The present invention relates to bending presses for sheet metal work and concerns in particular a device for setting a metal sheet in a reference position in a bending press which comprises at least one bending blade and at least one counterblade that together define a bend line, of which the bending blade is carried by a bladeholder, which is movable towards and away from the counterblade and is elongate in a first direction parallel with the bend line, which device comprises movement guide means carried by the bladeholder and extending in the above-mentioned first direction, and a pair of motorised slides adapted to move back and forth in the first direction on the guide means, and each slide comprises a respective reference block having a front reference face and a lateral reference face with which a front edge and a lateral edge, respectively, of the sheet engage, and in which each reference block moves back and forth in its respective slide in a second direction perpendicular to the first, towards and away from the bend line.

The invention has been conceived in its application to nu¬ merical-control bending presses, but can be applied to ben¬ ding presses in general.

Already known is a device of the kind described above in which the back-and-forth movement of each slide in the abo¬ ve-mentioned first direction is brought about by means of respective numerical-control electric motors. In this known device each slide carries a second numerical-control motor connected to the associated reference block in order to cause the latter to move back and forth in the above-men-

tioned second direction, independently of the movements of the slide in the first direction.

It is thus possible to position, with great accuracy, both laterally and frontally, the edge of a sheet, either to execute a first bend or to define once for all a "zero" po¬ sition to which the numerical control system of the press and its manipulator will refer when forming, in a metal pa¬ nel, all the other bends following the first bend.

The known device uses four numerical-control motors to po¬ sition the two reference blocks in the two above-mentioned directions. Numerical-control motors are expensive and it would be desirable to be able to use fewer of them, while still providing a device of the type in question whose pre¬ cision is no less than that of the known device with its four motors.

The chief object of the invention is to do precisely that.

According to the invention, this object is achieved with a device of the type described at the outset, characterised in that each slide incorporates a toothed bar that moves relative to the slide in the above-mentioned first direc¬ tion, and a gearing to convert the movements of the toothed bar relative to the slide into corresponding movements of the block in the second direction, in that each slide in¬ corporates selectively controllable means for locking and releasing the toothed bar relative to the slide, and in that the device also comprises, carried by the bladeholder, retaining means for immobilizing the toothed bar in a pre¬ determined position relative to said bladeholder, the ar¬ rangement being such that there is a biunivocal correspon¬ dence between, on the one hand, the positions of the slide along its guide means when the toothed bar is immobilised

in the above-mentioned predetermined position and, on the other hand, the position of the reference block relative to the bend line.

By these means it is possible accurately to adjust the po¬ sitions of each block in the first and second directions by means of just one electric motor, preferably of numerical- control type, for each slide.

Considering the case of just one of these two slides, the operation of adjusting the positions of the block in both directions can be accomplished in the following manner.

In order to make adjustments, the slide is traversed along its guide means in the first direction to a predetermined position. Once it is in this position, the retaining means carried by the bladeholder lock the toothed bar relative to the bladeholder and the slide is traversed further along its guide means, in either direction.

There is a biunivocal relationship between this further traversing of the slide along the bladeholder and a forward or backward movement of the reference block relative to the bend line.

The traversing movement of the slide, while the toothed bar is locked relative to the bladeholder and moving through the slide, is stopped when the block has reached, in the second direction, the desired forward or backward position.

The toothed bar is then locked relative to the slide in or¬ der to maintain the adjusted position of the block relative to the bend line, and the slide and toothed bar are traver¬ sed as one along the bladeholder until the block reaches the predetermined adjusted position in the first direction.

The invention also relates to a bending press incorporating a device according to the invention.

