System for welding structures composed of sheet metal, with prepositioned tools

Abstract: The invention consists of a work station for welding sheet metal structures, for example the bodies of motor vehicles, to which the structures are fed in succession. Said station is provided with a pair of opposing movable elements carrying positioning, clamping and, if necessary, welding tools disposed in units comprising a plurality of said tools disposed fanwise. Each of the tools of said plurality is movable from an operative position to a retracted non-operative position so as to be able to work, or not work, on a body disposed between the pair of opposing movable elements. Each time the model of the body arriving at the station is changed, the tools of each plurality are selectively made to move into one of said two positions so as to bring the tools suitable for manufacturing the particular model of body into the working position.

Description: There are known automated work stations which carry out the operations of fitting and welding together shaped metal sheets and the like to form monolithic structures, such as, for example the bodies of motor vehicles, driver's cabs of trucks and other structures, as for example in the electrical household appliances sector. Said work stations make use of elements, called "configurators" which consist of a frame supporting centering, clamping and, if necessary, also welding means disposed so as to be able to secure and weld a particular conformation of metal sheet. The type and arrangement of the devices supported by the configurators depends upon the particular production that the station is used for. For this reason, in the known technique, in order to make the work stations more flexible, the configurators were made uncoupleable and replaceable thanks to a small automatic magazine inside the welding station so as to enable them to adapt quite rapidly to a different model. For example, in the case of the manufacture of car bodies this makes it possible to handle different models, or types of car on the same production line. In order to make the system even more flexible, work stations have been constructed comprising means for moving the configurators which are capable of automatically replacing them by taking them from an additional magazine, outside the station, thus making it possible to alternate different models on the production line; models to each of which is associated a particular pair of configurators (in general, the work requires one configurator for each side of the line). WO 86/04871 exemplifies this kind of prior art. EP-0-147 910 discloses an automated work station with robot arms. These solutions, however, have various disadvantages such as large dimensions, especially with regard to the magazine, and considerable structural complexity, since they have to move considerable loads (both in weight and in size) and position them with the utmost precision with a relative mechanical apparatus which is always extremely complex and represents an important part of the station. Moreover, in said known systems, moving the configurators, both within the machine, and to and from the additional external magazine, can take a considerable length of time and slow up the production line unless prepositioning is possible. For example, DE-A1-3 144 686 discloses an assembly apparatus with two rotatable elements, each supporting fixture tools on both sides. When change of the car tools occurs, the two elements rotate for facing the proper side to the car body, placed between said elements. The apparatus can handle only two models of car body, but even if some fixture tools were useful for both car models, they would have to be duplicated on both sides of the element. Furthermore, the intrinsic complexity of the system bears very heavily upon both construction and maintenance costs. The general scope of this invention is to obviate the foregoing drawbacks by means of an automatic system for fitting together shaped metal sheets and the like which, although being able to handle different models of manufactured articles, is structurally simple and compact and offers the possibility of rapidly switching from one model to another and of achieving high output rates. This scope is achieved by providing a system for welding metal structures, in particular the bodies of motor vehicles, in a work station, said station being provided with tools for manufacturing said structures comprising positioning and clamping means and, if necessary, welding means, said tools being carried by a pair of opposing units with faced faces locating a space among them in which said structures are fed in succession, characterized by the fact that each unit is a vertical side element rotating around its horizontal upper side to make an inclination movement from a non-operative position, in which a structure is fed in the space between units, to an operative position in which the sets of tools are capable of carrying out work on the structure, each side element supports on a face faced to the other element a plurality of tools, each tool being individually movable from a non-operative retracted position, in which it does not interfere with the structure, to an operative position in which it works on the structure, the tools being grouped together so as to form sets of tools, each set comprising