Circuit for the control of a hydraulic or oleodynamic press for treating components, in particular metallic components as well as press provided with such circuit

Abstract

The present invention relates to a circuit for the control or operation of a hydraulic or oleodynamic press for the treatment of objects including a main hydraulic or oleodynamic cylinder (80) for operating a mold holder slide (5) of the press and a blank holder hydraulic or oleodynamic cylinder (100) of said press.

Description

[0001] “CIRCUIT FOR THE CONTROL OF A HYDRAULIC OR OLEODYNAMIC PRESS FOR TREATING COMPONENTS, IN PARTICULAR METALLIC COMPONENTS AS WELL AS PRESS PROVIDED WITH SUCH CIRCUIT”

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to a hydraulic functional circuit for a press for processing components, in particular metal components as well as a press provided with such a circuit.

[0004] More specifically, the present invention relates to a press used in pressing operations, such as molding, shearing, drawing of metal objects, such as sheets or roughs or semi-finished products.

[0005] DESCRIPTION OF THE STATE OF THE ART

[0006] It is known to use machines, commonly known as presses and related tools commonly called molds, suitable for processing metal components, typically sheets or roughs or semi-finished products.

[0007] Typical processes consist, for example, of molding, shearing, drawing, etc.

[0008] The presses are typically vertically moved, controlled mechanically or by hydraulic actuators and essentially operate a mold.

[0009] Furthermore, inside the press or mold there is one or more elements called blank holders.

[0010] Presses also include pumps for conveying fluids and more specifically independent pumps dedicated to individual actuators. These configurations limit the working speeds to the flow rate that can be managed by the pump that controls the main cylinder, thus making these configurations expensive and not very widespread in general practice.

[0011] Moreover, operating machines such as presses demonstrate numerous risks if they are powered by operators.

[0012] The safety condition is generally ensured through the combined action of multiple hydraulic valves, appropriately interfaced with specific control systems such as electromechanical relay systems or electronic systems such as safety PLCs and related safety modules.

[0013] The presence of direction or interception valves obviously involves a loss of energy when the fluid passes between upstream and downstream of the valves themselves, introducing further dissipative effects within the process.

[0014] The Italian patent application no. 102009901788323 teaches a solution according to the state of the prior art.

[0015] OBJECTS OF THE INVENTION

[0016] One object of the present invention is to provide a new circuit for the control or actuation of a hydraulic or oleodynamic press as well as a new hydraulic or oleodynamic press capable of reducing the energy consumption required from the electricity grid thanks to the recovery of the energy generated at the blank holder.

[0017] Another object of the present invention is to provide a new circuit and a new press that is structured so as to be able to manage all the required uses even with a limited number of pumps, also having a drastic reduction in the sizing of the total displacement required.

[0018] Another object of the present invention is to provide a new circuit and a new press that allow to ensure high safety standards, also reducing to a minimum the presence of interception valves, thus limiting energy losses compared to known solutions.

[0019] In accordance with one aspect of the invention, a circuit according to claim 1 is provided.

[0020] In accordance with another aspect of the invention, a press according to claim 11 is provided.

[0021] The dependent claims refer to preferred and advantageous embodiments of the invention.

[0022] BRIEF DESCRIPTION OF THE FIGURES

[0023] Further advantages, objectives and features as well as embodiments of the present invention are defined in the claims and will be clarified hereinafter by means of the following description, in which reference is made to the attached drawing tables; in the drawings, corresponding or equivalent features and / or component parts of the present invention are identified by the same reference numbers. In particular, in the figures:

[0024] - figure 1 represents a simplified diagram of a press, mold and basic hydraulic circuit not according to the present invention;

[0025] - figure 2 shows a diagram of a press not according to the present invention, which is equipped with a system for recovering the energy required by the blank holder through a purely hydraulic system;

[0026] - figure 3 shows a typical diagram of a press not according to the present invention, which is equipped with a system for recovering the energy required by the blank holder through a hydraulic / electric system;

[0027] - figure 4 shows a first variant of the diagram which is the subject-matter of the present invention with independent fixed-displacement pumps operated by servomotors controlled by an electronic control system;

[0028] - figure 5 shows another embodiment of the circuit and press which is the subject-matter of the present invention with an additional pump for fast movements;

[0029] - figure 6 shows a further embodiment in accordance with the present invention with another additional pump for fast movements;

[0030] - figure 7 illustrates another embodiment subject-matter of the present invention provided with independent variable displacement pumps driven by servomotors controlled by an electronic control system;

[0031] - figure 8 shows another embodiment subject-matter of the present invention with two coupled variable displacement pumps.

[0032] In the attached drawings, identical parts or components are identified by the same reference numbers.

[0033] DESCRIPTION OF FIGURES OF SOLUTIONS NOT ACCORDING TO

[0034] THE PRESENT INVENTION

[0035] With reference first to figure 1 , a press not according to the present invention is illustrated, which is vertically moved, controlled mechanically or by hydraulic actuators and such as to operate a tool or mold 4, which has an upper half-mold or movable upper part 4.1 and connected in an integral manner to the movable part of the press, commonly called slide 5. The mold 4 also has a lower part consisting of a punch 4.2 and a blank holder 4.3, which part is normally fixed and is connected to a contrast element of the machine or fixed contrast plane, normally called table 3.

[0036] Furthermore, inside the press or mold there is one or more elements so- called blank holders 4.3 operated by a command generally generated by the compression of a fluid inside a hydraulic cylinder 100 located in the lower part of the press.

[0037] The function of the blank holder is well known in the state of the art and is of fundamental importance in molding, since, by superimposing on the deformation due to molding a further stretching of the sheet due to the friction generated between the surfaces of the blank holder and the sheet itself, it avoids the formation of defects better known as wrinkles due to the localized compression of the sheet itself inside the mold.

[0038] The function is generally performed by an element inside the mold called a blank holder ring 4.3 that transmits force to the object or sheet OB in contrast to the movement of the upper half-mold 4.1. The blank holder ring is supported by a series of columns called spark plugs 2.1 in turn supported by an element called a blank holder box 2 generally obtained inside the press. Finally, the box is connected to one or more actuators 100 controlled by fluid called blank holder pistons.

[0039] Since these pistons act against the downward movement of the slide they are also called passive effects.

[0040] Typically, the press also comprises at least one extractor 90, operated during the upward stroke of the slide, which ensures that the workpiece does not remain inserted in the press or in an upper die 4.1 of the same, but is correctly evacuated at the end of the process.

[0041] In the most common construction, the lower table is fixed while the slide pushes the blank holder arranged in the lower part of the press. Furthermore, this slide is typically operated by one or more hydraulic cylinders 80, in which the pressure and flow rate of the fluid that operate the cylinder are generated by hydraulic pump motors 6 connected to the cylinder and controlled by an appropriate hydraulic valve block 7.

[0042] In the most common form, the reaction force of the blank holder cylinder 100 is ensured by pressure control valves acting in the rear chamber of the cylinder or by pressure control valves acting both in the rear chamber 100.2 and in the possible front chamber 100.1 of the cylinder that operates the blank holder 2. The pressure in the rear chamber is generated by the flow generated by the thrust of the slide 5 against the blank holder via the die 4 and its components 4.1, 4.3. In other variants, depending on the response speed and precision required, the pressure can be generated actively by suitable systems consisting of pumps or pump s / accumul ator s .

