HYDRAULIC DISTRIBUTOR WITH COMPENSATION DEVICE FOR DIRECTIONAL VALVES

Abstract

An open-center valve device for operating machines includes: a first section and a second section, a high-pressure line configured in such a way as to be connected to a pump to supply an operating fluid flow rate to the sections, and a discharge line configured to be connected to an outlet of the operating fluid. Each of the sections includes a spool control element, configured in such a way as to send the fluid flow rate to the respective work ports. The valve device further includes one or more free flow segments, a series duct configured in such a way that, upon a movement from the neutral position of one of the control elements for operating one of the actuators, a return flow rate from a respective work port is supplied to a subsequent control element, progressively closing the respective free flow passage.

Claims

1. An open-center valve device for operating machines comprising: a first section and a second section, the sections being configured to be connected to respective pairs of work ports to operate a respective actuator of the operating machine, a high-pressure line configured in such a way as to be connected to a pump to supply a flow rate of an operating fluid to the sections, and a discharge line configured to be connected to an outlet for the operating fluid, each of the sections comprising a spool control element, configured in such a way as to send the flow rate to the respective work ports, the valve device further comprising: one or more free flow segments configured in such a way as to define a free flow line connecting in successive sequence each of the control elements, each of the control elements including a free-circulation passage configured in such a way that, when all the control elements are in a neutral position, the high-pressure line is connected to the discharge line without sending the flow rate to the work ports, a series duct configured in such a way that, upon a movement from the neutral position of one of the control elements for operating one of the actuators, a return flow rate from a respective use is supplied to a subsequent control element, progressively closing the respective free flow passage, the control elements comprising respective return passages configured to receive the return flow rate, respective non-return valves being provided downstream of the return passages of the control elements and upstream of the series duct, wherein at least one of the control elements comprises at least one bypass passage, the control device being configured in such a way that, when the control device is in the neutral position, the bypass passage is closed and, when the control device is moved from the neutral position to operate the respective actuator, the control device progressively puts the bypass passage into communication with the outlet via the discharge duct or a low-pressure line directly connected to the outlet.

2. The valve device according to claim 1, wherein the section comprises a return line configured in such a way that, when one of the control elements is moved from the neutral position to operate the respective actuator, the return flow rate from the driven actuator is fed to the respective return passage.

3. The valve device according to claim 2, further comprising a bypass duct, the bypass duct being arranged as a bypass to the return line in such a way as to bring the return flow rate to the bypass passage in parallel with the return passages.

4. The valve device according to claim 3, further comprising a maximum pressure valve arranged along the bypass duct.

5. The valve device according to claim 1, further comprising a two-way sequence slide valve through which the return flow rate is discharged.

6. The valve device according to claim 5, wherein the sequence slide valve is formed outside the control element.

7. The valve device according to claim 5, wherein the slide valve is normally closed and defines respective opposite ends, a pressure signal taken from a reduced pressure line acting on a first end, the reduced pressure being lower than the pressure of the high-pressure line, and a spring and a decoupled reduced pressure, which is decoupled by a throttle with respect to the pressure existing on the first end of the slide valve, acting on a second end, opposite to the first end.

8. The valve device according to claim 7, wherein the second connected end is connected to the bypass passage through an additional duct.

9. The valve device according to claim 7, wherein the reduced pressure line is configured to pilot respective spools of the control elements.

10. The valve device according to claim 5, wherein the slide valve defines respective opposite ends, a pressure existing in a duct derived from the return passage upstream of the non-return valve acting on a first end and a spring and a pressure, which is decoupled by a throttle with respect to the pressure existing on the first end of the slide valve, acting on a second end, opposite to the first end.

11. A hydraulic system comprising a pump and a valve device according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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:

[0047] FIG. 1 is a schematic illustration of a valve device and the related hydraulic system made according to the present invention in a first embodiment;

[0048] FIG. 2 is a schematic illustration of a valve device and the related hydraulic system made in accordance with a second embodiment of the present invention;

[0049] FIG. 3 is a schematic illustration of a valve device and the related hydraulic system made in accordance with a third embodiment of the present invention;

[0050] FIG. 4 is a schematic illustration of a valve device and the related hydraulic system made in accordance with a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Referring initially to FIG. 1, an open-center valve device in accordance with the invention is illustrated overall with the reference number 3.

