Press for forging metal items

Abstract

A press (1) for forging metal items, in particular, ingots, comprising - a movable crossbeam (3); - a plurality of hydraulic cylinders (2) adapted to move the movable crossbeam (3); - a first tank (21), adapted to contain oil; - a pumping system (4) adapted to send oil from the first tank (21) to the hydraulic cylinders (2), in particular to pressurize the hydraulic cylinders (2); - an energy recovery system comprising one or more hydraulic accumulators (5) adapted to receive and release oil, in particular pressurized oil, discharged from the hydraulic cylinders (2) during a step of decompressing the hydraulic cylinders (2) in which the oil passes from the forging pressure to a lower pressure; a first valve (7), adapted to control the oil flow from the hydraulic cylinders (2) to said one or more hydraulic accumulators (5).

Description

[0001] PRESS FOR FORGING METAL ITEMS

[0002] Field of the invention

[0003] The present invention relates to the field of presses for forging metal items, in particular for forging ingots.

[0004] Background art

[0005] Conventionally, a press for forging ingots comprises: a movable crossbeam; hydraulic cylinders (or main cylinders or forging cylinders) adapted to move the movable crossbeam towards the item to be forged; a tank containing oil; and a pumping system adapted to send oil from the tank to the hydraulic cylinders, so as to pressurize the hydraulic cylinders. An element, also called a “hammer,” adapted to penetrate the ingot shaping the same, is constrained to the movable crossbeam. The press further comprises return cylinders to move the movable crossbeam away from the forged item.

[0006] A conventional ingot forging process involves the following steps:

[0007] Gravity approach: descent by gravity of the movable crossbeam to reach the cycle start height.

[0008] Compression: the movable crossbeam is brought into contact with the ingot, and the pressure in the main cylinders is raised and begins to rise up to the set force.

[0009] Forging: penetration of the hammer into the ingot at the set force until the desired deformation is achieved.

[0010] Decompression: by means of a valve, in particular a forging valve, with very fast response times, the volume of oil between the main cylinders and the tank is decompressed.

[0011] Ascent: the movable crossbeam rises to the desired height by means of the return cylinders to allow the rotation or advancement of the ingot being processed by means of a manipulator.

[0012] The valves used in known forging presses are sized to discharge the entire decompression flow rate of the main cylinders and the pumping system.

[0013] In the ingot forging process, a considerable amount of energy is consumed by the pumping system to ensure the movement of the movable crossbeam according to a predetermined degree of performance. Due to the volumes involved (main cylinders + pipes), the compressibility of the fluid (conventionally, mineral oil) and the dynamism of the process (very fast cycles), the quantity of oil released during the step of decompressing the main cylinders is very high.

[0014] In fact, the decompression is managed in the hydraulic circuit by using fast response valves which, during the duration of the decompression, release all the necessary volume contained in the main cylinders and in the pipes to pass from the forging pressure to the discharge pressure and, in addition, the entire flow rate of the pumps is directed through the same valves. This involves considerable energy consumption. In particular, the pumping system consumes a lot of energy during the decompression step. More specifically, during the first valve opening moments, the pumping system is still affected by the pressure of the main cylinders and therefore it consumes a lot of energy without producing any useful work.

[0015] There is therefore a need to improve the energy efficiency of a forging press so as to at least partially reuse the energy currently wasted, in particular the energy resulting from the decompression of the main cylinders, which is currently wasted.

[0016] Summary of the invention

[0017] It is an object of the present invention to allow, at least in part, the recovery of the energy released during the decompression step of a forging process in which the oil passes from the forging pressure to a lower pressure, in particular so as to improve the energy efficiency of a forging press and more generally of the processes of a company operating in this sector.

[0018] In order to improve energy efficiency, it is another object of the invention to reduce the energy consumption of the pumping system, in particular during the decompression step, in particular of the main cylinders.

