The present invention relates to a forming apparatus, particularly for forming metal sheets.

Background art

Two punching methods are currently Used for forming relief elements on flat metal sheets.

In one method, punching is performed using individual mating punches and dies, i.e. by performing one punching at a time by punching machines, i.e. with a punch and its die for each relief to be obtained, such as a boss.

It shall be noted that this method is technically known as "forming", because it forms relief elements on a flat sheet of material, typically a fiat metal sheet.

Namely, for such forming process, the punching machines are equipped with dies that are fixed onto a support at a level slightly higher than that of the support and work surface, to allow the relief elements to be formed only at the raised die.

The problem associated with such forming process is that the areas around the location in the sheet designed to be formed with the relief element should not interfere with other dies of the punching machine, otherwise the sheet would be subjected to inelastic buckling, which would cause the generation of abnormal stresses and possible cracks around the formed boss.

A second method was developed to solve this problem of inelastic buckling, in which the die corresponding to the punch to be used for forming is only temporarily lifted by a few millimeters from the support and work surface of the punching machine.

By this arrangement, also the portion of the metal sheet may be held raised from the support and work surface for the time strictly required for forming, while avoiding any interference with other dies of the punching machine close to that being used and hence preventing any inelastic buckling from occurring in the forming area. The above methods still suffer from certain drawbacks.

A first drawback associated with punching machines that do not provide die lifting, in which dies ready for forming are held raised and fixed in this position, is that when these machines have multipunch devices, these are unusable because the dies and punches are very close to each other, typically in a circular path, whereby during forming, the metal sheet should only be clamped between the punch and die designed for forming and not also between the neighboring punches and dies, to avoid the above mentioned inelastic buckling effect.

A drawback associated with punching machines that have the feature of temporary lifting of dies from the support and work surface is that such lifting motion shall be obtained using a special hydraulic actuator, having at least the same force as the cylinder-drop hammer that is used on the punch for forming, for the die to withstand the thrust of the latter for forming, without descending to the level of the support and work surface, which would prevent forming.

This requires very large, expensive hydraulic actuators to be mounted below the forming dies.

Disclosure of the invention

An object of the invention is to provide a forming apparatus that improves the state of the art.

Another object of the invention is to provide a forming apparatus that allows bosses and other relief elements to be formed on sheets of material, such as metal sheets, possibly at the same time as other operating features of the. punching machines, without causing inelastic buckling on the metal sheets.

In one aspect the invention relates to a forming apparatus, as defined in claim 1 , comprising: at least one forming die, which is alternately displaceable by displacing means in a forming direction between a pulled- back hidden position within a reference surface of a forming apparatus and a forming position projecting out of said reference surface, and a forming punch which is designed to be aligned with said at least one die in said forming direction to cooperate therewith for said forming, characterized in that said displacement means comprise a pushing arrangement having a cam profile, which is engageable by contact with said at least one die, to displace it from said pulled-back position to said forming position and vice versa.

Therefore, the invention allows a forming die to temporarily project out of a fixed reference surface of a punching machine to form bosses or other relief elements in metal sheets without causing undesired inelastic buckling therein.

Brief description of the drawings

Further characteristics and advantages of the invention will be more apparent from the detailed description of a few preferred, non-exclusive embodiments of a forming apparatus according to the invention, which are described as non-limiting examples with the help of the annexed drawings, in which:

FIG. 1 is an interrupted schematic side view of a portion of a punching machine having a forming apparatus according to the invention;

FIG. 2 is an enlarged top view of an area of the forming surface of a punching machine having a forming apparatus according to the invention;

FIGS. 3A and 3B are interrupted longitudinal cross sectional views of a forming apparatus of the invention, mounted to a punching machine, in a punching position and a forming position respectively;

FIG. 4 is a longitudinal cross sectional view of the forming apparatus in the position as shown in FIG. 2A;

FIGS. 5A and 5B are the corresponding top views of the positions of

FIGS. 3A and 3B;

FIG. 6 is an enlarged scale view of FIG. 3B;

FIG. 7 is a highly enlarged view of a wedge included in the displacement means of the forming die.

Detailed description of a preferred embodiment

Referring to Figure 1 , there is shown a punching area of a punching machine generally designated by numeral 1. The punching machine 1 is known to include a base 2 and an upper head.

A rotating platform 4 (as shown from the top in Fig. 2), is provided in the base 2, for supporting a plurality of die assemblies 5 to perform punching operations.

Namely, each die assembly 5 comprises a cylindrical tool, typically a container, known in the art as "multi-tool", which in turn contains a plurality of dies that may be selected for punching as needed and as known to those skilled in the art and hence not further described herein.

