DEVICE FOR LOCKING OF DIES ON PRESS BRAKES

Description

The present invention relates to a device for locking of dies on press brakes.

It is known that press brakes comprise a fixed lower beam on which at least one die is secured, which die has a seat normally defined by a V-shaped notch, and an upper beam to which a punch having a lower working end is linked. The upper beam is vertically movable being driven by suitable hydraulic actuators between a rest position and a work position. In the rest position the upper beam keeps the punch spaced apart from the die, to enable insertion of a sheet metal to be bent. In the work position, the upper beam brings the lower end of the punch partly into the die seat, so as to bend the sheet metal positioned between said two elements. Based on the thickness of the sheet metal to be bent, as well as on the bending angle and the sheet metal material, different punches and dies are mounted on the press brake.

In particular, it is known that for linking the die to the lower beam, plates or locking elements are used that are mounted on opposite sides of the beam and have surfaces for engagement with a die base. One of the locking plates is usually fastened to the beam while the other is pushed or pulled against the die base by means of hydraulic and/or pneumatic actuators. Said die base therefore remains clamped between the two plates, with possible interposition of spacer elements.

The locking plates of the above described type are

complex and expensive, since at the inside of same it is necessary to make the hydraulic ducts bringing the working fluid to the actuators.

In addition, this cost is high because usually employment of several plates sequentially arranged along the lower beam extension is required, so as to clamp the dies mutually aligned on the beam itself.

Furthermore, use of actuators of the hydraulic type has an influence not only on the cost of the whole press brake but also on the brake consumption because it is necessary to supply power to the pumps feeding the actuators .

It is also possible that, after a great number of mounting and dismantling cycles of the dies, overhauling i-s required for plates and actuators because for instance starting of losses in the hydraulic and/or pneumatic circuit may occur.

Also known are locking plates with manual clamping, that are pushed or pulled against the die base exclusively by a plurality of screws which pass through the plate itself and are screwed down in the lower beam. Assembling or disassembling of plates of this type is long and arduous because the worker responsible for the press brake must operate on each screw before being able to mount or remove a die. For this reason plates with manual clamping are usually rather short and each of them is provided with few screws. In order to clamp several dies disposed in side by side relationship several plates with manual clamping are used which are aligned along the extension of the lower beam. However, disadvantageously, between one plate and

the subsequent one there is a slit at which it is not possible to mount a die of reduced sizes because it could not be locked in a sufficiently safe and steady manner.

Accordingly, it is an object of the present invention to provide a device for locking of dies on press brakes enabling the problems of the known art to be solved.

It is a particular aim of the invention to propose a device for locking of dies on press brakes that is simple and cheap.

Another aim of the invention is to propose a device for locking of dies on press brakes enabling the production cost of the press and the servicing costs for same to be maintained within limits.

It is a further aim of the invention to propose a device for locking of dies on press brakes capable of reducing energy consumption as compared with known presses .

A still further aim of the invention is to provide a device at all events enabling quick mounting/dismantling of dies.

Finally, it is an aim of the present invention to propose a device for locking of dies on press brakes that can be installed on already existing presses.

The foregoing and still further aims are substantially achieved by a device for locking of dies on press brakes comprising the features set out in one or more of the appended claims.

Description of a device for locking of dies on press brakes in accordance with the present invention is now given, by way of non-limiting example, with reference to the accompanying drawings, in which: - Fig. 1 is a side view of a device for locking of dies on press brakes according to the present invention;

- Fig. 2 is a front view of an element of the device seen in Fig. 1;

- Fig. 3 is a rear view of the element in Fig. 2; - Fig. 4 shows the device in Fig. 1 with the element seen in Fig. 2 sectioned along line IV-IV;

- Fig. 5 shows the device seen in Fig. 1 with the element in Fig. 3 sectioned along line V-V;

- Fig. 6 shows the element seen in Fig. 2 sectioned along line VI-VI.

With reference to the drawings, a device for locking of dies on press brakes according to the present invention is identified by reference numeral 1.

Device 1 can be installed on a press brake, known by itself and therefore not shown, which comprises a base, a lower ..beam 2 installed on the base, an upper beam mounted above the lower beam 2 and suitable actuators, of the hydraulic type for example, adapted to enable vertical movement of the upper beam close to or away from the lower beam 2. Punches can be installed in a removable manner on the upper beam and dies 3 can be installed on the lower beam 2.