[0043] The action of the blank holder, in the configuration of the molds described in figure 1, is of the purely passive type since the reaction force of the blank holder is opposite to the direction of motion of the blank holder itself.

[0044] In the art, there are known system solutions that allow the energy generated to be recovered through purely hydraulic systems (see figure 2), composed of combined motor / pump systems 6 in which there are two variable displacement pumps, at least one of which is of the reversible type (also called 2-quadrant) 6.4 and connected to the blank holder cylinder 100 or by mixed hydraulic / electric systems (see figure 3) in which there are two independent motor pumps 6 and 8 equipped with pumps, at least one of which is of the 2-quadrant type, being said to be both variable and fixed displacement, both connected to a motor 6.2, 8.2 controlled by electronic power supply systems 6.3, 8.3, capable of modulating the current and therefore the torque of the motor itself.

[0045] In this way, the pressure generated by the blank holder is recovered in the network by the control 8.3 or within the electrical power circuit of the machine, if the control systems 6.3 and 8.3 are powered by a single electrical power supply system.

[0046] In combined pump systems of the type in figure 2, electronically controlled variable displacement pumps are typically used, in which an external electronic control system allows the flow rate and pressure to be managed at the pump inlets. In these configurations, a first pump 6.1 is normally dedicated to the control of pressure and flow rate of the main cylinder, while a second pump 6.4 of the reversible or 2-quadrant type, mechanically connected to the first, is dedicated to the control of pressure and flow rate of the blank holder cylinder 100.

[0047] Under the action of the main cylinder 80, powered by the first pump 6.1, the mold acts on the blank holder 3 generating an output flow from the blank holder cylinder 100 whose pressure is modulated by the electronic control 6.3 of the pump 6.4. In this mode, the pressure acting on the mouth P of the pump 6.4 generates a torque that is transmitted via the connecting shaft directly from the pump 6.4 to the pump 6.1, relieving the electric motor 6.2 of the power required by the blank holder. This configuration, known in the art, requires having a dedicated pump for feeding the main cylinder and another for the blank holder cylinder. The molding speed of the press is therefore limited by the size of the pump 6.1.

[0048] In other embodiments known to the art, the two electronically controlled variable displacement pumps powered by a single electric motor are replaced by two servo pumps 6 and 8 with fixed or variable displacement, of which at least 8.1 is of the 2-quadrant type, controlled by independent servo motors 6.2, 8.2. Similarly to the previous case, each pump controls a single cylinder, but in this case, the pressure generated by the blank holder produces a net torque to the pump 8.1 which, through the servo motor 8.2, generates a current to the driver 8.3 which can be recovered directly from the network or can be fed into a common electrical power supply system for the two pumps if they are connected by a single power supply. Compared to the previous case, this configuration uses simpler and cheaper hydraulic elements, while the complexity of the control of power and flow pressure is delegated to the servo motors and related electronic controls 6.3, 8.3. In these cases, the known circuits allow in some cases also to recover other passive components such as the braking energy generated in the fast approach phase of the slide in the case in which the pump 6.1 is also of the 2-quadrant type. Also in this case, the molding speed of the press is therefore limited by the dimensions of the pump 6.1.

[0049] EMBODIMENTS OF THE INVENTION

[0050] The present invention relates to a circuit 1 for the control or actuation of a hydraulic or oleodynamic press for the treatment of objects, preferably metallic, typically sheets or roughs or semi-finished products, including a main hydraulic or oleodynamic cylinder 80 for actuating a mold-holder slide 5 of the press and a hydraulic or oleodynamic cylinder 100 for the blank holder of the press, which circuit comprises at least one first fixed-displacement pump 10.1 or variabledisplacement pump 10.7, 11.1 and at least one second fixed-displacement pump 30.1 or variable-displacement pump 30.7, 11.4 of the 4-quadrant type.

[0051] With reference to this aspect, a pump, whether fixed or variabledisplacement, with 4 quadrants is able to function both as a pump and as a hydraulic motor, processing flow to and from each of its mouths.

[0052] The circuit 1 according to the present invention further comprises at least one drive motor 10.2, 30.2, 11.2 of the at least one first 10.1, 10.7, 11.1 and of the at least one second 30.1, 30.7, 11.4 pump. Preferably, at least one motor is provided for the first pump and one for the second pump, or one motor for both.

[0053] Of course, the shaft of the motor can directly drive one or more respective pumps or means of transmission of motion from the shaft of the motor to the pump can be provided, for example to a second drive shaft of the latter.

[0054] Furthermore, the circuit 1 is configured in such a way that at least one mouth of the at least one first pump 10.1, 10.7, 11.1 is designed to be connected, respectively, to the front chamber 80.1 and rear chamber 80.2 of the main cylinder 80 for actuating the mold-holder slide 5 or in any case such circuit has ducts and appropriate valves designed to connect, according to work or operation schemes or steps controlled or established by an electronic control unit or component, at least one mouth of the at least one first pump 10.1, 10.7, 11.1, respectively, to the front chamber 80.1 and rear chamber 80.2 of the main cylinder 80 for actuating the moldholder slide 5 of a press.

[0055] In relation to this aspect, even if the representation in the figures of the first pump 10.1, 10.7, 11.1 is that of a 4-quadrant pump, it could also not be a 4-quadrant pump and operate differently. In this regard, see for example the solutions in figures 1-3.

[0056] In relation to this aspect, at least one mouth or mouths of the first pump 10.1, 107, 11.1 could also be connected in a stable or constant manner with the front chamber 80.1 and rear chamber 80.2 of the main cylinder 80 that drives the moldholder slide 5, without therefore providing for steps in which a different connection of these mouths is provided. Alternatively, this connection could be established only during specific operating steps of the press.

[0057] The terms “front” and “rear” in relation to the chambers of the main cylinder refer to the pressing zone of the press, that is, where the objects are arranged and pressed. More specifically, the front chamber is the one closest (with respect to the rear chamber) to the pressing zone, so that the supply of fluid or oil to it causes a retraction or movement of the cylinder piston away from the pressing zone, while the rear chamber is the one furthest from the pressing zone, so that the supply of fluid or oil to it causes an extension or approaching of the cylinder piston to the pressing zone and therefore pressing.

[0058] In addition to the above, the circuit 1 is configured in such a way that the mouths A and B of the at least one second pump 30.1, 30.7, 11.4 are designed to be connected, respectively, to the rear chamber 80.2 of the main cylinder 80 for actuating the mold-holder slide 5 of a press and to the rear chamber 100.2 of the blank holder cylinder 100 of the press or in any case such circuit has ducts la and appropriate valves designed to connect, according to work or operating schemes or steps controlled or established by an electronic control unit or component, the mouths A and B of the at least one second pump 30.1, 30.7, 11.4, one (A or B) to the rear chamber 80.2 of the main cylinder 80 for actuating the mold-holder slide 5 of a press and the other (B or A) to the rear chamber 100.2 of the blank holder cylinder 100 of the press.

