POSITIONING APPARATUS WITH AN ASSOCIATED TRANSFER MECHANISM

Abstract

An apparatus including an inspection apparatus for inspecting an artefact, and a transfer mechanism for moving a pallet on which an artefact is located relative to the inspection apparatus so as to move the pallet to and from an inspection location, and further including at least one pallet lifter which can be actuated between a retracted and an extended configuration, configured such that when a pallet is at the inspection location the at least one pallet lifter can be actuated to its extended configuration so as to engage with and lift the pallet and thereby decouple the pallet from the transfer mechanism.

Claims

1. An apparatus comprising an inspection apparatus for inspecting an artefact, and a transfer mechanism via which a pallet on which an artefact is located relative to the inspection apparatus can moved to and from an inspection location, and further comprising at least one pallet lifter which can be actuated between a retracted and an extended configuration, configured such that when a pallet is at the inspection location the at least one pallet lifter can be actuated to its extended configuration so as to engage with and lift the pallet and thereby decouple the pallet from the transfer mechanism.

2. An apparatus as claimed in claim 1, in which the transfer mechanism is decoupled from the inspection apparatus.

3. An apparatus as claimed in claim 1, in which the inspection apparatus comprises a movement frame for moving an inspection device relative to a base, and in which the at least one pallet lifter is mounted on the base such that when the at least one pallet lifter engages a pallet, the pallet is connected to ground via the base.

4. An apparatus as claimed in claim 3, in which the transfer mechanism is decoupled from the base.

5. An apparatus as claimed in claim 1, in which the at least one pallet lifter is pneumatically operated.

6. An apparatus as claimed in claim 5, in which the at least one pallet lifter is configured to be actuated into its extended configuration pneumatically, and is configured to be biased into its retracted configuration mechanically.

7. An apparatus as claimed in claim 1, in which the at least one pallet lifter comprises a housing and a member which can be moved between a lowered position and a raised position relative to the housing, in which in the raised position the member extends from the housing more than it does in its lowered position.

8. An apparatus as claimed in claim 6, configured such that the member can be moved to its raised position pneumatically, and comprising at least one spring configured to bias the member toward its lowered position.

9. An apparatus as claimed in claim 7, in which in the raised position a part of the member is biased against a stop.

10. An apparatus as claimed in claim 9, in which the stop is provided on the inside of the housing.

11. An apparatus as claimed in claim 9, in which the stop is provided by a structure which is separate to the housing.

12. An apparatus as claimed in claim 7, in which the location of the member in its raised position is controlled by three discrete engagement locations provided between the member and the stop.

13. An apparatus as claimed in claim 12, in which an engagement location comprises a raised seat on one of the member and the stop, which is configured to be biased against a flat surface provided on the other member.

14. An apparatus as claimed in claim 1, comprising three pallet lifters located so as to interact with and lift a pallet at three separate locations.

15. An apparatus as claimed in claim 14, in which the three pallet lifters are configured to engage with a pallet so as to provide a kinematic joint between the pallet lifters and the pallet.

16. An apparatus as claimed in claim 1, in which at least one of the pallet lifters comprises an electrical connector for providing an electrical connection to an electrical connector on a pallet at the inspection location.

17. An apparatus as claimed in claim 16, in which the electrical connector on the pallet lifter moves with the actuated part of the pallet lifter such that when the pallet lifter is in its extended configuration the electrical connector can connect to a corresponding electrical connector on a pallet at the inspection location, and when the pallet lifter is in its retracted configuration the electrical connector is withdrawn away from a pallet at the inspection location.

18. A pneumatically operable actuator, comprising a housing which houses a piston comprising a piston rod which extends from the housing, and which can be moved between a retracted and an extended position, in which the rest position of the piston at its extended position is controlled by three discrete, engagement locations provided by/between the piston and a stop surface.

19. An apparatus comprising a transfer mechanism for moving a pallet, and at least one pallet lifter which can be actuated between a retracted and an extended configuration, configured such that when the pallet is located over the at least one pallet lifter, the at least one pallet lifter can be actuated to its extended configuration so as to engage with and lift the pallet and thereby decouple the pallet from the transfer mechanism, in which the pallet comprises at least one electrical connector on its underside, and in which at least one of the at least one pallet lifters comprises at least one electrical connector configured such that when the pallet lifter is in its extended configuration the pallet's and the pallet lifter's at least one electrical connectors can contact and electrically connect with each other.

20. An apparatus comprising an inspection apparatus for inspecting an artefact, and a transfer mechanism for moving a pallet on which an artefact is located relative to the inspection apparatus so as to move the pallet to and from an inspection location, in which the transfer mechanism is decoupled from the inspection apparatus.