[0019] The present invention achieves at least one of such objects, and other objects which will become apparent in the light of the present description, by means of a press, according to claim 1 , for forging metal items, in particular ingots, comprising

[0020] - a movable crossbeam;

[0021] - a plurality of hydraulic cylinders adapted to move the movable crossbeam;

[0022] - a first tank, adapted to contain oil; - a pumping system adapted to send oil from the first tank to the hydraulic cylinders, in particular to pressurize the hydraulic cylinders;

[0023] - an energy recovery system comprising: one or more hydraulic accumulators adapted to receive and release oil, in particular pressurized oil, discharged from the hydraulic cylinders during a step of decompressing the hydraulic cylinders in which the oil passes from the forging pressure to a lower pressure; a valve (also referred to as a first valve for descriptive purposes), adapted to control the oil flow from the hydraulic cylinders to said one or more hydraulic accumulators. Said valve, or first valve, is in particular a very fast response valve.

[0024] The aforesaid hydraulic cylinders are, in particular, the main hydraulic cylinders (or main cylinders) which may also be referred to as forging hydraulic cylinders (or forging cylinders).

[0025] The invention also relates to a method for operating a press, according to claim 14, wherein the following steps are provided a) sending oil to the hydraulic cylinders, in particular to pressurize said hydraulic cylinders up to the forging pressure; b) discharging oil from the hydraulic cylinders and sending the discharged oil, which in particular is pressurized oil, to the one or more hydraulic accumulators; c) releasing oil, in particular pressurized oil, from said one or more hydraulic accumulators; in particular wherein, during part or at least part of step b), said first valve is open. More particularly, during the first part, or initial part, of step b) the first valve is open, and optionally during the remaining part of step b) the first valve is closed. Preferably, and advantageously, the oil at the higher pressure is sent to said one or more hydraulic accumulators.

[0026] Preferably, during step a), said first valve is closed and / or during step c) the first valve is closed.

[0027] Advantageously, a press according to the invention allows, at least in part, to recover the energy released during the decompression of the oil of the hydraulic cylinders (or main cylinders) and generally allows to save energy.

[0028] A study has been carried out which has highlighted the possibility of recovering, at least in part, the elastic energy associated with the pressurization of the oil to operate the hydraulic cylinders (main cylinders) and released during the decompression step. The study has also highlighted the possibility of recovering (or saving) the energy absorbed by the pumping system, which, during the same decompression step, continues to operate, consuming electric energy. In known presses, these amounts of energy are completely dissipated.

[0029] In particular, advantageously, a press according to the invention allows to recover the energy related to the decompression of the fluid, in particular oil, which passes from the forging pressure to a lower pressure, in particular to ambient pressure (elastic energy); and furthermore, it allows to recover (or save) energy which, in a conventional press, is consumed during the decompression step by the pumping system.

[0030] It is highlighted that it is particularly advantageous to recover energy from the decompression of the oil which passes from the forging pressure to a lower pressure (lower with respect to the forging pressure). In fact, the forging pressure is particularly high. In other words, the energy is recovered by the main hydraulic cylinders (or forging cylinders) which in particular are the hydraulic cylinders adapted to move the movable crossbeam towards the metal item to be forged. Advantageously, for example, the energy released during the decompression step can be converted into mechanical energy.

[0031] For example, in one embodiment, the energy released during the decompression step may be converted into mechanical energy to generate compressed air, which can be used for a variety of industrial purposes.

[0032] In another embodiment, the energy released during the decompression step may be converted into mechanical energy to generate in turn electric energy.

[0033] In another embodiment, the pressurized oil released from the one or more hydraulic accumulators may be reintroduced into the hydraulic circuit of the press, for example, it may be sent to the hydraulic cylinders for the pressurization thereof.

[0034] In the present description, “decompression step” or “decompressing” relates to the decompression of the oil in the main hydraulic cylinders, or in other terms to the decompression of the main hydraulic cylinders, in particular from the forging pressure to a lower pressure. Further features and advantages of the invention will become more apparent in light of the detailed description of exemplary but not exclusive embodiments.

[0035] The dependent claims describe particular embodiments of the invention.

[0036] Brief description of the Figures

[0037] The description of the invention refers to the accompanying drawings, which are provided by way of non-limiting example, in which:

[0038] Figure 1 diagrammatically shows some parts of a press according to the invention; Figure 1A diagrammatically shows some parts of a variant of a press according to the invention;

[0039] Figure 2 diagrammatically shows the hydraulic circuit of a press according to an embodiment of the invention;

[0040] Figure 3 diagrammatically shows the hydraulic circuit of a press according to another embodiment of the invention.