at least two different tools, the sets being disposed along the periphery of the side element, the tools in each set being disposed in a fan-shaped distribution and converging in the direction of the structure between units. The innovatory principles of this invention and its advantages with respect to the known technique will be more clearly understood from the following description of a possible exemplary embodiment using such principles, with reference to the accompanying drawings, in which: figure 1 shows a schematic lateral elevation view of a station using said innovatory principles; figure 2 shows a schematic cross-sectional view along line II-II of figure 1; figure 3 shows a schematic view of a detail of the station; figure 4 shows a schematic view of a first embodiment of a tool holder arm of figure 3; figure 5 shows a schematic view of a second embodiment of a tool holder arm of figure 3. With reference to the figures, the system of a work station, generically indicated by reference 10 and made according to the innovatory principles claimed herein, comprises, as can be seen in figures 1 and 2, a frame 11 supporting a pair of opposing units 12, 12′ which are movable from a first non-operative position (drawn in broken lines in figure 2) to a second operative position (shown by the unbroken line in figure 2). The units 12, 12′ are made to move around their upper side by means of any known system (for example, an electric motor and a screw and nut screw type kinematic chain) and therefore not shown in detail nor further described. As can be clearly seen in figure 2, the units 12, 12′ are suitably spaced apart so that a conveyor line, generically indicated by reference 13, can pass between them for the programmed feeding of motor vehicle bodies 14 to the station (for the sake of simplicity, the station will be hereinafter described with reference to the welding of said bodies, without detriment to the applicability of the innovatory principles claimed herein to stations for welding the most widely varied articles). The station also comprises a plurality of floor-mounted welding robots 17 and portal-mounted robots 18 supported, above the body between the opposing units, by the frame 11. The line 13 and the plurality of robots (if necessary, movable on slides) are per se of the known type and will consequently not be further described. Each unit 12, 12′ carries a plurality of sets 15 of elements 16 suitable for welding a body 14 disposed between said units. The elements 16 are disposed fanwise, each according to its own axis, and are individually controlled. In the embodiment shown herein each set 15 comprises (as can be clearly seen in figure 3) three elements 16 and the axes of each of them are disposed so as to make them converge in the direction of the body. Each element being designed to work on a different type of body, as shown schematically in figure 3. As can be more clearly seen in figure 2, each element 16 is composed of a base 19 secured to the unit and of a movable arm 20, carrying positioning, clamping or welding devices 21. Each movable arm 20 can be made to move by means of various mechanisms which are easily imaginable by any expert in the field. For example, as can be seen in figure 4, a possible embodiment of an element 16 comprises a base 119 connected to a unit 12, and an arm 120 carrying a tool 121 operated by means of an actuator 22. The arm rotates around an axis at one of its ends by means of a linear actuator 23 (of any known type: linear, pneumatic, hydraulic, etc.) whose sliding element 24 carries a plurality of teeth 25 meshing with a toothed wheel 26 integral with the arm 120 so as to form a rackwork. In this way, by operating the actuator it is possible to rotate the arm from a non-operative position (shown by the broken line in figure 4) to an operative position (shown by the unbroken line in figure 4) for working on the body between the units. A second possible embodiment of an element 16 is shown in figure 5. Said embodiment comprises a base 219 connected to a unit 12, and an arm 220 carrying a tool 221 operated by means of an actuator 222. The arm rotates around an axis at one of its ends by means of a linear actuator 223 (of any known type: electric, hydraulic, pneumatic) whose sliding element 224 acts upon a toggle structure 225 connected to the arm 220 and to the base 219. In this way by operating the actuator 23 it is possible to rotate the arm from a non-operative position (shown by the broken line in figure 5) to an operative position (shown by the unbroken line in figure 5) for working on the body between the opposing units. The station as described above operates in the following way. A car body to be worked on is carried by the conveyor system 13 between the units 12, 12′ while the latter are in the non operative position, in which none of the elements carried by them can interfere with the movement of the body. Of the various elements 16 in each set, only those corresponding to the model of car body between the units are rotated towards the body while the others are in their rest position. When the body has reached the correct position between the opposing units, the latter shift into their operative position so that the elements 16 facing towards the body can reach it and work on it as is normal in a work station. On completion of the