System for loading workpieces into a coordinate positioning machine

Abstract

A system (20) is provided for loading a workpiece (9) into the working volume (11) of a coordinate positioning machine (10). The loading system (20) comprises a supporting member (30) on which the workpiece (9) is supportable and which is moveable relative to the machine (10) via a plurality of guided bearing members (31, 32, 33) along the three guides (41, 42, 43) respectively. The supporting member (30) is movable between a first position in which a workpiece (9) supported on the supporting member (30) is located at least partially outside the working volume (11) and a second position in which the workpiece (9) is located inside the working volume (11). The bearing members (31, 32, 33) form a kinematic coupling in the second position by engaging with corresponding coupling features (45, 46, 47) associated respectively with the three guides (41, 42, 43), and / or the bearing members (31, 32, 33) are in a drawer style configuration and / or are arranged to cantilever the supporting member (30) when in the first position.

Description

[0001] System for Loading Workpieces into a Coordinate Positioning Machine

[0002] The present invention relates to a system for loading a workpiece (or the like) into the working volume of a coordinate positioning machine. Coordinate positioning machines include, for example, coordinate measuring machines (CMMs) and machine tools.

[0003] Figure 1 of the accompanying drawings shows a known type of coordinate measuring machine 1, having three linear axes x, y and z that are arranged orthogonally to one another in series, with the z axis being aligned with gravity g. A measurement probe 3 is mounted to a vertical column 8 which is slidable in the z direction within a carriage 2; this relative movement defines the z axis. The carriage 2 is itself supported on a horizontal beam 7 and is slidable in the y direction along the beam 7; this relative movement defines the y axis. In turn, the beam 7 is slidable in the x direction on a pair of rails 6; this relative movement defines the x axis. A computer controller 5 operates to drive each component (column 8, carriage 2, beam 7) along its corresponding respective axis to the appropriate position to place the measurement probe 3 in the desired position within a working volume 11 of the machine 1, and to move it into a sensing relationship with a workpiece 9 which is supported on a fixed platform 4. The measurement probe 3 may be mounted to the vertical column 8 in a fixed manner as shown, or it may be mounted to the vertical column 8 via an articulated probe head as shown in the inset part of Figure 1, with the articulated probe head providing two rotational axes a, b in addition to the three linear axes x, y, z.

[0004] Each axis x, y, z is driven independently of each other axis by a corresponding respective motor (not shown). Each axis x, y, z is also encoded or sensed independently of each other axis by a corresponding respective sensor, with the outputs from the sensors being used to determine the position of the measurement probe 3 (or whatever tool is attached to the column 8). Each axis is provided with a length-measuring transducer having an encoder scale (depicted schematically in Figure 1 as a series of parallel lines along each axis) paired with a readhead (not shown). To measure relative movement between two parts, the encoder scale is mounted suitably to one part and the readhead is mounted suitably on the other part.

[0005] Another type of coordinate measuring machine 10 is illustrated schematically in Figure 2 of the accompanying drawings. The coordinate measuring machine 10 generally comprises a moveable platform 12 and a fixed platform 14 that are supported and moved relative to each other by a plurality of telescopic or extendable legs 16 provided between them. The fixed platform 12 forms part of a fixed structure of the machine 10. The moveable and fixed platforms 12, 14 can also be referred to as stages (or structures or parts), and the extendable legs 16 can also be referred to as struts (or actuators). Where there are six such extendable legs 16 (as illustrated in Figure 2), the machine 10 is commonly called a hexapod.

[0006] The extendable legs 16 are typically mounted on the platforms 12, 14 via ball joints 18, with each leg 16 either having its own ball joint 18 at one or both ends thereof (as illustrated in Figure 2) or sharing a ball joint 18 with an adjacent leg 16 at one or both ends. Each extendible leg 16 is typically formed as a pair of tubes, with one tube being moved telescopically within the other by a drive mechanism (e.g. linear motor) to provide extension and retraction of the extendible leg 16, as indicated by the arrows within each extendible leg 16 and as described in more detail in WO 2017 / 174966.

[0007] Various relative positions between the moveable platform 12 and the fixed platform 14 can be achieved by extending the legs 16 by differing amounts. The relative position at any instant is monitored by a plurality of length-measuring transducers 17, with one such transducer for each extendable leg 16. Each lengthmeasuring transducer 17 may comprise an encoder scale paired with a readhead, with the encoder scale being mounted suitably to one of the pair of telescopic tubes and the readhead mounted suitably on the other. Extension of the leg 16 thus causes the encoder scale to move past the readhead thereby allowing the length of the extendible leg 16 to be measured (or derived from measurements). A computer controller 15 operates to set the length of each extendible leg 16 to provide the required relative movement between the platforms 12, 14. By having six such length-measuring transducers 17, the relative position can be measured in six corresponding respective degrees of freedom (three translational degrees of freedom and three rotational degrees of freedom).

[0008] A workpiece 9 is mounted on the lower (fixed) platform 14 and a measurement probe 13 is mounted on the upper (moveable) platform 12. A working volume (or operating volume) 11 is defined between the upper (moveable) platform 12 and the lower (fixed) platform 14, with the measurement probe 13 being positioned (i.e. moved to a desired position) in the working volume 11 by operation of the extendible legs 16. The arrangement of Figure 2 can be referred to as a “bottom- up” arrangement because the extendible legs 16 extend up from the fixed platform 14 to the moveable platform 12. Alternatively, with a “top-down” arrangement the extendible legs 16 extend down from the fixed structure 14 to the moveable platform 12, with the measurement probe 13 mounted to a lower surface of the moveable platform 12 and a workpiece mounted to another part of the fixed structure 14 below that. These types of arrangement are discussed in more detail in WO 2019 / 073246 and WO 2021 / 074625.

[0009] A measurement probe 13 is just one example of an operating tool that can be mounted on the moveable platform 12 to enable an operation to be performed on the workpiece 9. Depending on the intended application, the operating tool can be adapted for measuring, probing or scanning in the case of a coordinate measuring machine, or machining or drilling in the case of a machine tool. It is also possible to mount the workpiece 9 on the moveable platform 12 and the measurement probe 13 (or other operating tool) on the fixed platform 14.

