EP0125974A1 - Forming press, particularly a folding press - Google Patents

Abstract

1. A forming press equipped with two tables (1, 2) one of which is mobile and which are each exposed to points of thrust resulting from the direct or transmitted action of jacks (16, 17, 19) and/or the reaction of fixed supports (14, 15) one of the tables of the press being exposed to a whole number _n of points of thrust, at least equal to two, and the other opposite table to (n+1) points of thrust which are offset and alternate two by two with the _n points of thrust of the first table in relation to lines parallel with the direction of movement of the mobile table, said points of thrust of the two tables being disposed symmetrically in relation to the median plane perpendicular to said tables, said press being characterised in that the offset of the points of thrust of one table in relation to the other, which is a function of the total possible forming length, and the distribution of the forces over the tables are determined in such a way as to obtain (n+1) common and substantially aligned points on the curves of longitudinal deformation of the tables, including the two end points.

Description

The invention relates to a forming press and more particularly to a press brake.

The forming presses generally comprise two aprons, one of which, called a slide, is mobile.

The aprons are equipped with means for carrying forming tools, the sheet being arranged between the tools of the aprons to be shaped under the combined action of the slide and the opposite fixed apron.

The slide is generally moved hydraulically by jacks but other pneumatic or mechanical means can obviously be used.

A conventional arrangement of a press brake consists in subjecting the slider to the action of two end jacks while the fixed deck rests on two supports located substantially in alignment with said jacks relative to the direction of movement of the slider.

In this type of arrangement, known as lateral thrust, the sheet thus formed between the tools subjects them to an almost uniformly distributed load, so that each deck is substantially under the same loading and deformation conditions.

However, it is clear that in this case the longitudinal deformation curves of the decks, each in the form of a single arc, are substantially symmetrical with respect to the plane of separation of the decks so that the maximum difference between the decks is at near the middle of the thrust points (cylinders and fixed supports) and represents twice the maximum deformation of each deck.

The maximum difference between the two aprons is an important parameter of the precision of the fold produced and in the above-mentioned case the two aprons in action being more apart in the middle than at the ends, the fold will be more open in the center than in said ends,

To decrease the maximum distance between the two deformed aprons més and thus improve the fold of the sheet, it was imagined to submit one of the aprons to two end cylinders or respectively two supports and the other apron to a support or respectively one or more cylinders arranged in its center ( provision hereinafter referred to as central thrust).

In this case the deformations of the aprons, also each in the form of an arc, are curved in the same direction and the maximum difference between the two aprons is significantly reduced since in this case the maximum difference is obtained by subtracting the arrows of each deformation curve, whereas in the case of lateral thrust, the maximum deviation was obtained by adding said arrows.

It is also possible to imagine a lateral thrust device with compensation by one or more median cylinders.

Obviously the maximum differences of the aprons are also a function of other factors and in particular of the inertia of the aprons. For example, for substantially equal maximum deviations between the two lateral thrust and central thrust arrangements, the inertias of the decks of the central thrust arrangement would be considerably reduced.

However, the calculation shows that the deformation curves of the aprons have different mathematical forms so that they cannot be parallel, contrary to what is generally asserted in this case.

In the central thrust arrangement if the maximum deviation of the decks is reduced compared to the lateral thrust arrangement, it nevertheless has a serious drawback.

In fact, in the lateral thrust arrangement, if the maximum deviation is significant, on the other hand the sheet formed remains substantially in the plane of symmetry between the two decks, while in the case of central thrust, the sheet is forced to follow a line located substantially between the two deformation curves. In some cases this drawback causes a saber-like deformation on the workpiece, although the folding angle throughout it is fairly correct.

The object of the invention is to propose an arrangement which makes it possible to minimize the maximum difference between the two aprons and to reduce the maximum deformations of each deck in order to minimize the "saber" effect mentioned above. For a press brake for example, reducing the maximum gap reduces the tolerance gap on the fold.

It is therefore a question of preserving, or even improving, the best results of the known art concerning the maximum deviation while at best reducing the deformation arrows.

