ITMI992467A1 - HYDRAULIC CONTROL DEVICE FOR THE OPERATION OF A HYDRAULIC USER WITH HIGH STABILITY INLET PRESSURE COMPENSATOR - Google Patents

Description

DESCRIPTION

The present invention relates to a control device, for operating a hydraulic user, with an inlet pressure compensator, with high operating stability. More particularly, the device according to the present invention is intended to be used in hydraulic systems for operating users consisting of double-acting hydraulic cylinders, or hydraulic motors, or of users with two operating branches which are selectively connected with a pressurized branch of the hydraulic circuit and with an unloaded branch, for example in machines for lifting or moving a load.

Hydraulic circuits are known, generally fed by a single pump of adequate capacity, for the operation of several users which usually have different loads, or which require different pressures for their operation.

It should be noted that, generally, it is required that the various users must be controlled in a completely independent way, that is, that variations in the resisting load or in the operation of one user must not affect the operation of the other users. Each user is usually controlled by a bidirectional pilot valve which selectively connects the two hydraulic supply branches of the relative user with the pressure branch of the main circuit or with the unloaded branch, or which closes these two supply branches of the user. considered.

In order to obtain the correct functioning of the various utilities, avoiding that the flow rate delivered by the pump must be directed mainly in the direction of the user with a lower load to the detriment of the utilities with a higher load, on the branch of the circuit that connects the branch under pressure, i.e. the pump delivery, a pressure compensator is arranged at the pilot valve of each user. This pressure compensator has the function of maintaining constant the difference in pressure between the pressure branch of the hydraulic circuit, connected to the pump delivery, and the operating pressure that overcomes the load, by means of which it is formed astride the distribution or pilot valve spool.

The operating pressure which overcomes the load, or which brakes the load, acts, together with a spring, in the sense of increasing the opening of the pressure compensator in contrast to the action of the pressure on the supply branch of the pilot valve.

In practice, the two supply branches of the user, through the actuation of the pilot valve, are connected respectively with the branch under pressure that enters the pilot valve and with the discharge branch of the circuit, the branch of the user connected with the branch under pressure is connected, through the same pilot valve, to a duct which enters the pressure compensator and through which the operating pressure is transmitted to the pressure compensator.

The pressure that is transmitted through this duct from the user branch to the pressure compensator constitutes a hydraulic signal called "load sensing" or LS which, in this way, drives the pressure compensator.

In some applications it is required that the actuation of the user in question be interrupted when the pressure along an actuation branch of the same user reaches a predetermined maximum value. To meet this need, the LS pipe is connected to a maximum pressure valve which connects the LS pipe and therefore the corresponding user operating branch with the discharge branch of the circuit, or more generally with a discharge, upon reaching this maximum preset pressure.

In some cases, the possibility of interrupting the actuation of the user considered is also required when two different maximum pressures are reached on the two operating branches of the user.

To meet these needs, special devices have been developed, one of which is described in patent No. 1.281.708 of the same Applicant.

In some operating conditions, such as when a load is lowered, i.e. when the hydraulic user, consisting of a hydraulic cylinder or a hydraulic motor, works mainly as a brake, the hydraulic user is required to be activated with low pressures and with a reduced flow rate.

On such occasions, with devices equipped with a pressure compensator on the inlet of the bidirectional pilot valve that controls the operation of the hydraulic user, problems of instability may arise in the form of pulsating pressures that generate strong oscillations on the mechanical structures of the machines themselves, such as to compromise its functionality.

The aim of the present invention is to solve the aforementioned problems by providing a hydraulic control device, for operating a hydraulic user, with an inlet pressure compensator, which achieves high operating stability during said operation.

Within this aim, an object of the invention is to provide a device that ensures operating stability even when the hydraulic user must be operated with low pressures and reduced flow rates.