A clearer explanation of the invention is provided by the following detailed description, which refers to the accom¬ panying drawings, given by way of non-limiting example and in which:

Figure 1 is a perspective view of a bending press in¬ corporating a device according to a preferred embodiment of the invention,

Figure 2a is a schematic illustration from above which shows the way in which the metal sheet to be bent is posi¬ tioned by means of two reference blocks forming part of the device,

Figures 2b and 2c are respective partial illustra¬ tions, similar to that of Figure 2a, showing the position of a metal sheet in two alternative embodiments to Figure 2a,

Figure 3 is a fragmentary lateral view on a larger scale seen in the direction of the arrow III indicated in Figure 1,

Figure 4 is a lateral view similar to Figure 3 , on a larger scale and with a slide that has been partly section¬ ed in order to illustrate certain internal details,

Figure 5 is a perspective view of one of the slides of the device shown in Figure 1 and associated parts,

Figure 6 is a front view, partly sectioned in the ver¬ tical plane marked VI-VI in Figure 4,

Figure 7 is a fragmentary view from above, basically in the direction of arrow VII marked in Figure 5, in which certain parts are shown as transparent,

Figure 8a is a partly sectioned schematic front view of one of the slides of the device in one extreme position of adjustment,

Figure 8b is a lateral view similar to Figure 3 and on

a smaller scale, showing a situation corresponding to that in Figure 8a,

Figures 9a and 9b are drawings corresponding respecti¬ vely to Figures 8a and 8b and illustrating the slide in an intermediate position of adjustment, and

Figures 10a and 10b are also similar illustrations to those of Figures 8a, 8b and 9a, 9b respectively, in which the slide is shown at the opposite end-of-travel position from its position in Figure 8a.

Referring to Figure 1, a bending press of the vertical ty¬ pe, marked 10 as a whole, comprises a strong C-frame marked 12 as a whole.

The frame 12 in turn comprises a fixed lower part 14 and a reciprocating upper part 16 whose movements are driven by one or more hydraulic actuators (not shown) .

The tools of the press 10 (blankholder, bending blades and counterblades) will be briefly described later with refer¬ ence to Figure 3. For the moment it is sufficient to state that mounted inside the cavity formed by the C shape of the frame 12 is a bladeholder 18, likewise C-shaped, the bend¬ ing blades of which will be discussed later with reference to Figure 3.

Still referring to Figure 1, at the front of the press 10 is a table 20 on which metal sheets or panels are laid in order to be bent by the press 10.

The table 20 is provided with a manipulator, which may for example be of the kind disclosed and illustrated in Italian patent application TO94A000885 in the name of the present Applican .

All the movements of the press 10 and of its manipulator are preferably governed by a numerical-control apparatus identified conventionally by the reference NC in Figure 1, which also indicates its "console" .

Still with reference to Figure 1, the bladeholder 18 is elongate in a first direction X parallel with the bend line defined by the tools of the press . These will be discussed at a later stage.

The bladeholder 18 comprises movement guide means in the form of a rail 22 that extends in the first direction X. The rail 22 carries a pair of motorised slides 24 which are movable back and forth in the first direction X.

Each slide 24 is driven by its own electric numerical-con¬ trol motor 26, which is connected to its respective slide 24 through its own timing-belt drive 28 which extends along the bladeholder 18.

Each slide 24 has its own reference block 30.

The function of the reference blocks 30 will now be explai¬ ned with reference to Figures 2a, 2b and 2c.

In Figure 2a an operator has laid on the table 20 a metal sheet P which is to be bent.

In the case of Figure 2a the sheet P is rectangular. Its front edge is marked E _y and its lateral edges E _x .

In order correctly to position the sheet P, the numerical control system has positioned the two blocks 30 in both the first direction X and a second direction Y perpendicular to the first, and also perpendicular to the bend line BL defi-

ned by the press tools.

For the purpose of correctly positioning the sheet P, each block 30 has a right-angled concavity defined by a front reference face F _y which encounters the front edge E _y , and a lateral reference face F _x which encounters the corres¬ ponding lateral edge E _x of the sheet P.

In Figure 2b it is assumed that the edges E _x , E _y of a rec¬ tangular sheet P are not very accurate. In this case the corners of the sheet P where the edges E _x and E _y meet have each been cut back a small amount at N _x , N _y (up to a few fractions of a millimetre) . The edges to which precise re¬ ference can then be made are provided in this case by the cut-back portions.

In Figure 2c it is assumed that the corners of the sheet P to be bent include deep right-angled notches defining, on the one hand, accurate lateral edges E _x and, on the other, an accurate front edge F _y .