Description

[0028] Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which:

[0029] FIG. 1 illustrates an apparatus according to the present invention, comprising a Coordinate Measuring Machine (CMM), a transfer mechanism for transferring a pallet to and from an inspection location, and pallet lifters for lifting the pallet from the transfer mechanism at the inspection location;

[0030] FIG. 2 illustrates a close-up view of the pallet lifters of the apparatus of FIG. 1;

[0031] FIGS. 3a and 3b respectively illustrate a pallet lifter in a retracted and extended configuration;

[0032] FIG. 4 illustrates a cross-sectional view of a pallet lifter;

[0033] FIG. 5 illustrates an exploded component view of a pallet lifter;

[0034] FIGS. 6a and 6b respectively illustrate an isometric top view of the piston of a pallet lifter according to a first embodiment of the invention, and a view into the underside of the pallet lifter's neck part with its three landing pads/seats;

[0035] FIGS. 7a and 7b respectively illustrate an isometric top view of the piston of a pallet lifter according to a second embodiment of the invention, and a view into the underside of the pallet lifter's neck part with its three kinematic V features;

[0036] FIGS. 8a and 8b illustrate a pallet lifters according to other embodiments of the invention;

[0037] FIGS. 8c and 8d illustrate parts of the piston rod and shroud of the embodiment of FIG. 8b in isolation;

[0038] FIGS. 9a and 9b illustrate the underside of a pallet according to a first and a second embodiment of the invention; and

[0039] FIGS. 10a and 10b respectively show a pallet lifter with an electrical connector, and the underside of a pallet with a corresponding electrical connector.

[0040] Referring to FIG. 1, there is shown an apparatus 100 according to the present invention, comprising an inspection apparatus, in this embodiment a Coordinate Measuring Machine (CMM) 200, and a transfer mechanism, in this embodiment a conveyor pallet loader 300.

[0041] In the embodiment shown, the CMM 200 comprises a base 202, and a movement system 204 which provides for repeatable and accurate control of the position of an inspection device (in this case a contact probe 206) in three orthogonal degrees of freedom X, Y and Z. In the embodiment shown, the movement system 204 is a gantry-style movement system, and comprises a raised bridge 205 moveable along the Y-axis, a carriage (not visible in FIG. 1 due to covers on the bridge 205) moveable along the bridge 205 along the X-axis, and a quill/z-column 212 carried by the carriage and moveable relative to the carriage (and hence the bridge) along the Z-axis. As will be understood, other types of inspection apparatus can be used, for example the inspection apparatus could comprise a a bridge-type CMM, a cantilever-type CMM, a non-Cartesian positioning system, a parallel kinematic system, or a robot arm.

[0042] In the particular example shown, an articulated head 214 is provided on the lower free end of the quill/z-column 212 for carrying the probe 206. In this case, the articulated head 214 comprises two orthogonal rotational axes. Accordingly, in addition to the three orthogonal linear degrees of freedom X, Y and Z, the probe 206 can be moved about two orthogonal rotational axes (e.g. A and B axes). A machine configured with such an articulated head is commonly known as a 5-axis machine.

[0043] Articulated heads for tools and inspection devices are well known, and for example described in WO2007/093789. As will be understood, an articulated head need not necessarily be provided, and for example the probe 206 could be mounted to the quill/z-column 212 via a fixed head which does not provide any rotational degrees of freedom. Optionally, the probe itself can comprise an articulated member so as to facilitate rotation about at least one axis.

[0044] As shown in FIG. 1, in this embodiment, the conveyor pallet loader 300 comprises a bridge 302 which extends over the base 202 of the CMM 200. The weight of the bridge 302, and of any part(s) thereon, is transferred in full through to ground via legs 304 which support and hold the bridge 302. Accordingly, the conveyor pallet loader's bridge 304 is slightly raised above the base 202 of the CMM 200 such that bridge is not in contact with the conveyor pallet loader. Accordingly, the conveyor pallet loader 300 is decoupled from the CMM 200.

