WO2011141774A1

WO2011141774A1 - Fixing device for a tool to the cursor of a bending-press

Info

Publication number: WO2011141774A1
Application number: PCT/IB2010/052132
Authority: WO
Inventors: Andrea Argentin
Original assignee: Andrea Argentin
Priority date: 2010-05-13
Filing date: 2010-05-13
Publication date: 2011-11-17
Also published as: EP2569107A1

Abstract

There is described a device (10) for fixing a tool (UT), for example a punch, to the cursor of a bending-press, comprising a central body (20) to be connected to the cursor of the bending-press comprising a longitudinal support surface (28) for the tool and a travel end stop (26) for the tool, and a tightening element (24) for the tool that is arranged in front of the central body and is movable relative thereto, and which may be moved from a first release position, wherein it is spaced from the central body for allowing the tool extraction, and a second locking position, wherein it tightens the tool on said surface and presses it against the stop. In order to facilitate and improve the tool tightening there are means (30) for moving the tightening element from the first to the second position, or vice versa with inverted moving motions, through a movement composed of an approaching translation to the central body orthogonal (Y) to said surface and an approaching translation to the abutment parallel (Z) to said surface.

Description

"FIXING DEVICE FOR A TOOL TO THE CURSOR OF A BENDING-PRESS" The present invention relates to a device for fixing a tool to the cursor of a bending- press.

As known, bending-presses are provided with tools (punches) for bending, for example, sheet by pressing it within corresponding fixed bottom dies. For each sheet process there corresponds a special tool, which must be changed each time.

Bending-presses are provided with a cursor, that is, a moving member controlled for carrying out the bending operation, also called tool-holding board, intermediate or piston, and with at least one device that allows fixing the bending tool to the cursor.

Such device serves for removably fixing the tool to the cursor, for allowing the operators to replace it quickly. To this end, the device comprises a central body and a tightening bracket that form a vice structure.

In some models, the bracket directly screws onto the body for locking a tang of the tool in abutment thereon. The major problem of these systems is that in order to replace the tool it is necessary to extract the tang from the vice laterally, sliding it, a particularly delicate and difficult operation for which a free side space is also required. The same applies if an electrical, hydraulic or pneumatic control is used in place of the manual screw-locking.

Other bending-presses are provided with more sophisticated fixing devices, which allow removing the tool from the cursor not laterally anymore, but according to a vertical direction, from top downwards. The inconvenient side extraction is eliminated but there is the problem of preventing the tool from accidentally dropping once the tightening means have been released. In order to obviate this problem, some devices are for example made for cooperating with a punch provided with elastically returning balls, with the task of pushing and maintaining a groove into the punch against a safety tooth in the tightening bracket. There are two drawbacks , to this solution: all the pre-existing punches without balls must be modified and it. is not always easy to overcome the resistant force of the balls to detach the punch.

The main object of the present invention is to improve this prior art.

Another object is to provide a device for fixing a tool to the cursor of a bending-press which allows removing the bending tool, for replacement or maintenance, in a quick and easy manner, with a minimum number of operations and manoeuvres.

Another object is to provide such fixing device that allows a safe replacement, without any risks of accidental dropping of the tool.

Another object is to be able to vertically insert a punch into the device without having to resort to a side extraction.

A further object is to allow aligning the punch on the device without having to resort to squashing or to initial bending tests, which extend the production time and increase scrap.

These and other objects are all achieved by the fixing device according to claim 1, that is, a fixing device for a tool (for example a punch) to the cursor of a bending-press, comprising

a central body to be connected to the cursor of the bending-press comprising

a longitudinal support surface for the tool and a travel-end abutment for the tool (travel end meaning the maximum insertion into the vice structure of the device),

a tightening element for the tool that is arranged in front of the central body and is movable relative thereto, and which may be moved from a first release position, wherein it is spaced from the central body for allowing the tool extraction, and a second locking position, wherein it tightens the tool on said surface and presses it against the abutment, characterised in that it comprises

means for moving the tightening element from the first to the second position, or vice versa with inverted moving motions, through a movement composed of an approaching translation to the central body orthogonal to said surface and an approaching translation to the abutment parallel to said surface.

