Patent Application
20060169398
The invention relates to a method and a device for automated application of lacquer film to bodywork parts. The invention is based here on the applicant's earlier patent application, according to German Offenlegungsschrift DE 102 30 034 A1, which was not published before the priority date. A method considered to be known from this document is reproduced in the precharacterizing clause of claim 1 and a corresponding device is reproduced in the precharacterizing clause of claim 16. The invention also relates to the use of an adhesive strip.
On vehicles, it is often intended for stylistic reasons to cover the surface of the bodywork lying between two neighboring areas of glass with a lacquer film that is black or dark-colored, irrespective of the color of the rest of the car, and often has a high-gloss finish, in order in this way to give the impression of a continuous glass surface at this location. To be precise, the two neighboring vertical frame members of the window frames in the region of the center pillar of the vehicle come into consideration here in particular—but not only these. On vehicles with a lamella roof or glass roof, it is also popular for stylistic reasons for the horizontally lying bodywork strip above the windshield to be provided with a dark-colored lacquer film, in order to create the visual impression of a uniformly continuous area here too. In the case of side application of the lacquer film, it is applied to the frame members of the window frame of the side doors. Since these areas of the bodywork generally represent only narrow strips, the blank of the lacquer film to be applied is also correspondingly shaped in an elongated manner and not particularly large. Since the lacquer film remains on the vehicle during the entire time it is in use, the lacquer film must correspondingly be adhesively attached permanently to the bodywork, account having to be taken of the fact that the side members to be covered in this way are in the direct field of view of the vehicle users, at least when they are getting in, and consequently the requirements for a satisfactory film application are particularly high.
For the automated application method known from the earlier patent application cited at the beginning (DE 102 30 034 A1), a three-layer film composite suitable for the purpose is
proposed, bearing an area-covering protective film or protective paper on each of both sides of the actual lacquer film blank. For the machine handling of the elongated film composite, a so-called tab is attached to both its ends, i.e. the protective film strips overhang at the ends. At these overhanging tabs, the film composite is grasped by means of controllable flat suction grabbers of a robot tool from a flat readiness position, the suction grippers being tilted out of the take-up plane after taking up the film composite. The tilting away of the suction grippers allows the film composite, which is kept stretched and is to be applied to the bodywork by a doctor knife, to be pressed out from the take-up plane in a V-shaped manner, without the contact area on the suction grippers being partially exposed. In addition, a second, separate tab, which projects beyond the first tab, is provided at one end of the film composite for the adhesive-side protective film. Using this further tab, the adhesive-side protective film can be removed from the film composite, i.e. the adhesive side of the lacquer film can be exposed, in an automated manner before the actual lacquer film application.
Although, to the knowledge of the applicant, it is possible for the first time with the technology according to the earlier patent application DE 102 30 034 A1 to apply lacquer films to bodywork parts in an automated manner, which apart from the advantage of providing relief from strenuous and monotonous manual work has the further, major advantage of lacquer film application that is always positionally accurate and free from bubbles and folds, it has been found on the other hand that the earlier technique still has the following disadvantages:
The required robot tools are complex and correspondingly susceptible to requiring maintenance, which is reflected in investment and maintenance costs. Since, because of the multiplicity of application locations on a vehicle model and the requirement of a reserve tool for each application location, a relatively large number of robot tools are simultaneously required, the expenditure is correspondingly higher.
Conversion of the robot tool to changed formats of the lacquer film blank is only possible to a very restricted extent. The robot tools therefore could not be used in a wider range of film formats.
A vacuum in the robot tool for handling the lacquer film composite is not entirely unproblematical from aspects of construction and control technology (large line cross sections, voluminous valves), which restricts the robot tool in the freedom of movement.
The prefabricated lacquer film composites must have on both opposite narrow sides relatively long, three-ply “tabs”, which have the same ply structure as the actual lacquer film blank, to be specific (from bottom to top) an adhesive-side protective strip, a lacquer film and an outer protective strip. As a result, each individual lacquer film composite is relatively expensive, which is reflected in a relatively high material price.
The pulling-off of the outer protective strip after the application of the lacquer film and the depositing of this protective strip in a waste container takes time and adversely affects the cycle time. Furthermore, the rolling-up protective strip represents very voluminous waste, which takes up considerable space in the application station.