Die 3 comprises a base 4 from which a lug 5 extends, which lug 5 at a distal end thereof has a seat 6 adapted to bend a sheet metal, in co-operation with a punch. Seat 6 is preferably defined by a V-shaped notch. In the attached drawings, only the cross-section

of die 3 is shown, which die can extend along the lower beam 2 over the whole length of same or over portions of said beam. In this case, several dies 3 can be disposed in mutual side by side relationship along the extension of the lower beam 2.

The lower beam 2 has an upper surface 7 adapted to receive, in a rest condition, a lower surface 8 of base 4 of die 3. The lower beam 2 further has a first clamping surface 9 transversely extending from the rest surface 7 and, preferably, forming a right angle with said rest surface 7.

Preferably, this first clamping surface 9 is not of one piece construction with the lower beam 2 but it belongs to an auxiliary plate 10 fastened to the lower beam 2 in a detachable manner, by means of screws, not shown, for example.

Said auxiliary plate 10 can extend over the whole length -of the lower beam 2 or only over a portion of same. As shown, the auxiliary plate 10 has a face 11 partly coupled to a first side face 12 of the lower beam 2. In particular, face 11 of the auxiliary plate 10 projects beyond the rest surface 7 and defines the first clamping surface 9.

Device 1 further comprises a clamping plate 13 to be linked to the lower beam 2 on the side opposite to the first clamping surface 9 relative to the rest surface 7. The clamping plate 13 has a second clamping surface 14 facing the first clamping surface 9 and spaced apart therefrom, so as to delimit a seat for die 3.

In more detail, the first and second clamping surfaces

9, 14 together with the rest surface 7 delimit the seat receiving base 4 of die 3.

Possibly, spacers could be interposed between the base 4 of die 3 and the first and second clamping surfaces 9, 14, if the width of said base 4 were smaller than the width of the lower beam 2.

Said clamping plate 13 too can extend over the whole length of the lower beam 2 or only over a portion of same .

Locking means is used for clamping die 3 between the first and second clamping surfaces 9, 14. In particular, opposite faces 15, 16 of base 4 of die 3 are sandwiched between the first and second clamping surfaces 9, 14.

Preferably, the locking means pushes the second clamping surface 14 against the base 4 and the latter against the auxiliary plate 10. This thrust generates friction forces on the opposite surfaces 15, 16 of base 4 of such a nature that they alone are able to prevent any movement of die 3 both along the longitudinal extension of the lower beam 2 and in a direction orthogonal to the rest surface 7 (vertical direction) . In fact, the first and second clamping surfaces 9, 14 are substantially smooth and do not have any projecting part engaged in recesses formed on the die.

The second clamping surface 14 too, when it is closed on die 3, extends transversely from the rest surface 7 and preferably forms a right angle with said rest surface 7.

The locking means comprises at least one pin 17 fastened to the lower beam 2 and extending along a direction "Y" substantially transverse to the longitudinal extension of the lower beam 2 itself (Fig. 4) .

Pin 17 is inserted with a predetermined clearance into a respective hole 18 formed in the clamping plate 13, so that the clamping plate 13 is free to oscillate in a plane transverse to the longitudinal extension of the lower beam 2 (Fig. 4) .

As can be viewed, device 1 comprises a plurality of pins 17 inserted into respective holes 18 formed in the clamping plate 13 and disposed along the longitudinal extension "X" of the clamping plate 13 itself (Fig. 2).

In particular, pins 17 are screws provided with heads

19 and screwed down in the lower beam 2 with their axes "Y" substantially perpendicular to a second side face

20 of said lower beam 2.

Holes 18 pass through the thickness of the clamping plate 13 and have axes substantially perpendicular to the clamping surface 14. Said hole/holes further has/have portions of different diameters so as to form an annular abutment 21 interfering with head 19, in order to retain the clamping plate 13. The portion of greater diameter houses head 19 of screw 17 and the portion of smaller diameter houses the shank.

The diameter of holes 18 is slightly greater than that of screws 17 (both at the shank and at the head) and the annular abutment 21 of screws 17 is not pushed against the clamping plate 13. Therefore, the clamping

plate 13 is free to slightly oscillate around an ideal axis "Z" (shown in Fig. 4) passing through the screws 17, also in a plane substantially perpendicular to its longitudinal extension "X" .

