WO1998058753A1

WO1998058753A1 - A metal sheet press-bending machine

Info

Publication number: WO1998058753A1
Application number: PCT/IT1997/000250
Authority: WO
Inventors: Luciano Gasparini
Original assignee: Luciano Gasparini
Priority date: 1997-06-20
Filing date: 1997-10-16
Publication date: 1998-12-30
Also published as: EP1011886B1; CN1259889A; BR9714752A; PT1011886E; AR013102A1; CZ9904634A3; ES2172009T3; DE69710101D1; CN1102871C; US6266984B1; EP1011886A1; CZ294461B6; JP2002504862A; ATE212259T1; DE69710101T2

Abstract

A press-bending machine to bend metal sheets, having improved features in the respective press-bending with measuring and control system operating on at least four points of the bending angle, of the type in which the press-bending machine has: an upper vertically reciprocal elongated bending punch (2, 101); a lower static elongated bending matrix (5-102) with at least a longitudinal bending groove (5'-102'); feeler means to measure the respective bending movement of the metal sheet in bending inside said bending groove, to control by data process logic unit the bending parameters of bending process in said bending machine, said feeler means operating with at least four bending detection points, characterized in that all said detecting points are conceived in such a way to be divided in two sets of bend detecting points, one to one side (6-9''; Rc-Rtleft; 18'; 108'-107'; 109'-1010') and one to the other side (7-9'''; Rc-Rtright; 18''; 108-107; 109''-1010'') and in symmetrical way divided in number and position respective to the vertical plane passing along the respective sheet bending line corresponding with the bending corner of the resulting bent sheet.

