Hydraulic press

Abstract

The present invention concerns the mechanical engineering sector. More specifically, the invention is relative to a hydraulic press (10) with energy recovery comprising: at least one press cylinder (1); a first hydraulic pump (P1 ); a first electric motor (M1 ); an oil tank (2); a first hydraulic circuit in which said oil is adapted to circulate; a first electric circuit; safety valves (4) for said first hydraulic circuit. Said first hydraulic pump (P1) is of the type adapted to function both as an operating machine and as a prime mover; said first electric motor (M1) is of the brushless type, adapted to act both as an operating machine and as a prime mover. Said hydraulic press (10) comprises a first driver (5) operatively connected at least to said first electric motor (M1) in order to drive said first electric motor (M1) and to manage the electric energy flows between them in both directions.

Description

[0001] HYDRAULIC PRESS

[0002] Technical field of application

[0003] The present invention concerns the mechanical engineering sector. More specifically, the invention is relative to a hydraulic press with energy recovery.

[0004] Prior art

[0005] Hydraulic presses are mechanical devices that exploit the flow of a fluid (generally hydraulic oil) to develop a force, used to compress different kinds of materials so as to shape them in a mould.

[0006] Traditional hydraulic presses comprise:

[0007] - a press cylinder with double-acting hydraulic piston at one end of which a pressing plate is associated for pressing the materials to be processed;

[0008] - a hydraulic pump;

[0009] - a motor, generally electric;

[0010] - an oil tank;

[0011] - a hydraulic circuit in which said oil is adapted to circulate;

[0012] - an electric circuit;

[0013] - a two-way valve, positioned along said hydraulic circuit, adapted to direct the pressurized oil to cause downward or upward movement of the hydraulic piston;

[0014] - safety valves for said hydraulic circuit.

[0015] The movement imparted to the pressing plate can be schematized in a rapid downstroke which exploits the falling of the hydraulic piston by gravity, a phase of slowing down the descent, a work and thrust phase caused by compression of the oil by the hydraulic pump driven by the electric motor, and an upstroke phase in which the direction of the oil flow in compression is inverted.

[0016] Possible variations of the hydraulic presses comprise the use of a sheet clamping assembly, intended to determine a counterthrust to support the work phase of the press cylinder.

[0017] Traditional hydraulic presses have some limits and drawbacks: the motor is always on: even when not moving, the press consumes 30% of the installed power, generating heat for movement of the oil; during the downstroke phases of the press cylinder hydraulic piston, its descent speed is controlled by proportional valves which also generate heat, hence the need to install an air / oil or water / oil heat exchanger, to cool the oil circulating in the hydraulic circuit; during the work and thrust phase of the hydraulic piston, all the maximum power of the electric motor installed is used, taking it from the electric mains, with considerable energy consumption; if the work cycle comprises the use of a sheet clamping assembly, the counter pressure of the sheet clamper must be created by means of proportional valves that generate further heat; the fact that the motor is always on and the fact that a heat exchanger is always active make the traditional hydraulic presses very noisy. Presentation of the invention

[0018] The invention aims to overcome these limits, providing an energy saving continuous cycle hydraulic press that does not generate heat and has a low noise level.

[0019] Said objects are achieved with a hydraulic press comprising:

[0020] - at least one press cylinder;

[0021] - a first hydraulic pump;

[0022] - a first electric motor;

[0023] - an oil tank;

[0024] - a first hydraulic circuit in which said oil circulates;

[0025] - a first electric circuit;

[0026] - safety valves for said first hydraulic circuit, characterized in that:

[0027] - said first hydraulic pump is of the type adapted to function both as an operating machine and as a prime mover;

[0028] - said first electric motor is of the brushless type, adapted to act both as operating machine and as prime mover;

[0029] - said hydraulic press comprises a first driver operatively connected at least to said first motor in order to drive said first motor and manage the electric energy flows between them in both directions.

[0030] In a possible variation, said hydraulic press comprises:

[0031] - a sheet clamping cylinder;

[0032] - a second hydraulic pump of the type adapted to function both as an operating machine and as a prime mover; - a second electric motor of brushless type, adapted to act both as an operating machine and as a prime mover;

[0033] - a second hydraulic circuit in which said oil circulates;

[0034] - a second electric circuit;

[0035] - safety valves for said second hydraulic circuit;

[0036] - a second driver adapted to electronically control said second electric motor; where said second driver is operatively connected at least to said second motor and to said first driver, in order to drive said second motor and manage the electric energy flows between them in both directions.