[0052] The valve device 3 is inserted in the context of a hydraulic system 100 of an operating machine.

[0053] The hydraulic system 100 comprises a fixed displacement pump 1, which can be connected to the valve device 3. The connection occurs through a high-pressure line 2.

[0054] In the attached figures, the valve device is depicted by way of example with three generic sections E1, E2 and E3, each of which controls a related actuator of the operating machine of the work ports A1, B1, A2, B2, A3 and B3.

[0055] Each section E1, E2, E3 comprises at least one spool control element C1, C2, C3 therein.

[0056] When the spools are not operated and are in the neutral position, the fluid from the high-pressure line 2 passes through free-circulation passages LC1, LC2 and LC3 along a free flow duct 6 and is sent to the outlet T through the duct 5.

[0057] Advantageously, the free flow duct 6 is split into separate segments 61, 62, 63 which connect the control elements of each section.

[0058] When a control element C1 or C2 is operated, the high-pressure line 2 is selectively put into communication with the work ports A1, B1, A2, B2, A3 and B3 and actually manages the actuators of the operating machine in which the control valve device is inserted.

[0059] Such a configuration defines delivery passages MA1, MA2, MA3, MB1, MB2 and MB3 on the respective control element.

[0060] The work port B1, A1, B2, A2, B3 and A3 selectively not put in communication with the high-pressure line 2 is connected to the next segment of the free flow duct 61, 62 and 63 through series ducts 71, 72.

[0061] Such a connection defines respective return passages TA1, TA2, TA3, TB1, TB2 and TB3 on the control element.

[0062] The free-circulation passage LC1, LC2 and LC3 defined on the control element is closed upon the operation of the control element when the relative spool is moved from the neutral position. Thereby, operating several spools simultaneously, only the first one operated directly feeds the work ports by directly putting the high-pressure line in communication with one work port at a time. The one which is not in communication with the high-pressure line 2 in the same section feeds a respective series duct 71, 72, which returns the fluid along the free-flowing segment of the next section.

[0063] The next operated control element which intercepts the free circulation line, since if operated it closes the passage LC and selectively puts the work ports connected thereto in communication with the previously mentioned series ducts and free flow segment, and is in fact fed by the non-fed work port of the previous operated section.

[0064] Only in the last operated control element is the selectively non-fed work port put in communication with the outlet T.

[0065] Inside the control elements C1, C2 and C3 before the intersection with the series ducts 71, 72 downstream of the return passages TA1, TA2, TB1, TB2, non-return valves VA1, VA2 and VB1, VB2 are inserted to prevent back flow to the work ports in the event of overpressure or limit switch of the work ports operated downstream of said series ducts.

[0066] In order to optimize the size of said valves, the corresponding cavities are made inside the spools themselves.

[0067] When said non-return valves close, they block the movement of the sections operated upstream of said valves.

[0068] The present invention advantageously allows a passage to be provided which allows to discharge the channels defined between the return passages TA1, TA2, TB1 and TB2 and the non-return valves themselves.

[0069] For this reason, as shown in FIG. 1, one or more additional passages 8 are inserted along the control element, connected in bypass with the duct comprised between the discharges TA1, TA2, TB1 and TB2 and the non-return valves VA1, VB1, VA2 and VB2 themselves. For the sake of simplicity, only one passage 8 is shown in the figure, which is connected in bypass to the discharge TA1 upstream of VA1 through a bypass duct 81.

[0070] In the neutral condition of the spool of the control element C1, the passage 8 is not in communication with any other ducts if not with the bypass duct 81. When the spool of the control element C1 is operated, an additional channel 82 opens through the control element which, as the stroke of the spool changes, progressively puts the control element in communication with the outlet T of the system through the duct 5.

[0071] FIG. 2 shows a second embodiment of the invention in which a maximum pressure valve 9 is inserted along the bypass duct 81.

