Roller-type hemming tool and method for performing a hemming operation

Abstract

 A hemming tool, particularly for an industrial robot, comprises at least one hemming roller (13, 17) and one guiding roller (28) which are carried by clamp-like roller supporting means (20). which are freely floatable around an axis (14) parallel to the axes of said rollers relative to a support (12).

Description

[0001] The present invention relates to a roller-type hemming tool and a method for performing a hemming operation with the aid of this tool. The invention is directed in particular to a hemming tool for an industrial robot, comprising a support for connection to a robot wrist and at least one hemming roller rotatably mounted, either directly or indirectly, on said support.

[0002] Hemming tools of the above indicated type are disclosed for instance in documents JP-A-42 53 524, JP-A-21 97 331, JP-A-612 62 432 and EP-B-0 525 759. These tools are used for performing hemming operations on sheet metal pieces, such as the sheet metal panels forming the structure of a car body part or subassembly, for instance the structure of a car door. The two sheet-metal panels forming a structure of this type are joined to each other by a hemming operation performed along the periphery of the structure or at least along portions thereof. According to a typical configuration, a peripheral edge portion of one of the two sheet metal panels is initially bent at 90° and the corresponding edge portion of the other panel is configured flat and juxtaposed to the other panel immediately adjacent to the edge portion bent at 90°. The hemming operation is typically performed in two subsequent stages. In a first stage, the 90° portion is initially bent towards the other panel by about 45°. In a second stage, the 45° bent portion is further bent by another angle of about 45° so as to be pressed flat against the other panel. According to the known solutions disclosed in the above identified documents, a tool with at least one rotatable hemming roller is mounted on the wrist of an industrial robot. The robot moves and presses the roller along the peripheral edge of the pieces to be hemmed. In all the above identified documents, the two stages of the hemming operation are performed by two subsequent passages of the hemming roller or rollers along the periphery of the structure to be hemmed. In a first passage, the 45° bending is performed, and in a second subsequent passage, the hemming operation is completed by a further 45° bending step.

[0003] It has already been proposed to move two hemming rollers located adjacent to each other simultaneously along the periphery of the structure to be hemmed, so that one roller performs the first 45° bending and the second roller, which is located behind the first one with respect to the direction of movement, performs the second final bending. In this manner, both stages can be performed in a single passage of the two rollers along the periphery of the structure to be hemmed. This solution is disclosed in WO-A-0 013 816 and equivalent EP-A-1 097 759. These documents show two rollers which are attached to two independently controllable robot arms so as to be both simultaneously roll-pressed along a portion to be processed. The description of a EP-A-1 097 759 also clarifies that in alternative to the use of two separate multi-articulated robot arms also a single multi-articulated robot provided with two arms carrying the two rollers can be used.

[0004] However, all the above indicated known solutions involve a common drawback, irrespective of whether they involve a single passage or a double passage to perform the two stage hemming operation. This drawback lies in that in order to perform the hemming operation, the hemming rollers must be pressed against the edge portions to be deformed. Since the hemming rollers are carried by the wrist of an industrial robot, this wrist and/or the structure of the robot must be designed and constructed in order to be able to withstand the loads which must be imparted on to the rollers in order to perform the hemming operation.

[0005] The main purpose of the present invention is that of providing a hemming tool and method by which the above indicated drawback can be overcome.

[0006] In view of achieving this object, the invention provides a hemming tool, particularly for an industrial robot, comprising a support and at least one hemming roller rotatably mounted, either directly or indirectly, on said support, characterized in that said tool further comprises:

• at least one guiding roller substantially opposite to said hemming roller, and
• clamp-like roller supporting means mounted on said support and movable between an opened position and closed position,
• at least one of said hemming roller and said guiding roller being carried by said clamp-like roller supporting means, so that said hemming roller and said guiding roller move towards and away from each other as a result of a movement of said clamp-like roller supporting means between their opened position and their closed position.

