This application is a national stage filing under 35 U.S.C. 371 of International Application PCT/IT2004/000581, filed on Oct. 22, 2004. The entire teachings of the referenced Application is incorporated herein by reference. International Application PCT/IT2004/000581 was published under PCT Article 21(2) in English.
1. Field
The present disclosure concerns a kinematic movement system for operating units of avant-garde bending machines. These are automatic machines for bending and shaping sheet metal.
This kinematic system features the electrical actuation and a particular kinematic drive of the main movements responsible for bending. The disclosure differs from machines currently produced which have hydraulic actuation.
The system according to the disclosure can be applied to a compact bending machine. In terms of weight and size such a machine can fit in a container, without the noisy and cumbersome hydraulic control unit. An ecological advantage is that it does not require topping up with great quantities of mineral oil. The machine is faster and more reliable than current machines and has more limited production costs.
This disclosure can be applied in the production of bending machines, and also to industrial bending machines for sheet metal.
2. General Background
It is known that the industry relative to the production of sheet metal items uses bending machines that allow a series of bends to be made in a single piece of sheet metal, in a completely automatic and controlled way, in order to obtain a finished product such as, for example, a cooker hood or a shelf.
It is also known that bending machines for sheet metal normally consist of:
A bending machine of the known type described above, marketed by the applicant hereto, comprises a blade-holder structure with a “C” shaped cross-section, movable in two reciprocally orthogonal directions with respect to the fixed bed, on which the bending blade(s) is (are) fixed.
The profile of the bend that can be obtained with a known automatic bending machine is not just the classic fixed angle profile that can be obtained with a manual bending machine. The simultaneous control of the positioning of the sheet metal and of the pressure exerted on it makes it possible to obtain radial profiles.
The use of traditional blades, particular tools and dies, included in the bending cycle, also makes it possible to form special profiles, without the need for the intervention of an operator when the length or the special tool changes.
The blades are supported by a load-bearing C-shaped structure mounted on the main frame. The unit comprises two blades: the upper one for negative bends (downwards) and the lower one for positive bends (upwards).
The system controls the dimensions of the angles and the thickness of the sheet metal, adjusting the position of the blades by means of proportional valves. All the movements are carried out by proportional control hydraulic cylinders. A special mechanism guarantees the parallelism of the movements of the bending unit.
The presser tool is mounted on an electrowelded structure with four arms, hinged at the rear of the main frame.
The movements of the C-shaped structure and of the tools are controlled by hydraulic cylinders. The cylinders can be programmed by means of the control unit in order to achieve the highest degree of precision during all the bending phases.
Traditional hydraulic bending machines, like other bending machines present on the market, are fitted with a kinematic structure which determines and controls the movement of the blade-holder unit.
This structure can in some cases be the pentalateral type, that is consisting of a closed kinematic chain with five members connected by five kinematic pairs.
The traditional pentalateral type kinematic chain is used in order to provide the machine with torsional rigidity and not therefore with specific mechanical functions. In addition, the pentalateral type is not actuated by frame cranks.
The above-mentioned features and objects of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which:
With reference to
In such machines, the pentalateral is not actuated by means of frame cranks but by hydraulic cylinders. This does not present any singularity combination.
This is a mechanism which presents certain structural and functional limitations, such as:
Specific analyses carried out on traditional bending machines have also shown that the usual mechanism for bending the sheet metal cannot be controlled electrically since the sensitivity coefficients of the tool with respect to the frame cranks are too high.
These high sensitivity coefficients of traditional bending machines are unable to provide the necessary amplification to the torque provided by the reduction motors (brushless motor+epicyclical reduction gear) available on the market. The only type of drive for known kinematic systems is therefore hydraulic.
Other types of motors cannot be used due to the movement laws to be carried out. Other reduction units (ordinary gear trains) are not compatible with the weights and dimensions of the machines.
Another problem is the non-absolute precision of the machine. This is due to the two synchronized movements that make it possible to define the trajectory of the tool are achieved by two groups of hydraulic cylinders which by virtue of their position are not completely independently for the horizontal and vertical movement of the tool.
The hydraulic cylinders responsible for the horizontal movement of the blade-holder unit also produce an unwanted vertical movement. In the same way the vertical cylinders also produce a horizontal movement.
This is due to the positioning of the cylinders which are not at right angles to each other, and also do not form fixed angles with respect to the frame.
This disclosure provides a kinematic system to drive operating units of bending machines. The system is able to eliminate or at least reduce the disadvantages described above.
The disclosure provides a kinematic system to drive operating units of a new concept of bending machines. Servomotors and epicyclical reduction gears are used for the movement of the blade-holder unit instead of the traditional hydraulic actuators.
