Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
  • B21D5/02—Bending sheet metal along straight lines, e.g. to form simple curves on press brakes without making use of clamping means
  • B21D5/0272—Deflection compensating means

Definitions

• This invention has for object a process for metal sheet press-bending with direct measuring system, comprising a compensation and control function of the upper and lower cross-pieces deformation, and press-bending machine so obtained.
• the innovation finds particular even if not exclusive application in metal working processes and in general in the field of heavy carpentry.
• Bending presses are known. They find wide use in metal and mechanical industry, and in particular in the cold-working of metal sheets, for example for obtaining differently shaped longitudinal sections , sometimes with the possibility of being taken up and, each of them, subjected again to a press-bending cycle.
• a so-called bending cycle consists essentially of the vertical descent of a tool up to touching the underlying sheet foil resting on the bench, in the carrying out of the bending, and then, at the end, in the lifting, up to reaching a starting position.
• the machine is made up of two parts, respectively a first dynamic one, generally regarding the upper part, and a second one, as a static part, making up the underside of the machine placed below the dynamic part.
• the tool in the execution of a bending cycle, the tool, made up of a differently formed blade also of the interchangeable type, operates exclusively a vertical to and fro movement, ensured by at least two oleodynamic cylinders, which determine the descent, the eventual stop, and the lifting of an upper cross-piece which supports the tool longitudinally.
• some drawbacks are noticeable, which, in general, refer the inaccuracy of the bending angle and are in any way related to an objective difficulty of predetermination and measuring of the same.
• the traditional system provides that, giving a known total height of the elongated matrix or depth of the elongated bending groove in the bend, and the thickness of the material, the elongated punch lowers for touching the sheet impressing on it the required angle.
• the elongated punch descent is calculated mathematically, and consequently, it provides to set the machine in function of the angle desired.
• the result is not always optimal, as, such technique, many times leads to obtaining angles with some errors even if limited ones. This happens because of the concourse of different factors, such as for example, the thickness of the different materials which is not constant, where also the incidence of few hundredths of a millimetre influence the working negatively.
• said elongated matrix provides two coplanar surfaces, movable on horizontal plane, defining in a intermediate position a longitudinal groove whose bottom may be eventually modified in height.
• Such groove determines the momentary bending angle by means of the relative position of both the support surfaces on the side of the groove, which delimit its opening, and the bottom of the groove itself.
• persists a certain inaccuracy one of whose causes is ascribable to the phenomenon of the elastic return of the sheet, a condition which occurs at the moment which follows the piece discharge, altering the bending angle originally determined and theoretically calculated.
• the process consists in that it provides: - in a first phase, the adjustment in height of the elongated matrix bottom occurs on the basis of the first angle to be obtained, which is a little wider respect to the given nominal angle, where the sheet is bent on the basis of this first angle by the lowering of the elongated punch up to the elongated matrix bottom; - in a second phase, the section is discharged, so that a return of the same in the stretched position occurs; - in a third phase the measured angle deriving from the returned and stretched section, is compared with the first angle and the position of the elongated matrix bottom is adjusted with a value that corresponds to the nominal angle minus the difference between the angle measured on the released section and the first angle; - in a fourth phase the bent sheet is completely pressed by the elongated punch again charged against the elongated matrix bottom, which will take a correct position in height.
• At least a third feeler means is privided, which predisposed in an intermediate position in respect to a couple of end feelers for the measuring of the bending angle, allows, during the bending cycle, to adjust the eventual flexion of the cross-pieces and matrix, after having detected the misalignment among these, and being in communication with the data process unit of the machine, starts a swelling device, provided in the lower cross-piece, and essentially made up of hydraulic jacks, which being co-ordinated in the operation, act dynamically on the upper part of the same cross-piece modifiyn the the linearuty of said matrix. In this way it is possible to reduce the bending time, accelerating the whole productive process with evident benefits otherwise not obtainable from an economical point of view.