In this case the lateral and front reference faces F _x and F _y respectively of the blocks form a positive dihedral an¬ gle with each other.

Referring to Figure 3, the fixed lower part 14 of the press frame supports a fixed lower blankholder 32. The reciproca¬ ting upper part 16 of the press frame supports a strong front plate 34 (Figure 1) comprising a movable upper blank¬ holder 36 at its bottom end.

The bladeholder 18 contained in the cavity defined by the C shape of the press frame is also C-shaped and carries an upper bending blade 38 and a corresponding lower bending blade 40.

The lower bending blade 40 is designed to cooperate with a counterblade 42 defined by a projecting part of the upper blankholder 36; the upper bending blade 38 is designed to cooperate with a counterblade formed by a corresponding projecting part of the lower blankholder 32.

The bladeholder 18 can be raised and lowered by a numeric¬ al-control motor (not shown) so as to cause its lower bend¬ ing blade 40 to cooperate with the upper counterblade 42, or its upper bending blade 38 with the lower counterblade 44, as required.

The arrangement described above by way of example is simi¬ lar to that illustrated and described in detail in document EP-A-0 298 056, which should be referred to for further de¬ tails.

In the following description, which refers to Figure 3 et seqq, the device according to the invention for setting the position of a metal sheet in the bending press will be des¬ cribed in relation to its left portion only, and it will be understood that the elements of the portions on the left and right are mirror images of each other.

Referring to Figures 3 to 7, these - or some of them - show the rail 22, the left-hand slide 24, its electric numeric¬ al-control motor 26, its timing belt drive 28 and its block 30.

The lateral and front reference faces of the block 30 are again marked F _x and F _y .

The slide 24 consists of a generally parellepipedal solid block. The block 30 is in the form of a sturdy bar mounted so as to move in the slide 24 in direction Y.

The slide 24 incorporates a toothed bar 46 mounted so as to move accurately through the slide in direction X.

In turn, the bar forming the reference block 30 possesses lateral teeth 48.

The teeth of the toothed bar 46 and the teeth 48 of the block 30, which are perpendicular to each other, are inter¬ connected by gearing incorporated in the slide 24 and serv¬ ing to convert the movements of the toothed bar 46 relative to the slide into corresponding movements of the block 30 in the direction Y.

The gearing 50 comprises a two-pinion unit in which a spin¬ dle 52 rotating in the slide 24 carries an integral larger pinion 54 meshing with the teeth of the toothed bar 46 and a smaller pinion 56 meshing with the teeth 48 of the block 30.

For purposes which will be explained below, the slide 24 incorporates means for the elastic return of the toothed bar 46 to an end-of-travel position of maximum extension (to the left in Figures 6 and 7, in the case of the left- hand slide 24, and to the right in the case of the right- hand slide 24) .

Preferably, as illustrated in Figures 5, 6 and 7, the elas¬ tic return means consist of a spiral spring 58 that inter¬ acts between the slide 24 and the spindle 52 of the two pi¬ nions 54, 56.

For purposes which will be explained below, the slide 24 incorporates selectively controllable means for locking and releasing the toothed bar 46 relative to the slide. The preferred embodiment of these locking and releasing means

will now be described with reference to the Figures 3 to 7.

The locking and releasing means comprise as a fundamental component a brake member 60, preferably in the form of a rocker, as illustrated. The rocker 60 is stressed by elas¬ tic means, in the form of helical compression springs 62, into a locking position, indicated in continuous lines in Figure 4, in which an active surface 64 on the brake member 60 clamps the toothed bar 46 between itself and an opposing surface 66 presented by a bottom wall 68 of the slide 24.

Counter to the force of the springs 62, the brake member 60 can be moved to a releasing position illustrated in chain lines in Figure 4. In this condition the toothed bar 46 is released from the slide 24 and can move relative to the latter in direction X.

A description will now be given of the preferred means for moving the brake member 60 into the releasing position against the force of the springs 62.

