EP0062562B1 - Method and device for the automatic control of the press rams by means of cylinders with self blocking piston rods - Google Patents

Abstract

Process and device for the automatic regulation of the push rods of a press by means of a self-locking rod jack. The device comprises a table, a matrix, a blank holder, a main slide, a punch and a blank holder slide. Each of the push rods comprises a jack rod mounted on the blank holder slide. The jack is equipped with an automatically lockable and unlockable device for regulating the length by sensing. At their lower end, in each case the rods have means for the high-speed locking to the blank holder.

Description

The present invention relates to an automatic adjustment device for the pushers of a stamping press. It also relates to a method of using this device.

Hydraulic stamping presses are used to stamp hollow parts from metal blanks. A press consists of a frame, a table on which the die is fixed, a main slide which moves in translation relative to the table along slides. This slide carries a punch .complementary to that of the imprint of the matrix. Forming without removing metal is carried out in a tool that is not part of the machine. The closing, working, and opening movement of the tooling at the required forming pressure takes place via a hydraulic cylinder.

A blank holder arranged between the table and the main slide has the function of keeping the sheet blank tight against the die during the stamping operation. This blank holder also moves in translation relative to the table, in order to allow the press to be fed with stamped parts and the evacuation of stamped parts.

The necessary clamping force exerted on the blank holder by a blank press slide located above the main slide is transmitted by pushers. These pushers are in the form of elongated rods passing through the main slide and supported at their upper end under the hold-down slide and at their lower end on the hold-down itself. Cross rods are placed in the pushers to prevent them from falling during the ascent of the main slide during the adjustment phases. The upward return of the backgrounds is provided by the main slide by means of tie rods passing through the latter. These are screwed at their lower end to the clamp and are supported by a shoulder of their upper end on the main slide.

We know (US-A 2 350 884) a press of this type. The four backgrounds are directly actuated by conventional hydraulic cylinders. The body of each cylinder is integral with the frame and the rod of each cylinder crosses the main slide to come to exert a pressing force on the blank holder. These hydraulic cylinders are locked in the desired position by maintaining or releasing the supply pressure.

With a press of this type, it is necessary to adjust the pushers before any drawing operation of a new series of parts.

However, the duration of the adjustment operations is significant, of the order of two hours, which leads to the immobilization of very expensive machines, and to an increase in production costs. In addition, these are tedious operations for the operator because of the number and weight of the pushers to handle.

We therefore understand the advantage of reducing the duration of the push button adjustment operation. It is precisely to this problem that the invention provides a solution. It relates to an automatic adjustment device for the pushers of a stamping press which eliminates their handling, mounting and adjustment.

To this end, the pushers of the prior art are replaced by jacks fitted with an automatic locking and unlocking system of the rod, in accordance with the characteristics defined in the characterizing part of claim 1.

The advantage of the invention resides in the fact that, thanks to the presence of a hold-down slide and of hydraulic jacks arranged between this slide and the hold-down itself, the length of the rods can be adjusted quickly. .

The invention also relates to a method for automatically adjusting the pushers of a stamping press: according to claim 4. Thanks to this method, it is no longer necessary to disassemble, reassemble and adjust the pushers at each change of tooling. . It suffices to lock in the high position the push rods which are not used with a specific blank press. Thanks to a programmable automaton, the selection of the pushers to be used and the display of the stamping parameters can be easily automated.

• - on descend le coulisseau de serre-flan en butée sur le coulisseau emboutisseur,
• - on débloque les tiges des vérins et on les descend jusqu'à ce qu'elles soient en butée contre le serre-flan,
• - on commande automatiquement le blocage des tiges à partir d'un signal détectant l'augmentation de pression hydraulique dans les vérins,
• - on bloque les extrémités des tiges sur le serre-flan.

More precisely, this process is characterized in that, the tools having been mounted on the table:

• - the blank holder slide is lowered into abutment on the stamping slide,
• - the rods of the cylinders are released and lowered until they are in abutment against the blank holder,
• - the rods are locked automatically from a signal detecting the increase in hydraulic pressure in the cylinders,
• - the ends of the rods are blocked on the blank holder.

• - la figure 1 représente une presse hydraulique à emboutir de l'art antérieur,
• - la figure 2 représente une presse à emboutir conforme à l'invention,
• - la figure 3 montre le détail de la presse représentée sur la figure 2.

The characteristics of the invention will emerge from the description which follows, given by way of illustration and in no way limiting, with reference to the appended drawings, in which:

• FIG. 1 represents a hydraulic stamping press of the prior art,
• FIG. 2 represents a stamping press according to the invention,
• - Figure 3 shows the detail of the press shown in Figure 2.

There is shown in Figure 1 a stamping press according to the prior art of this type. This press consists of a frame 2, a table 4, a main slide 6 and a hold-down slide 8. The main slide is controlled by the main cylinder 10. The hold-down slide 8 is ordered by at least two cylinders 12 with plunger. The matrix 14 is clamped on the table 4.