Description

DESCRIPTION A METAL SHEET PRESS-BENDTNG MACHINE Technical Field This invention has for object a press-bending machine having improved features in the respetive press-bending with measuring and control system operating on at least four points of the bending angle. The innovation finds particular even if not exclusive application in the controlled sheet deformation on press-bend working. Background Art. Bending presses are known. They find wide use in the metal and mechanical industry, and in particular in the bending of metal sheets, for example for obtaining some differently shaped longitudinal sections, sometimes with the possibility of being taken up and, each of them, subjected again to a bending-pressing cycle. As a rule, it is possible to notice that a bending cycle consists essentially of the vertical descent of a tool up to touching the underlying metal sheet resting on the bench, in the carrying out of the bend, and then, at the end, in going back (lifting) up to reaching a starting position. For carrying out the previous phases, the machine is made up of two parts, respectively a dynamic upper one (movable upper part), and a static lower one, making up the underside of the machine placed on the perpendicular of the dynamic part. Regarding the dynamic part, in the execution of a bending cycle, the movable bending tool (elongated punch), made up of a blade differently shaped, also of the interchangeable type, effects exclusively a vertical to and fro movement, ensured by at least one oleodynamic cylinder, which determines the descent of an upper cross-piece which supports longitudinally said elongated punch, said punch operating towards a lower cross-piece that supports an interchangeable elongated matrix, followed by the eventual stop and lifting in the starting position. In existing solutions, some drawbacks are noticeable. These, in general, concern the inaccuracy of the bending angle and in any way relate to an objective difficulty of predetermination and measuring of the bending angle. The traditional system provides that, giving a known total height of the matrix and depth of the groove in the matrix bending area, and the thickness of the sheet, the punch lowers to touch the sheet, then to further lower of a prestablished height to reach the required bending angle. In the machines with numerical control, the punch descent is calculated mathematically on the base of some parameters set by the operator, and consequently, the machine is prearranged for executing the programmed angle. However the result is not always optimal, as such technique, many times leads to obtaining angles with some errors even if limited ones. This happens because of the presence of different factors, for example, the thickness of the sheets which is not constant, where even the incidence of few hundredths of a millimetre negatively influences the working. For other reasons, because said predetermined theoretic calculation, such system does not offer the possibility of really checking the result, at the moment of bending, with the risk of endangering the productive process. An additional factor having considerable character, relates to the natural elastic return of the material, which is calculated hypothetically and therefore in so far as it can be reliable, it may get close to the desired result, but it will never be considered as a real data. Finally, besides the faultiness of the product, it is necessary to consider that the desired result is never attainable at the first bending cycle, that is at the first press- bending, but generally, a second press-bending phase is always necessary that intervenes to correct the first result. With the aim of solving the problems pointed out, some complex press machines were conceived, which use a bending matrix supplied with an adiustable bottom, allowing to obtain a bending angle more precise than that of the traditional systems. From a practical point of view, said matrix provides two surfaces coplanar and movable on horizontal plane defining in an intermediate position a longitudinal groove whose bottom may be eventually modified in height. Such groove determines the momentary bending angle by means of the relative position of both the support surfaces on the side of the groove, which delimit its opening, and the bottom of the same groove. Also in this hypothesis, however, persists a certain inaccuracy, one of whose causes is ascribable to the phenomenon of the elastic return of the sheet, a condition which occurs at the moment which follows the piece discharge, altering the bending angle originally determined and theoretically calculated. Consequently, is necessary to proceed at first with some working tests, and, before starting the definitive bending production cycle, to carry out the due corrections on the numerical control, intervening on the pushing action of the punch and eventually on the position of the matrix bottom. All this, besides requiring the intervention of specialised personnel, involves the machine stop and in conclusion, a considerable loss of useful time unavoidably influencing the relative production costs. European Patent 340 167 (Hammerle) document, proposes a bending process according to a given nominal angle with the aid of a bending equipment made up of a punch and of a matrix, which is supplied with an adjustable bottom according to the angle to be formed. The text points out that the process consists in that it provides: - in a first phase, the adjustment in height of the matrix bottom occurs on the basis of the first angle to be obtained, which is a little wider in respect to the given nominal angle, where the sheet is bent on the basis of this first angle by the lowering of the punch up to the matrix bottom; - in a second phase, the section is discharged, so that a return of the same in the stretched position occurs; - in a third phase the measured angle deriving from the returned and stretched section, is compared with the first angle and the position of the matrix bottom is adjusted with a value that corresponds to the nominal angle minus the difference between the angle measured on the released section and the first angle; - in a fourth phase the bent sheet is completely pressed by the punch again charged against the matrix bottom, which will take a correct position in height. However even this solution is not free from drawbacks. First of all, it appears as an extremely complex machine, not flexible and somewhat oversized, which needs a constant and accurate maintenance and setting-up, predominantly feasible by highly specialised personnel. The consequence is, for the reference market, some high costs, above all related to the purchase and management of the machine itself. From a qualitative view-point, finally, said solution does not allow to obtain a sheet bending with the round corner on the extrados, therefore optimal for the next processing. And in fact, it can be noticed that in the bending phase, by using a third dynamic point as mechanical element provided on the matrix bottom, the sheet in logic correspondence tends to be deformed, getting flat, practically becoming squashed, even if slightly, mainly in correspondence of the extrados of the bending angle. A proposal, that can help to solve part of the problems previously pointed out, was put on the market by the Belgian Company LVD with the system named Easy- Form®. Said system, consists in providing a movable arm, placed on the matrix side, which, supported by two articulations, and in bending phase, places a sensor means in contact with one of two wings of the diverging sheet. Said sensor means, is coaxially movable in respect to said arm, and provides a measured data to the control logical unit of the machine. In this hypothesis, there are therefore three measuring points for giving parameters to the machine, two of which known, made up by the intersection corners of the plane with the matrix bending groove, and one variable and detectable by the oscillation with following positioning of said movable arm. However, this is just because of the improper side position of the third point, dynamic, in respect to the matrix for the measuring of the bending angle, that a satisfactory precision is not allowed as, because of the natural characteristics of the material, a data unlike and different from the real data objectively