[0072] The maximum pressure valve is therefore also in bypass from the passage return line TA1 upstream of the non-return valve VA1 before the bypass passage 8. Said passage is therefore located in the portion 83 of the duct 81 downstream of valve 9. This valve allows the discharge to intervene on the series as described in relation to the previous embodiment, but only upon reaching a certain intervention pressure threshold.

[0073] FIG. 3 shows a third embodiment of the invention, if the flow rate value to be discharged along the series of the first section is greater with respect to the two previous cases.

[0074] In the present embodiment, the flow rate is discharged by means of a suitably dimensioned two-way two-position sequence slide valve 4, which is not obtained directly along the spool seat of the control element.

[0075] The bypass passage 8, which was previously used to manage the flow rate discharge, is now only used to manage the switching signal of said discharge slide valve. Based on the pilot signals received, the slide valve opens a passage along the channel TA1 towards the outlet T

[0076] The slide valve is normally closed. At the end of the slide valve, on a first end 41 there is the pressure signal of the reduced pressure line V (which can also be used to pilot the spools), a spring 43 and the reduced pressure V1 decoupled by a throttle 44 with respect to the pressure present on the first end of said slide valve acting on the opposite side on the end 42.

[0077] Advantageously, this latter end 42 is connected to the previously made passage 8 by means of a control duct 48: through the spool C1 of the distributor section, said end can be put in communication with the discharge line T by means of the passage 82 and the duct 5. When the control element is not operated, the connection 82 with the outlet is closed, and consequently the pressure at the ends of the slide valve is the same, V1 is equal to V, and the spring 43 holds the sequence slide valve 4 in the closed condition.

[0078] By operating the control element, the pressure on the spring side 42 is progressively discharged, the pressure drop generated by the throttle 44 progressively decouples the pressures V1 and V. As soon as the pressure V exceeds the sum of the force exerted by the spring 43 and the pressure V1, the slide valve moves from the normally closed position towards an open position and allows to discharge the series channel TA1 of the first control section as in the previous solutions upstream of the non-return valve VA1.

[0079] Through the duct 49 taken as a bypass from TA1, a passageway 45 opens towards the discharge line 5 connected to the outlet T.

[0080] FIG. 4 illustrates a fourth embodiment of the invention, in which a slide valve similar to that of the previous invention is used.

[0081] In this case, at the ends of the slide valve 4, it is no longer pilot pressure V that acts, but the pressure itself present in the series channel psr.

[0082] The operating principle is the same as in the previous case: at the ends of the slide valve 4, there is the pressure psr present in the duct 49 taken in bypass from the passage TA1 before the non-return valve VA1 acting on a first end 41, a spring 43 and the pressure psr1 decoupled by a throttle 44 with respect to the pressure present on the first end of said slide valve acting on the opposite end 42.

[0083] This last end 42 is connected with the previously made recess 8 by means of the duct 48: through the control element C1 of the distributor section, said end can be put in communication with the discharge line T by means of the passage 82 and the duct 5. When the control element is not operated, the connection 82 with the outlet is closed, and consequently the pressure at the ends of the slide valve is the same, psr1 is equal to that of psr and the spring 43 holds the sequence slide valve 4 in the closed condition.

[0084] By operating the control element, the pressure on the spring side 42 is progressively discharged, the pressure drop generated by the throttle 44 progressively decouples the pressures psr1 and psr. As soon as the pressure psr is greater than the sum of the force of the spring 43 and the pressure psr1, the slide valve moves from the normally closed position to an open position and allows the discharge of the series channel TA1 of the first control section as in the previous solutions upstream of the non-return valve VA1.

[0085] Through the duct 49 taken as a bypass from TA1, a passageway 45 opens towards the discharge line 5 connected to the outlet T.

[0086] What has been described in the previous solutions has, for the sake of descriptive simplicity, only been included on one of the work ports and in the first section, the findings of the invention are to be understood as achievable on both work ports and on several sections of the system in series, not necessarily and only the first control section of the control valve.