Machine for the production of metal sheet panels with bent edges

Abstract: Machine for the production of metal sheet panels with bent edges, comprising a work surface (1) for a sheet to be machined, a bending press (2) provided with a bending die and located frontally to the work plane, a mechanical hand (4) mobile as regards the work plane for the displacement of the sheet (5) during machining, characterised in that the work plane is substantially enclosed inside a protection structure (6), said protection structure comprising at least one access opening (7) to the work plane for the feeding to and the removal of the sheet from the work surface on behalf of a human operator, and in that said at least one access opening (7) is associated to respective means (8) for the interdiction of the access to the work plane during machining.

Description: The present invention refers to a machine for the production of metal sheet panels with bent edges, commonly referred to as panel machine. In particular the invention refers to a panel machine equipped with a single bending die to obtain metal sheets of generically rectangular shape having edges that are bent one or more times at one or more of their four sides, for example of the kind described in the Italian patent N. 1086365. Panels of this type have a wide utilisation for example in the manufacture of metal cabinets, refrigerators, washing machines, air conditioners, shelving in general etc. The known panel machines comprise a work plane where to lay the metal sheet (panel) to be machined, a bending press provided with a bending die and located frontally to the work plane, a mechanical hand mobile with respect to the work plane to move the sheet to be machined during machining, an automatic sheet feeder located laterally to the work plane and comprising a carriage for the conveyance of the sheet from the feeder to the work plane and for the removal of the bent sheet from the work plane once the machining has been completed. The conveyor carriage takes the sheet from the feeder and locates it on the work plane; the mechanical hand takes the sheet substantially at its centre and it moves it in such a way so as to position in turn each side to be bent in correspondence of the bending press. Once the machining is completed, the mechanical hand drops the sheet, and the carriage removes it from the work plane. Therefore, all the operations of the panel machine, in particular the feeding of the sheet to be machined and the removal of the machined sheet, are automated. Because of the presence of the feeder and of the carriage, the machining zone (that is the work plane) is substantially accessible from the outside during machining, in order not to hinder the operations of the same carriage. In order to meet the safety requirements imposed by the current regulations, light scan devices (laser scanner or photocells) are provided which stop the panel machine any time a human operator, or in any case a not identified body, gets near the machining zone. Such panel machines, although they are very efficient, are rather complex to realise and as a consequence they are costly due exactly to the high degree of automation. JP-A-04 046 644 discloses a sheet panel bending machine having a work plane. US-A-4 863 320 discloses a machine tool wherein the work plane is enclosed inside a protection structure comprising means for the interdiction of the access to the work plane during machining. In view of the state of the art described, object of the present invention is to provide for a less complex and as a consequence less costly panel machine and that would anyhow meet the safety requirement imposed by the current regulations. According to the present invention, such object is obtained by means of a panel machine as defined is claim 1. According to a preferred form of embodiment, said interdiction means consist of a door mounted on the protection structure in correspondence of the access opening or openings, selectively openable by the human operator for the feeding and removal of the sheet and closable during the machining of the same sheet. The door or doors form physical barriers preventing the access to the work plane when the machine is operating. As an alternative, said interdiction means can consist in light scan devices as photocells or laser scanners, serving the purpose to interrupt the operation of the machine any time that, during machining, a non-recognisable body tries to accede to the work plane through the access door or doors. The panel machine according to the invention is clearly less complex than the known panel machines, since neither automatic feeder nor carriage to convey sheets are provided. As a result of this, not only the panel machine is less costly, but it is also possible to enclose the work plane inside a protection structure (physical), consisting for example of a barrier made of sheets preferably provided with windows, that would completely isolate the machining zone for the metal sheets from the outside during the same machining. The feeding and removal of sheets from the work plane is carried out