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

Definitions

• This invention deals with a device for the automatic adjustment of the bending pressure, proportionally to the working pressure of the cylinders of the upper cross-piece particularly in a bending press machine, and so-obtained machine.
• the innovation finds particular, though not exclusive, application in processes and relative systems of metal processing and in general in the field of sheet deformation.
• Background Art Bending presses are known. They are often used in metallurgical industry, and in particular in the processing of metal sheets, to obtain, e.g. longitudinal sections in different forms, sometimes with the possibility of being taken up and each one of them again being subjected to a press-bending cycle.
• a so-called bending cycle consists essentially in the vertical descent of a tool up to touching the lower sheet metal resting on the bench, in the execution of the bending, and therefore at the end, in proceeding with the ascent, up to reaching a starting position.
• the machine is made up of two parts, respectively a first dynamic one which generally constitutes the upper part, and a static part which constitutes the underside of the machine and is placed on the perpendicular of the dynamic part.
• the tool in the execution of a bending cycle, completes exclusively a vertical to-and-fro movement, ensured by at least two oleodynamic end cylinders which determine the descent, the eventual stop, and the ascent of an upper cross-piece which supports the tool longitudinally.
• the underside of the bending press machine it includes a lower correspondent cross-piece on the perpendicular of the upper cross-piece, which is substantially intended to hold up a matrix and for possible measuring devices and control of the bending.
• a negative and more or less common aspect in the pre-existing solutions relates to the deformation to which the machine framework is submitted in working condition.
• the drawback in more detail consists in the transversal determination to the metal sheet, a certain convexity or concavity in the product submitted to the working cycle, a fact which also can be attributed to the irregular distribution of the force on the punch.
• some of these deficiencies can be corrected by appropriate bending devices or by recovering the flexures that make the lower cross-piece dynamic, suitable for contacting a data process unit, which at present still are not sufficiently able to be modulated and easy.
• variable working conditions include the length of the piece to bend, the thickness, the breaking load of the material and finally the position, lengthwise of the press, in which the bending operation is carried out. Quoting these circumstances, the bending or curving is aimed at recovering the curvature deflection caused by the bending effort on both cross-pieces, upper and lower, whose deformations are proportional to said bending effort.
• the hydraulic bending systems include a series of jacks which work contextually along an intermediate part of the lower cross-piece, and in more detail, on the base of a part of same, better known as an action cross-piece with two corresponding reaction cross- pieces on the outside.
• the main drawback of the known systems is that they present limits in the control of the bending pressure which, at present, is automatically defined by the numerical control provided together with the bending machines.
• the charging technique of the determination and calculation parameters for the intervention in the lower cross-piece deformation requires preliminarily the execution of a test series, which technically only count the sheet pieces, bent in the centre with respect to the machine.
• a second machine clearly more complex than the preceding, has supplied the use of two transducers, one for each cylinder of the upper cross-piece, each of which transmits the pressure with a numerical control and contacts with a common proportional valve which elaborates certain data regarding each sheet position, independently if it is placed on the centre or on the sides.
• the present self-balanced bending system can adapt full-automatically the bending pressure proportionally to the working pressure of the single cylinders of the upper cross-piece of the press-bending machine, no matter the loading entity and position regarding the length of the bending machine. Therefore an adjustment by the final user is not required, allowing a fair reduction of the working time, with a lower dead time introducing evident benefits from an economical point of view, and at the same time, allowing the realization of practically perfect bends.
• the initial calibration phase practicable in its origin by the subject manufacturer, it requires only a short intervention with minimal waste material for a subsequent tight closing.
• Figure 1 represents a view of a press-bending machine in static state, and of a relative interaction circuit with an adjusting device for the bending pressure, proportionally to the working pressure of the single cylinders.
• Figure 2 is a view in a dynamic state, always of a press-bending machine as in figure 1 , and of a relative interaction circuit with an adjusting device for the bending pressure, proportionally to the working pressure of the cylinders, where a working cycle is provided with the central positioning of the sheet to press-bend.
• Figure 3 is a view, always in dynamic state, of a press-bending machine as in the preceding figures and of a relative interaction circuit with an adjusting device for the bending pressure, proportionally to the working pressure of the cylinders, where a working cycle is provided on the right side with the positioning of the sheet to press-bend.
• FIG 4 is a view, still in dynamic state, of a press- bending machine as in the preceding figures and of a relative interaction circuit with an adjusting device for the bending pressure, proportionally to the working pressure of the cylinders, in which one provides a working cycle with the positioning of the sheet to be press- bend, on the left side.