[0010] The coordinate measuring machine 1 of Figure 1 can be referred to as a Cartesian coordinate measuring machine because it has three linear axes x, y and z that are arranged orthogonally to one another. On the other hand, the coordinate measuring machine 10 of Figure 2 can be referred to as a non-Cartesian coordinate measuring machine because, in contrast to a Cartesian machine such as is illustrated in Figure 1, its axes are not arranged orthogonally according to a Cartesian coordinate system. The coordinate measuring machine 10 of Figure 2 can also be referred to as a “parallel kinematic” coordinate measuring machine, because its axes of movement are arranged in parallel. This is to be contrasted with the coordinate measuring machine 1 of Figure 1, which can be referred to as a “serial kinematic” coordinate measuring machine because its axes of movement are arranged instead in series. Another type of serial kinematic machine is an inspection robot or a manual articulating arm, with multiple articulating arm members connected in series by multiple rotary joints.

[0011] Referring to the coordinate measuring machine 10 shown in Figure 2, access into the working volume 11 of the machine 10 is between adjacent legs 16 of the hexapod arrangement. The present applicant has appreciated that, since these adjacent legs 16 converge generally at the top platform 12 to create a generally triangular opening, access into the working volume 11 is accordingly rather restricted. This can make it problematic to load and mount a workpiece 9 onto the fixed platform 14, because it is necessary to reach laterally into a restricted space through a restricted opening. The access can be even more difficult than is depicted schematically in Figure 2 if the machine 10 is surrounded by a protective casing or enclosure. This problem applies similarly to the coordinate measuring machine 1 of Figure 1, since although the orthogonal nature of the axes of such a machine 1 means that access into the working volume 11 is generally more open than for the machine 10 of Figure 2, the lateral extent of the fixed platform 4 and the vertical restriction created by the overhead horizontal beam 7 can still make it problematic to load and fixture a workpiece 9 in the desired location on the fixed platform 4.

[0012] It is therefore desirable to provide improved access, or an improved system, for the loading of workpieces and the like into the working volume of a coordinate positioning machine such as those depicted in Figures 1 and 2. According to a first aspect of the present invention, there is provided a system for loading a workpiece into the working volume of a coordinate positioning machine, the system comprising a supporting member on which the workpiece is supportable and which is moveable relative to the machine via a plurality of guided bearing members between a first position in which a workpiece supported on the supporting member is located at least partially outside the working volume and a second position in which the workpiece is located inside the working volume. When in the second position, the bearing members form a coupling which constrains relative movement between the supporting member and the machine in six degrees of freedom (without over constraint). In other words, the bearing members can be said to provide exact constraint to relative movement between the supporting member and the machine in six degrees of freedom.

[0013] By forming a coupling which provides exact constraint in six degrees of freedom between the supporting member and the machine when in the second position, without over constraint, a very stable and repeatable stop position is defined for the supporting member and the workpiece supported thereon. The concept of exact constraint and relative movement in six degrees of freedom is discussed in more detail below. Therefore, not only does a loading system embodying the present invention overcome the above-mentioned problem by facilitating the loading of a workpiece into the working volume of the machine via the moveable supporting member, it also enables the supporting member to be moved into and out of the machine multiple times, knowing that each time it reaches the second position it will be in the same position and orientation relative to the machine as before. Furthermore, because the repeatable coupling is formed by the bearing members themselves, a very simple yet effective loading system is thereby provided.

[0014] According to a second aspect of the present invention, there is provided a system for loading a workpiece into the working volume of a coordinate positioning machine, the system comprising a supporting member on which the workpiece is supportable and which is moveable relative to the machine via at least three guided bearing members between a first position in which a workpiece supported on the supporting member is located at least partially outside the working volume and a second position in which the workpiece is located inside the working volume, wherein the bearing members are in a drawer style configuration and / or are arranged to cantilever (or to provide cantilever support for) the supporting member when in the first position.

[0015] A drawer style mechanism benefits from being relatively cheap and robust. It also benefits from providing an overhang or cantilever when in the first (pulled out) position. By using bearing members which are arranged to cantilever the supporting member when in the first (pulled out) position, there is no need for a fixed base member which would remain projecting outwardly from the machine even when the supporting member is in the second (pushed in) position, thereby providing a compact form of machine. This has not previously been proposed in the context of loading workpieces into a coordinate positioning machine.

[0016] The features of the second aspect of the present invention can be used independently of or in combination with the features of the first aspect of the present invention. Accordingly, for the second aspect of the present invention, the bearing members may in the second position form a coupling which constrains relative movement between the supporting member and the machine in six degrees of freedom (without over constraint), which is a particular feature of the first aspect of the present invention. And, for the first aspect of the present invention, the bearing members may be in a drawer style configuration and / or arranged to cantilever the supporting member when in the first position, which is a particular feature of the second aspect of the present invention.

[0017] Each bearing member may be fixed to one of the supporting member and the machine and may be arranged to move along a corresponding guiding member provided on the other of the supporting member and the machine. The coupling referred to above (i.e. the coupling formed when the supporting member is in the second position) may be formed between the bearing member and the guiding member (or a coupling feature of the guiding member) along which the bearing member is arranged to move. The bearing member can be said to form one half or side of the coupling, with the guiding member (or a coupling feature of the guiding member) forming the other half or side of the coupling.

[0018] The bearing members may between them create three points of contact (or three constraints to relative movement) between the supporting member and the guiding members when not in the second position, thereby constraining relative movement between the supporting member and the machine in three corresponding degrees of freedom and enabling relative movement in the unconstrained degrees of freedom, and in particular laterally into and out of the machine. The phrase “points of contact” is to be interpreted broadly, as discussed further below.

[0019] Each bearing member may create a single point of contact (or constraint) between the supporting member and the corresponding guiding member when not in the second position.

[0020] The guiding member may comprise additional constraints which define a maximum amount of (or limit to) relative movement in the otherwise unconstrained degrees of freedom. The system may be adapted such that any such additional constraints are not effective when the supporting member is in the second position, thereby maintaining the above-mentioned exact constraint in six degrees of freedom to relative movement between the supporting member and the machine when in the second position.

[0021] The bearing members between them may create six points of contact (or constraints) between the supporting member and the guiding member when in the second position, thereby constraining relative movement between the supporting member and the machine in six corresponding degrees of freedom without over constraint (or thereby providing exact constraint to relative movement between the supporting member and the machine in six degrees of freedom).

[0022] Each guiding member may comprise or be associated with a coupling / locating feature which interacts with the corresponding bearing member to create one or more of the six points of contact (or constraints) when in the second position.

[0023] Each coupling / locating feature may interact with the corresponding bearing member to create two of the six points of contact (or constraints) when in the second position.

[0024] The bearing members may form a kinematic coupling between the supporting member and the machine when in the second position, thereby forming or defining a kinematic stop position.