It is also clear that if the invention is more particularly intended for press brakes, it also relates to all kinds of presses, for example planing, stamping etc.

The above-mentioned aim is achieved according to the invention, surprisingly, by departing from received ideas.

Indeed, the forming press according to the invention, each deck of which is subjected to thrust points, resulting from the reaction of fixed supports and / or from the direct or transmitted action of jacks, is remarkable in that the distribution and the number of thrust points of each deck are such that the longitudinal deformation curve of each deck in action for forming over the entire length of the press, is wavy and symmetrical with respect to its midpoint while the two curves have maximums and minimums having substantially the same longitudinal coordinates.

The deformation curves are therefore wavy and no longer reduced to a single arc as before, which is a priori original compared to the goal to be achieved.

According to a preferred embodiment, one of the decks is subjected to an integer number n of thrust points, at least equal to two, while the other opposite deck is subjected to (n + 1) thrust points which are offset and alternated two by two with the n thrust points of the first deck relative to parallels to the direction of movement of the movable deck, said thrust points of the two decks being arranged symmetrically relative to the median plane perpendicular to said decks.

Advantageously, the offset of the thrust points of one deck relative to the other, which is a function of the length of total forming possible, and the distribution of forces on the decks are determined so as to obtain (n + 1) common points and substantially aligned on the deformation curves including the two end points, and this assuming d '' forming over the entire length of the aprons.

The invention further recommends that the inertia ratio between the two decks is preferably determined so as to obtain a maximum difference between the deformation curves, as small as possible.

It is also possible to vary the inertias along each deck as will be said below.

The invention also provides a particular and original arrangement of the intermediate thrust points in the case of composite decks, as well as servo means, in particular for distributing the forces on the decks.

• - la figure 1 est un schéma montrant la disposition des points de poussée dans le cas d'une presse à "cinq points^m,
• - les figures 2a à 2d sont des graphiques représentant les courbes de déformation des tabliers en fonction de diverses caractéristiques,
• - la figure 3 est une vue simplifiée en perspective, d'une presse selon un mode de réalisation, avec, par endroits, des arrachements pour une meilleure compréhension,
• - la figure 4 est un shéma de principe des moyens de commande et d'asservissement.

The invention will be clearly understood on reading the description which follows, of an embodiment of a press brake given by way of example and which refers to the appended drawings in which:

• FIG. 1 is a diagram showing the arrangement of the push points in the case of a "five point ^m " press,
• FIGS. 2a to 2d are graphs representing the deformation curves of the decks as a function of various characteristics,
• FIG. 3 is a simplified perspective view of a press according to one embodiment, with, in places, cutaway for better understanding,
• - Figure 4 is a block diagram of the control and servo means.

Figure 1 shows the principle of the invention for a so-called five-point thrust, each thrust point represented here by a double arrow which can be, as has already been said, a fixed support or the direct or indirect transmission of the action d 'a cylinder.

The distribution of the bending force F is shown on the. Figure 1 using a coefficient k which will be discussed below and assuming a total possible folding length equal to 2L.

The thrust points of the upper deck ( _s in FIGS. 1 and 2a to 2d) are three in number symmetrically arranged and those of the opposite lower deck (i) are two.

As can be seen, the thrust points of the lower deck are offset by an A value from the end points of the upper deck and alternate with them (the value of being a proportional function of 2L).

The deformation curves for this type of arrangement, in rectangular coordinates x and y (x being considered in the direction of the length of the decks) are shown in FIGS. 2a to 2d).

The curves 2a to 2d correspond of course to mathematical functions which make it possible to study the maximum difference (Emax) between the two curves.

In addition it should be noted that the curves 2a to 2d are made in the hypothesis of a folding over the entire length 2L possible and for ine-ties Is and Ii constant along each deck (s) and ( i).

