Open-centre valve device for operating machines

Abstract

An open-centre valve device for heavy equipment machines comprises a first section and a second section connected to respective pairs of work ports, a high-pressure line and a discharge line. Each of said sections comprises a spool control element. The valve device further includes one or more free flow segments and a series duct. At least one of said sections comprises at least one branching duct which connects a respective series duct with said discharge or to a low-pressure line independent of said discharge. A pressure valve is arranged along the branching duct, said pressure valve being normally closed and configured in such a way as to open upon reaching a certain pressure in said branching duct in such a way that the fluid flowing in said series duct is primarily sent to said discharge or said low-pressure line. Said valve device further comprises a non-return valve arranged along said series duct downstream of a branching point at which said branching duct connects to said series duct.

Description

[0001] D E S C R I PT I O N

[0002] TITLE: OPEN-CENTRE VALVE DEVICE FOR OPERATING MACHINES

[0003] FIELD OF APPLICATION

[0004] The present invention relates to a valve device for an operating machine and a hydraulic system comprising the same.

[0005] TECHNOLOGICAL BACKGROUND

[0006] A typical example of an operating machine comprises a boom crane, a bucket, a hydraulic cylinder of the boom crane configured to actuate the boom crane, a hydraulic cylinder of the bucket configured to actuate the bucket, and one or more auxiliary actuators configured to actuate auxiliary attachments.

[0007] The respective hydraulic cylinders are actuated by respective sections of a control valve present in the hydraulic circuit of the operating machine.

[0008] For example, a first section can be configured to control the lengthening and shortening of the boom crane cylinder, a second section of the control valve configured to control the lengthening and shortening of the bucket cylinder, and a third section of the control valve configured to actuate the auxiliary actuator.

[0009] Typically these sections are provided with relative spool valves and when the spool of the first section of the control valve is not actuated, the hydraulic oil sent by the pump passes through the interior of the spool itself and is supplied to the second section of the valve and, through the spool valve of the latter, to the successive sections.

[0010] This constructive solution of the valve is referred to in the jargon as "free flow LC" passage.

[0011] When the spool of the first control section is actuated, the hydraulic oil returning from the boom crane cylinder of the first control device passes again through the first control section and is used to feed the second control section and the successive sections.

[0012] This type of hydraulic circuit is referred to as a "series circuit".

[0013] One of the known problems of the series circuit occurs in the case of simultaneous actuation of several hydraulic cylinders.

[0014] For example, when the first section of the control valve (e.g. boom crane cylinder) and the second section of the control valve (e.g. bucket cylinder) are actuated at the same time, the operation could deteriorate. In particular, if the cylinder controlled by the second control section reaches its end of travel, two undesirable functional anomalies can occur.

[0015] The first anomaly is the pressurization of the series channel between the first and second control section and therefore of the cylinder chamber opposite the connection with the feed line which, by means of the differential areas of the cylinder itself, can lead to an unwanted movement in the opposite direction. According to the state of the art, said problem is partly solved by the use of nonreturn valves along the series duct of the first control section to avoid return flows along the series channel itself and the reversal of the motion direction of the cylinder with respect to that defined by the user.

[0016] A second anomaly, which occurs when the end of travel of a controlled work port is reached by a control section, leads to the stop of the cylinders actuated by sections preceding the same one which has reached the end of travel, until the spool of the latter section is at least returned to the neutral position, reopening the previously mentioned free flow channel LC. This can result in some difficulty for the operator and, in general, a feeling of poor manoeuvrability during the use of the operating machine. Patent US11255353B2 describes a solution to overcome the aforementioned problems.

[0017] This document envisages the introduction of a spool control element which opens an area of passage towards the discharge along the series line upstream of the non-return valve in such a way that, if during a simultaneous movement the non-return valve of a cylinder, which reaches the end of travel, by closing the passage along the series line itself, would actually block the movement of one of the cylinders connected to a control spool which is actuated upstream of the latter, the opening of said series channel towards the discharge allows the disposal of a flow rate, restoring the movement of the cylinder upstream of the series duct itself.

