A DRAWING OR CUTTING MACHINE OF THE PLOTTER TYPE AND WITH MEANS FOR ADVANCING A WORKING WEB FROM A SUPPLY REEL

Abstract: In machines for cutting a sign text or sign symbols in a working web of plastics it is usual that a coordinate controlled working head (10) works on a web length (18), which is laid out on a table (2) and is unreeled from a supply reel (16) such that new web lengths can be laid out on the table when the need arises. The web is pulled forward by means of a transverse, short driving roller (24) located at one side of the front end of the table, whereby the roller can advance both broad and narrow webs, which should always have a side edge located along a specific reference line of the table top. The web, during the pulling forward thereof, may easily leave that line, outwardly or inwardly, and it is important to adjust the new web length into a correct location both longitudinally and transversely. The invention provides for an automatic lateral guidance of the web (18) by a simple detection of the location of the reference edge thereof and an associated control or changing of the transverse direction of the driving roller (24, 26) for imparting a compensating cross movement of the web length being advanced. Also the lengthwise movement is controllable in an accurate automatic manner.

Description: A drawing or cutting machine of the plotter type and with means for advancing a working web from a supply reel. The present invention relates to a drawing or cut¬ ting machine of the type having a table plate having at one end a reel holder for a supply reel of paper or another web that is to be treated on the table plate when laid out thereover, and at the opposite end a driv¬ ing mechanism for advancing the web over the table plate, while a coordinate-controlled drawing or cutting head is mounted on a transverse, which is movable along the table plate. Machines of this type are usable for automatized cutting of sign texts and symbols in a self adhering plastic web, which, carried on a backing sheet, can be unreeled as a continuous web from a supply reel; after the cutting of the relevant cutting lines the desired letters or symbol details may be left on the backing sheet while the remainder of the plastic web is drawn off therefrom. It is important that for different orders webs of different widths may be used, viz. such that the waste of plastic web material may be kept at a required minimum, and for this reason the web driving mechanism should be able to advance both wide and narrow webs. For several reasons it is also important to make use of a steady reference location of one edge of the various webs, no matter their respective widths, i.e. the webs should always be laid out and advanced with one edge located in a well defined manner closely adjacent one side of the table plate. This implies that the driving mechanism, which may be a driving roller, should be located at the table end close to the selected side edge of the table, such that also quite narrow webs can be advanced, when a new web is desired. In fact it has been found that such a driv¬ ing mechanism having a relatively small width is suffi¬ cient to advance even much wider webs, i.e. these can be advanced solely by a driving engagement at a narrow edge area thereof. It has been found, however, that there are certain problems with respect to an accurate control of the location of the reference edge of the web in connection with the advancing of the web, and it is the primary purpose of the invention to provide a system by which this control can be effected accurately and in a simple manner. According to the invention advantage is taken of just the circumstance that the driving mechanism can cooperate with but a quite narrow width or partial width of the webs, inasfar as this makes it possible, without associated disadvantages, to effect variations of the direction of the driving roller or preferably a pair of cooperating driving rollers in response to an automatic detection of the location of the web edge, in order to achieve that the web edge is guided into a correct loca¬ tion whenever a deviation therefrom is detected. The detection, as well known per se, can easily be effected by sensors such as photo cells reacting to web edge locations respectively inside and outside the correct position, and the short driving rollers may then be angularly adjusted for producing an advancing which will immediately result in a lateral displacement of the web length into the correct position of the reference edge. It is well known to effect such corrections in response to a detection of an incorrect location of a web edge, but with the use of broad or rather long driv¬ ing rollers the corrections cannot be made just by a simple, corresponding turning of a driving pair of rol¬ lers, as these are in steady clamp connection with the web and therefore, when turned, would produce a surface deformation of the web; the web would be pushed forward- ly or rearwardly at the roller portions moved the larger distance in the general advancing direction by the turn¬ ing of the roller pair, and this would very easily re¬ sult in highly undesired bulgings of the web. On the other hand, when the driving rollers are short and co¬ operate with a narrow web width or partial width the resulting deformation of the web will be