= J donné, pour que les deux courbes aient trois points communs (M et les deux points extrêmes 0 et 0'), c'est-à-dire pour passer de la courbe 2a à 2b. Autrement dit k est sous cette condition fonction de λ et J.The inventor found that there was a relationship between k and the values of the shift λ, for an inertia ratio

= J given, so that the two curves have three common points (M and the two extreme points 0 and 0 '), that is to say to go from curve 2a to 2b. In other words k is under this condition a function of λ and J.

By adding the condition so that the three points 0, M, and 0 ′ are substantially aligned (FIG. 2c), that is to say so that the middle of each deck is substantially in alignment with its ends, it is then possible to determine the values to be given to k and λ.

Finally by looking for a minimum for Emax we can optimize the value of J.

Figures 2a to 2c are made on the assumption of J = 1 and we can see in Figure 2d, the curve (s') obtained with an optimized value of J (we can note in passing that the minimum of Emax for a value of J given in this case 1 in FIG. 2c corresponds substantially to the alignment of the three points.

The value L will be imposed by requirements (folding capacity equal to 2L) and if it is not possible then to choose exactly the values of k, J and λ, determined above, according to the other manufacturing constraints (total weight, cost, etc.) it will always be possible to determine the best value (s) for one or two parameters as a function of the value (s) set for the others, all the more so as the results obtained exceed the expectation of agreement between the calculation and the material tolerances.

FIGS. 2c and 2d clearly show, moreover, that the fact of imposing an alignment at the three points 0, M and 0 ′ requires that the axis of the sheet which would happen to be disposed between the decks, to be brought back to the vicinity of the straight line (it is clear that the curves of FIGS. 2a to 2d are shown without regard to the sheet).

In what has been said above, the inertia (Ii, Is) of each deck was assumed to be constant throughout said deck but it is conceivable to further improve the device by imagining a variation of inertia along the length of at least one of the decks to bring its deformation curve as close as possible to the straight line and / or further reduce the maximum difference between the deformation curves.

Technically it is possible to obtain the results described above in numerous ways. The movable apron or slide can be both the lower apron and the upper apron, these can also be monobloc or composite. Similarly, the pushing points can be push cylinders, cambering or correction cylinders or fixed supports.

Figure 3 shows a possible embodiment.

In the example shown in Figure 3, it is the upper deck 1 which is movable and which is hereinafter referred to as a slide while the lower deck 2 is fixed.

The slide 1 and the fixed deck 2 are mounted in a frame formed by two flanges 3 and 4 joined together notably by a bracing beam 5 also serving as distribution box.

The slider 1 slides with the aid of transverse and longitudinal guide means which are not more particularly shown.

The slide 1 is in this example, a composite deck and comprises a central core 6 to which two lateral cheeks 7, 8 are placed, arranged on either side of the core 6.

The cheeks 7, 8 and the central core 6 are joined together by pins or pins 9 and 10.

The fixed deck 2 is composed in substantially the same way by a central core 11 secured to two cheeks 12 and 13 by means of pins or pins 14, 15.

The slide 1 is moved by jacks 16 and 17 arranged at its ends and in such a way that they act on the cheeks 7 and 8 of the slide and therefore, by reaction of the pins 9 and 10, on the central core 6, which as the drawing shows, goes beyond said cheeks so that it will act on the sheet to be folded by means of a tool with which it will be equipped. In the example shown, the cylinders 16 and 17 are double and the central thrust axes pass through the pins 9 and 10.

The cheeks 12 and 13 of the deck 2 have on the top a beam 18 intended to receive the tool combined with that carried by the slide so that here the force is transmitted by the pins 14 and 15 to the central core 11 assumed to be fixed.

It is clear that this is an example of an embodiment and that it is possible to imagine at least one of the aprons in a monobloc form or to reverse the working parts of the aprons which could be the cheeks 7 , 8 for the slide 1 and the central core 11 for the deck 2, rather than, as shown, the core 6 of the slide and the cheeks 12, 13 of the deck 2.

In the embodiment shown, the central part of the slide (in the direction of its largest dimension) has a hole in which a cambering cylinder 19 is arranged.

