Patent Description:
Provisional <CIT>, entitled, "Optical Probe with Crash Protection and naming Gurpreet Singh, Paul Racine, John Langlais, and Jie Zheng as inventors [practitioners' file 3740A/ <NUM>], provisional <CIT>, entitled, "Adjustable Optical Probe Clip" and naming Gurpreet Singh, John Langlais, and Jie Zheng as inventors [practitioners' file 3740A/ <NUM>], provisional <CIT>, entitled, "Thermally Optimized Optical Probe Head" and naming Gurpreet Singh, John Langlais, and Jie Zheng as inventors [practitioners' file 3740A/ <NUM>], and provisional <CIT>, entitled, "Optical Probe with Adjustable Probe Platform" and naming Gurpreet Singh, John Langlais, and Jie Zheng as inventors [practitioners' file 3740A/ <NUM>].

The present disclosure relates to coordinate measuring machines and, more particularly, to coordinate measuring machines that use optical probe technologies.

Coordinate measuring machines (CMMs) are used for accurately measuring a wide variety of work pieces. For example, CMMs can measure critical dimensions of aircraft engine components, surgical tools, and gun barrels. Precise and accurate measurements help ensure that their underlying systems, such as an aircraft in the case of aircraft components, operate as specified.

<CIT> discloses a probe holder for a measuring system comprising a first connector having electric and/ or optical signal connections for attaching a measure probe, electric and/ or optical conductor for connecting to the measure probe by first connector, a rotary actuator arranged to rotate the first connector relative to a reference system, an electric and/ or optical slip ring and an angle encoder.

<CIT> discloses an adjustment device for adjusting the alignment of a probe which can be arranged on a measuring device, in particular a probe with a pivotable probe section. The adjustment device has an alignment range and at least one sensor for detecting at least one part of the probe is provided in the alignment range.

<CIT> discloses a coordinate measuring machine having a sensor system and having a holder for the automatically exchangeable fastening of said sensor system, wherein, apart from a probe head the sensor system additionally comprises at least a motor-driven rotary joint by means of which the probe head can be rotated about an axis.

<CIT> discloses a holder to allow temporary attachment of a lamp to a body. The holder has a base which can be attached to the body. The lamp holder is removably attached to the base by the provision of a releasable joint.

<CIT> discloses an intermediate element for the arrangement of a probe pin with respect to the probe pin carrier of a coordinate measuring machine, having a single-piece base body with a probe pin end and a machine end. It is provided here that the machine end is provided with a coupling element and with a means for ensuring a reproducible rotational alignment.

According to claim <NUM>, a probe clip for securing an optical probe to a coordinate measuring machine includes a base configured to removably couple to a probe platform. The probe clip also includes a probe seat configured to removably secure an optical probe to the probe clip as well as a movable joint for movably coupling the probe seat to the base and configured to allow the probe seat to be controllably movable relative to the base. The movable joint may be a ball joint, an extendable device such as a scissors mechanism, or a combination of a ball joint and a scissors mechanism, to name but a few examples.

For example, in some embodiments, the moveable joint is extendable such that the probe seat can be selectively moved closer to and further from the base. In other embodiments, the moveable joint is flexible so as to allow the probe seat to rotate in at least one plane, or two orthogonal planes, relative to the base.

To secure a probe to the probe clip, some embodiments include a retainer configured to removably secure a probe to the probe seat. For example, some embodiments include a spring-loaded retainer. In some such embodiments, the spring-loaded retainer includes a retainer seat to further secure the probe to the probe seat. In some embodiments, the retainer is spring-loaded to absorb thermal stress from the probe seat, thereby reducing the transmission of such thermal stress to the probe. For example, a spring-loaded retainer may include a pre-loaded spring configured to absorb thermal stress from the probe seat, thereby reducing the transmission of such thermal stress to the probe.

In some embodiments, the probe seat is configured to allow a probe having a long axis to controllably rotate about its long axis while secured to the probe seat, and in some embodiments, the probe seat is configured to allow a probe having a long axis to controllably move linearly along its long axis while secured to the probe seat.

The probe seat is configured to release a probe in the event of an impact between the probe and a foreign body in which the impact imposes on the probe an impact force above a given threshold force, the given threshold force being less than a force that would damage the probe, and to retain the probe at an impact force less than or equal to the given threshold force.

To enable additional degrees of adjustment, some embodiments are configured to be controllably slidable along, and re-securable to, the boom such that the location of the probe clip relative to the boom is adjustable without removing the probe clip from the boom. To that end, the base in some embodiments defines an aperture configured to surround the boom. Indeed, some embodiments define a C-shaped aperture configured to incompletely surround the boom. Some embodiments include a set screw configured to release and to re-secure the probe clip to the boom.

An embodiment of a probe head includes a probe platform, and a plurality of probe clips according to claim <NUM> coupled to the probe platform. In some embodiments, the moveable joint is flexible to allow the probe seat to rotate in at least two orthogonal planes relative to the base.

Various embodiments provide crash detection for a CMM probe head. To that end, a probe may move relative to its probe head in the event of a crash or other undesired contact between the probe and another object. After moving in response to the impact event, the probe favorably returns to its desired position.

Probe clips allow a user to adjust the position of a CMM probe relative to the portion of the CMM from which the probe is suspended. Such a probe clip may be configured to enable the user to easily and accurately place the probe clip onto a coordinate measuring machine. Moreover, various like or similar probe clips may be configured to movably and adjustably secure an optical probe to the CMM. To that end, the probe clip may have a probe seat, for holding the probe, movably coupled to a clamp segment by an adjustable joint. The clamp segment movably couples the probe seat to a probe platform on the CMM.

In related embodiments, a re-configurable probe platform (e.g., a "boom") allows substantial freedom for a user to adjust the location and orientation of one or more probes suspended from a probe head. Among other geometries, the probe platform may be circular, or C-shaped. In other embodiments, the probe platform includes a multi-positional connection device, such as an articulated arm, or a segmented arm connected by hinges.

In yet other embodiments, a probe head is configured to resist measurement errors caused by thermal changes. For example, the structures of the probe head, and probes, may be made from similar materials (e.g., steel, stainless steel). In that case, illustrative embodiments may match thermal time constants of features so they respond to changes in temperature on the same or similar time scale.

