HYDRAULIC DISTRIBUTOR WITH PRESSURE COMPENSATOR FOR DIRECTIONAL VALVES

Abstract

A hydraulic distributor includes at least one main spool configured to define a delivery branch, and a discharge branch, a feed branch and a pressure compensator configured such that a local pressure acts on a first side thereof and a maximum Load Sensing pressure acts on a second side characterizing either the working pressure of the hydraulic section, in the case in which there is only one hydraulic section, or, in the case in which there is a plurality of hydraulic sections, each one defining a respective characteristic pressure, of the maximum pressure among the characteristic pressures of the hydraulic sections. The pressure compensator is arranged such as to respectively intercept said delivery branch and said discharge branch.

Claims

1. Hydraulic distributor comprising: at least one main spool for actuating a hydraulic section, for example a hydraulic actuator, said spool being configured to define a delivery branch and a discharge branch; a feed branch configured so as to supply a flow rate of an operating fluid at a working pressure to the delivery branch for actuating the hydraulic section; a pressure compensator configured such that a local pressure taken at the delivery branch acts on a first side thereof and a maximum Load Sensing pressure acts on a second side opposite to said first side characterizing either the working pressure of said hydraulic section, in case there is only one hydraulic section, or, in case there is a plurality of hydraulic sections, each one defining a respective characteristic pressure, the maximum pressure among said characteristic pressures of the hydraulic sections, wherein said pressure compensator is arranged so as to intercept respectively said delivery branch and said discharge branch.

2. Hydraulic distributor according to claim 1, wherein both said delivery branch and said discharge branch are simultaneously intercepted by said pressure compensator.

3. Hydraulic distributor according to claim 1, wherein said pressure compensator comprises a continuous-positioning spool.

4. Hydraulic distributor according to claim 1, wherein said pressure compensator comprises four ways.

5. Hydraulic distributor according to claim 4, wherein said pressure compensator comprises a further way configured to connect said discharge section with an energy recovery section connectable to an energy recovery device.

6. Hydraulic distributor according to claim 1, wherein said pressure compensator comprises an elastic element acting on said first side.

7. Hydraulic distributor according to claim 1, wherein said pressure compensator comprises respective passageways for said delivery branch and said discharge branch, said passageways being configured such as to define a passage port of the delivery branch and a passage port on the discharge branch, the passage port of the delivery branch and/or of the discharge branch being variable according to the stroke of a continuous-positioning spool of said pressure compensator.

8. Hydraulic distributor according to claim 7, wherein said passageways are configured such that said passage port on the discharge branch has a smaller surface area than said passage port defined on the delivery branch.

9. Hydraulic distributor according to claim 1, wherein said local pressure is taken at a primary section of the delivery branch located downstream of said spool and upstream of said pressure compensator.

10. Hydraulic distributor according to claim 9, wherein said delivery branch comprises a secondary section further connecting said pressure compensator with said spool, said compensator being interposed between said primary section and said secondary section.

11. Hydraulic distributor according to claim 1, wherein said compensator is arranged immediately downstream of said main spool along said delivery section and along said discharge section.

12. Hydraulic distributor comprising: at least one main spool for actuating a hydraulic section, for example a hydraulic actuator, said spool being configured to define a delivery branch and a discharge branch; a feed branch configured so as to supply a flow rate of an operating fluid at a working pressure to the delivery branch for actuating the hydraulic section; a pressure compensator configured such that a local pressure taken at the delivery branch acts on a first side thereof and a maximum Load Sensing pressure acts on a second side opposite to said first side characterizing either the working pressure of said hydraulic section, in case there is only one hydraulic section, or, in case there is a plurality of hydraulic sections, each one defining a respective characteristic pressure, the maximum pressure among said characteristic pressures of the hydraulic sections, an energy recovery section that can be connected to an energy recovery device, wherein said pressure compensator is arranged so as to intercept respectively said delivery branch and said discharge branch by respective ways and comprises a further way configured to connect said discharge section with an energy recovery section.