[0041] The same elements or components have the same reference numerals.

[0042] Description of exemplary embodiments of the invention

[0043] With reference to the Figures, exemplary embodiments of a press 1 (or forging press) for forging metal items, in particular ingots, are described.

[0044] In all embodiments, the press 1 comprises

[0045] - a movable crossbeam 3, which in particular is provided with an element 31 , or hammer, adapted to penetrate the metal item to shape it;

[0046] - a plurality of hydraulic cylinders 2 adapted to move the movable crossbeam 3, the hydraulic cylinders 2 being in particular adapted to exert a force on the movable crossbeam 3, in particular to forge a metal item;

[0047] - a tank 21 (or first tank 21 ), adapted to contain oil;

[0048] - a pumping system 4, in particular comprising one or more pumps, adapted to send oil from the first tank 21 to the hydraulic cylinders 2, in particular to pressurize the hydraulic cylinders 2, in particular to the forging pressure; and the press 1 further comprises, advantageously, an energy recovery system comprising one or more hydraulic accumulators 5 adapted to receive and release oil, in particular pressurized oil, discharged from the hydraulic cylinders 2 during a step of decompressing the hydraulic cylinders 2, wherein during the step of decompressing the hydraulic cylinders 2, the oil passes from the forging pressure to a lower pressure (or in other words the oil pressure passes from the forging pressure to a lower pressure); a valve 7 (also referred to as a first valve 7 for descriptive purposes), adapted to control the oil flow from the hydraulic cylinders 2 to said one or more hydraulic accumulators 5.

[0049] The aforesaid hydraulic cylinders 2, in particular, are the “main cylinders” or “forging cylinders”.

[0050] The aforesaid hydraulic cylinders 2, in particular, are arranged above the movable crossbeam 3.

[0051] The aforesaid hydraulic cylinders 2, in particular, are adapted to move the movable crossbeam downwards, towards the metal item to be forged.

[0052] The aforesaid hydraulic cylinders 2, in particular, are adapted to make the hammer 31 penetrate into the metal item to be forged, in particular at the set force, until the desired deformation is achieved.

[0053] The forging pressure of the oil is preferably greater than 200 bar, for example from 200 to 220 bar.

[0054] Preferably, the axes along which the pistons of the hydraulic cylinders 2 move are distinct from each other.

[0055] The press 1 , in particular, further comprises return cylinders 13, distinct from the hydraulic cylinders 2, to make the movable crossbeam 3 rise, i.e. , to move it away from the metal item which has been forged. The return cylinders 13, in particular, are arranged below the movable crossbeam 3. The return cylinders 13, in particular, are also hydraulic cylinders.

[0056] Note that it is particularly advantageous to recover energy from the decompression of the oil which is at the forging pressure (i.e., to recover energy from the decompression of the oil which is in the main hydraulic cylinders 2).

[0057] The forging pressure, which is the oil pressurization pressure in the hydraulic cylinders 2 to perform the forging, is greater than, for example, the oil pressure to operate the return cylinders 13.

[0058] In other words, the (main) hydraulic cylinders 2 are adapted to be pressurized to a greater pressure than the return cylinders 13. By way of explanation and not of limitation, in the variant diagrammatically shown in Figure 1 , each hydraulic cylinder 2 is substantially at a respective column 33 along which the movable crossbeam 3 can move vertically.

[0059] By way of explanation and not of limitation, in the variant diagrammatically shown in Figure 1 A, the hydraulic cylinders 2 are between the columns 33 along which the movable crossbeam 3 can move vertically, i.e., they are in an inner position with respect to the columns 33.

[0060] The press 1 , preferably, further comprises an additional valve 6 (also called second valve 6), adapted to control the oil flow from the hydraulic cylinders 2 to the first tank 21 , in particular during the decompression step. In particular, the valve 6 and the valve 7 are preferably distinct from each other. The press 1 is in particular configured so as to be able to send the oil exiting the second valve 6 to the first tank 21 . The valve 7 is in particular sized according to the decompression flow rate.

[0061] Optionally, the press 1 comprises a second tank 22, and the press 1 is configured so that the oil exiting the valve 6 can be sent to said second tank 22 and then to said first tank 21 .