<FIG> shows one type of coordinate measurement machine <NUM> (hereinafter "CMM <NUM>") that may be configured in accordance with illustrative embodiments. As known by those in the art, the CMM <NUM>, which is supported on a floor <NUM> in this figure, measures an object or workpiece <NUM> on its bed/ table/ base (referred to as "base <NUM>"). Generally, the base <NUM> of the CMM <NUM> defines an X-Y plane <NUM> that typically is parallel to the plane of the floor <NUM>.

To measure an object on its base <NUM>, the CMM <NUM> has movable features <NUM> arranged to move a measuring device <NUM>, such as an optical probe on a probe head <NUM>, coupled with a movable arm <NUM>. Alternately, some embodiments move the base <NUM> (e.g., or a portion of the base <NUM>, such as a moveable table <NUM>) with respect to a stationary measuring device <NUM>. Either way, the movable features <NUM> of the CMM <NUM> manipulate the relative positions of the measuring device <NUM> and the object (or calibration artifact) with respect to one another to obtain the desired measurement. Accordingly, the CMM <NUM> can measure the location of a variety of features of the object or artifact.

The CMM <NUM> has a motion and data control system <NUM> (or "controller" or "control logic") that controls and coordinates its movements and activities. Among other things, the control system <NUM> includes a computer processor <NUM> and the noted sensors/ movable features <NUM>. The computer processor <NUM>, which may include a microprocessor, may have on-board digital memory (e.g., RAM or ROM) for storing data and/ or computer code, including instructions for implementing some or all of the control system operations and methods. Alternately, or in addition, the computer processor <NUM> may be operably coupled to other digital memory, such as RAM or ROM, or a programmable memory circuit for storing such computer code and/ or control data.

Alternately, or in addition, some embodiments couple the CMM <NUM> with an external computer (or "host computer") <NUM>. In a manner similar to the control system <NUM>, the host computer <NUM> has a computer processor such as those described above, and computer memory in communication with the processor of the CMM <NUM>. The memory is configured to hold non-transient computer instructions capable of being executed by the processor, and/ or to store non-transient data, such as data acquired as a result of the measurements of an object on the base <NUM>.

Among other things, the host computer <NUM> may be a desktop computer, a tower computer, or a laptop computer, such as those available from Dell Inc. , or even a tablet computer, such as the iPad™ available from Apple Inc. The host computer <NUM> may be coupled to the CMM <NUM> via a hardwired connection, such as an Ethernet cable <NUM>, or via a wireless link, such as a Bluetooth link or a Wi-Fi link. The host computer <NUM> may, for example, include software to control the CMM <NUM> during use or calibration, and/ or may include software configured to process data acquired during a calibration process. In addition, the host computer <NUM> may include a user interface configured to allow a user to manually operate the CMM <NUM>.

Because their relative positions are determined by the action of the movable features <NUM>, the CMM <NUM> may be considered as having knowledge about data relating to the relative locations of the base <NUM>, and the object or artifact, with respect to its measuring device <NUM>. More particularly, the computer processor <NUM> and/ or computer <NUM> control and store information about the motions of the movable features <NUM>. Alternately, or in addition, the movable features <NUM> of some embodiments include sensors that sense the locations of the table <NUM> and/ or measuring device <NUM>, and report that data to the computers <NUM> or <NUM>. The information about the motion and positions of the table and/ or measuring device <NUM> of the CMM <NUM> may be recorded in terms of a two-dimensional (e.g., X-Y; X-Z; Y-Z) or three-dimensional (X-Y-Z) coordinate system referenced to a point on the CMM <NUM>.

Some CMMs also include a manual user interface <NUM>, such as that shown generically in <FIG> and as further schematically illustrated in <FIG>. As shown, the manual user interface <NUM> may have control buttons 125A and knobs 125B that allow a user to manually operate the CMM <NUM>. Among other things, the interface <NUM> may enable the user to change the position of the measuring device <NUM> or base <NUM> (e.g., with respect to one another) and to record data describing the position of the measuring device <NUM> or base <NUM>.

In a moving table CMM, for example, the measuring device <NUM> may also be movable via control buttons 125C. As such, the movable features <NUM> may respond to manual control, or be under control of the computer processor <NUM>, to move the base <NUM> and/ or the measuring device relative to one another. Accordingly, this arrangement permits the object being measured to be presented to the measuring device <NUM> from a variety of angles, and in a variety of positions.

<FIG> schematically illustrate a probe head <NUM> of the CMM <NUM> while measuring the above noted workpiece <NUM> which, in this example, is a propeller. In this embodiment, the probe head <NUM> includes a mount <NUM> configured to couple the probe head <NUM> to the movable arm <NUM> of the CMM <NUM>. In some embodiments, the mount <NUM> may be an integral part of the arm <NUM>. In other embodiments, the probe head <NUM> may be configured to couple to a stationary part of the CMM <NUM>. Among others, this may be applicable to embodiments of the CMM <NUM> in which the table <NUM> moves the workpiece <NUM> relative to the probe <NUM> or probe head <NUM>. In some embodiments, the mount <NUM> includes electrical connections, for example, to provide power to a sensor <NUM> or probes <NUM>. Alternatively or in addition, these electrical connections may couple with communication circuits to provide communications capability between: A) the control system <NUM> or the computer <NUM>, and B) the sensor <NUM> or one or more probes <NUM>. Details of the sensor <NUM>, probes <NUM> and electrical connections are discussed below.

The probe head <NUM> also includes a probe platform <NUM>, as schematically illustrated in <FIG>, movably coupled to the mount <NUM>, and configured to support one or more probes <NUM> for use in measuring the workpiece <NUM>. The probe <NUM> may be removably coupled to the probe platform <NUM> by any of a variety of conventional means, or unconventional means such as with probe clips <NUM> (see <FIG> and others, discussed below). In illustrative embodiments, the probe <NUM> may be considered to be removably coupled to a probe platform <NUM>, for example, if the probe <NUM> can be affixed to the probe platform <NUM>, and/ or removed from the probe platform <NUM>, without damaging the probe <NUM> or the probe platform <NUM>.

Some embodiments also include a housing <NUM>, as described further below, to provide physical protection to the probe platform <NUM>, probes <NUM> or other components of the probe head <NUM> against contact with another object. In some embodiments, the probe head <NUM>, probe platform <NUM>, and probes (<NUM>-<NUM>, see <FIG>) are be made from identical materials (e.g., steel, stainless steel), so that they respond to changes in temperature on the same or a similar time scale, and/ or with matched thermally-induced changes in dimensions.