The object of the invention is to improve the method and the corresponding device of the generic type that are taken as a basis to the extent that these disadvantages are avoided. It is therefore intended by the invention that
more simple, and consequently less costly, lacquer film composites can be processed in an automated manner,
the robot tools can be made more simple, and consequently less costly,
conversions of the robot tools to different lacquer film formats are possible without any problem,
the robot tools are not restricted in their mobility by voluminous peripheral components and
the volumes of the protective strips occurring as waste are reduced.
Taking the application method and the corresponding device of the generic type as a basis, this object is achieved according to the invention by the characterizing features of claim 1 (method) and by the characterizing features of claim 16 (device). According to the invention, furthermore, the use of a virtually endless, wound-up adhesive strip as an outer protective strip is proposed for the automated taking-up and application of self-adhesive lacquer film blanks to bodywork parts (claim 27).
According to the latter, the upper film composite is handled by an adhesive strip located in the robot tool. A piece of adhesive strip that is kept stretched in the take-up plane of the application tool can be used repeatedly and can be easily renewed as and when required. In an expedient way, the adhesive strip is pulled from a supply roller secured in the tool, passed through the take-up plane of the robot tool over a pair of deflection rollers and wound up after use on a take-up roller likewise secured in the tool. This adhesive strip not only undertakes the secure holding of the lacquer film during the film application, but also replaces the outer protective strip previously attached on the outer side of the lacquer film composite. This makes it possible to dispense with voluminous vacuum hoses and vacuum valves, restricting the mobility. There are no longer any complex, tiltable suction grippers, which adversely affect the convertibility of the application tool to other film formats. With the adhesive strip, any desired formats of lacquer films can be readily taken up and securely handled. The novel, now only two-ply, lacquer film composite is also of a simpler form than previously and the lacquer film is transferred from the adhesive strip into the application tool directly on its exposed visible side. Since a number of clean lacquer films can be taken up by the adhesive strip one after the other, the adhesive strip need not be renewed after each application operation; rather, renewal after repeated use is sufficient. In the case of a virtually endless adhesive strip, the renewal may take place at intervals, i.e. by displacing the adhesive strip by an entire length of lacquer film after a specific number of application operations. Instead, the stretched adhesive strip may for example also be renewed by an incremental advancement of the adhesive strip by merely a small fraction of the length of the lacquer film after each application operation. The consumption of protective film is therefore much less than in the case of the old technology and the consumed protective film in the case of a virtually endless adhesive strip is wound up inside the robot tool in a space-saving manner. To this extent, no voluminous waste is created. Moreover, the two-ply lacquer film composite now only has at one end of the adhesive-side protective strip a tab by which the protective strip can be pulled off the lacquer film blank; the film composite is therefore also made simpler in this respect than the case of the older technology.
Further expedient refinements of the invention can be taken from the subclaims; moreover, the invention is further explained below on the basis of various exemplary embodiments that are represented in the drawings, in which:
Firstly, the overall view of an application station according to
The method according to the invention for automated application of self-adhesive lacquer film to bodywork parts presupposes that the self-adhesive lacquer films to be applied are prefabricated in blanks 6 and that these blanks are formed appropriately for handling. In order to allow the prefabricated lacquer film blanks 6 to be transported and handled in an automated manner, they must be respectively provided on their adhesive side with a sticking, but easily removable, protective strip 8, that is to say be contained in a two-ply film composite. Furthermore, the tab 10, 10′ projecting beyond the usable length L of the lacquer film blank 6 on the adhesive-side protective strip is important for automated application of the lacquer film blank. Such a tab is necessary in the present case merely in the region of a single narrow side at the end of the blank, in order to allow the adhesive-side protective strip to be pulled off. For the handling of the film composite as a whole in a way that is appropriate for automation, however, no further tabs are required.
Represented in the drawings (
In connection with the technique according to the invention of taking over and handling the film composites in or by the application tool, the film composite must be presented on the table 18, 18′ on a hard, flat base 27, and be securely held on it so as to lie flat. Therefore, the film composites cannot be offered in a stack, but must first be individually separated. For this purpose, in the case of the exemplary embodiment represented at the top in
Represented in the lower part of
On this table, a number of compartments 13 are arranged in parallel next to one another, laterally offset in relation to the base 27, for the presentation of an individually separated film composite, which compartments can in each case take relatively large stacks of film composites. This would also make it possible to stock different lacquer films for a production mix. The compartments 13 on the one hand and the base 27 on the other hand are at the same distance as one another from a side edge of the table. Apart from the compartments and the base, a transfer device 16′ with two Cartesian axes of movement is arranged and can be used in each case for removing a film composite from one of the compartments 13 and depositing it on the base 27. For this purpose, a horizontal guide running parallel to the table edge is provided for a carriage with a corresponding movement drive and a vertical guide is provided on the carriage for a flat suction gripper for taking up a film composite. The compartments 13 can take a relatively large number of film composites, so that manual refilling of the same is required only at relatively great time intervals.