Another object of the invention is to provide a device which can be obtained, with minor and simple modifications, by known devices equipped with a pressure compensator on the inlet of the bidirectional pilot valve which controls the actuation of the hydraulic user.

This task, as well as these and other purposes which will appear better later, are achieved by a hydraulic control device, for the operation of a hydraulic user, with inlet pressure compensator, comprising a bidirectional pilot valve that can be operated to connect a branch for operating a user with a pressurized branch of a hydraulic circuit and the other operating branch for the user with a branch unloading from the hydraulic circuit and a pressure compensator placed on the pressurized branch of the hydraulic circuit entering said valve pilot, said pilot valve comprising a valve body with defined a substantially cylindrical seat slidably housing a cursor; said seat presenting, along its axial development, areas of larger diameter alternating with areas of smaller diameter slidingly coupled with said slider; said areas with larger diameter defining, in the valve body, around said slider, a plurality of chambers comprising a first chamber in a substantially central position, communicating with a first port connected to the pressurized branch of the hydraulic circuit; laterally on opposite sides to said first chamber a second chamber and a third chamber being defined respectively communicating with a second port connected to a user operating branch and with a third port connected to another user operating branch; laterally to said second chamber and to said third chamber, on the opposite side to said first chamber, a fourth chamber and a fifth chamber being defined respectively communicating with a fourth port and with a fifth port connected to the discharge branch of the hydraulic circuit; laterally to said fourth chamber and to said fifth chamber, on the opposite side to said first chamber, a sixth chamber and a seventh chamber being defined respectively communicating with a sixth port and a seventh port connected to a control duct connected to said compensator pressure for its actuation in contrast to the pressure along said pressurized branch entering the pilot valve; said cursor being movable on command in three positions of which: a first position in which it connects said first chamber with said second chamber and said third chamber with said fifth chamber, a second position in which it connects said first chamber with said third chamber and said second chamber with said fourth chamber, a third position or rest position in which the connection of said first chamber with said second chamber and with said third chamber is interrupted, characterized by the fact that said sixth chamber is in communication with said seventh chamber and by the fact that said cursor has at least a first internal duct connecting, with the cursor in said first position or in said second position, said first chamber with said sixth chamber or with said seventh chamber, said cursor also presenting at least a first connecting passage, with the cursor in said first position or in said second position, said seventh chamber with said fifth chamber or said sixth a chamber with said fourth chamber.

Further characteristics and advantages of the invention will become clearer from the description of two preferred but not exclusive embodiments of the device according to the invention, illustrated, by way of non-limiting example, in the accompanying drawings, in which:

Figures 1 to 6 show a first embodiment of the device according to the invention, more particularly:

Figure 1 illustrates the pilot valve, axially sectioned, with the spool in the first position;

Figure 2 illustrates the pilot valve, axially sectioned, with the spool in the second position;

Figure 3 shows the pilot valve, axially sectioned, with the spool in the third position;

Figure 4 schematically illustrates the device according to the invention with the spool of the pilot valve in the first position;

Figure 5 schematically illustrates the device according to the invention with the spool of the pilot valve in the second position;

figure 6 is a schematic view of the device according to the invention with the spool of the pilot valve in the third position;

Figures 7 to 12 illustrate a second embodiment of the device according to the invention, more particularly:

Figure 7 illustrates the pilot valve, axially sectioned, with the spool in the first position;

figure 8 shows the pilot valve, axially sectioned, with the spool in the second position,

Figure 9 illustrates the pilot valve, axially sectioned, with the spool in the third position;

Figure 10 schematically illustrates the device according to the invention with the spool of the pilot valve in the first position,

Figure 11 schematically illustrates the device according to the invention with the spool of the pilot valve in the second position;

Figure 12 schematically illustrates the device according to the invention with the slider of the pilot valve in the third position; Figure 13 illustrates a hydraulic diagram for operating two users, one of which is operated by means of the device according to the invention.

