing mechanism passes through the ultrasonic transducer. A biasing force of the same magnitude then urges the transducer into contact with the transducer contact surface and also urges the object contact surface into contact with the object.

[0050] The provision of such a second 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 contact 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 the biasing force provided by the biasing mechanism. Thus, the act of contacting the ultrasonic probe with the object overcomes the biasing force and retracts the ultrasonic coupling assembly. However, the datum surface of the elongated member limits the amount of retraction of the ultrasonic coupling assembly. Thus, it is only the second biasing mechanism that controls the amount of force applied to the ultrasonic coupling element via the ultrasonic transducer after the datum surface engages the inspection object.

[0051] The above-described configuration makes the measurements more repeatable since it does not depend on precise positioning of the ultrasonic probe relative to the object to ensure that a constant force is applied to the object under test and / or that the coupling element is exposed to a constant compressive force. In addition, the force applied by the second biasing mechanism can be configured to be minimally dependent on the thickness of the coupling element. For example, the biasing mechanism can comprise a spring with a low spring rate and a high preload. Such an arrangement allows the coupling element to expand a significant amount in the oil without affecting the applied compressive force.

[0052] In a preferred embodiment, the elongated member may therefore include a tubular sleeve and the ultrasonic transducer assembly may be mounted within the tubular sleeve by a bearing mechanism configured to guide the ultrasonic transducer assembly back and forth along the longitudinal axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to a surface normal of the datum surface.

[0053] In alternative embodiments, the face of the coupling element can function as a position reference or datum surface used to align the elongated member to the surface of the object being inspected. For example, an ultrasonic transducer assembly may include an ultrasonic transducer and a constrained or rigid coupling element for acoustically coupling the ultrasonic transducer to the inspection object. If a rigid coupling element or delay line (e.g., formed from Rexolite) is provided, this may require the use of a couplant gel to obtain adequate acoustic coupling with the object. In such a configuration, the distal end of the coupling element may provide the datum surface of the elongated member (i.e., no separate datum surface is provided).

[0054] Advantageously, the ultrasonic probe further comprises a deflection sensor that senses deflection of the elongated member relative to the probe body. The deflection sensor may generate a trigger signal output by the ultrasonic probe when deflection of the elongated member relative to the probe body is detected to indicate that contact with the object has been made. The deflection sensor may simply sense whether the elongated member is deflected relative to the probe body without measuring the magnitude or direction of such deflection. Alternatively, the deflection sensor may measure (transduce) the magnitude and optionally the direction of any deflection of the elongated member relative to the probe body. The deflection sensor may be provided in the movable joint. The movable joint may incorporate the deflection sensor. The deflection sensor may be optical, capacitive, or electrical. For example, the kinematically defined movable joint described above that uses balls and rollers to define a rest position may include an electrical circuit through the balls and rollers. Deflection can then be sensed by monitoring when the electrical circuit is broken by the rollers moving away from a pair of supporting balls. The signal (e.g., a trigger signal) generated by the deflection sensor may be advantageously used to stop the movement of the ultrasonic probe relative to the object. The signal generated by the deflection sensor may be used to measure the position of a point on the surface of the object. This allows the ultrasonic probe to be moved to a defined position relative to the surface of the inspection object before stopping to collect ultrasonic measurements. Optionally, one or more probe positioning movements (e.g., toward and / or away from the object) may be performed after receiving the signal from the deflection sensor but before the collection of ultrasonic measurements.

[0055] As outlined above, ultrasonic inspection probes can be used with any coordinate positioning apparatus. Advantageously, ultrasonic inspection probes are configured for use with machine tools. Machine tools such as machining centres, milling machines, lathes, etc. typically have high rates of coolant and cutting debris discharged. Thus, unlike measurement-only coordinate measuring machines or inspection robots, machine tools are typically used in clean environments such as temperature-controlled inspection rooms. Thus, ultrasonic probes for machine tools require protection from contaminants present in the machine tool environment. Preferably, the ultrasonic probe is substantially sealed against ingress of cooling water or cutting debris. Advantageously, ultrasonic inspection probes include 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. 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 via an optical link. The wireless communication portion may transmit and / or receive measurements via a wireless 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 the tool shank.

[0056] According to a second aspect of the present invention there is provided a method for ultrasonic inspection of an object comprising the steps of bringing an ultrasonic inspection probe according to the first aspect of the present invention into acoustic contact with an object to be inspected using a machine tool and coupling ultrasonic waves into the object. The method may include measuring a thickness of the object and / or detecting defects in the object.

[0057] As mentioned above, the ultrasonic inspection probe may include a deflection sensor that senses deflection of the elongated member relative to the probe body. For such ultrasonic inspection probes, the method may include the step of (i) sensing physical contact of the elongated member with a surface of the object to be inspected using the deflection sensor. In other words, such ultrasonic inspection probes may also detect when the elongated member is in contact with the surface of the object (i.e., using the deflection sensor). In a preferred embodiment, the ultrasonic inspection probe may issue a trigger signal when contact of the elongated member with the surface is detected.

[0058] The method may also include (ii) using the physical contact detected in step (i) to initiate an ultrasonic measurement of the object using the ultrasonic inspection probe. For example, the ultrasonic measurement of step (ii) may be initiated after the deflection sensor issues a trigger signal indicating that surface contact has been made. A controller of an associated machine tool that moves the ultrasonic inspection probe relative to the object may receive the trigger signal. Upon receiving the trigger signal, the machine tool controller may direct the ultrasonic inspection probe to collect one or more ultrasonic measurements.

