Fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities

Abstract

Fluid-operated circuit (1) for the supply of primary and auxiliary utilities with predefined priorities comprising: a variable displacement pump (2), one supply line (4) connected to the pump (2), one primary line (5) communicating with the supply line (4) and connectable to a first utility (UP) with primary priority, at least one auxiliary line (6, 6a, 6b) connectable to a relevant auxiliary utility (UA1, UA2) with lower predefined priority than the primary priority; valve means (7) located between the supply line (4) and the at least one auxiliary line (6, 6a, 6b) and movable between at least one home position and at least one work position; piloting means (8) of the valve means (7) comprising at least a first piloting line (9) operating to push them from the home position to the work position, a second piloting line (10) operating on opposite side of the first piloting line (9), and first elastic means (11) operating on the same side of the second piloting line (10); a discharge line (12) connectable to a discharge tank (T); wherein the piloting means (8) comprise additional elastic means (13) operating on the valve means (7) in combination with the first elastic means (11) and wherein the valve means (7) are movable to at least one discharge position when the force operating on the valve means (7) and depending on the pressure along the first piloting line (9) is greater than the force operating on the opposite side and depending on the action exerted by the first elastic means (11), by the additional elastic means (13) and by the pressure along the second piloting line (10).

Description

Technical Field

[0001] The present invention relates to a fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities.Background Art

[0002] In fluid-operated circuits it happens that it is necessary to establish the so-called "priorities" when supplying various utilities with a pumping unit. In particular, the utilities having higher priority need to be supplied first than those having lower priority.

[0003] For example, the utility having the highest priority is generally the steering device, which allows the operating machine to be steered in the desired directions. On the other hand, the utility having secondary priority (lower, therefore, than the main one) generally consists of the so-called "trailer-brake valve", which is adapted to transfer the braking action of the tractor to the braking system of the trailer in such a way that their respective braking actions are linked to each other. The utility having third priority (lower than the previous ones) is, e.g., the hydraulic distributor to which the functions relevant to the work of the machine, but not relevant to safety, are connected.

[0004] Additional utilities, having gradually decreasing priority (meaning that the level of importance of the utility is gradually lower), may be the different auxiliary services with which the tractor is provided, such as e.g. the implements with which it is provided.

[0005] In more detail, the fluid-operated circuits of known type comprise a pumping unit adapted to deliver a pressurized work fluid (usually oil), and a supply line communicating with that pumping unit and adapted to convey the pressurized fluid towards the various utilities.

[0006] While the utility having main priority is directly connected to the supply line, between the other utilities (having gradually decreasing priority and defined hereafter as "auxiliary utilities") and such supply line are placed valve means movable between at least one home position, wherein they interrupt the connection between the supply line and the auxiliary utilities, and at least one work position, wherein they set said supply line in communication with at least one auxiliary utility. More particularly, such valve means have a plurality of work positions, i.e., one work position for each auxiliary utility, where upon reaching each work position (moving away from the home position) the connection between the supply line and the corresponding auxiliary utility is opened, while keeping open the connection with the auxiliary utility corresponding to the previous work position (and thus having higher priority).

[0007] Appropriately, piloting means of such valve means are provided which comprise a first piloting line, communicating with the supply line and operating on the valve means, and a second piloting line, communicating with the auxiliary utility having higher pressure and operating on the valve means on the opposite side from the first piloting line. On the same side as the second piloting line, first elastic means also operate. Thus, in order to displace the valve means from the home position to the work positions, it is necessary that the force exerted by the pressure along the first piloting line is higher than the sum of the force exerted by the pressure along the second piloting line and the force exerted by the first elastic means.

[0008] A fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities is, e.g. known from WO 2004 / 046561 A1.

[0009] It may happen that the utilities require no flow rate of the pressurized fluid, or the flow rate required by them drops below the minimum flow rate deliverable by the pumping unit. Under these operating conditions, it is necessary for the flow rate delivered by the pumping unit to be sent to a discharge tank.

[0010] Thus, the circuits of known type comprise a flushing valve, separated from the aforementioned valve means, adapted to set the supply line in communication with a discharge tank under the operating conditions as mentioned in the previous paragraph.

[0011] These circuits of known type do however have some drawbacks.

[0012] They are, in fact, complex to implement, since they require the presence of at least two valve units, i.e., valve means adapted to control the supply of the auxiliary utilities and of the flushing valve adapted to allow the work fluid to be conveyed to a discharge tank in case of no or insufficient demand from the auxiliary utilities, where the respective operations must properly combine with each other.