[0062] The press 1 is, in particular, configured so as to send at least part of the oil discharged from the hydraulic cylinders 2, during the decompression step, to said one or more hydraulic accumulators 5.

[0063] The valve 7, in particular, is advantageously adapted to be used during the decompression step, in particular during the first moments of the decompression step, to convey the oil into the one or more hydraulic accumulators 5. In particular, after the pressure has fallen below the calibration of the one or more hydraulic accumulators 5, the valve 7 can be closed and the valve 6 can be opened.

[0064] Advantageously, the one or more hydraulic accumulators 5 are adapted to receive and contain the oil coming from the hydraulic cylinders 2, in particular during the decompression step. The press 1 is optionally configured so that the one or more hydraulic accumulators 5 are also adapted to receive and contain the oil coming from the pumping system 4, in particular during the opening of the valve 6, in particular during the pressurization of the hydraulic cylinders 2.

[0065] The one or more hydraulic accumulators 5 are advantageously adapted to transform the oil flow from impulsive (upstream of the one or more hydraulic accumulators 5) to continuous or constant (downstream of the one or more hydraulic accumulators 5) during the sequence of cycles. In this condition, it is possible to create an optimal regime condition to feed the components adapted to recover and convert energy.

[0066] With particular reference to Figures 2 and 3, in a first and second embodiments, the energy recovery system comprises a hydraulic motor 8, and the press 1 is configured to send the oil released by said one or more hydraulic accumulators 5 to said hydraulic motor 8.

[0067] The hydraulic motor 8, in particular, is downstream, in particular always downstream, of the one or more hydraulic accumulators 5.

[0068] Preferably, the press 1 is configured so that the oil coming from the hydraulic cylinders 2 exiting said first valve 7 is sent partly to said one or more hydraulic accumulators 5 and partly to the hydraulic motor 8.

[0069] The hydraulic motor 8 is preferably a variable displacement motor.

[0070] The hydraulic motor 8, in particular, is adapted to receive a constant or substantially constant oil flow coming from the one or more hydraulic accumulators 5 during the closing time of the valve 7, and an oil flow coming from the hydraulic cylinders 2 during the step of decompressing the cylinders 2 and from the pumping system 4, during the opening time of the valve 7.

[0071] In particular, in other words, the press 1 is preferably configured so that, for each decompression step, the hydraulic motor 8 can receive the oil coming from the one or more hydraulic accumulators 5, when the valve 7 is closed; and preferably so that the hydraulic motor 8 can receive the oil coming from the hydraulic cylinders 2 (during the decompression step) and from the pumping system 4, when the valve 7 is open.

[0072] In the first embodiment (Figure 2), the energy recovery system also comprises a compressor 9 adapted to generate compressed air, adapted to be powered by the energy supplied by the hydraulic motor 8. The compressor 9 is preferably provided with an electric motor 9a. The electric motor 9a is connected to said hydraulic motor 8, in particular so that the hydraulic motor 8 can supply energy to the electric motor 9a.

[0073] Preferably, the compressor 9 is a screw compressor and / or preferably said electric motor 9a is an asynchronous electric motor. In this embodiment, advantageously, the energy released during the decompression is converted into mechanical energy to generate compressed air.

[0074] Advantageously, the compressed air can be used directly. Compressed air has numerous uses in the steel industry and, currently, to be produced, special compressors are needed which consume electric energy to generate it.

[0075] In the second embodiment (Figure 3), the press 1 comprises an electric generator 9b connected to said hydraulic motor 8, in particular so that the hydraulic motor 8 can supply energy to the electric generator 9b. The electric generator 9b is preferably asynchronous, preferably at a fixed speed, preferably at about 1500 rpm. Preferably, a DC / AC inverter 10 is provided connected to said electric generator 9b. In this embodiment, advantageously, the energy released during the decompression is converted into mechanical energy to generate electric energy.