[0059] Physical contact of the elongated member with the surface of the object (i.e., as measured by the deflection sensor) may be used to measure the position of a point on the surface of the object. For example, the relative position of the probe and object may be measured upon receipt of a trigger signal from the probe. Sensing such physical contact may also be used to stop motion of the ultrasonic inspection probe relative to the object to allow ultrasonic measurements to be collected. In one embodiment, the machine tool may simply stop motion and initiate ultrasonic measurements upon receiving a trigger signal from the ultrasonic inspection probe. The elongated member, in this example, has aligned itself relative to the surface of the object, i.e., disengagement of the carrier member from the seat allows the elongated member to align itself relative to the surface of the object when surface contact is made.

[0060] Alternatively, the machine tool may reposition the ultrasonic inspection probe after surface contact is detected (e.g., after the position of the point on the surface of the object is measured). In other words, the machine tool may be programmed to move the ultrasonic inspection probe towards and / or away from the object between steps (i) and (ii) to establish acoustic contact for ultrasonic measurement of the object. In particular, the ultrasonic inspection probe may be moved to an optimal position for collecting acoustic measurements. This optimal position may include providing acoustic contact with the object while the carrier member remains engaged with the seat such that the elongated member remains in a repeatable rest position. For example, this step may include moving (backing) the machine tool such that the ultrasonic inspection probe loses contact with the surface (i.e., the carrier member and the seat engage and the elongated member adopts a repeatable rest position). A step of moving the ultrasonic inspection probe into contact with the surface to enable ultrasonic measurement may then be performed, but with a force low enough to ensure that the carrier member remains engaged with the seat. This is advantageous for curved or uneven object surfaces where the orientation of the elongated member may be uncertain, allowing the elongated member to align itself to the surface.

[0061] Also described herein is an ultrasonic inspection probe comprising a probe body for mounting to a coordinate positioning device, an elongated member extending from the probe body, the elongated member including an ultrasonic transducer assembly and a surface (e.g., a datum surface) at a distal end thereof, and a movable joint connecting a proximal end of the elongated member to the probe body, the movable joint being configured to enable lateral and rotational movement of the proximal end of the elongated member relative to the probe body such that the elongated member can rotate about its distal end to enable the surface (e.g., the datum surface) to be angularly aligned with a surface of an object to be inspected.

[0062] The ultrasonic inspection probes described herein may comprise an integral elongated member. Alternatively, the ultrasonic inspection probe may include a holder for the elongated member (i.e., allowing the elongated member to be releasably attached to the holder). In other words, the ultrasonic inspection probe may comprise a probe body for attachment to a coordinate positioning device, a holder for attachment to the elongated member, and a movable joint connecting the holder to the probe body, the movable joint being configured to allow lateral and rotational movement of the holder relative to the probe body such that the elongated member attached to the holder can rotate about its distal end to allow a surface (e.g., a datum surface) of the elongated member to be angularly aligned with a surface of the object to be inspected. The elongated member preferably comprises an ultrasonic transducer assembly. The elongated member preferably comprises a surface (e.g., a datum surface) at its distal end for contacting the object to be measured. A kit may be provided that includes the ultrasonic inspection probe and one or more elongated members attachable to the holder. The kit may include multiple elongated members. The multiple elongate members may include different elongate members (e.g., having different lengths, transducers, coupling elements, etc.) One or more extension bars may be provided that can be disposed between the elongate members and the holder to increase the separation between the distal ends of the elongate members and the probe body.

[0063] Advantageously, the movable joint comprises a carrier member. The carrier member may be provided at a proximal end of the elongated member. In an embodiment, the carrier member may be removably attached to the remainder of the elongated member. For example, the carrier member may be provided as a stylus holder forming part of the movable joint, and the remainder of the elongated member may be provided as an ultrasonic stylus (e.g. an elongated tubular sleeve including an ultrasonic transducer assembly) that may be removably attached to the stylus holder. Advantageously, the movable joint comprises a seat. The probe body may include the seat. For example, the seat may be formed on or within the probe body. The seat may be in a fixed position relative to the remainder of the probe body. The carrier member and the seat may be configured to adopt a repeatable rest position when they engage with each other. The movable joint may also include a biasing mechanism, such as a spring. The biasing mechanism preferably urges the carrier member to engage with the seat in the absence of an applied external force, thereby defining a repeatable rest position of the elongated member relative to the probe body. Thus, the biasing mechanism may apply a spring or biasing force (returned to the probe body) to the carrier member that urges (e.g., pushes or pulls) the carrier member into engagement with the seat. In this way, the elongate member adopts the same (repeatable) rest or reference position relative to the probe body when it does not move away from its rest position due to external forces (e.g., due to deflection resulting from contact with an object).