Spring means 22 is interposed between the clamping plate 13 and lower beam 2 and is located at an end 23 of the clamping plate 13 opposite to the second clamping surface 14 relative to pin 17. The spring means 22 pushes this end 23 away from the lower beam 2 (arrow A in Fig. 5) and, through rotation of the clamping plate 13 around the ideal axis "Z", pushes the second clamping surface 14 towards the first clamping surface 9 and towards die 3 (arrow B in Fig. 5) .

Preferably, the spring means 22 comprises at least one spring 24 having a first end 24a in abutment against the clamping plate 13 and a second end 24b in abutment against the lower beam 2. Spring 24 works in compression and therefore exerts pressure against both the clamping plate 13 and the lower beam 2.

In the preferred embodiment herein shown, spring 24 is of the helical type and is substantially contained in a housing 25 formed in the clamping plate 13. In particular, the clamping plate 13 has a plurality of housings 25 arranged along its longitudinal extension

(Fig. 3). Housings 25 are blind holes opening onto a face 26 of the clamping plate 13 facing beam 2. The second end 24b of spring 24 projects from face 26 of the clamping plate 13 to abut against the second side face 20.of the lower beam 2 (Fig. 5) .

A protrusion 27 is present on face 26 of the clamping plate 13 and it carries the second clamping surface 14

which extends along an upper edge of the plate 13 itself. Therefore, while springs 24 push the second clamping surface 14 against die 3, the remaining surface 26 keeps slightly spaced apart from the lower beam 2 (Fig. 5) .

An insert 28 is introduced into protrusion 27 and defines part of the second clamping surface 14. This insert 28 is made of a softer material than that of die 3 and is preferably made of plastic material. The insert allows damage of die 3 to be avoided and ensures coupling thereto with high friction. In addition, this insert adapts itself to possible unevennesses of the die surface. Insert 28, as shown in Fig. 3, preferably extends along the whole length of the clamping plate 13.

To remove die 3 from the lower beam 2 and install another die, device 1 further comprises means 29 capable of moving the second clamping surface 14 away from die 3 against the action of the spring means 22, i.e. causing rotation of plate 13 around the ideal axis "Z" .

Preferably this means 29 comprises at least one dowel 30 (Fig. 6) inserted in a threaded through hole formed in the clamping plate 13 and located close to the second clamping surface 14. Dowel 30 has a first end 32 suitable for abutment against the lower beam 2 and a second end 33 operable by means of a tool or provided with a lever for example (not shown) , adapted to rotate dowel 30. Preferably a single dowel 30 is present and it is inserted in a hole 31 formed at an intermediate point of the clamping plate 13.

By screwing dowel 30 in hole 31, the first end 32 is brought to project beyond face 26 of plate 13, so as to move this second clamping surface 14 away from base 4 of die 3. After this operation, die 3 can be slipped off upwards or it is removed by causing its sliding along the beam, and then replaced.

A new die 3 is introduced between the first and second clamping surfaces 9, 14 (from top or causing sliding of same along the lower beam) and dowel 30 is unscrewed so that the first end 32 is retracted and the second clamping surface 14 is brought back against base 4 of the new die 3.

The present invention reaches the intended purposes and achieves important advantages.

The device of the invention is of simple and cheap structure. In fact, it is an exclusively mechanical device, surely simpler and cheaper than known hydraulic and/or pneumatic devices. As a result, maintenance costs are reduced too.

In addition, it is possible to apply this device substantially to any press without modifying it.

By virtue of the insert of plastic material and the even distribution of the clamping springs, the device ensures excellent clamping also of 10, 15 and 20 mm long pieces that, as known, cannot be forcibly clamped by traditional systems.

Unlike some known systems, it is possible to cause insertion of the die on the lower beam either vertically or by making it slide horizontally.

In addition, clamping plates of important length (typically 835 mm) can be made, because in any case with a single movement (a rotation of a 3/4 revolution of the fastening dowel at most) it is possible to lock/unlock the die itself. On the contrary, in traditional hand systems, it may happen that eight screws are to be loosened or tightened, the die length being the same.