The present invention relates to the field of multi-axis industrial robots, of the type comprising a base structure, an articulated robot wrist and a chain of mutually articulated robot elements which connect said base structure to said robot wrist, wherein said robot wrist also ends with a flange, to which a tool is rigidly connected that requires a power supply and/or a fluid supply, and wherein through said chain of mutually articulated robot elements, and through said robot wrist, a continuous internal passage is defined in which one or more cables and/or pipes for said power supply and/or said fluid supply to the tool are received.
A robot of the type specified above is, for example, described and illustrated in document U.S. Pat. No. 8,006,586 B2 owned by the same Applicant.
In robots of the type specified above, the harnessing of cables and pipes for the power supply and the fluid supply to the tool carried by the robot poses several problems. On the one hand it is necessary to prepare systems for retaining and guiding the cables and pipes that minimize the risk that they may interfere or become entangled with foreign bodies during the use of the robot in a production line. On the other hand it is also necessary to guide and protect the cables or pipes in order to reduce the deformation of bending and torsion as much as possible, to which they are subject during the movements of the robot, and especially so as to reduce the deterioration to which the cables are subject to due to exposure to aggressive external agents (weld splatter, dirt, etc.) that are often found in an industrial production line. Exposure of the cables to these agents often leads to greater and premature wear of such components, with the result that the harnessing of cables and pipes must be replaced more frequently (even after just one or two years from the first use), consequently requiring a greater number of stops and a lower productivity of the robot. Finally, it is also important to prepare the harnessing in such a way that its replacement can be carried out in a simple and rapid manner.
An object of the present invention is to solve or improve on all the above problems in an optimum manner, by creating a robot which is generally more efficient in its use and requires the minimum number of maintenance operations.
In view of achieving this scope, the invention has as a principal object: a multi-axis industrial robot having all the characteristics, which have been indicated at the beginning of the present description and further characterized by the fact that the said cables and/or pipes for the power and/or fluid supply to the tool continue without interruption in a passage formed through said flange of the robot up to the said tool, whereby said cables and/or pipes are arranged completely inside the robot and inside the tool, without the need to lay separate cables and/or pipes for the tool connected to the cables and pipes of the robot in correspondence of said flange, which instead occurs in known solutions.
An important advantage of the present invention is that the total protection of the cables and supply pipes completely avoids the premature wear of these components determined in the known solutions from contamination by aggressive external agents (weld splatter, dirt, etc.) present in industrial environments. Experiments conducted by the applicant have allowed prediction that the invention will result in an enormous advantage in terms of less replacements of the harnessing of the robot, since the average duration of a harnessing can change from a minimum time of about 1.5-2 years to a minimum time of about 8-10 years, almost comparable to the life of the robot. The invention is therefore able to produce a real breakthrough in the practice of robot use.
In a particularly preferred embodiment, the said tool is an electric spot welding head, of the type comprising a support structure rigidly connected to the robot wrist, a pair of welding electrodes carried by respective electrode-holding arms, wherein at least one of said electrode-holding arms is movably mounted on the support structure of the head between an open position and a closed position; said head further comprising an actuator for the activation of said movable arm and an electric transformer for the application of welding voltage to the electrodes. In this preferred embodiment, the electrical supply cables continue uninterruptedly through said flange of the robot inside the support structure of the head, up to a connector input of said electrical transformer.
In the case of the preferred embodiment, the supporting structure of the head is fixed by screws to the robot flange, preferably with the interposition of an intermediate bracket.
In the welding head described above, the body of the electrical transformer presents a rear wall facing towards the robot flange, a front wall opposite the rear wall, two side walls, and two end walls. According to a further particularly preferred characteristic, the two output poles of the transformer, which are connected to the two electrode-holding arms, are disposed: one on said front wall and the other one on said end walls of the body of the transformer. Thanks to this arrangement, the linking strips connecting the output poles of the electrical transformer to the respective electrode-holding arm can be arranged according to configurations that guarantee a more compact size of the welding head, particularly in the longitudinal direction of the head, i.e. in a direction which goes from the flange of the robot towards the electrodes.
Of course, a compact welding head having the characteristics indicated above may also be used in a robot of the traditional type and for this reason it also forms the subject, taken by itself, of a co-pending patent application by the same Applicant, U.S. application Ser. No. 13/892,757 published as US 2013/0306603 A1, the entire contents of which is incorporated by reference.