[0064] Advantageously, the movable joint is configured such that an imparted axial movement of the elongated member relative to the probe body (i.e., movement of the elongated member relative to the probe body along the direction of the longitudinal axis of the elongated member) causes the carrier member to at least partially disengage the seat. Such axial movement may be in addition to or caused by an angular movement (rotation) of the elongated member. This allows for a lateral movement of the proximal end of the elongated member relative to the probe body. In other words, an imparted axial movement (including a movement having an axial component) partially or completely disengages or unseats the carrier member from the seat. This in turn allows for a lateral movement of the proximal end of the elongated member. In this way, the elongated member maintains a well-defined rest position relative to the probe body until the movable joint is disengaged by an imparted axial movement of the elongated member relative to the probe body. Such an axial displacement of the elongated member relative to the probe body may also be used to help absorb so-called overtravel, thus providing an over-deflection protection mechanism that prevents damage to the ultrasonic probe when it is moved into contact with a surface.

[0065] Also provided herein is a method for ultrasonic inspection of an object, the method comprising the steps of bringing an ultrasonic inspection probe as described above into acoustic contact with the object to be inspected and coupling ultrasonic waves into the object.

[0066] An inspection probe is therefore described herein. The inspection probe may include an ultrasonic inspection probe. The probe may include a probe body. The probe body may be adapted for mounting to a coordinate positioning apparatus. A member, for example an elongated member, may extend from the probe body. The elongated member may include a measurement transducer. The member may include a measurement transducer assembly. The measurement transducer may include an ultrasonic transducer. The measurement transducer may include an alternative (non-ultrasonic) sensor. The member may have a datum (reference) surface. The datum surface may be provided at a distal end of the member. A movable joint may be provided connecting the elongated member to the probe body. For example, a proximal end of the elongated member may be connected to the probe body by a movable joint. The movable joint may be configured to enable lateral movement of the proximal end of the elongated member relative to the probe body. The movable joint is configured to enable rotational movement of the proximal end of the elongated member relative to the probe body. The movement permitted by the movable joint may be such that the elongate member can rotate about its distal end to allow the reference surface to be angularly aligned with the surface of the object to be inspected. The inspection probe may include any one or more of the features described above. [Brief description of the drawings]

[0067] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows an ultrasonic probe mounted on a spindle in a CNC machine tool. [Figure 2a] FIG. 2a shows a moveable joint for an ultrasound probe that allows lateral movement of the proximal end of the elongate member. [Figure 2b] FIG. 2b shows a moveable joint for an ultrasound probe that allows lateral movement of the proximal end of the elongate member. [Figure 2c] FIG. 2c shows a moveable joint for an ultrasound probe that allows lateral movement of the proximal end of the elongate member. [Figure 3a]FIG. 3a illustrates movement of the distal end of the elongate member with and without lateral movement at the diarthrodial joint. [Figure 3b] FIG. 3b illustrates movement of the distal end of the elongate member with and without lateral movement at the diarthrodial joint. [Figure 4] FIG. 4 shows an elongated member having a rigid delay line that provides a datum surface. [Diagram 5] FIG. 5 shows an elongate member having a reference surface formed by the distal end of a tubular member. [Figure 6] FIG. 6 illustrates an elongate member having a datum surface formed by the distal end of a tubular member and a linearly translatable ultrasonic transducer assembly. [Figure 7a] FIG. 7a shows in more detail the probe body attached to the elongate member by a kinematic moveable joint. [Figure 7b] FIG. 7b shows in more detail the probe body attached to the elongate member by a kinematic moveable joint. [Figure 7c] FIG. 7c shows in more detail the probe body attached to the elongate member by a kinematic moveable joint. [Figure 7d] FIG. 7d shows in more detail the probe body attached to the elongate member by a kinematic moveable joint. [Figure 7e] FIG. 7e shows in more detail the probe body attached to the elongate member by a kinematic moveable joint. [Figure 8] FIG. 8 illustrates an elongated member linearly translatable transducer assembly configuration. [Figure 9a] FIG. 9a provides a more detailed view of the linearly translatable transducer assembly. [Figure 9b] FIG. 9b provides a more detailed view of the linearly translatable transducer assembly. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0068] 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 inspection probe 10 is shown mounted on the spindle 4. Measurement information is transmitted wirelessly (e.g. via an optical or radio link) to a probe interface 12 that 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.

[0069] Although a machine tool is illustrated in FIG. 1, the ultrasonic inspection probe of the present invention may also be configured for use with other coordinate positioning devices such as coordinate measuring machines (CMMs), industrial inspection robots, and the like.

[0070] 2a-2c, an ultrasonic inspection probe 10 (or ultrasonic probe 10 for short) is shown generally. The ultrasonic probe 10 comprises a probe body 12 which may be secured to a machine tool spindle 4 by known mechanical mounting mechanisms. An elongated member 14 extends from the probe body 12. A proximal end of the elongated member 14 is attached to the probe body 12 by a moveable joint 16. A distal end or tip of the elongated member 14 comprises a datum surface 18. An ultrasonic transducer assembly is also provided within the elongated member 14. Details of the ultrasonic transducer assembly are not shown in FIGS. 2a-2c, but will be described in more detail below.

[0071] To collect ultrasonic measurements, the ultrasonic probe 10 is moved along its longitudinal axis toward and into engagement with the surface of the object 20 being measured (i.e., downward as shown in Figures 2a-2c). In this example, it is desired to measure the thickness of the object 20 below a point on the surface indicated by arrow 22.

[0072] As shown in Figure 2a, the ultrasonic probe 10 is first moved through free space towards the object 20. The elongated member 14 is biased by the movable joint 16 to a repeatable rest position relative to the probe body 12 in the absence of any external forces.