With particular reference to Figures 1 to 6, the device according to the invention, in the first embodiment, comprises a bidirectional pilot valve, globally indicated with the reference number 1, which can be operated to connect an actuation branch A or B of a hydraulic user with a pressurized branch P of a hydraulic circuit and the other operating branch B or A of the user with a discharge branch T of the hydraulic circuit.

The device also comprises, in a per se known manner, a pressure compensator 2 which is placed on the pressure branch of the hydraulic circuit which enters the pilot valve 1. The section of the pressure branch which extends from the pressure compensator 2 to the valve pilot 1 was marked with P1.

The pilot valve 1 comprises a valve body 3 in which a substantially cylindrical seat 4 is defined which accommodates, in an axially sliding manner, a cursor 5 which is coaxially arranged in said seat 4.

The seat 4 has, along its axial development, areas of greater diameter alternating with areas of smaller diameter and the latter are coupled, in a sliding and sealed manner, with areas of the casing of the slider 5. These areas with larger diameter define, in the body 3 of the pilot valve 1, around the spool 5, a series of chambers which comprise a first chamber 6, in a substantially central position, which communicates with a first port 7 defined in the valve body 3 and connected to the pressure branch P1 of the circuit hydraulic outlet from the pressure compensator 2.

Laterally, on opposite sides to the first chamber 6, a second chamber 8 and a third chamber 9 are defined which respectively communicate with a second port 10, defined in the body 3 of the pilot valve 1 and connected to the operating branch A of the user, and with a third port 11 defined in the body 3 of the pilot valve 1 and connected to the actuation branch B of the other user.

On the side of the second chamber 8 and the third chamber 9, on the opposite side with respect to the first chamber 6, a fourth chamber 12 and a fifth chamber 13 are defined which communicate respectively with a fourth port 14 and with a fifth port 15, which are defined in the body 3 of the pilot valve 1 and which are connected to the discharge branch T of the hydraulic circuit.

On the side of the fourth chamber 12 and the fifth chamber 13, on the opposite side with respect to the first chamber 6, a sixth chamber 16 and a seventh chamber 17 are defined which communicate respectively with a sixth port 18 and with a seventh port 19 which are defined in the body 3 of the pilot valve 1 and which are connected to the inlet 20a of a control duct 20 which is in turn connected to the pressure compensator 2 for its actuation against the pressure along the pressure branch which enters the pilot valve 1.

On the side of the sixth chamber 16 and the seventh chamber 17, on the opposite side to the first chamber 6, an eighth chamber 21 and a ninth chamber 22 are defined which communicate respectively with an eighth port 23 and with a ninth port 24 which are defined in the body 3 of the pilot valve 1 and which are connected respectively to a first control duct 25 and to a second control duct 26.

The cursor 5 is movable on command, along its axis inside the seat 4, in three operating positions: a first position in which it connects the first chamber 6 with the second chamber 8 and the third chamber 9 with the fifth chamber 13 , in such a way as to connect the operating branch A of the user with the pressurized branch of the hydraulic circuit and the operating branch B of the user with the unloading branch of the hydraulic circuit, a second position in which it connects the first chamber 6 with the third chamber 9 and the second chamber B with the fourth chamber 12 in such a way as to connect the operating branch B of the user with the pressurized branch of the hydraulic circuit and the operating branch A of the user with the unloading branch of the hydraulic circuit, a third position or rest position, in which it interrupts the connection of the first chamber 6 with the second chamber 8 and with the third chamber 9.

According to the invention, the sixth chamber 16 is in communication, through a connecting duct 32, with the seventh chamber 17 and the slider 5 has at least one first internal duct 30 which connects, when the slider 5 is in the first position or in the second position , the first chamber 6 with the sixth chamber 16 or with the seventh chamber 17; the slider 5 also has a first passage 31 which connects, when the slider 5 is in the first or second position, the seventh chamber 17 with the fifth chamber 13 or the sixth chamber 16 with the fourth chamber 12.

