EP2018482A1

EP2018482A1 - A fluid flow distribution device and a plant for fluid flow distribution comprising the device

Info

Publication number: EP2018482A1
Application number: EP06766291A
Authority: EP
Inventors: Danilo Manfredi
Original assignee: NEM SRL
Current assignee: NEM SRL
Priority date: 2006-05-15
Filing date: 2006-05-15
Publication date: 2009-01-28
Also published as: WO2007132488A1

Abstract

The fluid flow distribution device for plants comprising at least two hydraulic interconnected distributors (1) comprises an obturator (5), acting on a flow rate of a fluid transiting between an inlet conduit and an outlet conduit (38), and mobile among a plurality of operative positions; at least a by-pass conduit, being a preferential pathway for at least a part of the fluid coming from the fluid source at least when the obturator stops the fluid transit; at least a distribution organ (18) for activating the obturator among the operative positions thereof. The device comprises a by-pass circuit which is operatively associable to each by pass conduit of the distributors, and at least a deviation circuit, located in derivation from the by-pass circuit and acting on at least one of the distribution organs with at least a part of the fluid flow rate transiting internally of the by-pass circuit and generating an activation of the obturator. A plant for the distribution of the flow rate comprises at least two hydraulic distributors (1) connected to respective users, the distributors being interconnected to one another by a fluid flow distribution device of the described type.

Description

A Fluid Flow Distribution Device and a Plant for Fluid Flow Distribution comprising the Device.

Technical Field

The invention relates to a fluid flow distribution device and a plant for fluid flow distribution comprising the device. Background Art The invention relates to the field of hydraulically-activateid plants and in particular to the field of manoeuvring plants comprising two or more hydraulic distributors, each of which is destined to regulate the movement of a respective user. A typical example of such plants is the drive apparatus of earth-moving machines, in which the movements of the turret, the bucket and the shovel are regulated by respective hydraulic distributors. As is known, machines and plants belonging to this field include a hydraulic inter-connection among the varisou distributors, in particular they are connected to a pump for pressurised fluid delivery, generally oil, and supply each a relative user according to commands given by an operator. In particular, these commands are generally realised by activating respective levers in measures which are proportionate to the effect to be obtained, to which a corresponding impulse follows, correctly varying the flow rate of presurised fluid to each user. In particular, each impulse directly or indirectly activates an obturator of a corresponding distributor, opening and closing passage holes for the pressurised fluid internally of the distributor. The flow rate of the oil circulated by the pump is generally constant or, in any case, has a top limit which relates to the ratings characteristics of the pump itself.

The flow rate produced by the pump is distributed automatically among the various distributors according to the power demands thereof, in particular according to the passage holes defined by the positions of the obturators of the single distributors.

In some circumstances, however, it can happen that the power demand of one or more users consistently exceeds the power demand of the other users, for example due to application of a greater load to one or more users. This is converted into an increase of demanded flow rate from those users. In a case where the overall flow rate demanded by the users exceeds the maximum the pump can produce, the plant malfunctions and in particular there is an anomalous absorption of fluid flow rate by the users under load, with a consquent saturation of the flow rate supplied by the pump and a partial or total arrest of the other users, caused by an insufficient power supply thereto. The prior art teaches devices for partialising the fluid flow rate, sometimes known as anti-saturation devices, which deal out the flow rate inletting the various single distributors according to the fluid pressure in inlet to the user and therefore downstream of the distributor. These devices measure the fluid pressure using pressure sensors and communicate the measured pressure level to dedicated processors which where necessary reduce the command signals to one or more distributors. These devices, however, require the presence of pressure sensors located on all users in order to have a continuous fluid pressure reading of the fluid pressure in inlet to the users. The presence of pressure sensors disadvantageously reduces the reliability of the device and therefore the plant, as pressure sensors can be subject to faults and malfunctions. Further, these devices require one or more processors for dealing with the pressure data and for correcting the signals sent to the distributors. This requires the presence of data transmission systems between the pressure sensors and the processors, for example cables. These data transmission sensors are complex and often unwieldy and they increase the level of construction difficulty of the device, and therefore of the plant. It is also true that pressure level reading by sensors, even mechanical sensors, and subsequent processing of the values can lead to errors connected with the imprecision of the pressure level reading.

Further, as mentioned, the processing of the measured pressure levels leads to corrections in the size of the passage holes for the fluid internally of the hydraulic distributors. This requires the presence of special transducers which convert the correcting signals generated by the processor into movements of the obturator to modify the opening of the through-holes. A disadvantage of these transducers is that the overall reliability of the device and therefore the plant is reduced. The transducers are generally electromechanical and liable to malfunction and break.

The various natures of the components (hydraulic, electromechanical, electronic, mechanical) which have to interact in prior-art anti-saturation devices lead to delays in overall system response, given the different responses to transients that the single components make. This leads to damaging repercussions in relation to the overall speed of response of the system and its stability.

The main aim of the present invention is to provide a fluid flow distribution device and a plant for fluid flow distribution comprising the device, which is free of the above-described drawbacks. An important aim of the invention is to provide a fluid flow distribution device and a plant for fluid flow distribution comprising the device which are highly reliable.

A further aim of the invention is to provide a fluid flow distribution device and a plant for fluid flow distribution comprising the device which minimise the complexity of realisation and operation.

A further important aim of the invention is to provide a fluid flow distribution device and a plant for fluid flow distribution comprising the device which maximise operative precision and response readiness.

Another important aim of the invention is to provide a fluid flow distribution device and a plant for fluid flow distribution comprising the device which exhibit a rapid response to transients.

These aims and others besides, as will better emerge in the detailed description that follows, are attained by a fluid flow distribution device and a plant for fluid flow distribution comprising the device having the characteristics expressed in claim 1 and/or in one or more of the dependent claims thereon.

In a further embodiment of the invention, a plant for fluid flow distribution is described in claim 14 and/or in one or more claims that are dependent thereon. Disclosure of Invention

A preferred but non-exclusive embodiment of the invention is now described, with reference to the non-limiting figures of the drawings, in which: figure 1 is a partially-sectioned and partly schematic view of a fluid flow distribution device and a plant for fluid flow distribution comprising the device of the invention; figure 2 is a section view of a hydraulic distributor used in the plant of figure

1, in non-operative configuration; figure 3 is a section view of a portion of the distributor of figure 2 in a non- operative configuration; figure 4 is a section view of a portion of the distributor of figure 2 is a first operative position thereof; figure 5 is a section view of a portion of the distributor of figure 2, in a second operative position thereof; figure 6 is a section view of a portion of the distributor of figure 2, in a third operative position thereof; figure 7 is a section view of a portion of the distributor of figure 2, in a fourth operative position thereof. With reference to the figures of the drawings, 100 denotes in its entirety the plant of the invention, including a fluid flow distribution device according to the invention.

