Gripping tool capable of being used by a manipulator device for picking up and handling a workpiece

Abstract

A gripping tool, which can be used by a manipulator device for picking up and handling workpieces, comprises a plurality of gripping devices (50) distributed in groups, each group comprising one or more gripping devices. The gripping devices (50) in each group of gripping devices are mounted on an identical support body (P) made in one piece by additive manufacturing technology.

Description

Technical Field

[0001] The present invention relates to a gripping tool that can be used by a manipulator device for picking up and handling workpieces.

[0002] The tool according to the invention is universal. A particularly preferred exemplary application relates to the case of picking up and positioning metal workpieces in a welding station for assembling a motor vehicle structure or a subassembly thereof. The manipulator device with which the tool according to the invention can be used can also be of any type. A typical example of use is a multi-axis manipulator robot.

[0003] The invention relates in particular to a gripping tool of known type, comprising:

[0004] - a support frame equipped with attachment elements for connection to a manipulator device,

[0005] - a plurality of gripping devices carried by the support frame in a positionally adjustable manner relative to the support frame, and

[0006] - at least one sensor associated with the gripping device for detecting the presence of a workpiece engaged by the gripping device. Background Art

[0007] Gripping tools of the type described above are commonly used in assembly stations, for example for assembling motor vehicle structures, to position a workpiece in an assembly position on another sheet metal element and to hold it in the correct assembly position during welding operations. The support frame of the gripping tool is rigidly connected to an attachment flange, which is intended to be connected to the wrist of a manipulator robot. The robot is thus able to pick up and hold the workpiece in the correct assembly position on another element, which in turn is prepared and positioned in a suitable position on a stationary fixture in the assembly station, with the aid of the aforementioned gripping tool.

[0008] Gripping tools of the aforementioned type are described, for example, in the documents DE 10 2006 047285 B3 and DE 10 2016 009470 B3.

[0009] Tools of the above-mentioned type produced to date have a relatively complex and cumbersome structure and require lengthy and laborious calibration operations.

[0010] A tool according to the preamble of claim 1 is known from the document XP055718884 “3D Printed End-of-Arm Tooling & Fixtures” (Juergen Kortberg) published in 2017 for the “Automatic 2017” exhibition, and from the document XP055774453 EMIcorp “EMI Robot End of Arm Tooling–Catalog R20–July 2019”.

[0011] Purpose of the Invention

[0012] It is an object of the invention to provide a gripping tool of the type indicated at the outset which has a substantially simplified, light and compact structure and which has relatively low costs.

[0013] Another important object of the invention is to provide a gripping tool of the above-mentioned type, in which the calibration operations of the tool for use in an assembly station are simpler and faster than those of the devices of the prior art. Summary of the invention

[0014] In order to achieve one or more of the above objects, the present invention relates to a gripping tool having the features mentioned at the beginning of this specification, wherein:

[0015] - the gripping devices are distributed in groups, each group comprising one or more gripping devices,

[0016] - the gripping devices of each set of gripping devices are mounted on an identical supporting body made in one piece using additive manufacturing technology,

[0017] - the aforementioned supporting body of each group of gripping devices (50) is mounted on the supporting frame in a manner that the position thereof can be adjusted relative to the supporting frame along three mutually orthogonal axes,

[0018] - the aforementioned supporting body of each set of gripping means, made in one piece by additive manufacturing, is shaped so as to define a positioning surface in contact with the workpiece to be gripped, the configuration of said positioning surface being adapted to the configuration of the workpiece to be gripped, in such a way as to constitute a reference for the correct positioning of the workpiece to be gripped relative to said supporting body along said three mutually orthogonal axes,

[0019] The gripping tool is characterized in that the support body in each set of gripping devices comprises an integral connecting part having a cavity in which a support rod is fixed, the support rod being carried by a support frame so as to be positionally adjustable.

[0020] Preferably, the supporting body of at least one of the aforementioned gripping devices also supports said sensor.

[0021] The technology of "additive manufacturing" has been known and used for some time. Additive manufacturing uses an energy source, such as a laser beam, to melt powder layers of synthetic or metallic material in such a way that a component with the desired configuration is formed layer by layer. For example, a machine for producing metal components using additive manufacturing technology is described and shown in document WO 2015 181772 A1.