[0025] The bearing members may be arranged to provide support that is distributed widely and / or substantially evenly across the supporting member when in the first position, or at least around a normal support position or area or zone for the workpiece.

[0026] The bearing members may be arranged to provide support that is distributed widely and / or substantially evenly across the supporting member when in the second position, or at least around a normal support position or area or zone for the workpiece.

[0027] The bearing members may be arranged to provide support that is substantially only at one end (or at least in one half) of the supporting member when in the first position, or at least offset from or to one side of a normal support position or area or zone for the workpiece. The supporting member may be cantilevered in this way when in the first position.

[0028] A first set of the bearing members may be fixed to (or mounted on) one of the supporting members and the machine and a second set of the bearing members may be fixed to (or mounted on) the other of the supporting member and the machine. This can be considered to provide a drawer style configuration of bearing members.

[0029] The first set of bearing members may move relative to the second set of bearing members when the supporting member is moved between the first and second positions.

[0030] The first set may not be move completely past (or beyond) the second set when the supporting member is moved from the second position to the first position, so that the supporting member effectively remains interlocked with and / or attached to and / or supported by the machine via the bearing members even when in the first position, for example in the manner of a cantilever.

[0031] The supporting member may protrude or project outwardly from the main body of the machine when in the first position.

[0032] The first set may comprise at least one of the bearing members and the second set may comprise at least two of the other bearing members.

[0033] The first set may be fixed to (or mounted on) the supporting member and the second set may be fixed to (or mounted on) the machine.

[0034] The first set may comprise a single bearing member fixed to the back of the moveable supporting member, while the second set may comprise two bearing members fixed to the front of a base member which is itself attached to or forms part of the machine.

[0035] The system may comprise at least three such bearing members. The system may comprise three such bearing members. One of the three bearing members may be fixed to the supporting member and the other two bearing members may be fixed to the machine. The system may comprise a base member which is fixed or mounted or attached to or which forms part of the machine, with the supporting member being moveable relative to the base member (and therefore also relative to the machine). The system may be mounted to the machine via such a base member, which may also be referred to as a fixed member.

[0036] The system may comprise a magnetic biasing arrangement which tends to hold the supporting member relative to the machine in the second position. The magnetic biasing arrangement may also tend to draw the supporting member into the second position when nearby. A spring-based biasing arrangement may be used instead or as well as a magnetic biasing arrangement.

[0037] The bearing members may be rotatable bearing members such as rollers or wheels or balls.

[0038] The moveable supporting member may be in the form of a plate or platform or tray. The base member may be in the form of a plate or platform or tray.

[0039] The supporting member may comprise a handle to assist in manual movement of the supporting member between the first and second positions.

[0040] The coordinate positioning machine may be a non-Cartesian coordinate positioning machine.

[0041] The coordinate positioning machine may be a parallel kinematic coordinate positioning machine.

[0042] The coordinate positioning machine may be a hexapod coordinate positioning machine.

[0043] The coordinate positioning machine may be a coordinate measuring machine. According to a third aspect of the present invention, there is provided a coordinate positioning machine comprising a system according to the first or second aspect of the present invention.

[0044] According to a fourth aspect of the present invention, there is provided a facility comprising a plurality of coordinate positioning machines and a system according to the first or second aspect of the present invention for moving the supporting member (and any workpiece supported thereon) between a corresponding plurality of second positions. In each of the plurality of second positions the workpiece may be located inside the working volume of a corresponding one of the machines. In each of the plurality of second positions the bearing members may form a coupling which constrains relative movement between the supporting member and the machine in six degrees of freedom (without over constraint). The facility may be a production or manufacturing facility.

[0045] Reference will now be made, by way of example, to the accompanying drawings, in which:

[0046] Figure 1, discussed hereinbefore, is a schematic illustration of a Cartesian coordinate positioning machine;

[0047] Figure 2, discussed hereinbefore, is a schematic illustration of a non-Cartesian coordinate positioning machine;

[0048] Figure 3 is a schematic illustration of a system embodying the present invention for loading a workpiece into the working volume of the non-Cartesian coordinate positioning machine of Figure 2;

[0049] Figure 4 is a top view of a loading system embodying the present invention when in the first position, showing three points of contact which constrain movement in three degrees of freedom; Figure 5 is a top view of the loading system of Figure 4 when in a position in between the first and second positions, having been moved via the primary unconstrained degree of freedom;

[0050] Figure 6 is a top view of the loading system in the intermediate position of Figure 5, but with some additional motion via the secondary unconstrained degrees of freedom;

[0051] Figure 7 is a top view of the loading system of Figure 4 when in the second (docked) position, with the supporting member in a kinematically-defined position and orientation relative to the machine;

[0052] Figures 8, 9 and 10 show side views corresponding respectively to the top views of Figures 4, 5 and 7;

[0053] Figure 11 is a top view of a more compact loading system embodying the present invention, which allows the base member to be contained entirely within the machine;

[0054] Figure 12 is a top view of the loading system of Figure 11 when in the second (docked) position;

[0055] Figures 13, 14 and 15 show side views of the Figure 11 embodiment, corresponding generally to Figures 8, 9 and 10 of the previous embodiment;

[0056] Figure 16 shows an additional constraint member used in the Figure 11 embodiment to limit tilting of the supporting member;

[0057] Figure 17 is a schematic view of a machine and loading system similar to that shown in Figure 3, though with the machine having a casing around the working parts; Figure 18 is a less schematic view of a machine having a loading system embodying the present invention, corresponding generally to the more schematic machine view shown in Figure 17;

[0058] Figure 19 shows a more detailed view of the moveable supporting member from Figure 18, when in the second position;

[0059] Figure 20 shows a more detailed view of the moveable supporting member from Figure 18, when in the first position;

[0060] Figure 21 is a close-up view of the rear-most coupling feature, viewed from above and from the back of the loading system;

[0061] Figure 22 a close-up view of the bearing member engaged with the corresponding coupling feature when in the second position;

[0062] Figure 23 is a view from the front and from below the loading system, with the supporting member in the second position;

[0063] Figure 24 is a plan view of the underside of the supporting member in the same position as Figure 23, also showing the front-most bearing members;

[0064] Figure 25 shows one of the angled coupling features in more detail, viewed from below; and

[0065] Figure 26 shows detail of the other of the angled coupling features, viewed from above.