insignificant, and the desired directional changes of the web movement will be effected immediately by the adjustment of the angular position of the driving roller pair, such that the web, when deviating from a correct positioning, will be guided back to the correct position very quickly and easily. In the following the invention is described in more detail with reference to the drawing, in which:- Fig. 1 is a perspective view of a drawing or cut¬ ting machine according to the invention, while Fig. 2 is a corresponding partial view thereof. The drawing or cutting machine shown in Fig. 1 is built as a table with an elongate table plate 2, the opposed side edges of which have guiding tracks 4 for block heads 6 carrying between them a traverse 8, which carries a longitudinally movable holding head 10 for a drawing or cutting implement 12. At a rear end of the table 2 is mounted a horizontal supply reel 16 of a paper or plastic web 18, which can be drawn from the reel and laid out on the table 2 underneath the traverse 8 and the drawing or cutting head 12. The web is drawn to the opposite end of the table 2, where there is mounted a cross cutting device 20 and a driving system 22, which, through a built-in pair of driving rollers, cooperates with a reference edge area of the web 18 adjacent one side of the table. In Fig. 2 is shown that the driving system 22 com¬ prises a pair of cooperating driving rollers 24, 26, which are mounted on a common carrier post 28 also car¬ rying a driving motor 30, which, internally in the post 28, is in driving connection with at least one of the rollers 24, 26. The post itself is mounted rotatably about a vertical axis by means of a shaft pin 32 in a fixed socket portion 34. On a radial arm, which is here constituted by the motor 30, is mounted a nut 36 coope¬ rating with a screw spindle 38 as driven by a gear motor 40, which will thus be, able to rotate or turn the post 28 a certain angle in both directions about the pin 32, whereby the pair of rollers 24, 26 projecting from the post can be pivoted horizontally as indicated by an arrow a . In the table plate 2 there is mounted, in front of the roller pair 24, 26, a pair of sensors 42 and 44, which are located just outside and just inside, respec¬ tively, of the desired location of the relevant refe¬ rence edge of the web 18. These sensors are connected with the motor 30 through a non-illustrated control unit in such a manner that the gear motor 40 will pivot the roller pair 24, 26 in the direction designated £, if the web edge is misplaced outwardly to cover the sensor 42, whereby the pair of rollers during the advancing of the web will impart to the web a lateral movement component so as to cause the web edge to be pulled inwardly until the sensor 42 is again uncovered, whereby the roller pair is triggered to pivot back to normal position. Inversely the roller pair is pivoted in the direction II if the inner sensor 44 is uncovered, until it becomes covered again. Consequently the web edge can be guided with a high accuracy so as to assume its desired situa¬ tion at the end of each advancing operation. Normally quite small corrections will suffice, i.e. the pivotal movements of the pair of rollers 24, 26 can be quite small, in fact so small that no problems are encountered by the pivoting taking place while the web material is clamped between the rollers 24 and 26, this of course being conditioned by the rollers having a relatively short axial dimension. Just because the adjustment movements can be quite small the gear motor 40 may be replaced by a mechanism, e.g. simple solenoids, that can effect a pivoting of the roller pair 24, 26 between only three positions, viz. an accurately transverse position and slightly angularly offset positions at respective opposite sides of that transverse position. For reasons specified below it may be important that the web be advanced exclusively by a controlled rotation of the rollers 24, 26 and not additionally by a resulting longitudinal movement of the roller pair, as the case may be when the roller pair is pivoted about the post pin 32. For enabling the pair of rollers to be pivoted without any resulting longitudinal influence on the web it is possible to arrange for the pivoting to take place about a vertical axis through the middle area of the roller pair, e.g. by means of a cranked pivot shaft. In a plotting apparatus of the considered type it may happen that a sign cannot be made or ready-made on a single laid-out web length 18 on the table 2, either because the sign is longer than the table or because an available rest length of the web is not sufficient for the subsequent task. It is well known that in such cases care should be taken to advance the web only partially, viz. just sufficiently for the delivery of a ready-made product, even though the associated web length takes up only a foremost partial length of the table plate, such that the subsequent sign member may be produced with the entire table length at disposal, or to interrupt the sign making at the rear end of the non-completed sign located exactly in register with a marking on the table adjacent the front end thereof, whereafter the associ- ated control equipment takes care to continue the carry¬ ing out of the already initiated sign making, now start¬ ing from the front end of the table. It requires