[0037] Advantageously, said first hydraulic pump and said second hydraulic pump are four-quadrant pumps.

[0038] In a preferred embodiment, said hydraulic press comprises an electric energy rechargeable battery, where said first driver is operatively connected to said rechargeable battery in order to manage the electric energy flows between them in both directions, and said rechargeable battery is operatively connectable also to external utilities, as well as to said hydraulic press to manage the power supply thereof.

[0039] In particular, said first electric circuit comprises a first rectifier interposed between said first driver and said rechargeable battery.

[0040] Furthermore, said second driver is operatively connected to said rechargeable battery in order to manage the electric energy flows between hydraulic press and rechargeable battery in both directions. In particular, said second electric circuit comprises a second rectifier interposed between said second driver and said rechargeable battery.

[0041] The hydraulic press according to the invention has numerous advantages.

[0042] If the hydraulic press is not moving, said first electric motor is off, the oil does not circulate in the circuit, no heat is generated and no electric energy is dissipated.

[0043] During the downstroke of the press cylinder, the speed is controlled by means of said first pump, which in this phase acts as a prime mover and, in turn, causes said first electric motor to rotate, generating electric current.

[0044] During the work phase only the required power is used, resulting in significant energy saving.

[0045] The presence of a rechargeable battery allows surplus energy generated by the motor to be stored, to be re-used inside the press or if necessary, conveyed to the power supply of utilities external to the press.

[0046] In short, the hydraulic press according to the invention allows: a reduction in the number of hydraulic components installed, with consequent reduction in breakdowns and less maintenance required; a reduction in the heat of the hydraulic oil which advantageously avoids the use of heat exchangers and requires fewer litres of oil in the tank, in addition to prolonging the life of the oil; an estimated 40% to 70% reduction in electric energy consumption; a 20-30dB reduction in noise level of the press.

[0047] Brief description of the drawings

[0048] The advantages of the invention will become clearer from the description below, in which two preferred embodiments are illustrated, by way of non-limiting example, and with the help of the figures, where:

[0049] Fig. 1 shows schematically a hydraulic press according to a first variation of the invention;

[0050] Fig. 2 shows schematically a hydraulic press according to a second variation of the invention.

[0051] Detailed disclosure of preferred embodiments of the invention

[0052] With reference to Figure 1 a diagram of a hydraulic press 10 according to the invention is illustrated.

[0053] Said hydraulic press 10 comprises:

[0054] - a press cylinder 1 , comprising a double-acting hydraulic piston 11 at one end of which a pressing plate 12 is associated, dividing said press cylinder into a first chamber A and a second chamber B, each provided with an opening 13, 14 for the inlet and outlet of oil into and out of each of said chambers A, B;

[0055] - a first hydraulic pump R1 ;

[0056] - a first electric motor M1 ;

[0057] - an oil tank 2;

[0058] - a first hydraulic circuit in which said oil circulates; - a first electric circuit;

[0059] - a suction valve 3 arranged along said first hydraulic circuit, between said oil tank 2 and said press cylinder 1 , thus allowing the passage of oil into said first chamber A of said press cylinder 1 through an upper opening 15 thereof;

[0060] - a safety valve block 4 for said first hydraulic circuit;

[0061] - a first driver 5 to electronically drive at least said first electric motor M1.

[0062] In the variation illustrated, said hydraulic press 10 comprises a single press cylinder 1 , but in alternative variations, in order to increase the working speed during the downstroke, said press cylinder could be flanked by two further smaller cylinders, or be replaced with an “animated” cylinder (small cylinder inside a bigger cylinder).

[0063] Said first hydraulic pump P1 is of the type adapted to function both as an operating machine and a prime mover. In the first case to pump oil into said hydraulic circuit, powered by the electric energy provided by said first motor M1 ; in the second case to drive said first motor M1 .

