MXPA97007675A - Welding device for structural points constituted by metallic elements, particularly outer motor vehicle frames of the mis - Google Patents

Abstract

The present invention relates to a welding station, for example for welding motor vehicle frames, which receives only a part of the structure to be welded from a conveyor line, the remaining components of the structure are assembled with the part at the welding station itself, by means of two positioning gates, which receive the components of the handling robots, the robots are also provided to carry out the point welding of the structure once the latter has been assembled and fixed in an appropriate welding position by the positioning gates. The positioning gates are provided with self-propelled lower trailers guided on rails, in order to be quickly exchanged with another pair of positioning gates adapted to a different type of frame.

Description

DEVICE FOR WELDING MACHINE FOR METAL STRUCTURES POINTS METALLIC CEMENTS, PARTIOITALLY VEJ? CULQ DE .MOTOR Q DESCRIPTION OF THE INVENTION The present invention relates to devices for spot welding structures made of metal elements, in particular frames of motor vehicles or sub-assemblies thereof, of the known type, comprising: a welding station, provided with an automatic means for welding by points, - a conveyor line for feeding the welded structures leaving the welding station in sequence, downstream thereof, at least a first and second locating gates which are rapidly interchangeable in the welding station and devices transport to hold the component elements of the structure to be welded in an appropriate mutual assembly position, the positioning gates are adapted to operate respectively on two different types of structure to be welded, REF: 24725 the location gate which, whenever you are in the area of Work at the welding station can be further moved transverse to the conveyor line between an operative position, in which the clamping devices carried by the gate place the components of the structure which is in the welding station in the position and a non-operative position, in which the positioning gate allows the welded structure to be removed from the welding station, each positioning gate is provided with a self-propelled lower trailer, guided on a rail provided along the length of the floor of the welding station, in order to move between a working position in the welding station and a waiting station, separated from it, so that the station does not have support frames for elements to guide the movement of the placement gates. A device of the type described in the above has been the subject of the application for European patent EP-A-0 642 878 of the same applicant. The latter has been manufactured and sold for years as a flexible welding system, identified with the trademark "ROBOGATE", whose basic concept has been originally described, for example, in U.S. Patent Number 4,256,957 and in the corresponding German Patent Number 28 10 822 which give rise over time to numerous improvements and later variants which also form the subject of the applicant's various patents. The ROBOGATE system has actually determined a shift in the technique of welding motor vehicle frames which had been used until the late 1970s and has replaced the previous equipment used with many vehicle manufacturers around the world. In the basic version of this system, it is constituted by two or more pairs of positioning gates which can be quickly exchanged in the working position in the welding station and placed to operate in the respective types of frames. The system is capable of operating on the frames on which they are even very different from each other, so that the same line can be used for the production of different models. An additional advantage of the ROBOGATE system is that it can be adapted in relatively simple and fast operations and therefore with very small investments for the production of a new frame model. Another advantage is based on ensuring a uniform quality in all models of the same type on which the system operates.

The prior art constituted by the ROBOGATE system establishes that each frame to be welded reaches the welding station in a loose preassembled condition. Actually, upstream of the ROBOGATE welding station, one or more rectification stations are provided, in which the various elements constituting the frame are loose assembled together by bending connecting tabs. This provisional connection is, naturally, a loose or loose connection, that is, allows small movements of each element with respect to the adjacent elements. Precisely for this reason, the positioning gates provided in the welding station have clamping devices which couple the various parts of the frame in order to hold them in the proper assembly position before the welding points are applied by the robots which usually constitute welding means provided in the station. Once several welding points (in one or more ROBOGATE stations) sufficient to provide the frame with a stable geometry have been applied to the frame, the frame advances to the following stations to complete the welding, which does not require the use of clamping devices.