[0007] When a hemming operation is performed with the aid of the hemming tool according to the present invention, the structure to be hemmed is located on a supporting jig or die, whereupon the robot carrying the hemming tool is controlled so that this tool moves relative to the portion of the structure to be processed. This operation is carried out by "clamping" the die, along with the structure located thereon, between the hemming roller and the guiding roller. The hemming roller is pressed against the portion to be bent, while the guiding roller is kept in contact with an oppositely facing surface of the die. Thus, the load which must be imparted on the structure in order to perform the bending operation is absorbed by the above mentioned clamp-like roller supporting means and is not transmitted to the wrist and the structure of the robot.

[0008] In a preferred embodiment of the tool according to the invention, the above mentioned clamp-like roller supporting means includes a first arm and a second arm pivotably mounted relative to each other, at least one of said hemming roller and said guiding roller being carried by one of said first and second arms. The clamp-like supporting means further include an actuator interposed between said first and second arms for controlling the relative position thereof. During the hemming operation, it is this actuator which applies the load which is necessary for the hemming operation, by "closing" the clamp means on the structure to be hemmed, with the hemming roller pressed in contact against a surface of the structure to be hemmed and the guiding roller pressed against an oppositely facing surface of the die on which the structure to be hemmed is supported.

[0009] Still in the case of the preferred embodiment, a further important feature of the tool of the invention lies in that said clamp-like roller supporting means is pivotable, as a whole unit, around a first axis relative to said support.

[0010] Due to this feature, the clamp-like roller supporting means constitute a sort of "trolley" which is able to follow automatically the height variations of the profile of the structure to be hemmed, by oscillating around the above mentioned first axis, while the hemming tool is moved relative to the portion to be hemmed.

[0011] In one example, the above mentioned first arm of the clamp-like roller supporting means is pivotably mounted onto said support around the above mentioned first axis (around which the whole unit can oscillate), and said second arm is pivotably mounted on to said first arm around a second axis parallel to said first axis. In this example, the guiding roller is rotatably mounted onto the second arm, while the hemming roller is rotatably mounted onto one of said support and said first arm. Preferably, the hemming roller is rotatably mounted onto the support and has an axis coincident with said first axis around which the whole unit can oscillate.

[0012] Again with reference to the preferred embodiment of the invention, another important and preferred feature of the invention lies in that the hemming tool further comprises a second hemming roller adjacent to the above mentioned first hemming roller.

[0013] Due to this feature, the two hemming rollers can be shaped and arranged so that they are able to perform the first 45° bending operation and the second final bending during a single passage of the tool along the portion to be processed.

[0014] For example, with reference again to the embodiment mentioned above, the first hemming roller which is to perform the first 45° bending operation, is rotatably mounted on the support with its axis coincident with the first axis (around which the whole clamp-like unit is able to oscillate), whereas the second hemming roller which is to perform the final bending operation is carried by the above mentioned first arm of the clamp-like supporting means. When the tool is moved along the portion to be processed, the first hemming roller performs the first 45° bending while proceeding along the portion, while the second hemming roller, which is located immediately behind the first hemming roller with reference to the direction of movement, performs the second and final bending immediately after the first bending carried out by the first roller. Again, while the two hemming rollers follow the portion to be processed, the guiding roller follows an oppositely facing surface of the die on which the structure to be hemmed is located.

[0015] The actuator controlling the relative position of the first and the second arm may be a fluid cylinder interposed between these arms. Preferably, the actuator is a pneumatic cylinder which has an intrinsic elasticity which allows for limited relative movements of the first and second arms of the clamp-like device due to variations of the profile of the structure to be processed which are encountered while the rollers proceed along this structure.

[0016] As indicated in the foregoing, the present invention is also directed to the hemming method which is performed with the use of the above described hemming tool.

