EP0542610B1 - Workpiece-supporting device for a bending machine - Google Patents

Abstract

Metal-sheet-following device for a bending press, including a pivoting support (6) actuated by one or more articulated systems, each of them being constituted by at least two levers (9),(10) and two links (15),(17) forming, together with the support, at least two parallelograms which can be deformed in the manner of a pantograph. The fixed articulation points (7),(8) of the two levers on the one hand, and the articulation points (16),(18) of the links on the support on the other hand, are aligned with the point which is coincident with the axis of rotation of the metal sheet about the die edge. Rotational actuation of the assembly follows the movement of the moving table of the press by means of a control mechanism of the "master-slave" type which has the effect of minimising the following error in the metal sheet which is being bent. The metal sheet (5) is rendered integral with the support (6) but the latter may slide slightly in relation to its articulation points so as to follow the sliding of the metal sheet during the bending. The support may either be a plate or a set of arms, the spacing of which may be adjusted. The arms may be integral or independent. <IMAGE>

Description

The subject of the present invention is a sheet metal accompanying device during folding on a press brake according to the preamble of claim 1. During this operation, the sheet metal is clamped between an elongated punch called a counter-vee, fixed to the upper deck and a V-shaped matrix of the same length attached to the lower deck. The bringing together of these two tools causes a bending of the sheet between the two edges of the vee then a permanent deformation which constitutes the fold to be produced at the desired angle.

During this operation, if the fold to be produced is located near one of the edges of the sheet, leaving most of it in front of the press, this part pivots in the surrounding space with sudden acceleration to reach an angular speed which is d 'the larger the smaller the vee. Under these conditions, the moment created by the weight of the sheet, the center of gravity of which is far from the support line formed by the edge of the vee, causes this sheet to bend and a permanent deformation called a counter-fold, if the sheet metal is thin. To overcome this drawback, we must support the sheet in its movement which requires the action of two operators standing on each side of the sheet and trying to follow its movement. But synchronizing the arms of the operators with the movement of the sheet is difficult and very tiring, even dangerous.

Apparatuses of various types have been produced with a view to providing a solution to the problem, but these are not entirely satisfactory since they are either complex, as the apparatus described in US Pat. .

The difficulty encountered in the search for an effective solution stems from the fact that it is necessary to rotate the sheet support around an axis which coincides with the axis of rotation of the sheet around the die edge and that it is impossible to materialize this axis.

JP-A-59 147 716 discloses a sheet metal accompanying apparatus for a press brake as described in the preamble to claim 1. The apparatus of the invention is defined by claim 1.

The rotation control of the support results from the comparison between the value given by the linear sensor linked to the movable platform of the press and that given by the other linear sensor indicating the movement of the support system.

The consistency of the linear values read from the two sensors is obtained automatically.

The output signal from the servo device can act indifferently on a linear cylinder without defined orientation or on a rotary motor.

Several articulated systems can be placed at a certain distance from each other, each system being provided with its own support and each support being slaved to the movement of the part of the movable platform which is located in front of it.

The sheet being made integral with the support, the latter, according to a preferred embodiment, is connected to the articulated system by an elastic connection in order to follow the slight sliding of the sheet during folding.

• La figure 1 représente en vues de face et de profil,une presse-plieuse en cours de pliage et la formation du contre-pli sur une tôle de grand format.
• La figure 2 est un agrandissement schématisé de la zone de pliage
• La figure 3 est un vue de profil de l'avant de la presse équipée de l'accompagnateur de tôle suivant l'invention.
• La figure 4 est le schéma-bloc d'un asservissement électronique du type"maître-esclave"adapté à l'accompagnateur.
• La figure 5 est une vue de dessus d'un accompagnateur de tôle constitué de deux bras synchronisés mécaniquement.
• La figure 6 représente les deux bras indépendants asservis chacun en "maître-esclave" au vérin de presse le plus proche.
• La figure 7 est une vue de dessus d'un accompagnateur de tôle en forme de plateau.
• La figure 8 représente un détail de l'articulation d'une biellette d'actionnement sur le support.

Other additional characteristics and advantages of the sheet metal guide according to the invention will become more apparent from the following description of an exemplary embodiment given by way of indication with reference to the appended drawings in which:

• Figure 1 shows in front and side views, a press brake during folding and the formation of the counter-fold on a large sheet.
• Figure 2 is a schematic enlargement of the folding area
• Figure 3 is a side view of the front of the press equipped with the sheet metal guide according to the invention.
• FIG. 4 is the block diagram of an electronic control system of the "master-slave" type adapted to the attendant.
• Figure 5 is a top view of a sheet metal guide consisting of two mechanically synchronized arms.
• FIG. 6 represents the two independent arms each slaved as a "master-slave" to the nearest press cylinder.
• Figure 7 is a top view of a sheet metal support tray.
• Figure 8 shows a detail of the articulation of an actuating rod on the support.