The positionally defined presentation of the film composite for takeover by the handling robot can therefore take place in various ways, including ways not even described here, and also in different positions. What is important is firstly that the position of the film composites to be taken over that is precisely defined by mechanical stops or the like does not change during the takeover. In addition, the film composite must rest on a hard, level base, in order that it can be taken over into the application tool by doctor blading by means of a doctor knife integrated in the tool. Therefore, the film composites 5 must be offered individually, and preferably in a horizontal position, to the application tool for takeover. This is so because the two-ply film composites have a tendency, because of the dissimilar plies, to curl up, in particular on account of the different temperature- and/or moisture-dependent elongation of the two plies. Under some circumstances, electrostatic forces acting between the tool-side adhesive strip on the one hand and the presented film composite on the other hand could lead to an unwanted change in position of the film composite.
In order to be able to present the film composite satisfactorily on the table in spite of such a tendency to curl up and in spite of electrostatic forces, the film composite is forcibly held securely in a flat position, which takes place in the case of the exemplary embodiment represented in the figures by the hard base attached on the table 18, 18′ being formed as a suction box 19, which for its part can, via a connection 45, have a vacuum applied to it as and when required, i.e. for holding the composite in place, or have air admitted to it for releasing it. The upper side of the suction box forms the hard level base 27. In order that, when applying the tool-side adhesive strip by the doctor knife to the securely held film composite, edges of bores in the upper wall of the suction box cannot leave an impression on the sensitive lacquer film blank 6 through the adhesive-side protective strip 8, the upper wall of the suction box is only provided with suction bores in the edge region, which lie in the region of the lacquer film that is in any case folded around after the application.
Attached to one end of the suction box or the base is a holding arm 44, which in the case of the exemplary embodiment represented in FIGS. 2 to 5 carries at its free end a small suction bar 36, which can be subjected to a vacuum or have air admitted to it parallel to the suction box. The upper side of the suction bar, where the suction is effective, lies flush with the upper side of the base 27. The extreme end of the tab 10 or 10′ is securely held by the suction bar, whereas the main part of the tab is stretched out freely and is consequently accessible for a gripping tool from above and below and also transversely from the sides. At this point, it should already be mentioned in advance that, in the case of the more simple variant of the suction box that is represented in
Before the method according to the invention for application of the self-adhesive lacquer film is to be discussed, first the application tool 20 shown in different phases in FIGS. 2 to 5 is to be presented in its significant details.
The application tool that is shown in various exemplary embodiments 20 (
A supply roller 30 and a take-up roller 33 for new adhesive strip and used adhesive strip, respectively, are mounted between the rear side and the working side of the application tool 20, 20′—likewise fixed in place therein—in such a way that they can be exchanged quickly as and when required. The take-up roller 33 is fitted in a rotationally fixed manner on a drive shaft 34, which can be driven with a presettable torque by a drive motor 35, its drive being formed altogether in such a way that, even at a standstill, the take-up roller 33 can be driven in the sense of winding up the adhesive strip and can also be braked completely to a standstill. The supply roller 30 is fitted in a rotationally fixed manner on a braking shaft, which can be braked by a brake 32 with a predeterminable braking torque.
With regard to the possibility of the adhesive strip laterally running askew through the take-up plane, which is encouraged in particular by the doctor blading of the lacquer film blank, the take-up roller is mounted in the application tool in an axially displaceable manner, so that it is able to follow an adhesive strip that under some circumstances is displaced laterally. For the automation of an orderly winding-up of the used adhesive strip, the position of the side edge of the adhesive strip is detected in the end region of the take-up plane lying turned toward the take-up roller. Furthermore, a servomotor-effected side adjustment of the take-up roller is to be provided, activated in dependence on the detected side offset of the used adhesive strip. This allows the used adhesive strip to be wound up in an orderly manner.