[0022] Thanks to the use of the aforementioned techniques, the gripping tool according to the invention makes it possible to obtain a structure that is significantly simpler and lighter than the known tools. In fact, the support body that supports each set of gripping devices, manufactured by means of the additive manufacturing technique, is manufactured to have any configuration suitable for satisfying several functions simultaneously: the support body is firstly arranged to support the gripping devices. Secondly, the support body defines a positioning surface that is intended to come into contact with the picked-up workpiece in order to reference the workpiece to a precise position relative to the tool and therefore allow the robot to position the picked-up workpiece in a precise position in the assembly station. Finally, the same support body also performs the function of supporting the aforementioned sensor, which is arranged to detect the presence of the picked-up workpiece. The material constituting each support body, obtained by means of the additive manufacturing technique, can also be a synthetic material or a composite material including reinforcing fibers.

[0023] Thanks to the aforementioned characteristics, the complexity and weight of the tool are significantly reduced compared to known devices, with the advantage of being able to use manipulator robots of smaller dimensions (i.e. with a lower payload), and / or being able to use tools with a greater number of gripping devices once the robot has been dimensioned. Another advantage of the above-described construction is that the adjustment operations of the tool required in the initial calibration steps of the assembly station are greatly simplified. Once the workpiece has been picked up, the robot positions the tool in a predetermined programmed position corresponding to the standard position of the picked workpiece in the assembly station. In this case, the operator can adjust the position of the supporting body of each set of gripping devices in such a way as to obtain a precise positioning of the workpiece in the assembly station, for example relative to another workpiece that has been prepared and positioned in a suitable position in said assembly station.

[0024] In a preferred embodiment, the gripping devices are magnetic effect gripping devices, each of which comprises a support shell and a magnet which can be pneumatically displaced within the support shell between an operative position adjacent to a front end of the support shell and a non-operative position displaced rearwardly relative to the front end of the support shell, the front end of the support shell being arranged to engage a workpiece to be picked up; the tool is characterized in that the support shell of each magnetic effect gripping device is rigidly connected to a corresponding support body obtained by additive manufacturing technology.

[0025] The magnetic gripping device may be of any known type. Gripping devices of this type are produced and sold, for example, by the company Goudsmit Magnetic Systems BV (see also EP 1 541 255 A1).

[0026] The operating principle of these magnetic effect gripping devices is shown in the accompanying drawings. Figure 1 , Figure 2 . These figures schematically show a magnetic effect gripping device, which is indicated as a whole by the reference numeral 1, comprising a support housing 2 in the form of a hollow cylinder in which a permanent magnet 3 is slidably mounted. The magnet 3 can be moved within the support housing 2 between an operative position adjacent to a front end 4 of the support housing 2 and an inoperative position arranged rearwardly relative to the front end 4, the front end of the support housing being arranged to engage a workpiece to be picked up ( Figure 1 ), when it is necessary to release the previously picked-up workpiece, the magnet 3 is carried in the non-operating position. The displacement of the magnet 3 between its operating position and its non-operating position is achieved by delivering a pressurized air flow to one of the two openings 5, 6 of the support housing 2 (arrow A) and sucking air from the other of these openings (arrow B).

[0027] The use of a magnetic effect gripping device in the gripping tool according to the present invention is only a preferred example, and it should be understood that any other known type of gripping device, such as a suction cup gripping device, may be used.

[0028] In the present invention, the support body of each set of gripping means is integrally combined with a connecting portion having a cavity in which the support rods are fixed, and the support rods are carried by the support frame so as to be adjustable in position. In one embodiment, the support rods can be locked in place along their axes in the clamps, and the clamps can then be adjusted in a suitable position on the corresponding auxiliary support tubes along a first axis orthogonal to the axis of the support rods. The auxiliary support tubes can then be adjusted in a suitable position on the main support tubes carried by the aforementioned support frame of the tool along a second axis orthogonal to the first axis and the axis of the support rods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further features and advantages of the invention will emerge from the following description made with reference to the accompanying drawings, provided purely by way of non-limiting example, in which:

[0030] - Figure 1 , Figure 2 is a schematic diagram showing the operating principle of a magnetic effect grabbing device,