[0059] Thanks to this arrangement, in specific steps of the pressing process, the second pump 30.1, 30.7, 11.4 either assists or contributes through a first mouth A or B together with the first pump 10.1, 10.7, 11.1 to supply fluid (for example water, oil, an emulsion, or other fluid) to the rear chamber 80.2 of the main cylinder 80, controlling with the other mouth B or A the pressure of the fluid exiting the chamber

[0060] 100.2 of the blank holder cylinder 100 of the press itself. Clearly, this is advantageous since the second pump 30.1, 30.7, 11.4 also receives fluid from the blank holder cylinder 100, so that thanks to the present invention it is possible to recover or use the reaction force of the blank holder cylinder 100 to operate the main cylinder 80 during specific steps of the pressing process.

[0061] In essence, the total flow rate entering the rear chamber of the main cylinder

[0062] 80.2 will therefore be given by the sum of the flow rate exiting from one port of the first pump 10.1, 10.7, 11.1 plus the flow rate exiting from one port of the second pump 30.1, 30.7, 11.4, thus allowing the size of the first pump 10.1,10.7, 11.1 to be drastically reduced.

[0063] Clearly, the terms “front” and “rear” in relation to the chambers of the blank holder cylinder also refer to the pressing zone of the press, that is, where the objects are arranged and pressed. More specifically, the front chamber is the one closest (with respect to the rear chamber) to the pressing zone, so that the supply of fluid or oil to it determines a retraction of the cylinder or, better, a moving away of the respective piston from the pressing zone, while the rear chamber is the one furthest from the pressing zone, so that the supply of fluid or oil to it determines an extension of the cylinder or, better, a moving closer of the respective piston from the pressing zone.

[0064] The motor 10.2, 30.2 comprises a first 10.2 and a second 30.2 servomotor (i.e. a motor having electronic torque and speed control) 10.2 and 30.2, powered by electronically controlled power supply means 10.3, 30.3 of the circuit. In this case, the at least one first 10.1, 10.7, and / or the at least one second 30.1, 30.7, pump are driven by the at least one low inertia servomotor 10.2 and 30.2.

[0065] The power supply means comprise a first electronically controlled power supply system 10.3 for powering the first servomotor 10.2, and a second electronically controlled power supply 30.3 for powering the second servomotor As regards in detail the second electronically controlled power supply system 30.3, it is advantageously designed to modulate the torque of the at least one servomotor 30.2 controlling the at least one second pump 30.1, 30.7, in such a way as to precisely control the pressure required for the fluid in the rear chamber 100.2 of the blank holder cylinder during a molding step.

[0066] With regard to this aspect, a servomotor is a motor / driver group in which the driver is able to control the direction and rotation speed of the motor as well as the torque delivered or drag. In this case, the motor, of the synchronous or asynchronous type, can be operated either as a motor or as a generator. Furthermore, the servomotor advantageously has limited inertia.

[0067] A servomotor can also be advantageously equipped with safe electronic control circuits that allow the motor to be stopped in controlled and repetitive times in a constant manner and with reliability levels compatible with the safety levels required by the legislation of the various countries of installation. Furthermore, such power supply and control systems 10.3, 30.3 are connected to each other at the electrical power level so that they can exchange the power supply and braking currents.

[0068] Advantageously, the circuit 1 or the press also includes an electronic control unit or component designed to appropriately control, depending on the work cycles, the various components of the circuit or the press, such as valves, pumps, motors or servomotors, etc.

[0069] If desired, the circuit 1 comprises at least one diverter or flow distributor or diversion valve 40.7 designed to intercept in a controlled manner the ducts la of the circuit itself so as to alternatively connect the first mouth A (or B) of the second pump 30.1 to the rear chamber 80.2 of the main cylinder for driving a mold-holder slide and to the rear chamber 90.2 of an extractor cylinder 90 and the second mouth B (or A) of the second pump 30.1 to the rear chamber 100.2 of the blank holder cylinder 100 and to the front chamber 90.1 of the extractor cylinder 90.

[0070] The circuit could then be equipped with at least one additional or auxiliary pump for fast movements 10.4 with 2 or 4 quadrants with fixed displacement. In this case, the at least one first fixed displacement pump 10.1 could be mechanically integral with the pump 10.4, for example they could be operated by means of the same shaft or rotation component, so that operating one pump automatically operates the second pump.

[0071] According to the variant under consideration, one or the delivery mouth P of the auxiliary pump 10.4 would be connected to a mouth B (according to the nonlimiting embodiment illustrated in the figures) of the at least one first pump 10.1, so that the displacement of the auxiliary pump 10.4 can be added to the displacement of the at least one first pump 10.1 in specific steps of the pressing process, for example only in the low pressure steps of controlled descent and ascent of the control cylinder of a mold-holder slide. With regard to this aspect, these additional pumps would be used only in the ascent steps of the slide, which are usually conducted at limited pressures, for example 20-80 bar, while the working or pressing steps are usually conducted at higher pressures, even 300 bar. As it will be understood, the additional pumps serve to increase the flow rate available only in these last steps in order to speed up the machine cycle without however having high displacements and therefore also high torques to the motors during the working steps.

[0072] In addition or as an alternative to this, one or at least one additional pump 30.4 with 2 or 4 quadrants with fixed displacement mechanically integral with the second pump 30.1 could be provided, so that the displacement of the auxiliary pump 30.4 can be added to the displacement of the at least one second pump 30.1 in specific steps of the pressing process, for example in the low pressure steps of the blank holder rise.

[0073] Subject-matter of the present invention is also a hydraulic or oleodynamic press 60 for the treatment of metal objects comprising, as indicated above, a tool or mold 4 with an upper half-mold or movable upper part 4.1 and connected in an integral manner to the movable part of the press, commonly called slide 5.

[0074] The mold 4 then has a lower part consisting of a punch 4.2 and a blank holder 4.3, the latter being connected to a contrast element of the machine or fixed contrast plane, normally called table 3.

[0075] The blank holder 4.3, preferably configured as a ring, is operated by a command generated by the compression of a fluid inside a hydraulic or oleodynamic cylinder 100 located in the lower part of the press.

[0076] The function of the blank holder is the one indicated above, that is to transmit force to the objects being processed OB in contrast to the movement of the upper half-mold 4.1.

[0077] The blank holder ring 4.3 can be supported by a series of columns known in jargon as spark plugs, which are in turn supported by an element called a blank holder box, generally located inside the press. Finally, the box is connected to one or more fluid-controlled actuators 100 called blank holder pistons.

[0078] The press also preferably includes at least one extractor cylinder 90, operated during the upward stroke of the slide 5, which ensures that the processed object does not remain inserted in the upper mold 4.1, but is correctly evacuated at the end of the process.

[0079] The press also includes at least one main hydraulic cylinder 80 for actuating the mold-holder slide 5 of the press.

[0080] Furthermore, the press includes a circuit as indicated above, in which at least one mouth of the at least one first pump 10.1, 10.7, 11.1 are connected, respectively, to the front chamber 80.1 and rear chamber 80.2 of the main cylinder 80, while the mouths A and B of the at least one second four-quadrant pump 30.1, 30.7, 11.4 are connected, respectively, to the rear chamber 80.2 of the main cylinder 80 for actuating the mold-holder slide 5 of a press and to the rear chamber 100.2 of the blank holder cylinder 100 of the press.