In order to be able, as and when required, also to pull off small lengths of adhesive strip smoothly from the supply roller, a compensating roller 70 is arranged in the run-off of the adhesive strip from the supply roller and is wrapped around at approximately 90°. The compensating roller, which is mounted in a radially displaceable manner in relation to the supply roller in a guide 71, can unforcibly follow the changes in diameter of the supply roller which the latter undergoes in dependence on the use of adhesive strip. The compensating roller bears with a certain prestress against the outer circumference of the supply roller. For this purpose, the compensating roller is stressed in the direction of the supply roller by means of a spring 72.
On account of the compensating roller 70, even relatively small lengths of adhesive strip can be smoothly pulled off downward. For the case in which the piece 76 stretched in the take-up plane 21 is to be held unyieldingly, or in such a way that it yields only after overcoming a specific limiting force, not only the supply roller itself and the take-up roller 33 are able to be braked with a higher securing force, but under some circumstances the compensating roller 70 can also be fixed by a brake within its radial displaceability 71, which however is not indicated in the drawing.
The strand of the adhesive strip running from the compensating roller is guided onto the first deflection roller 37b and is deflected by it into the take-up plane 21. After running through the take-up plane, the second deflection roller 37a is reached, which deflects the adhesive strip to the take-up roller 33. In the piece 76 of the adhesive strip that is stretched in the take-up plane 21, its adhesive side faces downward, which is important for the function of the application tool.
When unwinding adhesive strip from the supply roller, electric charges can be released in the pulled-off adhesive strip and can attract dust particles from the surroundings and allow them to be deposited on the surface, which would be disruptive during the doctor blading. In order to reduce this risk, it is expedient if the compensating roller 70 is superficially electrically conductive and in this respect electrically grounded. It is alternatively or additionally also conceivable to discharge and render harmless an electric charge from the pulled-off adhesive strip by means of a narrow grounded brush of long, soft, electrically conductive fibres.
Also arranged in the application tool alongside the one deflection roller 37a, shown on the left in FIGS. 2 to 5, is a parallel-displaceable gripping tool 50, which is represented on its own in
In the case of the exemplary embodiment that is represented, the drive block of the gripping tool comprising the angular gear mechanism 54 and the motor 55 is coupled by means of parallelogram links 56 to a carriage 59, so that the drive block or the long-nose pliers can be displaced in a translatory manner on an arc of a circle from the starting position, represented in
As far as the position of the gripping tool or the long-nose pliers with respect to the spatial depth in relation to the plane of the drawing of the various representations of the application tool is concerned, it should be noted that the gripping tool lies in the same region in which the already mentioned deflection rollers 37a, 37b and the piece 76 of the adhesive strip tentered by them lie. In the same region there is also the doctor knife 39 described further below, which is carried by a separate carriage 42 and with which the tentered piece 76 of the adhesive strip is doctor-bladed to the film composite 5 presented when it is taken up and with which the lacquer film is doctor-bladed to the bodywork when it is applied. The drive block 54/55 for rotating the gripping tool must therefore lie in a plane on the far side of the gripping tool, deflection rollers, film composite and carriage 42.
In principle, it would also be conceivable to displace the movable gripping tool only linearly within the working plane for grasping the end of the adhesive-side protective strip and for pulling off the same from the film composite—apart from changing the gripping tool from the starting position into the working plane—and to dispense with a complex rotary drive of the gripping tool. However, at least with the desire for a tool-integrated, application-simultaneous pulling-off of the protective strip, this would presuppose that the linear stroke of the gripping tool guided in such a way corresponds at least to twice the length L of the latter film blank that is to be applied; furthermore, the gripping tool guided in such a way would have to be driven at twice the speed of the carriage 42, which carries the doctor knife 38/39. This would presuppose a considerable structural length of the application tool, which makes the latter heavy and unwieldy. Therefore, in the exemplary embodiment represented, the movably mounted gripping tool is—as stated—formed at the same time as a winding device, so that it can be moved at the same speed as the doctor knife 38/39, but nevertheless allows the adhesive-side protective strip to be pulled off from the lacquer film application-simultaneously.
