Gantry system

Abstract

A gantry system for transporting an object from a first area to a second area comprises two parallel rails and at least one cross-piece supporting a gripper fixture. The cross-piece comprises a cross-piece main body and two opposite coupling portions, each coupling portion being slidably coupled to a respective rail. The system further comprises position detecting means suitable for detecting the position of the object. The cross-piece main body is connected to each of the coupling portions by means of a cross-piece articulated joint, so that the cross-piece main body is rotatable around a rotation axis so as to compensate for a misalignment between an object orientation detected by the position detecting means and a predetermined orientation.

Description

GANTRY SYSTEM

[0001] The present invention relates to a gantry system for transferring an object from a first area to a second area, for example for stacking planar products, like plates for fuel cells.

[0002] Gantry systems according to the preamble of claim 1 are already known. Such gantry systems usually comprise two parallel rails and one or more cross-pieces extending between the two parallel rails. Each cross-piece comprises two opposite coupling portions slidably coupled to respective rails. Gripping means are supported by a respective cross-piece and are configured to pick up an object from the first area and release the object in the second area. Furthermore, the gantry system is provided with position detecting means suitable for detecting the position of the object in the first area and / or during the transportation from the first area to the second area.

[0003] In many applications, such as the above mentioned fuel cells, the objects must be stacked with great precision. Therefore, there is the need to compensate for any misalignment of the position of the object with respect to a predetermined theoretical position.

[0004] Furthermore, there is also an increasing need to reduce the stacking time.

[0005] Since the known gantry systems are configured to move an object along the three orthogonal axes X, Y and Z, any angular misalignment of the position of the object with respect to a predetermined theoretical position needs to be fixed using a specific gripper, such as the gripper applied to Scara robots.

[0006] However, the use of specific grippers increases the complexity of the whole gantry systems, and therefore the risks of faults. In addition, production, installation and maintenance costs are increased.

[0007] One object of the present invention is to provide a gantry system which is suitable for compensating also angular misalignments and which, at the same time, offers all the advantageous features of a gantry system, that is, a simple structure, high precision and working speed, low maintenance.

[0008] Another object of the invention is to provide a gantry system that, in meeting the aforementioned demands, is particularly inexpensive and easy to manufacture and assemble.

[0009] These objects are achieved with a gantry system according to claim 1 and with a method for transferring an object from a first area to a second area according to claim 12. The dependent claims describe preferred embodiments of the invention.

[0010] The features and advantages of the gantry system according to the invention will be apparent from the description given below of preferred embodiments thereof, made by way of a non-limiting examples with reference to the appended drawings, wherein:figure 1 is a schematic overview of the gantry system according to the invention;figure 2 is a schematic top view of the gantry system;figure 3 is a top view of the rails and cross-pieces of the gantry system, showing one of the cross-pieces subjected to an angular displacement;figures 4 and 4a are two perspective views of the rails and cross-pieces of figure 3;figure 5 is a side view of the rails and cross-pieces of figure 3;figure 6 is an enlarged perspective view of one cross-piece;figure 7 is the same view of figure 6, in which a plate of a gripper fixture for supporting the gripping means has been removed;figure 8 is the same view of figure 6, but from the opposite direction so as to better show the length elongation capabilities of the cross-piece;figure 9 is a top view of the gantry system showing, in three steps, the compensation of an offset between the current position of a picked-up object and the nominal position.

[0011] In the description below, all directional references (for example, upper, lower, upward, downward, left, right, towards the left, towards the right, at the top, at the bottom, above, below, vertical, horizontal, clockwise and counterclockwise) are used only for identification purposes in order to help the reader understand the described embodiments and do not create limitations, in particular with regard to the position, orientation or use of the described embodiments.

[0012] Terms related to joining or connection (e.g. fixed, coupled, connected, and the like) should be interpreted broadly and may include intermediate elements between a connection of elements and a relative movement between elements. These terms do not therefore necessarily imply that two elements are directly connected in a fixed relationship with one another.

[0013] In the drawings, reference number 100 globally denotes a gantry system, in particular for stacking planar objects 1. For example, a planar object to be stacked is a fuel cell subcomponent, e.g. coated and / or structured ceramic plates for fuel cells, bipolar plates or MEAs (Membrane Electrode Assembly) or seals or comparable plate-shaped elements. Such plate elements can have a square or rectangular outline.