[0073] FIG. 2b shows the elongated member 14 initially contacting the object 20 which is at a slight angle relative to the ultrasonic probe 10 (note that the tilt angle etc. is exaggerated in the drawing to aid in understanding). As shown in FIG. 2b, the datum surface 18 is therefore initially tilted at an oblique angle relative to the surface of the object 20 which prevents good acoustic contact from being established. However, movement of the ultrasonic probe 10 towards the object 20 also begins to displace the elongated member 14 relative to the probe body 12 at the movable joint 16. In particular, there is axial movement of the elongated member 14 towards the probe body 12, i.e., movement of the elongated member along the longitudinal axis of the elongated member as shown by arrow A.

[0074] As shown in FIG. 2c, continued movement of the ultrasonic probe 10 towards the object 20 causes additional axial movement at the movable joint 16. However, the movable joint 16 is also configured to allow lateral movement of the proximal end of the elongated member 14 (i.e., lateral movement as indicated by arrow L). This lateral movement at the movable joint 16 allows the datum surface 18 to tilt into alignment with the surface of the object 20 as the ultrasonic probe 10 continues to move closer to the object 20. In effect, the lateral movement L permitted by the movable joint 16 allows the elongated member 14 to rotate or pivot about its distal end. Thus, the datum surface 18 rotates and sits flat on the surface of the object 20 at the point (i.e., indicated by arrow 22) where the thickness of the object 20 is to be measured.

[0075] With reference to Figures 3a and 3b, the movement imparted by moveable joints that provide different amounts of lateral restraint are shown.

[0076] Figure 3a is similar to Figure 2c above and also shows an elongated member 14 connected to the probe body 12 by a moveable joint 16 that allows lateral movement. The elongated member 14 can thus be tilted about a point 24 at its distal end, with the tilted elongated member 14' shown in dashed outline. Note that tilting about point 24 is not limited to merely tilting in the plane shown in the drawing.

[0077] FIG. 3b illustrates an ultrasound probe having a movable joint 26 not in accordance with the present invention, where significant lateral movement of the proximal end of the elongated member 28 relative to the probe body 29 is not permitted. In other words, lateral movement of the proximal end of the elongated member 28 is constrained by the movable joint 26. Thus, the elongated member 28 can be tilted about its proximal end (e.g., about pivot point 30), and such movement causes the distal end of the elongated member 28 to move along an arc, as shown by dotted line 27 with the rotated elongated member 28' shown in dashed line. Thus, the movable joint 26 still allows the distal end of the elongated member 28 to change its orientation relative to the probe body 29, but this change in angular orientation of the elongated member 28 requires lateral movement of the distal end of the elongated member 28 relative to the probe body 29.

[0078] When an ultrasonic probe such as that shown in FIG. 3b contacts an object, the only way for the distal end of the elongated member 28 to reorient and align with the surface is to move laterally across the surface of the object. This lateral movement occurs as the elongated member is being moved into engagement with the surface with increasing force, thus potentially damaging (e.g., scratching) the surface being inspected. Such surface damage would be highly undesirable for expensive precision components such as turbine blades. Furthermore, the lateral movement of the distal end of the elongated member 28 would change the lateral location at which the object was measured. For example, the thickness measurement would be removed from the desired measurement point on the object. This leads to potential measurement errors, especially for objects with large thickness variations (such as turbine blades).

[0079] 4-6, various examples of elongate members and ultrasonic transducer assemblies that may be included in the ultrasonic probe 10 described above are described.

[0080] FIG. 4 shows the distal end of the elongated member 40 in free space (top drawing) and when fully engaged with the surface of the object 41 to be measured (bottom drawing). The remainder of the elongated member 40, the attached probe body, and the moveable joint are not shown. The elongated member 40 comprises a tubular sleeve 42. The ultrasonic assembly comprises an ultrasonic transducer 44 mounted within the tubular sleeve 42 and a rigid ultrasonic coupling element 46. An object contacting surface 48 of the rigid ultrasonic coupling element 46 extends distally beyond the tubular sleeve 42. In this example, a datum surface is provided by the surface 48 of the rigid ultrasonic coupling element 46, and the moveable joint of the ultrasonic probe (not shown) allows the elongated member 40 to rotate about its distal end so that the surface 48 sits flat on the surface of the object 41. As mentioned above, the application of an ultrasonic coupling gel or the like is likely to be required to provide sufficient acoustic coupling between such an ultrasonic probe and the object 41. It should be noted that a surface of a more flexible (elastic) ultrasonic coupling element can provide the datum surface instead of a rigid ultrasonic coupling element 4 6. For example, an ultrasonic coupling element can be provided that is formed from an elastic material but is surrounded or enclosed by a rigid carrier element that inhibits lateral expansion of the ultrasonic coupling element.