To be specified as a further structural component of the application tools 20, 20′ or 20″ that is important for the method is the already mentioned doctor knife 38, 39, which comes into action both when the film composite is taken up and in the actual application phase. It is movably arranged in two respects and is provided with a corresponding displacement drive. On the one hand, the doctor knife can be displaced with its working edge out of a waiting position represented in
In order that, irrespective of a tool-side positioning in relation to the bodywork part, the doctor-knife blade is able unforcibly to follow the transverse inclination of the latter, the doctor-knife blade 39 is pivotably mounted in the doctor-knife holder 38 in two respects, which is indicated in more detail in
For adjusting the doctor knife, the carriage-like doctor-knife holder 38 is displaceably mounted on a carriage guide 40, which is inclined in relation to the take-up plane 21, and is provided with a corresponding adjusting drive 41 in the form of a working cylinder, which also applies the pressing force of the doctor knife. On the other hand, in the working position, the doctor knife can be displaced in a rectilinear manner and parallel to the take-up plane 21. In order to permit this, in the case of the exemplary embodiment represented, the carriage guide 40 is for its part arranged on the already mentioned carriage 42. The displacing drive 43 allows the carriage or the doctor knife 39 to be displaced parallel to the working plane 21, it being possible for a doctor-blading operation to be performed with a specific linear pressure.
Before discussing the application method and the mode of operation of the application tool, an auxiliary device, which is arranged in a stationary manner alongside the base 27 or the suction box 19 for the preparation of a film composite to be taken up and is intended for the specific detachment only of the adhesive-side protective strip from the film composite taken up in the application tool, is to be explained with respect to its construction. In order to understand that such an auxiliary device is very expedient in the present case, it should on the one hand be recalled that the taken-up lacquer film blank 6 of the film composite adheres with only a moderate adhesive force to a piece 76 of the adhesive strip 31 that is stretched in the working plane 21 of the application tool. On the opposite side of the lacquer film blank, the protective strip 8 adheres to the adhesive side of the lacquer film blank, it being possible under some circumstances for this adhesive force to be greater than the adhesive force of the adhesive strip on the visible side of the lacquer film blank in spite of an anti-adhesive coating on the protective strip, especially since the adhesive strip is to be used repeatedly and the adhesive force thereby subsides from time to time. With the auxiliary device it is therefore intended to ensure that, when the tab 10 is pulled off from the taken-up film composite, only the adhesive-side protective strip 8 is detached from the taken-up lacquer film blank and the latter in every case remains adhering to the adhesive strip 31.
The auxiliary device for the specific pulling-off of the adhesive-side protective strip substantially comprises a movable counterstay tongue 46, which is mounted at a vertical distance from the base 27 and parallel to it. It is fastened by one end at the top to a vertical holder 47 and is mounted in a horizontally pivotable manner. By means of a pivoting drive (not represented), it can be pivoted out of the rest position, shown in
When the adhesive-side protective strip 8 is pulled off by the tool-integrated, movable gripping tool 50, the protective strip is pulled over the rounded edge of the counterstay tongue 46, as represented in an enlarged form in the lower part of
In connection with the mode of operation of the application device, it should initially be mentioned that, in preparation for the application of the lacquer film, first the film composite presented by the presentation robot 16 or transfer device 16′ on the base 27 or the suction box 19 has to be taken up in the application tool 20. In the case of the merely two-ply, presented film composite, the bare visible side of the lacquer film blank 6 is freely accessible. For taking up the film composite, the application tool is held with the take-up plane 21 a small distance above the presented film composite and, subsequently, the stretched part 76 of the adhesive strip is doctor-bladed by means of the tool-integrated doctor knife 39 from the position at a distance onto the unyieldingly held film composite, whereby the latter is adhesively attached firmly to the adhesive strip over its full surface area. At this point, it should be mentioned that, even with the stretched piece 76 of the adhesive strip running askew in an undefined manner, the lacquer film blank taken up in the application tool in any case assumes the same defined relative position in relation to the application tool. At the same time as the adhesive attachment of the film blank to the adhesive strip, the movable gripping tool 50 of the tool-integrated pulling-off device also grasps the tab 10 and securely holds it. After the film composite has been taken up in the application tool, the doctor knife returns again into the lifted-off starting position, represented in FIGS. 2 to 4 by solid lines.