[0076] In all embodiments wherein the hydraulic motor 8 is provided, preferably, the press 1 is configured so as to prevent the oil from passing from the hydraulic motor 8 to said one or more hydraulic accumulators 5. Thereby, the energy recovered from the decompression of the oil can be optimally exploited. For example, the press 1 can be configured to operate the hydraulic motor 8, for example so that a movable part thereof can rotate only so as to prevent the oil from passing from the hydraulic motor 8 to said one or more hydraulic accumulators 5, for example so that said movable part can rotate only in one rotation direction; and / or a valve can be provided, preferably a unidirectional or non-return valve, adapted to prevent the oil from passing from the hydraulic motor 8 to said one or more hydraulic accumulators 5. Said unidirectional or non-return valve, in particular, can be arranged along the duct 18 serving to conduct the oil from the one or more hydraulic accumulators 5 to the hydraulic motor 8.

[0077] In all embodiments in which the hydraulic motor 8 is provided, preferably, the press 1 comprises a duct 11 along which there is a valve 12, preferably a unidirectional valve. The valve 12 allows the oil to be suctioned by the hydraulic motor 8, in particular by the tank 21 , in the case wherein the energy recovery system is not operating, thus avoiding the onset of cavitation.

[0078] The duct 11 , in particular, is downstream of the one or more hydraulic accumulators 5. The duct 11 , in particular, is upstream of the hydraulic motor 8.

[0079] The duct 11 , preferably, branches off from said duct 18.

[0080] In the case in which there are provided the duct 11 and the aforesaid valve that prevents the passage of oil from the hydraulic motor 8 to said one or more hydraulic accumulators 5, said valve can, for example, be upstream or downstream of said duct 11 .

[0081] In a third embodiment, the press 1 is configured so that the oil released by said one or more hydraulic accumulators 5 is sent to the hydraulic cylinders 2. In particular, valve 7 is adapted to control the oil flow from said one or more hydraulic accumulators 5 to said hydraulic cylinders 2.

[0082] The invention also relates to a method for operating a press 1 , wherein the following steps are provided: a) sending oil to the hydraulic cylinders 2 (i.e., to the main hydraulic cylinders, or forging hydraulic cylinders), in particular to pressurize the hydraulic cylinders 2, in particular up to the forging pressure; b) discharging oil from the hydraulic cylinders 2 and sending the discharged oil, which in particular is pressurized oil, to the one or more hydraulic accumulators 5; c) releasing oil, in particular pressurized oil, from said one or more hydraulic accumulators 5; in particular wherein, during part or at least part of step b), said first valve 7 is open. The valve 7 may be open during all or part of step b).

[0083] In particular, during the first part, or initial part, of step b) the first valve 7 is open, and preferably during the remaining part of step b) the first valve 7 is closed. Preferably, during step a), said first valve 7 is closed and / or during step c) the first valve 7 is closed.

[0084] During at least part of step b), said second valve 6 (if provided) is closed.

[0085] In particular, during step b), when the first valve 7 is open, the second valve 6 is closed, and when the first valve 7 is closed, the second valve 6 is open.

Claims

CLAIMS1. A press (1 ) for forging metal items, in particular ingots, comprising- a movable crossbeam (3);- a plurality of hydraulic cylinders (2) adapted to move the movable crossbeam (3);- a first tank (21 ), adapted to contain oil;- a pumping system (4) adapted to send oil from the first tank (21 ) to the hydraulic cylinders (2), in particular to pressurize the hydraulic cylinders (2);- an energy recovery system comprising one or more hydraulic accumulators (5) adapted to receive and release oil, in particular pressurized oil, discharged from the hydraulic cylinders (2) during a step of decompressing the hydraulic cylinders (2) in which the oil passes from the forging pressure to a lower pressure; a first valve (7), adapted to control the oil flow from the hydraulic cylinders (2) to said one or more hydraulic accumulators (5).

2. A press (1 ) according to claim 1 , wherein said energy recovery system comprises a hydraulic motor (8); and wherein the press (1 ) is configured to send the oil released from said one or more hydraulic accumulators (5) to said hydraulic motor (8).

3. A press (1 ) according to claim 2, configured so that oil coming from the hydraulic cylinders (2) exiting said first valve (7) is sent partly to said one or more hydraulic accumulators (5) and partly to the hydraulic motor (8).

4. A press (1 ) according to claim 2 or 3, configured so that, in particular for each decompression step, the hydraulic motor (8) can receive the oil coming from the one or more hydraulic accumulators (5), when the valve (7) is closed; and so that the hydraulic motor (8) can receive the oil coming from the hydraulic cylinders (2) and from the pumping system (4), when the first valve (7) is open.