through the access opening or openings provided in the protection structure by means of a human operator. The presence of said interdiction devices in correspondence of the access opening or openings guarantees the safety of the operator. The characteristics and advantages of the present invention will be rendered more evident by the following detailed description of a possible embodiment thereof, illustrated as a non-limiting example in the enclosed drawings, in which: Figure 1 shows in a schematic axonometric view a panel machine according to the present invention, surrounded by a protection structure; Figure 2 is analogous to Figure 1, but with the protection structure partially removed; Figure 3 shows in a magnified scale the detail of a door to close an access opening of the protection structure of the panel machine of Figure 1; Figure 4 is a section along a vertical median plane of the panel machine of Figure 1; Figure 5 shows in detail an element for the centring of a sheet on the work plane, with the respective mechanism of movement. With reference to the drawings, in Figure 1 and 2 a panel machine according to the present invention is shown. The panel machine comprises a work plane 1 for a sheet to be machined 5, a bending press 2 provided with a bending die (that will be described in detail later) positioned frontally to the work plane 1, a mechanical hand 4 mobile as regards the work plane 1 for the movement of the sheet 5 during machining, and a protection structure 6, consisting of sheets preferably provided with windows, that encloses the work plane 1 with the mechanical hand 4, and the bending press 2. In this example, inside the protection structure 6 two openings 7 for the access to the machining zone are provided on opposite sides of the work plane, that allow a human operator to introduce a sheet to be machined 5 on the work plane 1 and to remove the sheet once the machining is completed. In the example shown, the access openings are associated with respective doors 8, that can be seen in a magnified scale in Figure 3, hinged to a supporting frame (not shown for clearness reasons) in the protection structure 6 in such a way so as to result to be turnable around respective horizontal axes. Preferably, in order to facilitate the opening and closing of the doors 8, conventional gas cylinders (not shown) can be provided. In the example shown, the protection structure 6 comprises two openings for the access to the work plane, so that the latter turns out to be accessible from either sides; however, it could also be possible to provide for a single access opening. More details about the structure of the bending press 2 and the mechanical hand 4, and the relative way of operating, are shown in Figures 4 and 5, that will now be described, in which for clearness reasons the protection structure 6 is not shown. In a known way, the mechanical hand 4 comprises a carriage globally indicated by 9, conformed as an "arch press" mobile as regards the work plane 1 through a longitudinal slit 3 of the same on rectilinear horizontal guides 10 supported by a bed 11 which rests on the floor, said guides 10 extending perpendicular to the front of the bending press 2. A fluid mechanical cylinder 50 causes the movement of the carriage 9 along the guides 10 in the direction toward or away from the bending press 2. The carriage 9 supports a hydraulic vice 12 with overlaid and coaxial lower and upper jaws 13, 14 having flat and horizontal opposite walls suitable to clamp between them the sheet to be machined, as shown in Figure 4. The lower jaw 13 is fixedly mounted on the upper end of a horizontal shaft 15 set into rotation by a rotator 16 mounted on the lower part of the carriage 9 and capable to confer the shaft 15 and the lower jaw 13 angular shift by 90° and 180° in one and in the opposite direction. The upper jaw 14 is fixedly mounted to the lower end of a vertical shaft 17 turningly held in idle mode by a bracket arm 51 held in turn in a slidingly vertical way by the end of the upper part of the carriage 9. A fluid mechanical cylinder, not shown, causes the lowering and lifting of the bracket arm 51, and therefore of the jaw 14, in such a way as to respectively clamp the sheet to be machined 5 between the jaws 13, 14 or to release the same sheet. The shaft 17 must idle in rotation around its own axis, in order not to prevent the rotation of the sheet 5 by means of the rotator 16, the jaw 14 having to co-operate with the jaw 13 in order to clamp the sheet 5. In addition, the mechanical hand 4 comprises a thrust means 19, that can also be seen in Figure 2 and shown in Figure 4 into two different operating positions, globally mobile with the carriage 9 and also independently set in motion by a respective fluid mechanical cylinder 52 and sliding in a slide created in the lower part of the carriage 9. When the thrust means 19 is in the position of rest, it is substantially in correspondence of the throat of the arch press 9; by moving forward along the slide toward the bending press 2 under the action of the cylinder 52, the thrust means 19 abuts against the