[0013] Another drawback of the circuits of known type consists in the fact that the activation of the flushing valve involves energy expenditure which adversely affects the performance of the circuit.Description of the Invention

[0014] The main aim of the present invention is to devise a fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities which allows simplifying, compared with the circuits of known type, the control of the work fluid delivered by the pumping unit in the event of no or insufficient demand from the auxiliary utilities.

[0015] Within this aim, one object of the present invention is to devise a circuit which allows minimizing the energy expenditure in discharging the work fluid delivered by the pumping unit to its minimum displacement in the event of no or insufficient demand from the auxiliary utilities.

[0016] Another object of the present invention is to devise a fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities which allows the aforementioned drawbacks of the prior art to be overcome within the framework of a simple, rational, easy and effective to use as well as affordable solution.

[0017] The aforementioned objects are achieved by this fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities according to claim 1.Brief Description of the Drawings

[0018] Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities, illustrated by way of an indicative, yet non-limiting example in the accompanying tables of drawings in which: Figure 1 is the hydraulic diagram of a circuit according to the invention, in a first embodiment; Figure 2 is a section of the valve means of the circuit in Figure 1; Figure 3 is the hydraulic diagram of a circuit according to the invention, in a second embodiment; Figure 4 is a section of the valve means of the circuit in Figure 3; Figure 5 is the hydraulic diagram of a circuit according to the invention, in a third embodiment; Figure 6 is the hydraulic diagram of a circuit according to the invention, in a fourth embodiment; Figure 6a is a variation of the hydraulic diagram of the circuit in Figure 6; Figure 7 is a cross-sectional view of the valve means of the circuit in Figure 5 in the home position; Figure 8 is a cross-sectional view of the valve means of the circuit in Figure 5 in the discharge position and with the additional elastic means in the home configuration; Figure 9 is a cross-sectional view of the valve means of the circuit in Figure 5 in a work position; Figure 10 is a cross-sectional view of the valve means of the circuit in Figure 5 in the discharge position and with the additional elastic means pre-loaded; Figure 11 is the hydraulic diagram of a circuit according to the invention, in a fifth embodiment; Figure 11a is a variation of the hydraulic diagram of the circuit in Figure 11; Figure 12 is a cross-sectional view of the valve means of the circuit in Figure 10 in the home position; Figure 13 is a cross-sectional view of the valve means of the circuit in Figure 10 in the discharge position and with the additional elastic means in the home configuration; Figure 14 is a cross-sectional view of the valve means of the circuit in Figure 10 in a work position; Figure 15 is a cross-sectional view of the valve means of the circuit in Figure 10 in the discharge position and with the additional elastic means pre-loaded; Figure 16 is the hydraulic diagram of a circuit according to the invention, in a sixth embodiment; Figure 17 is the hydraulic diagram of a circuit according to the invention, in a seventh embodiment. Embodiments of the Invention

[0019] With particular reference to these figures, reference numeral 1 globally denotes a fluid-operated circuit for the supply of primary and auxiliary utilities with predefined priorities.

[0020] The circuit 1 comprises a variable displacement pump 2 adapted to deliver a pressurized fluid, e.g., oil, where such pump 2 comprises a displacement regulating device 3.

[0021] The displacement regulating device 3 can be of the mechanical or electronic type. Then, the circuit 1 comprises at least one supply line 4 connected to at least the pump 2, at least one primary line 5 communicating with the supply line 4 and connectable to a first utility U P with primary priority, such as e.g. the steering unit, and at least one auxiliary line 6 connectable to a relevant auxiliary utility U A having a predefined priority. The auxiliary utility U A has a relevant lower priority than the aforementioned primary priority.

[0022] More particularly, the primary line 5 is directly connected to the supply line 4. The circuit 1 may comprise a single auxiliary line 6 or a plurality of auxiliary lines 6, each of which is connected to a relevant auxiliary utility U Ai having a predefined priority and is identified with a relevant index (6a, 6b, ..., 6i) identifying the priority order of the relevant utility.

[0023] In the embodiment of Figure 1, the circuit 1 comprises only one auxiliary line 6, while in the embodiment of Figure 2, the circuit 1 comprises two auxiliary lines 6, of which a second line 6a can be connectable to a second utility U A2 with lower priority than the first utility U P , corresponding, e.g., to the braking valve of a trailer (not shown in the figures), and a third line 6b connectable to a third utility U A3 with lower priority than the second utility U A2 , corresponding, e.g., to a hydraulic distributor.

[0024] As known to the engineer in the field, the circuit 1 may comprise more auxiliary lines 6 than shown in the attached figures and each having a corresponding predefined priority.