• Such aspect is mainly due to the quick measuring system of the bending angle, allowing the intervention, in a resolute way, for the correction of the error, being able to obtain the nominal bending angle with the utmost precision.
• the reading during the bending occurs on the same side of the sheet thus avoiding bending errors at the change of the thickness of the same, obtaining a perfect bending angle.
• the correct carrying out of the working is eased by a renewed swelling device, which is able to intervene rapidly during the bending cycle, with the utmost effectiveness with regard to the flexions recovery of the cross-pieces.
• Figure 2. represents a view, always in detail, of a subsequent working phase, in which the elongated punch is shown in active condition, up to deforming a sheet foil, penetrating onto the elongated matrix.
• Figure 3. is a prospect view of the press-bending machine, where one part of the elongated punch and of the underlying elongated matrix is disclosed , this part being shown in section.
• Figure 4. shows an enlarged view, of said part corresponding to a part of the section of the elongated matrix of a lower cross-piece.
• Figure 5. is a side view of the press-bending machine as shown in Figure 2., with a portion of the elongated matrix, enhanced in section.
• Figure 6. shows a schematic view in detail, of a data recording group, showing at least one linear transducer.
• Figure 7. shows a schematic Figure of the swelling device which is in the lower cross- piece.
• Figure 8. is an enlarged view, in section, of the lower cross-piece portion, regarding by the swelling device of the previous Figure.
• a press-bending machine (A) is made up of an upper part and of a lower part, the first essentially dynamic respect to the static second one.
• the first one includes an upper cross-piece (1), vertically movable along the axis (V- Y") in respect to the frame of the press-bending machine, on whose lower end an interchangeable longitudinal tool to realize the elongated punch (2) is provided.
• the body of the machine (A) provides at the ends, a cylinder group (3) for each side, which determines the descent (and vice versa) movement along the axis (Y'-Y"), of the upper cross-piece (1) towards the underlying lower cross-piece (4), which supports an elongated matrix (5) also of the interchangeable type.
• Said elongated matrix (5) has longitudinally, at least one elongated bending groove (5') that determines the bending angle " ⁇ " of a sheet foil (B) subjected to a bending working cycle.
• At least two measuring areas are provided, said areas being placed for example at the ends of the same one, or near to the sheet ends (B), respectively a right one and a left one (r'-r"), to which a third intermediate area, (c) is added, which in the case has the purpose of interacting with a flexion measuring device (C) for the recovery of the cross-piece flexions.
• a flexion measuring device C
• two opposite corners (6, 7) are provided, on which works the sheet back (B) in bending phase.
• the elongated bending groove (5') has on the bottom, logically corresponding to each of the three areas (r'-r", c), a series of holes (8), on whose inside is vertically movable, following a stroke (yl), a relative nail-like feeler (9).
• Said feeler (9), in correspondence of the upper end is provided with a rounded and with a larger diameter head (9') suitable to push permanently on the sheet back (B), while on the other side, always said feeler (9), is connected with a relative measuring group which transmits the data to an information logical data process unit.
• the measuring system of the bending angle " " that concerns at least the two end areas (r'-r") uses substantially three measuring points for each of them, respectively, two regarding the corners and a third regarding an intermediate point (9'), as intersection point of the back or lower side of the sheet (B) with the bending axis (Y'-Y").
• the exact position of these point (9') is detected by said nail-like feeler (9), that is maintained pressed against the back of the sheet (B).
• the same nail-like feeler (9) is mechanically connected , with a relative linear transducer (14,14a), of the high precision type, which constantly controls its position.
• the program of the data processing unit calculate mathematically, relating to the bending radius, the stroke (y) of the descent of the elongated punch (2), in function of the fixed distances, (x2), measurable between the contact corners (6,7), thus establishing the required bending angle.
• the stroke (y) of the descent of the elongated punch (2) is the same stroke (yl) detected by the feeler (9), which, is read by the corresponding linear transducer (14,14a).