[0081] Advantageously, the displacements of the at least one first pump 10.1 and of the at least one second pump 30.1 are chosen so that the total displacement of these pumps is in relation to the displacement of the at least one second pump 30.1 as the area of the rear chamber of the main cylinder 80.2 is to the rear chamber of the blank holder cylinder 100.2 or in any case such ratios differ by ±25%. If a flow diverter or distributor 40.7 is provided, it would be advantageously designed to intercept in a controlled manner the ducts la of the circuit itself so as to alternatively connect the mouth A (or B) of the at least one second pump 30.1 to the rear chamber 80.2 of the main cylinder actuating the mold holder slide and to the rear chamber 90.2 of the extractor cylinder and the mouth B (or A) of the at least one second pump 30.1 to the rear chamber 100.2 of the blank-holder cylinder and to the front chamber 90.1 of the extractor cylinder.

[0082] With reference now to the specific non-limiting embodiments of the invention illustrated in the figures, figure 4 illustrates a circuit 1 which is the subject-matter of the present invention, which is basically constituted by a series of ducts la appropriately intercepted by respective valves as well as by at least two motor pump units 10 and 30 equipped with fixed flow rate pumps, of which at least the second 30.1 is of the 4 quadrant type.

[0083] In this case, the first pump 10.1 is connected via at least one mouth and via a suitable hydraulic distribution block and respective ducts intercepted by valves, respectively to the rear chamber 80.2 and front chamber 80.1 of the main cylinder 80 which operates the mold-holder slide 5 and the second pump 30.1 is connected alternatively via the two respective mouths A and B (or B and A) to the rear chamber 80.2 of the main cylinder 80 and to the rear chamber 100.2 of the blankholder cylinder.

[0084] If an extractor cylinder is provided, then the second pump 30.1 is also connected, via specific ducts la intercepted by at least one suitable diversion valve 40.7 to the front chambers 90.1 and rear chambers 90.2 of the extractor cylinder 90. In this case, the second pump 30.1 would be connected alternatively, acting on the diversion valve 40.7, to the cylinders 80 and 100 or to the extractor cylinder 90.

[0085] The size of the rear chamber of the extractor 90.2 can in this case be chosen, for example in such a way that the flow rate delivered through the mouth A of the pump 30.1 in the ascent phase, i.e. the opening of the press or the respective mold, is sufficient to ensure an exit speed of the extractor 90 or better of the respective rod greater than the retraction or removal speed of the pressing zone of the mold holder slide 5, ensuring contact between the rod of the extractor cylinder 90 and the pressed object OB.

[0086] In this step, the electronic control 30.3 of the motor 30.2 allows the pressure to be modulated in the rear chamber of the extractor 90.2, appropriately limiting its force.

[0087] Advantageously, the displacements of the pumps 10.1 and 30.1 are chosen so that the total displacement, the sum of the pumps 10.1 and 30.1, is in relation to the displacement of the pump 30.1 substantially as the area of the rear chamber of the main cylinder 80.2 is to the rear chamber of the blank holder cylinder 100.2 or in any case these ratios differ by ±25%.

[0088] It follows that in the case where the ratio of the areas of the rear chamber of the main cylinder 80.2 and the rear chamber of the blank holder cylinder 100.2 are in the ratio of 2 to 1, if the pumps 10.1 and 30.1 are driven at the same maximum rotation speed, the displacements of the two pumps 10.1 and 30.1 are advantageously identical and the molding speed of the press is given by the sum of the maximum flow rates delivered by the two individual pumps 10.1 and 30.1 rather than by the maximum flow rate of the sole pump connected to the main cylinder as in the cases of the pumps 6.1 of figures 1, 2 and 3 relating to solutions not in accordance with the present invention.

[0089] As already indicated, the circuit 1 or the press also includes at least one electronic control unit or component designed to appropriately control, depending on the work cycles, the various components of the circuit or the press, such as valves, pumps, motors, servomotors, etc.

[0090] The press 60 may also include an electronic control system 10.3 and 30.3 (which is part of or in communication with the general control unit or component) of the motors 10.2 and 30.2 that drive the pumps.

[0091] The electronic control system 30.3 may for example modulate the torque of the motor 30.2 exclusively to control the pressure at the mouth B of the pump 30.1, while the flow rate delivered to the mouth A is a consequence or function of the speed at which the main cylinder 80, through the mold-holder slide 5, presses on the blank holder 2, i.e. the slide 5 presses on an object OB that is clamped between the slide 5 and the blank holder 2 and therefore, indirectly, presses on the blank holder 2.

[0092] The pressure and / or flow rate from the pump 10.1 towards the rear chamber of the cylinder 80.2 can also be controlled by the relevant electronic control system 10.3, while the pressure at the rear chamber 90.2 of the extractor cylinder 90 depends on the force required for molding or pressing, and can however be limited by controlling the torque of the servomotor 10.2 by reading a sensor 20.10 of the electronic circuit and control 10.3. With reference to this, during the molding steps, it may be useful to limit in a controlled manner the force available to the actuator 90, for example to avoid damaging the object or piece during the operation step of the extractor 90.

[0093] In this case, one or more specific sensors may also be provided, for example pressure sensors 20.9 and 40.8, designed to detect the fluid pressure in specific sections of the circuit, so that by means of the values obtained from them, the electronic control system 10.3 and 30.3 could modulate the torque of the motors

[0094] 10.2 and 30.2 in such a way that it is possible to control the pressure in the rear chamber 80.2 of the main cylinder 80 by controlling the torque delivered by the motor 10.2 and / or the pressure in the rear chamber of the blank holder cylinder

[0095] 100.2 by controlling the torque delivered by the motor 30.2.

[0096] The total flow rate entering the rear chamber of the main cylinder 80.2 will thus be given by the sum of the flow rate exiting from port A of the pump 10.1 plus the flow rate exiting from port A of the pump 30.1, the latter being equal to that entering port B of the pump 30.1 itself except for the compressibility of the hydraulic fluid and the different pressures in general acting on the rear chambers of the main cylinder 80.2 and the rear chamber of the blank holder cylinder 100.2. Since the ratio between the areas of the rear chambers 80.2 and 100.2 of the two cylinders 80 and 100 and the displacements of the two pumps is fixed, it follows that the flow rates exiting from ports A are uniquely linked.

[0097] Advantageously, these motors 10.2 and 30.2 can be stopped in a very short time thanks to the low inertia through appropriate safety circuits integrated into the press.

[0098] In this embodiment, unlike configurations not according to the present invention, the flow rate to the main cylinder 80 is the sum of the individual flow rates delivered by the pumps 10.1 and 30.1, thus allowing the size of the pump 10.1 to be drastically reduced.

[0099] Furthermore, by also choosing an appropriate ratio between the areas of the rear chamber of the main cylinder 80.2 and the rear chamber of the blank-holder cylinder 100.2, optionally 2 to 1 or a value between 4 and 1 or between 4 and 3 / 2, it is possible to optimize the performance of the individual pumps 10.1 and 30.1, which for example in the case of an area ratio of 2 to 1 result in having the same displacement, while the displacement of the pump 10.1 which operates the main cylinder 10.1, results in being lower, possibly even half that of a similar single pump, acting on the main cylinder, capable of ensuring the same performance as a press made with circuits not according to the present invention, for example those illustrated in figures 2 and 3.