The particular trajectory followed by the tightening element offers several advantages. In the release position, the tightening element moves away from the central body and leaves the necessary space to easily removing the punch, while when the punch must be locked, the tightening element not only presses it against the central body but also lifts/pulls it to perfectly abut it against the abutment. Easy removal and locking accuracy are obtained at the same time.

Preferably, the means for moving are adapted for moving the tightening element along a circumference arc, keeping it parallel to the surface of the central body. Such solution perfectly integrates said two translations and easily performs them. As preferred version, the means for moving comprise reciprocal articulation means between the tightening element and the central body adapted for imposing the above composite movement. In particular, the articulation means may comprise:

- two stiff articulation elements, for example plates, mounted at the sides of the tightening element and having each two hinging points to the central body and two hinging points to the tightening element, for forming an articulated parallelogram structure; or

- a stiff articulation element, for example substantially C- or bridge- or arch-shaped, comprising a central portion and two portions orthogonal thereto, wherein the two portions have each, at the end, a hinging point to the central body and in the proximity of the central portion, a hinging point to the tightening element. The axes passing through the hinging points on the tightening element and the central body are parallel.

The stiff articulation element may be mounted astride of the tightening element or between this and the central body. The solution with a stiff articulation element is advantageous because a single element allows obtaining the desired movement stiffly guiding the tightening element.

Preferably, the tightening element is mounted for slightly oscillating about the hinging axis relative to the stiff articulation element. This feature may lead to an additional advantage if the central body comprises a groove wherein a projection or tooth of the tightening element may insert in the first position only, thus allowing a rotation of the tightening element about the hinging axis. In this way it is possible to further separate the tightening element from the central body and facilitate the tool removal more. The grove and tooth position may also be exchanged.

Preferably, the device comprises means for imparting a force to the tightening element for moving it between, and locking it at, the first and second position. Such imparting means may comprise a closing element manually screwable into the central body and in engagement on the tightening element, so that by screwing the closing element it pushes the tightening element towards the central body and at the same time it acts as stopping and/or travel-end element adapted for defining (the extremes of) the first and second position. To prevent having the closing element make many turns, which would require time and uncomfortable manoeuvres, it is advantageous to limit its angular stroke while ensuring an excellent tightening. In order to do this, a threaded element with very long pitch would be required, but for example a very large (cumbersome) and easily reversible (poor safety) screw should be mounted. The invention solves the problem with a composite closing element, having a turnable head in sight engaged in a slit of the tightening element and a body that goes through the tightening element up to the central body, where it ends connecting integrally to a large-pitch threaded element (screwable in the central body). For example, a pitch 3 is used, equal to a metric M24 on the diameter. In any case, it is preferred that this pitch is such as to allow the passage from the first to the second position with at most half screwing turn of the turnable head.

The tightening element comprises a longitudinal stopping tooth, which couples to a corresponding groove into the tool and serves for both preventing the accidental drop thereof and for pulling it towards the abutment of the central body. Preferably, such tooth is mounted on elastic means, in order to allow a slight bending thereof useful during the assembly/removal phase for favouring the insertion and the removal of the punch.

Advantageously, the longitudinal tooth is divided into a plurality of minor aligned teeth, each mounted on an independent spring. This allows the device to adjust to different punches, and with different processing tolerances. The spring may be made as a harmonic steel spring divided into as many bending portions as are the teeth of the above plurality. It is preferred to use two equal overlapped springs for improving the elastic return and response.

Preferably, the tightening element is not flat but slightly arched so as to space apart more from the central body. The screwable element is preferably engaged at the centre thereof. The slightly arched shape compensates the deformation generated by the punctual application of the tightening force only at the centre thereof (through the closing element).

These and further advantages shall be better understood from the following description and annexed drawings, provided by way of an example, wherein:

- figure 1 shows a front view of the device of the invention;

- figure 2 shows a cutaway view according to plane II-II; - figure 3 shows a three-dimensional top view of the device in fig. 1 ;

- figure 4 shows a three-dimensional bottom view of the device in fig. 1;

- figure 5 shows a plan view of a leaf spring;

- figure 6 shows a three-dimensional view of a component of the device in fig. 1 ; - figures 7 and 8 show a three-dimensional view of some internal parts of the device in fig. 1.