[0017] Further features and advantages of the invention will become clearly apparent from the following description, which is given purely by way of nonlimiting example, with reference to the accompanying drawings, in which:

• figure 1 is a perspective view of an exemplary installation making use of the hemming tool according to the invention,
• figure 2 is an elevational view of the installation of figure 1,
• figures 3 and 4 show two perspective views of a preferred embodiment of the tool according to the invention,
• figure 5 is a diagrammatic side view of the tool of figures 3 and 4,
• figure 6 is a perspective view at an enlarged scale of the rollers used in the tool according to the present invention, during one stage of a hemming operation,
• figure 7 is an exploded perspective view of the hemming tool of figures 3-5, and
• figure 8-10 are front views which show alternative uses of the rollers carried by the tool of the present invention.

[0018] Figure 1 shows a typical installation where the tool according to the invention can be used, for processing car door structures. A car door is typically formed by two sheet metal panels joined to each other along at least a portion of their periphery by a hemming operation. In the example shown in figure 1, an installation 1 is provided with a central column 2, and a number of stations 3 (only two of which are shown in figure 1) arranged around the central column 2. In figure 1, one station 3 is shown with a column 4 carrying a die 5 (see also figure 2) on which a door structure 6 is supported. The door structure 6 is formed by two sheet metal panels which are placed in contact with each other and kept in this position by a holding rack 7 carried at the lower end of a vertical arm 8 supported at its upper end by a bracket 9 attached to the central column 2. The structure of the die 5, the holding rack 7, and the vertical arm 8, which is movable between a raised position and a lowered position, is not shown nor described herein in detail, since these elements may be formed in any known way and do not form part of the present invention. Moreover, the elimination of these details from the drawings renders the latter simpler and easier to understand.

[0019] The two panels constituting the door structure are joined to each other by a hemming operation which is performed with the aid of a hemming tool 10 according to the present invention. The hemming tool 10 is carried by the wrist of an industrial robot 11 which is mounted at the top of the central column 2. It must be noted however that both the structure and the arrangement of the robot carrying the hemming tool according to the invention may widely vary with respect to what is illustrated herein purely by way of example. Moreover, in particular applications, it is not excluded that the tool of the invention can be mounted on any type of carriage movable and controlled along a given direction rather than on an articulated robot. Therefore, in the present description and also in the accompanying claims, the expression "industrial robot" must be interpreted in a very broad sense, as meaning any type of structure which can be moved along at least one direction in a controllable manner. Furthermore, it is not excluded herein even the case where the hemming tool is stationary and the structure to be processed is caused to move relative to the hemming tool. Therefore, the present invention is also directed to the hemming tool per se, irrespective of whether this hemming tool is to be mounted on a robot or not.

[0020] With reference to figures 3-5 and 6, the hemming tool 10 comprises a support 10 which is rigidly connected to the wrist 12 of the robot 11. In the example shown, the support 12 includes two vertical side plates 12a screwed at the top to respective sides of a horizontal plate 12b. In the case of the embodiment shown in the drawings, the hemming tool of the invention comprises two hemming rollers and one guiding roller. A first hemming roller 13, which will be described in detail herein under, is freely rotatably supported around a first axis 14 on the lower end of one side plate 12a of the support 12 by means of a pin 15 (see figure 7) which is arranged through coaxial holes 16 formed in the lower ends of both side plates 12a of support 12.

[0021] A second hemming roller 17, whose shape and function will be also described in detail herein under, is freely rotatably supported around an axis 18 (figure 5) parallel to axis 14 on one arm 19 of a clamp-like roller supporting unit 20. The roller 17 is freely rotatably mounted around axis 18 by means of a pin 21 (figure 7) which engages a hole 22 formed in arm 19. In the embodiment shown, the arm 19 has a fork-like structure (see figure 7) comprising two side plates 19a connected at the top by a plate 19b.