13. Hydraulic distributor according to claim 12, wherein said compensator is arranged immediately downstream of said main spool along said delivery section and along said discharge section.

14. Hydraulic distributor according to claim 12, wherein said pressure compensator comprises respective passageways for said delivery branch and said discharge branch, said passageways being configured such as to define a passage port of the delivery branch and a passage port on the discharge branch, the passage port of the delivery branch and/or of the discharge branch being variable according to the stroke of a continuous-positioning spool of said pressure compensator and wherein said passageways are configured such that said passage port on the discharge branch has a smaller surface area than said passage port defined on the delivery branch.

15. Hydraulic distributor according to claim 12, wherein said pressure compensator is configured to simultaneously intercept both said delivery branch and said discharge branch.

16. Hydraulic distributor comprising: at least one main spool for actuating a plurality of hydraulic sections, for example a hydraulic actuator, said spool being configured to define a delivery branch and a discharge branch; a feed branch configured so as to supply a flow rate of an operating fluid at a working pressure to the delivery branch for actuating said plurality of hydraulic sections, each one defining a respective characteristic pressure; a pressure compensator configured such that a local pressure taken at the delivery branch acts on a first side thereof and a maximum Load Sensing pressure acts on a second side opposite to said first side, said maximum Load Sensing pressure being characterizing of the maximum pressure among said characteristic pressures of the hydraulic sections, an energy recovery section that can be connected to an energy recovery device, wherein said pressure compensator is arranged so as to intercept simultaneously said delivery branch and said discharge branch.

17. Hydraulic distributor according to claim 16, wherein said pressure compensator comprises four ways.

18. Hydraulic distributor according to claim 17, wherein said pressure compensator comprises a further way configured to connect said discharge section with an energy recovery section connectable to an energy recovery device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] This and other features will be more apparent from the following description of some embodiments illustrated purely by way of example in the accompanying drawings, in which:

[0046] FIG. 1 is a schematic illustration of a hydraulic distributor according to the present invention in an exemplary embodiment in which two working sections are provided;

[0047] FIG. 2 is a schematic illustration of a hydraulic distributor according to an exemplary embodiment in which a single working section is present and energy recovery logics are not used;

[0048] FIG. 3 is a schematic illustration of a hydraulic distributor according to a further exemplary embodiment in which a single working section is present and an energy recovery function is provided; and

[0049] FIGS. 4a, 4b, 4c are graphs illustrating the ratio between the stroke of the compensator and the passageways surface of the compensator in different configurations of the compensator.

DETAILED DESCRIPTION OF THE INVENTION

[0050] Referring initially to FIG. 1, a hydraulic system comprising a hydraulic distributor 100 according to the present invention is illustrated as a whole with the number 10.

[0051] The hydraulic system 10 is intended to actuate one or more hydraulic sections U1, U2, . . . , Un and comprises a feed group 20 intended to supply a flow rate of operating fluid for actuating these hydraulic sections.

[0052] The feed group 20 may be of the variable flow rate or pressure type, like in the embodiment example illustrated in the figure. However, solutions may be provided in which other solutions for adjusting the feed group 20 may be used.

[0053] In some embodiments, the feed group 20 may comprise a variable displacement pump that adjusts the flow rate based on the pressure characteristic of the higher pressure section among those fed by the feed group. The example in FIG. 1 illustrates the hydraulic system 10 in the case where the feed group 20 is intended to feed two hydraulic sections U1, U2. It should be noted that there can still be an even larger number of sections, as indicated above.

[0054] In the example represented in FIG. 1, the two sections U1, U2, are for example formed by double-acting hydraulic actuators. The hydraulic section U1 can however be represented by the actuation of any other hydraulic equipment. It will in fact be appreciated that the same inventive concepts set forth in connection with the present invention are also applicable to other solutions, like a hydraulic motor. For this reason, hereafter the term “hydraulic section” will be used to refer to any hydraulic equipment intended to be actuated by means of a hydraulic circuit with one or more working sections.