Subsequent to the patents mentioned in the above, the applicant has submitted additional patents related to various versions and improved developments of the ROBOGATE system. At least one of these improvements has been the object of the European patent application EP-A-0 642 878 which has been mentioned before. This document describes a welding station which has a structure much less complicated, lighter and more flexible with respect to the previous modalities of the ROBOGATE system. In most conventional solutions, the positioning gates are slidably guided in order to allow them to be quickly exchanged in the working position with the gates provided for a different type of frame to be welded, on guides upper directed parallel to the direction of the conveyor line in the welding station, which requires providing strong fixed support frames. These frameworks, in addition to greatly contributing to the cost and volume of the welding station, also make it difficult for welding robots to find the necessary space to operate in the frame to be welded. In the solution described in European patent application number EP-A-0 642 878, each positioning gate moves separately from the other gates so that it is provided in its lower part with a self-propelled trailer which is guided in a rail provided along the floor of the welding station. Therefore, the positioning gates do not need to provide longitudinal guides which extend across the entire length between the working position and the waiting position, and therefore do not require providing a heavy and bulky supporting frame, constituted by gangway or gantry structures connected to each other longitudinally, which are necessary in the classic solutions for ROBOGATE. Therefore, the space available for the welding robots is greatly increased, which also allows, if desired, to increase the number of robots in order to obtain an increase in the welding points applied during an interval of certain time. The robots themselves can have easier access to all the parts of the frame to be welded in order to carry out the appropriate welds. In addition, since each positioning gate moves separately from the other gates, the passage between each gate and the subsequent gate on the line is free and variable, which provides great flexibility in the design and installation of the plant. In addition, the installation of the plant is of a lower cost compared to conventional plants.

The method which is described in the European patent application mentioned before EP-A-0-642 878 relates to a case in which all the components of the structure are to be welded, in the specific case of a vehicle frame of motor, which are placed in the welding station from the conveyor line, which has a means of support for any type in which the various components of the frame are suspended in positions close to each other. When the components of a frame to be welded reach the welding station, the positioning gates close on these components and place them in the appropriate assembled position, in which the robots carry out the welding points. However, the use of positioning gates provided in their lower parts with self-propelled trailers with the possibility of eliminating conventional fixed support structure in the welding station, opens the possibility for designers to provide welding stations which also operate according to different criteria, and at the same time maintain the same advantages of the solutions which have been described before. This is valid in the case of both the structure on which the system must operate on a complete motor vehicle frame, as in the case where only a single sub-assembly of the frame is used. The aim of the present invention is to further improve the known systems mentioned above and at the same time to take advantage of their advantages. A first basic characteristic of the welding devices according to the present invention is based on the fact that the conveyor line whenever it supplies only a part of the structure to be welded to the welding station and the device further comprises manipulating means for lift the component elements remaining in the structure to be welded from the respective load poles, the elements of the remaining components are to form the structure together with the part of it which is already in the welding station, when placing it in the conveyor line, the handling means is adapted to supply the remaining components lifted from the loading posts to the positioning gate which is in the welding station, and the positioning gate is adapted to receive and hold these components by its fixing means, so that when the positioning gate is located n its operative position causes the components held in it to be assembled with the part which is already in the welding station, so that it places the complete structure for welding. Due to the features, the frame assembly operation is further simplified. Instead of the grinding stations which, when provided in most of the conventional solutions upstream of the ROBOGATE station, in order to form a loose preassembled frame before the welding is carried out, they eliminate completely. In addition, the conveyor line is simplified and costs are reduced, also with respect to the modality shown in European patent application EP-A-0 642 878, since the complete structure is formed solely from its unique components in the welding station, and not upstream of it. Preferably, the automatic means for spot welding comprise programmable robots provided with welding heads and also constitute "handling means which supply the components of the structure to be welded to the positioning gate which is in the station. of welding, the robots are provided with interchangeable handling tools with the welding heads.In the case where the structure to be welded is a motor vehicle frame, the lu-device according to the invention is characterized because, according to a technique known per se, two pairs of positioning gates are provided on the two sides of the conveyor line, which are rapidly interchangeable in the welding station, the gates of the pair which is in the station of welding are closed together in the operative position and are separated from each other in the position In this case, the conveyor line supplies the welding station with the floor of the frame to be welded, while the positioning gates receive two respective side panels from the handling means, side panels which are for forming the frame to be welded along the floor, as well as with one or more transverse members which connect the two side panels at the top. According to a further preferred feature, at least one of these transverse members, which form the frame, is transported by a transverse structure similar to a bridge which is mounted so as to connect the upper parts of the two lateral gates to each other. when the latter are in their closed operational positions. Such transverse structures are in fact also provided with clamping devices in order to hold and position the respective transverse member of the frame.