Still referring to Figures 3 to 7, for each slide there is mounted on the bladeholder 18 a driving member 70 situated towards the left-hand end of the bladeholder 18 in the case of the left-hand slide 24 and towards the right-hand end of the bladeholder 18 in the case of the right-hand slide 24.

The driving member 70 comprises a lever 72 which is hinged to the bladeholder 18 about an axis 74 extending in the di¬ rection X. The lever 72 carries a series of rollers 76 or equivalent members which are aligned with each other along the direction X.

In its turn the brake member 60 comprises a driven part 78 in the form of a shoe that is elongate in the direction X.

Connected to the lever 72 of the driving member 70 is a pneumatic actuator 80 which serves to pivot the lever 72 between an inactive position, drawn in continuous lines in Figure 4, and an active position, drawn in chain lines in the same figure.

When the slide 24 is towards the left-hand end of the bla¬ deholder 18, if the driving member 70 is in the active po¬ sition, drawn in chain lines in Figure 4, the rollers 76 push on the shoe 78 and move the brake member 60 to the re¬ leased position, also illustrated in chain lines in Figure 4, and hold it there.

The device for setting the reference position of a metal sheet also comprises, for each slide 24, retaining means carried by the bladeholder 18 for immobilizing the toothed bar 46 in a predetermined position relative to the blade¬ holder.

These means preferably take the form of a fixed left-hand stop 82 fixed at the left-hand end of the bladeholder 18, in the case of the left-hand slide 24, and a fixed right- hand stop 82 fixed at the right-hand end of the bladeholder 18, in the case of the right-hand slide 24.

The end of each toothed bar 46 can abut against its corres¬ ponding fixed stop 82.

Referring now to Figures 8a, 8b, 9a, 9b, 10a and 10b, the operation of the device for setting the reference position of the metal sheet will be described, taking the case of the left-hand slide 24.

In Figure 8a the toothed bar 46 has been released from the slide 24 and its elastic biasing means (spring 58) have pu-

shed it to the position of maximum extension towards the left. Its numerical-control motor has moved the slide 24 to a position in which the end of the toothed bar 46 abuts against the corresponding stop 82. In this condition the block 30 is in the position of maximum withdrawal into the slide 24, as illustrated in Figure 8b where its front face F _y is indicated. This being the desired position of adjust¬ ment of the block 30, the wedge member 60 is returned to the locked position 30 and the slide 24 is then traversed (to the right in Figure 8a) integrally with its toothed bar 46 so as to move the block 30 into the desired position of adjustment in direction X.

In Figure 9a, with the toothed bar 46 free to move relative to the slide 24, the latter has been traversed to the left by its numerical-control motor 26, bringing it to a posi¬ tion in which the end of the bar 46 abuts against the stop 82 and is withdrawn relative to the slide 24 in a predeter¬ mined intermediate position. Corresponding to this prede¬ termined position of the bar 46 is an intermediate position of the block 30 in which its front face F _y is at a prede¬ termined distance from the bend line. Once this condition of adjustment has been reached, the wedge member 60 returns to lock the toothed bar 46 relative to the slide 24 and the latter is traversed to the right (Figure 9a) until the block 30 is in the desired position in direction X.

In Figures 10a and 10b a similar situation is illustrated in which the bar 46, free to move through the slide 24, has been moved fully to the right (in Figure 10a) relative to the slide 24 owing to its abutment against the stop 82. In this situation the block 30 has been moved to the predeter¬ mined position of adjustment in which its front face F _y is at its closest point to the bend line.

As will be understood, the adoption of the procedure des¬ cribed with reference to Figures 8a, 8b, 9a, 9b, 10a and 10b means that, with a single motor for each slide 24, a biunivocal correspondence is obtained between, on the one hand, the positions of the slide 24 along its guide means 22, when the toothed bar 46 is immobilised in a predeter¬ mined position and, on the other hand, the position of the reference block 30 relative to the bend line.

The invention has been described above in its application to a so-called "double-acting" bending press, with two ben¬ ding blades and two counterblades operating alternately to produce upward and downward bends in a metal sheet, but it is no less applicable to a bending press fitted with just one bending blade and one counterblade which cooperate with each other.