[0066] Figure 3 is a schematic illustration of a system 20 embodying the present invention for loading a workpiece 9 into the working volume of the non-Cartesian coordinate positioning machine 10 described above with reference to Figure 2. The loading system 20 comprises a supporting member 30 on which the workpiece 9 is supportable and which is moveable laterally relative a base member 40 which is mounted to the fixed platform 14 within the working volume 11 of the machine 10. The supporting member 30 is moveable laterally between a first position in which the workpiece 9 on the supporting member 30 is located at least partially outside the working volume 11 (as shown in Figure 3) and a second position in which the workpiece 9 is located inside the working volume 11. This lateral movement from the first position to the second position is depicted in Figure 3 by the block arrow at the back of the supporting member 30. In this respect, the terms back and front used herein are relative to the normal position of an operator of the machine, with the front being closest to the operator and the back being furthest from the operator.

[0067] Figure 4 shows a view of the loading system 20 from above the moveable supporting member 30, with features of the fixed base member 40 in dotted outline and features of the moveable supporting member 30 in solid outline. Figure 4 shows that the supporting member 30 is moveable relative to the base member 40 via three guided bearing members (e.g. rollers) 31, 32, 33. In this embodiment, all three bearing members 31, 32, 33 are attached to the moveable supporting member 30, and move along three corresponding guides (or tracks or guiding members) 41, 42, 43 on the base member 40. A handle 34 on the front side of the moveable supporting member 30 is provided to assist in manually pushing the supporting member 30 laterally into the machine 10, and pulling it laterally back out again.

[0068] In this embodiment, therefore, the base member 40 would extend outwardly from machine 10 (unlike what is shown schematically in Figure 3, where the base member 40 is contained entirely within the machine 10). A preferred alternative (and more compact) arrangement, which is more similar to that depicted in Figure 3, will be described further below with reference to Figures 11 to 16, but the arrangement shown in Figures 4 to 10 is somewhat simpler in concept because all three bearing members 31, 32, 33 are attached to the moveable supporting member 30, which itself simply moves along the three corresponding guides 41, 42, 43 on the base member 40.

[0069] Figure 4 shows the supporting member 30 in the above-mentioned first position, in which a workpiece 9 on the supporting member 30 would be located at least partially outside the working volume 11. Each bearing member 31, 32, 33 is in the form of a roller, with a side profile of the first bearing member 31 being illustrated in the inset part of Figure 4 (the other bearing members 32, 33 having a similar side profile). The bearing member 31 has a curved outer surface as depicted, such that a single point-like contact ci is created between the bearing member 31 and the corresponding guide 41 on the base member 40, which will itself have a substantially flat or planar profile. Point-like contacts C2 and C3 are likewise made between the other two bearing members 32, 33 and their corresponding respective guides 42, 43. The bearing members 31, 32, 33 could be formed of hardened steel, with a hardened steel material also used to form the guides 41, 42, 43, and because of this the three contacts ci, C2 and C3 can be assumed to be point contacts even under load. In practice, these will not be points in a pure mathematical sense, but rather will form contact over a small area, but they can nonetheless be approximated as points for the purpose of this discussion; the term “point of contact” in this context is to be interpreted accordingly herein.

[0070] These three points of contact ci, C2 and C3 provide three corresponding constraints to relative motion between the moveable supporting member 30 and the base member 40. Accordingly, the supporting member 30 is constrained relative to the base member 40 in three corresponding degrees of freedom, these being rotation about orthogonal axes in the plane of the supporting member 30 (the pitch and roll axes, i.e. pitch and roll rotational motions are constrained) and linear motion along an axis perpendicular to that plane (the yaw axis, i.e. linear motion along that axis is constrained). Conversely, the supporting member 30 has three remaining degrees of freedom relative to the base member 40, these being rotation about the perpendicular axis (the yaw axis, i.e. yaw rotational motion is not constrained) and lateral motion along the orthogonal axes (the pitch and roll axes, i.e. linear motion along those axes is not constrained).

[0071] One of these available degrees of freedom is a primary degree of freedom which provides the main forward and backward movement of the supporting member 30 along the guides 41, 42, 43 into and out of the machine 10. Figure 5 shows the supporting member 30 having been moved part way along the base member 40 (and into the machine 10) by pushing laterally on the handle 34, thereby making use of the primary degree of freedom. However, the other two available degrees of freedom enable secondary movements of the supporting member 30 relative to the base member 40, these being sideways lateral movement and rotation about the above-mentioned perpendicular axis (i.e. yaw). Accordingly, it can be seen that the bearing members 31, 32, 33 are not tightly constrained within in their corresponding respective guides 41, 42, 43. This secondary movement is shown in Figure 6.

[0072] Whilst being generally planar in nature, the guides 41, 42, 43 preferably have some additional constraints (boundary constraints) which act to limit the secondary (undesirable) relative movements. For example, the guides 41, 42, 43 may be provided with side walls against which the bearing members 31, 32, 33 will come into contact as depicted in Figure 6, thereby limiting these undesirable movements. However, these additional constraints do not provide any additional points of contact during normal forward / backward motion, so that there are normally only three points of contact ci, C2 and C3 and three corresponding constraints to relative motion (with three constrained degrees of freedom and three unconstrained degrees of freedom).

[0073] Figure 7 shows what happens when the supporting member 30 reaches the above- mentioned second position (or stop position). In the second position the bearing members 31, 32, 33 form a coupling which constrains relative movement between the supporting member 30 and the base member 40 in all six degrees of freedom. Since the base member 40 is itself fixed relative to the machine 10, this also constrains relative movement between the supporting member 30 and the machine 10 in all six degrees of freedom. This is achieved by providing three coupling features (or coupling members) 45, 46, 47 along the three guides 41, 42, 43 respectively, into which coupling features 45, 46, 47 the three bearing members

[0074] 31, 32, 33 respectively locate when in the second position. Each of the coupling features 45, 46, 47 forms a v-groove shape internally, with the v-groove of coupling feature 45 being aligned with its corresponding guide 41, and with the v- grooves of coupling features 46, 47 being angled inwardly with respect to their corresponding respective guides 42, 43. These coupling features 45, 46, 47 are preferably recessed slightly into their respective guides 41, 42, 43 so that, by action of gravity, the three bearing members 31, 32, 33 naturally drop down into them when in the second (stop) position.