As shown in FIG. 1, the press brake essentially consists of a frame (1), an upper deck carrying a punch (2) and a lower deck carrying a matrix (3) generally in the form of a vee. One of the two aprons is movable, which brings the tools together and the sheet metal (5) folds together, as shown in FIGS. 2 and 3. If the sheet has a large dimension in front of the press and is not not supported, it flexes and forms during folding a counter-fold (26) resulting from the "whiplash" caused by its acceleration at the start of folding and the moment created by its weight.

The operating principle of the guide as described in Figure 3 is similar to that of the pantograph. The fixed points (7) and (8) integral with the frame (20) of the device are aligned with the edge of the die (4); around these fixed points can pivot two levers (9) and (10), the lever (9) has two points of articulation (11a) and (12a); the lever (10) has a point of articulation (13a) and a light (14). A link (15) connecting the points of articulation (11a) and (13a) is articulated in (16a) on the support (6) while a second link (17) connects the point (12a) of the lever (9 ) at a second point of articulation (18a) of the support (6). Points (16a) and (18a) are aligned with the die edge (4). The two parallelograms formed by points (7), (8) (13a), (11a) on the one hand and (11a), (12a) (18a), (16a) on the other hand can deform to take the respective positions (7), (8), (13b), (11b) and (11b), (12b), (18b), (16b) so that the points (18b), (16b) integral with the support (6 ) always remain aligned with the vee edge and at constant distance from this edge when the levers (9) and (10) are rotated by any angle α.

In the example of FIG. (3) the rotation of the lever (9), therefore of the lever (10) which remains parallel to it, is obtained by a jack (19) articulated at (8) and the rod of which is connected at ( 11a) to the lever (9) and to the link (15). This cylinder can be hydraulic, as shown in the figure, electric or pneumatic. In all cases, it is controlled by a power member, not shown but which, in the example described, comprises a hydraulic distributor delivering to the jack an oil flow proportional to an electrical set point; this being determined by the servo system so that the angle α of rotation of the support (6) is constantly equal to the angle α of rotation of the sheet at the same time during folding.

For this purpose, the guide is electrically connected to the press. This has either original or in addition an incremental measurement rule (21) whose cursor (22) indicates the position and the speed of the movable deck (23). At the same time, the guide is equipped with an incremental rule (24) whose dimension is related to the angular movement of the lever (10). This rule (24) has a cursor (25) guided on the rule and controlled by the lever (10) using a sliding link represented by the light (14). The rule (24) is mounted on the frame (20) in a position perpendicular to the lever (10) when it is at rest. We then see that the displacement of the cursor from (25a) to (25b) is proportional to that of the cursor (22) of the press since it measures the penetration of the punch in the die and that, geometrically, the triangle formed by the points (25a), (25b), (8) is similar to that formed by the top of the punch, in its initial (27a) and final (27b) positions and the die edge (4) shown in Figure 2. Thus , in this exemplary embodiment, the consistency of the values read from the two sensors is purely mechanical.

The servo principle is described in the diagram in FIG. 4. The adapters (44) and (45) process the signals complemented by the sliders (22) and (25) in order to obtain, on an output, a counting signal. positive if the cursor moves in the fold direction and, on another output, a negative count signal if the cursor moves in the opposite direction.

The frequency-voltage converter (46) outputs a setpoint voltage proportional to the counting frequency of the adapter (44), positive if the counting is positive and negative otherwise.

The member for preselecting the folding vee (47) outputs a division ratio corresponding to the matrix chosen from an interface of the coding wheel type or the like.

The division block (48) receives the counting signals from the adapter (45) and outputs a quantity of pulses proportional to the division ratio of the preselection member (47).

The counting signals coming from the adapter (44) and the division block (48) are transmitted to the block (49) which outputs a signed digital value representative of the chase error of the attendant relative to the movable platform.

The converter (50) transforms this digital value into analog voltage. Thus, the setpoint voltages leaving the converter (46) and the converter (50) enter a P.I.D.block (51) (proportional, integral and differential) to generate, at the output, a control signal from the power unit.

The sheet metal guide can take various forms and three examples of embodiment are given in FIGS. 5, 6 and 7.