• a press- bending machine (A) is essentially composed of an upper cross-piece (1), which can be moved vertically along the axis (Y'-Y") regarding the framework of the press-bending machine (A), on the upper end of which one provides associated longitudinally, an interchangeable tool, which forms the punch (2).
• the machine (A) provides at the ends, a cylinder group (3-3') per side, which determine the descending movement and vice versa along the axis (Y'-Y") of the upper cross-piece ( 1 ) towards the underlying lower cross-piece (4), which in its turn provides a matrix (5), it also being interchangeable.
• a bending device is provided, working on the lower cross-piece (4) and made up of a series of lined-up hydraulic jacks (6), in this case three.
• Said jacks (6) load on the base of an action cross-piece, placed on the lower cross-piece (4) in an intermediate position regarding two reaction cross-pieces, with co-ordinated activities of the device (C) to adapt the bending pressure proportionally to the working pressure of the single cylinders (3, 3') of the upper cross-piece, said device (C) being interposed along a circuit contacting the same.
• the device (C) interposed along a connecting circuit (9, 9') contacting the cylinders (3, 3') of the upper cross-piece with the cylinders (6) of the bending device provided on the lower cross-piece (4) is based on a system essentially made up of a first release valve (7) and a balance cylinder (8) for the proportional control of the cylinder pressure (6) of said bending device.
• the release valve (7) is represented with a slightly smaller closing surface regarding the pushing surface of the balance cylinder (8), so ensuring the perfect closing of the release valve (7).
• the release valve (7) proportionally controls the pressure of the bending cylinders on the basis of the fulcrum position (10).
• the outgoing pressure (side D) of the release valve (7) will always be lower than the incoming one (side E), but the relation rod-balance ( 11), subjected to adjustment (16) by the fulcrum (10), sees to it that the balancing cylinder (8) always ensures the closing of the release valve (7 ) .
• a second part of the device (C) interacting with the first, is made up of a second release valve (12) and a relative contrast means given by a balancing cylinder (13). Both have a security and control function, so that the pressure of the bending cylinders does not exceed the one necessary for the good result of the bending.
• the closing of the first release valve (7) is commanded by the balancing cylinder (8) which acts mechanically by a balance ( 1 1 ).
• the closing of the second release valve ( 12) is commanded by the second balancing cylinder (13) which acts mechanically by means of a second balance (14).
• the fulcrum position ( 10) on which the two rocker arms are rotating, respectively (1 1 ) and ( 14), is adjustable by handwheel means (16) to allow the balanced calibration between the pressure of the press cylinders (3, 3') and the cylinders (6) of the bending device.
• the field of the fulcrum adjustment (10) is limited in order to ensure that, with equal pressure, the force exerted by the balancing cylinder (8) always exceeds the one provoking the opening of the release valve (7).
• This calibration is originally developed in the factory, successively by bending tests, adjusting the handwheel screw ( 16), finding the precise fulcrum position (10), and so calibrating balances ( 1 1 , 14) according to the real cylinder pressures (3, 3') and the real balancing pressures of the cylinders (6), obtaining this way a constant angularity of the bent piece be it over the total length of the machine, as well as the lateral bending to the various possible pressures of the machine.
• the device (C) is adjusted.
• a switching valve (15) is provided on machine (A). This valve (15) is aimed at contacting the bending cylinders (6) with the pressure of the press cylinder (3, 3') contacting the cylinder with the minor pressure.
• the right-hand cylinder (3) will have the higher pressure; this pressure will displace the cursor of the switch valve or interception valve (15) so that it uses the pressure of the left- hand press cylinder (3'), in order to activate the bending contextual phase, which is lower than that of the right-hand press cylinder (3).
• This function is important, because on the lateral bending, the sole cylinder on the side of which one bends, exerts the necessary force for the bending, and the so-caused pressure can also be twice the pressure necessary for bending the same piece in the machine centre.
• the release valve (7) controls proportionally the pressure of the bending cylinders (6) on the basis of the fulcrum position (10). So that the outgoing pressure (side D) of the valve (7) will always be lower than that the incoming one (side E), but the relation rod-balance (1 1), determined by the fulcrum adjustment (10), sees to it that the cylinder (8) always ensures the closing of the valve (7).
• the oil flow coming from the intercepted cylinder (3') will continue to supply the bending cylinders (6), until its pressure will allow to leave the valve open (7), or until the pressure of this cylinder (3') and that of the bending cylinders (6) will be proportionally balanced.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Press Drives And Press Lines (AREA)
• Catching Or Destruction (AREA)
• Finger-Pressure Massage (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (1)

• 1997
  • 1997-06-13 IT IT97TV000079A patent/IT1293371B1/it active IP Right Grant
• 1998
  • 1998-06-02 WO PCT/IT1998/000148 patent/WO1998056518A1/en active Application Filing
  • 1998-06-12 AR ARP980102825A patent/AR012984A1/es active IP Right Grant

Patent Citations (1)

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