[0100] Furthermore, if there is a distributor or flow distributor or diversion valve 40.7 intercepting the ducts la of circuit 1, it is possible to independently control the raising of the blank holder 4.3 and the extraction of the object by means of the extractor cylinder 90 using only the pump 30.1. In fact, these steps can be performed one after the other.

[0101] As it will be understood, circuit 1 and press 60 can manage all the required uses with a limited number of pumps, also having a drastic reduction in the sizing of the total displacement required of the same.

[0102] Furthermore, thanks to the possible presence of servomotors 10.2, 30.2 and related control systems 10.3, 30.3, it is possible to guarantee the safety of the machine movement through safe stopping of the motor itself in very rapid and repetitive times.

[0103] Advantageously, the electronic control systems 10.3 and 30.3 are equipped with safe stopping systems for the motors and braking (see in particular the Machinery Directive 2006 / 42 / CE and subsequent, in particular the standard EN / IEC 60204-1 and subsequent the concepts of safety stopping SSI, SS2, SSE, etc.) such that the actuators present cannot be operated in an uncontrolled manner and that it is possible to perform the emergency stop in a safe and repetitive manner. The adoption of safe shutdown systems for the motors 10.2 and 30.2 through appropriate hardware and firmware devices within the electronic control systems 10.3 and 30.3 allows the replacement of the safety logic known in the art through shut-off valves, discharge valves or hydraulic monitored distributors within the circuit which, in addition to being expensive and complex to manage, have a resistance to crossing that leads to power dissipation.

[0104] The circuit and the press can then advantageously include safe shut-off valves 20.4, 20.5 and 40.4, 40.5 placed to shut off the various branches of the ducts la of the circuit 1, which would serve to avoid unwanted movements due to gravity, although their presence is reduced to a minimum, for example a number between two and ten, or if desired between two and eight.

[0105] The circuit described advantageously does not have directional control valves except for the distributor or diverter 40.7, thus it has minimal resistance to the passage of the fluid. There are overpressure control valves 20.1, 20.2, 20.3, 40.1, 40.2, 40.3, 50.1, 50.3 and safety shut-off valves against the gravity fall of the slide 20.4, 20.5 and of the blank holder 40.4, 40.5, but these valves are fewer in number than in known solutions.

[0106] The pressure and flow modulation is advantageously controlled only by modulating the torque of the motors 10.2 and 30.2 through appropriate control logics that reside in the electronic control systems 10.3 and 30.3 rather than through passive pressure control valves.

[0107] As it will be understood, the circuit configuration of the embodiment under examination allows both the flow rates of the pumps 10.1 and 30.1 to be added to the rear chamber of the main cylinder 80.2, while the second port B of the pump 30.1 is connected to the rear chamber of the blank holder cylinder 100.2.

[0108] This type of connection allows, during the pressing or actual work step, to use the pump 30.1 both to control the pressure of the rear chamber of the blank holder 100.2 and, through port B (or A), to simultaneously deliver flow rate to the rear chamber 80.2 of the main cylinder through port A (or B).

[0109] The press 60 can also be equipped with special safety valves 20.4, 20.5, which, during the rapid approach step of the slide 5 towards the object OB to be treated, ensure a safety function against the fall of the slide 5 due to gravity. More specifically, during this step, the valves 20.4, 20.5 are opened and the pump 10.1, driven by the motor 10.2, rotates so as to control the flow rate exiting the front chamber of the main cylinder 80.1.

[0110] Therefore, near the point where molding starts, the rotation of the motor 10.2 could advantageously be modulated so as to slow down the descent speed until the intervention of an appropriate balancing valve 20.8, of the fixed or proportional type.

[0111] As it will be understood, during a molding step the upper half-mold 4.1, constrained to the mold-holder slide 5, comes into contact with the object to be treated OB and the lower mold, consisting of a fixed part 4.2 on the mold-holder table 3 and the blank-holder ring 4.3, pushed by the upper half-mold 4.1, transmits the movement via appropriate components called candles 2.1 to the actual blankholder 2.

[0112] In this step, the two pumps 10.1 and 30.1 rotate in a direction useful for ensuring a supply flow to the rear chamber of the cylinder 80.2.

[0113] As mentioned, the circuit is advantageously defined so that the ratio between the sum of the flow rates of the two pumps 10.1 and 30.1 and the flow rate of the pump 30.1 is substantially equal to that defined between the areas of the rear chambers of the cylinders 80.2 and 100.2 or in any case such ratios differ by ±25%.

[0114] In this way, it is possible to have similar rotation speeds of the two motors 10.2 and 30.2, optimizing the exploitation of the available performance.

[0115] Preferably, the press 60 also comprises a suitable set of pressure transducers 20.9 and 40.8 connected to the rear chambers of the cylinders 80.2 and 100.2 controlling the slide and the blank holder and an electronic control 30.3, the latter being able, based on the detection of the pressure transducers 20.9 and 40.8, to control the servomotor 30.2 so as to modulate the torque so as to control the pressure at mouth B (the one for delivery to the rear chamber of the main cylinder 80) of the second pump 30.1.

[0116] In this configuration, the pressure acting on the port B is of the driving type, while the pressure acting on the port A is resistive.

[0117] Advantageously in this way, compared to other known configurations, the torque generated by the controlled pressure at the blank holder and the torque generated requested at the slide 5 are directly subtracted inside the four-quadrant pump 30.1, and only their resultant is transmitted to the motor 30.2.

[0118] In the case in which the pressure requested at the port A of the pump 30.1 is greater than that generated at the port B of the pump 30.1, the torque at the motor

[0119] 30.2 is positive, that is, the motor 30.2 must generate a driving torque and therefore the electronic control system 30.3 supplies current to the motor 30.2 by taking it directly from the network or from a common power supply to the electronic control

[0120] 10.3 connected to the network.

[0121] Vice versa, if the pressure required at port A is lower than that generated at port B of pump 30.1, the torque at motor 30.2 is negative, that is, motor 30.2 must generate a resistive torque or generator torque and therefore the electronic control system 30.3 controls the braking current supplied by motor 30.2, returning it to the network or to a power supply common to the electronic control 10.3 connected to the network.

[0122] If desired, at the end of the molding process, the two electronic control systems 10.3 and 30.3 can modulate the current to the motors 10.2 and 30.2 so as to cancel the pressure in the rear chambers 80.2 and 100.2 of the main control cylinder of the slide 5 and of the blank holder 4.3, respectively.

[0123] The rotation of the motor 10.2 is then reversed so as to perform the ascent stroke of the slide. In this step, the electronic control system 10.3 can modulate the speed of the motor 10.2 and consequently of the pump 10.1 so as to control the position and speed of the slide. Advantageously, during the ascent step of the slide, the extractor 90 is activated (if provided) through the action of the possible distributor or diverter 40.7 which allows the connections between the ports A and B of the pump 30.1 and the rear and front chambers of the extractor cylinder 90.2. In this step, the electronic control 30.3 of the motor 30.2 modulates a current capable of ensuring an adequate torque to guarantee the pressure of desired extraction and measured by the sensor 50.4.

