Machine for bending sheets of metal

Abstract: A machine for bending sheets of metal comprises a counterblade (5) integral with a fixed base (1), a movable sheet metal holder (40) above the counterblade (5), first operating means for moving the sheet metal holder (40) in a vertical direction with respect to the counterblade (5); the sheet metal holder (40) is integral with a support (4) hinged to at least one crank (3) integral with a shaft (2) rotatably connected to the base (1), and second operating means (9, 10, 42) are provided to determine the rotation of said shaft (2).

Description: The present invention relates to a machine for bending sheets of metal. Machines for bending sheets of metal are known wherein the sheet of metal to be bent, arranged horizontally, is initially clamped between two casings, one lower known as "counterblade", integral with the base of the machine and acting as support for the sheet of metal, and one upper, known as "sheet metal holder", that can be moved vertically between an upper position for the introduction of the sheet of metal and a lower position for clamping and holding the sheet itself in position; the sheet of metal is positioned so that one edge thereof, destined to be bent, protrudes horizontally with respect to the edges of the counterblade and of the sheet metal holder, and the sheet metal holder is made to slide along vertical guides by hydraulic cylinders placed at its ends. The sheet of metal is subsequently bent upward by a lower bending blade that is under the edge to be bent or downward by an upper bending blade that is above said edge, said upper and lower blades constituting a pair of bending blades integral with a common support that can move in an independent manner in the vertical and horizontal directions. Such a machine has for example been described in the EP-A-0022122. In EP-A-0293964 there is described a bending machine according to the pre-characterising part of claim 1 wherein the movement in the vertical direction of the sheet metal holder is obtained by means of the rotation of the sheet metal holder itself about a horizontal axis, placed sufficiently far from the line of bending (that is, from the edge of the counterblade) to allow the assimilation of its effective circular trajectory to a substantially rectilinear trajectory on the short stroke actually executed in its movement between said high position and said lower position. The fact that the sheet metal holder can move only in a substantially vertical direction with respect to the counterblade, integral with the base, that also co-operates in clamping the sheet of metal, limits the variety of the combinations of bends that can be executed with traditional machines. US-A-3 662 584 discloses a sheet metal bending apparatus comprising a lower sheet metal holder which is movable in horizontal and downwards direction with respect to an upper sheet metal holder in order to enable a bending member to perform tight bends of said sheet metal, beyond 180°. In view of the state of the art as described, the object of the present invention is to provide a machine for bending sheets of metal wherein the sheet metal holder, as well as in a substantially vertical direction, can also be moved in a horizontal direction with respect to the base of the machine, and thus with respect to the counterblade. According to the present invention such object is attained by means of a machine for bending sheets of metal as defined in claim 1. Thanks to a machine according to the present invention, the sheet metal holder can be moved both vertically and horizontally with respect to the counterblade. This determines a high degree of flexibility in the use of the machine, thanks to a much greater variety in the type of bends that it is capable of executing. These and other advantages of the present invention will be made more evident by the following detailed description of an embodiment thereof illustrated as an example in the enclosed drawings, wherein: Fig. 1 is a vertical side view of a machine embodying the invention; Fig. 2 is a simplified rear view of the machine of Fig. 1; Figs. 3, 3'-6, 6' show in detail a bending area of the machine in different operational steps of the machine according to the invention to obtain four different types of bend of the sheet. With reference to Figs. 1 and 2, a bending machine according to an embodiment of the invention comprises a base 1 to which, in the front, a counterblade 5 is integrally fastened that operates as a support for a metal sheet 6 to be bent; a sheet metal holder 40 is placed above the counterblade 5 and is integrally fastened to a support 4, that at the rear end of the machine is hinged at two points 11 to two respective cranks 3 integral with a torsion shaft or bar 2. The torsion bar 2 is rotatably connected to the base 1 by means of two supports 41 integral with the base 1 and provided with through holes into which the ends of the torsion bar 2 are inserted. A third crank 9 is fastened integrally to the torsion bar 2 in a median position, and is hinged to a stem 42 of a hydraulic cylinder 10 in turn hinged to a flange 60 integral with the base 1. The support 4 of the sheet metal holder 40 is also hinged to a Linear succession of hydraulic cylinders 12 (only one shown in Fig. 1) whose stems are hinged to the base 1. A pair of bending blades 7 and 8 and a unit for moving them are placed in the cavity between the base 1 and the support 4 of the sheet metal holder 40. The pair of bending blades comprises an upper