[0025] The circuit 1 comprises valve means 7 located between the supply line 4 and the auxiliary line 6 and movable between at least one home position, wherein they stop the connection between the supply line 4 and the auxiliary line 6, and at least one work position, wherein they set the supply line 4 in communication with at least one auxiliary line 6.

[0026] Appropriately, the circuit 1 comprises a plurality of auxiliary lines 6, each of which is connectable to a relevant auxiliary utility U Ai with decreasing priorities, and the valve means 7 have a plurality of work positions arranged in succession away from the home position, where in each work position the supply line 4 is set in communication with an additional auxiliary line 6 with respect to the previous work position.

[0027] More specifically, the valve means 7 comprise a number of work positions equal to the number of auxiliary lines 6 and arranged in succession according to the priority order of the relevant utilities, where at each of these work positions the supply line 4 is set in communication with a corresponding auxiliary line 6. In other words, the first work position reached by the valve means 7 as a result of the displacement from the home position sets the supply line 4 in communication with the auxiliary line 6 having higher priority, that is, with the second line 6a. Similarly, the second work position reached by the valve means 7 and arranged downstream of the first work position moving away from the home position, sets the supply line 4 in communication with the third line 6b.

[0028] Appropriately, by displacing away from the home position, the valve means 7, in each work position, not only sets the supply line 4 in communication with the corresponding auxiliary line 6 but also keep open the connection between the supply line itself and the auxiliary line 6 with respect to the previous work position.

[0029] The circuit 1 then comprises piloting means 8 of the valve means 7 comprising at least a first piloting line 9 communicating with the supply line 4 and operating on the valve means 7 to push them from the home position towards the work position, a second piloting line 10 communicating with the utility U P , U Ai , between the first utility U P and the auxiliary utilities U Ai , having higher pressure and operating on the opposite side from the first piloting line 9, and first elastic means 11 operating on the valve means 7 from the same side as the second piloting line 10.

[0030] More specifically, the circuit 1 comprises one or more valves V, also known as "shuttle valves", adapted to selectively set the second piloting line 10 in communication with the utility U P , U Ai (and more in detail with the relevant piloting lines), between the first utility U P and the auxiliary utilities U Ai , having higher pressure.

[0031] The displacement regulating device 3 is operationally connected to the second piloting line 10 to regulate the displacement of the pump 2 so that the pressure of the fluid delivered is higher than the pressure along the second piloting line itself by a predefined value V P (so-called "pump margin"). Such a predefined value V P can, e.g., be electronically controlled in real time in the system, or be of a fixed type.

[0032] Appropriately, the pump 2 may have a minimum displacement value, which allows delivering a minimum flow rate of the pressurized work fluid even if the pressure along the second piloting line 10 is substantially zero. Alternatively, the pump 2 may have zero displacement and the circuit 1 may comprise an external line 30 communicating with the supply line 4 and adapted to deliver a minimum flow rate of the pressurized work fluid.

[0033] The circuit 1 also comprises a discharge line 12 connectable to a discharge tank T.

[0034] According to the invention, the valve means 7 are located between the supply line 4 and the discharge line 12, and the piloting means 8 comprise additional elastic means 13 operating on the valve means 7 in combination with the first elastic means 11. Specifically, the first elastic means 11 and the additional elastic means 13 operate on the same side as the valve means 7.

[0035] According to the invention, the valve means 7 are movable to at least one discharge position, wherein they set the supply line 4 in communication with the discharge line 12, at least when the force operating on the valve means 7, depending on the pressure along the first piloting line 9, is higher than the force operating on the opposite side, depending on the action exerted by the first elastic means 11, by the additional elastic means 13 and by the pressure along the second piloting line 10.

[0036] Advantageously, the piloting means 8 comprise at least one actuator element 14 communicating with an additional piloting line 40 and adapted to pre-load the additional elastic means 13 when the pressure along the additional piloting line itself reaches a calibration value V T .

[0037] More particularly, the additional piloting line 40 can be separate from the second piloting line 10 or coincide therewith.

[0038] In this case (embodiments shown in Figures 5 to 15), the valve means 7 are movable to the discharge position when the pressure along the additional piloting line 40 is lower than the calibration value V T or when the force operating on the valve means 7, depending on the pressure along the first piloting line 9 is higher than the force operating on the opposite side, depending on the action exerted by the first elastic means 11, by the additional elastic means 13, when the pressure along the additional piloting line 40 is higher than the calibration value V T , and by the pressure along the second piloting line 10. In other words, the valve means 7 reach the discharge position in a first operating condition wherein the pressure along the additional piloting line 40 is lower than the calibration value V T (and only the contribution of the first elastic means 11 on the force balance is present), whereby the actuator element 14 remains inactive and the additional elastic means 13 are not pre-loaded thus remaining in the home (neutral) configuration, and in a second operating condition wherein the pressure along the first piloting line 9 is higher than the sum of the pressure along the second piloting line 10, and the equivalent pressure exerted by the first elastic means 11 and by the additional elastic means 13, where the latter are pre-loaded as a result of the action of the actuator element 14 following the attainment (or exceeding) of the calibration value V T by the pressure along the additional piloting line 40.