As shown in Fig. 2, the rotating platform 4 is driven into step-by-step rotation by a motor unit 6 with a drive belt 7, normally of toothed type, connected thereto, and wound about a driving pinion 8, and about the peripheral edge of the platform 4, which has peripheral teeth for this purpose.

Supplementary dies 11 are mounted between each pair of the die assemblies 5 that are circumferentially arranged on the rotating platform 4, for forming relief elements on sheet materials, typically on metal sheets.

As shown in Fig. 2, these supplementary dies 11 are also arranged circumferentially, external to the die assemblies 5 and radially alternated thereto.

Figure 1 shows that the die assemblies 5 define a common reference surface designated as "P" and coinciding with the support and work surface for the workpieces to be punched by the punching machine .

A second rotating platform 4' containing a plurality of punch assemblies, i.e. as many punch assemblies 9 as there are die assemblies 5, in coaxial alignment with the latter, is supported in the head 3 over the base 2.

The punch assemblies 9 also contain a plurality of punches, i.e. as many punches as there are dies, which are selectable for punching.

Supplementary punches 10 are also mounted to the second platform

4', which is rotatably driven by a second motor unit 12, and are designed to cooperate with the supplementary dies 11 for forming, and are designed to be coaxially aligned therewith for this purpose, by rotations.

Referring to Figures 4 to 6, each supplementary die 11 is shown to include an axially hollow cylindrical shaft 12 defining a first end 13 with a housing 15 formed therein for receiving a forming head 16 that has a forming surface 16A.

At the opposite end, the cylindrical shaft 13 defines an opposite end 17 having return means 18.

The cylindrical shaft 13 is coaxially inserted in a cylindrical sliding jacket 19 which is in turn inserted in a hole 19A formed in the rotating platform 4 and fastened thereto by bolt fasteners 20.

Through apertures 21 and 22 are transversely formed both in the cylindrical shaft 13 and in the sliding jacket 9 in coincident positions.

In the punching position, as shown in Fig. 3A and in Fig. 4, the through apertures 21 and 22 are horizontally aligned but slightly offset in the vertical direction, whereas in the forming position as shown both in Fig. 3B and in Fig. 6, they are both horizontally and vertically aligned, and are hence substantially coaxial.

The forming position of the die 11 is obtained by inserting a wedge 23 into the through apertures 21 and 22 in the insertion direction designated by arrow "Z", as shown in Figures 5A and 5B.

Namely, referring to Fig. 7, the wedge 23 is shown to include a body, typically a solid body, whose surface is generally designed with a cam profile 24, i.e. a surface that has such a shape as to form two longitudinal inclined portions 25 and 26, connected to each other by a horizontal portion 27.

During insertion, this profile 24 is designed to push the cylindrical shaft 13 in a forming direction designated by the arrow "F" and in this case in the vertical direction, thereby causing the head 16 to project to a length "d" out of the reference surface "P".

In other words, the wedge 23 forms a point "PN" (see Fig. 5A) which progressively increases its thickness in the longitudinal direction, i.e. from the end 23A facing towards the apertures 21 and 22 to the opposite end 23B facing opposite to it: in Figs. 6 and 7 the respective thicknesses are designated by "S1" and "S2", and "S2" is greater than "S1".

Therefore, progressive insertion of the wedge 23 first through the aperture 22 formed in the sliding jacket 19 and then through the apertures 21 formed in the cylindrical shaft 13 causes progressive and two-step upward lifting of the latter and hence of the forming head 16.

The wedge 23 has a flat surface 28, opposite to the surface 24, which is designed to slide on the lower edges of the apertures 22 and 21 during insertion or withdrawal.

It may be further noted that the apertures 21 have different sizes, namely the aperture 21' facing opposite to the wedge 23 is smaller than the aperture 21", because the aperture 21' is designed to receive the end 23A of the wedge 23 only, which has the smaller thickness "S1", whereas the aperture 21 ", which is substantially identical to the apertures 22, is large, at least as large as the thickness "S2", because it is designed to receive the opposite end 23B of the wedge 23.

Still with reference to Fig. 6, it will be appreciated that, when the wedge 23 is fully inserted in the apertures 22, 21' and 21", it acts as a transverse mechanical lock for the sliding motion of the shaft 13 towards the pulled-back position, thereby effectively opposing the perpendicular force of a punch 10 driven, during forming, by the main punching cylinder of the punching machine.