In some embodiments, some or all of the probe head <NUM>, boom <NUM>, and probes (e.g., the probe <NUM>), are be made from different materials, but materials with matched thermal time constants (e.g., coefficients of thermal expansion-"CTEs") and matched thermal lengths. Accordingly, features made of such materials are expected to respond to changes in temperature on the same or a similar time scale, with matched thermally-induced changes in lengths. Illustrative embodiments may form each of the probe head <NUM>, probe platform <NUM> and probes <NUM>-<NUM> from a plurality of different materials having a composite CTE that match as noted above. For example, the probe platform <NUM> may be formed from multiple materials that have a composite CTE that matches those of the probe head <NUM> and the probes <NUM>-<NUM>.

The sensor <NUM> is operably coupled between the mount <NUM> and the probe platform <NUM>, such that motion of (or displacement of) the probe platform <NUM> relative to the mount <NUM> is transmitted to the sensor <NUM>. For example, the probe platform <NUM> may be in a nominal position, as schematically illustrated in <FIG>, when the CMM <NUM> is in normal operation, or not in use. However, when a portion of the probe head <NUM> (e.g., the probe platform <NUM>; the probe <NUM>; the housing <NUM>) contacts an object (e.g., the workpiece <NUM>; another part of the CMM <NUM>, a user, or another object near the CMM <NUM>), the probe head <NUM> moves (i.e., is displaced) relative to the mount <NUM>. To illustrate this, <FIG> schematically shows the probe head <NUM> displaced from its nominal position. The displacement, or motion, of the probe head <NUM> is transmitted to the sensor <NUM> through, e.g., the probe platform <NUM>. In illustrative embodiments, any contact that causes the sensor <NUM> to detect such displacement may be referred to as "dynamic" contact.

The mount <NUM>, the sensor <NUM>, and the probe platform <NUM> are thus configured so that dynamic contact between A) the probe platform <NUM> or the probe <NUM> coupled to the probe platform <NUM>, and B) an object causes a change in an electrical and/ or mechanical property of the sensor <NUM>. In this way, the sensor <NUM> can detect a crash between the probe head <NUM> and another object. The CMM <NUM> may react to a crash in one or more ways, as described below.

<FIG> schematically illustrate three different close-up views of an embodiment of the probe head <NUM> of <FIG>. These views show the probe head <NUM> with several probes (<NUM>, <NUM>, <NUM>, and <NUM>) suspended from the probe platform <NUM> (e.g., also referred to as a boom) by corresponding probe clips (<NUM>, <NUM>, <NUM>, and <NUM>). Each probe is in electrical communication with the controller <NUM> via a cable <NUM>, and the sensor <NUM> is in electrical communication with the controller <NUM> via cable <NUM>, as schematically illustrated in <FIG>.

The boom <NUM> is shown as being L-shaped, although it may have other shapes/ geometries, and in some embodiments has an adjustable shape. For example, the boom <NUM> may include a plurality of components that are movable relative to each other. In some embodiments, the boom <NUM> may simply include two boom segments (<NUM>, <NUM>) connected by joint <NUM> (<FIG> and <FIG>), which may be a simple hinge or ball joint, to name two examples. As such, in this embodiment, the boom <NUM> can include two boom segments (<NUM>, <NUM>) that can move relative to each other at least as permitted by the joint <NUM>. The embodiment of <FIG> and <FIG> may have such a two-segmented boom <NUM> with a simple hinge <NUM>, so that the two boom segments <NUM>, <NUM> of that embodiment may rotate about the Z-axis.

Other embodiments, however, may permit additional freedom of movement. For example, the segments <NUM>, <NUM> may be coupled so that they have more than two degrees of freedom of motion. Specifically, one or both of the boom segments may be configured to extend linearly along their respective lengths, and/ or to rotate about an axis defined by those lengths.

Those skilled in the art may select a joint mechanism <NUM> permitting the noted movement. For example, among other things, the connection mechanism <NUM> between boom segments <NUM>, <NUM> may include a hinge, ball and socket connection, telescoping connections, etc..

Before use, the user may re-configure or re-orient the boom segments <NUM>, <NUM> to more effectively operate with the workpiece <NUM> and overall CMM <NUM>. Accordingly, the CMM <NUM> thus may use this re-configurable boom <NUM>, movable probe clips <NUM>, or both to more effectively measure a workpiece <NUM>.

The boom <NUM> is, in turn, movably suspended from the sensor <NUM> which, as noted above, may be positioned in the mount <NUM>. This connection preferably is made so that the boom <NUM> is movable with respect to the mount <NUM>. In general, the sensor <NUM> may detect motion or displacement of the boom <NUM> by sensing changes in electrical properties of circuit elements in physical (although not necessarily direct) contact with the boom <NUM>. In illustrative embodiments described below, the sensor <NUM> includes a kinematic seat <NUM>, for example as discussed with regard to <FIG>.

In this embodiment, a stem <NUM> suspends the boom <NUM> from the kinematic seat <NUM>. As such, the length may determine, in part, the sensitivity of the crash detector feature. The kinematic seat <NUM> is thus configured to detect motion of the boom <NUM> relative to the mount <NUM>. These simplified illustrations schematically illustrate the function of a kinematic seat <NUM>.

As noted above, some embodiments also include the rigid housing <NUM> (or "shroud" or "apron"), which is movably coupled to the mount <NUM>, for example by one or more pivot fasteners <NUM> that allow the housing <NUM> to move relative to the mount <NUM>. The housing <NUM> may be coupled to the mount <NUM> by a plate <NUM>. In the embodiment of <FIG>, the housing <NUM> is essentially cylindrical, although it does not have a complete cylindrical surface so as to allow the probes (<NUM>-<NUM>) to extend beyond the housing <NUM>. This embodiment of the housing <NUM> has its axis of symmetry parallel to the long dimension of the stem <NUM>, although other shapes and/ or orientations are possible.