The plant 100 comprises at least two hydraulic distributors 101 the functioning of which is illustrated in figures 2-6 and which will be described in more detail herein below. In general terms, the plant 100 can comprise a plurality of hydraulic distributors 101, preferably having the same characteristics, the interaction during operation thereof being regulated by the device 1. In particular the distributors 101 are hydraulically connected to one another by the device 1, and the functioning of each thereof is linked to the functioning of the other distributors 101. The device 1 therefore automatically supervises the operation of the distributors 101, intervening whenever a condition of imbalance in the overall functioning of the plant 100 occurs. In the preferred embodiment, illustrated in the figures of the drawings, each distributor 101 receives a fluid in inlet, preferably pressurised oil, regulates it and conveys it towards a user which can be, for example, a single- or double- acting hydraulic piston, or in any case a general user commanded by pressurised fluid. The distributor 101 comprises a support body 102 which is specially shaped to house a plurality of operative elements necessary for the operation of the distributor 101, which operative elements will be described in more detail herein below.

In particular, the distributor 101 comprises an inlet conduit 103 of the fluid, which fluid is supplied by a source of known type, for example a pump P and a delivery conduit 104 which can be connected to the user. In figure 2, the user is illustrated by way of example as a double-acting piston, and denoted by U. The inlet conduit 103 and the delivery conduit 104 are realised in the support body 102 and are in fluid communication, defining a predetermined pathway for the fluid internally of the distributor 101. The distributor 101 further comprises an obturator 105, which acts between the inlet conduit 103 and the delivery conduit 104 and realises a change in flow rate of the fluid internally of the delivery conduit 104. The obturator 105, which in the preferred embodiment is a slide valve 105a, is housed in a seating 106 and is mobile among a plurality of operative passage positions of respective fluid flow rates from the inlet conduit 103 towards the delivery conduit 104. The obturator 105 can preferably assume closed position in which it completely obstructs the passage of the fluid from the inlet conduit 103 towards the delivery conduit 104. The obturator 105 is moved between the plurality of operative positions by means therefor which will be better described herein below, and which displace the obturator 105 along a sliding direction X. With the aim of controlling the displacement of the obturator 105 in response to preset parameters, the distributor 101 comprises an actuator 107 which acts on the obturator 105 to move it between the plurality of operative positions and the closure positions.

The obturator 5 is advantageously moved along the sliding direction X directly by the fluid flow transiting in the delivery conduit 104 in line with a user U flow demand, following a functioning principle which will be more fully described herein below. In particular, the actuator 107 is directly activated by a momentaneous difference in fluid flow rate running between the inlet conduit 103 and the delivery conduit 104. The actuator 107 thus has the function of receiving instantaneous command impulses originating from the flow rate change, and imposing, on the basis of this change, a displacement on the obturator 105 along the sliding direction X, to meet the demands of the user U. Further, the actuator 107 is operatively active between the inlet conduit 103 and the obturator 105 and is advantageously in fluid communication with the obturator 105 to activate it hydraulically to displace among the respective operative and closure positions. In more detail, the actuator 107 comprises a plunger piston 108, sensitive to instantaneous flow rate variations between the inlet conduit 103 and the delivery conduit 104 and slidable in a respective sliding seating 109 according to the changes detected in the flow rate. The plunger piston 108 exhibits a flow-rate activated portion ; preferably this portion is a first end 110 of the plunger piston 108. In the preferred and illustrated embodiment of the distributor 1, the plunger piston 108 is located between the inlet conduit 103 and the obturator 105.

The plunger piston 108 is slidable internally of the seating 109 along a sliding direction Y which is parallel to a main development direction of the piston 108 itself. Further, the plunger piston 8 internally exhibits a through-hole 111 in the sliding direction Y which places the first end 110 in fluid communication with a second end 112 of the piston 108, opposite the first end 110. The first end 110 is tapered. In more detail, the first end 110 exhibits a central portion 113 which is preferably convex, and which engages and occludes a connection conduit 114 between the plunger piston 8 and the obturator 105, and a peripheral portion 115 which is preferably concave, and on which the fluid in inlet from the inlet conduit 103 acts, receiving from the transiting flow rate an axial thrust along the sliding direction Y of the plunger piston. The second end 112 of the plunger piston 8 is preferably flat and directed perpendicular to the sliding direction Y of the plunger piston 108. Further, the second end 112 is associated to first means for elastic contrast 116, such as for example a helix spring, engaged between the plunger piston 116 and a portion of the support body 102 to contrast the axial thrust exerted by the fluid on the plunger piston 108 itself.

The second end 112 of the piston 108 is in fluid communication with the connection conduit 114 through the through-hole 111. Further the inlet conduit 103 preferably has an outflow section 117 on the peripheral portion 115 of the first end 110 of the plunger piston 108. The plunger piston 108 can also have an axial-symmetric conformation with respect to the prevalent development direction thereof, although other shapes are possible, such as for example prismatic or cylindrical conformations. The actuator 107 further comprises at least a distribution organ 118 having an inlet 119 placed in communication with a fluid source, and at least an outlet 120 in fluid communication with the obturator 105 in order to activate it hydraulically. The distribution organ 18 further comprises a discharge outlet 121 in fluid communication with a fluid collection reservoir. In the preferred embodiment, illustrated in the accompanying figures of the drawings, the distributor 101 comprises two distribution organs 118 which are symmetrically arranged with respect to the plunger piston 108, for activating a user U, which is a double-acting cylinder. There follows a detailed description of structural and functional aspects of one of the two distribution organs 118, as in the preferred embodiment the two distribution organs 118 are identical apart from having a specular symmetry. In a preferred embodiment, not illustrated, the two distribution organs might be structurally different, though having identical functions. In detail, each distribution organ 118 comprises a respective liner 122 which is slidable within a sliding seating 123 along a respective sliding direction W to intercept the inlet 119 and the outlet 120 of the distribution organ 118. Further, the distribution organ 118 comprises a pilot piston 124 which is mobile internally of a liner 122 therefor, which selectively places the inlet 119 of the distribution organ 118 in fluid communication with the outlet 120, and the outlet 120 in fluid communication with the discharge outlet 121. The liner 122 is provided with through-holes 125 which place the pilot piston 124 in fluid communication respectively with the inlet 119 and the outlet 120 of the distribution organ 118, and also with the discharge outlet 121. The through holes 125 preferably each comprise an enlarged portion 125a, for example a spot-faced portion, for intercepting the fluid from the inlet 119 or send it on to the discharge outlet 121 following displacements of the liner 122 which cause small misalignments between each opening and the inlet 119 or the discharge outlet 121 to which it is associated.