blade 7 and a lower blade 8, suitably shaped (Figs. 3, 3'-6, 6') fastened to a support 43 through which the stems of the cylinders 12 pass; such support 43 is hinged at the opposite end with respect to the blades 7 and 8 to a crank 44 integral with a shaft 45; a further crank 46, also integral with the shaft 45, is hinged to a stem 47 of a hydraulic cylinder 48 integrally fastened to the base 1. The shaft 45 is rotatably connected to the base 1. The support 43 for the pair of blades 7 and 8 is provided at its lower end with a flange 49 hinged to a stem of a further hydraulic cylinder 50, hinged to the base 1. Fig. 2 is a simplified view, and in it, for greater clarity, neither the bending blades nor the corresponding moving unit are shown. The hydraulic cylinders 12 determine the vertical movement of the sheet metal holder 40, that is, its upward and downward movement with respect to the counterblade 5; more specifically, the extension of the stems of the cylinders 12 determines the raising of the sheet metal holder 40, while their reversal determines the lowering of the sheet metal holder 40 over the sheet of metal 6, so that the latter is kept in position while it is being bent. The trajectory described by the sheet metal holder 40 is in effect an arc of a circumference, since the support 4 rotates about a horizontal axis passing through the points 11 at which the support 4 itself is hinged on the cranks 3; but since the axis of rotation of the support 4 is rather distant from the sheet metal holder 40, the radius of such arc of a circumference is very large, and the trajectory of the sheet metal holder 40 is practically rectilinear vertical. The hydraulic cylinder 10 on the other hand determines the longitudinal horizontal movement of the support 4, and thus of the sheet metal holder 40: the extension or the reversal of its stem 42 in fact determines, through the crank 9, the rotation of the torsion bar 2, and thus the rotation of the two cranks 3; the latter, being hinged to the support 4, determine its substantially rectilinear horizontal motion. The pair of bending blades 7 and 8 can move both in the longitudinal horizontal direction and in the vertical direction: the extension or the reversal of the stem 47 of the hydraulic cylinder 48 determines the rotation of the crank 46 and thus that of the shaft 45 and of the crank 44; the latter determines the forward or reverse movement of the support 43, and thus of the pair of blades 7 and 8. The hydraulic cylinder 50 on the other hand determines a motion of rotation of the support 43 about a horizontal axis of rotation passing through the hinge point with the crank 44, a motion that translates into a substantially vertical movement of the blades 7 and 8. Some advantages of the machine embodying the invention will now be exemplified with reference to Figs. 3, 3'-6, 6', tending to show four examples of the use of the machine for the execution of bends that are not normally possible using bending machines according to the known art. There are shown in Figs. 3 and 3' two operational steps of the machine embodying the invention for the execution of a first type of bend. More specifically, there is shown in Fig. 3 the sheet of metal 6 after it has been submitted to a first bend, that can also be obtained with traditional machines: the sheet 6 is positioned so that, when the sheet metal holder 40 moves downward, an edge 13 protrudes over the line of bending, defined by the edge of the counterblade 5; the edge 13 is thus bent to form an angle β with the rest of the sheet 6 itself, an angle that is substantially determined by the conformation of the sheet metal holder 40; such a bend is made by initially raising the lower bending blade 8 (by operating the cylinder 50) and making it then move forward (by operating the cylinder 48). If this preliminary bend is followed, as shown in Fig. 3', by a horizontal backward displacement of the sheet metal holder 40, by operating the cylinder 10, the bending angle of the edge 13 of the sheet 6 can be increased up to a value α: this is obtained, for example, by lowering the upper blade 7 (by operating the cylinder 50). The final bending angle α that can be obtained thanks to the machine according to the embodiment of the invention, is thus greater than the angle that can normally be obtained with traditional machines. In other words a first bend is executed up to the maximum angle β allowed by the non-interference of the edge 13 with the sheet metal holder 40, and then a second bend after moving the sheet metal holder 40 horizontally backward (by operating the cylinder 10), so that the latter limits the movement of the edge 13 to a lesser extent. There are shown in Figs. 4 and 4' two operational steps of the machine for the execution of a second type of bend. The sheet 6 is made to move forward over the counterblade 5 so that, when the sheet metal holder 40 moves downward, an edge 14 protrudes beyond the line of bending, again defined by the edge of the counterblade 5. The upward movement of the lower bending blade 8, following the operation of the cylinder 50, determines the progressive upward bending of the edge 14 until the latter forms a right angle with the sheet 6 itself. The sheet metal holder 40 is raised and the sheet is made to move forward so that, when the sheet metal holder 40 moves downward again, an edge 14' protrudes with respect to the line of bending; the upward movement of the lower blade 8 determines a preliminary upward bend of the edge 14', until this is