WO2021014330A1

WO2021014330A1 - Hydraulic-gas system for pressurising a working fluid

Info

Publication number: WO2021014330A1
Application number: PCT/IB2020/056789
Authority: WO
Inventors: Flavio Tondolo; Nicola Zenoni; Emanuele MONTAGNA
Original assignee: STI SRL
Current assignee: STI SRL
Priority date: 2019-07-23
Filing date: 2020-07-20
Publication date: 2021-01-28
Anticipated expiration: 2022-01-23
Also published as: IT201900012627A1; EP4004381C0; EP4004381B1; EP4004381A1

Abstract

A gas-hydraulic system (100) for pressurizing a working fluid comprising a main tank (7) containing a working fluid and comprising a maximum level switch ( 10) and a minimum level switch (11), a secondary tank (6) containing the same working fluid, a first circuit (A) crossed by a gas under pressure from an inlet line (1), comprising a pressure reducer (4) supplied by the inlet line (1) and fluid-dynamically connected to the secondary tank (6), and comprising a valve (12) supplied by the inlet line (1) and fluid- dynamically connected to the main tank (7), a second circuit (B) crossed by the working fluid, comprising a hydraulic supply line (2) in fluid-dynamic connection between the main tank (7) and at least one external user, and in turn comprising a first non-return valve (15); a hydraulic return line (3) in fluid-dynamic connection between said at least one external user and the secondary tank (6) and comprising a second non-return valve (14); a hydraulic connection line (23) between the main tank (7) and the secondary tank (6), comprising a third non-return valve (8).

Description

HYDRAULIC-GAS SYSTEM FOR PRESSURISING A WORKING FLUID

DESCRIPTION

Technical field of the invention

The present invention relates to a gas-hydraulic system for pressurizing a working fluid. In particular, the system consists of a gas-hydraulic control unit that uses high-pressure gas for pressurizing oil supplied to one or more users.

Prior art

As is known and in few words, the technical field in question refers to systems useful for pressurizing a working fluid. Many servomechanisms have in fact among their main components such systems, mostly made of a hydraulic pump driven by an electric motor, wherein the electric energy delivered by the motor is transformed into pressure energy of the working fluid .

In known systems, the aforementioned technology is typically used, i.e. by using an electro-hydraulic control unit, which is characterized by significant plant costs. In addition, a single electro-hydraulic control unit is typically dedicated to a single user, which can be an actuator operating a single valve or a plurality of valves. This entails a considerable plant engineering complexity and a significant economic commitment. To the state of the art, electro-hydraulic control units are not in any case known, which are used to supply several users at the same time, nor control units of other types, but with clear advantages in term of plant costs.

There is therefore a need to define a control unit or a pressurization system that allows to obtain the advantages mentioned above.

Summary of the invention

The object of the present invention is therefore a gas-hydraulic system for pressurizing a working fluid, for example oil, supplied to one or more users. This working fluid can be pressurized by the line gas taken upstream or downstream of a valve, or from any other source of high-pressure gas.

Advantageously, users are connected exclusively to the hydraulic line of the working fluid and are not directly connected to the high-pressure gas. Users can also employ purely hydraulic components, which are more readily available, have lower cost and typically require less certifications compared to similar pneumatic components. This latter advantage is particularly relevant if being used on hydraulic components in replacing pneumatic components operating at pressures higher than 100 bar.

Therefore, the solution object of the present patent allows to use a single gas-hydraulic system to operate several users simultaneously, as specified in the attached independent claim.

The dependent claims outline particular and further advantageous aspects of the invention.

Brief description of the drawings

These and other advantages of the invention will now be described in detail, with reference to the attached Figures, which represent an exemplary embodiment of the invention, in which:

- Figure 1 shows a diagram of the system object of the present invention;

Figures 2A and 2B show the two main diagrams constituting the system of Figure 1, which is the object of the present invention, namely the first circuit A and the second circuit B (respectively of pneumatic and hydraulic type) deliberately separated for explanatory purposes;

- Figure 3 shows a variant of the system of Figure 1.