[0022] The above described first arm 19 of the clamp-like unit 20 is pivotably mounted around the same axis 14 of roller 13 with respect to support 12. To this end, the side plates 19a of arm 19 have coaxial holes 23 (one of which is visible in figure 7) which receive the above mentioned pin 15 on which roller 13 is supported.

[0023] The clamp-like unit 20 includes a second arm 24 which is arranged in the space between side plates 19a of the first arm 19 and is pivotably connected to the first arm 19 around a third axis 25 parallel to axes 14, 18. To this end the two side plates 19a of arm 19 and arm 24 have aligned holes 26, 27 for engagement of a common shaft (not shown). In proximity to its lower end, the second arm 24 carries a guiding roller 28 which is freely rotatable around a fourth axis 29 parallel to axes 14, 18, 25. To this end, the lower end of arm 24 is provided with an enlarged portion 24a (see figure 7) having a through hole 30 which receives a pin 31 for rotatably supporting the roller 28.

[0024] Thus, the two arms 19, 24 form a clamp-like unit. The two arms are pivotable relative to each other around axis 25, so as to be movable between an opened condition, shown in figures 3-5, in which the guiding roller 29 is relatively spaced apart from rollers 13, 17, and a closed condition (not shown) in which the guiding roller 29 is closer to rollers 13, 17. The relative position of arms 19, 24 is controlled by a pneumatic cylinder 32 which is operatively interposed between these arms. In the example shown, the casing 33 of the cylinder is rigidly connected to arm 19, whereas the stem of the cylinder is pivotably connected at 34 to the upper end of the second arm 24. Also in the example shown, the casing 33 of cylinder 32 is screwed to two side blocks 35 (figure 7) which in turn are screwed to plate 19b of arm 19.

[0025] As a result of the above described arrangement, an activation of the cylinder 32 causes a change in the relative position of arms 19, 24 of the clamp-like supporting unit 20.

[0026] Moreover, since arm 19 of the clamp unit 20 is pivotably mounted onto support 12 around axis 14, while second arm 24 is pivotably mounted onto the first arm 19 around axis 25, the whole clamp unit formed by the two arms 19, 24 is pivotable relative to support 12 around the first axis 14. In the rest condition, this unit is held in the position shown in figures 2-5 by two pair of springs 36 which are arranged on both sides of blocks 35 and are interposed between theses blocks and the structure of support 14.

[0027] Finally, as visible in figures 3, 4 and 7, the hemming tool 10 is provided with another group of three rollers 37, 38, 39 on the side of the tool opposite to that carrying rollers 13, 17, 28. Roller 37 is rotatably mounted onto a respective side plate 12a of support 12 by means of pin 15 (figure 7). Roller 38 is rotatably mounted on arm 19, on the side opposite to that carrying roller 17, by means of pin 21. Finally, roller 39 is rotatably mounted at the lower end of the second arm 24, on the side opposite to that carrying roller 28, by means of pin 21.

[0028] Figure 6 of the accompanying drawings shows the basic principle of operation of the hemming tool according to the invention.

[0029] As already indicated, the hemming operation is performed by controlling the robot 11 in order to move the hemming tool 10 along the structure to be processed. As already indicated, this structure comprises two sheet metal panels juxtaposed with each other. With reference to figure 6, a lower panel 40 is arranged with an edge portion 41 initially bent at 90° relative to the general plane of the panel, whereas a second panel 42 is placed above the lower panel 40 with its edge 43 configured flat and adjacent to the bent edge 41 of the lower panel 40. While robot 11 causes a movement of rollers 13, 17 along the bent edge 41, the hemming operation is carried out. The first roller 13 which encounters the 90° bent edge 41 causes, due to the engagement of its conical portion 13a against the edge 41, a first 45° bending of edge 41. As soon as edge portion 41 has been bent by 45°, it is further bent flat against edge 43 of the upper panel 42 by the cylindrical portion 17a of the second hemming roller 17.