Furthermore, the cursor 4, in the first position, connects the sixth chamber 16 with the eighth chamber 21 and, in the second position, connects the seventh chamber 17 with the ninth chamber 22.

The chambers 6, 8, 9, 12, 13, 16, 17, 21 and 22 are arranged symmetrically with respect to an ideal median plane 33 perpendicular to the axis of the seat 4. The slider 5 has an operating area, with a substantially cylindrical shape, with circumferential narrowings 34, 35, 36 and 37 spaced apart, which is intended to interact with the aforementioned chambers.

More particularly, the circumferential narrowings 34, 35, 36 and 37, delimit, on the operating area of the slider, a central portion 38, two lateral-median portions 39 and 40 and two lateral-extreme portions 41, 42. Straddling the circumferential narrowings 34 and 35, located respectively between the central portion 38 and the lateral-median portion 39 and between the central portion 38 and the lateral-median portion 40, there are slots 43, 44. When the slider 5 is in the first position, the slots 43 connect the first chamber 6 with the second chamber 8 and the recesses 44 connect the third chamber 9 with the fifth chamber 13, while when the cursor 5 is in the second position, the recesses 43 connect the second chamber 8 with the fourth chamber 12 and the smanchi 44 connect the first chamber 6 with the third chamber 9.

The smanchi 43, 44 have a cusp conformation which gradually widens in the direction of the external surface of the slider and which also gradually widen from the lateral-median portions 39, 40 and from the central portion 38 in the direction of the circumferential narrowings 34 and 35 astride of which they extend.

In the embodiment illustrated, in which the internal duct 30 extends into the area of the slider 5 occupied by the central portion 38, the lateral-median portion 40 and the lateral-extreme portion 42, this internal duct 30 has an inlet 30a on the central portion 38 and an outlet 30b in correspondence with the circumferential narrowing 37.

The first passage 31 consists of a constriction which is defined on the lateral-median portion 39 of the slider 5 and preferably has a section which progressively narrows in the direction of the central portion 38 of the slider 5.

Conveniently, in the first embodiment, a second internal duct 50 is defined in the slider 5 which connects, when the slider 5 is in the first position, the second chamber 8 with the sixth chamber 16 and, when the slider 5 is in the second position, connects the fourth chamber 12 with the eighth chamber 21.

According to requirements, the position of the first internal duct 30 could be inverted with that of the second internal duct 50 in a symmetrical way with respect to the ideal median plane 33a of the slider 5. This median plane 33a coincides with the median plane 33 of the seat 4 when cursor 5 is in the third position. In this case, the inlet 30a would still be defined on the central portion 38 but in such a way as to be in the second chamber B when the slider 5 is in the first position and the outlet 30b would be in correspondence with the circumferential narrowing 36; again in this case, the second internal duct 50 would have an inlet 50a on the lateral-median portion 40 so as to be in the fifth chamber 13 when the slider 5 is moved to the first position and an outlet 50b in correspondence with the circumferential narrowing 37 and to be located in the third chamber 9 by connecting it with the seventh chamber 17 when the cursor 5 is moved to the second position.

The pressure compensator 2 is pushed into the closed position by the pressure along P1 in contrast to the action of a spring 60. The control duct 20 is connected to the pressure compensator 2 so as to act on this in accordance with the action of the spring 60 and therefore in the direction of opening the pressure compensator.

With particular reference to Figures 4 to 6, the first control duct 25, along which the hydraulic pressure signal LSA is transmitted, corresponding to the operating pressure of the branch A of the user, is connected to the discharge branch T of the hydraulic circuit through a maximum pressure valve 61 which connects the control duct 25 with the discharge branch T when a pressure at least equal to the calibration pressure of the valve 61 occurs along the control duct 25.