[0031] - Figure 3is a perspective view of a preferred embodiment of a gripping tool according to the present invention (in which the housing of the solenoid valve controlling the pressurized air flow required to activate the magnetic effect gripping device has been removed),

[0032] - Figure 4 yes Figure 3 Additional perspective views of the tool shown with the tool's support frame removed,

[0033] - Figure 5 , Figure 6 is a further perspective view, on an enlarged scale, showing Figure 3 , Figure 4 Some details of the tool, and

[0034] - Figure 7 is a perspective view showing a detail on an enlarged scale of a workpiece picked up by a gripping tool according to the invention. DETAILED DESCRIPTION

[0035] Reference Figure 3-7 , reference numeral 8 denotes a gripping tool (or "gripper") which can be used on any known type of manipulator robot to pick up and position workpieces in an assembly station, for example, in a processing station for welding motor vehicle structures or subassemblies thereof.

[0036] Of course, it is obvious that the tool according to the invention is universal and, in particular, it can be used with any type of processing device or machine. Moreover, the tool according to the invention can be used not only for picking up and positioning workpieces in a station where the picked-up workpiece must be assembled on a workpiece previously arranged at a precise position in the station, but also for picking up and positioning workpieces in any other type of industrial equipment, or even just for transferring workpieces from one station to another in a production plant.

[0037] The tool 8 comprises a metal support frame 9 which, in the example shown, comprises a column 10 from which an arm 11 projects laterally and terminates in an attachment flange 12 for attachment to the wrist of a multi-axis manipulator robot of any known type.

[0038] Again, with reference to the example specifically shown, the column 9 has two opposite ends 9A, 9B bearing attachment flanges. The attachment flange 9A is used to screw onto it a plate 13 supporting a tool. At the other end of the column 10, the flange 9B is intended to be connected to an additional tool of any type, for example another gripping tool or, for example, an electric spot welding head, or any other type of operating tool.

[0039] Thus, in the example shown, a manipulator robot having a wrist connected to the attachment flange 12 is able to use tool 8 to pick up and position a workpiece in an assembly station in certain operating steps, and is able to use an additional tool (e.g., a welding head) connected to the attachment flange 9B to perform further operations (e.g., spot welding) on ​​a workpiece that has previously been picked up and positioned in the assembly station in other operating steps.

[0040] Naturally, this configuration is described herein purely as an example; it should be understood that a manipulator robot or any other manipulator machine may simply be provided with the gripping tool described herein.

[0041] Specific reference Figure 5 , support blocks 14 and 15 are threadedly connected to support plate 13 ( Figure 5 , Figure 6 Shows the relative Figure 3 , Figure 4 The tool is in an inverted position to show the support plate 13 in Figure 3 The U-shaped support bracket 16 is in turn threaded onto the support blocks 14, 15, thereby clamping the support tube 17 (which extends from both ends of the plate 13) between the support blocks 14, 15 and the bracket 16.

[0042] In the case of the example shown, the gripping device of the tool 8 is a magnetic gripping device of the type Figure 1 , 2 Schematically shown in FIG. 5 and denoted in the drawings by reference numeral 50. However, as an alternative to these devices, any other type of gripping device may be used, such as a suction cup gripping device.

[0043] Whatever type of gripping device is used, the gripping devices 50 are distributed in groups, each group consisting of one or more gripping devices 50. Each group of gripping devices 50 is carried by an identical supporting body P connected to the frame 9 in the manner described in detail below.

[0044] According to the invention, each support body is made in one piece from a metallic or synthetic material by means of additive manufacturing techniques. Each gripping device 50 is fixed to the corresponding support body P by any connection means, for example by screws.

[0045] Each supporting body P comprises one or more connecting parts B having a cavity in which a supporting rod 18 is received and locked (by means of a screw).

[0046] With reference to the accompanying drawings, in particular with reference to Figure 4, each support rod 18 is locked in place in a clamp 19, which comprises two clamping brackets that are clamped together by means of screws around the corresponding rod 18. The clamp 19 can be released by loosening its fastening screws to allow adjustment of the corresponding support rod 18 along its axis, after which its fastening screws can be tightened again to lock the rod 18 and therefore the corresponding support body P in the desired position.