5 This cylinder 19 is arranged so as to urge the core cen trale 6 of the slide by resting on the cheeks 7 and 8 (it could be the reverse with working cheeks 7 and 8). In a case of a one-piece apron, the jack 19 could for example be placed in a notch of said apron and bear on the beam 5.

We find indeed in the representation of Figure 3 the arrangement of the push points of Figure 1, namely a slide provided with three push points in the form of the pins 9, 10 (in reaction of the jacks 16, 17) and the jack 19 while the deck 2 has two push points in the form of fixed supports 14 and 15 offset from the push points of the slide.

Such a press is of course provided with a regulation and servo control assembly and FIG. 4 schematically shows, by way of example at least in part, such an assembly. In this figure we find, according to arrangements and shapes a little different than those of Figure 3 since it is a block diagram, the slide 1, the fixed deck 2, the frame flanges 3 and 4 , the thrust cylinders 16, 17 and the camber cylinder 19.

The jacks 16, 17 and 19 are controlled by servo valves S1, S2, and S3 respectively supplied by pumps P1, P2 and auxiliary pumps Pa.

Electronic and / or mechanical and / or hydraulic logic (not shown) takes information from control means such as the pedal shown diagrammatically in Pc, from data entry means (instructions) and from measurement means in the form of sensors. of force F1, F2 which permanently measure the bending force actually applied and its preparation with respect to the plane of symmetry of the press, of position sensors Cl, C2 which permanently measure the relative positions of the ends of the deck 2 and of the slide 1 and a moment sensor M which permanently measures the bending moment in the center of the slide and which will be discussed in more detail below (the oblique arrows shown in the drawing represent the connection with the logic).

The pedal Pc controls via the above-mentioned logic and the valves SI and S2: the advance, stop and return of the slide 1.

The data or instructions are entered by the logic input unit and relate to the nature, thickness and possibly the length of the sheet as well as the characteristics of the fold to be obtained (angle of the fold, dimensions of the tooling. ..) so as to determine a folding depth and therefore an end position of the slide.

The logic processing unit uses the instructions given and the information received from the measurement means to modulate the controls of the servo valves.

On approach, the comparison of the data of Cl and C2 makes it possible to control the parallel movement of the slider 1 relative to the deck 2 by acting on the valves Sl and S2.

The comparison of said position data with respect to a conventional position chosen also makes it possible to determine the end of the approach stroke (fast speed) and to switch to slow folding speed.

The functions described above are obviously the same in reverse movement (return of the slide).

During bending, the force F to be applied depends on the characteristics of the sheet (nature of the metal, thickness, length). This force F is generally determined by means of charts, or by calculation in the case of certain numerical controls, and then preset on the machine. The force sensors F1 and F2 which measure the distribution of the thrusts and which are arranged in the flanges of the frame or the pins or elsewhere (jacks, etc.) thus deliver two pieces of information to the logic which are the total force d, folding-F and, by difference, the eccentricity of the thrust.

By acting on Sl, 52 the logic thus controls the conformity of the real bending force with respect to the calculated theoretical value and the parallelism of execution of the fold. It can however be noted here that it is always the position sensors C1, C2 which serve as a servo reference for the parallelism, the offset data being used elsewhere.

All these means thus make it possible to take account of the characteristics of the sheet and of its position relative to the plane of symmetry.

The studies and calculations of the departure (Figures 1 to 2d) which made it possible to determine the values of J, k and A for producing the press were made on the assumption of a load uniformly distributed on the aprons, that is to say - say for a centered folding and also applying over the entire length of the press.

In the case of a folding over a partial and / or eccentric length, we have seen how the means described above can take this into account.

However, it is necessary to correct the data coming from the position sensors C1, C2 since the positions of the ends of the aprons do not correspond with the actual dimensions at the ends of the sheet and that in addition there is reason to enslave also the bending force, that is to say to act on the value to be effectively given to the coefficient k which depends on the eccentricity and the actual bending length.

The length of the sheet to be bent can be displayed and entered by the logic as already said, but it is particularly interesting and original to determine it by means of the sensor M, the measurements of which are a function of said bending length, of the force F and eccentricity.