prevented by the interference between the edge 14 and the casing of the sheet metal holder 40 (Fig. 4); the sheet metal holder 40 is then made to move backward with respect to the line of bending, and the further upward movement of the blade 8 completes the bend of the edge 14', that ends when this forms a right angle with respect to the sheet 6 (Fig. 4'). In traditional machines, the length of the edge 14 is limited by the distance between the line of bending and the casing of the sheet metal holder 40 (as shown by the dashed line in Fig. 4); but in the machine embodying the invention, if the edge 14 of the "C-shaped" bend is to have a greater length, it is sufficient to move the sheet metal holder 40 further back with respect to the line of bending after a first bending of the edge 14'. There are shown in Figs. 5 and 5' two operational steps for the execution of a 180° upward bend, not normally possible using traditional machines. The sheet 6, possibly after having been subjected to other preliminary bending operations, is made to move forward over the counterblade 5 so that, after the downward movement of the sheet metal holder 40, an edge 15 protrudes with respect to the line of bending, again defined by the edge of the counterblade 5. The lower blade 8 is then raised (by means of the cylinder 50) and subsequently made to move forward (by means of the cylinder 48) so as to bend the edge 15 up to the maximum possible angle (substantially equal to the angle β of Fig. 3). During this step the sheet metal holder 40 is aligned with the line of bending. The sheet metal holder 40 is subsequently moved backward with respect to said line of bending by activating the cylinder 10, so that a part of the sheet of metal 6 is left uncovered. By operating the cylinder 50, the downward movement of the upper bending blade 7 is determined: this presses against the edge 15 of the sheet until the desired 180° bend is obtained. There are shown in Figs. 6 and 6' two operational steps suitable for obtaining a 180° downward bend, also not normally possible using traditional machines. As before, the sheet 6, possibly after having been subjected to prior bending operations, is made to move forward with respect to the counterblade 5 so that, when the sheet metal holder 40 moves downward, an edge 16 protrudes with respect to the line of bending, that is, to the edge of the counterblade 5. The cylinder 50 is then activated that determines the downward movement of the upper blade 7, and subsequently the cylinder 48 that determines the forward movement of the same to bend the edge 16 with respect to the sheet 6, as shown in Fig. 6; during this step the sheet metal holder 40 is aligned with the line of bending. The sheet metal holder 40 is made to move forward with respect to said line (by means of the cylinder 10), so that it protrudes with respect to the counterblade 5; the sheet 6 is also made to move forward with respect to the counterblade 5. When the cylinder 50 is activated the upward movement of the lower blade 8 is determined, that presses the edge 16 against the lower surface of the sheet metal holder 40 until the desired 180° bend is obtained.

Claims: Machine for bending sheets of metal comprising a counterblade (5) integral with a fixed base (1), a movable sheet metal holder (40) above the counterblade (5), first operating means (12) for moving the sheet metal holder (40) in a vertical direction with respect to the counterblade (5), a pair of opposed bending blades (7, 8) integral with a common support (43) and operating means (44-48, 50) for moving said pair of bending blades (7, 8) comprising a horizontal movement unit (48) and a vertical movement unit (50), characterized in that said sheet metal holder (40) is integral with a support (4) hinged to at least one crank (3) integral with a shaft (2) rotatably connected to the base (1), second operating means (9, 10, 42) being provided to determine the rotation of said shaft (2), whereby to cause movement of said sheet metal holder (40) in a substantially horizontal direction to a position where its nose is not aligned with that of the counterblade (5), while said holder (40) still clamps said sheet metal against said counterblade (5). Machine according to claim 1, characterized in that said second operating means (9, 10, 42) comprise a crank (9) integral with the shaft (2) and hinged to a stem (42) of a hydraulic cylinder (10) integral with the base (1). Machine according to claim 1 or 2, characterized in that said first operating means comprise a plurality of hydraulc cylinders (12) and correspondings stems, hinged the ones to the support (4) and the others to the base (1). Machine according to claim 1, characterized in that said horizontal-movement unit (44 - 48) comprises a hydraulic cylinder (48) integral with the base (1), whose stem (47) is hinged to a first crank (46) integral with another shaft (45) connected in a freely-rotatable manner to the base (1), and a second crank (44) also integral with said further shaft (45) and hinged to the common support (43) of the pair of bending blades (7, 8). Machine according to claim 1, characterized in that said vertical-movement unit comprises a hydraulic cylinder (50) under the common support (43) of the pair of bending blades (7, 8) and hinged to the base (1), whose stem is hinged to the same common support (43).

Inventors: KUNZE WOLFGANG, KUNZE, WOLFGANG
Applicants: SALVAGNINI ITALIA SPA, SALVAGNINI ITALIA S.P.A.
Application year: 1995
Main classification: B21D5
IPC codes: B21D5