[0030] As clearly visible in figure 6, while the two hemming rollers 13, 17 proceed along edge 41, the lower guiding roller 28 is pressed in contact against the lower surface 5a of die 5. As also described in the foregoing, the structure constituted by the die 5 with the two panels 40, 42 placed thereon it is thus "clamped" between the upper hemming rollers 13, 17 and the lower guiding roller 28. This is obtained by activating the cylinder 32 which acts as an actuator tending to move the clamp-like unit 20 towards its closed position, so that the rollers are pressed against the respective contact surfaces.

[0031] Due to this arrangement, the load which must be imparted to the panels in order to perform the hemming operation is absorbed by the structure of the clamp-like unit 20, while being not transmitted to support 12 and the structure of the robot to which support 12 is connected.

[0032] Moreover, since the whole clamp-like unit 20 is able to freely oscillate around axis 14, this unit is able to float freely around this axis while the rollers 13, 17 follow any changes in height of the profile of the panels while the tool proceeds along the portion to be processed. During this movement, the intrinsic elasticity of the pneumatic cylinder 32 allows limited changes in the relative position of the two arms 19, 24 around axis 25, whereas springs 26 always tend to bring the whole clamp-like unit 20 towards its neutral position.

[0033] As already indicated, in the specific embodiment illustrated herein, the hemming tool is provided with a group of three rollers on both sides, so that it can be used relying on the rollers provided on one side or the other, thus obtaining a high flexibility in the application of the device.

[0034] Obviously, the advantage of discharging the loads on the clamp unit 20 itself enables the use of a simplified structure also for the supporting die 5. As clearly shown in figures 3, 4, the rollers of the hemming tool of the invention are preferably provided at their free ends with the noses N of cylindrical shape and reduced diameter, for performing specific special tasks as shown herein under.

[0035] Naturally, the rollers provided on both sides of the hemming tool may have dimensions adapted to different tasks. Thus, the double side design of the hemming tool according to the preferred embodiment of the invention renders this tool multi-functional.

[0036] Figures 8, 9 and 10 show auxiliary tasks which can be performed by the above described hemming tool. Figure 8 shows a hemming operation performed along the edge of the window of a car door, wherein the nose N of a roller 37 is exploited, while the other side of tool (figure 9) can be used for flat hemming of the outer edge of the door.

[0037] According to a further feature of the invention, the rollers on the hemming tool can be interchanged with rollers of different size and shape, such as rollers 37', 38' 39' of figure 10, where roller 37' has a circumferential groove 44 in order to define a rope-like edge 45 on a hemmed portion of sheet metal.

[0038] As it is clearly apparent from the foregoing description, the hemming tool according to the invention has a structure of low cost, is highly flexible in use and allows the combination of the extreme capabilities of robots with hemming requirements without any compromise to quality.

[0039] Naturally, while the principle of the invention remains the same, the embodiments and the details of construction may widely vary with respect to what has been described herein purely by way of example, without departing from the scope of the present invention.

Claims

1. A hemming tool, particularly for an industrial robot, comprising a support (12) and at least one hemming roller rotatably mounted either directly or indirectly on said support (12),
   characterized in that said tool (10) further comprises:

- at least one guiding roller (28; 39) substantially opposite to said hemming roller (13, 17; 37, 38), and

- clamp-like roller supporting means (20) mounted on said support (12) movable between an opened position and a closed positioned,

- at least one of said hemming roller (13, 17; 37, 38) and said guiding roller (28; 39) being carried by said clamp-like roller supporting means (20), so that said rollers are moved towards and away from each other as a result of a movement of said clamp-like roller supporting means (20) between their opened and closed position.

2. A hemming tool according to claim 1, characterized in that said clamp-like roller supporting means (20) includes a first arm (19) and a second arm (24) pivotably mounted relative to each other, at least one of said hemming roller and said guiding roller being carried by one of said arms (19, 24), and an actuator (32) being interposed between the first and second arms (19, 24) for controlling the relative position of said arms.