[0075] As shown in Figure 7, the curved outer surface of the three bearing members 31,

[0076] 32, 33 and the coupling features 45, 46, 47 are mutually adapted and arranged such that six points of contact cn, C12 (between bearing member 31 and coupling feature 45), C21, C22 (between bearing member 32 and coupling feature 46), and C31, C32 (between bearing member 33 and coupling feature 47) are created between the supporting member 30 and the base member 40 when in the second (stop) position. These six points of contact cn, C12, C21, C22, C31, and C32 thereby constrain relative movement between the supporting member 30 and the machine 10 in six corresponding degrees of freedom. Again, as noted above, each of the points of contact will in practice be a small contact area that approximates a point contact.

[0077] Because of the alignment of the coupling feature 45 with the guide 41 (and bearing member 31), the two points of contact cn, C12 between bearing member 31 and coupling feature 45 are disposed centrally on either side of the bearing member 31, with the bisector between them being aligned with the guide 41. On the other hand, because the coupling feature 46 is angled inwardly with respect to its corresponding guide 42 (and bearing member 32), the two points of contact C21, C22 between bearing member 32 and coupling feature 46 are pushed forward and backward respectively, such that the bisector between them is angled inwardly with respect to the guide 42. Similarly, because the coupling feature 47 is angled inwardly with respect to its corresponding guide 43 (and bearing member 33), the two points of contact C31, C32 between bearing member 33 and coupling feature 47 are pushed backward and forward respectively, such that the bisector between them is angled inwardly with respect to the guide 43.

[0078] Accordingly, when in the second position, the bearing members 31, 32, 33 form a kinematic form of coupling between the supporting member 30 and the machine 10, thereby forming a kinematically-defined stop position for the supporting member 30. The kinematic coupling is a “2-2-2” configuration of kinematic coupling, with each of the three coupling locations defining two of the six points of contact (constraints) overall. What is meant by a kinematic coupling in this context will now be explained.

[0079] In the context of locating a first body relative to a second body, kinematic design considerations are met by constraining the degrees of freedom of motion of the first body relative to the second body using the minimum number of constraints (also referred to as exact constraint). Where there is over constraint in a coupling between the two bodies, i.e. where the coupling provides more than the minimum number of constraints by providing at least one redundant constraint, it is not possible to determine with any certainty which combination of constraints will determine the actual position of the first body relative to the second body. Accordingly, the position of the first body relative to the second body is not repeatable, because it is not known at which of the several possible positions the first body will come to rest relative to the second body when they come together again.

[0080] Furthermore, where there is over constraint, the first body does not assume a stable position relative to the second body because it may move between two or more of the different possible positions when a force is applied. An example of this is a four-legged table which will often rock between two different positions when placed on a flat surface. This is because the minimum number of constraints in this context is three, to constrain relative motion in three corresponding degrees of freedom (two rotational degrees of freedom and one translational degree of freedom), whereas a four-legged table has four constraints (created by contact between each of the four legs and the flat surface), such that the coupling between the table and the flat surface is over constrained.

[0081] In general, a single constraint is required for each degree of freedom to be constrained, and a single point contact between two bodies creates a single constraint. Therefore, to constrain a first body relative to a second body in all six degrees of freedom, the coupling between them would need to define six points of contact that are mutually arranged to constrain the two bodies relative to one another in six corresponding degrees of freedom without any redundancy. It will be understood that these points of contact need not be (and in practice would not be) mathematical points in the pure sense. Instead, in practice, each of these would typically be a small area that approximates a point. However, even though each point of contact may not be pure in a mathematical sense, the coupling can still be referred to as a kinematic coupling because it can still be considered to follow kinematic design principles. The term kinematic, as used herein in the context of a coupling between two bodies, is to be interpreted accordingly as meaning kinematic or at least pseudo-kinematic, and similarly for like terms such as kinematically.

[0082] In view of the above, it will be understood that use of a kinematic coupling between a first body and a second body provides a kinematically-defined position for the first body relative to the second body that is unique, discrete, repeatable, predictable and stable, at least in respect of the degrees of freedom that are constrained by the coupling (i.e. ignoring any unconstrained degrees of freedom). Unless otherwise stated, a kinematic coupling as referred to herein is to be understood as providing relative constraint in all six degrees of freedom, with a kinematically-defined position being interpreted likewise as relating to a relative position defined kinematically in all six degrees of freedom. A kinematically- defined position can also be referred to in short as a kinematic location. Because of its reliance on the principle of exact constraint, a kinematic coupling between two bodies is also by its nature readily couplable and decouplable. This is because, in order to prevent the two bodies from coming away from the constraints that define their relative position, it would be necessary to provide an additional (and opposing) constraint, such as a clamp, and the additional constraint would itself result in over constraint and would therefore turn it from a kinematic coupling into a non-kinematic coupling. That said, a kinematic coupling does typically require some form of nesting force (or biasing force) to hold the coupled bodies together, but without creating an additional constraint. In this respect, a theoretical constraint is not just a contact point alone, but also includes a corresponding nesting force that maintains the contact. The nesting force is a force vector that goes through the contact point normal to the surfaces of contact, but these can be vectorially combined into a single force. For example, a gravitational or magnetic force can be used as a nesting force.

[0083] By way of further background, these concepts are explored further in: (a) “Mechanical Design of Laboratory Apparatus” by H. J. J. Braddick, Chapman & Hall, London, 1960, pages 11-30; (b) “Exact constraint” by James G. Skakoon, Mechanical Engineering, September 2009; (c) “Kinematic Couplings: A Review of Design Principles and Applications” by Alexander Slocum, International Journal of Machine Tools and Manufacture 50.4 (2010): 310-327; and (d) “Principles and Techniques for Designing Precision Machines” by Layton C. Hale, Ph.D. thesis, Massachusetts Institute of Technology, February 1999.

[0084] In the context of an embodiment of the present invention, by forming a kinematic coupling between the supporting member 30 and the machine 10 when in the second position, a very stable and repeatable stop position is defined for the supporting member 30 and the supported workpiece 9. The supporting member 30 can be moved into and out of the machine 10 multiple times, knowing that each time it reaches the stop position it will be in precisely the same position and orientation relative to the machine 10. This is highly advantageous, and what is more because the kinematic coupling is formed by the bearing members 31, 32, 33 themselves, a very simple yet effective loading system is thereby provided.

[0085] Referring again to the additional constraints mentioned above with reference to Figure 6, it is to be noted that any such additional constraints do not provide any additional points of contact when the supporting member 30 is in the second position, in particular. In other words, there will be clearance between the bearing members 31, 32, 33 (or any other part of the supporting member 30) and any feature using to create the additional constraints (e.g. side walls to the guides 41, 42, 43) when in the second position, so that there is no additional contact created other than the six points of contact cn, C12, C21, C22, C31, and C32 mentioned above. This avoids creating over constraint and preserves the kinematic nature of the coupling which is created by the bearing members 31, 32, 33 engaging with the coupling features 45, 46, 47 in the second position.