• the measuring system of the bending angle " " in a sheet (B) concerns at least the two areas (-r") placed next to the ends of the sheet piece (B) to be subjected to the working cycle.
• each of said two areas (-r") additionally, includes a respective feeler (9), of the nail-like type, which downwardly is connected by levers with a corresponding linear transducer (14-14a).
• said levers consist of a couple of small arms (11, 15) of the balance type and opposed one to the other, and being hinged to the machine body, and being movable in a synchronous way and engaged respect to a common end (11', 15'), at the base (9") of the feeler (9).
• the opposite end (11") of a first small arm (11) is longitudinally engaged, by a connecting clamp (12), with a longitudinal bar (13), which activates the respective linear transducer, the right one or left one (14, 14a).
• the second small arm (15), over said first one, has the opposite end (15"), engaged with an helicoidal spring (10), that allows to duly contrast the descent action of the feeler (9), and in the release phase, to reset it in the original position.
• an helicoidal spring (10) that allows to duly contrast the descent action of the feeler (9), and in the release phase, to reset it in the original position.
• a further couple of linear transducers is further provided, two upper ones (23) are exclusively read for the fast descent and the lifting, while the other three, as it has been seen, are connected to the nail-like feelers (9), and are read during the true bending phase.
• a first phase for preparing or setting up the machine is provided .
• Two of these, as already observed, must be placed in correspondence of the end of the piece to be bent (B), while the central detecting device (c), has to be placed at the centre between said opposed two (r', r").
• the central part (c) of said measuring groups is part of a device (c) for the recovery of the flexures of the cross-pieces or bulging device.
• Said central part (c) is analogously made up of a feeler (9), of the nail-like type, on whose base (9") are keyed the ends of analogue balance levers (11, 15).
• One of these (11) is engaged at the opposite end (11") with a central bar (19) provided at the end of a position signalling means or reference signaller (20), signalling the position of the control bar of the bulging device (C).
• Said position signalling means (20) being engaged along the central bar (19), interacts with a sensor (21) engaged to the rod (13) of at least one of the two linear transducers (14, 14a).
• the bulging device (C) provides that, along a lower cross-piece (4), centrally, there is a break (4a), in which are housed some hydraulic jacks (22). These jacks (22), have substantially, the base of the cylinder that rests both on the central cross-piece and on the stiffening lateral ones, while regarding the steams of the jacks, they pass solely on the central cross-piece.
• the upper cross-piece (1) of the pressing machine (A) descends at high speed carrying the elongated punch (2) towards the elongated matrix (5).
• Such displacement is electronically controlled, thanks to two opposed linear transducers (23), placed on the sides of the press (A).
• the elongated punch (2) slows and passes to a low speed up to touch the surface of the sheet itself (B). It is in this moment in fact that the reading related to the stroke of the elongated punch (2), is carried out by the linear transducers (14, 14a) placed on the bench (16).
• the sheet (B) pressed by the elongated punch (2) pushes the feelers (9), that start the reading mechanisms on the bars (13, 19).
• the machine sets itself for a following and definitive bending cycle, which without discharging the product (B), will be carried out with correction parameters compared and obtained by the reading and processing of data collected in the previous phase.
• the measuring group (r r , r) that includes at least one sensor (21), engaged along a bar (13), with an intermediate measuring group (c) that includes at least one reference signaller (20), engaged along the central bar (19), is activated the bulging device (C).
• the jacks (22) push on the central cross-piece exerting a flexion on the upper part of the same.
• the bench (16) curves deforming in a way almost specular to the deformation that concerns the upper cross-piece (1) during the bending phase of the sheet (B), maintaining both of them parallel.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)
• Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• A Measuring Device Byusing Mechanical Method (AREA)

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Cited By (4)

Citations (5)

• 1997
  • 1997-04-11 IT IT97TV000039A patent/IT1293174B1/it active IP Right Grant
  • 1997-10-16 WO PCT/IT1997/000251 patent/WO1998046378A1/en active Application Filing

Patent Citations (5)

Non-Patent Citations (1)

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