The servomotors and reduction units make it possible to achieve higher performance levels than those of a hydraulic system. This also ensures a constant delivered torque that cannot be obtained with a hydraulic system that uses accumulators and thus necessarily has a pressure that slowly decreases during bending.
Electric servomotors, by virtue of the intrinsic linearity of their model of behavior, allow the use of advanced control patterns to carry out freely defined trajectories and interpolations, with practically no errors in position and speed. Such levels of performance cannot be achieved with a hydraulic system controlled by means of proportional valves because of the non-linearity caused by the fluid and of the more reduced pass-band of this drive.
These advantages are achieved by a kinematic system for driving the operating units of a bending machine. These features are described in the main claim.
The dependent claims describe advantageous embodiments of the disclosure.
A main advantage of this solution is that the blade-holder unit of the bending machine uses an articulated mechanism. By definition, this is a variable speed mechanism.
This means that, with the same drive speed, very low speeds can be used in the few seconds immediately prior to closing/opening. Decidedly higher speeds can be used during the rest of the presser stroke.
This also allows a further reduction in cycle time and a consequent increase in machine performance.
The machine is actuated electrically, by an appropriate electronic control unit. This employs an original mechanism for the movement of the bending blades. This can produce an amplification of the torque sufficient to generate the force on the tools necessary to bend the thicknesses and lengths as per the machine specifications.
The articulated system that constitutes the mechanism is a kinematic plane mechanism. This is a mechanism in which the members move with plane motion, with the axes of the turning pairs parallel to each other and at right angles to the plane of motion.
From the topological point of view (number of members and type of couplings) this is a closed kinematic chain with five members connected by five kinematic turning pairs.
One of these members is the frame of the machine. This kinematic chain has two actual degrees of freedom. This allows two independent motors. The two frame cranks were chosen as motor elements.
From the geometric point of view, the mechanism:
The mechanism according to this disclosure is such as to be in a condition of dual kinematic singularity (referring to inverse motion) in a neighbourhood of both the above-mentioned configurations.
This dual singularity is achieved by simultaneously aligning the first motor crank with the first connecting rod and the second motor crank with the second connecting rod.
This concept is independent of the geometric dimensions of the members or of the position of the frame kinematic pairs. The amplification effect depends to some extent on these dimensions, and on the working space of the machine.
The blades of the machine according to the disclosure are moved by an articulated system with two degrees of freedom that presents evident kinematic non-linearity, the movement of the bending blades. This is characterized by well-defined bending trajectories, and is made possible and programmable by a special original inverse kinematic algorithm of the non-iterative type. This is inserted in the numerical control or used as a pre-processor. This makes it possible to carry out well-defined trajectories with interpolated axes such as, for example, the classic circular interpolation.
In particular, a method and an algorithm typical of the field of robotics were applied to a machine tool, in an appropriately adapted way. This allows movement control by variables other than the tool coordinates, not orthogonal but independent of each other.
This algorithm defines the law of motion, exactly and without approximation. This corresponds to a desired tool trajectory, unlike what occurs in hydraulic bending machines in which the trajectory is traditionally set in the actuator space, which differs from the Cartesian space, and is therefore approximated regardless of the controller quality.
This algorithm resolves the position kinematics in a non-iterative way and thus with zero error.
According to the disclosure, the inverse kinematic algorithm comprises the subsequent solution of two closed links, each of which corresponds to two non-linear closing equations in two unknown quantities.
The non-iterative solution takes place by geometric type considerations.
This inverse kinematic algorithm, combined with the high precision of the controller that works on electric axes, makes it possible to carry out particular trajectories, other than the circular one, with particular features and uses.
In particular the machine according to the disclosure foresees the use of a new and original bending trajectory. This is unlike the known solutions, which allows the bending blade to turn on the sheet metal without sliding.
This trajectory is particularly useful in processing materials with a protective film as it prevents the film from being torn and the consequent damage to the sheet metal.
In this case, the blade and the sheet metal behave like two conjugate profiles and the resulting trajectory is a sort of circle involute. It can be observed that by mathematically imposing the non-slipping constraint between the blade and the sheet metal, a bond is achieved between the two free (or generalised) coordinates which define the trajectory.
The quality of the semifinished part processed by the machine according to the disclosure is excellent. This is achieved by a considerably quieter machine compared to previous machines and uses reduced quantities of oil for a much simpler hydraulic circuit.
The environmental impact of the new machine is completely different with respect to the solutions known, since it is less noisy and uses considerably less oil.