[0018] This solution requires the creation of a constricted passage on the spool between the series and discharge recess in order to open a passage upstream of the non-return valve. The limitation is that the size of this constricted passage on the one hand must be large enough to guarantee an adequate residual speed of the cylinder when the cylinder of the downstream controlled section reaches the end of travel, on the other hand it must be small enough to limit the dispersion discharging the flow rate during normal operation, with a consequent reduction in the series function and of the speed of the downstream controlled cylinder. It is therefore evident that this solution represents a compromise between two conflicting needs, involving on average high pressure drops, unsatisfactory cylinder speeds and the impossibility of excluding the passage to the benefit of the simultaneity of the actuations.

[0019] US 10 947 700 B2 describes a further example of a hydraulic system. Specifically, the hydraulic system comprises a pump, a first actuator, a second actuator, a first and a second control valve. There is also provided a constricted section located at a return pipe.

[0020] The need is therefore felt to improve the state-of-the-art solutions in the multi-section hydraulic circuits with series and free flow structure.

[0021] SUMMARY OF THE INVENTION The technical problem underlying the present invention is to make available a valve device that is structurally and functionally conceived to overcome, at least in part, one or more of the limitations disclosed above with reference to the mentioned prior art.

[0022] In the context of such a technical problem, an aim of the present invention is to provide the art with a valve device and a hydraulic system comprising the same capable of improving the operating feel of a hydraulic actuator and maintaining controllability during the execution by the operator of all the movements of the operating machine itself.

[0023] A further aim of the invention is to provide a valve device and a hydraulic system which improve the known solutions within the framework of a rational and relatively low-cost solution.

[0024] This problem and at least one of these aims are at least partially achieved by the invention, a valve device and by a hydraulic system comprising one or more of the features of the invention disclosed in the independent claims, as well as by the invention as defined by one or more of the following aspects.

[0025] The present invention refers to an open-centre valve device for heavy equipment machines comprising a first section and at least a second section configured to be connected to respective pairs of work ports to actuate an actuator of the operating machine.

[0026] Preferably the valve device comprises a high-pressure line configured in such a way as to be connected to a pump to supply a flow rate of operating fluid to said sections.

[0027] Preferably, the valve device further comprises a discharge line configured in such a way as to be connected to a discharge of said operating fluid.

[0028] Each of said sections preferably comprises a spool control element, configured in such a way as to send the flow rate of fluid to the respective delivery work port connected to the respective cylinder and in such a way as to receive through the respective return work port the flow rate of fluid returning from the cylinder itself.

[0029] Preferably, the valve device further comprises one or more free flow segments configured in such a way as to define a free flow line that joins said control elements in successive sequence.

[0030] Each of said control elements preferably includes a free flow passage configured in such a way that, when all said control elements are in a neutral position, the high-pressure line is connected to said discharge line without sending flow rate to the work ports.

[0031] The valve device further comprises a series duct.

[0032] Preferably, the series duct is configured in such a way that, upon a movement from the neutral position of one of said control elements for the actuation of one of said actuators, it directs a return flow rate from a respective work port by supplying it to a successive control element, progressively closing the respective free flow passage.

[0033] Preferably at least one of the sections comprises at least one branching duct which connects a respective series duct to the discharge. Alternatively, the branching duct may connect the series duct to a low-pressure line independent of the discharge.

[0034] A pressure valve is advantageously arranged along said branching duct. The pressure valve is normally closed and configured in such a way as to open upon reaching a certain pressure in said branching duct in such a way that the fluid flowing in the series duct is primarily sent to said discharge or said low-pressure line. A non-return valve, which is configured to prevent the return of the fluid, i.e. the passage of the fluid from the series duct towards the control element, is preferably inserted on the series duct.

[0035] It will therefore be appreciated that in the invention, at least one of said control elements comprises at least one return flow branching duct along the series duct, which connects to the series duct preferably at a branching point, upstream of the non-return valve mentioned above, along which the pressure valve is inserted. Preferably, said return flow branching is made in a portion of the circuit placed downstream of the spool control element and directly upstream of the nonreturn valve positioned along the first segment of the series channel.