[0039] The valve means 7 displace from the home position towards the work position counteracting the first elastic means 11 only.

[0040] In the embodiments without the actuator element 14 (Figures 1 to 4), the valve means 7 reach the discharge position when the pressure along the first piloting line 9 is higher than the sum of the pressure along the second piloting line 10 and the equivalent pressure exerted by the first elastic means 11 and by the additional elastic means 13.

[0041] The work position is located between the home position and the discharge position.

[0042] More particularly, the discharge position is arranged downstream of the last work position with respect to the displacement of the valve means 7 away from the home position.

[0043] Preferably, the valve means 7 comprise at least one hollow body 15 defining a housing seat 16 provided with at least one supply port 17 communicating with the first piloting line 9 (which in the embodiment shown in the figures substantially coincides with the supply line 4), with at least one auxiliary port 18 communicating with a corresponding auxiliary line 6, with at least one discharge port 19 communicating with the discharge line 12 and with at least one piloting port 20 communicating with the second piloting line 10, wherein a distributor element 21 is housed within the housing seat 16 in a sliding manner and is movable to set the supply port 17 in communication with / isolate from the auxiliary port 18 and / or the discharge port 19.

[0044] Therefore, the distributor element 21, in the home position, isolates the supply port 17 from the auxiliary port 18 and from the discharge port 19, in the work position it sets the supply port 17 in communication with at least one auxiliary port 18 while closing the discharge port 19, and in the discharge position it sets the supply port 17 in communication with the discharge port 19.

[0045] In the event of the circuit 1 comprising a plurality of auxiliary lines 6, the housing seat 16 has as many auxiliary ports 18 as the number of the auxiliary lines 6 and, therefore, the work positions of the distributor element 21 are also equal in number to the auxiliary ports 18. Even in this case, the auxiliary ports 18 are identified with a relevant index (18a, 18b, ..., 18i) identifying the auxiliary line 6a, 6b, ..., 6i to which they are connected.

[0046] In each work position, the distributor element 21 opens the connection between the supply port 17 and a relevant auxiliary port 18, while keeping open the connection to the auxiliary port 18 corresponding to the previous work position (with reference to the displacement to the direction away from the home position). In the embodiments shown in Figures 2, 4, 7 to 10 and 12 to 15, the housing seat 16 has two auxiliary ports 18, of which a second port 18a communicating with the second line 6a and a third port 18b communicating with the third line 6b. The distributor element 21 then has, moving away from the home position, a first work position, wherein it sets the supply port 17 in communication with the second port 18a, and a second work position (subsequent to the first work position), wherein it opens the connection between the supply port 17 and the third port 18b. Thus, in the second work position, the supply port 17 is set in communication with both the second port 18a and the third port 18b.

[0047] In more detail, between the body 15 and the distributor element 21 is defined at least one first chamber 22 communicating with the supply port 17 and at least one second chamber 23 arranged on the opposite side of the first chamber 22 and communicating with the piloting port 20.

[0048] The first elastic means 11 are housed within the second chamber 23 and interact with the distributor element 21 to counteract the displacement from the home position towards the work position.

[0049] The distributor element 21 then moves within the housing seat 16 as a result of the resultant of the forces operating thereon.

[0050] The distributor element 21 has an active area on which the pressure of the work fluid coming from the supply line 4 (or the first piloting line 9) operates.

[0051] Preferably, the active area of the distributor element 21 is sized so that the force exerted thereon by a pressure of the work fluid equal to the predefined value V P (i.e., multiplied by the active area itself of the distributor element 21) is higher than the force exerted on the opposite side by the first elastic means 11. In other words: V P × A 1 > M 1

[0052] where M1 is the force exerted by the first elastic means, V P the characteristic predefined value of the pump 2 and A1 the active area of the distributor element 21. This ensures that the distributor element 21 is displaced towards the work position and, therefore, that the relevant auxiliary utilities U A are properly supplied.