[0045] In this embodiment, the conveyor pallet loader 300 comprises two pallets 310, 312. In use, one or more artefacts can be located on one or more of the two pallets 310, 312. It might be that a calibration artefact 314 is provided on one of the pallets, and a workpiece 316 to be inspected is provided on the other. The pallets 310, 312 can be moved along the bridge 302 of the conveyor pallet loader 300, either manually or automatically. Accordingly, the bridge 302 and/or pallets 310, 312 can comprise bearings, such as mechanical bearings (e.g. roller, ball) and/or air bearings, for facilitating such movement. In the case of the pallets being automatically driven along the bridge 302, one or more actuators, e.g. motors, can be provided. The actuator(s) could be integral with the conveyor pallet loader 300. For example, in the example shown, the bridge 302 of the conveyor pallet loader 300 comprises belts 303 running along the either side of the length of the bridge 302 which can be operated under the control of a motor, for driving the pallets 310, 312 along the bridge 302. Chains (e.g. accumulator chains) could be used instead of the belts 303. Optionally, the actuator(s) could be separate to the conveyor pallet loader 300. For example, an external robot arm could be provided for pushing and/or pulling the pallets 310, 312 along the bridge 302 of the conveyor pallet loader 300.

[0046] The apparatus 100 also comprises three pallet lifters 402. In FIG. 1, the pallet lifters are not visible. Rather, in FIG. 1, there are shown three holes 401 in a cover plate 403, through which the pallet lifters can extend when in their extended configuration. The cover plate 403 has been removed from FIG. 2 so that the pallet lifters can be clearly seen. Referring now to FIG. 2, the pallet lifters 402 are rigidly mounted (e.g. bolted or clamped) to the base 202 of the CMM 200. The pallet lifters 402 can be operated so as change between a retracted/lowered configuration and an extended/raised configuration. The pallet lifters 402 are shown in their retracted/lowered configuration in FIGS. 1 and 2. The pallet lifters 402 are located and configured such that when they are in their retracted configuration, a pallet 310, 312 can be moved by the conveyer pallet loader 300 so as to position the pallet over the pallet lifters 402. In this position, the pallet could be said to be in an “inspection location”, because this is a location where a workpiece on the pallet 310, 312 can be/is to be inspected by the CMM 200. When the pallet is in the inspection location, the pallet lifters 402 can then be actuated into their extended/raised configuration so as to engage and lift the pallet 310, 312 and thereby decouple the pallet 310, 312 from the conveyor pallet loader 300 and provide a firm and stable connection between the pallet 310, 312 and ground (in this case via the base 202 of the CMM 200). The CMM 200 can then be operated so as to inspect a workpiece on the pallet 310, 312. After inspection, the pallet lifters 402 can be actuated to return to their retracted configuration such that the pallet 310, 312 can then moved away from the inspection location by the conveyor pallet loader 300.

[0047] The pallet lifters will now be described in more detail with reference to FIGS. 3 to 7. FIG. 3a shows a pallet lifter in its retracted/lowered configuration, and FIG. 3b shows a pallet lifter in its extended/raised configuration. In the described embodiment, the pallet lifter comprises a pneumatic actuator.

[0048] With reference to FIGS. 3 to 5, the pallet lifter comprises a housing 404 (comprising a main body 406 and a neck 408), and a piston 410 (comprising a piston rod 412 and a piston disc 414). The piston 410 can be moved along an axis A between a lowered/retracted position (shown in FIGS. 3a and 4) and a raised/extended position (shown in FIG. 3b). The piston disc 414 resides in a chamber 420 inside the housing 404, and the piston rod 412 extends, from the piston disc 414, through the neck 408 of the housing 404 and protrudes therefrom through an opening at the free end of the neck 408. A helical spring 428 is compressed between the piston disc 414 and the inside of the free end of the neck 408, thereby urging the piston disc 414 (and hence the piston 410) towards the bottom of the pallet lifter 402/chamber 420 along the axis A. Accordingly, the helical spring 428 biases the piston 410 to its lowered position (and hence the pallet lifter is mechanically biased towards its retracted configuration).

[0049] The piston rod 412 comprises a rounded free end (at its end distal the piston disc 414). In this particular embodiment, the rounded free end is provided by a spherical member 416 set in a recessed seat 418 at the free end of the piston rod 412. In the embodiment described the spherical member 416 comprises a tungsten carbide ball, but other materials such as steel can be used instead. The piston 410, housing 406 and neck 408 are made from aluminium, but other materials such as steel can be used instead.

[0050] An inlet 422 is provided in the main body 406 of the housing, which in this embodiment can be connected to a compressed air source 470 (see FIG. 1), such that compressed air can be pumped into the chamber 420 below the piston disc 414. A vent 430 is provided for allowing air to enter/exit the part of the chamber 420 above the piston disc 414 as the piston moves up and down. A first O-ring seal 424 is provided between the piston disc 414 and the inside of the housing 404 and a second O-ring seal 426 is provided between the free end of the neck 408 and the piston rod 412. The lateral position of the piston 410 (perpendicular to the axis A) is constrained by the housing 404. In this embodiment, the rotation of the piston 404 about the axis A is prevented by way of a pin 432 extending from the piston disc 414 which is a snug fit within, but can slide in and out of, a slot 434 in the bottom of the main body 406 of the housing 404. Although such an anti-rotation device can be advantageous when the rotational position of the piston is important (e.g. because the piston rod has an electrical connector (not shown) at its end which is to engage the pallet in use), such an anti-rotation device is optional.