[0086] Figures 8, 9 and 10 show side views corresponding respectively to the plan views of Figures 4, 5 and 7, illustrating clearly how the supporting member 30 (and the supported workpiece 9) is moveable relative to the base member 40 via the plurality of guided bearing members 31, 32, 33 (bearing member 33 is hidden behind bearing member 32 in Figures 8, 9 and 10) between a first position (Figure 8) in which the workpiece 9 supported on the supporting member 30 is located at least partially outside the working volume and a second position (Figure 10) in which the workpiece 9 is located inside the working volume, wherein in the second position the bearing members 31, 32, 33 form a coupling which constrains relative movement between the supporting member 30 and the machine 10 in six degrees of freedom, without over constraint.

[0087] Figures 8 to 10 also show a magnetic biasing arrangement which is provided to help to hold the supporting member 30 relative to the machine 10 (or equivalently the base member 40) in the second position, and also to draw the supporting member 30 into the second position when nearby. The magnetic biasing arrangement comprises a magnetic feature 38 (a permanent magnet or magnetic material) on the supporting member 30 and an opposing magnetic feature 48 on the base member 40 (magnetic material or a permanent magnet).

[0088] The magnetic biasing arrangement is optional, and provides a similar effect to the gravitational effect described above, whereby the bearing members drop down slightly into recessed coupling features 45, 46, 47. This also helps to draw the supporting member 30 into the second position when nearby, and to hold it in that position, because moving away from that position will require a force to lift the supporting member 30 (and workpiece 9) up against the force of gravity. It will Ibe appreciated that the coupling features 45, 46, 47 need not be recessed at all within their respective guides 41, 42, 43, and could in fact be raised up, so that each bearing member 31, 32, 33 is pushed up a ramp and then engages with (and optionally drops down into) its corresponding respective coupling feature 45, 46, 47. A spring-based biasing arrangement may be used instead or as well as a magnetic biasing arrangement. Sprung flexures could also be provided on the underside of the supporting member 30, with the flexures having grooves in them which provide both a downward force and a lateral constraint.

[0089] It will be noted that the inward angling of the coupling features 46, 47 not only serves to form a “2-2-2” kinematic coupling arrangement, resulting in six points of contact and exact constraint in six degrees of freedom when in the second position, but it also acts to apply a twist to the bearings of the rotatable bearing members 32, 33 (which may be rollers or wheels or balls), and this helps to prevent further “play” (and corresponding movement of the supporting member 30) when in second (seated) position.

[0090] As noted above, in the embodiment of Figure 4, the base member 40 would extend outwardly from the machine 10, unlike what is shown schematically in Figure 3 where the base member 40 is contained entirely within the machine 10. Figure 11 shows a more compact arrangement which allows the base member 40 to be contained entirely within the machine 10, with only the supporting member 30 extending outwardly from the base member 40 when in the first (extended) position. In the embodiment of Figure 11, the front-most bearing members 32, 33 are attached to the fixed base member 40 rather than the supporting member 30, with rear-most bearing member 31 remaining fixed to the moveable supporting member 30. Correspondingly, the guides 42, 43 and the front-most coupling features 46, 47 are now on the underside of the moveable supporting member 30 rather than on the top of the fixed base member 40. Again, features of the moveable supporting member 30 are shown in solid outline in Figure 11, while features of the fixed base member 40 are shown in dotted outline.

[0091] Figure 12 shows the moveable supporting member 30 pushed into the second (seated or stop) position, exhibiting a more compact footprint overall compared to the equivalent position shown in Figure 7. Despite the different arrangement, a kinematic coupling is formed between the bearing members 31, 32, 33 and their corresponding coupling features 45, 46, 47 in an entirely equivalent way, so a further description of this is not required. Figures 13, 14 and 15 show side views of this more compact arrangement, and correspond generally to Figures 8, 9 and 10 of the previous embodiment.

[0092] With this embodiment, the lateral separation between the rear-most bearing member 31 and the front-most bearing members 32, 33 is no longer constant, as is most apparent from the sequence shown in Figures 13, 14 and 15. When in the first (fully extended) position shown in Figure 13, there is a danger that the moveable supporting member 30 will tilt by pivoting around the front-most bearing members 32, 33, particularly when loaded with a workpiece 9. To prevent this, the middle guide 41 can provided with an upper constraint member 49 as shown in Figure 16, which will limit the amount of tilting and prevent the supporting member 30 and workpiece 9 from coming away from the machine 10 completely.

[0093] The arrangement of bearing members 31, 32, 33 (and corresponding respective guides 41, 42 and 43) in the embodiment of Figures 11 to 16 can be referred to as a drawer style configuration of bearing members, because it resembles the type of bearing configuration that is used for slidably supporting a drawer in furniture that is commonly inside used the home or office, for example for kitchen drawers. For the known type of draw style bearing arrangement, there would typically be two bearings on either side (two at the back of the moving part and two at the front of the fixed part, making a total of four).

[0094] It will also be noted that the bearing members 31, 32, 33 are arranged to provide support that is substantially only at one end (or at least in one half) of the supporting member 30 when in the first position, or at least offset from or to one side of a normal support position or area for a workpiece 9 that is supported on the supporting member 30. The supporting member 30 is thereby cantilevered by the bearing members 31, 32, 33 when in the first position. On the other hand, when the supporting member 30 is in the second position, the bearing members 31, 32, 33 provide support that is distributed more widely and / or substantially evenly across the supporting member 30, or at least around a normal support position or area or zone for the workpiece 9.

[0095] It would not be obvious to use such a drawer style or cantilever arrangement for loading workpieces into a coordinate positioning machine, because a loading system for use in a coordinate positioning context would ordinarily be considered to require an overhanging support in order to provide a secure and accurate linear bearing, for example more like the embodiment described with reference to Figures 4 to 10.

[0096] A drawer style mechanism benefits from being relatively cheap and robust, as well as from providing an overhang or cantilever without need for an underlying support at the one end (being supported only at the other end). This is a benefit in its own right, not previously proposed in the context of loading workpieces into a coordinate positioning machine. Accordingly, this drawer style or cantilever support arrangement can be used independently of the kinematically-defined stop position described above, and should therefore be considered to relate to a second (and independent) aspect of the present invention. A drawer style or cantilever arrangement is typically over constrained and / or unstable (for example subject to movement or bending), and for a coordinate positioning application such as is described herein, a known and stable end position is beneficial. Hence the kinematic features described above in relation to the first aspect are preferably used in combination with a drawer style bearing or cantilever support arrangement of this second aspect, in order to provide a repeatable and stable resting position for the workpiece even if the moveable support member is over constrained or lacking somewhat in positional stability when not in the rest position.