The pilot piston 124 exhibits a shape composed of two cylindrical parts 126, having greater diameter which is about the same as an internal diameter of the liner 122 so that there is a fluid seal. The two cylindrical parts 126 are separated by an intermediate part 127, preferably cylindrical and having a smaller transversal dimension than the cylindrical parts 126 in the sliding direction W of the liner 122. The two cylindrical parts 126 are located at a reciprocal distance which is such as at least partially to associate the two cylindrical parts 126 respectively at the inlet 119 and at the discharge outlet 121 of the distribution organ 118. The cylindrical parts 126 and the intermediate part 127 together define a manoeuvring chamber 128 in fluid communication selectively with the inlet 119 and the discharge outlet 121 according to the position assumed by the pilot piston 124 with respect to the liner 122, and are in perpetual fluid communication with the outlet 120. The pilot piston 124 can thus assume static positions in which the cylindrical parts thereof 126 close the inlet 119 and the outlet 121 (figure 7), intervention positions in which the inlet 119 is at least partially uncovered from the respective cylindrical part 126 to which it is associated while the discharge outlet 121 is closed (figures from 4 to 6) and release positions in which the discharge outlet 121 is at least partially uncovered by the respective cylindrical part 126 to which it is associated while the inlet 119 is closed (figures 2 and 3).

The pilot piston 124 is activated by a respective pilot actuator 129, comprising a nucleus 129a which is solidly constrained to the pilot piston 124 and a coil 129b which magnetically surrounds the nucleus 29a. The coil 129b is excited by a current which is proportional to a command impulse, for example relating to an entity of displacement of a lever activated by an operator, and generates a displacement of the nucleus 129a which cause a movement of the pilot piston 124 with respect to the liner 122. The pilot piston 124 is also associated to second elastic contrast means 130, preferably comprising a helix spring, which have the function of contrasting the displacement of the pilot piston 124 following the action of the pilot actuator 129. The nucleus 129a of the pilot actuator 129 is connected to the pilot piston 124 in a retracted position with respect to an operating advancing position of the pilot piston 124. The operative advancement of the pilot piston 124 is the movement it makes when it places the inlet 119 in communication with the outlet 120 starting from the closed position of the inlet 119 and the outlet 120, i.e. when the pilot piston 124 establishes a fluid communication between the inlet 119 and the activating chamber 135 in order to activate the obturator 105.

Also, the cylindrical part 126 of the pilot piston 124 opposite the nucleus 129a of the pilot actuator 129, together with the liner 122, defines an auxiliary chamber H hydraulically separated from the manoeuvring chamber 128 because of a fluid seal realised by the cylindrical part 126, opposite the pilot actuator 129, and the liner 122.

The distribution organ 118, in particular the liner 122, and the actuator are operatively associated in order to enable the distribution organ 118 to receive displacement impulses from the actuator 107 and transmit consequent displacements to the obturator 105.

For this purpose, the distributor 101 comprises mechanical command means 131 which act between the plunger piston 108 and the liner 122. The mechanical command means 131 comprise a channel 132 afforded on the plunger piston 108, engaged slidably and progressively by a wedge-shaped protuberance 133 associated to the liner 122, for example by a dragging connection.

The sliding direction Y of the plunger piston 108 and the sliding direction W of the liner 122 are preferably directed perpendicularly to one another. Also, the channel 132 and the wedge-shaped protuberance 133 engage along a surface Z which is inclined with respect to the sliding directions Y, W of the plunger piston 108 and the liner 122, so as to convert a translation of the plunger piston 108 along the sliding direction Y into a translation of the liner 122 along the respective sliding direction W. To maintain the channel 132 in reciprocal contact with the wedge-shaped protuberance 133, the liner 122 is advantageously associated with third elastic contrast means 134 acting between the liner 122 and the support body 102, which third elastic contrast means 134 are elastically preloaded to guarantee continuous contact between the wedge-shaped protuberance 133 and the channel 132. The mechanical command means 131 have the function of moving the liner 122 among a plurality of operative positions of movement of the obturator 105. Due to the structure of the distribution organ 118, each position assumed by the pilot piston 124 and the liner 122 realise a precise operative position of the obturator 105, inasmuch as it defines precise passage holes of the fluid through the manoeuvring chamber 128 and therefore a precise fluid flow destined to activate the obturator 105.

To cause the obturator 105 to move between the relative operative positions and the closure position, the distributor 101 further comprises at least an activating chamber 135, in fluid communication with the outlet 120 of the distribution organ 118 and active on an end of the obturator 105 to transmit an axial sliding thrust to the obturator 105. The activating chamber 135 is fluid-sealed from the outside and its structure enables the obturator 105 to be moved by commanded injections of fluid through the inlet 119 and the outlet 120 of the distribution organ 118 and commanded releases of the fluid contained in the activating chamber 135, which is discharged through the outlet 120 and the discharge outlet 121. The end of the obturator 105 on which the activation chamber 135 acts is associated to fourth elastic means 136, e.g. a helix spring, which returns the obturator 105 to the non-operative position of figure 3 following displacements of the obturator 105 towards operative positions. The obturator 105 comprises a main valve 137 which closes the fluid flow rate associated to the delivery conduit 104, selectively interrupting the fluid flow towards the user U. The main valve 137 is thus mobile between a closed position, associated to the non-operative position of the obturator 105 illustrated in figures 2 and 3, and a plurality of open positions associated with the plurality of operative positions of the obturator 105, illustrated in figures from 4 to 7.

In non-operative positions, the distributor 101 includes automatic discharge of the fluid coming from the pump, without the fluid itself engaging actively in the distributor 101. For this purpose, the distributor comprises at least a by- pass conduit 138 defining a preferential pathway for the fluid coming from the pump P when the main valve 137 is closed. The distributor 101 preferably comprises a pair of by-pass conduits 138 associated to a respective distribution organ 118. The obturator 105 comprises a first valve 139 associated to the by-pass conduit 138 for closing or at least partially opening the by-pass conduit 138 by sliding the obturator 105 along the sliding direction X. The obturator 105 preferably comprises a pair of first valves 139, each associated to the respective by-pass conduit 138. In figure 3 the first valves 139 are illustrated in the discharge position. The distributor 101 further comprises an outlet opening 140 to send on the fluid towards the user U, and a return opening 141 for the fluid coming back from the user U. The outlet and return openings 140, 141, are preferably contiguous to the main valve 137 and to the delivery conduit 104, and realise a direct fluid communication with the delivery conduit 104. The obturator 105 also comprises a pair of second valves 142, each associated respectively to the outlet opening 140 and the return opening 141, for at least partially uncovering the outlet opening 140 and the return opening 141 at least when the delivery conduit 104 is open. The second valves 142 preferably have a smaller transversal size than the seating 106 of the obturator 105, and for this reason always leave the outlet 140 and the return 141 openings open.