concerning the bending angle would result. Finalised to radically solving the problems of the solutions previously described, the applicant with the Italian Patent Application TV97A000039 (Gasparini), proposes a press-bending process of the metal sheet by a direct measuring system, in which the following is provided: - the advancement of the metal sheet on the working bench, up to intersecting the vertical axis plane of the upper punch supported by an upper cross-piece, towards the underlying matrix supported by a lower cross-piece; and in which on the back of the sheet foil feel a feeler means, passing into the matrix and connecting each with a respective measuring group, each of which communicates with a data processing logical unit that controls said press-bending machine ; - therefore, after carrying out the descent phase of the punch, towards the underlying matrix, and then press-bending the sheet and determines a corresponding displacement along the vertical axis of said feeler means, which, being in co-operation with reading means of a corresponding measuring group, communicate to the data process unit the data relative to the bending stroke; - at the end, in proceeding with the reascent of the punch, by carrying out at the same time the reset of said feeler means to their original condition; - and again in which, detecting in the first phase through said feeler means, permanently in contact with the sheet foil, a bending angle different in respect to the preset nominal one, said data process unit ensures the consent to the press-bending machine, not discharging the product so obtained, to carry out at least a second descent phase of the punch, towards the underlying matrix up to passing again on the same bending angle, to then proceed with the discharging of the product. In relation to said process, it is finally an opinion of the applicant, that the working and above all the measuring phase of the bending angle may be further optimized, above all with regard to the precision and the reading times of the bending angle obtained, not excluding the possibility of intervening for the correction of the elastic return of an already pressed-bent sheet. A recent system for the measuring of the bending angle characterised by the trade-mark ACB®, was proposed by the Firm TRUMPF and concerned a product named TrumaBend series V. It, in practice, consists in providing on the inside of the upper bending tool (punch), two feeler discs, with different diameters. During the bending process the discs are self-centred measuring four contact points on the internal side of the bend, and consequently, on the basis of the distance of the centres of the discs, the system allows to calculate the effective angle. The main drawback, which can be ascribed to the above mentioned solution, consists essentially of the fact that it is not possible to intervene on the bendings with such measuring system, in which the sheet, relatively to the angle obtainable on the internal side of the bending, is wider than 90 ° to 10°. Said system, additionally, obliges to maintain the sheet edges somewhat wide, reducing the use possibilities of the different matrixes, with a consequent lower flexibility of the press-bending machine. Finally, said system predetermines the bending angle by means of some calibration matrixes, and consequently, on one side involves a limitation of the bending measuring and on the other does not allow a rapid obtainment of the bending desired, above all in consideration of the fact that it needs a complex setting. In relation to the two latter techniques for the measuring of the bending angle, it is the opinion of the applicant, that the working and above all the measuring phase of the bending angle may be further optimised, above all with regard to the precision and the reading times of the bending angle obtained, not excluding the possibility of intervening for the correction of the elastic return of an already pressed-bent sheet. These and other problems are solved with this innovation according to the characteristics as in the included claims, by a press-bending machine to bend metal sheets, with measuring and control system of the bending angle, of the type in which the press-bending machine has: • an upper vertically reciprocable elongated bending punch (2,101); • a lower static elongated bending matrix (5-102) with al least a longitudinbal bending groove (5'- 102'); • feeler means, having bending detecting points, to measure the respective bending movement of the metal sheet in bending, on said bending groove, to control and command by data process logic unit the bending parameters of bending process in said bending machine, characterized in that all said bending detectmg points are conceived in such a way to be divided by an immaginary vertical plane passing on the bending corner line of the bending metal sheet (yl), in two sets of bending detecting points, one set of detecting points to one side and one set of detecting points to the other side. In this way it is possible to have a more precise measurement of the evolution of the bending end and it is possible to measure in a more precise way even the bendings with a minimum angle of bend, allowing best performance of the operation of the entire press-bending machine. In the preferred solution the bend detecting points are angled and the angle of each of said feeler bending detection points has an angle equal of more than 90°. In an alternative solution the feeler means have two movable wings like a butterfly feeler where the respective wings follow the respective movement of the opposed bending surfaces divided by the bending line corner. Advantageouslv the feeler is substantiallv a fork and a bending operation is as follows: - the advancement on the working bench of at least one metal sheet, up to intersecting the descent vertical axial plane of a punch supported by a reciprocally movable upper cross-piece, toward the underlying matrix supported by a lower cross-piece; and in which on the sheet rested on the matrix, feel at least one feeler means made up of a feeler measuring fork interacting with a position transducer, communicating with a data processing logical unit that controls said press-bending machine; - therefore, in carrying out a first descent phase of the measuring punch supporting upper cross-piece, towards the underlying matrix supported by a lower cross-piece, pressing-bending the sheet foil and determining a corresponding displacement along the vertical axis of said feeler means, which, interacting with a position transducer, communicates to said data process unit the data relative to the bending stroke; - at the end, in the carrying out of at least one partial re-ascent of the punch, carrying out at the same time the reset of the feeler means in an original starting condition; - and again in which, detecting in the first phase through said feeler means, a bending angle different in respect to the preset nominal one, said processing unit ensures the consent to the press-bending machine, not discharging the product so obtained, for carrying out at least one second descent phase of the punch, towards the underlying matrix up to resting again on the same bending angle, for then proceeding with the product discharging. In one solution the use of a feeler measuring fork realizes substantially two feeling angled points wherein the other two angle points is realized in the borders (corners) of the elongated groove of the matrix. Better performance is mainly due to the improved measuring system of the bending angle, which besides being extremely precise, is always supplied in real time, allowing to intervene in a determinant way for the error correction, up to obtaining the nominal bending angle with the due precision. In this wav, the reading during the bending is more precise, thus avoiding bending errors. Using the fork-like shaped feeler means, the bending angle is measured, not as if this were an ideal geometric figure defined by three points, but viceversa considering the real inclination of the two specular planes each interested by two measuring points one of which is known and the other is variable, definitely overcoming the errors caused by the thickness of the sheet, by the material composition, and of the thinning caused by the sheet stretching in correspondence of the