[0051] The pallet lifter 402 is shown in its retracted/lowered configuration in FIGS. 3a and 4, with the piston 410 retracted into the housing 404 as far as possible (i.e. at its lowermost position). In order to actuate the pallet lifter 402 to its raised configuration, compressed air is pumped into the chamber 420 via the inlet 422. This pushes the piston 410 upwards along the axis A, such that the piston extends/projects further out of the free end of the neck 408 of the housing 404. The piston 410 continues to travel along the axis A until the piston engages a stop provided on the inside of the housing 404. In this embodiment, the location of the piston 410 along the axis A in the extended/raised position is controlled by three discrete, annularly spaced, engagement locations provided between the piston 410 and the stop.

[0052] In particular, as shown in more detail in FIGS. 6a and 6b the top face 440 of the piston disc comprises a flat face/rim that extends annularly around the axis A/the piston rod 412, and the stop comprises three discrete, annularly spaced (around the axis A), protruding flat surfaces (so-called “landing pads” or “landing seats”) 442 provided on the bottom edge of the neck part 408 of the pallet lifter's housing 404. The piston 410 continues to travel along the axis A until the top face 440 of the piston disc 414 engages the three landing pads/seats 442 on the inside of the housing 404.

[0053] The location of the piston 410 along the axis A in the extended/raised position need not be controlled by three discrete, annularly spaced, engagement locations provided between the piston 410 and the stop. For instance, four or more, engagement locations could be provided. Furthermore, the location of the piston 410 along the axis A in the extended/raised position could be provided by the engagement of two annularly extending flat planar rims (e.g. one on the piston disc and one on the housing). However, providing three discrete, annularly spaced (around the axis A), engagement locations provides a single, stable engagement configuration between the piston 410 and the housing 404, thereby significantly reducing the risk of the piston 410 moving, e.g. rocking, between different engagement configurations when it is in its raised/extended position. This can be important because such motion during inspection of an artefact on a pallet supported by the pallet lifters can adversely affect the accuracy of measurements obtained.

[0054] FIG. 7a shows a different embodiment of the pallet lifter. Similar to the above described embodiment, there are three discrete, annularly spaced, engagement locations. However, in this embodiment, they are configured such that the piston 410 is kinematically located with respect to the housing 404 at its extended/raised position. In particular, in this embodiment, three projections 450 (in this case three spherical features, e.g. balls) are provided on the piston disc 414 which are configured to be received in three recesses 452 (in this case V-grooves) when the piston 410 is at its extended/raised position.

[0055] As shown in FIG. 9a, the underside of a pallet 310′ comprises three features 320, each arranged to receive the extended end 416 of a pallet lifter. In the embodiment of FIG. 9a, each feature comprises a V-shaped slot, arranged to provide two points of contact with the end 416 of a pallet lifter, and thereby together provide a kinematic joint/link with the three pallet lifters. In the embodiment of FIG. 9b, a first feature 322 comprises a three-sided pyramidal recess, which provides three points of contact with the end 416 of a first pallet lifter, a second feature 320 comprises a V-shaped slot which provides two points of contact with the end 416 of a second pallet lifter, and the third feature 324 comprises a flat surface which provides one point of contact with the end 416 of a third pallet lifter. Together they provide a kinematic joint/link with the three pallet lifters.

[0056] In order to actuate the pallet lifter 402 to its lowered/retracted configuration, the pressurised air within the chamber 420 below the piston disc 414 can be released (e.g. via a valve in the air supply line, not shown). To avoid a vacuum in the chamber 420 above the piston disc 414, air can enter the chamber via the vent 430. The piston 410 thereby lowers under the influence of gravity and assisted by the helical spring 428.

[0057] In the embodiment described, the pallet lifters are pneumatically operated. In particular, the apparatus comprises a pneumatic system which is operable to use pressured air to actuate the pallet lifters to their raised configuration. Each pallet lifter also comprises a mechanical, helical spring 428 which is configured to bias the pallet lifter towards its retracted configuration, such that the pallet lifter returns to its retracted configuration when the air pressure is reduced.