With the purpose of evacuating the fluid returning from the user U, the distributor 101 comprises at least a discharge conduit 143. The distributor 101 preferably comprises a pair of discharge conduits 143, one of which is contiguous to the outlet conduit 140 while the other is contiguous to the return conduit 141. The distributor therefore advantageously has a reversible function, so that the outlet conduit 140 and the return conduit can reciprocally invert their functions according to the operation mode of the device. The obturator 105 comprises at least a third valve 144, associated to the discharge conduit 143. Preferably the obturator 105 comprises a third pair of valves 144, each associated to one of the discharge conduits 143 to uncover the discharge conduit at least when the main valve 137 uncovers the delivery conduit 104.

In the preferred and illustrated embodiment, the distributor 101 comprises a pair of activating chambers 135, each acting on an opposite end of the obturator 105 in order to move it in a one sense of the sliding direction X. A helix spring, being the fourth elastic means 136, operates at each end of the obturator 105.

The functioning of a distributor 101 according to the invention and having the above characteristics will now be described. In operation, in a start configuration in which the distributor 101 is in a non- operative equilibrium configuration, illustrated in figures 2 and 3, the pump P is in fluid communication with the inlet conduit 103, with the inlet 119 and the by-pass conduits 138 through a triple offtake downstream of the pump P itself. The fluid pressure at the inlet 119 is preferably lower than the fluid pressure in the inlet conduit 103 and the by-pass conduit 138. The distributor organ 118 operates at lower pressure to work pressure of the user U and is therefore equipped with a reduction valve 145 of the pressure between the pump P and the inlet 119. In the configuration of figures 2 and 3, the plunger piston 108 breasts the connection conduit 114, occluding it, while the liners 122 and the pilot pistons 124 are positioned so as to obstruct fluid supply to the manoeuvring chamber 128 through the respective inlets 119. In this configuration, the fluid delivered by the pump P discharges entirely through the by-pass conduits 138. Furthermore, the discharge outlets 121 are open, creating stable discharge conditions in the manoeuvring chamber 128 and thus the respective activating chambers 135. This places the obturator 105 in a non-operative position, in which it closes the delivery conduit 104 and interrupts the fluid flow towards the user U. This closure means that part of the operatively active fluid in previous cycles stays inside the through-hole 111 of the plunger piston 8 and in proximity of the second end 112 of the plunger piston

108.

When a user U demands power, a signal, preferably analog, is sent to one of the two coils 129b in the form of, for example, a modulated current. In a non-limiting description of the present invention, the user U will be, for the present purposes, a double-acting cylinder; thus the respective out and return runs of the piston stem require separate actions, only one of which will be analysed here as the other action is identical. The excitation of the coil 129b generates a consequent displacement of the nucleus 129a, which draws the respective pilot piston 124. In particular, the pilot piston 124 is brought close to the plunger piston 108. The movement of the pilot piston 124, the entity of which is determined by the excitation current level crossing the coil 129b, obstructs the discharge outlet 121 and at least partially uncovers the inlet 119. A pressurised fluid delivery follows, flowing into the manoeuvring chamber 128 and, through the respective outlet 120, flowing internally of the activating chamber 135, increasing internal pressure therein. This stage is illustrated in figure 4. The increase in pressure in the activating chamber 135 leads the obturator 105 to displace, translating away from the activating chamber 135, overcoming the reaction of the fourth elastic means 136. During this stage the main valve 137 at least partially uncovers the delivery conduit 4, associating it to the outlet opening 140. A part of the fluid which was initially trapped in the through hole 111 of the plunger piston and in the immediate vicinity of the connection conduit 114 exits; this fluid is then conveyed towards the user U through the outlet opening 140. The user U can return a fluid flow to be discharged, which is conveyed towards the distributor 101 through the return conduit 141. The translation of the obturator 5 leads to the translation of the third valves 144, one of which uncovers the respective discharge conduit 143. In particular, the discharge conduit 143 associated to the return opening 141 is uncovered. The outletting fluid from the user U, transiting internally of the return opening 141, is discharged through the discharge conduit 143. Further, the translation of the obturator 105 causes a translation of the first valves 139 and therefore a partial constriction of the by-pass conduits 138, followed by an increase in load losses associated to the outflowing of fluid in the by-pass conduits 138. This allows an increase in pressure and consequently the fluid flow-rate through the inlet conduit 103 and the connecting conduit 114 following a reduction of the fluid rate in discharge through the by-pass conduit 138. This stage is illustrated in figure 5. The progressive outflowing of the fluid from the inlet conduit 103 to the connecting conduit 114, with a consequent reduction of the fluid pressure in those zones, creates an imbalance of pressure on the plunger piston 108 which generates a progressive raising thereof. The second portion 112 and the central portion 113 of the first end 110 of the plunger piston 108 are surrounded by a pressure that is consistently lower than at the peripheral portion 115 of the first end 110 of the plunger piston 108. This generates a non-nil axial thrust on the plunger piston 108 which overcomes the reaction of the first elastic means 116. In other words, internally of the through-hole 111 of the plunger piston 8 and in the immediate vicinity, there is lacking a counter-pressure which is sufficient to balance the pump P delivery pressure, which presses on the peripheral portion 115 of the first end 110 of the plunger piston 108. This counter-pressure was present before the delivery conduit 104 was opened.

The raising of the plunger piston 108 causes detachment thereof from the connecting conduit 114 and causes an outflowing of the pressurised fluid from the inlet conduit 103 to the delivery conduit 104, and from there directly to the user U through the outlet opening 140.

The above stage is illustrated in figure 6 which illustrates the progressive evolution of the operative configuration of the distributor 101. Figure 6 shows that the channel 132 and the wedge-shaped protuberance 133 are not in contact, though in reality this does not happen as the third elastic means 134 keep the channel 132 and the wedge-shaped protuberance 133 in a perpetual state of reciprocal contact.