Since the force F and the eccentricity are also captured, the logic can easily, from the information from the sensor M, deduce the value of k therefrom.

Many variants can be imagined as has already been said without departing from the scope of the invention (lower slide, two-point slide and fixed three-point apron ..). Furthermore, it is clear that the five-point embodiment can be extended to other embodiments with 7, 9 points, etc. (see even numbers) for which other camber cylinders than the cylinder 19 are provided. , which can be arranged as described above in the composite decks. In addition, the stress sensor M can be arranged otherwise, on the other deck, for example.

Finally, it is clear that if the description relates more particularly to a press brake, the invention is not limited to this particular type but applies to any kind of press to be formed.

Claims (9)

1) Forming press, each deck of which is subjected to thrust points, resulting from the reaction of fixed supports and / or from the direct or transmitted action of jacks, characterized in that the distribution and the number of thrust points of each deck are such that the longitudinal deformation curve of each deck in action for forming over the entire length of the press, is wavy and symmetrical relative to its midpoint while the two curves have maximums and minimums having substantially the same longitudinal coordinates. 2) A forming press according to claim 1 characterized in that one of the aprons of the press is subjected to an integer n of thrust points, at least equal to two, while the other opposite apron is subjected to ( n + 1) thrust points which are offset and alternated two by two with the n thrust points of the first deck with respect to parallels to the direction of movement of the movable deck, said thrust points of the two decks being arranged symmetrically with respect to in the median plane perpendicular to said aprons. 3) A forming press according to claim 2, characterized in that the offset of the thrust points of one deck relative to the other, which is a function of the total possible forming length, and the distribution of the forces over the aprons are determined so as to obtain (n + 1) common points and substantially aligned on the deformation curves including the two end points, and this in the hypothesis of forming over the entire length of the aprons. 4) A forming press according to claim 3, characterized in that the inertia ratio between the two decks is determined so as to obtain a maximum difference between the deformation curves as small as possible. 5) A forming press according to one of claims 1 to 4, characterized in that at least one deck has a variable inertia along its length so as to bring its deformation curve towards the straight line and / or to reduce maximum deviation between the deformation curves of the decks. 6) A forming press according to one of claims 2 to 5 characterized in that the intermediate push points at the end push points on the deck subjected to (n + 1) push points, result from the direct action or indirect actuators. 7) A forming press according to one of claims 1 to 6, at least one of the aprons of which is composed of a central core taken between two lateral cheeks to which it is secured, characterized in that some at least of the pushing points intermediaries of the apron or aprons are formed by jacks arranged so as to urge either the central core carrying the forming tool by bearing on the lateral cheeks, or the latter, then bearing the tool, by bearing on the central core. 8) A forming press according to one of claims 1 to 7 of which at least the movable apron or slide (1) is composed of a central core (6) taken between two lateral cheeks (7,8) to which it is secured, characterized in that the slide is provided with (n + 1) push points, the end points (9, 10) of which each result from the action of at least one push cylinder (16, 17), acting, either on the lateral cheeks (7,8) to transmit the force to the central core, or on the latter (6) to transmit the force to the lateral cheeks (7,8) while the intermediate push points are formed each by a jack (19) acting directly on the central core (6) or respectively the side cheeks (7,8) and by resting on the lateral cheeks (7,8) or respectively on the central core (6 ), the thrust points of the opposite fixed apron (2) being constituted by fixed supports (14,15). 9) A forming press according to one of claims 1 to 8 provided with sensors (Cl, C2) controlling the position of the aprons, force sensors (F1, F2) arranged to measure the distribution of the thrusts and a logic d servo, press characterized in that it is further provided with a sensor (M) disposed on one of the decks and giving information which is in particular a function of the eccentricity of the sheet to be formed and the length of this so as to allow the enslavement, by logic, of the distributed tion of the forces on the pushing (16,17) and bending (19) cylinders and possibly correcting the data of the position sensors (Cl, C2), in the case of forming over a partial length of the press and / or offset.

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