[0036] The force of a spring acts on one side of said normally closed valve and, on the other side, the pressure present in said branching of the return flow acts on a first driving area. According to another aspect, as shown in a second embodiment, the pressure signal derived from the respective delivery work port, opposite to the return work port itself, acts on a second driving area. The two driving areas placed on the same end of the valve are not necessarily the same.

[0037] Advantageously, once the pressure on the driving area of the valve (or on the areas) is sufficient to open the passage through the valve itself overcoming the force of the opposed spring, the return flow is put in communication with the discharge line S or with a low-pressure line independent of the discharge itself T.

[0038] In some embodiments, the spool control element also manages two independent connections, defined below as distinct segments, between the return branches of the respective work ports and the first segment of the series duct.

[0039] Preferably, the first part of said series duct defines the two independent segments on which a non-return valve is inserted for each segment. Advantageously, the non-return valve is placed upstream of the segment of the series duct itself, in a position in which said independent segments merge into a single channel.

[0040] According to one aspect of the invention, on the pressure valve placed along the aforementioned branching duct there is only one driving area whose operating pressure is the same present on said portion of the series duct on which said branching duct is made. As will be seen in greater detail below, there may be two independent valves for each of said independent segments of said first parts of the series channel.

[0041] According to a second aspect, on the pressure valve located along the branching duct, a second driving area is made, on which the pressure signal present on the respective branch connected to the opposed delivery line on the cylinder to the return branch that feeds the series duct acts.

[0042] According to a third aspect, the non-return valve is inserted along the series duct along the segment of the same where said independent segments have been merged into a single channel. In this solution there is therefore a single branching passage of the return flow along which only one pressure valve is inserted.

[0043] Further preferred aspects are also defined in the appended claims as well as by the following description.

[0044] 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 non-limiting example in the accompanying drawings, in which: figure l is a schematic illustration of a valve device and the relative hydraulic system made in accordance with a first embodiment of the present invention; figure 2 is a schematic illustration of a valve device and the relative hydraulic system made in accordance with a second embodiment of the present invention; figure 3 is a schematic illustration of a valve device and the relative hydraulic system made in accordance with a third embodiment of the present invention;

[0046] DETAILED DESCRIPTION OF THE INVENTION

[0047] With reference initially to figure 1, an open-centre valve device in accordance with the invention is illustrated overall with reference number 3.

[0048] The valve device 3 is inserted in the context of a hydraulic system 100 of an operating machine.

[0049] 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.

[0050] In the attached figures the valve device is depicted by way of example provided with three generic sections El, E2 and E3 each of which controls a relative actuator, not illustrated in the figure, through the machine operating the work ports Al, Bl, A2, B2, A3 and B3.

[0051] Each section El, E2, E3 comprises at least one spool control element Cl, C2, C3 therein.

[0052] When the spools are not actuated and are in the neutral position, the fluid from the high-pressure line 2 passes through the free flow passages LC1, LC2 and LC3 along a free flow duct 6 and is sent to the discharge T through the duct 5.

[0053] Advantageously, the free flow duct 6 is split into separate segments 61, 62, 63 which connect the control elements of each section.

[0054] When a control element Cl or C2 is actuated, the high-pressure line 2 is selectively put into communication with the work ports Al, Bl, A2, B2, A3 and B3 and actually manages the actuators of the operating machine in which the control valve device is inserted.

[0055] This configuration defines delivery passages MAI, MA2, ..., MB1, MB2, ... on the respective control element.

[0056] For simplicity of description, the references of the delivery passages of only the sections El and E2 are indicated in figure 1 and only those of the section El are indicated in figures 2 and 3.

[0057] In general, in the following description reference will mainly be made to one of the sections of the device, it being clear that what has been described may also apply to the further sections, if any.

[0058] The work port Bl, Al, B2, A2, B3 and A3 selectively not put in communication with the high-pressure line 2 is connected to the successive segment of the free flow duct 61, 62 and 63 through series ducts 71, 72.