During a working cycle, the doctor knife 39 comes into action twice and is moved lengthwise through the application tool 20, 20′ or 20″, that is to say a first time for taking up the film composite in the application tool and a second time for applying the exposed lacquer film blank to the intended bodywork part. In the case of the first doctor knife stroke (taking up), the movable winding device is functionless, whereas it comes into action in the second doctor knife stroke (application) and, during a stroke performed together with the doctor knife, pulls off the adhesive-side protective strip from the lacquer film blank application-simultaneously and winds it up. In the case of all the exemplary embodiments of the application tools that are represented in the figures, two separate carriages are provided, for the doctor knife on the one hand (carriage 42) and the winding device on the other hand (carriage 59), as well as separate actuating cylinders, so that the doctor knives and the winding device can be displaced independently of one another. Accordingly, the suction box shown in FIGS. 2 to 4 stands directly on the table 18.
By contrast, however, the suction box 19′ represented in
For exposing the adhesive side of the lacquer film blank 6, the film composite taken up in the application tool is lifted off from the base 27 up to the height of the counterstay tongue 46. Subsequently, the beginning of the adhesive-side protective strip 8 is detached from the adhesive side of the lacquer film blank initially in a stationary manner by the auxiliary device described above, the adhesive side of the lacquer film blank initially being only partially exposed by winding up. In this partially exposed state of the taken-up lacquer film blank, the counterstay tongue is pivoted back into its rest position, exposing the suction box, and the application tool with the film composite taken up in it is moved to the vehicle body. After the positionally exact alignment of the lacquer film blank over the frame member 3 or 4, the lacquer film blank 6 is doctor-bladed onto the bodywork part to which it is to be adhesively attached, which is securely held in a positionally defined and unyielding manner, from the stretched-out position at a distance by the doctor blade 38, 39 that is longitudinally movable within the application tool. In this case, the further pulling-off of the adhesive-side protective strip or exposing of the adhesive side of the lacquer film blank takes place simultaneously with the doctor-blading in a way corresponding to the progressive advancement of the doctor-blading of the lacquer film blank 6 onto the bodywork part.
For the sake of completeness, it should be mentioned that it would also be conceivable to pull off the adhesive-side protective strip 8 completely from the film composite before the application operation and only then begin to apply the lacquer film. However, with regard to the risk of the pulling-off of the adhesive-side protective strip releasing in the remaining film composite an electrostatic potential which may attract particles from the surroundings onto the exposed, adhesively effective side of the lacquer film 6 and keep them there, it is advisable to keep the time period between pulling-off the effective strip 9 and adhesively attaching the lacquer film 6 onto the bodywork part 1 as short as possible and to carry out only the least possible locational change of the remaining film composite during this time. This aim is best achieved if the adhesive-side protective strip is only pulled off during the application operation, i.e. application-simultaneously.
In order for the applied lacquer film to adhere well and permanently on the vehicle body, the lacquer film blank 6 must be doctor-bladed with a very high linear pressure during the application operation. To be precise, this pressure should be at least 6 N/cm and preferably lie in the range from 7 to 17 N/cm. With such a high linear pressure under the doctor-knife edge, the smallest gas inclusions are progressively pressed out from the adhesive join. Air that is initially adhesively bonded to the exposed layer of adhesive is squeezed out on account of the high linear pressure of the doctor knife. It is also not possible for microfine gas inclusions to join together subsequently to form visible gas bubbles, because—as stated—no gas inclusions remain behind any longer in the adhesive join. When the presented film composite is taken up in the application tool, however, a lower doctor knife pressure than for the application of the lacquer film itself is sufficient.
An important requirement for the application-simultaneous pulling-off of the adhesive-side protective strip 9 is that the lacquer film blank 6 is doctor-bladed onto the bodywork part 1 only in a single direction and with only one doctor knife 38, 39. In this case, an approximately constant distance A—see
To prevent unacceptably great elongations in the film composite 5, and in particular in the lacquer film blank 6, in particular toward the end of the doctor-blading operation, the deflection roller 37b on the end side is brought up close to the bodywork surface 3, 4 that is to be covered (see
Finally, on account of a pulling-off movement of the application tool 20, in particular the deflection roller 37a on the start side, the upper-side adhesive strip 31 is pulled off from the outside of the completely applied lacquer film blank 6. For this purpose, the application tool 20 is pivoted away from the bodywork surface 3, 4 about a virtual pivoting axis lying in the vicinity of the deflection roller 37b on the end side, as indicated in
One special feature of the lacquer film application to vertical frame members of passenger car side doors is that, once the lacquer film blank has been correctly adhesively bonded onto the flat side of the frame member, its laterally overhanging edges must be folded around and pressed onto the rear side. As long as no robot tool has been provided for this, this can be performed manually in a conventional way, under some circumstances with the assistance of special hand tools for pressing it onto the rear side. Moreover, this activity is less problematical with respect to possible defects, even if carried out manually, since the the main part of the lacquer film is applied in a positionally correct manner and free from bubbles and folds.