edge. The consequence is that, once the machine is set for the obtainment of a certain bending angle, it is possible to bend another sheet of any material and thickness, provided that it is compatible with the width of the bending groove, without modifying the set programming and without carrying out tests. It must be additionally considered that the use of such feeler means allows a radical simplification of the press-bending machine, with, on one side an important reduction of the manufacturing costs and on the other a fair containing of the encumbrances of the respective devices. As a consequence thereof, it requires a minimum maintenance, easily possible by suitable personnel and with short stops of the productive cycle. This system has the further advantage of simplifying the execution of the control software as this means a measuring of only a linear displacement of the feeler fork. Finally, the system for maintaining the pressed-bent sheet in place is particularly interesting and innovative, for allowing the execution of a second bending phase, suitable to correct the elastic return of the sheet measured after a first bending phase. Said system, substantially, avoids the pressed-bent sheet, from being subjected to displacements, also accidental, in respect to the matrix and this until the punch has not again touched the bending groove for the correction of the error detected in respect to the nominal data of the preset angle. In a further solution a measuring device on four points of the bending angle, in a press- bending machine is provided, in which the following bending svstem is provided : - on the back of the metal sheet rested on the matrix, permanently feel at least one feeler means, provided along the corner axis of the bending groove of said matrix, said feeler means being made up of a couple of forks mutually interacting, the one inside or adjacent in respect to the other, in such a way that the median axis of both the forks coincides with the axis of the punch, and in which said elastically yielding forks are connected with a relative position transducer communicating with a data process logical unit that manages said press-bending machine ; - alternatively, providing along the punch suitable to pass on an underlying matrix, at least one feeler means made up of two interacting slides, elastically yielding, connected with a relative position transducer communicating with a data processing logical unit that manages said press-bending machine, the one inside or adjacent in respect to the other, whose lower ends of different width, are perfectly flat and whose end corners have a ray-like disposition, and, in a rest condition, eventually parallel in respect to the underlying sheet foil to be bent as well as coplanar and coinciding with the end of the punch tool, all having the median axis in common. With this solution the measuring of the bending angle is made possible, on four dynamic measuring points or bending detecting points, with the maximum precision possible without any limitation relative to the angle to be obtained. This solution does not need the execution of a perfect groove in the matrix, as the aforesaid measuring system is independent of any reference on the same. The measuring system is independent from the eventual elastic deformation of the matrix, in the bending execution phase. The bending time can be reduced, accelerating the whole productive process. Such result is more evidently considered the most effective measuring system of the bending angle, which other than being extremely precise, always provides the data in real time, allowing to intervene in a resolutory way for the error correction, up to obtaining, with due precision, the nominal bending angle. As the reading of the angle during the bending occurs on the same side of the sheet, in the first case on the lower surface and in the second case in the upper surface of the sheet, errors due to the change of thickness of the sheet are avoided. Additionally, it is found that by using one of the above mentioned feeler means, the bending angle is measured considering the real inclination of the two specular planes of the sheet, each concerned, on the intrados or on the extrados by the couples of measuring points, overcoming in a definitive way the errors caused by other factors eg yielding (kind of the material), and by the thinning caused by the stretching in correspondence of the edge. The result is that, once set the machine for the obtainment of a certain bending angle, it is possible to bend another sheet of any material and thickness, provided that it is compatible with the width of the bending matrix groove and respective punch, without modifying the programming set and without carrying out tests and this also with small bendings. These, and other advantages will appear from the following description of same solutions with the aid of schematic drawings, whose details are not to be considered as limitative but only illustrative. Figure 1., shows a view in detail of one of the phases of the sheet foil bending process, seen in correspondence of the punch which rests on the matrix, determining the displacement, along the vertical axis, of a measuring device including a lower fork- shaped feeler means. Figure 2., shows a view, in detail and with reference to the previous Figure, of the four bend detecting points detected by the measuring device, from which are obtained respective data necessary in the determining of the actual bending angle. Figure 3., shows a front view of a press-bending machine, in which, relative to the lower cross-piece, some devices for the bending angle measuring are pointed out. Figure 4., shows a cross sectional view, of a variation to the measuring device and in particular to the structure of the fork-shaped feeler means, represented by an axially guided slide , with the end coplanar with the matrix plane. Figure 5., shows, always a cross sectional view, of the fork-shaped feeler means, with the end pushed downwards respect to the matrix plane, and therefore in a sheet bending dynamic condition. Figures 6. and 7., represent respectively, a sectional vertical view of a fork-shaped feeler means, active along a matrix and a plan-view of the same one. Figure 8., illustrates a possible variation to the fork-shaped feeler means, consisting of a measuring device of the bending angle with vertically movable axis in respect to the matrix bottom, and in which on the end of said axis is hinged an elastically yielding book-like plane. Figure 9., shows a dynamic condition of the hinge feeler means of Figure 8., and in particular consequent to the execution of a bending. Figures 10. and 10a., represent a sectional view, and in two operative conditions, of a part of the punch aiming at passing on the sheet as a presser for maintaining it in position, allowing the repetition of a bending phase for correcting a value altered because of the elastic return. Figures 11. and 12 show an alternative solution of the fork feeler means using a double fork. Figure 11., shows a view in detail of one of the phases of the sheet bending process, seen in correspondence of the punch which rests on the matrix, determining the displacement, along the vertical axis, of a measuring device including a feeler means consisting of a double fork. Figure 12., shows a view of a subsequent phase of the process for the working of the sheet foil found in Figure 11., seen in correspondence to the punch that passes on the matrix, determining the displacement, along the vertical axis, of a measuring device including feeler means made up of a double fork. Figures 13 to 16 shows alternate solutions in which the feeler means are provided upwards of the respetive punch. Figure 13., shows a view in detail of one of the phases of the working process of the metal sheet, seen in correspondence of the punch going to pass on the matrix, determining the displacement, along the vertical axis, of a device, alternative to the previous one for the measuring of the bending angle including associated feeler means along the punch. Figure 14. shows a view of a subsequent phase of the working process of the sheet foil as in Figure 13., seen in correspondence of the punch that passes on the matrix, determining the displacement, along the vertical axis, of the relative measuring device of the bending angle. Figures 