Some embodiments couple the housing <NUM> to the mount <NUM> via a movable element (e.g., a stress absorbing spring system) <NUM>, as schematically illustrated in <FIG>. The spring system <NUM> is coupled to the mount <NUM> by a collar <NUM>, and in this embodiment includes three flexible elements <NUM>, in a "T" configuration, positioned between the mount <NUM> and pivot fasters <NUM> so that the plate <NUM> is coupled to the mount <NUM> by the spring <NUM>. In this way, thermal expansion of the plate <NUM> is at least partially absorbed by the motion of the spring <NUM> so that the plate <NUM> is not over-constrained and does not push against the mount <NUM>. Such interaction, without the spring <NUM>, undesirably can cause the circumferential edge of the plate <NUM> to move away from the mount <NUM>, which can transmit to the boom <NUM> via a rod <NUM>. The spring <NUM> favorably mitigates transmission of thermal expansion from the housing <NUM> to the boom <NUM> and probes <NUM> coupled to the boom <NUM>.

In addition, the spring <NUM> allows the housing <NUM> to move relative to the mount <NUM>, for example when the housing <NUM> contacts, or is in contact with, an object, such as the workpiece <NUM>, a different portion of the CMM <NUM>, an operator, or a foreign body. Moreover, the spring <NUM> may cause the housing <NUM> to return to a nominal position (e.g., as in <FIG>) from a displaced position (e.g., <FIG>) after the contact with the object is removed.

The housing <NUM> is physically coupled to the sensor <NUM> via a rod (or "strut") <NUM>. In the embodiments of <FIG>, the rod <NUM> is coupled to the sensor <NUM> via the boom <NUM> and thus via the stem <NUM>. Consequently, motion of the housing <NUM> relative to the mount <NUM> (e.g., if the housing <NUM> contacts an object or another part of the CMM) is transmitted to the sensor <NUM>, which detects the crash similar to the crash detection describe above.

In some embodiments, the rod <NUM> is isolated from the housing <NUM> via a hysteretic mechanical coupling <NUM> that mitigates or prevents transmission of thermal stress (e.g., mechanical motion in the housing arising from a change in the housing temperature) from reaching the sensor <NUM>, but which transmits to the sensor motion or displacement of the housing <NUM> due to in impact of the housing with an object. Preferably, this arrangement thus ensures that changes in the housing temperature do not cause a corresponding change in an important electrical property of the sensor <NUM>. For example, in some embodiments, as schematically illustrated in <FIG>, the hysteretic coupling <NUM> has an aperture <NUM> in the bottom <NUM> of housing <NUM>, and a fastener <NUM> passing through the aperture <NUM> securing the housing <NUM> to the rod <NUM>. The diameter <NUM> of the aperture <NUM> is larger than the outside diameter <NUM> of the fastener <NUM>. As such, the radial sides <NUM> of the fastener <NUM> do not contact the side (inner wall) <NUM> of the aperture <NUM>, ensuring that lateral (X-axis) motion of the housing <NUM> due to thermal expansion is not transmitted to the fastener <NUM>.

In some embodiments, the housing <NUM> includes a mechanical interface <NUM> (<FIG>) that allows an optical cable to pass through the housing <NUM> to reach an optical probe suspended from the boom <NUM>. In some embodiments, the mechanical interface <NUM> is in the form of an aperture passing through the housing <NUM>.

In the event that the CMM <NUM> senses a crash (an impact event) between the probe head <NUM> or the probe platform, or the probe <NUM>, and another object, the CMM <NUM> may take a variety of actions, such as immediately stopping the motion of the probe head <NUM>, or the motion of a CMM table; repeating one or more previous measurements; discarding previous measurements; and/ or notifying a CMM operator that a crash occurred. For example, the sensor <NUM> may be coupled with the controller <NUM> that takes the appropriate action after it receives a signal from the sensor <NUM> indicating a crash.

<FIG>schematically illustrates an alternate embodiment of the boom <NUM>. In this embodiment, the boom <NUM> is in the shape of a torus (i.e., it is toroidal), while in other related embodiments, the boom <NUM> may have a "C" shape. Such embodiments permit a user to suspend the probe <NUM> substantially anywhere along the boom <NUM>, thus providing a user a great deal of flexibility in where to place the probe <NUM>, and where to place multiple probes relative to one another relative to a <NUM> degree area. For example, the embodiment of <FIG>is schematically illustrated with two probes <NUM>, although the boom <NUM> could accommodate more or fewer probes <NUM>.

In some embodiments, the probe <NUM> is coupled to the boom <NUM>, or to the mount <NUM>, by a flexible arm <NUM> as schematically illustrated in <FIG>. The arm <NUM> can have any number of segments, and may be extensible and/ or articulated to provide any desired number of degrees of freedom. The arm <NUM> in this example has three arm segments (<NUM>, <NUM> and <NUM>) coupled by joints (<NUM> and <NUM>) that allow several degrees of freedom with respect to the other joints. Accordingly, this embodiment provides to a probe <NUM> a plurality of degrees of freedom relative to the boom <NUM> or mount <NUM>, as indicated by the double-headed arrows near the joints <NUM>, <NUM> and probe <NUM>. In addition, one or more of the arm segments <NUM>, <NUM>, and <NUM> may be extendable axially along the long dimension of the segments themselves. As shown, the probe <NUM> couples to arm segment <NUM>, while the arm <NUM> couples to the boom <NUM>, or mount <NUM>, at segment <NUM>.

Other embodiments may have a single boom segment (e.g., one of segments <NUM>, <NUM>, or <NUM>) that can move about the other portions to which it is connected. Various other embodiments may have more than two or three boom segments <NUM>, <NUM>, or <NUM>, each of which are configured to be adjustable relative to one another as noted above.

The arm <NUM> may thus allow the probe <NUM> to be moved in and around a workpiece <NUM>. As suggested, other embodiments may have more or fewer arm segments and moveable joints, and may have more or fewer degrees of freedom.

<FIG> schematically illustrate one of the above noted kinematic seat <NUM>. In this embodiment, the kinematic seat <NUM> includes a T-shaped bracket <NUM> having a base portion <NUM> orthogonally coupled with a cross-bar <NUM>. The cross-bar <NUM> may have an elongated shape, or form a region having a large surface area (e.g., the top face of a circular shaped member). At least the cross-bar <NUM> is electrically conductive. In other embodiments, however, both the cross-bar <NUM> and base portion <NUM> are electrically conductive.

The kinematic seat <NUM> also includes several conductive seats. In <FIG>, only two such seats are schematically illustrated (<NUM>, <NUM>), but various embodiments may have three, four, or more such conductive seats. The cross-bar <NUM> is mechanically biased against the seats (<NUM>, <NUM>) by a spring <NUM>, which pushes against the mount <NUM>. When no force, or a small force, is applied to the base portion <NUM>, the cross-bar <NUM> is in physical and electrical contact with the conductive seats (<NUM>, <NUM>. When in this state, an electrical current passes from one seat (<NUM>) through the cross-bar <NUM> to the other seat (<NUM>), where the current is detected by a continuity detector <NUM>.