In the left half-view of FIG. 1, the main slide 6 and the blank holder slide 8 are shown in the high position. On the right half-view, the main slide and the blank holding slide have been lowered until contact with the tools.

A press of this type is called a "double-acting press" because it has two different slides actuated by two separate jack systems. A triple-acting stamping press has the same elements that perform the same functions. There is only added an upward movement located under the table 4. The punch 16 is fixed to the main slide 6, also called stamping slide. The sheet blank to be stamped 18 is placed on the die 14. The blank holder 20 has the function of clamping the sheet blank 18 during the stamping operation, it is controlled by means of pushers 22 interposed between it -same and the blank holder slide. The two jacks 12 bring the slide 8 into abutment against the main slide 6. The force transmitted by the pushers 22 to the blank holder 20 therefore depends on the adjustment of the length of these pushers. This adjustment is made using shims and requires great precision.

Furthermore, particular pushers, which will be called tie rods 22a, in the following text, are slidably mounted in bores made in the main slide 6 and are screwed at their lower end into the blank holder 20 while their upper end carries a shoulder which prevents them from crossing the main slide 6. These tie rods ensure the raising of the blank holder by raising the slide 6.

When changing the tooling of the press, that is to say the die 14 and the punch 16 to stamp a series of different parts, it is necessary to adjust again the length of the pushers 22. The change of buttons are carried out as follows. First of all, the stamping slide 6 is lowered onto the table 4 (see FIG. 1, half-view on the right); the pushers 22 are introduced inside the orifices 7 provided for this purpose in the slide. The push rod retaining rods 22 are introduced at their upper part. We go up the main slide 6 and we introduce the tooling of the press on the table 4. This tooling is composed as it was said previously, of a die 14, a punch 16 and a blank holder 20 The main slide 6 is lowered in contact with the tool. This main slide is then in the position it will occupy during normal press operation at the end of the stamping operation, to the thickness of the blank. The punch is flanged on the underside of the main slide and the die on the table 4. It remains to make a setting between the upper end of the pushers 22 and the underside of the hold-down slide 8 to make up for the play of wear. The stamping slide 6 and the blank holder slide 8 are then reassembled via the tie rods 22a. The press is then ready to work.

The assembly and adjustment operations of the pushers which have just been described are very long, of the order of two hours.

FIG. 2 shows a stamping press according to the invention, which makes it possible to considerably reduce the duration of the operations for adjusting the pushers. The general construction of this press is similar to that of FIG. 1. It comprises a frame 2, a table 4, a stamping slide 6 and a blank clamp slide 8. The tool, that is to say the die 14, the punch 16, and the blank holder 20 is identical.

According to the invention, the pushers which transmit the clamping force of the blank holder slide 8 to the blank holder 20, designated by the reference 22 in FIG. 1, here consist of the rods 24 of the jacks 26 mounted vertically on the blank holder slide 8. Around each of the rods 24 of these jacks, there is an automatic locking and unlocking device 28. At its lower end 24a, the rod 24 has a quick locking system, on the greenhouse - blank. This system can be automatic.

The means for locking and unlocking the rod 24 of the jack 26 are shown on an enlarged scale in FIG. 3. They are preferably constituted by a bush 30 which surrounds the rod 24; by means of the sleeve 30, it is possible to tighten and loosen the rod 24 in such a way that the friction forces lock it in its position. The blocking of the rod 24 is effected when a hydraulic pressure is exerted outside the sleeve 30. The unblocking is then effected by lack of pressure. Preferably, a reverse locking system is used in which the sleeve 30 has an internal bore whose diameter is less than that of the rod 24. This gives a friction connection due to the elastic deformation of the materials present. The unblocking ^> cage is obtained by a hydraulic pressure applied uniformly inside the sleeve 30 between the two contact surfaces. The “auto-lock” system, manufactured and marketed by the Quiri Company is an automatic locking system which can be used with satisfaction in a press of the invention.

• En partant de la presse en position de repos, c'est-à-dire le coulisseau emboutisseur 6 et le coulisseau de serre-flan 8 étant en position remontée, on monte et on centre l'oùtillage sur la table 4. Afin de raccourcir la durée de cette opération, on utilise un dispositif hydraulique de bridage rapide.

The tooling change and the adjustment of the pushers by means of the device of the invention is carried out as follows:

• Starting from the press in the rest position, that is to say the stamping slide 6 and the blank holder slide 8 in the raised position, the tool is mounted and centered on the table 4. In order to shorten for the duration of this operation, a hydraulic fast clamping device is used.

We descend the stamping slide. The punch 16 is flanged on the underside of this slide. As with the die, this clamping can be carried out by means of a hydraulic fast clamping device. We define the travel of the blank holder slide 8 by stopping the main slide at top dead center in a position chosen according to the tooling. This position depends in particular on the thickness of the blank to be stamped.