[0014] In one general embodiment, gantry system 100 is suitable for transporting an object 1, or work piece, from a first area A1 to a second area A2.

[0015] For example, first area A1 is an end portion of a conveyor belt and the second area A2 is the final stacking position.

[0016] In a general embodiment, the gantry system 100 comprises two parallel rails 10. Each rail 10 extends along a longitudinal rail axis Y.

[0017] At least one cross-piece 12 extends mainly along a cross-piece axis X between the two parallel rails 10.

[0018] Rail axis Y and cross-piece axis X define a gantry plane (X, Y).

[0019] Each cross-piece 12 supports at least one gripper fixture 18. Each gripper fixture 18 is configured to hold a gripper - not shown - suitable for picking up an object 1 from the first area A1 and for releasing the object in the second area A2.

[0020] Each cross-piece 12 comprises a cross-piece main body 14 and two opposite coupling portions 16. Each coupling portion 16 is slidably coupled to a respective rail 10.

[0021] In one embodiment shown in the drawings, the gantry system 100 is provided with two cross-pieces 12, each of which picking up a respective object 1 from a respective first area A1. In this case, first areas A1 may be located underneath the opposite ends of the parallel rails 10 and the second area A2 may be located underneath an intermediate portion of the parallel rails 10. The two cross-pieces 12 can work in a synchronized and coordinated manner, for example so as when one cross-piece 12 is picking up an object 1 from the respective first area A1, the other cross-piece 12 is releasing the respective object 1 in the second area A2.

[0022] Gantry system 100 further comprises position detecting means 20 suitable for detecting the position of the object 1 in the first area A1 and / or during the transportation from the first area A1 to the second area A2.

[0023] According to one aspect of the invention, the cross-piece main body 14 is connected to each of the coupling portions 16 by means of a cross-piece articulated joint 22, so that the cross-piece main body 14 is rotatable around a rotation axis perpendicular to gantry plane (X, Y).

[0024] Therefore, if the position detecting means 20 detect a misalignment between an object orientation and a nominal, predetermined orientation, such misalignment can be compensated, that is, annulled.

[0025] In one embodiment, at least one cross-piece articulated joint 22 is a hinge. For example, each coupling portion 16 forms two opposite flanges 162 (e.g. upper and lower flanges) and each end of the main body 14 forms or supports a pivot element which is rotatably coupled to a respective flange 162.

[0026] In one embodiment, the gantry system 100 comprises at least two linear actuators 24. Each linear actuator 24 is operable to displace a respective coupling portion 16 along the respective rail 10.

[0027] In one embodiment, each linear actuator 24 is at least partially housed in a respective rail 10.

[0028] In one embodiment, each linear actuator is a linear motor comprising a track of permanent magnets 242 housed in a respective rail 10 and a coil unit 244 supported by a respective coupling portion 16 of the cross-piece. When the coil unit 244 is energized, the coupling portion 16 translates along the track of permanent magnets 242.

[0029] This linear direct drive can ensure cycle time, alignment reaction time and precision at the same time.

[0030] However, linear actuator 24 could be implemented using other technologies, like ball screw or belt driven actuators.

[0031] In one embodiment, the two linear actuators 24 are independently controllable. This way, the rotation of the cross-piece main body 14 can be obtained by imparting different displacements of the coupling portions 16. In particular, a rotation of the main body 14 can be obtained by displacing the coupling portions in opposite directions.

[0032] Therefore, the cross-piece 12 can be rotated to compensate for angular misalignment without the necessity to provide dedicated angular actuators, but using the same linear actuators 24 which cause the cross-piece 12 to translate along the direction of the rail axis Y.

[0033] In one embodiment, the cross-piece main body 14 comprises at least two main body portions 142, 144. These two main body portions 142, 144 are slidably coupled along the cross-piece axis X so as the length of the main body 14 along the cross-piece axis X can passively change to compensate for a change in the distance between the opposite coupling portions 16 due to a rotation of the main body 14.

[0034] In other words, the main body 14 has a kind of telescopic structure.

[0035] For example, the two main body portions 142, 144 are slidable by means of crossed roller bearings interposed therebetween. This technical solution ensures high stiffness, high reproducibility, precision and alignment throughout the complete stroke of the possible length extension.