[0081] FIG. 5 shows an alternative configuration of the elongated member 50. Again, the top view shows the elongated member in free space and the bottom view shows the elongated member when engaged with an object 51 to be measured. The remainder of the elongated member 40, the attached probe body, and the movable joint are not shown. In this embodiment, the elongated member 50 comprises a tubular sleeve 52. The ultrasonic assembly comprises an ultrasonic transducer 54 fixed within the tubular sleeve 52 and an elastically deformable (soft) carrier element 56 having an object contact surface 57 that protrudes (in free space) beyond the distal end of the tubular sleeve 52. An annular end surface 59 of the tubular sleeve 52 provides a datum surface that engages the object 51. The elongated member 50 rotates about its distal end (by virtue of a movable joint, not shown in FIG. 5) when pressed into engagement with the object 51 such that the datum surface (i.e., the annular end surface 59) is angularly aligned with the surface of the object. The elastically deformable (flexible) carrier element 56 is sufficiently elastic to deform and compress flush with the datum surface (i.e., annular end surface 59) when fully engaged with the object 51. Although not shown, an annular gap may be provided between the elastically deformable (flexible) carrier element 56 and the surrounding tubular sleeve 52 to allow for sufficient deformation of the carrier element 56.

[0082] FIG. 6 shows an elongated member 60 having a further alternative configuration. Again, the top view shows the elongated member in free space and the bottom view shows the elongated member when engaged with an object 61 to be measured. The remainder of the elongated member 60, the attached probe body, and the moveable joint are not shown. The elongated member 60 includes a tubular sleeve 62 having an ultrasonic assembly slidably mounted within the tubular sleeve 62. The ultrasonic assembly comprises an ultrasonic transducer 64 acoustically coupled to an ultrasonic coupling assembly 65. The ultrasonic coupling assembly 65 comprises a resilient ultrasonic coupling element 66 contained partially within a tubular carrier shell 68. The ultrasonic transducer 64 and ultrasonic coupling assembly 65 are mounted by a bearing mechanism (not shown) allowing them to translate back and forth along the longitudinal axis of the tubular sleeve 62. A bias in the form of a compression spring (not shown) is also provided which urges the object contacting surface 69 of the resilient ultrasonic coupling element 66 to extend distally beyond the annular end surface 70 of the tubular sleeve 62 in the absence of an applied external force. In an embodiment, the annular end surface 70 of the tubular sleeve 62 provides a datum surface.

[0083] After the object contacting surface 69 engages the object, the ultrasonic assembly translates within the tubular sleeve 62 until the object contacting surface 69 of the resilient ultrasonic coupling element 66 is flush with the reference surface of the annular end surface 70. Furthermore, as the elongated member 60 rotates about its distal end (by virtue of a moveable joint not shown in FIG. 6 ), the datum surface (i.e., the annular end surface 70) moves away from its repeatable rest position and aligns angularly with the surface of the object. In this manner, reliable acoustic contact with the object is provided that allows ultrasonic measurements to be collected. Further details of this type of mechanism are provided below.

[0084] It is preferred that the datum surface is aligned with the surface of the object prior to taking an ultrasonic measurement, however, it should be noted that this is not necessarily the best solution for certain (e.g., non-flat) surfaces. For example, for curved or uneven surfaces that allow the elongated member to self-align with the surface, ultrasonic measurements may be collected from unpredictable directions relative to the surface. In such cases, it may be preferred that the ultrasonic measurements are collected with the elongated member in its repeatable rest position. This may be achieved by detecting when the elongated member contacts the surface (e.g., using a deflection sensor as described below) to provide an approximate measurement of the position of the point on the surface of the object. The machine tool may then move (retract) the ultrasonic probe such that the elongated member loses contact with the surface of the object, thereby returning the elongated member to its repeatable rest position. A further movement of the ultrasonic probe back toward the measurement point on the surface of the object may then be performed to re-engage the elongated member with the surface. However, the ultrasonic probe may be positioned by the machine tool such that the elongated member engages the surface of the object with a force low enough to prevent the elongated member from moving away from its repeatable rest position. The orientation of the elongated member relative to the surface of the object is then known as the ultrasonic measurements are collected.

[0085] With reference to Figures 7a-7e, various views of the ultrasonic probe 300 are shown. Figure 7a is a schematic diagram of the entire ultrasonic probe 300 with a cutaway provided as an enlargement of Figure 7b, showing the movable joint within the probe. Figure 7c again shows a general view of the entire ultrasonic probe 300, but with a different cutaway, showing the ball and roller arrangement of the movable joint in more detail, provided as an enlargement of Figure 7d. Figure 7e shows a cross section through plane II of Figure 7d.

[0086] The ultrasonic probe 300 comprises a probe body 302 having an elongated member 304 extending therefrom. An ultrasonic transducer assembly is provided within the elongated member. An object contacting surface 306 of an ultrasonic coupling element of such ultrasonic transducer assembly is visible at a distal end of the elongated member 304. The elongated member 304 is attached to the probe body 302 by a moveable joint housed within the probe body 302.

[0087] With reference to Figure 7b, the elongate member 304 comprises at its distal end a tubular sleeve 308 which is releasably attached by a threaded attachment to a stylus holder 310. As best seen in Figures 7d and 7e, the stylus holder 310 comprises three equally spaced radially extending rollers 312. The stylus holder 310 is thus an example of a carrier member located at the proximal end of the elongate member 304.

[0088] The probe body 302 includes three pairs of balls 316, also best seen in Figures 7d and 7e. Each pair of balls 316 forms a cleft for receiving one of the rollers 312 of the stylus holder 310, as shown in Figure 7d. The three pairs of balls 316 are fixably secured to the probe body 302, thus forming a seat for the rollers 312 of the stylus holder 310. A compression spring 318 has a proximal end 320 fixed to a portion of the probe body 302. A conical element 322 is attached to a distal end of the compression spring 318. The compression spring 318 exerts a biasing force against a curved recess 324 provided as part of the stylus holder 310.