[0064] Advantageously, said first pump is a four-quadrant pump which, due to its construction, is able to function both as a pump and as a motor; it can change rotation direction (right-hand or left-hand) and therefore if included in an appropriately structured system it can function also as an energy generator.

[0065] Said first electric motor M1 is of the brushless type, and is also adapted to function both as an operating machine and as a prime mover. Said first driver 5 is operatively connected to said first motor M1 and programmed in order to manage the flows of electric energy between them, in both directions, thus being able to receive the electric energy produced by said first motor M1 and if necessary, supply it to the latter at a later time.

[0066] Along said hydraulic circuit there are two further valves S1 , S2 for the direct passage of oil from said tank 2 to said first pump P1 , without passing through the press cylinder 1. Said valves S1 and S2 are actuated automatically according to the active rotation direction of the first pump P1 .

[0067] Again with reference to the variation of Figure 1 , said hydraulic press 10 comprises an electric energy rechargeable battery 6, and said first electric circuit comprises a first rectifier 7 interposed between said first driver 5 and said rechargeable battery 6.

[0068] Said first driver 5 is operatively connected to said rechargeable battery 7 in order to manage the electric energy flows between said first motor M1 and said rechargeable battery 6 in both directions, thus allowing said rechargeable battery 7 to receive and accumulate energy, and then supply it to the hydraulic press 10 as required.

[0069] Advantageously, said rechargeable battery 6 is operatively connectable also to utilities external to said hydraulic press 10 to manage the power supply thereof.

[0070] The operation of the hydraulic press 10 of Figure 1 is the following, described in relation to the operating phases of the press cylinder 1 . The first phase (phase 1 ) entails the rapid downstroke by gravity of the hydraulic piston 11 which begins to compress the oil in the second chamber B of the press cylinder 1 to cause it to flow out of the second opening 14 and into the first hydraulic circuit, in order to rotate said first pump R1 with set rotation direction, for example right-hand; as the speed of the downstroke by gravity of the hydraulic piston 11 increases, the oil is sent back to the press cylinder 1 , into its first chamber A through the first opening 13; simultaneously from the opening 15 oil is sucked directly from the tank 2 by means of the suction valve 3; said first pump P1 , with its right-hand rotation movement, functions as a prime mover and drives said first motor M1 which begins to generate electric current; the electric current produced is sent to the first driver 5; part of this current is sent from the first driver 5 to said rechargeable battery 6; by regulating the number of revolutions of the motor, the downstroke speed of the hydraulic piston is also regulated, without having to use proportional valves.

[0071] The second phase (phase 2) entails slowing the downstroke by gravity of the hydraulic piston 11 , in preparation for the subsequent work and thrust phase: by setting in said first motor M1 a torque and a descending revolution slope, by means of said first driver 5, said first pump P1 brakes the descent speed of the hydraulic piston 11 ; in this phase said first motor M1 continues to act as a generator and sends electric current to the first driver 5, which in turn conveys it partly to the rechargeable battery 6. The third phase (phase 3) is the actual work and thrust phase of the press cylinder 1 : said first motor M1 , being a brushless motor, has a an efficiency and torque superior to a traditional asynchronous motor, and consumes much less electric energy for its operation; due to the difference in the thrust areas of the press cylinder 1 , said first pump P1 has to suck additional oil to be sent back to the press cylinder 1 , in addition to the oil coming from the opening 14; said first pump P1 therefore sucks oil directly from the tank 2 through the valve S1 .

[0072] The fourth phase (phase 4) is the last phase which closes the work cycle of the press cylinder 1 and is the opening phase of the hydraulic press 10 with upstroke of the hydraulic piston 11 : in this phase said first pump P1 rotates in the opposite rotation direction, for example left-hand, and sends the oil to the opening 14 of the press cylinder 1 ; due to the difference in the thrust areas of the press cylinder 1 , it is necessary to open the suction valve 3 to convey the additional oil from the opening 15 to the tank 2.

[0073] Figure 2 illustrates a diagram of a hydraulic press 10 according to a possible variation of the invention in which the thrust of the press cylinder 1 is supplemented by a counterthrust of a sheet clamping assembly 20.