In
From the structural point of view, the rear part of the blade-holder unit is integral with a plurality of supports 11, while plinths 12 are fixed on its lower part. The supports 11 and the plinths 12 are involved in the action of a particular kinematic system. The chain has two degrees of freedom, depending on two mechanical units indicated, respectively, by 13 and 14.
The articulated system which makes up the mechanism is kinematically considered a plane mechanism. This is a mechanism in which the members move with plane motion. The axes of the turning pairs are parallel to each other and at right angles to the plane of motion.
From the topological point of view, the number of members and the type of couplings, is a closed kinematic chain with five members connected by five kinematic turning pairs.
One of these members is the frame of the machine. This kinematic chain has two degrees of freedom. This allows two independent motors, each installed on the respective mechanical unit.
The first independent servomotor 15 is part of the first mechanical unit 13, to which a crank 16 is fitted, attached in turn to a connecting rod 17, with its other end hinged to a lever 18.
This lever 18 is equipped with a pivot on the shaft 19, while its other end, the one opposite to the coupling point with the connecting rod 17. These branch into a series of elements 18a and 18b, which are coupled to the same number of pins 20a and 20b positioned on the ends of the supports 11 integral with the blade-holder unit 10.
The second mechanical unit 14 consists of two servomotors 21 and 22 which drive respective cranks 23 and 24 hinged in turn to respective connecting rods 25 and 26. The other ends are attached to the plinth 12 of the blade-holder unit 10.
All the cranks can be constructively represented by eccentric elements having the same function and that the two frame cranks were chosen as motor elements.
From the geometric point of view, the mechanism:
This mechanism is in a condition of dual kinematic singularity (referring to inverse motion) in a neighborhood of both the above-mentioned configurations.
This dual singularity is achieved by simultaneously aligning the first motor crank 23, 24 with the first connecting rod 25, 26 and the second motor crank 16 with the second connecting rod 17.
Z1—crank 23, 24 of the first link between the motor 21, 22 and the connecting rod 25, 26;
Z2—trajectory of the connecting rod 25, 26 of the first link;
Z3—trajectory of the first link between the hinge of the connecting rod 25, 26 and the blade-holder unit 10, and the hinge 20 of the lever 18;
Z4—trajectory of the first link between the hinge 20 of the lever 18 and the pivot 19 of this lever;
ZB1—trajectory of the second link between the pivot 19 of the lever 18 and the hinge between the crank 18 and the connecting rod 17;
ZB2—trajectory of the second link between the hinge of the crank 18 and connecting rod 17 and the hinge of the connecting rod 17 and the crank 16;
ZB3—trajectory of the second link between the hinge of the connecting rod 17 and the crank 16, and the shaft axis of the motor 15.
It should also be pointed out that the disclosed concept is independent of the geometric dimensions of the members or of the position of the frame kinematic pairs. It is evident that the amplification effect depends to some extent on these dimensions, and on the working space of the machine.
The blades of the machine according to the disclosure are moved by an articulated system with two degrees of freedom that presents evident kinematic non-linearity. The movement of the bending blades is characterized by well-defined bending trajectories. This is made possible and programmable by a special original inverse kinematic algorithm of the non-iterative type which, inserted in the numerical control or used as a pre-processor. This makes it possible to carry out well-defined trajectories with interpolated axes such as, for example, the classic circular interpolation.
In
The reference X1 in
In
The blade and the sheet metal behave like two conjugate profiles and the resulting trajectory is a sort of circle involute. By mathematically imposing the non-slipping constraint between the blade and the sheet metal, a bond is achieved between the two free coordinates which in fact define the trajectory.
The kinematic motion described leads to numerous advantages. The servomotors and the reduction units make it possible to achieve definitely higher levels of performance than those of a hydraulic system and also ensure constant delivered torque. This cannot be achieved with a hydraulic system that uses accumulators and thus necessarily has a pressure that slowly decreases during bending.
In addition, the quality of the semifinished part processed by the machine according to the disclosure is excellent and is achieved by means of a considerably quieter machine compared to previous machines and uses reduced quantities of oil for a much simpler hydraulic circuit.
The environmental impact of the new machine is completely different with respect to the known solutions, since it is less noisy and uses considerably less oil.
The disclosure is described above with reference to a preferred embodiment. It is nevertheless clear that the disclosure is susceptible to numerous variations within the framework of technical equivalents.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IT2004/000581 | 10/22/2004 | WO | 00 | 2/26/2008 |
Publishing Document | Publishing Date | Country | Kind |
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WO2006/043292 | 4/27/2006 | WO | A |
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7114360 | Ikeda | Oct 2006 | B2 |
Number | Date | Country |
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WO2004069444 | Aug 2004 | WO |
Number | Date | Country | |
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20080264135 A1 | Oct 2008 | US |