[0059] This connection defines on the control element respective return passages TAI, TA2, ..., TB1, TB2,.... Also in this case, the figures only partially show the references relative to the return passages, as previously illustrated.

[0060] The direct free flow passage LC1, LC2 and LC3 defined on the control element is closed upon actuation of the control element when the relative spool is moved from the neutral position. Thereby, by actuating several spools simultaneously, only the first one actuated directly feeds the work ports by directly putting the high- pressure line in communication with one work port at a time. The passage 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 flow segment of the successive section.

[0061] The actuated control element next to the one intercepting the free flow line is actually fed by the non-fed work port of the previous actuated section. In fact, when a control element is actuated, it closes the passage LC and selectively puts in communication the work ports connected to it with the series ducts and the free flow segment previously mentioned. Only in the last actuated control element is the selectively non-fed work port put in communication with the discharge T.

[0062] Within the control elements Cl, the spool manages two independent connections between the return branches TAI and TB1 of the respective work ports and the first segment of the series duct 71. Accordingly, in preferred embodiments, the first part of said series duct consists of two independent segments 71A and 71B.

[0063] Preferably, along said segments 71A and 71B two recesses are made with relative non-return valves VSAl and VSBl. The two connection portions of the independent segments 71A and 71B of the series duct included downstream of the spool before said valves are referred to as TSAI and TSB1.

[0064] To solve the previously mentioned problem of the prior art due to the presence of non-return valves along the series duct, three examples of embodiment are now illustrated in detail.

[0065] A first embodiment is for example represented in figure 1.

[0066] In particular, in some embodiments, branching ducts 81 and 83 are made, which are branched to the ducts TSAI and TSB1 upstream of the valves VSAl and VSBl. Respective branching points 710A and 710B are thus defined at which the branching duct connects with the respective segment of the series duct.

[0067] It should be noted that for descriptive simplicity in the figures, as well as in the following description, the branching ducts are illustrated only with reference to the first section or only to one of the movements attributable to the connections of the work ports connected to a cylinder. The embodiments are to be understood as being achievable on both work ports of the pair of work ports present in a section, and on several sections of the series system, not necessarily and only the first control section of the valve device.

[0068] The control element is advantageously an 8-way and at least 3-position element. When the control element is in a neutral position, the high-pressure line 2 is connected to the free flow line, making the flow rate of fluid arrive at the successive sections. When all the control elements are in the neutral position, the fluid is sent directly to discharge 5 without sending flow rate to the work ports.

[0069] The control element also provides two positions to respectively actuate the one or the other work port of the section, making the return flow rate of fluid flow from the relative work port to the series segment 71.

[0070] A fourth position can also be provided in which both work ports are connected directly to the discharge.

[0071] By way of example, the movement made through the spool connection P->B1 and A1- TSA1- 71 can be considered, that is, a movement of the spool such that the pressurized operating fluid from the high-pressure line 2 is supplied to the work port Bl and the fluid returning from the actuator through the work port Al is supplied to the connection portion TSAI.

[0072] In this position the line indicated with reference 5A1 in figure 1 operates as a line of return from the work port Al and the line 5B1 operates as a line of delivery from the control element Cl to the work port Bl.

[0073] It will therefore be appreciated that depending on the controlled work port, the lines 5A1, 5B2,... e 5B1, 5B2,... will operate as delivery lines or return lines. For this reason, these lines will be indicated below in general as delivery / return lines 5A1, 5B2,... e 5B1, 5B2,....

[0074] A pressure valve 4A (4B possibly for the respective duct 83 on the opposite movement) is inserted along the branching duct 81.

[0075] The valve 4A is normally closed and the force of a spring 43 acts on one end 41 thereof. On the opposite end 42, the pressure present along the branching duct itself acts on a driving area 45. Under normal conditions the pressure valve remains closed. Once the pressure applied to the driving area 45 exceeds the preload value of the spring 43, a passage is opened through the valve 4A itself which put the series duct into discharge mode by putting the branching duct 81 in communication with a duct 82 connected with the discharge line T or with a low-pressure line independent of the discharge itself T.