In addition, according to a further preferred feature, means are provided for exchanging the pair of positioning gates which are in the waiting position with an additional pair of positioning gates, corresponding to an additional type of the frame to be welded , which is taken by a deposit or feeder of additional positioning gates corresponding to different additional types of the frame. Due to the characteristics indicated above, the system according to the invention maintains all the advantages of the ROBOGATE system, and the system forms the subject of the application for European patent number EP-A-0 642 878. At the same time, the system is It also improves from the point of view of simplicity and standardization of the plant. In particular, in the case of the present invention, the various components of the structure to be welded are assembled together, to carry out welding at the welding station itself, if the need to provide a conveyor line which feeds the entire structure to be welded in the station, since the positioning gates also fulfill the function of adopting or taking the elements of the structure of the handling robots and bringing these elements to the assembly position, in the that the positioning gates themselves are provided for fastening, for welding. Characteristics and advantages of the invention will become apparent from the description which follows with reference to the accompanying drawings, given solely by way of non-limiting example, in which: Figure 1 is a cross-sectional view of a station welding according to the invention, and Figure 2 is a plan view of the welding station of Figure 1. In the drawings, the reference number 1 generally designates a welding station according to the present invention, which is for frames of frame motor vehicles made of metal elements by spot welding. The term "structuring" as used herein means the application of several sufficient welding points to provide a stable geometry to the frame. Of course, it would be possible to provide more than one station type station 1 in order to carry out the structuring. In fact, it is possible to provide a single station for structuring the entire frame of the motor vehicle, or, for example, two stations in sequence, one of which is used to structure the internal structure of the frame, while the other serves to structure the outer elements of the frame in the internal structure of the frame. When the structuring operation has been completed, the frames are caused to advance, in a manner known per se, to additional stations to complete the welding, which has a much more simplified structure, since they do not require fixing devices to retain the elements to be welded in the proper welding position. In the case of the illustrated example, the welding station 1 is for operating with two different models of the frame. However, the invention can also be applied to the case in which a station is adapted to operate in more than two different models, since it is generally necessary to provide several pairs of positioning gates equal to the number of models involved. A conveyor line for transporting the floor panels 3 of the frames 4 to be welded in sequence through the welding station 1 is diagrammatically shown by the reference number 2. The specific structure of the conveyor line and the details of construction thereof can be made by any known method that are not found, when taken together, within the scope of the present invention. For this reason, these details are not described herein and are not shown in the accompanying drawings, so that they make this document easier to understand. By way of example only, Figure 1 shows the case in which each floor panel 3 is transported on a support platform or pallet 5 which is provided with means for fixing the floor panel in a precise position at the floor station. welding. In the two sites of the conveyor line 2 (see also figure 2) there are provided, according to the technique known per se, two pairs of positioning gates 6L, 6R and 7L, 7R provided with fastening device adapted to place the component parts of two different types of frames to be welded properly in the welding station. Furthermore, according to the technique known per se, the two pairs of gates 6, 7 are rapidly interchangeable by the longitudinal movement thereof on both sides of the line, so that each pair of gates can move between one position of work in the welding station and a standby position separated from it respectively upstream or downstream of the welding station (figure 2). The structure of the positioning gates 6, 7 can be made in any known manner, but is preferably of the type that is illustrated in the previous European patent application EP-A-0 642 878 of the same applicant. A further feature of the invention is additionally based on the fact that each of the positioning gates 6, 7 is provided with a self-propelled lower trailer 8 which is guided on a respective longitudinal rail 9 placed parallel to the conveyor line 2 in both sides of the welding station. The construction details of the self-propelled trailer 8 and the rail 9 are not illustrated here for purposes of simplicity since they are of the same type as those illustrated in the European patent application mentioned before the same applicant. Due to this feature, as already described above, the positioning gates 6, 7 can be moved to provide the exchange in the welding station, as a function of the type of the frame which is in the welding station, without bulky, heavy and complicated support frames are required which are provided in the classic ROBOGATE stations, in order to guide the movement of the positioning gates. Still with reference to Figure 1, the movement of the positioning gates 6, 7 on the rails 9 takes place when these composite are in their separate non-operative position, shown with a dashed line in Figure 1. As indicated in the European patent application mentioned above, of the applicant, the rails 9 have separate sections in the welding station which allow transverse movement in the conveyor line to carry the two positioning gates 6 or 7 which are in the welding station from their separate non-operative positions, which are shown with a dashed line in Figure 1, to their closed operative positions, which are shown with a continuous line in Figure 1, in which the fastening devices (not shown) are provided, in a manner known per se, for these gates, which can couple different components of the structure to be welded to hold them and n the proper welding position. As already described above, the conveyor line 2 only transports the floor panel of the frame to be welded to the welding station. The assembling of the frame to be welded is completed in the welding station itself, since in this station there are provided programmable manipulation robots 10 of any known type, capable of lifting the various components of the two side panels of the frame from the loading posts 11 and for supplying these components to the two positioning gates 6 or 7 which are in the welding station in their inoperative positions, separated. In this condition, each positioning gate receives the various elements that receive the respective side panel of the frame and hold it by the respective holding devices, so that each side frame panel is preassembled in the positioning gate. At this time, the two positioning gates move towards their closed operative positions in which they carry the respective side panels assembled thereon to a position for assembly with the floor panel 3. The frame to be assembled is completed with one or more transverse members 12 connecting the two side panels 13L, 13R at the top. Each transverse member 12 is supported by a transversal structure similar to a bridge which is placed by one of the handling robots 10 above the two positioning gates 6 or 7 when the latter are in their closed operating portions, by means of the clamping devices 14 of the same type as the clamping devices provided by the positioning gates 6, 7. The ends of the transverse structure 15 are connected to the upper parts of the two positioning gates 6 or 7 by means of automatic quick coupling devices. It should be noted that in the applicant's prior European patent application, which has been mentioned above, the use of a transverse structure to connect the two positioning gates in the operative condition is also described. However, one of the features of the present invention is based on the fact that this transverse structure is also used to transport the clamping devices 14 that make it possible to support a transverse member that forms part of the frame to be assembled. Once the structure of the frame has been assembled in the welding station, with the various components of the frame fixed in a precise position by means of the fastening devices provided in the positioning gates and in each bridge-like structure, the The same handling robots 10 carry out various spot welding, naturally after they have changed their handling tool with a welding head, with a fully automated technique, known per se. Naturally, it is also possible that the handling robots 10 mount each side panel of the frame already completely assembled, by a single operation, in a respective positioning gate, in order to allow the latter to bring the side panel to the condition for assembled with the frame floor panel. Once the frame has been welded, the positioning gates again open and return to their operative positions shown with a dashed line in FIG. 1, to allow the conveyor line 2 to feed the welded frame downstream of the station of welding and to bring a new floor panel inside the welding station. If this panel belongs to a different type of frame from the previously welded frame, the entire new floor panel inside the station occurs simultaneously with a change of the two pairs of positioning gates in the welding station. This exchange takes place since the lower self-propelled trailer of each positioning gate moves along the respective rail 9. In this way, the positioning gates which previously are in their working position are moved to their waiting position and The other pair of positioning gates enters the welding station. According to a technique also known per se, when the two positioning gates are in a waiting position, separated from the welding station, they can be exchanged with additional pairs of raised positioning gates of auxiliary deposits of positioning gates, for example, in accordance with what is illustrated in the British patent application GB-A-2 172 555 for the same applicant, in which additional deposits of positioning gates provided in a fan-like arrangement are provided, which allow the welding station is adapted to operate in many different types of frames (for example 8). From the previous description, it is clearly evident that the device according to the invention takes up all the advantages of the ROBOGATE system and the system shown in the application for European patent EP-A-0 642 878, and at the same time simplifies and normes the additional use of the welding plant. The system itself allows its use in the case in which it is necessary to start the production of a new car model initially in a single version, while anticipating the introduction of an additional version within a predetermined time; in this case, the plant is initially installed with a single pair of positioning gates, but is subsequently provided with self-powered lower trailers in any way which are coupled to the floor rails, so that it becomes easy to adapt the device for a second Rack version by introducing an additional pair of positioning gates. Under this aspect, a system is provided in which a way described above (a single pair of positioning gates with self-propelled racks mounted on the rails) would present an equivalent production of the device of appended claim 1, since it is clearly evident that trailers and rails must be used in order to allow the insertion of a second pair of interchangeable positioning gates. Naturally, although the principle of the invention remains the same, the details of construction and embodiments may vary widely with respect to what has been described and illustrated by way of example only, without departing from the scope of the present invention. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (7)