a qualified manual effort to carry out such a precise advancing of the web into its new posi¬ tion in order to obtain a quite unnoticeable transition between the initiated and the continued sign making, and it is an additional purpose of the invention to provide a technique which will make this manual effort or atten¬ dance superfluous. This purpose is achievable in that based on the data read into the control unit it is possible to effect or control the advancing of the web with such a high accuracy that the web is already hereby positioned cor¬ rectly for a direct continuation of a specific working initiated on the previously laid-out web portion. It is of course a first condition that the newly advanced web length is laid out with exactly the same positioning of the reference edge of the web as by the previous laying out, and it has already been explained how this is pos¬ sible. Another condition is that the driving roller pair 24, 26 is actuated for the attainment of a very accu¬ rately controlled advancing of the web, this being a question not only of a well controlled actuation of the driving motor 30, but also of the web 18 actually being advanced in close accordance with the control signals supplied to this motor. Particularly for this reason it is important, as already mentioned, to make sure that there will be no undue sliding between the driving rol¬ lers and the web 18, e.g. by a resulting substantial pivoting of the roller pair 24, 26 about an axis sub¬ stantially outside these rollers. It is hereby a further and important circumstance that the pair of driving rollers 24, 26 should be able to advance the web 18 in an accurate manner into a "con¬ tinuation position" on the table 2 irrespectively of the resistance of the supply reel 16 being more or less pronounced. For this reason it has been found important that the unreeling resistance be reduced to a minimum by arranging for the reel shaft 14 to be connected with sensing and driving means which, responsive to an occur¬ ring pull in the web 18, will give rise to a motor driven rotation of the shaft 14 for a practically fric- tionless unrolling of a new web length to the table 2. Hereby the new laid-out web length, by the computer controlled operation of the driving rollers 24, 26, may be delivered just in such a position, in which the draw¬ ing or cutting head 12 may resume its operation at the front edge area of the table for completing a previously initiated working, without giving rise to visible dis¬ placements between the respective sections of the draw¬ ing or the cutting lines and without the advancing of the web having to be watched or manually finely cor¬ rected. When the advancing of the web can be effected with high accuracy in a fully automatic manner it will be rather unimportant after which criteria the advancing of the web and a possible associated move of the working head are effected; thus, it is perfectly possible to make use of but a partial advancement, e.g. just suffi¬ ciently for the termination of an already initiated working.

Claims: C A I M S : 1. A drawing or cutting machine of the plotter type and of the kind having a table plate having at one end a reel holder for a supply reel holding a web material that is to be worked on the table plate when laid out thereover, and at the opposite end having a driving mechanism for advancing new lengths of the web over the table, and further having a coordinate-controlled draw¬ ing or cutting head, which is displaceably mounted on a displaceable traverse mounted crosswise over the table, said driving mechanism comprising a short driving roller cooperating with a reference edge area of the web mate¬ rial or with a narrow web material extending along such an area, characterized in that the driving roller or preferably a pair of cooperating driving rollers is mounted pivotably about an axis perpendicular to the table plate and that in connection with the latter there is arranged sensor means for sensing a location of the web edge respectively inside and outside a predetermined reference line, said sensing means being operatively connected with control means for pivoting the driving roller into a temporarily swung out position for guiding the web edge into coincidence with the reference line in case of the web edge during the advancing of the web being moved away therefrom. 2. A machine according to claim 1, characterized in that the pivot axis of the driving roller is located immediately adjacent one end of the roller or at the middle thereof. 3. A machine according to claim 1 or particularly claim 2, in which a control unit for the movement of the drawing or cutting head is adapted to actuate this head to proceed with its working on a web portion extending beyond the rear edge of the table, characterized in that the driving roller is controlled so as to automatically effect just such an advancement of the web which corre¬ sponds to the preprogrammed jump of the working area of the drawing or cutting head. 4. A machine according to claim 3, characterized in that the means for holding the supply reel are arranged so as to effect an active unreeling of the web during the advancing thereof.

Inventors: NONBYE OLE, NONBYE, OLE
Applicants: SIGN TRONIC AS, SIGN-TRONIC A/S
Application year: 1989
Main classification: B65H23
IPC codes: B26F1, B65H23, G01D15