15. and 16., show a variation to the design of interaction with the relative position transducer group, of the alternative device of Figs. 13. and 14. for the measuring of the bending angle, including the associated feeler means along the punch. Considering the figures 1 to 10-10', it can be seen that a press-bending machine (A), is made up of an upper and lower part, the first essentially dynamic in respect to the second one, static. Of the first one, is part an upper cross-piece (1), vertically movable along the vertical axis (Y'-Y") in respect to the frame of the pressing-bending machine, on whose lower end is provided associated, longitudinally, a tool of the interchangeable type, making up the punch (2). The press-bending machine (A), provides at the ends, a cylinder means (3, 3') for each side, which determines the descent and lifting movement along the axis (Y'-Y"), of the upper cross-piece (1) towards the underlying lower cross-piece (4), which supports a matrix (5) also of the interchangeable type. Said matrix (5) has longitudinally, at least one bending groove (5') that determines the bending angle "α" of a sheet foil (B) subjected to a working cycle. In this case, along the longitudinal groove (5') of a matrix (5), is provided at least one measuring area, in this case two of them (r'-r"), placed at the ends of the same one, or near to the sheet ends (B), and more in detail a right one and a left one (r'-r"). On the top of said groove (5'), the walls, obtained bv the intersection of the tilted planes with the horizontal plane of the matrix (5), two opposite corners, realizing a first couple of said angled bend-detecting points (6, 7) are obtained, on which corners the sheet (B) in bending phase works. The groove (5'), provides on the bottom, logically corresponding to each of the two areas (r'-r"), axial vertical holes (8), on whose inside it is vertically movable, following a stroke (yl), a relative nail-like feeler (9). Said feeler (9), in correspondence to the upper end, is provided with a head (9') with a fork-like or even with "U"-like shape, suitable to touch with the two angled points and permanently, the back of the sheet (B), while on the other side said feeler (9), interacts with a relative measuring group which transmits the data to a data logic process unit of the information thus acquired. In this case, the measuring system of the bending angle " ", that concerns at least the two end areas (r'-r") uses substantially four measuring points for each of them, respectively, two static ones (Re Fig.2) which correspond to the centre of the curvature radius of the corners (6, 7) of the groove (5') of the matrix (5), and two dynamic ones (Rt Fig.2), as feeler fork points (9",9'") symmetricaly placed one to one side and one to the other side of the bending corner axial line; both operating on the back of the sheet (B). In this case, the two dynamic points (Rt), will be diametrically opposed in respect to the bending axis (Y'-Y"), where the horizontal distance between the centres (Re) and (Rt) is not always constant (Ce), whereas the distance (Ci) between said two dinamic feeler points (Rt) is constant. In substance, we have four feeling points (2xRc+2xRt) of which two static detecting points (Re) and two dynamic detecting points (Rt) that integrated in a movably dynamic feeler device (9) costitutes two feeler points (Rt), the total remaining four detecting points. Both couples of points beng divided symmetrically in position and number to one side and to the other side of said vertical axial plane passing on the bending corner line (yl) The detecting points result symmetric respect to the bending axis (Y'-Y"). While the position of the static detecting points (Re) is known to the data processing unit of the machine (A), the exact position of dynamic feeling points of feeler points (Rt), is detected by said feeler (9) fork-like shaped (9'), that is maintained pressed against the lower surface of the sheet (B), with the feeler points one on one side and the other to the other side of the bending corner line (Yl axis). Therefore, knowing the displacement (H2) between the static couple (Re) and the dynamic couple (Rt) it is possible to calculate the bending angle "α" as it corresponds exactly to the tangent of the radii (Re) and (Rt). To allow such a condition, the lower end of the feeler (9), passes along an elastically yielding projecting wing (10') of a transducer group, essentially including a slide (10), engaged along a guide (11) of an adjacent support, placed beneath the matrix. Parallel to said guide (11) there is an optical line (12) which reads, by comparing the displacement, the position of the slide (10), and sending the information, through an electronic component (13) to the data process central unit of the press-bending machine (A). In a variation the feeler (9) includes a stem, tapered downwardly, and longitudinally provided with a guide slot (15), that allows the passage along the hole (8) made on the bottom of the bending groove (5') of the matrix (5). In this case, the holding of the feeler (9), is ensured by two screws in axis (16), which both, can be finalized to the stop function. In a working cycle, when the sheet (B) is placed over the matrix (5), the four bend detection points (Re, Rt) of each area (r'-r"), are placed perfectly aligned and coplanar. In this condition, by means of the optical transducer group, the processing unit feels the position of the nail-like feeler (9), and considers it as a "0" value (Index). On the practical side, it is preferable that the data process unit provides that the feeler means (9) is put in position, touching the back surface of the sheet (B). By carrying out the bending, the sheet (B), curves penetrating toward the groove (5'), pushing consequently downwards also the fork-nail-like feeler (9), whose fork-like shaped end (9') remains in contact with the back of the sheet (B). Consequently, the program of the processing unit, will have to calculate mathematically, relating to the bending angle, the stroke (Y'-Y") of the descent of the punch (2), in function of the fixed distances, measurable between the fork-like shaped end (9') in contact with the sheet (B), and the other couple of points, known since their origin, given by the matrix groove corners (6, 7), thus establishing the required bending angle. In this way, it is obtained that the stroke (Y'-Y") of the descent of the punch (2), is the same stroke (yl) detected by the feeler (9), which, is read by the corresponding transducer. More in detail, the displacement (Y'-Y") of the punch (9) is checked, as previously disclosed, by a first series of optical lines (11) up to its contact with the sheet (B), and then the movement control is carried out by the optical lines (12) of the measuring devices (r'-r") of the bending angle. Initially, in a bending cycle, the upper cross-piece (1) of the pressing machine (A), descends at high speed carrying the punch (2) toward the matrix (5). Such displacement is electronically controlled, thanks to two linear transducers (14), placed to the sides of the press machine (A). Some millimetres from the sheet (B), the punch (2), slows and passes to the low speed up to touching the surface of the sheet (B). It is at this moment that the reading related to the stroke of the punch (2), is given in charge to the transducers placed on the bench, and in fact, it is the sheet (B) pressed by the punch (2), that pushes the feelers (9), that start the reading mechanisms. Once an eventual error between the bending angle "α" and the nominal angle is detected, the machine is pre-set for a subsequent and definitive bending cycle, which, without discharging the product (B), will be executed with correction parameters compared and obtained by the reading and processing of data collected in the previous phase. A variation to the previous solution (see Figs 8-9), a feeler (9), provides a means for the measuring the bending angle, of the type with measuring book-like hinged plane or papillon-like feeler. More in detail, the feeler is made up of a stem (17), coaxially housed respect to a hole (8) always obtained on the bottom of the matrix (5). While the lower end stresses a position transducer, of the above illustrated type, the upper end hinges a supporting surface (18), elastically yielding. In such case, said