back edge of the sheet to be machined in such a way as to push the sheet 5 and to allow its automatic correct positioning, as it will be described more in detail later. The bending press 2 comprises a bearing structure having a substantially "C" shaped section and comprising a lower wing 21 and an upper wing 22. The lower wing 21 rests on the floor, while the upper wing 22 is hinged to the lower wing 21 in correspondence of flanges 23 located on the back of the latter, in such a way so as to result turnable around a horizontal axis indicated by A. A cylinder-piston unit 24 produces the rotation of the upper wing 2 around the axis A, being provided at least one vertical rod 25 (schematically indicated by dots and lines) which acts as a guide to the movement of the upper wing 22. Frontally to the lower wing 21 a vertical support 26 is fixed having a free flat and horizontal upper surface located at the same level of the work plane 1, that forms a lower blank holder. Frontally to the upper wing 22 an upper blank holder 27 is fixed in such a way so as to extend vertically toward the bottom, that is provided with a free flat lower surface suitable to co-operate with the upper surface of the lower blank holder in order to clamp the sheet to be machined near the edge of the same to be bent. In the space comprised between the upper and lower wings 22, 21 a bending blade holder 28 is housed, having a substantially "C" shape, in cross section. The blade holder 28 comprises a lower arm 29 and an upper arm 30 which extend toward the front of the bending press 2. A lower bending blade 34 is fixed at the end of the lower arm 29, while an upper bending blade 35 is fixed to the upper arm 30. On the back, the blade holder 28 is hinged to a torsion bar 31 in such a way so as to result as being turning around the axis indicated by C. The torsion bar 31 is also turnable around the horizontal axis indicated by B under the action of a fluid mechanical cylinder, of which only the rod 32 is schematically shown in dots and lines. A fluid mechanical cylinder (whose rod 33 is schematically shown in dots and lines) produces the rotation of the blade holder 28 around the axis C. The combination of the rotation of the torsion bar 31 around its own axis B, which determines the position of the axis of rotation C of the blade holder 28, and the rotation of the blade holder 28 around the axis C allows a great variety of movements to the bending blades 34, 35 in order to obtain bends with various angles both upward and downward. Frontally to the support 26 a known reference-bearing block 36 is mounted, that has a flat horizontal upper surface 37 at the same level of the work plane 1 and inside of which reference elements 38 visible also in Figures 1 and 2 are located. The block 36 is movable in a direction perpendicular to the front of the bending press 2, so that it can move away from or toward the same. In addition, the reference elements 38, normally retractable inside the block 36 during the machining of the sheet, can project in such a way so as to jut out from the surface 37. The reference elements 38 can also move in a direction parallel to the front of the bending press, in such a way that they can mutually move toward or away from each other. As shown in Figure 5, each reference element 38 (shown by a continuous line in a position of rest, retracted and by dots and lines in the operating position, projecting) is turningly supported by a respective carriage 61 mounted on an endless screw 39, extending parallel to the front of the bending press 2 and mortised on a pulley 62-which in turn is set in rotation by a motor 60 through a belt 63. The carriage 61 can therefore move in the direction parallel to the front of the bending press. Parallel to the screw without end 39, a bar 64 extends, which form the axis of rotation of the reference element 38. A cylinder-piston unit 65, whose vertical rod 66 is hinged to the reference element 38 while the cylinder is hinged to the reference-bearing block 36 causes the rotation of the reference 38 around the bar 64, in such a way so as to produce the projection or the retraction of the reference element 38 from the reference bearing block 36. The operation of the panel machine previously illustrated will be now described. Initially, the operator takes a sheet to be machined, opens the door 8 in order to accede to the work plane 1, and positions the sheet to be machined on the work plane, in a roughly central position. Therefore, the operator closes the door 8 and he turns the panel machine on. The mechanical hand 4, initially in a position distant from the bending press 2 and with the upper jaw 14 lifted, moves toward the bending press. In the meantime, the thrust means 19 is activated by the relative cylinder 52, and moves along the relative slide toward the front of the bending press 2, in such a way so as to abut against the back edge of the sheet to be machined and to push the latter toward the bending press. Simultaneously, the two retractable reference elements 38 project, so that the fore edge of the sheet, pushed by the thrust means 19, abuts