[0124] According to this variant, once the extraction step has been performed, the possible distributor or diverter 40.7 is switched by connecting the ports A and B of the pump 30.1 with the rear chambers of the main cylinder 80 and the rear chamber of the cylinder 100.2, then the rotation of the motor 30.2 is reversed in such a way as to perform the upward stroke of the blank holder. In this step, the electronic control system 30.3 modulates the speed of the motor 30.2 and consequently of the pump 30.1 in order to control the position and speed of the blank holder 4.3.

[0125] In a variant of the present circuit, the two electronic control systems 10.3 and 30.3, instead of being directly connected to the grid, are connected by a single power supply (not shown in the figure), which in turn is connected to the electrical grid, so that the power supplied to and from the motors 10.2 and 30.2 are advantageously added or subtracted before connection to the electrical grid, with advantages in terms of process efficiency.

[0126] With reference now to the non-limiting embodiment of the present invention illustrated in figure 5, it is similar to that of figure 4, but the first pump 10.1 is connected to a first additional pump with 2 or 4 quadrants 10.4 having the delivery port P advantageously connected to the second port B of the pump 10.4 so that the displacement of the second pump 10.4 can be automatically added to the displacement of the pump 10.1 in the low pressure steps of fast approach and ascent of the slide. In this manner, the additional displacement from the pump 10.4 acts only in the low-pressure steps, limiting the torque required for the sizing of the motor 10.2 and power supply 10.3. According to the variant under consideration, one or the delivery port P of the auxiliary pump 10.4 would be connected to a port B of the at least one first pump 10.1, so that the displacement of the auxiliary pump 10.4 can be added to the displacement of the at least one first pump 10.1 in specific steps of the pressing process, for example in the low-pressure steps only of controlled descent and ascent of the control cylinder of a mold-holder slide.

[0127] In this regard, the torque required by the pumps is proportional to the total displacement involved and to the pressure at the pump mouth. In the ascent movements it can be useful to have a greater flow rate available to obtain a greater speed of the cylinders. With reference to this aspect, in order to avoid also having as a consequence a high torque required by the servomotors, it is possible to use additional pumps to be used only in the steps of rapid approach or ascent, which normally are at much lower pressures than the working pressures, generally, less than 50% of the latter.

[0128] In this case, the at least one first fixed displacement pump 10.1 could be mechanically integral with the additional pump 10.4, for example they could be operated by means of the same shaft or rotation component, so that by operating one pump the second pump is automatically operated.

[0129] With regard to the non-limiting embodiment of the present invention illustrated in figure 6, it is similar to that of figure 4, but the second pump 30.1 is connected to a second additional pump with 2 or 4 quadrants 30.4 having the delivery port P advantageously connected to the port B of the pump 30.1 so that the displacement of the second pump 30.4 can automatically add to the displacement of the pump 30.1 in the low pressure steps of the blank holder rise. In this way the additional displacement of the pump 30.4 acts only in the low pressure steps, limiting the torque required for the sizing of the motor 30.2 and power supply 30.3.

[0130] In a further non-limiting variant of the present invention shown in figure 7, at least the second pump 30.7 of the 4 quadrant type is of the variable displacement type.

[0131] In this case, both the displacement of the pump 30.7 and the torque of the motor 30.2 in rotation mode can be advantageously modulated so as to guarantee the desired pressure at the mouth B of the pump 30.7 and therefore at the chamber 100.2 of the blank-holder cylinder.

[0132] According to this variant, both the first pump 10.7 and the second 30.7 could have variable displacement, but this does not change the fact that only one 10.7 or 30.7 is with variable displacement and the other with fixed displacement.

[0133] Figure 8 then shows another variant of the circuit according to the present invention, in which circuit the first 10.1 and the second 30.1 pumps of the fixed displacement type are replaced by variable displacement pumps, of which at least one second 11.4 is of the 4-quadrant type and electronically controlled.

[0134] The first pump 11.1 in this case, is connected by means of an appropriate hydraulic distribution block, to the rear chamber 80.2 and front chamber 80.1 of the main cylinder that operates the mold-holder slide 5. The second pump 11.4 is advantageously connected alternatively, by means of appropriate ducts la of the circuit, through at least one mouth to the rear chamber 80.2 of the main cylinder 80 and to the rear chamber 100.2 of the blank-holder cylinder 100.

[0135] This configuration allows, as also described previously, to add both the flow rates of the pumps 11.1 and 11.4 to the rear chamber of the main cylinder 80.2, while the mouth B of the pump 11.4 is connected to the rear chamber of the blankholder cylinder 100.2.

[0136] In this case, the two pumps 11.1 and 11.4 are mechanically connected to a single motor.

[0137] The flow rate and pressure of the electronically controlled 4-quadrant pump 11.4 are controlled via the electronic displacement control of the pump itself 11.7.

[0138] During the actual working step, the pump 11.4 can appropriately modulate the pressure of the rear chamber of the blank holder 110.2 via the port B (or A) which supplies flow rate to the rear chamber of the main cylinder via the port A (or B).

[0139] In this case, the electronic control 11.7 can be used to modulate the pressure via the displacement control on board the pump 11.4 exclusively to control the pressure at mouth B, while the flow rate delivered to mouth A is a consequence of the speed at which the main cylinder 80, through the mold holder slide 5, presses on the blank holder 2.

[0140] The flow rate exiting the pump 11.1 via mouth A is controlled by the relative electronic control system 11.7 which regulates the displacement of the pump itself, while the pressure at the rear chamber of the main cylinder 80.2 depends on the force required for molding.

[0141] Also in this case, the total flow rate entering the rear chamber of the main cylinder 80.2 will therefore be given by the sum of the flow rate exiting the pump 11.1 plus the flow rate exiting the port A of the pump 11.4, the latter equal to that entering the port B of the pump itself except for the compressibility of the hydraulic fluid and the different pressures in general acting on the rear chambers of the main cylinder 80.2 and the rear chamber of the blank holder cylinder 100.2. Since the ratio between the areas of the rear chambers of the two cylinders is fixed, the rotation speed is single, it results that the flow rates exiting the chamber 80.2 of the main cylinder are uniquely linked to the displacements of the two pumps.

[0142] As in the previous case, the displacements of pumps 11.1 and 11.4 are chosen so that the total displacement, sum of pumps 11.1 and 11.4, is in relation to the displacement of pump 11.4 approximately as the area of the rear chamber of the main cylinder 80.2 is to the rear chamber of the blank holder cylinder 100.2 or in any case these ratios differ by ±25%.

[0143] It follows that, for example, in the case in which the ratio of the areas of the rear chamber of the blank holder cylinder and the rear chamber of the blank holder cylinder are in a ratio of 2 to 1, being mechanically connected to each other, the pumps also have the same rotation speed and therefore the displacements of the two pumps are advantageously identical or in any case related as desired based on the ratio between the areas established.

[0144] The pump 11.4 can be connected via an appropriate deviation valve 40.7 to the front and rear chambers of the extractor cylinder 90.2. The size of the rear chamber of the extractor 90.2 can in this case be chosen so that the flow rate delivered via the mouth A of the pump 11.4 in the ascent phase is sufficient to guarantee an exit speed of the extractor greater than the speed of the mold holder slide, ensuring contact between the extractor tool and the piece. At this stage the electronic control 11.7 of the pump displacement 11.4 can be pre-set so as to allow the pressure in the rear chamber of the extractor to be modulated, appropriately limiting its force when required.