surface (18), has two specular wings (18'-18"), longitudinally hinged in an intermediate position, and having a fulcrum corresponding to the upper end of the stem (17). In a static condition, the wings (18'- 18") are perfectly coplanar with the flat and horizontal surface (19) of the matrix (5), because this same in proximity of the bending groove (5'), provides a lowered portion and such to compensate the thickness of said wings (18'-18"). Also in the groove (5'), corresponding to the tilted specular planes, it is obtained a seat (19') whose depth is such to house on the same plane respect to the longitudinal development of the same, said wings (18'-18") in working condition. Said wings (18'- 18") corresponding to said detecting points, one to one side and one to the other side of said axial vertical plane passing on the bending corner line (Yl). The press-bending machine (A), can include a punch (2) suitable to ease the keeping in position of the sheet (B) during the bending phase, following a first one, for the removing of the bending angle difference noticeable because of the elastic return of the same. More in detail, the tool (2) applied along the lower base of a cross-piece (1), in a press- bending machine (A), can comprise at least one presser (20), in this case two of them intercalated along the same, elastically yielding, one for each end. In this case, for holding up the presser (20) in-line with the punch (2) it is used a tool holder (21). Said tool holder (21) has a vertical guide bending groove (22) and a stroke stopping tooth (21') obtained along a wall of said guide (22). In this case, an engaged vertical movement is allowed to the pressor device (20), respectively: on one side by the bottom of the guide (22), which during the working phase allows to have the contact end of the presser device (20) at the same level of the contact line of the punch (2). On the other, the engagement offered by said stop tooth (21'), is aimed at limiting the protrusion of the presser device (20). In this case, the presser device (20) being elastically recalled downwards, in a static condition it tends to protrude in respect to the contact line of the punch (2) of a size equal to about. 2-3 mm. In a hypothetical operative condition, consequently, it is found that the punch (2) at the end of the first bending, re-ascends slightly and stops allowing the sheet (B) to temper, slightly lifting because of the natural elastic return. In this circumstance, the punch (2) deviates just a little from the surface of the sheet (B) except for the lateral pressers (20) that, released, rest on one or more points of the surface of the sheet (B) maintaining it in position, until a new descent of the cross-piece (1) and therefore allowing the tool (2) together with the pressers (20) to pass again on the same bending. A further alternate solution is disclosed in figures 11, 12, that show a pressing- bending device having an upper part (Al) and of a lower one, the first (Al) essentially dynamic in respect to the second static one. The first one includes an elongated punch (101). The second one includes an elongated matrix (102) that has longitudinally, at least one longitudinal bending groove (102') that determines the bending angle "α" of the metal sheet (B) subjected to a bending cycle. In this case, along the longitudinal bending groove (102'), at least one measuring area, of said bending angle "a" is provided, for example two of them, placed at the ends of the elongated bending groove (102'), or near to the sheet ends (B). In said matrix, on the top of said elongated bending groove (102'), the corners obtained bv the intersection of the tilted planes with the horizontal plane of the elongated matrix (102) realizes two symmetrical opposite detecting points (103, 104), on which works the sheet back (B) in bending phase. The bending groove (102'), provides on the bottom, corresponding to each of the two detecting areas (r', r"), holes (105), on whose inside a relative feeler (106) is vertically movable following a stroke (v^**^*), said feeler being realized as an "Y" shape. Said feeler (106), is substantially made up of two Y-rods, whose upper ends make up respective fork (106', 106"), Y-like or U-like shaped, one placed on the inside or aside in respect to the other, having a different distance between centres and between the relative bend detecting points (107-107'; 108-108'). More in detail, the fork (106') has a distance between centers between the respective substantial points (107, 107') wider than that of the fork (106"), whose substantial points (108, 108') define a distance between centers shorter than the previous one. In this case, it is found that the median axis passing through said forks (106', 106") corresponds to the axis (yl) of the stroke of the punch (101). With regard to the lower ends of the rods including on the upper part two forks (106', 106"), they are engaged with corresponding elastically yielding means (1013, 1013'), in this case made up of compression helical springs, and each engaged with a relative position transducer group. Purpose of the position transducer group is that of communicating with a data process logical unit of the press-bending machine, giving the data relative to the different stroke from each single fork (106', 106"), carried out as a consequence of the pressure perpendicularly exerted by the elongated punch (101). In this way, two specular planes can be detected, corresponding to the back (lower surface) of the bent sheet (B), comparing the difference in height found between the respective substantial points (107, 108) and (107', 108'). Considering Figure 13 to 16, another solution of the measuring system of the bending angle is provided, this solution consists in providing the measuring device, associated along the verticallv movable punch (101). In this solution, the feeler means are two and both are dynamic feeler means as the previous solution but placed above the sheet, on the punch. Said feeler means detect the bending on the sheet (B) on the upper surface of the metal sheet (B). The solution consists in providing to the punch (101), two slides, respectively (109 and 1010), made up of two metallic elastically yielding plates, with independent stroke, essentially rectangular, of which the first (109) is wider than the second (1010) at least in correspondence of the lower square heads (109', 1010'), whose end corners have a ray-Hke disposition. A characteristics of said slides (109, 1010), is to provide a common central slot (1011) used as a sliding guide, providing engaging means (1012) of engagement of both said slides (109, 1010), keyed to said elongated punch (101), said guide slot (1011) being obtained in correspondence of the median axis (yl) corresponding to the stroke of said punch (101). Obviously the shape of the elongated punch (101) can be modified, in that case, the median axis (yl) may also not necessarily correspond to the stroke of the elongated punch (101). Both lower ends (109', 1010'), of said slides (109, 1010), are perfectly flat and with the end corners having a ray-like disposition, so that, with the punch (101) in a non- operative condition, they are coplanar and coinciding with the working end of the punch (101). The respective four dynamic bend detecting points are angled and their angle is 90° so allowing the perfect measuring even of a small bending angle. In other words the end of the two feelers (110; 109) are rectangular and in this way produce two couple of corners for each one (109'-1010' ; 109"-1010"), said corners being the claimed bend detecting points. In the same condition an arrangement of the square heads (1097109", 1010'/ 1010"), of said slides (109, 1010) is also obtained, perfectly parallel as regards the plane surface of a sheet (B) to be subjected to a pressing-bending cycle. In this way, to the action of the punch (101), that touches the sheet (B), corresponds a different stroke of the square heads (1097109", 101071010"), of said slides (109, 1010), detecting for each side, corresponding to two points given by the relative corners, two specular tilted planes. In this case, the different stroke of the slide feelers (109, 1010), by corresponding position transducers groups, is communicated to the logical unit of the pressing- bending machine, for the relative data processing.