The second control duct 26, along which the pressure hydraulic signal LSB is transmitted, corresponding to the operating pressure of the utility branch B, is also connected to the discharge branch T of the hydraulic circuit through a relief valve. pressure 62 which connects the control duct 26 with the discharge branch T when a pressure at least equal to the calibration pressure of the valve 62 occurs along the control duct 26.

Advantageously, the control ducts 25 and 26 each have a branch which is connected to the discharge branch T by means of respective solenoid valves 63 and 64 which can be driven. The solenoid valves 63 and 64, in normal operating conditions, are energized or closed and therefore prevent the connection of the control ducts 25 and 26 with the unloading branch T and can be de-energized to make this connection when conditions occur that require a interruption of the utility operation during operation on branch A or branch B.

The circuit illustrated in Figures 4 to 6 is completed by a restriction 65 arranged on the control line 20 and by a branch 20b of the control line 20 which enters an exchange valve 66 or selector. The outlet of the exchange valve 66, as illustrated in Figure 13, is connected to a flow / pressure regulator 67 which is arranged along a branch 68 connecting the pressure branch P with the discharge branch T of the hydraulic circuit. More particularly, the flow rate / pressure regulator 67 is kept in the open position by the pressure present in the pressure branch P in contrast to the action exerted by a spring 69. The signal LS coming from the control duct 20 acts on the flow regulator / pressure 67 in accordance with the action of the spring 69 which therefore acts in the direction of causing the closure of the flow rate / pressure regulator 67, as will become clearer hereinafter.

Figure 13 illustrates a hydraulic circuit which serves two users, respectively a first user, indicated with the reference number 80, controlled by a device according to the invention and a second user, globally indicated by the number 81, which is controlled by a device of the type illustrated in the aforementioned patent No. 1.281.708.

The LS signal coming from the first device 80, at the output from the changeover or selector valve 66, passes through a second changeover or selector valve 70 into which the LS signal of the device 81 also enters and therefore reaches the flow rate / pressure regulator 67. pump that feeds the hydraulic circuit is indicated by number 71. As regards the other elements shown in figure 13, since they are elements commonly used in the hydraulic circuit sector, the detailed description is omitted.

It should be noted that, according to requirements, one or both of the maximum pressure valves 61 and 62 may be absent, as well as one or both of the solenoid valves 63 and 64 may be absent.

The operation of the device in the first embodiment is as follows.

It should be noted that the device, in this first embodiment, is particularly suitable for use when a user activation similar to that obtainable with a proportional direction valve in the supply of branch A of the user is required, such as during lifting a load, and when branch B of the user has to be operated with low pressure and reduced flow, such as when lowering a load.

When the cursor 5 from the third position or rest position (Figures 3 and 6) is moved to the first position (Figures 1 and 4), the first chamber 6 is connected with the second chamber 8, the sixth chamber 16 is connected with the eighth chamber 21, the third chamber 9 is connected with the fifth chamber 13. In this operating condition, moreover, the duct 50 connects the second chamber 8 with the sixth chamber 16 while the duct 30 connects the third chamber 9 with the ninth chamber 22. In this way, the branch P1 is connected with the branch A. It should be noted that, with the cursor 5 in this position, the branch A and the branch P1 are connected with the control conduit 20, along which the signal LS is transmitted, and with the first control duct 25 along which the hydraulic signal LSA is transmitted.

The branch B and the second control duct 26, along which the hydraulic signal LS, ti, is transmitted, are connected to the discharge branch T. In this operating condition, the pressure compensator 2 operates normally.