3. A hemming tool according to claim 2, characterized in that said clamp-like roller supporting means (20) is pivotable as a whole unit around a first axis (14) relative to said support (12).

4. A hemming tool according to claim 3, characterized in that:

- said first arm (19) is pivotably mounted onto said support (12) around said first axis (14)

- said second arm (24) is pivotably mounted on said first arm (19) around a second axis (25) parallel to said first axis (14),

- said guiding roller (28; 39) is rotatably mounted on said second arm (24),

- said hemming roller (13; 37) is rotatably mounted on one of said support (12) and said first arm (19).

5. A hemming tool according to claim 3, characterized in that said hemming roller (17; 38) is rotatably mounted on said support (12) on an axis coincident with said first axis (14).

6. A hemming tool according to claim 1, characterized in that said tool further comprises a second hemming roller (17; 38) adjacent to said first hemming roller (13; 37).

7. A hemming tool according to claim 5, characterized in that said tool further comprises a second hemming roller (17; 38) adjacent to said first hemming roller (13; 37), and in that said second hemming roller (17; 38) is rotatably mounted on said first arm (19).

8. A hemming tool according to claim 6, characterized in that said actuator (32) is a fluid cylinder interposed between said first arm (19) and said second arm (24).

9. A hemming tool according to claim 3, characterized in that said tool further comprises spring means which are interposed between said clamp-like roller supporting means (20) and said support (12) and tending to hold the clamp-like roller supporting means (20) in a rest position relative to said first axis (14) around which the clamp-like roller supporting means (20) is pivotable.

10. A hemming tool according to claim 1, characterized in that said clamp-like roller supporting means has two opposite sides each provided with at least one hemming roller and one guiding roller.

11. A hemming tool according to claim 1, characterized in that at least one of said rollers has a cylindrical nose (N) of reduced diameter.

12. A hemming tool according to claim 1, characterized in that at least one of said rollers is interchangeable with rollers of different shapes and dimensions.

13. A hemming robot, characterized in that it comprises a hemming tool according to any of the previous claims.

14. A hemming installation, comprising at least one die (5) for supporting a piece to be hemmed, holding means (17) for holding said piece to be hemmed on the die (5), a hemming tool (10) and means for causing a relative movement of the hemming tool with respect to the piece to be hemmed, wherein said hemming tool is in accordance with any of claims 1-12.

15. A method for performing a hemming operation on a sheet metal piece, comprising:

- proving a support (12) and at least one hemming roller rotatably mounted, either directly or indirectly, on said support (12), and

- moving said support (12) relative to said piece while said hemming roller rolls along one edge portion of said piece,

   characterized in that a guiding roller (28)is further provided substantially opposite to said hemming roller (13, 17), and clamp-like roller supporting means are also provided which are mounted on said support (12) and movable between an opened position and a closed position, at least one of said hemming roller (13, 17) and said guiding roller (28) being carried by said clamp-like roller supporting means (20) so that said rollers are moved towards and away from each other as a result of a movement of said clamp-like roller supporting means between said opened position and said closed position, and

- in that the clamp-like roller supporting means (20) are controlled during the hemming operation so that while the hemming roller engages said edge portion, said guiding roller engages an oppositely facing surface of a die (5) on which said piece is supported, so that the die (5) with the piece located thereon is pressed between said hemming roller (13, 17) and said guiding roller (28),

- whereby the load applied on the piece during the hemming operation is taken up by said clamp-like roller supporting means (20) without being transmitted to said support (12),

16. Method according to claim 15, characterized in that said clamp-like roller supporting means (20) is pivotable as a whole unit around the first axis (14) relative to said support (12) so that during the hemming operation the clamp-like roller supporting means is able to freely float around said first axis (14) while said hemming roller (13, 17) follows the profile of said edge portion of said piece.

Drawing