Detailed description

With reference to Figure 1 and to the attached Figures 2A and 2B, according to one absolutely non limiting embodiment of the present invention, a gas- hydraulic system 100 is shown, consisting of a first circuit A that draws gas from the inlet line 1. This gas is used to increase the oil pressure in a second circuit B, comprising in particular a hydraulic supply line 2 and a hydraulic return line 3. In this circuit B a working fluid circulates, for example oil under pressure. This latter is sent to users passing through the hydraulic supply line 2. The pressurized oil then returns to the gas-hydraulic system 100 through the hydraulic return line 3. The oil within the second circuit B takes high operating pressures, usually greater than 30 bar, and can be used to supply one or more users. For explanatory purposes, Figures 2A and 2B separately illustrate the first circuit A and the second circuit B.

As shown in Figure 1, the line gas entering into the gas-hydraulic system 100 may be picked up by a valve 30, in particular a selector 31 defining whether to supply the gas-hydraulic system 100 by drawing it from a first line 30', upstream of the valve 30, or from a second line 30", downstream of the valve 30 itself .

The gas entering the system passes then through the first circuit A to the pressure line, passes through a pressure reducer 4 and enters into a secondary tank 6 containing oil. The gas entering the first circuit A can also come from an auxiliary supply line 17, useful for example in cases where the valve 30 is submitted to maintenance and no pressurized gas is available. The gas then pressurizes the oil into the secondary tank 6 up to a pressure value imposed by the pressure reducer 4 and visible on the manometer

5. Through the second circuit B, the oil passes then to the main tank 7 through a third non-return valve 8, along a hydraulic connection line 23, whereas a second no-return valve 14 prevents the supply along the return hydraulic line 3. The oil level in the main tank 7 increases, therefore, up to reach an upper limit level imposed by a maximum electric level switch 10. When the oil reaches such level, the level switch 10 is triggered by activating a valve 12 through a controller 16, in order to allow the gas with the line pressure coming from the first circuit to pressurize the oil contained in the main tank 7 through the valve 12. In this manner, a further increase of the oil level is prevented, a situation which would lead to the leakage of such fluid from the main tank 7, for example through a silencer 13 downstream of the valve 12. Advantageously, the valve 12 may be a solenoid valve or a pneumatic valve and can be normally closed or normally open.

Following the action of the line gas entering the main tank 7, the pressurized oil contained in such tank 7 is then sent to the users through the hydraulic supply line 2, passing through a first non-return valve 15. The third non-return valve 8 prevents it from being supplied to the secondary tank 6. During this loading phase of the users, the oil level contained in the main tank 7 decreases up to the level dictated by the minimum level electric switch 11.

When the oil reaches such lower limit level, the minimum level switch 11 acts by de-activating the valve 12 through the controller 16, so that the pressurized gas present in the main tank 7 is discharged, passing through the valve 12 and possibly the silencer 13. In this way, a complete discharge of the oil from the main tank 7 is avoided, a situation that would cause a failure in supplying such working fluid to the users. Finally, the return oil from the users reaches the secondary tank 6 through the second non-return valve 14 from the hydraulic return line 3, where it is again pressurized and supplied to the main tank 7.

Advantageously, the components of the system according to the present invention and shown in Figure 1 can be replaced by similar accessories having the same operational or logical functions. For example, the sub-group comprising the level switches 10 and 11, the valve 12 and the controller 16 may be replaced by a pneumatic system having the same functionality and logic, as well as the main tank 7 can be replaced by a storage tank or of another type.

It is also possible to add other components to the gas-hydraulic system 100 of the present invention without affecting its operation, such as for example by connecting to the tanks 6 and 7 respectively a safety valve 18 and 19 for controlling the over pressures. Such a variant can be adopted for safety reasons or if expressly required by current regulations .