However, a force applied to the base portion <NUM> of the bracket <NUM> (which base portion <NUM> may include the stem <NUM>, or which may be physically coupled to the stem <NUM>) causes the cross-bar <NUM> to break its electrical contact with one or more of the seats (<NUM>, <NUM>). This causes the continuity detector <NUM> not to detect a current flowing through the seats (<NUM>, <NUM>) and cross-bar <NUM>, or alternately, to detect an absence of such a current. For example, in <FIG>, a force in the +X direction has caused the cross-bar <NUM> to lose contact with the seat <NUM>. Consequently, the CMM knows that the probe head <NUM> (or other coupled CMM part) has crashed into something by moving the in X direction. Note that, although <FIG> schematically illustrates the kinematic seat <NUM> operating in the X-axis, the same principle applies in the Y-axis (which is orthogonal to the X-axis and the Z-axis) using seats (e.g., <NUM>, <NUM>) and the cross-bar (<NUM>) in that axis, with the result that the kinematic seat <NUM> can detect crashes in either the +/ - X-axis and/ or the +/ - Y-axis.

In <FIG>, a force in the +Z direction has caused the cross-bar <NUM> to lose contact with both seat <NUM> and seat <NUM>. Consequently, the CMM knows that the probe head has crashed into something by moving the in -Z direction.

Consequently, the kinematic seat <NUM> is a type of sensor that detects motion or displacement of the bracket <NUM>. In practice, the bracket <NUM> is physically coupled to the boom <NUM>, which is physically coupled to the probes (<NUM>-<NUM>). This coupling is made so that the kinematic seat <NUM> detects motion of the bracket <NUM> caused by contact between any of the bracket <NUM>, boom <NUM>, probes (<NUM>-<NUM>), housing <NUM>, or other feature of the probe head <NUM>, and another object. As such, the kinematic seat <NUM> may be referred to as a "crash detector.

Although the kinematic seat <NUM> of the above embodiments detects motion of the boom <NUM> by make-or-break electrical connections between the cross-bar <NUM> and the seats <NUM>, <NUM>, the sensor <NUM> may operate differently. For example, some implementations of the sensor <NUM> may detect motion of the cross-bar <NUM> by coupling the cross-bar <NUM> to one or more piezo resistors (represented by <NUM>, <NUM> in <FIG>) such that physical stress (e.g., compression; tension) imposed by the cross-bar <NUM> on one or more of the piezo resistors <NUM>, <NUM> causes a change in the electrical resistance of the piezo resistor(s), which change may be detected by detector <NUM>. In another example, some sensor <NUM> may detect motion of the cross-bar <NUM> by coupling the cross-bar <NUM> to one or more variable capacitors (also represented by <NUM>, <NUM> in <FIG>) such that physical motion of the cross-bar <NUM> causes a change in the electrical capacitance of at least one of the variable capacitors that is detected by the detector <NUM>. In some piezo resistor embodiments, the cross-bar <NUM> need not be conductive. Micro electromechanical systems ("MEMS devices") also may be used to aid in sensing. For example, the sensor <NUM> could be an accelerometer or gyroscope configured to detect a motion of, or change in motion of, the arm <NUM> or probe head <NUM>.

<FIG> schematically illustrate the noted elongated optical probe <NUM>, which defines an elongated axis (<NUM>, parallel to the B-axis), and an axis <NUM> perpendicular (or normal) to the elongated axis <NUM> (and parallel to the A-axis). The embodiment of <FIG> includes an optical probe that measures the workpiece <NUM> by illuminating the workpiece with light projected from the probe <NUM>, and reflected back to the probe <NUM> by the workpiece. To that end, the probe <NUM> has an optical transceiver <NUM> configured to transmit light and receive a reflection of that light (the light and its reflection are schematically illustrated by double-headed arrow <NUM>). Note that the direction of the light (<FIG>) may be changed by rotation of the probe <NUM> around its elongated axis <NUM> (<FIG>). Alternately, or in addition, some probes transmit light and receive reflections from the probe <NUM> along axis <NUM>.

<FIG> schematically illustrates an embodiment of the probe <NUM> with adjustment indicia. Some measurements by the CMM <NUM> may require that a probe be at or near a certain position, or in a particular orientation, for example relative to a probe clip, in order to operate correctly. To that end, some embodiments of probes <NUM> include axial indicia <NUM> at one or more locations along their length to indicate, to an operator, the radial position of the probe <NUM> within a probe clip (e.g., how the probe <NUM> is turned within a probe seat <NUM>, discussed below with regard to <FIG>). Alternately, or in addition, some embodiments of probes <NUM> include axial indicia <NUM> at one or more locations on one or both of its end faces to indicate, to an operator, the radial position of the probe <NUM> within a probe clip.

Alternately, or in addition, some probes <NUM> may include radial indicia <NUM> at one or more locations around their circumference, to indicate, to an operator, the axial position of the probe <NUM> within a probe clip (e.g., where the probe is positioned along the seat <NUM>).

<FIG> are shown and described with respect to three orthogonal axes labeled A, B and C. Although axes A, B and C may align with axes X, Y and Z, and/ or axes Q, R and S in other figures, such alignment is not required and is not a limitation of various embodiments.

<FIG> schematically illustrate additional details of illustrative embodiments of an embodiment of the probe clips <NUM>, <NUM>, <NUM> and <NUM>, using probe clip <NUM> for illustrative purposes.

Many of the features of the probe clip <NUM> and probe <NUM> are movable relative to a boom <NUM> on which the probe clip is mounted. Some such motions may be described as linear in that a feature moves along an axis, while other such motions may be described as rotational in that a feature rotates about an axis.

Some of the figures include illustrative axes (e.g., some sets of axes show three dimensions Q, R and S of <FIG>, while others show only two axes, such as Q and S, or R and S) for reference purposes. For purposes of describing certain features, the following terms are defined relative to the reference axes:.