[0053] Advantageously, the active area of the distributor element 21 is sized such that the resultant of the force exerted by the first elastic means 11 and by the additional elastic means 13 is higher than the force exerted by a pressure of the work fluid equal to the predefined value V P on the distributor element itself (i.e., multiplied by the active area of the distributor element 21). In other words: V P × A 1 < M + M 12 where M 1 is the force exerted by the first elastic means, M 2 the force exerted by the additional elastic means, V P the characteristic predefined value of the pump 2 and A 1 the active area of the distributor element 21. In this way, during normal operation (which in the embodiments shown in Figures 5 to 15 corresponds to the condition wherein the pressure along the additional piloting line 40 is higher than the calibration value V T ) the discharge port 19 remains closed and is opened only when the flow rate demand from lines 5 and 6 drops below the value corresponding to the minimum flow rate flowing through the supply line 4 and delivered by the pump 2 or by the external line 30 (depending on the embodiment).

[0054] The distributor element 21 moves towards the home position when the pressure difference between the supply line 4 and the second piloting line 10 is lower than the predefined value V P .

[0055] Appropriately, the body 15 can be made as a single body piece or in several parts locked together with each other.

[0056] In the embodiment shown in the figures, the additional elastic means 13 are also housed within the second chamber 23 and the piloting means 8 comprise at least one abutment element 25 located between the distributor element 21 and the additional elastic means 13, wherein such an abutment element 25 displaces so as to counteract the additional elastic means 13 as a result of the interaction with the distributor element 21 during its displacement from the work position to the discharge position.

[0057] In the embodiments shown in Figures 1 to 4, the additional elastic means 13 are located between the abutment element 25 and the body 15.

[0058] In the embodiments shown in Figures 5 to 15, the additional elastic means 13 are then located between the abutment element 25 and the actuator element 14. More particularly, the abutment element 25 has one end arranged to contact the additional elastic means 13 and the opposite end adapted to interact with the distributor element 21.

[0059] Preferably, the distributor element 21 travels a first stroke stretch C 1 , counteracting the first elastic means 11, to displace from the home position to the work position, and travels a second stroke stretch C 2 to displace from the work position to the discharge position.

[0060] Advantageously, the distributor element 21 travels the second stroke stretch C 2 counteracting the additional elastic means 13 (in the embodiments 5 to 15 this occurs when the pressure along the second piloting line 10 is higher than the calibration value V T so that the additional elastic means 13 are thus pre-loaded) to displace from the work position to the discharge position. More particularly, under this operating condition, the distributor element 21 interacts, at the end of the first stroke stretch C 1 , with the abutment element 25 and moves locked together therewith along the second stroke stretch C 2 .

[0061] Appropriately, the abutment element 25 rests against a stopping surface 27 at the end of the second stroke stretch C 2 .

[0062] In more detail, the first stroke stretch C 1 has a relevant end-of-stroke defined by the interaction of the distributor element 21 with the abutment element 25 and corresponding to the attainment of the last work position (in the case where a plurality of work positions are provided).

[0063] The second stroke stretch C 2 has in turn a relevant end-of-stroke defined by the interaction of the abutment element 25 with a stopping surface 27. In the embodiment shown in the figures, the stopping surface 27 is defined by the body 15.

[0064] In the embodiments 5 to 15, when the pressure along the additional piloting line 40 is lower than the calibration value V T , the additional elastic means 13 are in the home configuration (and therefore they exert no thrust on the abutment element 25) and the distributor element 21 travels the first stroke stretch C 1 and the second stroke stretch C 2 counteracting only the first elastic means 11 by switching from the home position to the discharge position.

[0065] Appropriately, the actuator element 14 has an active area communicating with the additional piloting line 40. Therefore, on the active area of the actuator element 14 operates the incoming fluid from the additional piloting line 40 to move it counteracting the additional elastic means 13, so as to cause the compression thereof. In the embodiments shown in the figures, the additional piloting line 40 coincides with the second piloting line 10 and the active area of the actuator element 14 is set in communication with the second chamber 23 so that the pressure of the incoming work fluid from the second piloting line itself operates on the second chamber itself.

[0066] More particularly, the piloting means 8 comprise at least one control element 28 operationally connected to the actuator element 14 to counteract the displacement thereof along the pre-loading direction of the additional elastic means 13 until the pressure along the additional piloting line 40 reaches the calibration value V T .

[0067] In the embodiments shown in Figures 4 to 11 and 12 to 15, the control element 28 consists of second elastic means adapted to interact with the actuator element 14 to counteract the displacement thereof along the pre-loading direction of the additional elastic means 13, where the active area of the actuator element 14 and the pre-load of the second elastic means 28 in the home condition (i.e., when they are not compressed by the actuator element 14, which is thus in the end-of-stroke position) define the calibration value V T beyond which the second elastic means 28 are compressed and the actuator element 14 displaces by compressing the additional elastic means 13.