[0097] It will be understood that although the cantilever or drawer style embodiment described with reference to Figures 11 to 16 (and indeed shown schematically in Figure 3) has a single bearing member 31 at the back of the moveable member 30 and a pair of bearing members 33, 34 at the front of the fixed member 40, this could instead be reversed, with a pair of bearing members at the back of the moveable member 30 and a single bearing member at the front of the fixed member 40. Or, particularly where a known and stable stop position is not required, there could be a pair of bearing members at the back of the moveable member 30 and a pair of bearing members at the front of the fixed member 40, i.e. more like a known bearing arrangement as used in a kitchen drawer. However, even with two pairs of bearing members, it would still be possible to avoid over constraint in the rest position (thereby ensuring exact or kinematic constraint) by ensuring that there are still only six points of contact in this position, for example by ensuring that one of the bearings of one of the pairs does not make any contact with the other side when in the rest position (for example by locating over a void), and with the other bearing of the pair making two points of contact as described above (thereby forming six points of contact over three bearings in a “2-2-2” arrangement), or by ensuring that each bearing of one of the pairs makes a single point of contact (thereby forming six points of contact over four bearings in a “2- 2-1-1” arrangement).

[0098] It will also be understood that although the embodiment described with reference to Figures 4 to 10 has a single bearing member 31 at the back of the moveable member 30 and a pair of bearing members 33, 34 at the front of the moveable member 30, this could instead be reversed, with a pair of bearing members at the back of the moveable member 30 and a single bearing member at the front of the moveable member 30. It is again noted that the terms back and front used herein are relative to the normal position of an operator of the machine, or alternatively relative to the position from which a workpiece is normally loaded into the machine, with the front being closest to this position and the back being furthest from this position; in other words it corresponds to what would be considered to be the front of the machine and what would considered to be the back.

[0099] Furthermore, similar to what is mentioned above for the cantilever or drawer style embodiment, it would also be possible to have two pairs of bearings fixed respectively to the back and front of the moveable supporting member 30, for example moving along side guides 42, 43 with no middle guide 41, though this would provide four points of contact away during movement between the first and second positions (and therefore over constraint, with the risk of rocking), but in the stop position it could still be ensured (via suitably adapted coupling features) that there are still six points of contact to create exact constraint in the rest position as before.

[0100] Figure 17 is a schematic view of a machine 10 and loading system 20 similar to the schematic view of Figure 3. Compared to the machine 10 shown in Figure 3, the machine 10 shown in Figure 17 includes a protective casing or enclosure 50 which surrounds the working parts of the machine 10, e.g. the hexapod arrangement of extendable legs 16 and the moveable and fixed platforms 12, 14. The casing 50 also incorporates one or more viewing windows 52. The controller 15 of Figure 3 has been omitted from Figure 17 purely for simplicity but would in practice be present. It will be apparent from Figure 17 that, because of the casing 50, access into the working volume 11 is even more restricted than is depicted schematically in Figure 3, and this is even more so with the embodiment described below with reference to Figure 18. This more restricted access into the working volume 11 makes the use of a loading system 20 embodying the present invention even more desirable.

[0101] Figures 3 to 17 referred to above are rather schematic in nature, to show clearly the principles underlying an embodiment of the present invention. To illustrate how a loading system embodying the present invention can be incorporated into an actual machine design, a more realistic embodiment of the present invention is shown in Figures 18 to 26. The embodiment shown in these drawings correspond closely to the more compact embodiment shown in schematic form in Figure 3 and Figures 11 to 17, differing in implementation detail but generally having the same principle of operation, with like reference numerals being used for like parts. Therefore, a detailed description of the embodiment shown in Figures 18 to 26 is not required.

[0102] Figure 18 shows the loading system 20 in an extended configuration, i.e. with the moveable supporting member 30 in the first position, extended outward from the machine 10, and with a workpiece 9 being loaded onto the supporting member 30. Figure 19 shows a more detailed view of the moveable supporting member 30 when in the second position, pushed into the machine 10 and docked in the seated or stop position. Figure 20 shows a more detailed view of the moveable supporting member 30 when in the first position, extended outwardly from the machine 10. Figure 20 also shows a damper element 51 on the base member 40 which is used to slow movement of the moveable supporting member 30 as it approaches the second position from the first position, which helps to prevent moveable supporting member 30 from overshooting the second position and crashing into a stop beyond it, and also making it generally easier to locate into the required position even with a relatively uncontrolled push on the handle 34.

[0103] Figure 21 is a close-up view of the rear-most coupling feature 45, viewed from above and from the back of the system 20, from which the form of the v-groove is readily apparent. Figure 21 also shows where on the v-groove the points of contact cn, C12 will be formed between bearing member 31 and coupling feature 45 when docked in the second position. Also apparent from Figure 21 is the upper constraint member 49 as also shown earlier in Figure 16. Figure 22 shows a similar close-up view of the rear-most coupling feature 45, but also shows the moveable supporting member 30 in the second (docked) position with the bearing member 31 engaged with the coupling feature 45 to create two of the six points of contact that define the kinematic coupling described above.

[0104] Figure 23 is a view from the front and from below the system 20, with the supporting member 30 docked in the second position, showing the front-most bearing members 32, 33 that are attached to the fixed base member 40 and engaged into the front-most coupling features 46, 47 on the underside of the moveable supporting member 30 (thereby creating four of the six points of contact that define the kinematic coupling described above), with the guides 42, 43 behind. Figure 24 is a plan view of the underside of the supporting member 30 in the same position as Figure 23, with the base member 40 hidden from view but showing the bearing members 32, 33 attached to the fixed base member 40 engaged into the coupling features 46, 47 on the supporting member 30 at the end of respective guides 42, 43.

[0105] Detail of one of the front-most angled coupling features 46 is shown in Figure 25, viewed from below the supporting member 30. It can be seen from this view how the v-groove is recessed slightly below the level of the corresponding guide 42. Figure 26 is a view of the other of the front-most angled coupling features 47, viewed from above the supporting member 30 but with the support member 30 itself hidden to reveal the coupling feature 47 and how it engages with the bearing member 33 when in the seated position to create an angled pair of contact points with the curved outer surface of the bearing member 33.