The probe clip <NUM> has a probe seat segment <NUM> and a clamp segment <NUM> coupled together by movable joint <NUM>. The movable joint <NUM> is adjustable to allow the position or orientation of the probe seat segment <NUM> to be adjustable relative to the clamp segment <NUM>, e.g., in both azimuth and elevation. In some embodiments, the joint <NUM> may be a ball joint or spherical joint. Such a joint may be configured to allow the above noted probe seat <NUM>, holding a probe <NUM>, to rotate in at least two orthogonal planes relative to the clamp segment <NUM>, thereby allowing a user to adjust the location and/ or orientation of the probe <NUM> relative to the clamp segment <NUM>.

To support the probe <NUM> the probe seat segment <NUM> includes a concave (e.g., v-shaped) shaped seat <NUM>, and a spring-loaded retainer <NUM> to couple the probe <NUM> into the seat <NUM>. The spring-loaded retainer <NUM> is coupled to the probe seat segment <NUM> at a slot <NUM> (<FIG>), and may include a retainer seat <NUM>. In addition, the seat <NUM> and the retainer seat <NUM> preferably are positioned in opposition and cooperate to secure the probe <NUM> into the seat <NUM>. In some embodiments, if the probe <NUM> is displaced from its position in the seat <NUM>, for example due to contact between the probe <NUM> and an object, the retainer <NUM> returns the probe <NUM> to its intended seated position after the contact is terminated. The nature of the probe seat <NUM> and spring retainer <NUM> is such that the probe <NUM>, in some embodiments, returns to a prescribed position in the probe seat <NUM> with a significant degree of accuracy, such as would allow a measurement process to continue.

<FIG> schematically illustrates a side-view of the clamp segment <NUM>, to clearly show an aperture <NUM> configured to couple the probe clip <NUM> to the boom <NUM>. The diameter of the aperture <NUM> preferably is slightly larger than the diameter of the boom <NUM>. Accordingly, the boom <NUM> fits into and through the aperture <NUM> such that the clamp base <NUM> slides onto the boom <NUM>. Although the aperture <NUM> is schematically illustrated as a circle, the aperture <NUM> may have other shapes, such as square, rectangular, or irregular shapes, and may generally match the shape of a corresponding boom <NUM>. Some embodiments also include a set screw <NUM> passing through the clamp base <NUM> and into the aperture <NUM>. When coupled, the set screw <NUM> may be tightened against the boom <NUM> positioned through the aperture <NUM> to secure the clamp base <NUM> to the boom <NUM>.

The elevation of the probe <NUM> in the probe clip <NUM> (e.g., in probe seat segment <NUM>) may be adjusted by rotating the clamp segment <NUM> around the boom <NUM>. For example, a user may loosen the set screw <NUM>, move the clamp segment <NUM> to a new desired position (e.g., by rotating the clip <NUM> around the Q axis), and tighten the set screw <NUM> to fix the clip <NUM> in the new position.

The joint <NUM> is selectively movable, and may be fixed into a selected position, e.g., under the control of a user. The joint <NUM> may rotate, e.g., about the S axis, the Q axis or the R axis, and its length may be extended or reduced along the S axis.

In the examples below, the position of the probe <NUM> relative to the boom <NUM> is changed by manipulating:.

Although illustrated separately, any of the features described below may be made and used in combination to adjust the location and orientation of a probe <NUM> relative to a boom.

<FIG> schematically illustrate the probe clip <NUM> in two positions: an initial position in <FIG>, and a subsequent position in <FIG>, after the probe clip <NUM> has translated along the boom <NUM> in the Q direction. As shown in <FIG>, the probe clip <NUM> is nearer to boom position <NUM> than to position <NUM>, while in <FIG> the probe clip <NUM> is nearer (i.e., has moved to be nearer) to boom position <NUM> than to boom position <NUM>.

To move the probe clip <NUM>, a user may loosen the set screw <NUM> and slide the clip <NUM> along the boom <NUM> to the subsequent position. When in the appropriate boom position, the user may then tighten the set screw <NUM> to secure the clip <NUM> to the boom <NUM>.

<FIG> schematically illustrate one embodiment of the probe <NUM> in the probe seat <NUM> of the seat segment <NUM>. In <FIG>, the seat segment <NUM> has been extended, relative to the clamp segment <NUM>, by extension of the joint <NUM> along the S axis. Among other things, the joint <NUM> may include a threaded section so that the seat segment <NUM> may be moved relative to the clamp segment <NUM> in a screw-like fashion. As another example, the joint <NUM> may include a scissor-like mechanism enabling the seat segment <NUM> to move relative to the clamp segment <NUM> by expanding or contracting the scissor-like mechanism.

<FIG> schematically illustrate another embodiment of the probe <NUM> in the probe seat <NUM> of the seat segment <NUM>. More specifically, <FIG> schematically illustrate the probe <NUM> in two positions: an initial position in <FIG> in which point <NUM> on the probe <NUM> is near the seat segment <NUM>, and a subsequent position in <FIG> in which point <NUM> on the probe <NUM> is farther from the seat segment <NUM>, after the probe <NUM> has been moved axially (i.e., along its elongated axis, along the V-shaped groove <NUM>).

<FIG>and <FIG> schematically illustrate another embodiment of the probe clip <NUM> containing the probe <NUM> in the probe seat <NUM>. More specifically, <FIG>and <FIG> schematically illustrate the probe <NUM> in two positions: an initial position in <FIG>, and a subsequent position in <FIG>. As shown, in <FIG>, the probe <NUM> has been rotated (radial motion) from its position in <FIG> about its elongated axis <NUM>.

<FIG> schematically illustrate another embodiment in which the probe <NUM> is positioned at two distinct elevations: an initial elevation in <FIG>, and a subsequent elevation in <FIG>, after the seat segment <NUM> has been rotated (about the Q axis) relative to the clamp segment <NUM>. In this embodiment, the joint <NUM> is rotatable about the Q axis.

<FIG> schematically illustrate yet another embodiment in which the seat segment <NUM> has two distinct azimuth positions: an initial position in <FIG>, and a subsequent position in <FIG>, after the seat segment <NUM> has been rotated (about the S axis) relative to the clamp segment <NUM>. In this embodiment, the joint <NUM> is rotatable about the S axis.