While the reciprocating sliding motion of the wedge 23 may be obtained in a variety of manners, in this case a linear fluid-dynamic actuator 29 as shown. in Figs. 1 and 2 has been used, namely a hydraulic cylinder; nevertheless, this solution shall be intended without limitation to other solutions known to the skilled persons.

As shown herein, when the wedge 23 is wholly inserted across the apertures 21', 21" and 22, then the cylindrical shaft 13 is fully raised into the forming position of the die 16, as the upper edges of the apertures 21', 21" and 22 lie on their respective flat portions 27 and 24.

As the cylindrical shaft 13 is pushed upwards, it overcomes the return action of two helical springs 30, which are interposed between the cylindrical body 13 and the sliding jacket 19, and have their ends coupled to hooks 31 and 32, transversely associated with the cylindrical shaft 13 and the sliding jacket 19 respectively.

The operation of the invention is as follows: when the punching machine 1 performs normal punching operations on sheet material, such as metal sheets, both the supplementary punches 10 and the supplementary dies 11 are idle.

When relieves or bosses are to be formed on the metal sheet, the latter is placed on the surface "P", so that the point to be formed is aligned between a supplementary forming die 11 and a corresponding supplementary punch 10 coaxially aligned therewith.

The alignment can be obtained both manually and automatically, in the latter case by automatic aligning members mounted on the punching machine, but not shown.

Before use, the selected supplementary die 11 lies, like all the others, in the pulled-back position, i.e. with the forming surface 16A of the forming head 16 retracted flush with the reference surface "P", so that it is ineffective on the metal sheet during normal punching operations.

In this state, the wedge 23 is held in a retracted position, i.e. withdrawn from the apertures 21 and 22.

Whenever a boss or a raised profile is to be formed, the linear actuator 29 is operated to move the wedge 23 in the direction "Z".

The wedge 23 fits into the aperture 22 formed in the cylindrical sliding jacket.29 and then into the aperture 21" with its end 23A.

As the wedge 23 moves further, the end 23A progressively fits into the aperture 21' and the upper edge of the latter first slides against the inclined portion 26, thereby progressively lifting the cylindrical shaft 13.

At the same time as the aperture 21 ', the inclined portion 25 slides in contact with the upper edge of the aperture 21 " thereby pushing it upwards.

Therefore, the two inclined portions 26 and 25 impart a displacement in the forming direction "F" of the cylindrical shaft 13 which causes the forming head 16 to project out of the reference surface "P" of the punching machine 1.

As the wedge 23 slides still further, the two apertures 21' and 21" lie on the horizontal portions 27 and 24 of the cam profile.

In this position, the wedge 23 acts as a mechanical lock member, somewhat as a latch for locking the translational motion of the shaft 13 in the forming direction "F" both towards the forming position and towards the pulled-back position.

Thus, the supplementary die 11 may withstand the axial stress exerted thereon by the supplementary punch 10 selected for forming and driven by the main cylinder of the punching machine.

It should be noted that as the shaft 13 and the punching head 16 are lifted, they also lift the portion of the metal sheet lying on the reference surface "P" of the punching machine 1 in which forming has to be done; therefore, during the forming step, the metal sheet is only clamped between a selected supplementary forming die 11 and a corresponding selected supplementary punch 10, while the other dies of the die assemblies 5 and the other punches of the punch assemblies 9 do not clamp the metal sheet, which prevents the buildup of any undesired stress.

When forming is completed, the wedge 23 is pulled back into the rest position by the linear actuator 29, and fully withdrawn from the apertures 21', 21" and 22.

The cylindrical shaft 13 slides in the sliding jacket 19 to the pulled- back position, and is assisted in such pull-back motion by the pulling action of the springs,.30 that were previously loaded during their motion towards the forming position.

The supplementary punch 10 is also returned in the opposite direction, and the metal sheet in which a relief has been formed is again free of being moved to the reference surface "P" for the next processing step.

The above operating cycle may be repeated until completion of processing as predetermined for each metal sheet. It shall be noted that the wedge 23 has a very small height, like the linear actuator 29 that drives it, which is substantially aligned therewith.

Therefore, very small height, compact machines, may be fabricated, and forming may be performed without mounting powerful actuator units under the shafts 13 to counteract the force of the main cylinder of the punching machine 1 and with no stresses resulting from interferences between the supplementary dies and punches designed for forming and the die assemblies and the punch assemblies designed for ordinary punching.

The above disclosed invention was found to fulfill the intended objects.

The invention is susceptible to a number of changes and variants within the inventive concept.

Furthermore, all the details may be replaced by other technically equivalent parts.

In practice, any materials, shapes and sizes may be used as needed, without departure from the scope of the following claims.