[0145] Similarly to the previous cases, in the rapid approach step, safety valves 20.4, 20.5 are provided against fall by gravity, which are opened, while the displacement of the pump 11.1 is controlled so as to modulate the descent speed of the main cylinder 80 via the output flow rate from the front chamber 80.1.

[0146] During the molding step, the upper half-mold 4.1, constrained to the moldholder slide 5, comes into contact with the obj ect OB and the lower mold, consisting of a fixed part 4.2 on the mold-holder table 3 and the blank-holder ring 4.3, the latter, pushed by the upper half-mold 4.1, transmits the movement via appropriate spacers called candles 2.1 to the actual blank-holder 2.

[0147] In this steps, the two pumps 11.1 and 11.4 deliver a flow rate to the rear chamber 80.2 of the cylinder 80 controlling the slide 5.

[0148] Circuit 1 is advantageously defined so that the ratio between the sum of the maximum displacements of the two pumps 11.1 and 11.4 and the maximum displacement of the pump 11.4 is equal to that defined between the areas of the rear chambers of the cylinders 80.2 and 100.2 or in any case such ratios differ by ± 25.

[0149] In this way it is possible to have a similar maximum displacement of the two pumps 11.1 and 11.4, optimizing the exploitation of the available performance.

[0150] The pump 11.4 has an incoming flow rate from the rear chamber of the blank holder cylinder 100.2 to the port B (or A) and an outgoing flow rate from the port A (or B) towards the rear chamber of the main control cylinder of the slide 80.2.

[0151] In this variant, sets of pressure transducers 20.9 and 40.8 can also be provided, connected to the rear chambers 80.2, 100.2 of the control cylinders of the slide and the blank holder cylinder, so that the electronic control of the displacement 11.7, depending on the values detected by these transducers, is able to modulate the pressure at the port B of the pump 11.4.

[0152] In this configuration, the pressure acting on the mouth B is of the driving type, while the pressure acting on the mouth A is resistive. Advantageously, the torque generated by the pressure in the chamber 100.2 and the torque generated by the pressure in the chamber 80.2 are subtracted inside the four-quadrant pump 11.4, and only their resultant is transmitted to the motor 11.2 via the common shaft with the first pump 11.1.

[0153] If desired, at the end of the molding process, the electronic displacement control system 11.7 modulates the displacement of the pumps 11.1 and 11.4 in such a way as to cancel the pressure in the rear chambers 80.2 and 100.2 of the main control cylinder of the slide and blank holder respectively. Therefore, the displacement of the pump 11.1 can be modulated in such a way as to perform the upward stroke of the slide. At this stage, the electronic control system 11.7 can modulate the displacement of the pump 11.1 in order to control the position and speed of the slide.

[0154] During the ascent step of the slide, the extractor 90 can be activated by means of the action of the possible distributor or diverter 40.7 which allows the connection of the ports A and B of the pump 11.4 with the rear and front chambers of the extractor cylinder 90.2. In this step, the electronic control 11.7 of the displacement of the pump 11.4 can modulate the pressure measured by the sensor 50.4 in order to guarantee the desired extraction pressure force.

[0155] Once the extraction step has been carried out, the distributor or diverter 40.7 can be switched by connecting the ports A and B of the pump 11.4 with the rear chambers of the main cylinder and the rear chamber of the blank holder cylinder 100, then the displacement of the pump 11.4 is modulated in such a way as to perform the ascent stroke of the blank holder 4.3. At this step, the electronic control system 11.7 modulates the displacement of the pump 11.4 in order to control the position and speed of the blank holder.

[0156] Similarly to the previous cases, the circuit described in figures 7 and 8, advantageously does not have directional control valves except for the distributor or diverter 40.7, therefore it presents a minimum resistance to the passage of the fluid. Advantageously, there are minimum valves for overpressure controlling

[0157] 20.1, 20.2, 20.3, 40.1, 40.2, 40.3, 50.1, 50.3 and safe interception against the fall by gravity of the slide 20.4, 20.5 and of the blank holder 40.4, 40.5.

[0158] Preferably, the pressure and flow modulations are advantageously controlled only by modulating the displacement of the pumps 11.1 and 11.4 through appropriate control logics that reside in the electronic control system 11.7 of the displacement rather than through passive pressure control valves.

[0159] The motor 11.2 can be of the type that can be powered directly from the grid, or, advantageously, the power supply and control system 11.3, of the motor

[0160] 11.2, when present, can be equipped with a safe motor stop and braking system such that the actuators present cannot be activated in an uncontrolled manner and that it is possible to perform the emergency stop in a safe and repetitive manner.

[0161] The adoption of safe stop systems of the servomotor 11.2 through appropriate hardware and firmware devices within the electronic power and control system 11.3, allows to replace the safety logic known in the art through interception valves, discharge valves or hydraulic monitored distributors within the circuit which, in addition to being expensive and complex to manage, present a resistance to crossing that leads to a non-negligible power dissipation.

[0162] It will therefore be understood that the circuit and the press according to the present invention are structured so as to be able to manage all the required uses even with a limited number of pumps, also having a drastic reduction in the sizing of the total displacement required.

[0163] Furthermore, it is reiterated that the present invention allows to obtain high safety standards, also by reducing to a minimum the presence of interception valves, thus limiting energy losses compared to known solutions.

Claims

CLAIMS1. Circuit for the control or operation of a hydraulic or oleodynamic press for the treatment of objects including a main hydraulic or oleodynamic cylinder (80) for operating a mold holder slide (5) of the press and a blank holder hydraulic or oleodynamic cylinder (100) of said press, said circuit comprising at least one first pump with fixed (10.1) or variable (10.7, 11.1) displacement and at least one second pump with fixed (30.1) or variable (30.7, 11.4) displacement, at least one drive motor (10.2, 30.2 , 11.2) of said at least one first (10.1, 10.7, 11.1) and of at least one second (30.1, 30.7, 11.4) pump, at least one electronic control unit or component, said circuit also comprising ducts (la) and valves designed to connect, according to work or operation schemes or steps controlled or established by said electronic control unit or component, at least one mouth of said at least one first pump (10.1, 10.7, 11.1) to the front (80.1) and rear (80.2) chamber of the main cylinder for operating the mold holder slide of a press, characterized in that said at least one second pump with fixed (30.1) or variable (30.7, 11.4) displacement is of the 4-quadrant type and in that said circuit has ducts (la) and valves designed to connect, according to work or operation schemes or steps controlled or established by said electronic control unit or component, the first mouth (A or B) and the second mouth (B or A) of said at least one second pump (30.1, 30.7, 11.4), respectively, to the rear chamber (80.2) of the main cylinder (80) for operating the mold holder slide (5) of a press and to the rear chamber (100.2) of the blank holder cylinder (100) of the press, so that said at least one second pump (30.1, 30.7, 11.4) assists or contributes by means of a respective mouth (A or B) together with the first pump (10.1, 10.7, 11.1) to supply fluid to the rear chamber (80.2) of the main cylinder (80) of a press, controlling with the other mouth (B or A) the pressure of the fluid exiting the chamber (100.2) of the blank holder cylinder (100).