Figure 7 illustrates a stable equilibrium position which is brought about by the raising of the previously-illustrated plunger piston 108, the liner 122 associated to the pilot actuator 129 which was initially excited receiving a thrust in a nearing direction to the plunger piston 108 because of the inclination of the inclined surface Z. The displacement of the liner 122 with respect to the pilot piston 124, which persists in its initial perturbed position, causes a progressive closure of the inlet 119, interrupting pressurised fluid supply from the pump P to the manoeuvring chamber 128.

The liner associated to the non-excited pilot actuator 129 also undergoes a displacement, nearing the plunger piston 108; however there is no operative consequence to this as the respective pilot piston 124 is still in the initial position and keeps the inlet 119 closed, leaving the discharge opening 121 open, so that the respective manoeuvring chamber 128 is not in fluid communication with the pump P.

The distributor 101 thus reaches a condition of dynamic equilibrium, in which the obturator 105 maintains a translated operative position with respect to its non-operative position and allows passage of a constant fluid delivery from the inlet conduit 103 to the delivery conduit 104 and thus to the user U. Simple theory and practice teaches that if the pressure delivered from the pump P is kept constant, the constancy of the delivery determines the constancy of the hydraulic power absorbed by the user U. During the distributor 101 operation, transients can occur due for example to load changes associated with the user U. For example, the user might include an earth-moving bucket which, when cutting into the ground, meets an obstacle or a more-compacted layer of earth than before. This generates an increase in resistance which translates into an increase in fluid pressure transiting through the user U, and therefore an increase in pressure in the delivery conduit 104 which opposes the normal transit of the fluid flow from the pump P to the user U.

For an operator of earth-moving machines and the like, it is particularly important for the user device (for example a bucket as described above) to follow the most constant law of motion possible, a law which is independent of the time-by-time load the user U is subject to.

It is therefore necessary that the delivery internally of the delivery conduit 104 is maintained constant, even following variations in fluid pressure in the delivery conduit 104. Following the increase in pressure of the fluid transiting in the delivery conduit 104, the fluid is subject to a reduction as the increased pressure acts as a counter-pressure at discharge while the pressure of the pump P remains unaltered, thus reducing the transiting delivery. The pressure imbalance occurs at the first end 110 of the plunger piston 108 which, being invested by a smaller fluid delivery, is subject to a smaller axial thrust and consequently the first elastic means 116 can return the plunger piston 8 into a closer position to the connecting conduit 114, thus a lower position according to the accompanying figures than the dynamic equilibrium configuration previously reached and illustrated in figure 7. The pressure increase in the delivery conduit 104 advantageously does not generate an upwards thrust on the plunger piston 108, as the plunger piston 8 exhibits the through hole 111 which transfers the pressure levels at the first end 110 of the plunger piston 108 to the second end 112 of the plunger piston 108. In other words, the special geometry of the plunger piston 108 is such that the plunger piston 8 is sensitive to the fluid flow at the first end 110 thereof and at the variations over time, but there is no passing-on to the plunger piston 108 of any sensitivity to static pressure levels it is subject to.

The progressive lowering of the plunger piston 108 causes a displacement of the liner 122 associated to the initially-excited pilot actuator 129. This displacement of the liner 122 is in a direction away from the plunger piston 108 because of the orientation of the inclined surface Z of the command means 131. Following the liner 122 displacement, there is an at least partial opening of the inlet 119, as the pilot piston 124 remains in position. The opening of the inlet 119 resets the pump P in fluid communication with the manoeuvring chamber 128 and thus with the activating chamber 135. The pressure inside the activating chamber 135 therefore increases progressively, causing a translation of the obturator 105 away from the activating chamber 135 i.e. towards the right in the accompanying figures. The first valve 139 chokes the by-pass conduit 138 by more, causing an increase in pressure which generates an increase in fluid delivery to the user U which contrasts the previous pressure increase in the delivery conduit 104. The distributor progressively reaches a new condition of equilibrium in relation to the increased load on the user U.

In the case of load reduction on the user U₅ the device operates inversely to what is described above. In more detail, the pressure in the delivery conduit 104 diminishes and attracts a greater fluid delivery from the inlet conduit 103. The plunger piston 8 is therefore raised and in particular the first end 110 receives a greater axial thrust because of the greater flow rate it is subject to, and a displacement of the plunger piston 108 occurs, away from the connecting conduit 114. The action of the third elastic means 134 and the raising of the plunger piston 108 cause the liner 122 to displace towards the plunger piston 108, progressively closing the inlet 119 and uncovering the outlet 121. The pressurised fluid in the activating chamber 135 discharges through the outlet opening 121 and the fourth elastic means 136 recall the obturator 105 towards the activating chamber 135. The obturator 105, more precisely the first valve 139, tends to open the by-pass conduit 138, reducing pressure and fluid delivery transiting to the user U. The distributor 101 is therefore able to move progressively into a new dynamic equilibrium condition in a totally automatic process. To bring the distributor 101 into the initial non-operative configuration, it is sufficient to de-excite the coil 129b that was originally excited; this leads to the return of the nucleus 129a into the respective initial position by action of the second elastic contrast means 130. The displacement of the nucleus 129a returns the pilot piston 124 to its initial position, in which it closes off the inlet 119 and at least partially uncovers the discharge outlet 121. There is consequently a pressurised fluid outflow from the activating chamber 135 through he manoeuvring chamber 128, which resets the obturator 105 in the closed position.

The distributor 101 can work inversely by activating the other coil 129b, and therefore causing the inverse activation of the user U. In this case, the outlet opening 140 and the return opening 141 have their functions inverted.

It is also possible to create special hydraulic connections between the pump P and the distributor 101, for example by connecting the by-pass conduits 138, the discharge conduits 143 and the discharge outlets 121 with a single fluid collection device, for example a collection reservoir, possibly by connecting the device to an aspiration device of the pump P in order to generate a closed circuit of the fluid.

It is further advantageous to connect the inlet conduit 103 and the inlet 119 in derivation from the pump P, in order to reduce the overall complexity of the hydraulic connections; the pressure reducer valve 145 for the pressure upstream of the inlet 119 can be used for this.