[0076] A second embodiment of the invention is illustrated in figure 2. In this case the pressure valve 4A is configured in such a way that the force of the spring 43 acts on the first end, while on the opposite end 42 the pressure present along the branching duct itself acts on a first driving area 45 and the pressure signal PMB1 present on the respective branch connected to the opposed delivery line on the cylinder of the spool control element 3 to the return branch TAI that feeds said series line TSAI, taken through a respective duct 46, acts on a second driving area 44.

[0077] Note that the two driving areas 44 and 45 placed on the same end 42 of the valve 4A are not necessarily the same. Under normal conditions the pressure valve remains closed. Once the pressures applied to the two driving areas 44 and 45 exceed the preload value of the spring 43, a passage is opened through the valve 4A which put the series duct into discharge mode by putting the branching duct 81 in communication with a duct 82 connected with the discharge line S or with a low- pressure line independent of the discharge T itself.

[0078] It should be noted that the present solution with two driving areas described above may be adopted in both the pressure valves 4A and 4B illustrated with reference to the previous embodiment.

[0079] In the third embodiment of figure 3, a single branching is made with the relative non-return valve VS in the portion of the series channel 71. In this solution there is therefore a single branching passage 81 of the return flow of the series duct 71 along which a single pressure valve 4A is inserted. The invention made according to the present embodiment is attributable to the operating principle described for the solution of figure 1 except for the fact that there is a single non-return valve along the series duct 71 there is a single trigger threshold due to the single valve 4A on the actuations of the spool towards the work port.

[0080] The seat of the valve(s) 4A, 4B can be made as well as inside the valve device

[0081] 3 also on a block that is directly flanged or connectable to the valve device 3 itself, following the hydraulic connections of the ducts as indicated above.

Claims

CLAIMS1. An open-centre valve device (3) for heavy equipment machines comprising: a first section (El) and a second section (E2), said sections being configured to be connected to respective pairs of work ports (Al, A2, Bl, B2) to actuate a respective actuator of the operating machine, a high-pressure line (2) configured in such a way as to be connected to a pump (1) to supply a flow rate of operating fluid to said sections, and a discharge line (S) configured in such a way as to be connected to a discharge (T) of said operating fluid, each of said sections comprising a spool control element (Cl, C2), configured in such a way as to send the flow rate of fluid to the respective work ports (Al, A2, Bl, B2), said valve device (3) further including: one or more free flow segments (61, 62) configured in such a way as to define a free flow line (6) that joins in successive sequence said control elements (Cl, C2), each of said control elements including a free flow passage (LC1, LC2) configured in such a way that, when all the control elements (Cl, C2) are in a neutral position, said high-pressure line (2) is connected to said discharge line (S) without sending the flow rate to the work ports, a series duct (71, 72) configured in such a way that, upon a movement from the neutral position of one of said control elements for the actuation of one of said actuators, a return flow rate from a respective work port is supplied to a successive control element, progressively closing the respective free flow passage, wherein at least one of said sections (El) comprises at least one branchingduct (81) connecting a respective series duct (71) with said discharge (T) or to a low-pressure line independent of said discharge, a pressure valve (4A) being arranged along the branching duct (81), said pressure valve (4A) being normally closed and configured in such a way as to open upon reaching a certain pressure in said branching duct (81) such that the fluid flowing in said series duct (71) is primarily sent to said discharge (T) or said low-pressure line, said valve device further comprising a non-return valve (VSAl) arranged along said series duct (71) downstream of a branching point (710A) at which said branching duct (81) connects to said series duct (71).

2. The valve device (3) according to claim 1, wherein said non-return valve (VSAl) is configured to prevent a passage of fluid from said series duct (71) towards the control element (Cl).

3. The valve device (3) according to claim 1 or 2, wherein said pressure valve (40) is configured in such a way that a pressure taken from said branching duct (81), upstream of said pressure valve (40), acts on a first end (42), and an elastic element (43) acts on a second end (41), opposite to the first end, said pressure valve (40) being configured in such a way as to displace itself into an open position when a force greater than a respective force exerted by the spring on the second end is exerted on said first end.