A further embodiment of the present invention of particular interest consists instead of using an storage tank 20 and a fourth non-return valve 21, in order to keep the supply line 2 under pressure up to the users. During the step of recharging the main tank 7, the users might equally require pressurized oil, which unfortunately is not available during such phase. The storage tank 20 thus allows to guarantee the oil supply to the users, by temporarily replacing the main tank 7 and allowing the latter to finish the recharging cycle. Unfortunately, the oil supplied by the storage tank 20 will result in a lower pressure than that supplied by the main tank 7. At the same time, this latter tank, once the oil recharging phase is finished and the supply phase to the users is restarted, this will also have the function of recharging the storage tank 20, by using a part of the oil useful to the users.

In order to improve such a solution, a more efficient implementation mode is shown in Figure 3, in which the circuit is similar to that of Figure 1 but has the redundancy of the components 7, 8, 10, 11, 12, 15 and adds a further control valve 22. In

Figure 3, to facilitate the understanding, possible additional components are also not shown: safety valve 18, 19, storage tank 20 and fourth non-return valve 21, but nothing excludes their possible use, as described above. For the same reason, the valve 30 and the selector 31 are not shown. The controller 16 can be set in such a way to operate the valves 22, 12 and 12' in order to ensure the continuous supply of oil to users. In particular, if the tank 7 would be supplying oil to the users (with the valve 12 activated) and would turned out to be at the lower limit level specified by the respective minimum level switch 11 (as shown in Figure 3), the controller 16 actuates the valves 22, 12, 12' according to the following phases:

actuating the valve 12' to pressurize the working fluid in the tank 7' by means of the high pressure line gas of the first circuit A, starting the supply phase of the working fluid to the users. At the end of this phase, the tank 7' can therefore fulfill the users' request for oil,

- actuating the valve 22 so as to discharge the residual gas present in the duct between the control valve 22 and the valves 12, 12',

deactivating the valve 12 to discharge the residual gas present in the main tank 7 through the valve 22, thus starting the recharging phase of the main tank 7,

- by attaining of the maximum specified level from the maximum level switch 10, deactivating the valve 22 for connecting in a fluid-dynamic way the main tank 7 with the gas pressure reduced downstream of the reducer filter 4, thereby finishing the recharging of the main tank 7 and keeping the oil level in the main tank 7 constant, so as to be able to fulfill a hypothetical request for oil by the users.

In such way the two tanks 7, 7' alternate the oil recharging and supply phases, so ensuring a continuous supply to the users.

Advantageously, the actuation of several users by means of a pressurized working fluid is obtained by means of the present invention without the use of any hydraulic pump and relative electric motor. The only source of energy is constituted by a gas still available between the plant technical means, typically made of a line of compressed air or of another gas available under pressure. In addition, it is sufficient to supply a minimum quantity of electric energy to be used to control the solenoid valve, if present as shown in Figure 1. Ultimately, the proposed solution has an extreme plant simplicity and is economically advantageous compared with known solutions. It should also be noted that the total number of users involved may exceed the unit, just as the type of such users may be of different nature (hydraulic actuators or other) .

Even if at least one exemplary embodiment has been presented in the summary and in the detailed description, it must be understood that a large number of variants are possible within the scope of protection of the invention. Furthermore, it must be understood that the embodiment or the embodiments shown are only examples which do not intend in any way to limit the scope of protection of the invention or its application or configurations. Instead, the short and detailed description will provide the skilled technician in the sector with a convenient guide for implementing at least one exemplary embodiment, being it clear that numerous variants can be made in the function and assembly of the elements described herein, without departing from the scope of protection of the invention, as established by the attached claims and by their technical-legal equivalents .