[0055] The feed group 20 is intended to supply the fluid required for the actuation of these actuators, which is supplied to them by means of the distributor 100. In the hydraulic system 10, a direct tank branch is also defined, generically denoted by T, in which the operating fluid being discharged from the sections flows.

[0056] In preferred embodiments, an energy recovery device 30 is also provided towards which the distributor 100 can direct part of the operating fluid in ways that will be described in more detail below.

[0057] Still with reference to the example illustrated in FIG. 1, the distributor 100 comprises a feed branch 1 connected to the feed group 20 and through which the fluid flow rate is directed to the individual sections of the distributor 100.

[0058] It will be appreciated that the distributor 100 may have a plurality of working sections 101, each one intended to actuate a respective hydraulic section U1, . . . , Un.

[0059] In the embodiment illustrated in FIG. 1, the distributor 100 comprises two working sections 101, 102, connected to a respective actuator or more generally to a respective hydraulic section U1, U2.

[0060] Preferably, each of the sections 101, 102 comprises a spool 2 for actuating the hydraulic section U1, U2 and a pressure compensator 3, the operating characteristics of which will be better illustrated below.

[0061] For the sake of illustrative simplicity, the invention will still be illustrated below in the case of a single section 101, like in the example of FIG. 2. Again, for the sake of greater illustrative simplicity, in the embodiment example of the figure there are no energy recovery functions.

[0062] As can be observed, the spool 2 defines a delivery branch 11, connected to the feed branch 1, and a discharge branch 12, connected to the discharge T.

[0063] Preferably, the spool 2 intercepts the delivery branch 11 defining a primary section 11A that connects the spool 2 to the pressure compensator 3.

[0064] As will be better illustrated below, compensator 3 is intended to compensate for the pressures present in the system as a function of the position of a continuous-positioning spool thereof.

[0065] According to some embodiments, the pressure compensator 3 is of the four-way type.

[0066] A first way 3a and a second way 3b intercept the delivery branch 11. The first way 3a is in particular connected to the primary section 11A, while the second way is connected to a secondary section 11B of the delivery branch 11, which brings the flow rate of operating fluid back to the main spool 2 after passing through the compensator 3.

[0067] This flow rate of operating fluid can then be sent to the hydraulic section Un, by actuating it in one direction or in the opposite one depending on the position of the main spool 2. For this purpose, a first connection section 21 and a second connection section 22 can be provided in the section 101, to which the spool 2 sends the flow rate supplied by the secondary section 11B, or more generally by the delivery branch 11, depending on the positioning of the spool 2.

[0068] During the actuation of the hydraulic section, one between the first and the second connection branch supplies the flow rate of fluid in delivery and the other receives the fluid in discharge once the required hydraulic work has been performed.

[0069] This fluid is again passed in the spool 2 which sends it to the discharge branch 12 of the section.

[0070] The discharge branch 12 is also intercepted at the outlet of the spool 2 by the compensator 3. Therefore, two further ways 3c and 3d of the compensator are connected to the discharge branch 12, defining a main section of the discharge branch 12A, which connects the spool 2 to the compensator 3, and an auxiliary section 12B, which connects the compensator to the discharge T.

[0071] As previously illustrated, the compensator 3 allows to choke the passage of the fluid both in the delivery and in the discharge.

[0072] In other words, the passageways 3a, 3b, 3c, 3d are configured such to define a passage port of the delivery branch and a passage port of the discharge branch.

[0073] Advantageously, the passage of fluid is choked simultaneously at the delivery and discharge.

[0074] These passage ports can be choked according to the stroke of the spool of the compensator 3.

[0075] In this regard, FIGS. 4A, 4B and 4C illustrate the variation of the surface of the passage ports as a function of the stroke of the spool of the compensator in various embodiments.