[0068] In the alternative embodiments shown in Figures 6a and 11a, the control element 28 instead consists of a sequence valve arranged along the additional piloting line 40 and calibrated to a pressure equal to the calibration value V T . The work fluid pressure along the additional piloting line 40 then reaches the actuator element 14 only when it reaches or exceeds the calibration value V T .

[0069] After exceeding the calibration value V T , the actuator element 14 then moves closer to the abutment element 25.

[0070] In the embodiment shown in Figures 2 and 7 through 10, the valve means 7 comprise a stationary base element 24 associated with the body 15, where the first elastic means 11 have one end resting on such base element 24 and the opposite end resting on the distributor element 21. The distributor element 21 then moves closer to the base element 24, counteracting the first elastic means 11, in its displacement from the home position towards a work position.

[0071] More particularly, in this embodiment, the abutment element 25 has a rod-shaped portion 26, which is inserted through the base element 24 in a sliding manner and on which the first elastic means 11 are fitted. This rod-shaped portion 26 then operates as a spring guide for the first elastic means 11 and defines the end of the abutment element 25 adapted to interact with the distributor element 21.

[0072] Thus, in this embodiment, the first elastic means 11 and the additional elastic means 13 operate in parallel on the distributor element 21.

[0073] The abutment element 25 does not interact with the first elastic means 11.

[0074] In the embodiment shown in Figures 4 and 12 to 15, the abutment element 25 is located between the first elastic means 11 and the additional elastic means 13. In more detail, in the embodiment shown in Figures 12 to 15, the abutment element 25 moves counteracting the first elastic means 11 when the pressure along the additional piloting line 40 is higher than the calibration value V T .

[0075] The base element 24 defines a counter-stop 29 facing the stopping surface 27 and adapted to define the end-of-stroke of the abutment element 25 moving closer to the distributor element 21.

[0076] The body 15 defines the counter-stop 29 facing the stopping surface 27 and defining the end-of-stroke of the abutment element 25 moving closer to the distributor element 21.

[0077] At the moment when the abutment element 25 interacts with the distributor element 21, stopping against it, only the additional elastic means 13 operate on the distributor element 21. Thus, in this embodiment, the first elastic means 11 and the additional elastic means 13 operate in series with each other.

[0078] In the alternative embodiments shown in Figures 16 and 17, the additional elastic means 13 are pre-loaded and the piloting means 8 comprise at least one actuator element 14 communicating with an additional piloting line 40 and adapted to unload the additional elastic means 13 when the pressure along the additional piloting line itself reaches a calibration value V T . More specifically, the additional elastic means 13 thus exert a predefined force on the distributor element 21 when they are not actuated by the actuator element 14.

[0079] In these embodiments, the valve means 7 are movable to the discharge position when the pressure along the additional piloting line 40 is higher than the calibration value V T and when the force operating on the valve means 7 and depending on the pressure along the first piloting line 9 is higher than the force operating on the opposite side and depending on the action exerted by the first elastic means 11, by the additional elastic means 13, when the pressure along the additional piloting line 40 is lower than the calibration value V T , and by the pressure along the second piloting line 10.

[0080] It has in practice been ascertained that the described invention achieves the intended objects, and in particular, the fact is emphasized that the circuit covered by the present invention, wherein the valve means that control the flow of the work fluid towards the auxiliary utilities also integrate the control of the discharge of the work fluid in case of no or insufficient demand from the auxiliary utilities, is constructively simpler than the circuits of known type.

[0081] In particular, the fact that the valve means controlling the flow of the work fluid towards the auxiliary utilities also have a discharge position to convey the flow towards a discharge tank allows for higher compactness than within the circuits of known type, which instead involve several valve means which are separate from each other.

[0082] In addition, the presence of the additional elastic means and of the actuator element allows ensuring the proper supply of the auxiliary utilities and the discharge of the work fluid only when actually needed.

[0083] Last but not least, the circuit that is covered by the present invention allows minimizing the power losses in order to convey the flow of the work fluid towards the discharge tank.