Distributors 101 of the above type, as already described, can be applied singly, if the operation of a single user is to be controlled, or in cooperation, if complex and articulated users have to be regulated. In this second case, the regulation of the distributors 101 is done by one or more fluid flow distribution devices of the invention. In more detail, each device 1 comprises at least a by-pass circuit 2, operatively associable with each by-pass conduit 138 of the distributors 101 and destined to set in fluid communication the fluid source with the by-pass conduits 138 of the distributors 101, and the by-pass conduits 138 with one or more fluid collection reservoirs of the fluid discharge by the by-pass conduits 138. The fluid is taken from the fluid source before crossing the by-pass conduits 138 and discharging into a collection reservoir. A pressure reducer valve A is located immediately downstream of the pump P, for limiting the fluid pressure internally of the by-pass conduits 2, as the pressure within the by-pass conduits 2 regulates the plant 100 functioning, but the pressure reducer valve A has no power applications and therefore requires no maximum operational pressures, necessary for the operation of normal users. The by-pass circuit 2 preferably establishes a series fluid connection among the by-pass conduits 138 of a distributor 101 and the by-pass conduits 138 of another distributor 101. In other words, this type of connection is such that the fluid outletting from a by-pass conduit 138 of a distributor 101 is supplied in inlet to a by-pass conduit 138 of another distributor 101. In the preferred and illustrated embodiment, in which each distributor 101 comprises two by-pass conduits 138, the two by-pass conduits 138 are preferably connected to one another in parallel, in particular in derivation from the by-pass circuit 2.

The device 1 further comprises at least a deviation circuit 3, shunting from a respective by-pass circuit 2 and acting on the distribution organs 118 of the distributors 101 to move at least one of the distribution organs 118 with a least a part of the fluid flow transiting internally of the by-pass conduit 2 and therefore to generate an obturator 105 activation.

The device preferably comprises a single by-pass circuit 2 and a single deviation circuit 3, derived from the by-pass circuit 2.

The deviation circuit 3 sets in fluid communication at least one of the distribution organs 118, preferably both, of each distributor 101 with a portion of the by-pass circuit 2 upstream of all the distributors. This characteristic is strictly linked to the operative functioning of the device 1, inasmuch as the activating of the obturator 105, among its various operations, causes a progressive closure of the by-pass conduits 138. The at least partial closure of the by-pass conduits 138 generates differences of pressure in the fluid therein due to losses of load in the fluid itself, so the fluid upstream thereof has a greater pressure than the fluid downstream. It follows that in the whole by-pass circuit 2, the fluid pressure is located upstream of all the bypass conduits 2, thus upstream of all the distributors 101 and in particular in proximity of the pump P.

Also in a case of complete closure of both the by-pass conduits 138 of a single distributor 101, following a strong translation of the obturator 105, at the pump P the maximum circuit by-pass pressure is established. Because of the symmetrical conformation of each obturator 105, a strong translation of the obturator 105 causes closure of both by-pass conduits 138 associated thereto.

Therefore the derivation of the deviation circuit 3 from the by-pass circuit 2 upstream of all of the distributors 101 enables a pilot flow rate of closure of the by-pass conduits 138 of any one of the distributors 101 served by the device 1. The pilot flow rate is sensitive to a strong translation of the obturator 105 of one or more of the distributors 101. Thanks to the functioning of the distributor 101 described herein above, it is clear that the above-mentioned strong translation of the obturator 105 is evidence of the fact that the user connected to the distributor 101 is subject to an overload, which causes a considerable increase of the fluid flow rate demanded by the user U and which can cause an imbalance in the flow rate distribution towards the various distributors 101.

The device 1 further comprises a deviator valve V, acting on the deviation circuit 3 to regulate the conveying of the pilot flow rate from the by-pass circuit 2 towards the distribution organs 118, in particular to open or close the deviation circuit 3 in accordance with a fluid pressure upstream of the deviator valve V.

The deviator valve V is preferably a maximum pressure valve, calibrated to intervene at least when the by-pass conduit 2 is closed and in any case when the pressure upstream of the deviator valve V exceeds a predetermined level. When the by-pass conduit 2 is closed, the pressure of the fluid internally of the by-pass conduit 2 increases following the action of the pump P delivery. For best plant 100 functioning, the deviator valve is active in a portion of the deviation conduit 3 which is immediately downstream of the derivation of the deviation conduit 3 from the by-pass conduit 2, in order to have a pressure which is more or less equal to the pressure acting in the by-pass conduit 2 upstream of all of the distributors 101. This enables a more prompt and effective intervention of the deviator valve V, which receives a pressure signal which is indicative of the considerable load losses downstream of the branching of the deviation circuit 3 from the by-pass circuit 2. The pilot flow rate, derived from the by-pass circuit 2, can be advantageously conveyed to a distribution organ 118 for resetting the correct functioning of the distributors 101 according to what is described above. The pilot flow rate is preferably conveyed to all the distribution organs 118 of the distributors 101.

The pilot flow rate is conveyed to the auxiliary chamber H of each distribution organ 118.

The auxiliary chamber H is kept depressurised thanks to the presence of a tap- hole S. In order to create the directing of the pilot flow rate from the by-pass circuit 2 towards each auxiliary chamber H, each liner 122 exhibits a passage hole 146 for placing the respective auxiliary chamber H in communication with the outside environment. The passage hole 146 preferably places the auxiliary chamber H in communication with an antechamber 147, the passage hole 146 being realised at or near the wedge-shaped protuberance 133. The antechamber 147 is delimited by the sliding seating 123 of the respective liner 122, by a front portion of the liner 122 and by a lateral portion of the plunger piston 108. The antechamber 147 has therefore a variable volume in accordance with the position of the liner 122 and the contemporaneous geometrical configuration of the mechanical command means 131. Also, the antechamber 147 communicates with the outside through an outflow conduit 148 made in the support body 102.

The deviation circuit 3 exhibits two or more derivations, each terminating with an outflow section 4 associable to a respective outflow conduit 148 in order to supply the respective auxiliary chamber H with at least a part of the pilot flow rate tapping from the by-pass conduit 2. The outflow sections 4 are in reciprocal fluid communication as they are connected in derivation from the same deviation circuit 3. Further, the fluid communication between the outflow sections 4 is downstream of the deviator valve V, which therefore has the function of contemporaneously regulating all the distributors 101 associated to the device 1.

The pilot flow rate, conveyed into the auxiliary chambers H through the respective outflow conduits 148 and the respective antechambers 147, acts advantageously on the pilot piston 124, in particular on the respective cylindrical part 126 opposite the pilot actuator 129, generating a thrust on the pilot piston 124 which contrasts the operative advancement thereof. Further, the fluid pilot flow rate is at a pressure which is a function of the load losses in the by-pass circuit 2 and thus of the overload acting on one or more distributors 101. This means that anomalous fluid demands on the part of the overloaded distributors 101 can be compensated for, and the compensation is proportional to the overload itself.