5. A press (1 ) according to claim 2, 3 or 4, wherein said energy recovery system comprises a compressor (9) adapted to generate compressed air, adapted to be powered by the energy supplied by the hydraulic motor (8); preferably wherein the compressor (9) is provided with an electric motor (9a); wherein said electric motor (9a) is connected to said hydraulic motor (8), in particular so that the hydraulic motor (8) can supply energy to the electric motor (9a);preferably wherein said compressor (9) is a screw compressor and / or said electric motor (9a) is an asynchronous electric motor.

6. A press (1 ) according to claim 2, 3 or 4, comprising an electric generator (9b) connected to said hydraulic motor (8), in particular so that the hydraulic motor (8) can supply energy to the electric generator (9b); preferably wherein said electric generator (9b) is asynchronous, preferably at fixed speed; and / or preferably wherein the press (1 ) comprises a DC / AC inverter (10) connected to said electric generator (9b).

7. A press (1 ) according to any one of the preceding claims, comprising a duct (11 ) along which there is a valve (12), preferably a unidirectional valve, in particular to allow the suction of oil by the hydraulic motor (8) from the tank (21 ), in particular in the case where the energy recovery system is not operating, and thus avoid the onset of cavitation.

8. A press (1 ) according to any one of claims 2 to 7, configured so as to prevent the oil from passing from the hydraulic motor (8) to said one or more hydraulic accumulators (5); preferably wherein a valve is provided which is adapted to prevent the oil from passing from the hydraulic motor (8) to said one or more hydraulic accumulators (5).

9. A press (1 ) according to claim 1 , configured so that the oil released by said one or more hydraulic accumulators (5) is sent to the hydraulic cylinders (2); in particular wherein said first valve (7) is adapted to control the oil flow from said one or more hydraulic accumulators (5) to said hydraulic cylinders (2).

10. A press (1 ) according to any one of the preceding claims, comprising a second valve (6), adapted to control the oil flow from the hydraulic cylinders (2) to the first tank (21 ); in particular wherein said first valve (7) is distinct from said second valve (6); in particular wherein the press (1 ) is configured so that the oil exiting the second valve (6) can be sent to said first tank (21 ); optionally wherein the press (1 ) comprises a second tank (22), and the press (1 ) is configured so that the oil exiting the second valve (6) can be sent to said second tank (22) and then to said first tank (21 ).

11. A press (1 ) according to any one of the preceding claims, configured so that the one or more hydraulic accumulators (5) are adapted to receive the oil coming fromthe pumping system (4), in particular during the pressurization of the hydraulic cylinders (2).

12. A press (1 ) according to any one of the preceding claims, wherein said hydraulic cylinders (2) are adapted to move the movable crossbeam (3) towards a metal item to be forged; in particular, wherein said hydraulic cylinders (2) are arranged above the movable crossbeam (3).

13. A press (1 ) according to any one of the preceding claims, comprising a plurality of return cylinders (13) adapted to move the movable crossbeam (3) so that it moves away from a forged metal item; in particular wherein said return cylinders (13) are arranged below the movable crossbeam (3).

14. A method for operating a press (1 ) according to any one of the preceding claims, wherein there are provided the steps of a) sending oil to the hydraulic cylinders (2), in particular to pressurize the hydraulic cylinders (2) up to the forging pressure; b) discharging oil from the hydraulic cylinders (2) and sending the discharged oil, which in particular is pressurized oil, to the one or more hydraulic accumulators (5); c) releasing oil, in particular pressurized oil, from said one or more hydraulic accumulators (5); in particular wherein, during part or at least part of step b), said first valve (7) is open.

15. A method according to claim 14, wherein the press (1 ) comprises a second valve (6), adapted to control the oil flow from the hydraulic cylinders (2) to the first tank (21 ); in particular, wherein said first valve (7) is distinct from said second valve (6); in particular, wherein during part of step b), said second valve (6) is closed; in particular, wherein during step b), when the first valve (7) is open, the second valve (6) is closed, and when the first valve (7) is closed, the second valve (6) is open.

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