[0058] Optionally, the pallet lifter can be configured differently to that described. For instance, in an alternative embodiment, a spring device could be used to bias the pallet lifter towards its raised configuration, to assist the pneumatic system. In a different embodiment, the pallet lifter could be configured such that a spring biases the pallet lifter towards its raised position instead of a pneumatic system. In a further embodiment a pneumatic system could be provided for actuating the pallet lifter towards its retracted configuration. However, a spring mechanism in such embodiments would likely need to be very strong and physically big in order to be able to lift the pallet and artefact by itself, thereby increasing the size and cost of the pallet lifter. Accordingly, the configuration described above in connection with FIGS. 1 to 7 is advantageous. Although means other than pneumatics could be used to actuate the pallet lifters (e.g. hydraulics/motors), a pneumatic system is particularly advantageous, for instance due to the simplicity and compactness it can provide.

[0059] In the embodiment described above, the stop is provided by the housing 404 of the pallet lifter 402. In an alternative embodiment, the stop could be provided by a component separate from the housing. For example, as illustrated in FIG. 8a, the stop could be provided by a shroud 500 which sits over the pallet lifter 402. In this embodiment, three features 460 (only two of which are shown in FIG. 8a) are spaced annularly about the piston rod 412, which engage the shroud 500 when the piston is at its raised position, thereby defining/controlling the location of the piston along the axis A. In the embodiment described, the features 460 are cylindrical rods extending radially from the piston rod 412, which engage V-shaped slots (not shown) on the shroud 500, thereby providing a kinematic location between them. FIG. 8b shows a similar configuration in that the stop is provided by a separate component, but differs in that the separate shroud 500′ sits on top of the main body 406 of the pallet lifter 402. In this embodiment, the shroud 500′ is secured to the base 202 via bolts 502. Tightening of the bolts 502 act to clamp the shroud 500′ and pallet lifter 402 to the base 202.

[0060] Also, in this embodiment, it is shown that the pallet lifter's moveable member (in this case the piston rod 412) can comprise multiple parts. In this case, the piston rod comprises a first part 412′ having a threaded socket 413 and a second part 412″ having a threaded pin 415 via which the first 412′ and second 412″ parts can be secured. FIG. 8c shows the second part 412″ in isolation and FIG. 8d shows an underside isometric view of the shroud 500′ of FIG. 8b. As shown, the second part 412″ comprises three radially extending features 460′ for cooperation with three corresponding sockets 504 in the shroud 500′. Each radially extending feature 460′ provides two contact surfaces 462 which engage corresponding contact surfaces 506 on the sockets 504 in the shroud 500′, thereby providing a kinematic link between the piston rod 412 and the shroud 500′. As will be understood, a piston rod comprising multiple parts is equally applicable to the other embodiments described above.

[0061] FIG. 10a shows an advantageous optional addition to a pallet lifter. As shown, an electrical connector 600 is provided which moves with the piston rod. In particular, in this embodiment, the electrical connector is provided on the piston rod, and more particularly, it is clamped onto the end of the piston rod 412. The electrical connector 600 comprises a body 602, a clamping bolt 604 and a plurality of electrical contacts 606. The body 602 is snap fitted over the end of the piston rod 412 and clamped in place by tightening the bolt 604, so that it moves with the piston rod 412. A cable 610 for supplying power and/or carrying signals to/from the electrical contacts is connected to the body 602. The electrical contacts 606 face upward, and are configured such that when the piston rod 412 is extended so as to lift a pallet, the electrical contacts 606 can contact, and electrically connect with, corresponding electrical contacts 608 on the underside of a pallet 310′″ (see FIG. 10b). The electrical contacts/pads on the pallet 310′″ can thereby supply power and/or carry signals to/from one or more electrical components in or on the pallet, e.g.: to allow the transmission of temperature data; to confirm the absence/presence/correct seating of the artefact being inspected on the pallet (via fixture proxy sensors); to control fixture electromechanical clamps; to receive data regarding the part being inspected, etc. As will be understood, preferably there is provided some compliance in the electrical connector 600, its contacts 606 and/or the contacts 608 on the pallet such that they do not impact the location of the pallet on the pallet lifter.

[0062] In the embodiments described above, the pallet 310/312 is held against the pallet lifters 402 solely due to the gravitational pull on the pallet (and workpiece mounted thereon). However, this need not necessarily be the case. For example, other means for biasing the pallet 310/312 against the pallet lifters 402 could be provided so as to increase the force by which the pallet 310/312 is held against the pallet lifters 402. For instance, one or more magnets, and/or a vacuum suction system, could be provided and configured so as to pull the pallet 310/312 onto the pallet lifters 402. Such means could be provided on the pallet lifter 402 (e.g. around the end of the tip of the piston rod), or separately thereto.