On the other hand, when the cursor 5 is moved from the rest position to the second position (Figures 2 and 5), the first chamber 6 is connected to the third chamber 9, the seventh chamber 17 is connected to the ninth chamber 22, the second chamber 8 is connected to the fourth chamber 12. The duct 30 connects the first chamber 6 to the seventh chamber 17, the duct 50 connects the fourth chamber 12 with the eighth chamber 21 while the passage 31 puts the sixth chamber 16 in communication with the fourth chamber 12. In this operating condition, the pressure of the branch P1 is transmitted to the seventh chamber 17 and from this to the pressure compensator 2 in such a way that this pressure acts in accordance with the spring 60 to keep the pressure compensator 2 in the open position or in any case to increase its 'opening. Due to the fact that the seventh chamber 17 is in communication, through the connection duct 32 with the sixth chamber 16, a part of the flow entering the first chamber 6 is sent into the discharge branch T through the passage 31. The extent of the flow flow rate discharged through the passage 31 will be a function of the position of the spool 5 following the particular shape of the same passage 31. Due to the fact that the pressure transmitted along the control duct 20 to the pressure compensator 2 is equal to or slightly lower than the pressure along branch P1, the compensator 2 is kept in a position of complete opening or in any case in a position in which its opening is greater than that which would arise if the control conduit 20 were connected to the branch B of the user.

Furthermore, the signal LS, which is equal to or slightly lower than the pressure P1, through the exchange valves 66, 70, is sent to the flow rate / pressure regulator 67 assisting the spring 69 in causing or increasing the closure of this flow rate / pressure regulator 67. In this way, the working pressure of pump 71 is considerably higher than that necessary to supply branch B of the user. Thanks to this fact, greater operating stability is achieved even if the user requires low pressures and reduced flow rates to be operated.

In the second embodiment, illustrated in Figures 7 to 11, the device again comprises a bidirectional pilot valve, globally indicated with the reference number la, whose body is substantially made like the body 3 of the pilot valve 11. For this reason , the body of the pilot valve la, the seat for the spool 5a, the various chambers defined along this seat as well as the ports for the connection of various ducts, have been marked with the same reference numbers used to mark the analogous elements described in reference to the first form of execution. The slider 5a, as regards its shell, is made in the same way as described with reference to the slider 5 of the first embodiment. For this reason, the central portion, the lateral-median portions, the lateral-outer portions and the circumferential narrowings, as well as the gaps arranged in correspondence with the circumferential narrowings placed on the sides of the central portion, have been marked with the same reference numbers used in the figures 1 to 3.

In the slider 5a, in a similar way to the first embodiment, an internal duct is obtained, still marked with the reference number 30.

Unlike the slider 5, the slider 5a has a second internal duct 80 which has an inlet 80a on the central portion 38 and an outlet 80b in correspondence with the circumferential narrowing 36. The position of the inlet 80a is such as to be inside the first chamber 6 to connect the first chamber 6 with the sixth chamber 16 when the cursor 5a is moved to the first position and to be in the second chamber 8 to connect it with the eighth chamber 21 when the cursor 5a is moved to the second location.

Again unlike the slider 5, the slider 5a has, on the lateral-median portion 40, a second passage 81 which, when the slider 5a is in the first position, connects the seventh chamber 17 with the fifth chamber 13.

In practice, in the second embodiment, the slider 5a is preferably made in such a way as to be symmetrical with respect to the ideal median plane 33a of the slider 5a.

Also the hydraulic circuit in which the pilot valve la is inserted, illustrated in figures 10 to 12, is the same as the hydraulic circuit illustrated in figures 4 to 6. For this reason, the various elements of the circuit which are illustrated in figures 10 to 12, have been marked with the same reference numbers as the elements of the circuit illustrated in Figures 4 to 6.

The operation of the device according to the invention in the second embodiment is as follows.

When the cursor 5a is moved from the third position or rest position (Figures 9 and 12) to the first position (Figures 7 and 10), the first chamber 6 is connected with the second chamber 8, the sixth chamber 16 is connected with the eighth chamber 21, the third chamber 9 is connected with the fifth chamber 13. The duct 80 connects the first chamber 6 with the sixth chamber 16, the duct 30 connects the third chamber 9 with the ninth chamber 22 while the passage 81 puts in communication the seventh chamber 17 with the fifth chamber 13. In this operating condition, the branch P1 of the hydraulic circuit is connected to the branch A of the user while the branch B of the user is connected to the discharge branch T. The branch A of the The user is in communication with the first control duct 25, while the second branch B and the second control duct 26 are connected to the discharge branch T.