4. The valve device (3) according to any one of the preceding claims, wherein each section comprises respective delivery / return lines (5A1, 5B1, 5A2, 5B2) each configured to operate as a delivery line or return line according to the work port which is actuated by sending to / receiving from respective work ports (Al, Bl, A2, B2) of each pair of work ports the flow rate of fluid following the actuation of the respective control element (Cl, C2).

5. The valve device (3) according to the preceding claim, comprising respective connection portions (TSAI, TSB1), said connection portions (TSSA1, TSB1) being configured in such a way as to receive, through said spool control element (Cl), the flow rate of operating fluid returning from the respective work port which is actuated, the operating fluid coming from the line (5A1, 5B1, 5A2, 5B2) which operates as a return being directed towards one of said connection portions of the series duct (71) when a work port of the pair of work ports is actuated and towards the other of said connection portions when the other work port is actuated.

6. The valve device (3) according to the preceding claim, wherein said connection portions (TSAI, TSB1) comprise at least one connection portion (TSAI) connected to said series duct (71).

7. The valve device (3) according to the preceding claim, wherein said connection portions are both connected to said series duct (71).

8. The valve device (3) according to any one of claims 5 to 7, wherein said first end of the pressure valve defines a first driving area (45) and a second driving area (44), said pressure valve (4A) being configured in such a way that a pressure taken along said branching line (81) upstream of said pressure valve acts on said first driving area (45), and a pressure signal (PMB1) present on the respective line (5B1), when it operates as a delivery line, acts on said second driving area (44), said pressure valve (4A9 being further configured such that a return flow rate of operating fluid passes through said connection portion (TSAI) connected to said series duct (71).

9. The valve device (3) according to any one of the preceding claims, when dependent on claim 2, wherein said series duct (71, 72) defines two distinct series segments (71A, 71B), said fluid being sent to a respective series segmentbetween said two distinct segments according to the work port selected, by the spool control element, among the respective pair of work ports to actuate the actuator, each of said series segments comprising a respective non-return valve (VSAl, VSBl) configured to prevent a passage of fluid from said series duct (71) towards the control element upstream of said series duct (71).

10. The valve device (3) according to any one of the preceding claims, when dependent on claim 5, wherein said spool control element (3) is configured such that, when one work port of the pair of work ports of the section is actuated, the operating fluid is directed towards one (TSAI) of said connection portions of the series duct (71) and when the other work port is actuated, the operating fluid is directed towards the other (TSB1) of said connection portions.

11. The valve device (3) according to any one of the preceding claims, when dependent on claim 9, wherein said branching duct (81) is connected to a first segment (71A) of the series duct (71), said non-return valve (VSAl) being arranged along said first segment (71A) and a further non-return valve (VSBl) being arranged along a second segment (71B) of the series duct (71), said further non-return valve (VSBl) being configured to prevent a passage of fluid from said second series segment (71) towards the control element (Cl), said first segment (71A) and said second segment (71B) each being connected to a respective connection portion (TSAI, TSA2).

12. The valve device (3) according to any one of the preceding claims, when dependent on claim 9, wherein said second series segment (71B) is connected to a further branching duct (83) which connects the second series segment (71) with said discharge (T) or to said low-pressure line independent of said discharge (T), a further pressure valve (4B) being arranged along the further branching duct (83), said further pressure valve (4B) being normally closed andconfigured in such a way as to open upon reaching a certain pressure in said further branching duct (83) in such a way that the fluid flowing in said series duct (71) is primarily sent to said discharge (T) or to said low-pressure line independent of said discharge (T).

13. The valve device (3) according to any one of the preceding claims, wherein said pressure valve(s) (4A, 4B) is / are formed on a separate block made as an independent body with respect to a main body including said sections (El, E2), said separate body being directly flanged to said main body or configured in such a way as to be connectable to said main body.

14. A hydraulic system (100) comprising a pump (1) and a valve device (3) made according to one or more of the preceding claims.

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