[0106] It will also be apparent from Figures 25 and 26 that the guides 42, 43 do not have any lateral constraints (e.g. side walls) to prevent excessive sideways movement and yaw as described with reference to Figure 6. Instead, these movements are restricted by way of lateral constraint members 53 shown in Figure 26 and also in Figures 19, 20, 23 and 24. It will be particularly apparent from Figures 19 and 20 how these lateral constraint members 53 act to prevent excessive sideways movement and yaw by providing a bounded channel through which the sides of the supporting member 30 can pass. Again, it should be noted that there is no contact between the supporting member 30 and these lateral constraint members 53 in particular when the supporting member 30 is in the second (seated) position, to avoid creating over constraint and to preserve the kinematic nature of the coupling which is created by the bearing members 31, 32, 33 engaging with the coupling features 45, 46, 47 in that position.

[0107] Although an embodiment of the present application has been described in the context of a hexapod non-Cartesian coordinate positioning machine, it can also be used for loading workpieces into a Cartesian coordinate measuring machine of a type as shown in Figure 1, or indeed any type of coordinate positioning machine such as a comparator, a scanning machine, a machine tool, a robot, a positioning device (e.g. for optical components), and a prototype manufacturing machine.

[0108] A loading system embodying the present invention is also not limited to moving a workpiece into and out of a single machine. It can also be used as a conveyor or track or transport system for moving a carrier (the supporting member 30) between a series of machines, e.g. measuring machines and / or machine tools, in a factory or facility. The carrier (supporting member 30) would be pushed along a base member 40 that extends from one machine to the next, so that a workpiece 9 can be transferred to each working volume in turn. Where a cantilever or drawer style configuration of bearing members is being used (see Figures 11 to 16), in which at least one of the bearing members is fixed to the machine itself, a set of fixed bearing members could be provided for each machine, with contact being made with the fixed bearing member(s) of the next machine in the series before losing contact with the current machine in the series, so that the moveable supporting member is fully supported at all times; or a set of fixed bearing members could be provided at suitable intervals along the extended base member 40, even between machines, again to ensure that the moveable supporting member is fully supported at all times. It will also be appreciated that, although the supporting member 30 described above relies on being moved manually via the handle 34, the supporting member 30 could also be driven relative to the base member 40 using motors, for example with rotary motors to drive the bearing members 31, 32, 33.

Claims

CLAIMS1. A system for loading a workpiece into the working volume of a coordinate positioning machine, the system comprising a supporting member on which the workpiece is supportable and which is moveable relative to the machine via a plurality of guided bearing members between a first position in which a workpiece supported on the supporting member is located at least partially outside the working volume and a second position in which the workpiece is located inside the working volume, wherein: (a) in the second position the bearing members form a coupling which constrains relative movement between the supporting member and the machine in six degrees of freedom; and / or (b) the bearing members are in a drawer style configuration and / or are arranged to cantilever the supporting member when in the first position.

2. A system as claimed in claim 1, wherein each bearing member is fixed to one of the supporting member and the machine and is arranged to move along a corresponding guiding member provided on the other of the supporting member and the machine.

3. A system as claimed in claim 2, wherein the bearing members create three points of contact between the supporting member and the guiding members when not in the second position, thereby constraining relative movement between the supporting member and the machine in three corresponding degrees of freedom.

4. A system as claimed in claim 3, wherein each bearing member creates a single point of contact between the supporting member and the corresponding guiding member when not in the second position.

5. A system as claimed in claim 2, 3 or 4, wherein the guiding member comprises additional boundary constraints which define a maximum amount of relative movement in the otherwise unconstrained degrees of freedom.

6. A system as claimed in any one of claims 2 to 5, wherein the bearing members create six points of contact between the supporting member and theguiding member when in the second position, thereby constraining relative movement between the supporting member and the machine in six corresponding degrees of freedom.

7. A system as claimed in claim 6, wherein each guiding member comprises a coupling / locating feature which interacts with the corresponding bearing member to create one or more of the six points of contact when in the second position.

8. A system as claimed in claim 7, wherein each coupling / locating feature interacts with the corresponding bearing member to create two of the six points of contact when in the second position.

9. A system as claimed in any preceding claim, wherein the bearing members form a kinematic coupling between the supporting member and the machine when in the second position.

10. A system as claimed in any preceding claim, wherein the bearing members are arranged to provide support that is distributed substantially evenly across the supporting member when in the first position, or at least around a normal support position or area or zone for the workpiece.

11. A system as claimed in any preceding claim, wherein the bearing members are arranged to provide support that is distributed substantially evenly across the supporting member when in the second position, or at least around a normal support position or area or zone for the workpiece.

12. A system as claimed in any preceding claim, wherein the bearing members are arranged to provide support that is substantially only at one end or at least in one half of the supporting member when in the first position, or at least offset from or to one side of a normal support position or area or zone for the workpiece.

13. A system as claimed in any preceding claim, wherein a first set of the bearing members is fixed to one of the supporting members and the machine and asecond set of the bearing members is fixed to the other of the supporting member and the machine.

14. A system as claimed in any preceding claim, comprising three such bearing members.

15. A system as claimed in claim 14, wherein one of the three bearing members is fixed to the supporting member and the other two bearing members are fixed to the machine.

16. A system as claimed in any preceding claim, comprising a magnetic biasing arrangement which tends to hold the supporting member relative to the machine in the second position.

17. A system as claimed in any preceding claim, wherein the bearing members are rotatable bearing members such as rollers or wheels or balls.

18. A system as claimed in any preceding claim, wherein the moveable supporting member is in the form of a plate or platform or tray.

19. A system as claimed in any preceding claim, wherein the supporting member comprises a handle to assist in manual movement of the supporting member between the first and second positions.

20. A system as claimed in any preceding claim, comprising a base member which is fixed or mounted or attached to or which forms part of the machine, with the supporting member being moveable relative to the base member.

21. A system as claimed in any preceding claim, wherein the machine is a hexapod coordinate positioning machine.

22. A system as claimed in any preceding claim, wherein the machine is a coordinate measuring machine.

23. A coordinate positioning machine comprising a system as claimed in anypreceding claim.

24. A facility comprising a plurality of coordinate positioning machines and a system as claimed in any one of claims 1 to 22 for moving the supporting member between a corresponding plurality of second positions.

25. A facility as claimed in claim 24, wherein in each of the second positions the workpiece is located inside the working volume of a corresponding one of the plurality of machines.

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