In this first position, moreover, the inlet pressure to the pilot valve is transmitted, through the second internal duct 80, to the control duct 20 and helps the spring 60 in its action on the pressure compensator 2 to maintain or increase its pressure. opening. A part of the inlet flow to the pilot valve 1 is conveyed to the discharge branch T through the second passage 81 which connects the seventh chamber 17 with the fifth chamber 13 following the connection between the sixth chamber 16 and the seventh chamber 17. The amount of flow that is conveyed to the discharge branch T depends on the position of the slider 5a following the particular conformation of the second passage 81.

In this first position, the LS signal is also transmitted, through changeover or selector valves, to a flow / pressure regulator, as already described with reference to the first embodiment, to maintain this flow / pressure regulator in the position of closing, thus forcing the pump that feeds the pressurized branch to work at higher pressures than those actually needed to operate the user.

By moving the slider 5a to the second position, an operation is similar to that described with reference to the first embodiment, that is, an operation of the pump with higher pressures is obtained also for supplying the user branch B. Thanks to this fact, both during the operation of the branch A of the user and during the operation of the branch B of the user, the pump is forced to work at higher pressures than those necessary for the operation of the user and, consequently, greater operating stability is obtained.

It should be noted that, both in the first embodiment and in the second embodiment, the pressurized fluid which is withdrawn from the central chamber, through the internal duct 30 or 80, is conveyed to the drain, through the relative passage 31 or 81 , allows the chambers 16 and 17 to be kept at the same pressure and therefore ensures perfect hydrostatic support of the slider 5 or 5a.

In practice it has been found that the device according to the invention fully achieves the intended aim because, thanks to the fact that it forces the pump to operate at a higher pressure than that actually required by the user actuation, it achieves greater operating stability even if the user, in order to be activated, requires reduced pressures and flow rates.

A further advantage of the device according to the invention is that of being able to use a pilot valve which can be derived, in an extremely simple way, from pilot valves of a known type, for example of the type illustrated in patent no. 1.281.708 by simply replacing the cursor.

The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept. Furthermore, all the details may be replaced by other technically equivalent elements.

In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

Claims (13)