Claims

1. Fluid-operated circuit (1) for the supply of primary and auxiliary utilities with predefined priorities comprising: - a variable displacement pump (2) adapted to deliver a pressurized fluid, where said pump (2) comprises a displacement regulating device (3); - at least one supply line (4) connected to at least said pump (2); - at least one primary line (5) communicating with said supply line (4) and connectable to a first utility (UP) with primary priority; - at least one auxiliary line (6, 6a, 6b) connectable to a relevant auxiliary utility (UA1, UA2) with lower predefined priority than said primary priority; - valve means (7) located between said supply line (4) and said at least one auxiliary line (6, 6a, 6b) and movable between at least one home position, wherein they stop the connection between said supply line (4) and said auxiliary line (6, 6a, 6b), and at least one work position, wherein they set said supply line (4) in communication with said at least one auxiliary line (6, 6a, 6b); - piloting means (8) of said valve means (7) comprising at least a first piloting line (9) communicating with said supply line (4) and operating on said valve means (7) to push them from the home position to the work position, a second piloting line (10) communicating with the utility (UP, UA1, UA2), between said first utility (UP) and said at least one auxiliary utility (UA1, UA2), having higher pressure and operating on opposite side of said first piloting line (9), and first elastic means (11) operating on said valve means (7) on the same side of said second piloting line (10); wherein said displacement regulating device (3) is operationally connected to said second piloting line (10) to regulate the displacement of said pump (2) so that the pressure along said first piloting line (9) is higher than the pressure along the second piloting line itself by a predefined value (VP); - a discharge line (12) connectable to a discharge tank (T); characterized by the fact that said valve means (7) are located between said supply line (4) and said discharge line (12); by the fact that said piloting means (8) comprise additional elastic means (13) operating on said valve means (7) in combination with said first elastic means (11); and by the fact that said valve means (7) are movable to at least one discharge position, wherein they set said supply line (4) in communication with said discharge line (12) at least when the force operating on said valve means (7) and depending on the pressure along said first piloting line (9) is greater than the force operating on the opposite side and depending on the action exerted by said first elastic means (11), by said additional elastic means (13) and by the pressure along said second piloting line (10).

2. Circuit (1) according to claim 1, characterized by the fact that said piloting means (8) comprise at least one actuator element (14) communicating with an additional piloting line (40) and adapted to pre-load said additional elastic means (13) when the pressure along the additional piloting line itself reaches a calibration value (VT) and by the fact that said valve means (7) are movable to the discharge position when the pressure along said additional piloting line (40) is lower than said calibration value (VT) and when the force operating on said valve means (7) and depending on the pressure along said first piloting line (9) is greater than the force operating on the opposite side and depending on the action exerted by said first elastic means (11), by said additional elastic means (13), when the pressure along said additional piloting line (40) is greater than said calibration value (VT), and by the pressure along said second piloting line (10).

3. Circuit (1) according to claim 1 or 2, characterized by the fact that said valve means (7) comprise at least one hollow body (15) defining a housing seat (16) provided with at least one supply port (17) communicating with said first piloting line (9), with at least one auxiliary port (18, 18a, 18b) communicating with said at least one auxiliary line (6, 6a, 6b), with at least one discharge port (19) communicating with said discharge line (12) and with at least one piloting port (20) communicating with said second piloting line (10), and comprise at least one distributor element (21) housed within said housing seat (16) in a sliding manner and movable to set said supply port (17) in communication with / isolate from said at least one auxiliary port (18, 18a, 18b) and / or said discharge port (19), wherein between said body (15) and said distributor element (21) is defined at least one first chamber (22) communicating with said supply port (17) and at least one second chamber (23) arranged on the opposite side of said first chamber (22) and communicating with said piloting port (20), said first elastic means (11) being housed within said second chamber (23) and interacting with said distributor element (21) to counteract the displacement from the home position towards the work position.

4. Circuit (1) according to claim 3, characterized by the fact that in the home position said distributor element (21) isolates said supply port (17) from said at least one auxiliary port (18, 18a, 18b) and from said discharge port (19), that in the work position it sets said supply port (17) in communication with said at least one auxiliary port (18, 18a, 18b), closing said discharge port (19), and that in the discharge position it sets said supply port (17) in communication with said discharge port (19).

5. Circuit (1) according to one or more of claims 2 to 4, characterized by the fact that said additional elastic means (13) are housed within said second chamber (23) and by the fact that said piloting means (8) comprise at least one abutment element (25) located between said distributor element (21) and said additional elastic means (13), said abutment element (25) displacing so as to counteract said additional elastic means (13) as a result of the interaction with said distributor element (21) during its displacement from the work position to the discharge position when the pressure along said additional piloting line (40) is higher than said calibration value (VT).

6. Circuit (1) according to claim 5, characterized by the fact that said additional elastic means (13) are located between said abutment element (25) and said actuator element (14).

7. Circuit (1) according to one or more of claims 3 to 5, characterized by the fact that said distributor element (21) travels a first stroke stretch (C1), counteracting said first elastic means (11), to displace from the home position to the work position, and travels a second stroke stretch (C2) to displace from the work position to the discharge position.