[0047] Furthermore, the position of at least some of the clamps 19 along the auxiliary support tubes 20, which are orthogonal to the rods 18 and which are in turn rigidly connected to the respective main support tubes 17, is adjustable. To this end, the plate forming part of the clamps 19 is in turn clamped on the auxiliary tubes 20 by means of additional clamping flanges 21 (see in particular Figure 4 on the left side of the ).

[0048] Reference again Figure 4 The auxiliary support tube 20 is supported by a U-shaped bracket 22 (see also Figure 6 ) is rigidly connected, the U-shaped bracket cooperating with an additional U-shaped bracket 23 to clamp the corresponding tube 17 between them.

[0049] In this way, the position of the main body P supporting each group of grasping devices 50 can be adjusted in the direction of the axis of the rod 18, in the direction of the axis of the auxiliary support tube 20 and in the direction of the axis of the main support tube 17 (i.e. along three mutually orthogonal axes).

[0050] from Figure 4 As can be better seen in the left part of , the one or more supporting bodies P also carry a sensor S of any known type intended to come into contact with the workpiece picked up and to emit an electrical signal indicating the presence of this workpiece.

[0051] Figure 7 It is shown by way of example only. Figure 3 , Figure 4 Detail of a tool which is in a state of simultaneously picking up a plurality of workpieces E1, E2, E3 intended to be positioned and welded on a motor vehicle floor panel structure in a station for assembling vehicle floor panels. In this specific application, the floor panel portion to which the elements E1, E2, E3 must be welded is initially arranged in a precise position (relative to a set of three mutually orthogonal reference axes x, y, z) on a stationary fixture of the assembly station and locked therein. The manipulator robot on which the gripping tool is arranged is programmed to arrange the elements E1, E2, E3 on this floor panel portion, which is arranged on the stationary fixture. The tool 8 is constructed in such a way that each gripping device 50 is oriented orthogonal to the surface of the workpiece to which it is joined.

[0052] Under the aforementioned conditions, the elements E1 , E2 , E3 picked up by the gripping tool are positioned in place relative to the tool itself, since the body P supporting each set of gripping means 50 has positioning surfaces in contact with the corresponding surfaces of the elements to be picked up.

[0053] The configuration of these positioning surfaces of the support body is adapted to the configuration of the workpiece to be picked up. Figure 7 In the example of , the element E2 has, for example, a wing 24 which contacts a corresponding lateral positioning surface 25 of the supporting body P to guide the workpiece to a suitable position along a first direction. Similarly, the body P has another lateral surface arranged in a plane orthogonal to the plane of the surface 25, which contacts another wing 26 of the element E2 to guide it to a suitable position along a second direction orthogonal to the first direction. The supporting body P also comprises two downwardly projecting fingers 27 which contact an additional flange 28 of the element E2 to constitute a further reference.

[0054] In the case of element E1, this element comprises a longitudinal element 29 and a transverse member 30. Element E1 is gripped by three sets of gripping means carried by the supporting body, Figure 7 In the figure, these three sets of gripping means are indicated by P1, P2 and P3. The support body P1 has its gripping means engaging one end of the element 29 and the cross member 30. The support body P1 comprises downwardly projecting fingers 31 defining locating surfaces arranged in mutually orthogonal planes which contact respective portions of the cross member 30 to position them in the appropriate position along the longitudinal axis x of the base plate and along the transverse axis y. Additional fingers 32 projecting downwardly from the support body P2 contact the inner and outer surfaces of the element 29 to position it in the appropriate position along the y-axis and the x-axis.

[0055] The support body P3 located at the opposite ends of the element 29 also has downwardly protruding fingers 33, 34, which contact the wall of the element 29 to position it in the appropriate position in the direction of the x-axis and the direction of the y-axis; precise positioning in the z-axis direction is achieved by engaging with additional positioning surfaces of the body P.

[0056] As can be clearly seen from the foregoing, thanks to the use of additive manufacturing technology, in the gripping tool according to the invention, the supporting body of the gripping device can obtain a structure that performs multiple functions simultaneously. Firstly, each supporting body obtained by additive manufacturing has the function of carrying the gripping device. Secondly, the supporting body P has the function of carrying one or more sensors suitable for detecting the workpiece. Thirdly, each supporting body P also performs the function of defining a positioning surface intended to come into contact with the workpiece to be picked up in order to guide the workpiece to a precise position along one or more axes relative to the tool.