[0089] The biasing force exerted by the compression spring 318 on the stylus holder 310 (i.e. via the conical element 322 engaging the curved recess 324) urges the rollers 312 of the stylus holder into engagement with the pair of balls 316 which form gaps for the rollers. In the absence of any external forces, the stylus holder 310 adopts a highly repeatable (kinematically defined) rest position relative to its seat in the probe body 302.

[0090] When the elongated member 304 engages an object, any tilting or axial movement (i.e., movement along the longitudinal axis 326) relative to the biasing force causes a pair of balls 316 associated with one or more rollers 312 to disengage. This frees the stylus holder 310 from positional constraints otherwise provided, allowing angular and lateral movement of the stylus holder 310 relative to the probe body 302. In this way, the elongated member 304 can align itself with the surface of the object to be inspected without the distal end of the elongated member moving laterally across the surface of the object. The rollers 312 and balls 316 may also form part of a series electrical circuit, such that disengagement of any one or more of the rollers from the associated pair of balls breaks the circuit, thus providing a so-called trigger signal that can be used to indicate that the elongated member 304 has deflected due to contact with the object. In other words, the rollers 312 and balls 316 may form part of a deflection sensor for sensing deflection of the elongated member 304 relative to the probe body 302. This trigger signal may be used to measure the position of a point on the surface of an object and / or to stop the movement of a machine tool carrying the ultrasonic probe 300.

[0091] A guide channel element 326 is provided in the probe body adjacent the proximal (top) end of the compression spring 318. This guide channel element 326 acts to stabilize or constrain the spring 318 (i.e., limit lateral movement of the top of the spring 318) to prevent uncontrolled deformation or buckling of the spring 318. This ensures that a desired spring velocity is maintained while ensuring that the spring 318 does not limit lateral movement of the stylus holder 310. The guide channel element 326 also acts as a limit or end stop to prevent over-compression of the spring 318 (i.e., the stylus holder 310 can move axially a distance d before engaging the guide channel element 326).

[0092] With reference to FIG. 8, further details are provided of an ultrasonic probe 80 including a linearly movable transducer assembly of the type described above with reference to FIG.

[0093] The ultrasonic probe 80 comprises a probe body 82 and an elongated member 84 extending from the probe body. The probe body 82 is attached to the elongated member 84 by a movable (deflectable) joint 86. The elongated member 84 comprises a tubular sleeve 88 that houses various components that form an ultrasonic assembly. A distal annular end face 89 of the tubular sleeve 88 provides a datum surface that engages an object 104 to be inspected.

[0094] The ultrasonic assembly includes a compression spring 90, an ultrasonic transducer 92, and an ultrasonic coupling assembly 94. The ultrasonic coupling assembly 94 includes a resilient ultrasonic coupling element 96 that is partially contained within an outer tubular carrier shell 98. The carrier shell 984 is made from a substantially rigid material that prevents the resilient coupling element 96 from expanding radially (i.e., the resilient coupling element 96 is radially constrained by the carrier shell 98), but allows longitudinal expansion. A proximal (rear) face 100 of the resilient coupling element 96 protrudes from a proximal end of the carrier shell 98. The ultrasonic transducer 92 is biased (pushed) into contact with the proximal (rear) face 100 of the resilient coupling element 96 by the compression spring 90. A distal (front) face 102 of the resilient coupling element 96 protrudes from a distal end of the tubular carrier shell 98. This distal (front) surface 102 of the resilient coupling element 96 is configured to be pressed into contact with an object 104 to be measured.

[0095] The ultrasonic transducer 92 and ultrasonic coupling assembly 94 are configured to move linearly (i.e., translate back and forth) within the elongated member's tubular sleeve 88. In particular, the ultrasonic transducer 92 is partially encapsulated in a layer of hardened epoxy 106 that provides a bearing surface that slidably engages an inner surface 108 of the tubular sleeve 88. Thus, a sliding bearing is provided that guides the ultrasonic transducer 92 back and forth along a linear axis.

[0096] The process for forming the sliding bearing shown in FIG. 8 includes the following steps. First, the (inner) bearing surface 108 of the tubular sleeve 88 is coated with a wax release agent. The ultrasonic transducer 92 is then held in the required position and orientation within the tubular sleeve 88. A two-part epoxy is injected into the space between the transducer 92 and the inner bearing surface 108 of the tubular sleeve 88, and the epoxy is allowed to solidify. The transducer 92 and the fixed epoxy are slid out of the tubular sleeve 88, and the wax is removed from the (inner) bearing surface 108 of the tubular sleeve 88. The transducer 92 and the attached (i.e., fixed or cured) epoxy 106 are then returned to the tubular sleeve 88 with appropriate lubrication to form a high-precision sliding (linear) bearing. Additionally, a sliding bearing arrangement is also provided for gently linearly guiding the ultrasonic coupling assembly 94 within the tubular sleeve 88, although the precision of such guiding is not critical, as will be explained below.