The action on each pilot piston 124 tends to move it in the opposite direction to the operative advancement direction. Each pilot piston 124, moving closer to the respective pilot actuator 129, at least partially closes the respective inlet 119 while it at least partially uncovers the respective discharge outlet 121. This causes a corresponding translation of the obturators 105 towards the relative closure conditions of the respective delivery conduits 104. The effect obtained is thus a partial reduction of the fluid flow rates transiting internally of the distributors 101, balancing the excessive fluid demand manifested by one or more overloaded distributors 101 and generating an optimal redistribution of the fluid flow rates internally of the distributors 101. The present invention attains the set aims.

The device of the invention is sensitive to a momentaneous position of the distributor obturators, as the position assumed by the obturators determines a corresponding choking of the by-pass conduits and therefore a consequent pressure in the deviation conduits acting on the distribution organs, which are therefore instantaneously sensitive to any overloads in the users. This enables an automatic regulation of the flow rate transiting internally of the distributors, and in particular this regulation is done without there being any need for pressure sensors located on the distributors, with the consequent advantage of having a greater reliability with respect to prior-art devices. Also, this leads to the considerable advantage of having an absence of data transmission and processing systems, such as for example complex cabling systems and electronic boards for processing, or mechanical fluid systems. The realisation of the device of the invention is therefore simpler, as therefore is the realisation of the plant; the plant is also more reactive in its response to operational transients.

Also, the control directly performed on the fluid pressure, with no need to process signals coming from pressure sensors and generating electrical impulses on the pilot actuator, increases the overall precision of the device and further improves the ready-response of the plant.

Finally, a further advantage of the invention is that the fluid flow control system works fully a low pressures, and is therefore less sensitive to leakage phenomena between chambers at different pressures.

Claims

Claims.

1. A fluid flow distribution device for plants comprising at least two distributors (101), each distributor (101) comprising: an obturator (105), acting on an operative flow rate of a fluid transiting between an inlet conduit (103), hydraulically connected to a fluid source, and a delivery conduit (104), connected to a user (U), the obturator (105) being mobile among a plurality of operative positions defining various fluid flow levels, and closed positions, in which transit of the fluid flow towards the delivery conduit (104) is stopped; at least a by-pass conduit (138), being a preferential pathway for at least a part of the fluid coming from the fluid source at least when the obturator

(105) is in a closed position, each by-pass conduit (138) being at least partially closed when the obturator (105) therefore assumes an operative position thereof; at least a distribution organ (118) for activating the obturator (105) among the operative positions thereof; wherein the device (1) comprises at least a by-pass circuit (2) which is operatively associable to each by-pass conduit (138) of the distributors (101) in order hydraulically to connect the by-pass conduits (138) of at least two distributors (101) to one another, and at least a deviation circuit (3), located in derivation from the by-pass circuit (2) and acting on the distribution organs

(118) of the distributors (101), to move at least one of the distribution organs

(118) with at least a part of the fluid flow rate transiting internally of the by- pass circuit (2) and to generate an activation of the obturator (105).

2. The device of claim 1, wherein the by-pass circuit (2) sets the fluid source in communication with the by-pass conduits (138) of the distributors (101) and the by-pass conduits (138) in communication with a fluid collection reservoir.

3. The device of claim I₅ wherein the by-pass circuit (2) has a series fluid connection with the by-pass conduits (138) so that fluid outletting from the a by-pass conduit (138) of a distributor (101) is supplying in inlet to a by-pass conduit (138) of a further distributor (101).

4. The device of any one of the preceding claims, wherein the deviation circuit (3) sets the distribution organs (118) of each distributor (101) in fluid communication with a portion of the by-pass circuit (2) which portion is upstream of all of the distributors (101).

5. The device of any one of the preceding claims, wherein it comprises a deviator valve (V) located on the deviation circuit (3), which deviator valve (V) opens and shuts the deviation circuit (3) in accordance with a fluid flow rate level in the by-pass conduits (138).

6. The device of claim 5, wherein the deviator valve (V) is a maximum pressure valve which is normally closed to enable passage of fluid from the by-pass circuit (2) towards the distribution organs (118) of the distributors (101) when the fluid in the by-pass circuit (2) upstream of the deviator valve (V) reaches a predetermined pressure level.

7. The device of claim 5 or 6, wherein the deviator valve (V) is located immediately downstream of the derivation of the deviation circuit (3) from the by-pass circuit (2).

8. A process for distributing a flow rate of fluid in plants (100) comprising at least two interconnected hydraulic distributors (101), each comprising: an obturator (105) acting on a fluid flow rate transiting between an inlet conduit (103), hydraulically connected to a fluid source, and a delivery conduit (104), connected to a user (U), the obturator (105) being mobile among a plurality of operative positions, defining fluid flow rate levels, and closed positions, in which transit of the fluid flow towards the delivery conduit (104) is stopped; at least a by-pass conduit (138) defining a preferential pathway for at least a part of the fluid coming form the fluid source, at least when the obturator

(105) is in the closed position, each by-pass conduit (138) being at least partially closed when the respective obturator (105) assumes an operative position; at least a distribution organ (118) for activating the obturator (105) among the operative positions thereof; wherein the process comprises stages of: directing a fluid from the fluid source towards the by-pass conduits (138) of the distributors (101) through a by-pass circuit (2); conducting at least a part of the fluid flow transiting internally of the by-pass circuit (2) towards the distribution organs (118) of the distributors (101) for moving the distribution organs (118) and generating an activation of the respective obturator (105).

9. The process of claim 8, wherein the stage of directing a fluid from the fluid source towards the by-pass conduits (138) comprises a stage of conducting the fluid in series among the by-pass conduits (138), so that the fluid exiting from a by-pass conduit (138) of a distributor (101) is supplied in inlet to a bypass conduit (138) of another distributor (101).

10. The process of claim 8 or 9, wherein the stage of deviating at least a part of the fluid flow rate transiting in the by-pass circuit (2) towards the distribution organs (118) comprises a stage of setting in fluid communication the distribution organs (118) of the distributors (101) with a portion of the bypass circuit (2) upstream of all of the distributors (101) through a deviation circuit (3) branching-off from the by-pass circuit (2).

11. The process of any one of claims from 8 to 10, wherein the stage of deviating at least a part of the fluid flow comprises a stage of predisposing a deviator valve (V) located on the deviation circuit (3) for opening or closing the deviation circuit (3) according to a fluid pressure upstream of the deviator valve (V).

12. The process of claim 11, wherein the stage of predisposing a deviator valve (V) comprises a stage of calibrating the deviator valve (V) for enabling automatic opening thereof when the fluid pressure upstream of the deviator valve (V) reaches a predetermined level.