In FIG. 5, each articulated system has its own support arm (32), (33), the arms can be separated according to the width of the sheet; for this purpose, they can slide along the apron (34) of the press and find a place in the extension of this apron when they are not in use. Their drive can be independent or common, for example by means of a splined shaft (35).

In FIG. 6, the two support arms are independent and each arm is slaved to the movement of the part of the deck located opposite it; in practice, the arm (32) is slaved to the jack (28) and the arm (33) to the jack (29); each control being assigned a coefficient proportional to the distance between the axis of the linear sensor of the press managing this cylinder and the axis of the linear sensor of the corresponding arm. This arrangement makes it possible to accompany the sheet even when the fold is progressive from one end to the other, owing to a different adjustment of the two jacks.

In FIG. 7, the support is a plate (36) driven by at least two articulated systems.

In all cases, the device is made integral with the lower deck at precise horizontal and vertical distances depending on the width and height of the die. Most often, it can be moved along the lower apron of the press, as in Figure 3 using rollers (39a), (39b) rolling on a rail (30). Each arm will then have a locking system. The distance adjustment and the locking system are not shown in the figure.
In order not to inadvertently slide on the support during folding, the sheet is held on it, for example using suction cups (40) or any other means such as electromagnets or clamps.

During folding, the sheet metal pivots around the edge of the die (4) but we see in figure (2) that it slides on this edge since the segment (4) - (27b) is longer than the segment ( 4) - (27a). The device therefore comprises, according to Figure 8 a possibility of longitudinal sliding between the support (6) and the connecting pins (16) and (18). For this purpose the yokes (41) on which the links (15), (17) are articulated are slidably mounted on the plate (6) and are connected to the latter by means of elastic elements such as the springs ( 42) and held by screws (43). It is obvious that this solution is given by way of example, and that the device can be adapted to the sliding of the sheet in another way such as for example a sliding mounting of the holding members on the plate.

The principle of the sheet metal guide according to the present invention can be used on all types of press brakes with upper or lower movable deck. Due to its simple servo-control, it can be installed on rustic press brakes that do not have a digital control.

Claims (5)

1. Sheet-metal accompanying apparatus intended to be used on a bending press of the type comprising an upper table carrying a punch (2) and a lower table carrying a matrix (3), one of said tables being mobile, comprising

   a first sensor (21, 22) linked to the mobile table of the press,

   a support (6) that pivots about an axis parallel to the matrix (3) in order to support the sheet metal (5) during the bending operation,

   one or more articulated systems actuating said support, each of them being constituted by at least two levers (9, 10) and at least two connecting rods (15, 17) forming, together with the support (6), at least two parallelograms that are deformable in the manner of a pantograph; the control for rotating the assembly being determined so that the rotation of the support follows the rotation of the sheet metal about the edge of the matrix (4) during bending, the fixed articulation points (7, 8) of the levers (9, 10) on the one hand and the articulation points (1 6, 18) of the connecting rods (15, 17) on the support (6) on the other hand being aligned with the point that lies on the axis of rotation of the sheet metal about the edge of the matrix (4), and

   means (19) for rotating the support controlled by a servo-control device of the master/slave type between the mobile table of the press and the support, having the effect of minimising an error between the position of the support (6) and the desired position of the support (6) during bending,
   characterised in that said first sensor (21, 22) is a linear sensor that measures the penetration of the punch (2) into the matrix (3);

   in that the apparatus further comprises a second linear sensor (24, 25) measuring the position of one of the members (9, 10, 15, 17) of the articulated system in order to indicate the angular displacement of the support (6);

   and in that the control of rotation of the support (6) is such that said angular displacement of the support (6) is proportional to said penetration of the punch (2).
2. Apparatus according to Claim 1,
   characterised in that the control of rotation of the support (6) is such that the angle of rotation (α) of said support is constantly equal to the angle of rotation (α) of the sheet metal about the edge of the matrix (4) during bending.
3. Apparatus according to one of the preceding claims,
   characterised in that the output signal of the servo-control device acts indiscriminately on a linear jack (19) without defined orientation, or on a rotary motor.
4. Apparatus according to one of the preceding claims,
   characterised in that the support (6) comprises two independent arms (32, 33) each arm having an articulated system, the movement of each arm being slaved to the movement of the part of the mobile table that is located opposite it, assigned a coefficient of proportionality that depends on the distance between the axis of the first linear sensor of the press managing that part of the mobile table, and the second linear sensor for the articulation system of the arm (32, 33).
5. Apparatus according to one of the preceding claims,
   characterised in that the support is connected to the articulated system via an elastic link (41, 42, 43) oriented in the direction in which the sheet metal slides over the edge of the matrix (4).

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