Claims

Claims 1. A press-bending machine to bend metal sheets, with measuring and control system of the bending angle, of the type in which the press-bending machine has: ΓÇó an upper vertically reciprocal elongated bending punch (2J01); ΓÇó a lower static elongated bending matrix (5-102) with al least a longitudinal bending groove (5'- 102'); ΓÇó feeler means, having bending detecting points, to measure the respective bending movement of the metal sheet in bending, on said bending groove, to control and command by data process logic unit the bending parameters of bending process in said bending machine, characterized in that all said bending detecting points are conceived in such a way to be divided by an imaginary vertical plane passing on the bending corner line of the bending metal sheet (yl), in two sets of bending detecting points, one set of detecting points to one side and one of detecting points to the other side (6-9" 17-9'"; Rc-Rtleft I Rc-Rtright ; 18718" ;108'-107'/108-107; 109'JOIO' / 109"-1010").

2. A press-bending machine as claimed in claim 1 characterized in that said bending detecting points are four and have an angled shape (6-9"; Rc-Rtleft ;108'-107'; 109'- 1010' / 7-9"'; Rc-Rtright ; 108-107; 109╬æ010").

3. A press-bending machine according to the previous claim characterized in that the angle of said detecting point is equal to of more than 90┬░.

4. A press-bending machine according to the previous claim characterized in that said detecting points are extended in a contact surface that contact the surface of the bending sheet (B) and follow its bending movement (18'-18")

5. A press-bending machine according to previous claims characterized in that the bending machine provides the following bending steps: - the prearrangement on the working bench of at least one sheet foil (B), up to intersecting the vertical axis (Y'-Y") of descent of the upper cross-piece (1) for the supporting of a punch (2), towards the underlying matrix (5), supported bv a lower cross-piece (4); in which on the intrados of the sheet foil (B) rested on the matrix (5), passes permanently at least one feeler means (9) made up of a measuring fork (9') interacting with a position transducer, communicating with a data processing logical unit that controls said pressing-bending machine (A); - the carrying out of a first descent phase of the upper cross-piece (1) supporting the punch (2), towards the underlying matrix (5) supported by a lower cross-piece (4), pressing-bending the sheet foil (B) and determining a corresponding displacement (yl) along the vertical axis of said feeler means (9), which, interacting with a position transducer, communicates to the processing unit the data relative to the stroke carried out by the same; - at the end, in the proceeding with the re-ascent of the upper cross-piece (1) and of the relative punch (2), carrying out contextually the reset of the feeler means (9) in an original condition.

6. A press-bending machine according to previous claims characterized in that it is structured for operating as follow: - measuring in the first phase of a working cycle, by at least one feeler means (9) fork- like shaped (9') permanently in contact with the sheet foil (B), a bending angle different respect to the preset nominal one, and - operating a data process unit with correction values to ensure the consent to the press-bending machine (A), without discharging the product thus obtained, and - to perform at least a second descent phase of said punch (2), towards the underlying matrix (5) up to pass again on the same bending angle.

7. A press-bending machine according to previous claims characterized in that it is structured for operating as follow: - measuring in the first phase of a working cycle, by at least one feeler means (9) fork- like shaped (9') permanently in contact with the sheet foil (B), a bending angle different respect to the preset nominal one; - the punch (2) at the end of the first bending, slightly ascends allowing the sheet (B) to temper, up to moving away just a little from the surface of the sheet (B) except for a pressers (20) that, released, touch on more points of the surface of the sheet (B) maintaining it in position, up to a new descent of the cross-piece (1), so that said punch (2) together with said pressers (20) carries out again a bending phase.

8. A press-bending machine according to previous claims characterized in that the measuring system of the bending angle (╬▒) that concerns at least the two end areas (r'- r") of a press-bending machine (A), is made up substantially of four measuring detecting points for each, respectively two static ones (Re) which correspond to the corners (6, 7) of the groove (5') of said matrix (5), and two dynamic ones (Rt), such as specular surfaces and main points (9",9'"), of contact of the fork-like end (9') of said feeler (9), on the lower surface of said bending sheet (B).

9. A press-bending machine according to previous claims characterized in that it comprises at least one improved measuring device of the bending angle on four points (r'-r"), wherein the exact position of a couple four dynamic feeler points (Rt), is measured by said fork-like shaped feeler (9-9'), that maintains itself pressed against the back of the sheet (B) in the same moment in which said punch (2) passes on the sheet (B), while, the lower end of the feeler (9'), passes along a projecting wing (10') of a transducer group, including essentially a slide (10), engaged along a guide (11) of an adjacent support, placed beneath said matrix (5), and in which parallel to the guide is an optic line (12), which reads, by comparing the displacement, the position of the slide (10), sending the information, through an electronic component (13) to said data process unit to command and control the working and operating conditions of said pressing-bending machine (A).

10. A press-bending machine according to previous claims characterized in that the shape of the fork of said feeler means (9'), resembles a "U" shape obtaining two substantial and specular points (9"/9'"), one to one side and one to the other of the vertical plane passing on said bending corner line.

11. A press-bending machine according to previous claims characterized in that the horizontal distance between the centres (Re) and (Rt) is not always constant (Ce), so as constant (Ci) is the distance between centres between the two centres (Rt) of the feeler (9) fork-like shaped (9').

12. A press-bending machine according to previous claims characterized in that the dynamic two points (Rt), are symmetric respect to the bending axis (Y'-Y"), while the static points (Re) are external to said first ones.

13. A press-bending machine according to previous claims characterized in that the measuring groups of the bending angle "╬▒" consist of two measuring areas, respectively (r', r") lateral respect to said bending sheet (B).

14. A press-bending machine according to previous claims characterized in that in a working cycle, when the sheet (B) is placed over the matrix (5), the four measuring points (Rc,Rt) of each area (r'-r") are perfectly aligned and coplanar.

15. A press-bending machine according to previous claims characterized in that said feeler (9), includes a stem, longitudinally provided with a guide slot (15), for the passage along a hole (8) made on the bottom of the groove (5') of said matrix (5), and in which passing through said slot (15) are provided, in axis, some guiding means (16).

16. A press-bending machine according to previous claims characterized in that said punch (2) applied along the lower base of a cross-piece (1), in a pressing-bending machine (A), includes along the same, at least one adjustable elastically yielding presser means (20).

17. A press-bending machine according to previous claims characterized in that for holding said presser means (20) in-line with said punch (2) is used a tool holder (21), which has a vertical guide groove (22) and a stroke stopping tooth (21') obtained along a wall of said guide (22).