[0074] Said sheet clamping assembly 20 comprises:

[0075] - a sheet clamping cylinder 21 ;

[0076] - a second hydraulic pump P2 of the type adapted to function both as an operating machine and a prime mover; - a second electric motor M2 of brushless type, adapted to function both as an operating machine and a prime mover;

[0077] - a second hydraulic circuit in which said oil circulates;

[0078] - a second electric circuit;

[0079] - a safety valve block 24 for said second hydraulic circuit;

[0080] - a second driver 25 adapted to electronically drive at least said second electric motor M2.

[0081] Also said second pump P2 is a four-quadrant pump.

[0082] Said second driver 25 is operatively connected at least to said second motor M2 and to said first driver 5, and programmed in order to manage the electric energy flows between them in both directions.

[0083] Said second driver 25 is operatively connected also to said rechargeable battery 6, in order to manage the electric energy flows between them in both directions. For said purpose, said second electric circuit comprises a second rectifier 27 interposed between said second driver 25 and said rechargeable battery 6.

[0084] In operating terms, said sheet clamping assembly 20 contributes to the functioning of the hydraulic press 10 during the third above- mentioned work and thrust phase (phase 3).

[0085] During the work and thrust phase of the press cylinder 1 , simultaneously the sheet clamping cylinder 21 compresses the oil towards the second pump P2 (phase 3a). The second pump P2 begins to work as a prime mover and rotates the second motor M2 which has been given appropriate torque. Said second motor M2 begins to generate electric current which, by means of said second driver 25, is sent to the first driver 5 and consequently supports the first motor M1 . Any excess current is sent from the second driver 25 to the rechargeable battery 6.

Claims

CLAIMS1 . A hydraulic press (10) comprising:- at least one press cylinder (1 );- a first hydraulic pump (P1);- a first electric motor (M1 );- an oil tank (2);- a first hydraulic circuit in which said oil is adapted to circulate;- a first electric circuit;- safety valves (4) for said first hydraulic circuit, characterized in that:- said first hydraulic pump (P1) is of the type adapted to function both as an operating machine and as a prime mover;- said first electric motor (M1 ) is of the brushless type, adapted to act both as an operating machine and as a prime mover; and said hydraulic press (10) comprises a first driver (5) operatively connected at least to said first electric motor (M1 ) in order to drive said first electric motor (M1 ) and to manage the electric energy flows between them in both directions.

2. The hydraulic press (10) according to claim 1 , characterized in that it comprises:- a sheet clamping cylinder (21 );- a second hydraulic pump (P2) of the type adapted to function both as an operating machine and as a prime mover;- a second electric motor (M2) of the brushless type, adapted to act both as an operating machine and as a prime mover;- a second hydraulic circuit in which said oil is adapted to circulate;- a second electric circuit;- safety valves (24) for said second hydraulic circuit;- a second driver (25) adapted to electronically control said second electric motor (M2), wherein said second driver (25) is operatively connected at least to said second electric motor (M2) and to said first driver (5), in order to drive said second electric motor (M2) and to manage the electric energy flows between them in both directions.

3. The hydraulic press (10) according to claim 1 , characterized in that said first hydraulic pump (P1) is a four-quadrant pump.

4. The hydraulic press (10) according to claim 2, characterized in that said second hydraulic pump (P2) is a four-quadrant pump.

5. The hydraulic press (10) according to claim 1 , characterized in that it comprises an electric energy rechargeable battery (6), wherein said first driver (5) is operatively connected at least to said rechargeable battery (6) in order to manage the electric energy flows between said hydraulic press (10) and said rechargeable battery (6) in both directions.

6. The hydraulic press (10) according to claim 5, characterized in that said rechargeable battery (6) is operatively connectable also to external utilities, as well as to said hydraulic press (10), to manage the power supply thereof.

7. The hydraulic press (10) according to claim 5, characterized in that said first electric circuit comprises a first rectifier (7) interposed between said first driver (5) and said rechargeable battery (6).

8. The hydraulic press (10) according to claims 2 and 5, characterized in that said second driver (25) is operatively connected to said rechargeable battery (6) in order to manage the electric energy flows between said hydraulic press (10) and said rechargeable battery (6) in both directions.

9. The hydraulic press (10) according to claim 8, characterized in that said second electric circuit comprises a second rectifier (27) interposed between said second driver (25) and said rechargeable battery (6).

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