1. A device for spot welding of structures consisting of metal elements, particularly frames of motor vehicles or sub-assemblies thereof, the device is capable of operating in at least two different types of structures, for example, two different models of a frame , the device is characterized in that it comprises: - a welding station, provided with an automatic means for spot welding, a conveyor line for feeding the welded structures that leave the welding station in sequence, downstream thereof, - by at least one first and second locator gates which are quickly interchangeable in the welding station and transport devices for securing the component elements of the structure to be welded in an appropriate mutual assembly position, - the positioning gates are adapted to operate respectively in two different types it is of structure to be welded, the locating gate which, each time it is in the work area in the welding station can be further moved transversely towards the conveyor line between an operative position, in which the clamping devices carried by the gate place the components of the structure which is in the welding station in the appropriate mutual position, and a non-operative position, in which the positioning gate allows the welded structure to be removed from the station of welding, each positioning gate is provided with a self-propelled lower trailer, guided on a rail provided along the floor of the welding station, in order to be able to move between a working position in the welding station and a station waiting, separated from it, so that the station does not have support frames for elements that guide the movement of the positioning gates, the device is characterized in that the conveyor line only feeds a part of the structure to be welded to the welding station, and also because the device comprises manipulation means for lifting the additional elements that constitute the structure to be welded to the respective load poles, the additional elements are to form the structure together with the part which is in the welding station when carried to it by the conveyor line, the handling means is capable of supplying the components lifted by the positioning posts to the positioning gate, which is in the welding station, and the positioning gate is capable of receiving and supporting these components by means of its fixing means, so that when the gate is brought to its operative position, allows these components to be transported in the same to be assembled with the part which is already in the welding station so that it places the whole structure for welding.