[0097] The ultrasonic coupling assembly 94, and in particular the transducer 92, may therefore be aligned during manufacture such that the acoustic axis (i.e., the axis along which the ultrasonic waves are directed) is substantially perpendicular to a plane that contains the annular datum surface 89. In other words, the acoustic axis is aligned such that it is substantially parallel to a normal to the datum surface 89. This ensures that when the annular datum surface 89 engages the surface of an object, the ultrasonic waves are directed at the object along a direction perpendicular to the surface.

[0098] The sliding bearing arrangement ensures that the ultrasonic transducer 92 maintains a fixed orientation relative to the normal to the annular end face 89 (i.e., the datum surface) even as it translates back and forth. In other words, a bearing mechanism is provided to limit the movement of the ultrasonic transducer 92 to maintain a fixed transducer orientation relative to the normal to the annular datum surface 89. In particular, at least pitch and yaw of the ultrasonic transducer 92 is substantially prevented.

[0099] In the specification, the ultrasonic coupling assembly 94 is initially biased to its (fully) extended position by the compression spring 90 (note that no mechanical stop is shown defining this fully extended position). In this configuration, the distal (front) surface 102 of the resilient coupling element 96 extends beyond the annular datum (reference) surface 89. This configuration is employed when the ultrasonic measurement probe 80 is not in contact with the object to be inspected (e.g., in free space prior to measurement).

[0100] To obtain ultrasonic measurements, the ultrasonic probe 80 is pushed into engagement with the object, as shown for the object 104 in FIG. 8 . As described above, the movable joint 86 allows the elongated member 84 to rotate about its distal end, so that the annular datum surface 89 lies flat on the surface of the object. Furthermore, the action of bringing the annular ultrasonic coupling assembly 94 into contact with the surface of the object 104 pushes the ultrasonic coupling assembly 94 and the transducer 92 rearwardly into the tubular sleeve 88 until the distal (front) surface 102 of the elastic coupling element 96 is flush with the annular base surface 89. In other words, the ultrasonic coupling assembly 94 adopts a stored (measurement) position in which the acoustic axis is substantially perpendicular to the surface of the object 104. Thus, ultrasonic waves are coupled into the object 104 in a direction perpendicular to the surface.

[0101] A particular advantage of this configuration is that the force with which the distal (front) face 102 of the elastic coupling element 96 is pressed into the surface is governed by the strength of the bias provided by the compression spring 90. Furthermore, since the ultrasonic transducer 92 is also pressed into contact with the proximal (rear) face 100 of the elastic coupling element 96 by the compression spring 90, the compressive force experienced by the elastic coupling element 96 is also controlled by the compression spring 90. This configuration means that any expansion of the elastic coupling element 96, which must be a linear (non-radial) expansion due to the tubular carrier shell 98, does not substantially affect the compressive force applied to the elastic coupling element 96 during measurement (i.e., when in the retracted / measurement position). This enhances repeatability between measurements, even if the elastic coupling element 96 expands significantly due to absorption of refrigerant, etc.

[0102] Although an epoxy-based linear bearing for guiding the ultrasonic transducer is described, other sliding bearing arrangements can alternatively be used, for example, linear ball bearings. This configuration may also allow adjustment of the orientation of the ultrasonic transducer 92. For example, adjustment of the orientation of the acoustic axis of the transducer relative to the normal of the datum surface 89 may be possible after manufacture. For example, this may allow adjustment of the acoustic axis during a repair or recalibration procedure.

[0103] 9a and 9b, there is shown an ultrasonic inspection probe including a probe body 196 and an ultrasonic stylus 198. Figure 9b provides a close-up view of the distal end of the inspection probe of Figure 9a.

[0104] The ultrasonic stylus 198 comprises an elongated tubular structure formed from a first section 200, a second section 202, and a third section 204. The first section 200 comprises a proximal end of the stylus and includes a threaded recess configured to attach the stylus 198 to a corresponding threaded protrusion of the probe body 196. The second section 202 comprises a hollow tube connecting the first section 200 to the third section 204. The three sections 200, 202, and 204 are releasably connected to each other to allow for easy disassembly, although, alternatively, they may be permanently joined to each other. 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.

[0105] An annular datum surface 206 provides a distal face of the third section 204 of the stylus. The ultrasonic coupling assembly 210 and ultrasonic transducer 212 are slidably mounted within the third section 204 of the stylus 198. A sliding (linear) bearing for the ultrasonic transducer 212 is provided by an epoxy layer 230 that slides against a corresponding inner surface 213 of the third section 204 of the stylus. The ultrasonic coupling assembly 210 includes an outer O-ring 232 that slides against a corresponding inner surface of the third section 204 of the stylus. As mentioned above, the ultrasonic coupling assembly 210 includes an ultrasonic coupling element 214, which in this example includes a high consistency rubber. The ultrasonic coupling element 214 is radially constrained within a carrier shell 215 and has a dome-shaped object-contacting (front) surface 216 that protrudes (extends) through an opening defined by the annular datum surface 206 (in the absence of external forces). The ultrasonic transducer 212 is biased into contact with the transducer contacting (rear) surface 218 of the ultrasonic coupling element 214 by a spring 219. During use, the annular datum surface 206 engages the surface of the object and the object contacting (front) surface 216 of the ultrasonic coupling assembly 210 is retracted so that it is flush with the annular datum surface 206. As described above, the spring 219 controls the force applied to the ultrasonic coupling element 214. A wire 220 passes from the ultrasonic transducer 1212 through the stylus 198 and into the probe body.