2. Circuit according to claim 1, wherein said at least one motor comprises at least one first (10.2) and at least one second (30.2) servomotor both powered by electronically controlled power supply means (10.3, 30.3) of said circuit, said at least one first pump (10.1, 10.7) being driven by said at least one first servomotor(10.2), whereas said at least one second pump (30.1, 30.7) is driven by said at least one second servomotor (30.2), said electronically controlled power supply means comprising a first electronically controlled power supply system (10.3) for powering the first servomotor (10.2), and a second electronically controlled power supply system(30.3) for powering the second servomotor (10.3).

3. Circuit according to claim 2, characterized in that said electronically controlled power supply means (10.3, 30.3) are connected to a single power supply connected to the electricity grid, in such a way that the powers delivered to and from the servomotors (10.2, 30.2) are added or subtracted before connecting to the electricity grid.

4. Circuit according to claim 2, wherein said electronically controlled power supply means (10.3, 30.3) are powered directly by the electricity grid and wherein said second electronically controlled power supply system (30.3) is suitable for recovering towards the grid the power generated by the respective servomotor (30.2).

5. Circuit according to claim 2 or 3 or 4, wherein said second electronically controlled power supply system (30.3) is designed to modulate the torque of said at least one second servomotor (30.2) controlling said at least one second pump (30.1, 30.7) in such a way as to precisely control the pressure required to the fluid in the rear chamber (1002) of the blank holder cylinder during a molding step.

6. Circuit according to any one of the preceding claims, wherein said at least one first pump (11.1) and said at least one second pump (11.4) are mechanically integral with each other, said circuit also comprising an electronic control system (11.7) designed to modulate the displacement of said at least one second pump (11.7) in such a way as to precisely control the pressure required to the fluid in the rear chamber (100.2) of the blank holder cylinder during a molding step.

7. Circuit according to any one of the preceding claims, wherein said motors (10.1, 30.1, 11.2) and related control systems (10.3, 30.3, 11.3) are equipped with a safe braking and stopping system.

8. Circuit according to any one of the previous claims, comprising at least one flow rate diverter or distributor or diversion valve (40.7) designed to intercept, in a manner controlled by said electronic control unit or component, the ducts (la) of the circuit, so as to connect alternatively the first mouth (A or B) of said at least one second pump (30.1, 30.7, 11.4) to the rear chamber (80.2) of the main cylinder for operating a mold holder slide and to the rear chamber (90.2) of an extractor cylinder and the second mouth (B or A) of said at least one second pump (30.1, 30.7, 11.4) to the rear chamber (100.2) of the blank holder cylinder and to the front chamber(90.1) of the extractor cylinder.

9. Circuit according to any one of the preceding claims, comprising at least one additional pump (30.4) of the 2 or 4 quadrants-type and wherein said at least one first pump (30.1) is mechanically integral with said additional pump (30.4), the delivering mouth (P) of said at least one additional pump (30.4) being connected with a mouth (B) of said at least one first pump (30.1), so that the displacement of the additional pump (30.4) is added to the displacement of said at least one first pump (10.1) only in the low pressure steps while the extractor goes down or of the blank holder cylinder goes up.

10. Circuit according to any one of the preceding claims, wherein said at least one second pump (30.7) has variable displacement and wherein both the displacement of said at least one second pump (30.7) and the torque of said motor(30.2) in the rotation regime are modulated so as to guarantee the desired pressure to the second mouth (B) of said second pump (30.7) and thus to the rear chamber(100.2) of the blank holder cylinder.

11. Hydraulic press for the treatment of metal objects including a mold holder slide (5), a blank holder (2) as well as a main hydraulic or oleodynamic cylinder (80) for operating said slide (5), a blank holder hydraulic or oleodynamic cylinder (100) and a circuit according to any one of the preceding claims, wherein the mouths (A and B) of said at least one first pump (10.1, 10.7, 11.1) are connected, respectively, to the front (80.1) and rear (80.2) chamber of said main cylinder (80), whereas the mouths (A and B) of said at least one second pump (30.1, 30.7, 11.4)are connected, respectively, to the rear chamber (80.2) of the main cylinder (80) for operating the mold holder slide (5) of the press and to the rear chamber (100.2) of the blank holder cylinder (100) of the press, so that at least one second pump (30.1, 30.7, 11.4) assists or contributes together with the first pump (10.1, 10.7, 11.1) to supply fluid to the rear chamber (80.2) of the main cylinder (80) of the press.

12. Press according to claim 11, wherein the displacements of said at least one first pump (10.1, 10.7,1 1.1) and of said at least one second pump (30.1, 30.7, 11.4) are such that the total displacement of said pumps is in ratio to the displacement of said at least one second pump (30.1, 30.7, 11.4) as the area of the rear chamber of the main cylinder (80.2) is in ratio to the rear chamber of the blank holder cylinder (100.2) or in any case these ratios differ by ± 25%.

13. Press according to claim 11 or 12, comprising at least one extractor cylinder (90) designed to ensure that a worked object does not remain inserted in the press(4.1), but is correctly extracted at the end of the process, said press also comprising a flow rate diverter or distributor (40.7) designed to intercept, in a manner controlled by said electronic control unit or component, the ducts (la) of said circuit, so as to connect alternatively the first mouth (A) of said at least one second pump (30.1, 30.7, 11.4 ) to the rear chamber (80.2) of the main cylinder for operating the mold holder slide and to the rear chamber (90.2) of the extractor cylinder (90) and the second mouth (B) of said at least one second pump (30.1) to the rear chamber (100.2) of the blank holder cylinder and to the front chamber(90.1) of the extractor cylinder (90).

14. Pressing process by means of a press according to claim 11, 12 or 13, wherein said main cylinder (80) is operated, during specific steps, by the fluid supplied both by said at least one first pump (10.1, 10.7, 11.1) and by said at least one second pump (30.1, 30.7, 11.4).

15. Process according to claim 14 with a press according to claim 13, wherein the size of the rear chamber of the extractor (90.2) is such that the flow rate delivered through the first mouth (A) of said second pump (30.1, 30.7, 11.4 ) in the opening step of the press is sufficient to ensure a speed of extension of the stem ofthe extractor cylinder (90) greater than the speed of retraction or removal of the pressing zone of the mold holder slide (5), ensuring contact between the stem of the extractor cylinder (90) and pressed object (OB).

16. Process according to claim 14 or 15, wherein said at least one electronic control unit or a respective component (30.3, 11.7) modulates the torque of said at least one motor (30.2) or the displacement of said at least one second pump (11.4) to control the pressure at the second mouth (B) of the second pump (30.1, 30.7, 11.4), whereas the flow rate delivered to the first mouth (A) of the second pump (30.1, 30.7, 11.4) is a consequence or function of the speed at which the main cylinder (80), by means of the mold holder slide (5) presses on the blank holder (2).

17. Process according to claim 14 or 15 or 16, wherein the pressure and / or flow rate of the first pump (10.1, 10.7, 11.1) towards the rear chamber (80.2) of the main cylinder (80) is controlled by said at least one electronic control unit or component (11.7) or by a respective component (10.3), whereas the pressure at the rear chamber (90.2) of the extractor cylinder (90.2) depends on the force required for molding or pressing.

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