[0057] During use, in an initial calibration step, the robot manipulator places the gripping tool and the workpiece picked up by it in a predetermined and programmed position within the assembly station, which corresponds to the theoretical position of the picked up workpiece in the correct assembled state. The robot controller controls the position of the robot wrist and thus the position of the tool connected to the robot wrist relative to a predetermined Cartesian coordinate system. With respect to this same reference system, the assembly station is designed to position the workpiece (for example a bottom panel part) at a precise position on the stationary structure of the station on which the workpiece (or workpieces) picked up by the tool must be positioned and assembled. Once the robot has moved to its predetermined programmed position in the assembly station, the operator can intervene in the fixtures 19-23 to adjust the position of each support body P relative to the frame 9 of the tool along three mutually orthogonal directions until the correct positioning of the picked up workpiece is obtained on the element previously arranged in the assembly station. In this case, the aforementioned fixtures are then tightened again, after which the tool is calibrated for repeating the same operating cycle in the production step without further loss of time.

Claims

1. A gripping tool capable of being used by a manipulator device to pick up and handle a workpiece, the gripping tool comprising: - a support frame (9) provided with an attachment flange (12) for connection to the manipulator device, - a plurality of gripping devices (50) carried by the support frame (9) so as to be positionally adjustable relative to the support frame (9), and - at least one sensor associated with the gripping device (50) for detecting the presence of a workpiece engaged by the gripping device, in: - the gripping devices (50) are distributed in groups, each group consisting of one or more gripping devices (50), - the gripping devices (50) of each set of gripping devices are mounted on an identical supporting body (P) made in one piece using additive manufacturing technology, - the supporting body (P) of each set of gripping devices (50) is mounted on the supporting frame (9) so as to be positionally adjustable relative to the supporting frame (9) along three mutually orthogonal axes (x, y, z), - the shape of the support body (P) in each set of gripping devices (50) made in one piece by additive manufacturing technology is determined to define a positioning surface in contact with the workpiece to be gripped, the configuration of the positioning surface being adapted to the configuration of the workpiece to be gripped, thereby constituting a reference for the correct positioning of the workpiece to be gripped relative to the support body (P) along the three mutually orthogonal axes (x, y, z), The gripping tool is characterized in that the supporting body (P) of each group of gripping devices (50) includes a connecting part (B) of an integral structure, the connecting part has a cavity, a support rod (18) is fixed in the cavity, and the support rod is supported by the supporting frame (9) so that the position can be adjusted.

2. The gripping tool according to claim 1, characterized in that: At least one supporting body (P) also supports said sensor (S).

3. The gripping tool according to claim 1, wherein: The gripping device (50) is a magnetic effect gripping device, each of which comprises a support shell (2) and a magnet (3), the magnet being pneumatically movable within the support shell (2) between an operating position adjacent to a front end (4) of the support shell (2) and a non-operating position spaced rearwardly relative to the front end (4) of the support shell (2), the front end of the support shell being configured to engage a workpiece to be picked up, the gripping tool being characterized in that the support shell (2) of each magnetic effect gripping device (50) is rigidly connected to a corresponding support body (P) obtained by additive manufacturing technology.

4. The gripping tool according to claim 1, characterized in that: The support rods (18) can be locked in place in the clamp (19) along the axes of these support rods, and the clamp can further adjust the position on the corresponding auxiliary support tube (20) along a first axis (x) orthogonal to the axis of the support rod (18), and the auxiliary support tube (20) can further adjust the position along a second axis (y) on the main support tube (17) supported by the support frame (9) of the grasping tool, and the second axis is orthogonal to the first axis (x) and the axis of the support rod (18).

5. A method of using the gripping tool according to claim 1, wherein: The gripping tool is associated with the manipulator device and is used to pick up the workpiece and position it in the correct assembly position on the element arranged on the stationary fixture of the assembly station, Furthermore, during an initial calibration step of the station, once the manipulator device has been moved to a predetermined programmed position theoretically corresponding to the assembly position of the picked workpiece, the position of the picked workpiece relative to the gripping tool is adjusted by adjusting the position of each of the supporting bodies (P) of the group of gripping devices (50) relative to the supporting frame (9) until the correct positioning of the workpiece relative to the elements arranged in the station is actually obtained.

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