It should also be noted that, for reasons of easier maintenance, the pipes for supplying fluid to the tool can still be provided with a separated end portion, associated with the tool, and connected by means of quick couplings to the corresponding pipes associated with the robot. In this case, the basic principle of the invention is still applied to the electrical cables (power and/or signal) associated with the robot.
The invention will now be described with reference to the accompanying drawings, provided purely by way of a non-limiting example, wherein:
With reference to
In the case of the example illustrated in
With reference to
As already indicated, the passing cavities of said first, second and third hollow body 22, 24, 26 form a continuous passage along the axes W, V, VI, through which cables and/or pipes are arranged for the power supply, the fluid supply and the control of the tool associated with a flange F leaving from the third hollow body 26. The said passage has a substantial capacity for which there is a considerable number of cables and/or pipes that are able to receive. For example, in the case that the tool is an electric spot welding head, the power supply lines that pass through the internal passage of the robot wrist comprise two delivery pipes of a refrigerant fluid, two return pipes of the refrigerant fluid, a cable to the control the signal of an electric drive motor of the head, a power cable of this electric motor, a multi-bus cable, and three power supply cables (or, alternatively, a single power cord with three wires) for the electric current welding.
Again with reference to the illustrated example, the axes IV and VI are inclined with respect to the axis V by an angle between about 50° and 70°. Preferably, this angle of inclination is 60°. This choice of inclination of the axis of rotation V, relative to the axes IV and VI, allows the obtainment of a wide working-range of the robot wrist, and at the same time ensures a simple and continuous passage of cables and/or pipes within the wrist. As can be seen, in the condition wherein the axes W, V, VI are coplanar, they define a Z configuration.
Again with reference to the illustrated example, at the connection between the arm 18 and the hollow body 22, housing for a first gearmotor 27 is provided. According to the size of the first hollow body 22 and of its cylindrical portion intended to be coupled to the arm 18 of the robot, the housing for the first gearmotor 27 can be entirely obtained in the first hollow body 22 or even partially in the arm 18 of the robot, but always in such a way that the first gearmotor 27 is substantially included within the volumes defined by the geometry of the arm 18 and the first hollow body 22, with particular reference to the dimensions of the section of this arm. In correspondence to the second hollow body 24 a further housing for a second gearmotor 29 is provided. In particular, as visible in
Between the first hollow body 22 and the second hollow body 24 a single crossed roller bearing 33 of known type is arranged, having an inner ring 32 and rigidly connected to the first hollow body 22, while an outer ring 34 is rigidly connected to the second hollow body 24. A single crossed roller bearing 37 is also provided between the second hollow body 24 and the third hollow body 26, with an outer ring 36 rigidly connected to the second hollow body 24 and an inner ring 38 rigidly connected to the third hollow body 26.
Each gearmotor 27, 29 comprises a respective motor 28, 30, a coupling flange 31, a gearbox 40 as already indicated above, and a pinion 42, 46. The gearboxes 40 are characterized by a high transmission ratio and are preferably of the epicyclic or harmonic type. Each gearbox 40 is coupled at its one end to its relative motor 28, 30 through the coupling flange 31. The coupling flange is connected by screws 35a to the motor 28, 30 and to the gearbox by means of other screws 35b.
At the other end, the respective gearbox 40 carries the pinion 42, 46 for the transmission of motion, which is now fixed by means of a plurality of screws 35c. The first gearmotor 27 comprising the first motor 28, gearbox 40 and a bevel pinion 42 is fixed by screws in abutment with a bottom wall 39 of the respective housing. Between the bottom wall 39 of the housing and the end of the gearbox which is fixed to the bevel pinion 42, a flange 41 for fixing and adjustment of the clearance is interposed. During assembly of the wrist, the thickness of the flange 41 is adapted so as to obtain the correct meshing of the pair of bevel gears. The bevel pinion 42 meshes with the internal teeth of a ring bevel gear 44, and this, being fixed by means of screws (not shown) to the outer ring 34 of bearing 33, is rigidly connected to the second hollow body 24. The second gearmotor 29 comprising the second motor 30, gearbox 40 and a cylindrical pinion 46 is inserted into the slot formed in the second hollow body 24 and is secured in abutment with a bottom wall 43 of said housing by means of screws. The cylindrical pinion 46 meshes with a ring-shaped cylindrical wheel 48 which is fixed to the inner ring 38 of bearing 37.