In some embodiments, two or more probes may be coupled to a boom <NUM> to allow the CMM <NUM> to measure a workpiece <NUM> from a variety of different directions. For example, in <FIG>, three probes (<NUM>, <NUM> and <NUM>) are adjacent to one another and coupled to the boom <NUM>. The orientation of the probe <NUM> relative to its probe clip <NUM> may be set so that the light transmitted from and received by the probe <NUM> is along the Q axis in the -Q direction, so that the probe <NUM> can illuminate and measure a workpiece <NUM> when the probe is located, relative to the workpiece <NUM>, in the +Q direction. Similarly, the orientation of the probe <NUM> relative to its probe clip <NUM> may be set so that the light transmitted from and received by the probe <NUM> is along the Q axis in the +X direction, so that the probe <NUM> can illuminate and measure the workpiece <NUM> when the probe is located, relative to the workpiece <NUM>, in the -Q direction. The light transmitted from and received by the probe <NUM> is along the R axis, so that the probe <NUM> can illuminate and measure the workpiece <NUM> when the probe is located, relative to the workpiece <NUM>, in the R axis.

In this way, the CMM <NUM> can measure the workpiece <NUM> by moving the probe head <NUM> to various positions along the Q and R axis, and use the probes <NUM>, <NUM> and <NUM> independently (e.g., one at a time) depending on the location of the probe head and probes relative to the workpiece <NUM>. Some embodiments, however, may use one or more of the probes <NUM>, <NUM> and <NUM> at the same time. Because the location and orientation of each of the probes <NUM>, <NUM> and <NUM> relative to the boom <NUM> and relative to one another, is adjustable as described above, a user can avoid having to remove a probe and replace it with another probe when a probe of a different orientation is required or desired. Rather, the user can simply adjust and adapt the location and orientation of a probe using the features described herein. This reduces the need for a variety of different probes and clamps, and makes operation of the CMM faster and more efficient.

<FIG> are shown and described with respect to three orthogonal axes labeled Q, R and S. Although axes Q, R and S may align with axes X, Y and Z, and/ or axes A, B and C, in other figures, such alignment is not required and is not a limitation of any embodiment.

<FIG> schematically illustrates another embodiment (<NUM>) of a probe clip, in which two arms <NUM>, <NUM> extend from a base <NUM>. The base <NUM> may be a probe seat that couples to a clamp segment in any of the ways schematically illustrated by probe seats <NUM> and clamp segments <NUM> in <FIG>, or could be a clamp segment <NUM> configured to couple directly to a probe platform. One of the arms (e.g., the arm <NUM>) includes a v-shaped seat (<NUM>) that defines an axis (<NUM>; parallel to the Q-axis in <FIG>) that extends in a direction that does not intersect the base <NUM>. The second arm <NUM> has a retainer seat <NUM>, and acts as a spring-loaded retainer to secure the probe <NUM> into the v-shaped seat <NUM>.

Another embodiment of the clamp segment <NUM> is schematically illustrated in <FIG>, and includes an aperture <NUM> that includes an opening <NUM> to one, such that the aperture <NUM> forms an open "C" shape. The clamping screw <NUM>, when tightened into the clamp segment <NUM> across the opening <NUM>, reduces the gap width of the opening <NUM> such that the clamp segment <NUM> acts as a clamp to secure the clamp segment <NUM> to the boom <NUM>. To that end, the clamping screw <NUM> may screw into a threaded aperture <NUM> in the clamp segment <NUM>. Alternately, in some embodiments, the (optionally threaded) aperture <NUM> may pass completely through the clamp segment <NUM>, across the opening <NUM>, and the clamping screw <NUM> is secured to the clamp segment <NUM> by a nut <NUM>.

In some embodiments, a pre-loaded spring <NUM> secures the probe <NUM> to the probe seat segment <NUM>, as schematically illustrated in <FIG>. In such embodiments, changes in mechanical properties due to thermal stress are absorbed by the pre-loaded spring <NUM>, rather than being allowed to distort the probe <NUM> (or other structure, which also can distort the probe <NUM>). In such embodiments, if thermal expansion of features (e.g., probe seat segment <NUM>; retainer <NUM>) increases force on the probe <NUM>, the pre-loaded spring <NUM> flexes to absorb the force, thereby reducing the transmission of that force increase to the probe <NUM>. Similarly, if thermal contraction of such features decreases force on the probe <NUM>, the pre-loaded spring <NUM> flexes to increase its force on the probe <NUM>. Accordingly, the probe <NUM> should remain aligned in the appropriate manner.

In some embodiments, the pre-loaded spring <NUM> includes a screw <NUM> that adjusts (e.g., to increase and decrease) the force applied by the pre-loaded spring <NUM>.

In some embodiments, the pre-loaded spring <NUM> is sufficiently flexible to absorb thermally-induced forces, yet sufficiently rigid to transmit, to a sensor <NUM> in the mount, motion or displacement of the probe <NUM> relative to the mount <NUM> in the event of a crash of the probe into another object. A person of ordinary skill in the art, having possession of this disclosure, can establish or adjust the flexibly and rigidity of the pre-loaded spring <NUM> according to the application in which the pre-loaded spring <NUM> is used.

<FIG> is a flow chart illustrating a method by which some embodiments of the CMM <NUM> react to detecting a crash between a probe head <NUM>, or a probe <NUM>, and another object.

The CMM <NUM> moves the probe <NUM>, or the probe head <NUM>, relative to another part of the CMM <NUM>, at step <NUM>. For example, the CMM <NUM> may move the arm <NUM> relative to a base <NUM>, or may move the base <NUM> (e.g. a table) relative to the probe <NUM>. In any case, the probe <NUM> or probe head <NUM> may unintentionally contact an object in a crash.

At step <NUM>, the CMM <NUM> detects the crash, for example by detecting motion or displacement of a probe head <NUM> relative to an arm, <NUM>. In some embodiments, the above noted sensor <NUM> is coupled to the controller <NUM> such that the controller <NUM> detects <NUM>) a signal from the sensor indicating motion or displacement of a probe head <NUM> relative to an arm <NUM> by a signal, and/ or <NUM>) a change in a signal from the sensor <NUM>.

In response to detecting motion or displacement of a probe head <NUM>, the CMM <NUM> may take one or more actions. At step <NUM>, the CMM <NUM> may take remedial action, such as stopping motion of the probe <NUM> or probe head <NUM>, or causing the probe <NUM>, probe head <NUM>, or arm <NUM> to repeat, in reverse order, one or more movements that preceded the crash. Indeed, illustrative embodiments may take other remedial action and thus, the noted remedial actions are illustrative specific embodiments only.