In the figures, reference numeral 10 globally indicates a device for fixing a tool UT (dashed in Fig. 2) to the cursor of a bending-press. Tool UT is dashed in Fig. 2.

Device 10 comprises a central body 20, a tightening element or bracket 24 and a stiff articulation element 30.

The central body 20 comprises a connecting portion 22 to the press cursor, and a flat portion 25 that has a support surface 28 for the tool and a travel-end abutment surface 26 for tool UT (see fig. 2). In the example, tool UT has a dihedron, two faces at 90° whereof rest on two faces at 90° of portion 25, that is, surfaces 26, 28.

The tightening element 24 in the practice is a compact block with a central opening or slit 80, which is mounted in front of the central body 20 and hinged thereto through the articulation element 30. This is shaped as a C-shaped case or cover and is formed by two side wings 34, 36 and a central portion 38 that surmounts element 24.

The hinging is obtained through pins 40, 42, which hinge the wings 34, 36 respectively to the central body 20 and to the sides of element 24. The overall result is that the articulation element 30 is mounted oscillating on the central body 20 about an axis XI, whereas the tightening element 24 is mounted (slightly) oscillating about an axis X2, parallel to XI.

In slit 80 there is a screwing element 50 (see also fig. 7 and 8) composed of a head 52, exposed outwards for manual screwing, a partially hollow longitudinal body 54 that extends up to the underlying central body 20, and a threaded bushing or portion 56 integrally fixed to body 54 by a screw 58.

Bushing 56 has a sufficiently long pitch as to ensure that - as shall be better explained hereinafter - the tool locking movement requires only a fraction of round angle on the screwing element 50. By screwing/unscrewing the screwing element 50, head 52 moves close or away to/from the central body 20 along an axis Y orthogonal to the central body 20. The top edge of the tightening element 24 comprises a projection or tooth 60 facing the central body 20, which in turn exhibits a groove or concavity 62 wherein such tooth 60 may enter subsequent to an oscillation of the tightening element 24 about axis X2. The bottom edge of groove 62 also has a chamfer 64 for the resting of tooth 60. The bottom edge of the tightening element 24 is provided with a safety tooth 70 projecting towards the central body 20 and adapted for supporting and/or retaining the tool. Tooth 70 consists of an aligned series of secondary teeth 72 that are fixed to a leaf spring 74 made of harmonic steel. Spring 74 (see fig. 5) is divided into flexible lips 76, on each one there being mounted a minor tooth 72. Preferably, spring 74 is actually given by the overlapping of two equal springs, for improving the elastic resistance and limiting the deformations.

Device 10 operates as follows. With the screwing element 50 at the maximum distance away from the central body 20, the tightening element 24 is at the maximum distance away from the central body 20 along axis Y. It is then possible to insert the tool between the tightening element 24 and the flat portion 28. The tool pushes the tightening element 24 upwards, so that tooth 60 sets over groove 62 and, if forced, enters therein. This means that the tightening element 24 may slightly tilt relative to the central body 20, rotating about axis X2 for (slightly) enlarging the entrance of the vice structure and facilitating the mounting of the punch. When the punch is inserted and hooked to tooth 70, its weight lowers the tightening element 24 and moves tooth 60 in abutment on chamfer 64, which forces the tightening element 24 to remain parallel to the central body 20 without clearance. This ensures that the punch remains fastened to the central body 20 even in pre-assembly condition.

In order to lock the punch on the central body 20, the screwing element 50 is screwed so that head 52 pushes the tightening element 24 along axis Y and towards the central body 20. In this way, the tightening element 24, guided by the articulation element 30 that rotates about axis XI, at the same time carries out two movements (see arrow F in fig. 2 and 3):

- one towards the central body 20 along axis Y, and

- one upwards (that is, towards portion 22), perpendicular to axis Y. The direction of this movement is indicated with letter Z in fig. 2.

As a consequence, the tightening element 24 not only presses the tool against surface 28 but with tooth 70 it pulls the tool towards the flat stopping surface 26. The composite movement therefore ensures a perfect contact on surfaces 26, 28, which also leads to high processing accuracy.