[0036] In addition, one of the two body portions 142, 144 may include adjustment elements to enable a further finetuning of alignment and pretension of the crossed roller bearings.

[0037] In one embodiment, each cross-piece 12 is provided with first gripper fixture actuating means 26 suitable for actively displacing the gripper fixture 18 along the cross-piece axis X (Figure 7). Therefore, an offset between the position of the object and the nominal position along the cross-piece axis X can be compensated. For example, such offset can occur due to the rotation of the main body 14 for compensating for an angular misalignment. In other words, in some cases, the object, and therefore the gripper fixture, has to be subjected to a roto-translation to compensate for an angular misalignment.

[0038] In one embodiment, each cross-piece 12 is further provided with second gripper fixture actuating means 28 suitable for displacing the gripper fixture 18 along a gripping means axis Z, for example a vertical axis, orthogonal to the gantry plane (X, Y).

[0039] In one embodiment, the second gripper actuating means 28 is implemented with a coil-magnet unit, in which the magnet keeps the gripper fixture 18 in a raised position and the coil, when energized, causes the gripper fixture 18 to move vertically from a lower position to the raised position. In particular, the second gripper actuating means 28 are configured to implement gravity compensation.

[0040] In one embodiment, the position detecting means 20 includes at least one camera.

[0041] In the example shown in figure 2, when the object 1 has a planar rectangular shape, the position detecting means 20 includes two detecting cameras 20a, 20b for each cross-piece 12. These two cameras 20a, 20b are positioned so as to detect the position of two opposite vertexes of the object 1 when the object is in the first area A1 or in an intermediate position (as in figure 2) between the first area A1 and the second area A2.

[0042] In one embodiment, a further monitoring camera 21 is located above the second area A2 to monitor the stacking of the objects.

[0043] In figure 2, coordinates Y1, Y2, Y3 and Y4 indicate the travel of the coupling portions 16 of each cross-piece 12 along the respective rails 10. Circular arrows represent the possible mechanical rotations (clockwise or counterclockwise) of the main bodies 14 about the respective coupling portions 16.

[0044] In one embodiment, the gantry system comprises a control system 30, 40, 42 operatively connected to the position detecting means 20 and to each cross-piece 12. The control system 30, 40, 42 is configured to receive, from the position detecting means 20, current position data related to the current position of an object, when the object is in the first area A1 or during the transport towards the second area A2, compare such current position data with reference data related to a predetermined nominal position and control the cross-piece 12 so as to annul differences between the current position data and the reference data.

[0045] The control system 30, 40, 42 is operatively connected to the linear actuators 24 and is configured to command the linear actuators 24 to displace the coupling portions 16 so as to cause an angular displacement of the cross-piece main body 14.

[0046] In one embodiment, the control system 30, 40, 42 comprises a vision controller 30, a motion controller 42 and servo drives 40.

[0047] The vision controller 30 is operatively connected to the detecting cameras 20a, 20b and is configured to implement computer vision algorithms to calculate the coordinates of the current position of the object starting from the images captured by the detecting cameras 20a, 20b. Vision controller 30 is further configured to send such coordinates to the motion controller 42.

[0048] The motion controller 42 is configured to calculate the coordinates of the coupling portions 16 based on the coordinates received from the vision controller 30 so as to compensate for any misalignment between the current position of the object 1 and the predetermined nominal position. The updated coordinates of the coupling portion are then transformed by the motion controller 42 in driving commands for the linear actuators 24.

[0049] In one embodiment, the driving commands are sent to servo drives 40. Such servo drives 40 control the positions of linear actuators 24, for example by means of PWM signals.

[0050] In one embodiment, these servo drives 40 use high precision feedback systems, which may be embedded in rails 10. For example, a sensor position tape is housed in each rail 10 and the linear actuators 24 are provided with a reading head operatively coupled to the sensor position tape.

[0051] In use, a gripper is installed on the gripper fixture 18 of each of the cross-pieces 12.

[0052] A cross-pieces 12 is positioned above first area A1 and the gripper is controlled to pick up an object 1 from the first area A1.

[0053] The cross-piece 12 is then driven so as to move along the rails 10 until the object is aligned with the second area A2.