We descend the blank holder slide 8 in abutment on the main slide. Indeed, as we can see in Figures 2 and 3, the blank holder slide 8 has, at its lower part, stops 32 intended to provide a clearance between the lower part of the blocking and unblocking device 28 and the upper face of the stamping slide 6. The slide 8 being in abutment, the rods of the jacks 24 are released and they are brought down into abutment on the clamp blank 20. This blank holder comprises a rapid locking and unlocking device 33 of the end 24a. According to a variant, this locking 33 can be carried out automatically. Once the end 24a abuts against the blank holder 20, the hydraulic pressure inside the jack 26 increases rapidly, since the volume available for the fluid no longer increases. The detection of this increase in pressure makes it possible to develop a signal which on the one hand interrupts the low pressure hydraulic supply to the jack 26 and on the other hand blocks the rod 24 by means of the device 28.

In a preferred embodiment of the invention, the blocking of the rod 24 is obtained by means of a cancellation of the hydraulic pressure exerted inside the bush 30. This pressure cancellation simultaneously in the bush and in the actuator is controlled by a pressure switch, when the actuator supply pressure reaches a predetermined threshold, lower than the regulating pressure of the entire press.

Thus, in the event of a hydraulic supply failure of the device, the retention of the rod 24 being ensured by the friction in the sleeve 30, any danger of untimely operation is avoided.

The stamping slide 6 and the blank holder slide 8 are then raised to the high position. The press is then ready to work.

The adjustment of the press pushers as just described makes it possible to reduce the tool setting time to around 5 minutes. It therefore allows more frequent tooling changes and consequently leads to the elimination of the downtime of the press, when waiting for stamping interfaces dedicated to heat treatments.

Furthermore, the definition of the stroke of the pushers by probing allows automatic adjustment of the wear clearances at each adjustment.

In addition, all manipulations of the pushers and their storage are eliminated. Indeed, when changing the tooling of the press, it is not necessary to disassemble the pushers which are not used. FIG. 3 shows two different tools: on the one hand a matrix 14 and a blank holder 20, and on the other hand a matrix 14 'and a blank holder 20'. When using the die 14 and the blank holder 20 a number of pushers, for example the pushbutton 24 'are not used. It then suffices to reassemble it in the high position, as shown in FIG. 3, and to block it in this position by means of the device 28 for automatic locking and unlocking. In the example shown, this blocking is effected by lack of pressure. Thanks to a programmable automaton, the selection of the pushers to be used and the display of the stamping parameters are automatic.

Claims (5)

1. Stamping press which comprises, in known manner, a table (4) to which is fastened a matrix (14), a draw ring (20) located above the table (4), a main slider (6) vertically-displaceable with respect to the table (4) and to which is fastened a punch (16), a draw ring slider (8), at least one draw ring jack (12) for vertically moving the draw ring slider (8) with respect to the table (4), rams fixed at one end to the draw ring (20) and at the other end to the draw ring slider (8), said rams being adapted to transmit the force of the slider (8) to the draw ring (20), characterized in that each ram comprises the rod (24) of a jack (26) mounted on the draw ring slider (8), said jack (26) having an automatically blockable and releasable gripping device (28) for controlling its extension, the means for blocking and releasing the rod (24) of the jack (26) comprising a bushing (30) mounted around said rod and fixed to the cylinder of the jack (26), blocking and releasing of the rod (24) being controlled by hydraulic pressure means, the lower ends (24a) of the rods (24) comprising means for rapid locking to the draw ring (20).

2. Press according to Claim 1, characterized in that blocking of the rod (24) is produced by means of hydraulic pressure acting on the exterior of the bushing (30).

3. Press according to Claim 1, characterized in that the bushing (30) has an internal bore of smaller diameter than the rod (24), frictional blocking of the latter resulting from elastic deformation of the material, release resulting from hydraulic pressure uniformly applied between the two contacting surfaces.

4. Process for controlling the draw ring rams of a press comprising a table (4) to which is fastened a matrix (14), a draw ring (20) located above the table (4), a main slider (6) vertically-displaceable with respect to the table (4) and to which is fastened a punch (16), a draw ring slider (8), at least one draw ring jack (12) for vertically moving the draw ring slider (8) with respect to the table

(4), rams fixed at one end to the draw ring (20) and at the other end to the draw ring slider (8), said rams being adapted to transmit the force of the slider (8) to the draw ring (20), each ram comprising the rod (24) of a jack (26) mounted on the draw ring slider (8), said jack (26) having an automatically blockable and releasable gripping device (28) for controlling its extension, the means for blocking and releasing the rod (24) of the jack (26) comprising a bushing (30) mounted said rod and fixed to the cylinder of the jack (26), blocking and releasing of the rod (24) being controlled by hydraulic pressure means, the lower ends (24a) of the rods (24) comprising means for rapid locking to the draw ring (20), characterized in that, after lifting the movable components :

- the draw ring slider (8) is lowered until it abuts the press slider (6) ;

- the rods (24) of the jacks (26) are released and they are lowered until they abut against the draw ring (20) ;

- blocking of the rod (24) is automatically commanded by a signal generated by increase of hydraulic pressure in the jacks (26) ; and

- the ends (24a) of the rods (24) are locked on the draw ring (20).

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