[0076] In a preferred embodiment, schematically shown in FIG. 4A, the passageways 3a, 3b, 3c, 3d are configured such that the passage port on the discharge branch 13 has a smaller surface area than said passage port defined on the delivery branch 11.

[0077] In this case, assuming that the delivery and discharge flow rates are the same (section/actuator with equal areas), the compensation will mainly occur on the discharge branch, but the portion of compensation on the delivery branch can help reduce the undesirable effects of increased pressures and system instability.

[0078] Different sizings of the ports advantageously allow to obtain different behaviors in the compensator and in general in the system.

[0079] FIGS. 4B and 4C illustrate in fact the borderline cases in which the variation of the port on the delivery branch is respectively eliminated or the variation of the port on the discharge branch is completely eliminated. It will therefore be appreciated that the system of the present invention allows by means of simple structural modifications to achieve different operational solutions, thus providing a high degree of versatility.

[0080] In order to achieve the compensation required by the system, the pressure compensator 3 is advantageously configured such that a local pressure Ploc taken at the delivery branch 11 acts on the first side 31 thereof and a maximum Load Sensing pressure PLSmax acts on the second side 32, opposite to the first side 31.

[0081] Preferably, the local pressure PLoc is taken at a primary section 11A of the delivery branch 11 located downstream of said spool 2 and upstream of said pressure compensator 3. Preferably the pressure is taken immediately upstream of the compensator 3, i.e. there are no hydraulic components interposed between the point where the pressure PLoc is taken and the compensator 3.

[0082] In some embodiments, a spring, or other equivalent elastic element 33 further acts on the side 31 in addition to the local pressure PLoc.

[0083] With regard to the pressure PLSmax, in the case in question, in which there is only one hydraulic section, this pressure corresponds to the pressure characteristic of the working pressure of the hydraulic section U1. On the other hand, in the case in which there is a plurality of hydraulic sections U1, . . . Un, the pressure PLSmax corresponds to the maximum Load Sensing pressure among all those characterizing the hydraulic sections present. This pressure is taken at a Load Sensing branch 14 which supplies the Load Sensing signal to the feed group 20.

[0084] In this regard, it will be appreciated that in the context of the present invention, the term Load Sensing pressure is used to indicate the characteristic pressure value of each section which is sent to the feed group 20 to adjust the flow rate in the system, e.g. by adjusting the pump displacement.

[0085] Therefore, the maximum Load Sensing pressure determined by the operating conditions of each section U1, . . . , Un acts on the side 32.

[0086] Thanks to this configuration, the compensator 3 can therefore make a continuous adjustment based on the actual operating conditions of the system, shifting the spool, and thus compensating for the flow rates, so as to maintain the system in a condition of dynamic equilibrium.

[0087] An alternative embodiment of the distributor of the present invention is represented in FIG. 3.

[0088] In such embodiments, the energy recovery function is further envisaged in the system.

[0089] For this purpose, the pressure compensator 3 comprises a further way 3e configured so as to connect the discharge section 12 with an energy recovery section 13 that can be connected to the energy recovery device 30.

[0090] Depending on the operating conditions, the operating fluid may be sent to the discharge T or to the energy recovery device 30.

[0091] These conditions are transmitted to the compensator by means of the pressures PLoc and PLSmax, which will move into a position such as to open, partialize or close the further way 3e if the flow rate and pressure conditions are suitable to allow an energy recovery. For example, in the case of a dragging load acting on the hydraulic section, the difference between PLoc and PLSmax is likely to be such that the spool of the compensator is shifted so that the passageway towards the discharge is closed and the flow is partially or entirely diverted towards the recovery device 30.

[0092] It will be appreciated that although such an energy recovery solution has been described in relation to a single section it will be possible to apply these concepts also to other embodiments, for example formed by a plurality of sections.

[0093] It will therefore be appreciated that the circuit of the present invention allows the compensation and energy recovery functions to be realized effectively, with a high degree of versatility and efficiency in handling the different operating conditions.