[0054] The gripper is then actuated to release the object in the second area A2.

[0055] Before picking up the object or during the transfer of the object between the first area A1 and the second area A2, the position detecting means 20 detect the current position of the object and the control system compares the detected position with a predetermined nominal position.

[0056] In case of a misalignment in the angular position between the detected position and the predetermined nominal position, the offset is computed, for example by computer vision software, and the main body 14 of the cross-piece 12 is rotated so as to annul the offset before releasing the object in the second area A2.

[0057] In one embodiment disclosed above, where the gantry system 100 comprises at least two linear actuators 24, each of which being independently operable to displace a respective coupling portion 16 along the respective rail 10, the control system recalculates, from the angular offset, final positions of the coupling portions 16 along the respective rails 10 and drives the linear actuators 24 so as to displace the coupling portions 16 to the recalculated final positions.

[0058] In one embodiment, the detection of the current position, the computation of the offset and the update of the final coordinates of the coupling portions 16 are performed while the cross-piece 12 moves along the rails to transfer the object from the first area A1 to the second area A2.

[0059] If the position detecting means 20 detect an offset with respect to the nominal position along rail axis Y (longitudinal offset), the final coordinates Y1, Y2 are recalculated to compensate for the longitudinal offset.

[0060] If the position detecting means 20 detect an offset with respect to the nominal position along cross-piece axis X (transversal offset), the control unit 30 drives the first gripper fixture actuating means 26 to compensate the transversal offset.

[0061] Figure 9 shows an example of angular compensation.

[0062] In step 1, on object 1 with an angular misalignment is picked-up from the first area A1. The cross-piece 12 with the misaligned object 1 starts moving along the rails 10.

[0063] When the cross-piece 12 passes over the detecting cameras 20a, 20b, the angular offset is detected and measured. The control system then compares the detected offset with the nominal position and recalculates the final coordinates of the coupling portions 16 (step 2).

[0064] In step 3, the cross-piece 12 has reached the final position above the second area A1. It can be noted that the coupling portions 16 of the cross-piece 12 have different final Y-coordinates so that the main body 14 forms an angle with respect to the nominal cross-piece axis X, orthogonal to rail axis Y. Thanks to this rotation of the main body 14, the object 1 is perfectly aligned with its nominal position.

[0065] Therefore, the present invention can provide a complete machine system that combines visual inspection, linear motor direct drive system and controller. Using flying trigger library function, it is possible to detect and compensate misalignment on the fly.

[0066] The gantry system is provided with flexible joints that allow rotational compensation of workpieces (e.g. fuel cell subcomponents like MEA and BiPolar plate).

[0067] In some embodiments, actuators and cameras can work together via a digital bus (e.g. Ethercat) to precisely position workpiece inside the machine. For example, each work piece is allowed to enter the machine with an angle deviation of 3°. The gantry system according to invention allows to build a stack of work pieces with an edge deviation within 20 micrometers.

[0068] The control unit is programmed with a dedicated software for directly transforming position deviations received from cameras to servo drives for driving the linear actuators.

[0069] In one embodiment, the second gripper fixture actuating means allow to implement an additional vertical axis to place workpieces in an angled orientation to the drop off location.

[0070] A person skilled in the art may make modifications and adaptations to the embodiments of the gantry system according to the invention, replacing elements with others functionally equivalent so as to satisfy contingent requirements while remaining within the scope of protection of the following claims.

[0071] Each of the characteristics described as belonging to a possible embodiment may be realized independently of the other embodiments described.

Claims

1. Gantry system for transporting an object (1) from a first area (A1) to a second area (A2), the gantry system comprising: - two parallel rails (10), each rail (10) extending along a longitudinal rail axis (Y); - at least one cross-piece (12) extending mainly along a cross-piece axis (X) between the two parallel rails (10), each cross-piece (12) comprising a cross-piece main body (14) and two opposite coupling portions (16), each coupling portion being slidably coupled to a respective rail (10); - at least a gripper fixture (18), each gripper fixture (18) being supported by a respective cross-piece (12) and configured to hold a gripper suitable for picking up an object from the first area and for releasing the object in the second area; - position detecting means (20) suitable for detecting the position of the object in the first area (A1) and / or during the transportation from the first area to the second area; the gantry system being characterized in that the cross-piece main body (14) is connected to each of the coupling portions (16) by means of a cross-piece articulated joint (22), so that the cross-piece main body (14) is rotatable around a rotation axis perpendicular to a gantry plane (X, Y) defined by rails and cross-piece axes (Y, X) so as to compensate a misalignment between an object orientation detected by the position detecting means (20) and a predetermined orientation.