The remedial action may be conditional on the severity of the crash. For example, in some embodiments, the CMM <NUM> may take remedial action only if the crash causes an impact force, as applied to a probe <NUM> or probe head <NUM>, that exceeds a given threshold. Various exemplary thresholds are schematically illustrated in <FIG>. It may not be prudent in some embodiments to take remedial action for a slight bump or contact with an object that causes a slight impact force (e.g., below threshold <NUM> in <FIG>) on a probe <NUM> or probe head <NUM>. For example, if a probe is a tactile probe that requires contact with a workpiece <NUM> in order to measure the workpiece <NUM>, such a level of contact would not be sufficient to cause the sensor <NUM> to react, and would be less than the force threshold <NUM>. Accordingly, the given threshold may be established at a somewhat higher force <NUM>. In this way, for example, the CMM <NUM> may continue executing a measurement operation despite of the slight bump, thereby avoiding the need to re-start or repeat a measurement of a workpiece <NUM>.

The remedial action releases the probe <NUM> from its probe clip <NUM> if the impact force exceeds a release threshold <NUM>. A release threshold may be less than, equal to, or greater than an action threshold <NUM>, but in any case is less than that which would damage the probe <NUM> if the probe <NUM> could not move.

<FIG> schematically illustrates a method of adjusting the distance between an optical probe <NUM> and a workpiece <NUM>, for example as part of a process of measuring the workpiece <NUM>. To help describe this method, <FIG> schematically illustrates a corresponding user interface <NUM>. At step <NUM>, using the CMM controller <NUM>, an operator moves the probe is moved to a position relative to the workpiece <NUM>. At step <NUM>, the CMM <NUM> detects the distance between the probe <NUM> and the workpiece <NUM>, and assesses whether the probe <NUM> is within an acceptable range of distances from the workpiece <NUM>. For example, an acceptable range of distances from the workpiece <NUM> may be specified by a measuring protocol uses to measure a specific workpiece <NUM>.

More specifically, at step <NUM>, the CMM <NUM> or an operator assesses whether the probe <NUM> (or probe head <NUM>) is too far away from the workpiece <NUM>. If so, the CMM <NUM> moves the probe <NUM> (or probe head <NUM>) closer to the workpiece at step <NUM>. Such motion may be performed automatically by the CMM <NUM> under control of the controller <NUM>, thus automating a process otherwise performed by a human operator, or in response to control by an operator. Optionally, the process may then return to step <NUM> to detect, and then assess the distance, again, and repeat steps <NUM> and <NUM> until the probe <NUM> (or probe head <NUM>) is no longer too far from the workpiece <NUM>.

Alternately, or in addition, the CMM <NUM> or an operator assesses whether the probe <NUM> (or probe head <NUM>) is too close to the workpiece <NUM> at step <NUM>. If so, the CMM moves the probe <NUM> (or probe head <NUM>) away from the workpiece at step <NUM>. Such motion may be performed automatically by the CMM <NUM> under control of the controller <NUM>, or in response to control by an operator. Optionally, the process may then return to step <NUM> to detect, and then assess the distance, again, and repeat steps <NUM> and <NUM> until the probe <NUM> (or probe head <NUM>) is no longer too close to the workpiece <NUM>.

In some embodiments, step <NUM> may be performed prior to step <NUM>.

<FIG> schematically illustrates a user interface <NUM> configured to allow the CMM <NUM> to communicate with an operator during the foregoing processes. Such a user interface <NUM> may be disposed on an arm or other portion of a CMM <NUM>, or may be displayed on a computer screen in communication with the CMM <NUM>, to name but a few examples. In operation, if the probe <NUM> is too far from the workpiece <NUM>, the CMM <NUM> illuminates arrow <NUM> to instruct the operator to move the probe closer to the workpiece <NUM>, and if the probe <NUM> is too close to the workpiece <NUM>, the CMM <NUM> illuminates arrow <NUM> to instruct the operator to move the probe away from the workpiece <NUM>. If and when the probe is within an acceptable range of distances from the workpiece <NUM>, the CMM <NUM> illuminates light <NUM> to inform the operator accordingly.

Although the probe head <NUM> and its various features, and the probe clips and their features, as well as the foregoing methods, are described in terms of use with optical probes, they may also be used with non-optical probes, such as tactile probes, etc. For example, a probe head <NUM> supporting a tactile probe (e.g., <NUM>), as known in the art, could be used to detect a crash between a feature of the probe head (e.g., probe platform <NUM>; housing <NUM>) and an object, and to take remedial action accordingly.

Various embodiments of the invention may be implemented in part in any conventional computer programming language. For example, some embodiments may be implemented in a procedural programming language (e.g., " C"), or in an object oriented programming language (e.g., "C++"). Other embodiments of the invention may be implemented as preprogrammed hardware elements (e.g., application specific integrated circuits, FPGAs, and digital signal processors), or other related components.

A computer program product for use with a computer system may include a series of computer instructions fixed either on a tangible medium, such as a non-transient computer readable medium (e.g., a diskette, CD-ROM, ROM, FLASH memory, or fixed disk). The series of computer instructions can embody part of the functionality previously described herein with respect to the system.

Those skilled in the art should appreciate that such computer instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Furthermore, such instructions may be stored in any memory device, such as semiconductor, magnetic, optical or other memory devices, and may be transmitted using any communications technology, such as optical, infrared, microwave, or other transmission technologies.

Among other ways, such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the network (e.g., the Internet or World Wide Web). Of course, some embodiments of the invention may be implemented as a combination of both software (e.g., a computer program product) and hardware. Still other embodiments of the invention are implemented as entirely hardware.

Claim 1:
A probe clip for securing an optical probe to a coordinate measuring machine having a probe platform configured to support at least one probe clip, the probe clip comprising:
• a base (<NUM>, <NUM>) configured to removably couple to the probe platform (<NUM>);
• a probe seat (<NUM>) configured to removably secure the optical probe to the probe clip;
• a movable joint (<NUM>) for movably coupling the probe seat (<NUM>) to the base (<NUM>, <NUM>) and configured to allow the probe seat (<NUM>) to be controllably movable relative to the base (<NUM>, <NUM>),
wherein the probe seat (<NUM>) is configured to release the probe in the event of an impact between the probe and a foreign body in which the impact imposes on the probe an impact force above a given threshold force, the given threshold force being less than a force that would damage the probe, wherein the probe seat (<NUM>) is configured to retain the probe at an impact force less than or equal to the given threshold force.