18. A press-bending machine according to previous claims characterized in that said presser means (20) carries out a vertical movement, engaged respectively: - on one side by the bottom of the guide (22), which in a working phase allows to have the contact end of the presser (20) at the same level of the contact line of the punch (2); - on the other, by the said stopping tooth (21'), aimed at limiting the protrusion of the presser (20).

19. A press-bending machine according to previous claims characterized in that said presser means (20) when elastically recalled downwards, in static condition it tends to protrude in respect to the contact line of the punch (2) of a size equal to about. 2-3 mm.

20. A press-bending machine according to previous claims characterized in that a measuring means of the bending angle, including a feeler (9) is provided with a measuring plane (18) book-like hinged.

21. A press-bending machine according to previous claim characterized in that said feeler (9) is provided with a measuring plane (18) book-like hinged and, is made up of a stem (17), coaxially housed respect to a hole (8) obtained on the bottom of said matrix (5), and in which while the lower end stresses a position transducer, the upper end hinges a surface (18) elastically yielding, for supporting said bending sheet (B).

22. A press-bending machine according to previous claim characterized in that said surface (18), has two specular wings (18'), longitudinally hinged in intermediate position, and having fulcrum corresponding to the upper end of the stem (17).

23. A press-bending machine according to previous claim characterized in that the upper edge of said matrix (5) in proximity of said groove (5'), corresponding to the tilted specular planes, provide a lowered portion, such to compensate the thickness of said wings (18'), allowing to house in the same plane respect to the longitudinal development of said groove (5'), said wings (18') in working condition.

24. A press-bending machine according to previous claims characterized in that it is structured to have a measuring device on four points of the bending angle, in a press- bending process of the sheet, to work as follows: - advancement on the working bench of at least one metal sheet (B), up to intersecting the descent vertical axis of the upper cross-piece supporting a punch (101), towards the underlying matrix supported bv a lower cross-piece; - carrying out a first descent phase of the upper cross-piece supporting the punch (101), toward the underlying matrix (102) supported by a lower cross-piece, press- bending said sheet foil (B) and determining a corresponding displacement along the vertical axis of a feeler means, which, interacting with a position transducer, communicating to said data process unit, supplying the data relative to the stroke carried out by the same; - carrying out of at least one partial ascent of said punch (101), carrying out the reset of said feeler means in an original condition; - detecting in the first phase through said feeler means, a bending angle different in respect to the preset nominal one, said processing unit ensuring the consent to the press-bending machine, not discharging the product thus obtained, for carrying out at least one second descent phase of said punch (101), towards the underlying matrix (5) up to pass again on the same bending angle (╬▒), to then proceed with the product discharging; - and wherein is provided that at least one feeler means, for detecting the bending angle "╬▒" on the intrados or on the extrados of the sheet (B) is made up of two elastically yielding and independent elements, the one inside or adjacent to the other, whose heads being suitable to be placed in contact with the sheet foil (B), are provided with relative four detecting points, of which two for each element having distance between centres different from the remaining two ones.

25. A press-bending machine according to previous claims characterized in that it has a measuring device on four points of the bending angle, having at least one feeler means provided along said bending groove of said matrix (102), said feeler being made up of a couple of forks (106', 106") mutually interacting, the one inside or adjacent respect to the other, in such a way that the median axis of both said forks (106', 106") coincides preferably with the axis (yl) of said punch (101), and in which said forks (106', 106") are elastically yielding and are downwardly connected with a relative position transducer communicating with a data process logical unit that manages said pressing- bending machine.

26. A press-bending machine according to previous claims characterized in that said feeler means for measuring the folding angle "╬▒", is provided along the punch (101) able to pass on an underlying matrix, said feeler means being made up of two slides (109, 1010) interacting, elastically yielding, connected with a relative position transducer communicating with a data processing logical unit that manages said press-bending machine, the one inside or adjacent respect to the other, whose lower ends are made up of square heads (109', 1010') having different width and being flat with the end corners placed like rays.

27. A press-bending machine according to previous claims characterized in that said feeler means (106), is essentially made up of two rods, whose upper ends make up two forks (106', 106"), shaped like a fork, that is like a "U", the one inside or adjacent respect to the other, having a different distance between centres between the respective substantial points, respectively (107, 107') and (108, 108').

28. A press-bending machine according to previous claim characterized in that said feeler means fork (106') has a distance between centres between the respective substantial points (107, 107') wider than the one of the fork (106"), whose substantial points (108, 108') define a distance between centres lower than the previous one, and in which the median axis passing through said forks (106', 106") corresponds to the axis (yl) of the stroke of the punch (101).

29. A press-bending machine according to previous claim characterized in that the lower ends of the rods including on the upper part of said two forks (106', 106"), include corresponding elastic yielding means (1013, 1013'), and each is engaged with a relative position transducer group.

30. A press-bending machine according to previous claims characterized in that said feeler means consists of two upper slides, (109 e 1010), sliding in said punch and having an independent stroke, and providing downwardly of the square heads (109', 1010'), of which the first wider than the second.

31. A press-bending machine according to previous claim characterized in that said slides (109, 1010) provide a common central slot (1011) finalized to be a sliding guide, providing means (1012) for the engagement of both said slides (109, 1010), keyed to the punch (101), said guide slot (1011) being obtained in correspondence of the median axis (yl) corresponding to the stroke of said punch (101).

32. A press-bending machine according to previous claim characterized in that both lower ends (109', 1010'), of said slides (109, 1010), are perfectly flat, so that with the punch (101) in a not operative condition , they are coplanar and coinciding with the working end of the punch (101).

33. A press-bending machine according to pervious claim characterized in that the higher ends of said two previous (109, 1010), are connected with a relative position transducer group, communicating with said data process logic unit to command and perform working operation of said press-bending machine.

34. A press-bending machine according to previous claim characterized in that it has at least a axially slidable bending feeler means realized substantially in a Y-shape.