8. Circuit (1) according to claims 2 and 7, characterized by the fact that, when the pressure along said additional piloting line (40) is higher than said calibration value (VT), said distributor element (21) travels said second stroke stretch (C2) counteracting said additional elastic means (13) to displace from the work position to the discharge position.

9. Circuit (1) according to claim 8, characterized by the fact that said distributor element (21) interacts, at the end of said first stroke stretch (C1), with said abutment element (25), said distributor element (21) and said abutment element (25) moving locked together with each other along said second stroke stretch (C2).

10. Circuit (1) according to claim 2 and one or more of claims 7 to 9, characterized by the fact that, when the pressure along said additional piloting line (40) is lower than said calibration value (VT), said additional elastic means (13) are in the home configuration and said distributor element (21) travels said first stroke stretch (C1) and said second stroke stretch (C2) counteracting said first elastic means (11) by switching from the home position to the discharge position.

11. Circuit (1) according to one or more of claims 3 to 10, characterized by the fact that said valve means (7) comprise a stationary base element (24) associated with said body (15) and by the fact that said first elastic means (11) have one end resting on said base element (24) and the opposite end resting on said distributor element (21), the latter moving close to said base element (24), counteracting said first elastic means (11), in its displacement from the home position to the work position.

12. Circuit (1) according to one or more of claims 3 to 10, characterized by the fact that said abutment element (25) is located between said first elastic means (11) and said additional elastic means (13) and by the fact that said abutment element (25) moves counteracting said first elastic means (11) when the pressure along said additional piloting line (40) is higher than said calibration value (VT).

13. Circuit (1) according to one or more of claims 3 to 12, characterized by the fact that said actuator element (14) has an active area on which the fluid coming from said additional piloting line (40) operates.

14. Circuit (1) according to one or more of the preceding claims, characterized by the fact that said piloting means (8) comprise at least one control element (28) operationally connected to said actuator element (14) to counteract the displacement thereof along the pre-loading direction of said additional elastic means (13) until the pressure along said additional piloting line (40) reaches said calibration value (VT).

15. Circuit (1) according to claim 14, characterized by the fact that said control element (28) comprises second elastic means adapted to interact with said actuator element (14) to counteract the displacement thereof along the pre-loading direction of said additional elastic means (13), the active area of said actuator element (14) and the pre-load of said second elastic means (28) in the home condition defining said calibration value (VT).

16. Circuit (1) according to claim 14, characterized by the fact that said control element (28) comprises a sequence valve arranged along said additional piloting line (40) and calibrated to a pressure equal to said calibration value (VT).

17. Circuit (1) according to one or more of the preceding claims, characterized by the fact that said distributor element (21) has an active area on which the pressure of the work fluid coming from said first piloting line (9) operates, wherein said active area of the distributor element (21) is sized so that the force exerted thereon by a pressure of the work fluid equal to said predefined value (VP) is greater than the force exerted on the opposite side by said first elastic means (11).

18. Circuit (1) according to one or more of the preceding claims, characterized by the fact that said distributor element (21) has an active area on which the pressure of the work fluid coming from said first piloting line (9) operates, wherein said active area of the distributor element (21) is sized so that, when the pressure along said additional piloting line (40) is higher than said calibration value (VT), the resultant of the force exerted by said first elastic means (11) and by said additional elastic means (13) is greater than the force exerted by a pressure of the work fluid equal to said predefined value (VP) on the distributor element itself.

19. Circuit (1) according to one or more of the preceding claims, characterized by the fact that said distributor element (21) moves towards the home position when the pressure difference between said first piloting line (9) and said additional piloting line (40) is lower than said predefined value (VP).

20. Circuit (1) according to claim 1, characterized by the fact that said additional elastic means (13) are pre-loaded and by the fact that said piloting means (8) comprise at least one actuator element (14) communicating with an additional piloting line (40) and adapted to unload said additional elastic means (13) when the pressure along the additional piloting line itself reaches a calibration value (VT) and by the fact that said valve means (7) are movable to the discharge position when the pressure along said additional piloting line (40) is higher than said calibration value (VT) and when the force operating on said valve means (7) and depending on the pressure along said first piloting line (9) is greater than the force operating on the opposite side and depending on the action exerted by said first elastic means (11), by said additional elastic means (13), when the pressure along said additional piloting line (40) is lower than said calibration value (VT), and by the pressure along said second piloting line (10).

21. Circuit (1) according to one or more of the preceding claims, characterized by the fact that said additional piloting line (40) corresponds to said second piloting line (10).

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