operations on the body, the opposing units return to their non-operative position and the conveyor system carries the body away and at the same time replaces it with the next one to be worked on. If this body is of the same model as the previous one, the cycle described above is repeated with the same operative elements 16; conversely, if the body is of another model, during the time elapsing between the departure of the body which has just been worked on and the arrival of the next one, new arms of the elements 16 suitable for working on the new body are rotated towards the line and those which are not suitable are rotated outwards into the rest position. Thus, on arrival of the body, the opposing units are equipped with the clamping, positioning and welding tools suitable for it. The advantages of a work station such as the one described above are clearly evident. Even though it is able to handle different models of car bodies, it has limited overall dimensions since there are no configurators magazines or relative handling systems. Moreover, the operating time required for changing the layout of the station from one model to another is reduced and contained within the time required for the conveyor line to replace a body between the opposing units without, therefore, any delay or waiting cycle along the production line. Moreover, the particular disposition of the arms of the elements 16 leading off from the perimeter of the configurators increases the space available for the floor-mounted robots which can be more rationally disposed and have easier access to the areas to be welded. In particular, the fanwise layout, which puts all the space outside the frame at the disposal of the plurality of tools, also enables the tools to be distributed according to their specific dimensions, thus making it possible to simplify the work of the robots and to obtain less tortuous and complicated movements since it is not necessary for them to avoid the obstacles present on the configurators of known technique. This makes it possible to use less sophisticated robots, obtain higher output rates and reduce wear and maintenance due to the simplification of the movements. Lastly, the arms of the robots can be made shorter, thus decreasing vibration, increasing the accuracy of the welding and making it possible to use heavier or larger clamps on them. For example, the movable elements 20 can be made with different shapes and kinematisms from those described for achieving the movement from an operative position to a non-operative position, as can be easily imagined by any expert in the field. The movement of the aforesaid elements 20 to and from said two positions is understood as being rotatory around a real or virtual centre of rotation in any position, in particular with an infinite centre so as to achieve a purely translational motion.

Claims: A system for welding metal structures (14), in particular the bodies of motor vehicles, in a work station (10), said station (10) being provided with tools (16) for manufacturing said structures comprising positioning and clamping means and, if necessary, welding means, said tools (16) being carried by a pair of opposing units (12, 12') with faced faces locating a space among them in which said structures (14) are fed in succession, characterized by the fact that each unit (12, 12') is a vertical side element (12, 12') rotating around its horizontal upper side to make an inclination movement from a non-operative position, in which a structure is fed in the space between units (12, 12'), to an operative position in which the sets of tools are capable of carrying out work on the structure, each side element (12, 12') supports on a face faced to the other element a plurality of tools (16), each tool (16) being individually movable from a non-operative retracted position, in which it does not interfere with the structure (14), to an operative position in which it works on the structure (14), the tools (16) being grouped together so as to form sets (15) of tools (16), each set (15) comprising at least two different tools, the sets (15) being disposed along the periphery of the side element, the tools in each set being disposed in a fan-shaped distribution and converging in the direction of the structure between units (12, 12'). System as claimed in Claim 1, characterized by the fact that each tool (16) comprises a base (19, 119, 219) secured to the corresponding unit (12, 12') and an arm (20, 120, 220) hinged thereto, for supporting the clamping, positioning or welding means, which is movable to and from said two positions by rotation around its end opposite the end supporting said means controlled by an actuating device (23, 223). System as claimed in Claim 2, characterized by the fact that said actuating device is made in the form of a linear actuator (23) connected between the fixed base (119) and the supporting arm (120) by means of a rack (24) and pinion (26) system. System as claimed in Claim 2, characterized by the fact that said actuating device is made in the form of a linear actuator (223) connected between the fixed base (219) and the supporting arm (220) by means of a toggle joint (225).

Inventors: DI ROSA GAETANO, DI ROSA, GAETANO
Applicants: FATA AUTOMATION, FATA AUTOMATION S.P.A.
Application year: 1989
Main classification: B23K37
IPC codes: B62D65, B23K37