An important feature of the present invention is the reuse of the part 76 of the adhesive strip that is stretched in the take-up plane 21, which is only renewed after being used a number of times. Various variants are suitable for this in the case of the exemplary embodiment represented in FIGS. 2 to 5. For example, the piece 76 of the tool-side adhesive strip 31 that is stretched in the take-up plane may be completely renewed at intervals, i.e. after being used a number of times, for example 4 to 6 times. Instead of this, the renewal of said piece of adhesive strip may take place incrementally after each application operation, but only partially each time, in that the piece of adhesive strip 76 that is located in the take-up plane is respectively advanced only by a corresponding fraction of the stretched-out length. For example, the piece of adhesive strip may be incrementally advanced after each application operation by 20% of the stretched-out length, so that after five application operations the piece of adhesive strip located in the take-up plane would be completely renewed.
In this connection, the exemplary embodiment of the application tool 20′ that is represented in
At this point, we should also discuss the simple version of the application tool 20″ as shown in
The sequence for applying the film composite taken up in the robot tool is to be discussed in more detail below with reference to FIGS. 7 to 9, a slightly earlier state, as represented in
Further preparatory pulling-off of the protective strip from the adhesive side of the lacquer film may take place preferably on the path of the application tool to the vehicle body. The winding speed is in this phase made to match the displacing speed of the gripping tool 50 in such a way that the part of the adhesive-side protective strip 8 pulled off from the film composite on the one hand is wound up with a certain density onto the gripping tool and on the other hand a certain initial length of the adhesive side of the lacquer film blank is exposed. During the transfer of the application tool from the table 18, 18′ to the frame member 3, 4 of the side doors, the application tool is pivoted in such a way that the deflection roller 37a on the start side comes to lie on top and the lacquer film can be doctor-bladed from top to bottom, i.e. in a descending manner. This has proved to be advantageous in comparison with an ascending doctor-blading with regard to the concave shape of the bodywork surface in the region of the transition from the frame member to the door side panel.
At the beginning of the actual application phase, the doctor knife 38/39 is lowered in the direction of the arrow from the waiting position, represented in
During the doctor-blading of the lacquer film onto the bodywork surface, the gripping tool 50 driven in winding mode is advanced in a translatory manner, running ahead at the same speed as the doctor knife and with a constant distance A from the doctor knife. At the same time, the gripping tool is driven at such a winding speed that the adhesive-side protective strip 8 detached from the lacquer film at the progressively advancing detachment point 69 is continuously wound up to form a roll 68. As this happens, the circumferential speed of the roll is approximately, i.e. on average, equal to the translating speed of the doctor knife. In the region of the progressively advancing detachment point 69, the film composite 5 is supported by the roll 68, which is becoming larger.
The end of the doctor-blading operation is represented in
At the stage of the application operation that is shown in
After the pulling-off of the adhesive strip, it is moved further by a certain fraction of the stretched-out length, whereas the wound-up adhesive-side protective strip 8 is discarded by means of a waste container. For discarding the adhesive-side protective strip wound-up on the gripping tool, the application tool must be brought into such a position that the gripping tool 50 is aligned approximately parallel to the direction of gravitational force and points downward with its free end, so that, after opening the gripping tool, the loosened roll 68 can fall axially off the winding core as a result of gravitational force.
Because of its practical significance for the application technique, the already repeatedly mentioned gripping tool is shown in an exemplary embodiment in
In the ready-to-receive starting position, the long-nose pliers 51/52 must be in such an embracing position, and the rotary drive must be equipped with a correspondingly suitable control for automatically bringing about this embracing position, in which the upper nose part 51 is arranged above the take-up plane 21, whereas the lower nose part 52 is located in the ready-to-receive starting position beneath the take-up plane 21.
In the case of the exemplary embodiment of the gripping tool that is represented in
The advantage of the gripping tool 50 as shown in
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP04/00286 | 1/16/2004 | WO | 9/13/2005 |