against the same reference elements. The conformation of the reference elements 38 is such as to allow the centring of the sheet to be machined, in a direction parallel to the front of the bending press, whether or not this has sheared corners. The possibility to move the reference elements 38 in a direction parallel to the front of the bending press allows the centring of sheets having variable dimensions. Therefore, the operator has not to worry about positioning the sheet on the work plane in a precise manner. At this point, the reference elements 38 retract, and the thrust means 19 returns to its rest position, in such a way as not to represent an obstacle during the following stages of the machining. The upper jaw 14 lowers and in co-operation with the jaw 13, it holds the sheet in a substantially central position. Therefore, the mechanical hand moves the sheet forward, toward the bending press. The upper wing 22 of the latter is lifted, so that the upper blank holder is enough distant from the lower blank holder 26 to allow the passage of the sheet. Once the latter has been introduced in the bending press, the cylinder 24 produces the lowering of the upper wing 22 so that the upper blank holder 27 presses against the lower blank holder 26, an edge of the sheet to be machined projecting inside the bending press. At this point, the cylinders whose rods are indicated by 32 and 33 in Figure 4 set in motion the blade holder 28, whose bending blades 34 and 35 cause bending of the edge of the sheet, in co-operation with the blank holder 26, 27. Once the edge of the sheet has been bent in the desirable way, the upper wing 22 of the bending sheet is lifted, and the sheet released from the hold of the upper blank holder 27. The mechanical hand 4 backs, removing the sheet from the bending press and, if other edges of the sheet have to be bent, it carries out the rotation of the sheet by 90° or 180° by means of the rotator 16. When the sheet has been rotated in the desired manner, the mechanical hand moves forward again bringing the edge of the sheet to be machined inside the bending press, and the operations described above are repeated. At the end of the machining of the sheet, the operator stops the machine, he opens the door 8, and he removes the sheet from the work plane, he takes a new sheet, he positions it on the work plane, he closes the door and turns the machine on.

Claims: Machine for the production of metal sheet panels with bent edges, comprising a work surface (1) for a sheet to be machined, a bending press (2) provided with a bending die and located frontally to the work plane, a mechanical hand (4) mobile as regards the work plane for the displacement of the sheet (5) during machining, sheet positioning means (19, 38) to automatically position the sheet (5) to be machined after this has been introduced by the operator on the work plane (1), characterised in that the work plane is substantially enclosed inside a protection structure (6), said protection structure comprising at least one opening (7) of access to the work plane for the feeding to and the removal of the sheet from the work surface on behalf of a human operator, and in that said at least one access opening (7) is associated to respective means (8) for the interdiction of the access to the work plane during machining, said sheet positioning means (19, 38) being enclosed in said protection structure (6) and comprising retractable reference elements (38) normally retracting as regards the upper surface of the work plane (1) and suitable to project as regards said upper surface of the work plane during a stage of the positioning of the sheet (5) to engage a front edge of the panel, and a mobile thrust means (19) that engages a back edge of the sheet to push the front edge of the sheet against said reference elements. Machine according to claim 1, characterised in that said interdiction means (8) of the access to the work plane (1) comprise a door associated to said opening (7), openable by the operator for the introduction and the removal of the sheet (5) before and after machining, and closable to prevent the access to the work plane during machining. Machine according to claim 2, characterised in that said door (8) is mounted on said protection structure (6) in correspondence of said opening (7) in such a way as to result to be turnable around a horizontal axis. Machine according to claim 1, characterised in that it comprises a pair of said retractable reference elements (38). Machine according to any one of the previous claims, characterised in that said mechanical hand is mobile in a direction towards/away from said bending press (2) and it comprises a vice (12) suitable to clamp the sheet (5) to be machined in position substantially central to the same, and a rotator (16) suitable to rotate the sheet (5) in said work plane (1).

Inventors: KUNZE WOLFGANG, VENTURINI GIANFRANCO, KUNZE, WOLFGANG, VENTURINI, GIANFRANCO
Applicants: SALVAGNINI ITALIA SPA, SALVAGNINI ITALIA S.P.A.
Application year: 1998
Main classification: B21D5
IPC codes: B21D55, B21D5, B21D43, B21D47, F16P3, B30B15