[0106] The stylus 198 is removably attached to the probe body 196 via a threaded connection provided by a threaded recess and a corresponding threaded protrusion. The deflectable stylus carrier of the probe body 196 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 196 is measured by a suitable sensor. In this way, deflection of the stylus 198 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 198. The probe body 196 of this example also includes a processing unit including a processor for analyzing the ultrasonic signal and a wireless communication unit for transmitting ultrasonic measurements to an associated probe interface. In this example, these are provided on one or more circuit boards located within the probe body 196.

[0107] It should be noted that the above are merely examples of the present invention. Those skilled in the art will appreciate that there are a variety of different ways in which the present invention can be implemented. For example, the probe body can include a protruding stem (e.g., having a similar cross-sectional shape as the elongated member) that carries a movable joint at its distal end. The elongated member can then be attached to the distal end of the stem. Such an arrangement is particularly useful for applications where access to components is limited, such as a measurement bore. It is also possible for an ultrasonic inspection probe to include multiple movable joints (e.g., in series), with elongated members of different lengths being provided for different measurement applications.

Claims

1. 1. An ultrasonic inspection probe, the ultrasonic inspection probe comprising: a probe body for attachment to a coordinate positioning apparatus; an elongated member extending from the probe body, the elongated member including an ultrasonic transducer assembly and a datum surface at a distal end thereof; a movable joint connecting a proximal end of the elongate member to the probe body; Equipped with the movable joint is configured to permit lateral and rotational movement of the proximal end of the elongated member relative to the probe body such that the elongated member can rotate about its distal end to angularly align the datum surface with a surface of an object to be inspected; the movable joint includes a carrier member, a seat, and a biasing mechanism, the carrier member being provided at the proximal end of the elongated member, the probe body including the seat, and the biasing mechanism urging the carrier member into engagement with the seat in the absence of an applied external force, thereby defining a repeatable resting position of the elongated member relative to the probe body; an ultrasound inspection probe, the movable joint configured such that an applied axial movement of the elongated member relative to the probe body causes the carrier member to at least partially disengage the seat, thereby enabling lateral movement of the proximal end of the elongated member relative to the probe body.

2. The ultrasonic inspection probe of claim 1 , wherein the carrier member and the seat are configured to provide a kinematically defined rest position.

3. 3. The ultrasonic inspection probe of claim 2, wherein the carrier member advantageously includes three radially extending rollers, and the seat includes three pairs of balls, each of the pairs defining a gap for receiving one of the rollers.

4. The ultrasonic inspection probe of claim 1 , wherein the biasing mechanism includes a compression spring.

5. The ultrasonic inspection probe of claim 4 , wherein the compression spring engages the probe body and / or the carrier member via a conical member.

6. The ultrasonic inspection probe of claim 4 , wherein the probe body includes a guide channel, and the compression spring is at least partially disposed within the guide channel.

7. 7. An ultrasound inspection probe as claimed in any preceding claim, wherein the movable joint allows movement of the proximal end of the elongate member of at least 1 mm.

8. 2. The ultrasonic inspection probe of claim 1, wherein the elongated member comprises a tubular sleeve that houses the ultrasonic transducer assembly, a distal end of the tubular sleeve providing the datum surface, the ultrasonic transducer assembly comprising an ultrasonic transducer and an elastically deformable ultrasonic coupling element for acoustically coupling to an inspection object.

9. 9. The ultrasonic inspection probe of claim 8, wherein the ultrasonic transducer assembly is mounted within the tubular sleeve by a bearing mechanism configured to guide the ultrasonic transducer assembly back and forth along the longitudinal axis of the elongated member such that the ultrasonic transducer maintains a substantially invariant orientation relative to a surface normal of the datum surface.

10. 2. The ultrasonic inspection probe of claim 1, wherein the ultrasonic transducer assembly comprises an ultrasonic transducer and a rigid coupling element for acoustically coupling the ultrasonic transducer to an inspection object, a distal end of the rigid coupling element providing the datum surface of the elongated member.

11. The ultrasonic inspection probe of claim 1 , further comprising a deflection sensor for sensing deflection of the elongated member relative to the probe body.

12. 10. The ultrasonic inspection probe of claim 1 configured for use with a machine tool, the ultrasonic inspection probe being substantially sealed against coolants or cutting debris and including a wireless communication portion for wirelessly communicating ultrasonic measurements to a remote probe interface.

13. 13. A method for ultrasonically inspecting an object, the method comprising the steps of: using a machine tool to bring an ultrasonic inspection probe according to any one of claims 1 to 12 into acoustic contact with the object; and coupling ultrasonic waves into the object.

14. The ultrasonic inspection probe includes a deflection sensor that senses deflection of the elongated member relative to the probe body, and the method includes: (i) using the deflection sensor to sense physical contact between the elongate member and a surface of the test object; and 14. The method of claim 13, comprising: (ii) using the physical contact detected in step (i) to initiate an ultrasonic measurement of the object using the ultrasonic inspection probe.

15. 15. The method of claim 14, wherein the machine tool is programmed to move the ultrasonic inspection probe towards and / or away from the object between steps (i) and (ii) to establish acoustic contact for ultrasonic measurement of the object.

Images