Optionally, spring 74 may bend in some of its component teeth 72 in the case of different tolerances in the punch profile that abuts against the stop surface 26. Besides improving the press adaptability to any punch, this solution improves the processing accuracy compensating the mechanical tolerances in the punch.

To remove the tool it is sufficient to rotate the screwing element 50 in the reverse direction to lower the tightening element 24 and move it away from the central body 20. It is noted that the articulation element 30 allows the dual and concurrent movement described above to the tightening element 24 (movement on a circumference arc having as a radius the distance between axes XI and X2), and with its stiffness it ensures the constant parallelism between axes XI and X2.

Claims

1. Device (10) for fixing a tool (UT), for example a punch, to the cursor of a bending-ress, comprising

- a central body (20) to be connected to the cursor of the bending-press comprising a longitudinal support surface (28) for the tool and a travel-end abutment (26) for the tool,

- a tightening element (24) for the tool that is arranged in front of the central body and is movable relative thereto, and which is movable from a first release position, wherein it is spaced from the central body for allowing the tool extraction, and a second locking position, wherein it tightens the tool on said surface and presses it against the abutment, characterised in that it comprises means (30) for moving the tightening element from the first to the second position, or vice versa with inverted moving motions, through a movement composed of an approaching translation to the central body orthogonal (Y) to said surface and an approaching translation to the abutment parallel (Z) to said surface.

2. Device according to claim 1, wherein the means for moving (30) are adapted for moving the tightening element (24) along a circumference arc, keeping it parallel to the support surface (28) of the central body. .

3. Device according to claim 1 or 2, wherein the means for moving (30) comprise reciprocal articulation means (30) between the tightening element and the central body adapted for imposing said composite movement.

4. Device according to claim 3, wherein the articulation means comprise two stiff articulation elements mounted at the sides of the tightening element and having each two hinging points to the central body and two hinging points to the tightening element, for forming an articulated parallelogram structure.

5. Device according to claim 3, wherein the articulation means comprise a stiff articulation element (30), comprising a central portion (38) and two portions orthogonal thereto (34, 36), wherein the two portions (34, 36) have each, at the end, a hinging point to the central body and, in the proximity of the central portion, a hinging point to the tightening element, so that the axes (XI, X2) passing through the hinging points on the tightening element and the central body are parallel.

6. Device according to claim 5, wherein the stiff articulation element (30) is substantially C- or bridge-shaped, and is mounted astride of the tightening element.

7. Device according to claim 5 or 6, wherein the tightening element (24) is mounted for slightly oscillating about the hinging axis (X2) relative to the stiff articulation element (30).

8. Device according to one of the previous claims, comprising means (50) for imparting a force to the tightening element for moving it between, and locking it at, the first and second position.

9. Device according to claim 8, wherein the imparting means comprise a closing element manually screwable into the central body (20) and engaged on the tightening element (24), so that by screwing the closing element it pushes the tightening element towards the central body and at the same time it acts as stopping and travel-end element adapted for defining the first and second position.

10. Device according to claim 9, wherein the closing element is a composite element, having

a turnable head (52) in sight and engaged into a slit (80) of the tightening element (24), and

a body (54) that goes through the tightening element up to the central body where it ends connecting integrally to a threaded element (56) with large pitch which can be screwed into the central body, such pitch being such as to allow the passage from the first to the second position with at most half screwing turn of the turnable head.

11. Device according to one of the previous claims, wherein the tightening element comprises a longitudinal stopping tooth (70) adapted for coupling to a corresponding groove (62) in the tool (UT) and adapted for both preventing the accidental drop of the tool and for pulling it towards the central body abutment (28), said tooth being mounted on elastic means (74) for allowing a slight bending thereof useful during the assembly/removal phase for favouring the punch insertion and removal.

12. Device according to claim 11, wherein said longitudinal tooth (70) is divided into a plurality of minor aligned teeth (72), each mounted on independent spring means.

13. Device according to claim 12, wherein said independent spring means comprise two superimposed harmonic steel springs shaped for having an aligned series of flexible lips.

14. Device according to one of the previous claims, wherein the tightening element is slightly arched, so as to space apart more from the central body.