2. The welding device according to claim 1, characterized in that the automatic spot welding means comprise, in a manner known per se, programmable robots provided with welding head, and also because the robots also constitute handling means which supply the components of the structure to be welded to the positioning gate which is in the welding station, the robots are provided with interchangeable handling tools with the welding heads.

3. The welding device according to claim 2, characterized in that the device is used to weld frames of motor vehicles, the device is characterized in that in a manner known per se, two pairs of positioning gates are provided on the two sides of the device. The conveyor line which are quickly interchangeable in the welding station, the gates of the pair which is in the welding station are close to each other in operative position and are separated from each other in the inoperative position, and in addition the conveyor line feeds only the floor panel of the frame to be welded to the gate station, whereby the pair of positioning gates, which is in the welding station, receives two respective side panels which are to form the frame to be welded from the handling means.

4. The welding device according to claim 3, characterized in that the frame to be welded comprises one or more transverse members which are connected to the side panels in the upper part and in which at least one of the Transverse members, which form the frame, are transported by a transverse structure similar to a bridge which is assembled in a manner that connects the upper parts of the positioning gates when the latter are in their closed operative positions.

5. The welding device according to claim 4, characterized in that the transverse structure to bridge is also provided with clamping devices in order to hold and position the respective transverse member of the frame.

6. The welding device according to claim 5, characterized in that the transverse structure similar to bridge is provided in order to be transported and mounted on the positioning gates by the handling robots.

7. The welding device according to claim 1, characterized in that means are provided for exchanging the pair of positioning gates which is in a waiting position, with an additional pair of positioning gates corresponding to an additional type of frame that is going to be welded, - which is taken by a deposit or feeder of different placement gates corresponding to different types of frame.