R I V E N D I C A Z I O N I 1. Hydraulic control device, for operating a hydraulic user, with inlet pressure compensator, comprising a bidirectional pilot valve that can be operated to connect an operating branch of a user with a pressurized branch of a hydraulic circuit and the other branch for operating the user with a branch unloading from the hydraulic circuit and a pressure compensator placed on the pressure branch of the hydraulic circuit entering said pilot valve, said pilot valve comprising a valve body with a substantially cylindrical seat defined slidably accommodating a slider; said seat presenting, along its axial development, areas of greater diameter alternating with areas of smaller diameter slidingly coupled with said slider; said areas with larger diameter defining, in the valve body, around said slider, a plurality of chambers comprising a first chamber in a substantially central position, communicating with a first port connected to the pressurized branch of the hydraulic circuit; laterally on opposite sides to said first chamber a second chamber and a third chamber being defined respectively communicating with a second port connected to a user operating branch and with a third port connected to another user operating branch; laterally to said second chamber and to said third chamber, on the opposite side to said first chamber, a fourth chamber and a fifth chamber being defined respectively communicating with a fourth port and with a fifth port connected to the discharge branch of the hydraulic circuit; laterally to said fourth chamber and to said fifth chamber. on the opposite side to said first chamber, a sixth chamber and a seventh chamber being defined respectively communicating with a sixth port and a seventh port connected to a control duct connected to said pressure compensator for its actuation in contrast to the pressure along said branch under pressure entering the pilot valve; said cursor being movable on command in three positions of which: a first position in which it connects said first chamber with said second chamber and said third chamber with said fifth chamber, a second position in which it connects said first chamber with said third chamber and said second chamber with said fourth chamber, a third position or rest position in which the connection of said first chamber with said second chamber and with said third chamber is interrupted, characterized by the fact that said sixth chamber is in communication with said seventh chamber and by the fact that said cursor has at least a first internal duct connecting, with the cursor in said first position or in said second position, said first chamber with said sixth chamber or with said seventh chamber, said cursor also presenting at least a first connecting passage, with the cursor in said first position or in said second position, said seventh chamber with said fifth chamber or said sixth a chamber with said fourth chamber. 2. Device, according to claim 1, characterized in that in correspondence with said seat, in the valve body, laterally to said sixth chamber and said seventh chamber, on the opposite side to said first chamber, an eighth chamber and ninth chamber communicating respectively with an eighth port connected to a control conduit and a ninth port connected to another control conduit, said cursor, in said first position, connecting said sixth chamber with said eighth chamber and, in said second position , connecting said seventh chamber with said ninth chamber. 3. Device, according to claims 1 and 2, characterized in that said chambers are arranged symmetrically with respect to a median plane perpendicular to the axis of said seat and by the fact that said slider has an operating area, substantially cylindrical in shape with circumferential narrowings spaced apart, intended to interact with said chambers. 4. Device according to one or more of the preceding claims, characterized in that said circumferential narrowings define, on said operating zone of the slider: a central portion, two lateral-median portions and two lateral-extreme portions of said slider; gaps being provided extending from said lateral portions by means of said central portion straddling the narrowings located between said portions; said snaps connecting said second chamber with said first chamber and said third chamber with said fifth chamber when said slider is in the first position and connecting said first chamber with said third chamber and said second chamber with said fourth chamber when said slider is in second position. 5. Device, according to one or more of the preceding claims, characterized in that said notches have a cusp conformation gradually widening in the direction of the external surface of said slider and also gradually widening from said lateral-median portions and from said central portion in the direction circumferential narrowings across which they extend. 6. Device according to one or more of the preceding claims, characterized in that said internal duct has an inlet on said central portion and an outlet on the circumferential narrowing placed between one of said lateral-median portions and the contiguous extreme lateral portion. 7. Device according to one or more of the preceding claims, characterized in that said first passage is constituted by a constriction defined on a lateral-median portion of said slider. 8. Device, according to one or more of the preceding claims, characterized in that said narrowing has a section which gradually narrows in the direction of said central portion of said slider. 9. Device according to one or more of the preceding claims, characterized in that said slider has a second internal duct connecting, with the slider in said first position or in said second position, said second chamber with said sixth chamber or said fourth chamber with called the eighth chamber. 10. Device according to one or more of the preceding claims, characterized in that said first internal duct of the slider extends into the portion of the slider extending from said central portion to an axial end of the slider, said second internal duct developing into the portion of the slider extending from said central portion to the other axial end of the slider. 11. Device according to one or more of the preceding claims, characterized in that said slider has: - a first internal duct connecting, with the cursor in said first position, said first chamber with said sixth chamber and, with a cursor in said second position, said second chamber with said eighth chamber; - a first passage connecting, with the cursor in said first position, said seventh chamber with said fifth chamber; - a second internal duct connecting, with the cursor in said first position, said third chamber with said ninth chamber and, with the cursor in said second position, said first chamber with said seventh chamber, - a second passage connecting, with the cursor in said second position, said sixth chamber with said fourth chamber. 12. Device, according to one or more of the preceding claims, characterized in that said control duct is connected to a flow / pressure regulator, connecting the pressure branch with the discharge branch of the hydraulic circuit, to operate or increase its closure in contrast to the action exerted by the pressure in said pressurized branch. 13. Hydraulic control device for operating a hydraulic user, with inlet pressure compensator, characterized in that it comprises one or more of the characteristics described and / or illustrated.