2. Gantry system according to claim 1, wherein at least one cross-piece articulated joint (22) is a hinge.

3. Gantry system according to claim 1 or 2, comprising at least two linear actuators (24), each linear actuator (24) being operable to displace a respective coupling portion (16) along the respective rail (10).

4. Gantry system according to claim 3, wherein the at least two linear actuators (24) are independently controllable, and wherein the rotation of the cross-piece main body (14) is caused by different displacements of the coupling portions (16), for example by displacements in opposite directions.

5. Gantry system according to any of the previous claims, wherein the cross-piece main body (14) comprises at least two main body portions (142, 144), said two main body portions being slidably coupled along the cross-piece axis (X) so as the length of the main body (14) along the cross-piece axis (X) can passively change to compensate for a change in the distance between the opposite coupling portions (16) due to a rotation of the main body (14).

6. Gantry system according to any of the previous claims, wherein each cross-piece (12) is provided with first gripper fixture actuating means (26) suitable for displacing the gripper fixture (18) along the cross-piece axis (X).

7. Gantry system according to any of the previous claims, wherein each cross-piece (12) is provided with second gripper fixture actuating means (28) suitable for displacing the gripper fixture (18) along a gripping means axis (Z), for example a vertical axis, orthogonal to the gantry plane (X, Y).

8. Gantry system according to any of the previous claims, wherein the position detecting means (20) includes at least one camera.

9. Gantry system according to any of the previous claims, comprising a control system (30, 40, 42) operatively connected to the position detecting means (20) and to the cross-piece (12), the control system (30, 40, 42) being configured to receive, from the position detecting means (20), current position data related to the current position of an object, compare such current position data with reference data related to a predetermined nominal position and control the cross-piece (12) so as to annul differences between the current position data and the reference data.

10. Gantry system according to claims 4 and 10, wherein the control system (30, 40, 42) is operatively connected to the linear actuators (24) and is configured to command the linear actuators (24) to displace the coupling portions (16) so as to cause an angular displacement of the cross-piece main body (14).

11. Gantry system according to any of the previous claims, wherein the object (1) has a planar rectangular shape, and wherein the position detecting means (20) includes at least two cameras (20a, 20b), said two cameras being positioned so as to detect the position of two opposite vertexes of the object when the object is in the first area (A1) or in an intermediate position between the first area (A1) and the second area (A2).

12. Method for transferring an object from a first area (A1) to a second area (A2) by means of a gantry system according to any of the previous claims, wherein a gripper is installed on the gripper fixture (18) of the at least one cross-piece, the method comprising the steps of: - picking up, by means of the gripper, the object from the first area (A1); - moving the cross-piece (12) along the rails (12) until the object is aligned with the second area (A2); - releasing the object in the second area (A2); wherein the method further comprises the steps of: - detecting, by the position detecting means (20), the current position of the object before picking up the object or during the transfer of the object between the first area (A1) and the second area (A2); - comparing the detected position with a predetermined nominal position; - in case of a misalignment in the angular position between the detected position and the predetermined nominal position, measuring the offset and commanding the main body (14) of the cross-piece to rotate so as to annul the offset before releasing the object in the second area (A2).

13. Method according to claim 12, wherein the gantry system comprises at least two linear actuators (24), each linear actuator (24) being operable to displace a respective coupling portion (16) along the respective rail (10), wherein the at least two linear actuators (24) are independently controllable, and wherein the rotation of the main body (14) to annul the offset is obtained by: - recalculating, from the angular offset, final positions of the coupling portions (16) along the respective rails (10); - driving the linear actuators (24) so as to displace the coupling portions (16) to the recalculated final positions.

14. Method according to claim 12 or 13, wherein the steps of detecting the current position and annulling the angular offset is performed while the cross-piece is moved along the rails to transfer the object from the first area (A1) to the second area (A2).

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