Claims

1. Gas-hydraulic system (100) for pressurizing a working fluid comprising:

- a main tank (7) containing a working fluid and comprising a maximum level switch (10) and a minimum level switch (11),

- a secondary tank (6) containing the same working fluid,

- a first circuit (A) traversed by gas under pressure coming from an inlet line (1), comprising a pressure reducer (4) supplied by the inlet line (1) and fluid connected to the secondary tank (6), and comprising a valve (12) supplied by the inlet line (1) and fluid connected to the main tank (7),

- a second circuit (B) traversed by the working fluid, comprising a hydraulic delivery line (2) in fluid connection between the main tank (7) and at least an external user, and in turn comprising a first non-return valve (15) ); a hydraulic return line (3) in fluid connection between said at least an external user and the secondary tank (6) and comprising a second non-return valve (14); a hydraulic connection line (23) between the main tank (7) and the secondary tank (6), the hydraulic connection line (23) comprising a third non-return valve (8),

wherein : - the main tank (7) is fed with the working fluid coming from the secondary tank (6) at a pressure higher than the opening pressure of the third non return valve (8), and the volume of working fluid contained therein varies from a minimum level determined by the minimum level switch (11) to a maximum level determined by the maximum level switch (10) ,

- the secondary tank (6) is fed with the working fluid coming from the hydraulic return line (3), when the pressure of the working fluid is higher than the opening pressure of the second non-return valve (14), said gas-hydraulic system (100) being characterized in that:

- when the maximum volume of working fluid in the main tank (7) is reached, the valve (12) is activated by means of a controller (16) and is configured to pressurize the working fluid present in the main tank (7) through the pressurized gas coming from the first circuit (A), so that the main tank (7) feeds the delivery line (2) with the working fluid at a pressure higher than the opening pressure of the first non return valve ( 15) , and

- when the minimum volume of working fluid in the main tank (7) is reached, the valve (12) is de activated by means of the controller (16) and is configured to discharge the gas under pressure in the main tank (7 ) so as to depressurize the working fluid in the main tank (7) and start the refilling phase of the main tank (7) .

2. System (100) according to claim 1, wherein the gas coming from the inlet line (1) is taken from a valve (30) comprising a selector (31) which extracts the gas from a first line (30 ') positioned upstream of the valve (30) or from a second line (30 ") positioned downstream of the valve (30) itself.

3. System (100) according to claim 2, wherein the gas entering the first circuit (A) comes from an auxiliary supply line (17) when gas under pressure from the inlet line (1) is not available.

4. System (100) according to any of the preceding claims, wherein the pressure of the gas entering the secondary tank (6) and coming from the inlet line (1) is regulated by the pressure reducer (4) in turn connected to a pressure gauge (5) .

5. System (100) according to any of the preceding claims, wherein the valve (12) has a silencer (13) downstream in order to discharge the main tank (7) .

6. System (100) according to any of the preceding claims, further comprising a safety valve (18) connected to the secondary tank (6) and a safety valve (19) connected to the main tank (7) for controlling the overpressures.

7. System (100) according to any of the preceding claims, further comprising a storage tank (20) and a fourth non-return valve (21) for guaranteeing the delivery of oil to the users when the main tank (7) does not feed the line of delivery (2) .

8. System (100) according to one of the preceding claims, wherein the components main tank (7, 7 '), third non-return valve (8, 8'), maximum level switch (10, 10 '), minimum level switch ( 11, 11 '), valve (12, 12')_/ first non-return valve (15, 15 ') are present in redundancy in number of two for each component and said system (100) comprises a further control valve (22 ) .

9. Method of operating the system (100) according to claim 8, wherein if one of the two main tanks (7) is at the minimum level specified by the respective minimum level switch (11), then with the valve (12) activated, the controller (16) manages the valves (22, 12, 12 ') according to the following phases:

- activate the valve (12 ' ) to pressurize the working fluid in the tank (7 ' ) using the high pressure line gas of the first circuit (A) , starting the delivery phase of the working fluid to the users, activate the valve (22) to discharge the residual gas present in the duct between the control valve (22) and the valves (12, 12'), - de-activate the valve (12) to discharge through the valve (22) the residual gas present in the main tank (7), thus starting the refilling phase of the main tank ( 7 ) ,

- upon reaching the maximum level specified by the maximum level switch (10), de-activate the valve (22) to fluidly connect the main tank (7) with the reduced pressure gas downstream of the reduction filter (4), ending in this way the way of recharging the main tank (7) and maintaining the level of the working fluid in the main tank (7) constant, so as to be able to start a subsequent phase of delivery of the working fluid to the users if required.