The motion of rotation from the motor 28 is transformed through the gearbox 40 and transferred to the bevel pinion 42 which rotates the ring bevel gear 44 rigidly connected to the outer ring 34 of bearing 33, in turn fixed to the second hollow body 24. In this way, the rotation of the second hollow body 24 about the axis V is carried out. When the second gearmotor 30 is activated, the rotation is transferred through the gearbox 40 to the cylindrical pinion 46. The cylindrical pinion 46 meshes with the cylindrical wheel 48, which is rigidly connected to the inner ring 38 and the third hollow body 26. In this way the rotation of the third hollow body 26 around the axis VI is carried out.
The internal cavity of the wrist allows the passage of supply cables and/or ducts C of the welding head intended to be associated with the flange F. These cables and/or ducts C are associated with a bushing 47.
As indicated above, the said known hollow wrist configuration is also used in the preferred embodiment of the robot according to the invention, it being understood, however, that the teachings of the invention are also applicable to robots with different configurations.
As seen in
In the case of known robots, and also in the specific case of the known robot illustrated in
In contrast to this arrangement, in the robot according to the invention no rapid replacement of the tool carried by the robot is provided and the tool (in this specific example the welding head) is not provided with cables and separate pipes that are connected to the cables and pipes of the robot when the tool is mounted on the robot flange. As clearly shown in
The welding head is therefore fully integrated into the robot, so that together, the robot and welding head constitutes a single “welding machine,” without any distinction between the robot part and the tool part, and without any possibility of rapid replacement of the tool. This solution, compared to the known solution from the document U.S. Pat. No. 8,006,586 B2, has the advantage of not providing any connector of connection between cables and pipes of the robot and separate cables and pipes arranged on board of the welding head and therefore does not entail the drawback of the known solution, wherein the cables and pipes associated with the head, which extend from the flange of the robot towards the head, are at least partially exposed to the outside.
As is visible in the accompanying drawings and as will be illustrated in further detail below, this advantage is further enhanced by providing an outer casing for the welding head that forms a prolongation of the body of the robot and that completely hides the tract of cables and pipes which extend beyond the flange of the robot.
In
With reference to
The components of the actuator 116 are not illustrated herein because, as said, this actuator is realizable according to any known configuration and because the elimination of these details from the drawings renders them more readily and easily understood.
The electric current for the welding is carried across the electrodes 101, 102 by passing it through the structure of the arms 103, 104, consisting of aluminum, and having a hollow prism configuration, with side walls bearing lightening holes 117. The body of the arms 103, 104 is electrically connected to the two output poles 118, 119 of an electric transformer T arranged between the two plates 111 of the supporting structure of the welding head.
With reference also to
According to a further important feature of the invention, which allows the relaying of particular compactness to the welding head, the two output poles 118 and 119 of the transformer T are arranged on different walls of the transformer body. More precisely, the pole 118 is provided on the front wall 121, while the pole 119 is provided on the lower end wall 124. The poles 118, 119 are also electrically connected to the structure of the respective arms 103, 104 by means of an elastically deformable strip 125 is, having a general U-configuration (
Both the transformer T and the welding electrodes 101, 102 require fluid-refrigeration. Therefore, in the bundle of cables and pipes which extends beyond the flange of the robot (see
The proximal ends of the pipes 128, 129 are connected via connectors 130 (see
The other arm 103 is constituted of a stem guided in a slidable way in a prismatic guide 200 carried at the ends by two plates 201 fixed to the plates 111 of the head structure. The stem 103 is connected at its end to the stem of the actuator 116 so as to be linearly displaceable along the axis of the actuator 116 between an open position, in which the electrodes 101, 102 are spaced apart, and a closed position, in which these electrodes are in contact with each other. The arrangement of the transformer T is identical to that described above with the output poles of the transformer T disposed on the front wall and on the lower wall of the transformer. In this case, the elastically deformable strip 125 has a U-shaped configuration orientated horizontally (
This arrangement is also clearly visible, as already described above, in
Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may widely vary with respect to those described and illustrated purely by way of example, without departing from the scope of the present invention.
In particular, the basic principles of the invention are also applicable to a robot equipped with a tool of any other type, not necessarily an electric spot welding head. For instance, this tool may be a gripper, which can be used to pick up, support and/or move and deposit components in an industrial plant.
Number | Date | Country | Kind |
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12168065.6 | May 2012 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2013/053759 | 5/9/2013 | WO | 00 |