13. The process of claim 10 or H₅ wherein the stage of predisposing a deviator valve (V) comprises a stage of locating a deviator valve (V) immediately downstream of the branching-off of the derivation circuit (3) from the by-pass circuit (2).

14. A plant for fluid flow distribution comprising at least two hydraulically interconnected distributors (101), each distributor (101) comprising: an obturator (105), acting on an operative flow rate of a fluid transiting between an inlet conduit (103), hydraulically connected to a fluid source, and a delivery conduit (104), connected to a user (U), the obturator (105) being mobile among a plurality of operative positions reflecting various fluid flow levels, and closed positions, in which transit of the fluid flow towards the delivery conduit (104) is stopped; at least a by-pass conduit (138), being a preferential pathway for at least a part of the fluid coming from the fluid source at least when the obturator

(105) is in a closed position, each by-pass conduit (138) being at least partially closed when the obturator (105) therefore assumes an operative position thereof; at least a distribution organ (118) for activating the obturator (105) among the operative positions thereof; wherein the device (1) comprises at least a by-pass circuit (2) which is operatively associable to each by-pass conduit (138) of the distributors (101), and at least a deviation circuit (3), located branching off from the by-pass circuit (2) and acting on the distribution organs (118) of the distributors (101), to move the distribution organs (118) with at least a part of the fluid flow rate transiting internally of the by-pass circuit (2) and to generate an activation of the obturator (105).

15. The plant of claim 14, wherein each deviation circuit (3) is associated to a deviator valve (V) for opening or closing the deviation circuit (3) in accordance with a fluid pressure upstream of the deviator valve (V).

16. The plant of claim 15, wherein the deviator valve (V) is a maximum pressure valve, calibrated for intervening at least in a closure condition of one of the by-pass conduits (138), the closure condition of a by-pass conduit (138) causing an increase in fluid pressure upstream of the deviator valve (V).

17. The plant of any one of claims from 14 to 16, wherein the by-pass conduits (138) of the distributors (101) are connected to one another in series by means of the at least a by-pass circuit (2), in such a way that the fluid outletting from one or the by-pass conduits (138) is supplied in inlet to another of the by-pass conduits (138).

18. The plant of any one of claims from 14 to 17, wherein the at least a distribution organ (118) exhibits an inlet (119) set in fluid communication with a fluid source and an outlet (120) set in fluid communication with an activating chamber (135) acting on the obturator (105) in order hydraulically to activate the obturator (105).

19. The plant of claim 18, wherein the at least a distribution organ (118) comprises a discharge outlet (121) set in fluid communication with a reservoir for discharging fluid from the activating chamber (135) of the obturator (105).

20. The plant of claim 19, wherein the at least a distribution organ (118) comprises a pilot piston (124) which is slidingly mobile internally of a liner (122) in order selectively to place in fluid communication the inlet (119) of the distribution organ (118) and the outlet (120) of the distribution organ (118) with the discharge outlet (121) of the distribution organ (118).

21. The plant of claim 20, wherein the deviation circuit (3) acts on the pilot pistons (124) of the distributors (101) to move the pilot pistons (124) with at least a part of the fluid flow transiting internally of the by-pass circuit (2) and to generate an activation of the respective obturator (105).

22. The plant of claim 20 or 21, wherein the pilot piston (124) is activated by a respective pilot actuator (129).

23. The plant of claim 22, wherein the at least a part of the fluid flow transiting in the by-pass conduit (138) acts on the pilot piston (124) in an opposite direction to the operative actions exerted on the pilot piston (124) by the pilot actuator (129), in order to contrast the action of the pilot actuator (129).

24. The plant of any one of claims from 14 to 23, wherein each deviation circuit (3) exhibits at least two outflow sections (4), each in fluid communication with the distribution organs (118) of the distributors (101).

25. The plant of claim 24, wherein the outflow sections (4) of each deviation circuit (3) are in fluid communication with one another.

26. The plant of claims 24 or 15, wherein the fluid communication among the outflow sections (4) of each deviation circuit (3) is achieved downstream of the deviator valve (V) of the deviation circuit (3).

27. The plant of any one of claims from 14 to 26, wherein each distributor (101) comprises a plunger piston (108) which is sensitive to changes in the flow rate transiting between the inlet conduit (103) and the delivery conduit (104) and which slides within a sliding seating (109) in accordance with the change in flow rate detected; the plunger piston (108) controlling the at least a distribution organ (118).

28. The plant of claim 27, wherein the plunger piston (108) exhibits a first end (110) which acts on the fluid flow rate transiting between the inlet conduit (103) and the delivery conduit (104).

29. The plant of claim 27 or 28, wherein it comprises mechanical command means (131) for transmission of movement between the plunger piston (108) and the at least a distribution organ (118).

30. The plant of claim 29, wherein the mechanical command means (131) comprise a channel (132) afforded on the plunger piston (108), engaged slidably and progressively by a wedge-shaped protuberance (133) of the at least a distribution organ (118).

31. The plant of claim 20, wherein the at least a distribution organ (118) comprises a liner (122), slidable in a sliding seating (123), for intercepting the inlet (119), the outlet (120) and the discharge outlet of the distribution organ (118); the pilot piston being slidably housed internally of the liner (122).

32. The plant of claim 31, wherein the liner (122) together with the pilot piston (124) housed therein defines an auxiliary chamber (H) in fluid communication with the deviation circuit (3) for activating the pilot piston (124) with at least a part of the fluid flow transiting in the by-pass circuit (2).

33. The plant of claim 31 or 32, wherein the liner (122) is provided with through-holes (125) for placing the pilot piston (124) in fluid communication with the inlet (119) and the outlet (120) of the respective distribution organ (118) and with the discharge outlet (121) of the respective distribution organ (118).

34. The plant of claim 30 or 31, wherein the wedge-shaped protuberance (133) is associated to the sliding liner (122).

35. The plant of claim 18, wherein the obturator (105) is a slide valve and is translatable along a sliding direction (X), and is activated by a fluid pressure in the activating chamber (135).

36. The plant of any one of claims from 14 to 35, wherein the obturator (105) comprises at least a first valve (139) associated to a by-pass conduit (138) for closing or at least partially opening the by-pass conduit (138) following activation of the obturator (105).

37. The plant of claim 14, wherein each hydraulic distributor (101) comprises two distribution organs (118) for achieving a reverse functioning of the user (U).

38. The plant of claims 18 and 37, wherein each distributor further comprises two activation chambers (118), acting on opposite ends of the obturator (105) in order to move the obturator (105) according to two inversely-directed functioning regimes.