WO2021009776A1 - Solenoid operated three way hydraulic valve - Google Patents

Abstract

Present invention relates to an electrically actuated, three way, two position hydraulic valve incorporating electrical redundancy for its operation. The disclosed embodiment comprises three sets of ports namely pressure port (P), control port (C), and return port (R) of which control port (C) and return port (R) remains interconnected under the influence of spring and whenever both the coils of said valve are not electrically energized. Upon energisation of either of the redundant coils, the pressure port (P) and control port (C) are interconnected with return port (R) isolated. Communication of various fluid ports (P, R, C) is accomplished by means of a shuttling ball (12), selectively covering and uncovering fluid passages made inside valve seat (9) and return seat (13).

Description

SOLENOID OPERATED THREE WAY HYDRAULIC VALVE

TECHNICAL FIELD OF INVENTION

[0001] This invention relates to an electrically actuated, three way, two position hydraulic valve incorporating electrical redundancy for its operation.

BACKGROUND OF THE INVENTION [0002] US patent No.: 3578284 reveals a miniature two way - two position solenoid valve which is adapted for use as a pilot valve for a normally closed type flow control valve. This solenoid valve includes an orifice fitting which conducts the inlet fluid. However, the end of the orifice fitting is sealed by means of a ball forming a valve seat under the influence of compression applied over a reciprocating plunger through a spring. The solenoid coil upon energisation reciprocates the plunger against the spring thereby unseating the ball from the valve seat paving hydraulic inter-communication.

[0003] US patent No.: 8833731 B2 describes a two way - two position solenoid valve, which if not operated, connects one fluid port to other and vice versa. A solenoid coil after energization compresses a helical spring accomplishing the isolation of the fluid ports. A non return valve is provided between these fluid ports which interconnects the first and second fluid connections if the pressure in the second fluid connection is substantially higher than the pressure in the first fluid connection. This compact solenoid valve has just two ports, which makes it useful as a shut off valve to other hydraulic equipment with the solenoid valve energized only when the hydraulic equipment is required to function.

[0004] US patent application No.: 2013/0020515A1 reveals a three way - two position cartridge type solenoid distribution valve. This valve has two valve seat bores housed in a valve chamber along with a valve lifter operated under the influence of electromagnetic stage. Three hydraulic ports extend to the valve seat bores of which two hydraulic connections are interconnected at a given operating position. Upon energisation of the electromagnet, the valve lifter is drawn against the spring and hydraulic forces to accomplish the closure of one port by means of a ball attached to it enabling interconnection of other two ports. This embodiment, however, discloses a very complex valve chamber incorporating numerous components and sealing surfaces using rubber seals for preventing leakage. The maintenance and trouble-shooting of such configuration essentially needs labour having high level of skill and therefore remotely possible at the site where it is installed.

[0005] In addition to the shortcomings discussed above, these valves have a single coil which ceases to function in case of electrical short in their solenoid coil. Also, absence of suitable means for back EMF suppression may render the solenoid control electronics unserviceable after few cycles of solenoid operation.

SUMMARY OF THE INVENTION

[0006] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

[0007] According to an aspect, the present invention provides a solenoid operated three way two position hydraulic valve that comprises a hydraulic stage formed by a pressure port (P), a return port (R) and a control port (C) each having a passage in a manifold (4) with a seal to provide hydraulic isolation between the passages. An electrical stage is fastened to said hydraulic stage, wherein said electrical stage is formed by a casing housing a plurality of coils with the core consisting of combination of ferromagnetic bobbins and an axially slidable plunger defining an air gap there between. A retainer integrated in the valve is having a recess to accommodate a spring loaded shuttling ball that provides communication between the fluid ports (P to C or R to C) by means of selectively covering and uncovering fluid passages inside a valve seat and a return seat. The said valve has an energised state and a de-energized state.

[0008] In the de-energized state, spring force predominates the hydraulic force of the pressure port (P) causes the ball to cover passage of the valve seat, connecting the control port (C) and the return port (R) isolating the pressure port (P).

[0009] In the energised state, the coil causes an electromagnetic force (EMF) induced across the air-gap resulting in an attraction force between bobbin and plunger, in opposite to that of spring force such that the sum of electromagnetic force and the hydraulic force of the pressure port (P) predominates the spring force to cause the ball to cover the return seat, connecting the control port (C) and the pressure port (P) isolating the return port (R).

BRIEF DESCRIPTION OF DRAWINGS [0010] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0011] Figure 1 is a hydraulic schematic diagram of a three way, two position solenoid operated valve with solenoid coil in de-energised condition;

[0012] Figure 2 is a hydraulic schematic diagram of a three way, two position solenoid operated valve with solenoid coil in energised condition;

[0013] Figure 3 is a sectional view of invented three way two position solenoid valve with solenoid coil in de-energised condition; [0014] Figure 4 is a detailed view of hydraulic stage of invented solenoid valve as shown by figure 3;

[0015] Figure 5 is a sectional view of invented three way two position solenoid valve with solenoid coil in energised condition;

[0016] Figure 6 is an isometric view of retainer forming a component of the invented solenoid valve; [0017] Figure 7 is an end view showing mounting arrangement of the invented solenoid valve;

[0018] Figure 8 is a schematic of back EMF suppression scheme adopted for the solenoid valve; [0019] Figure 9 shows a hydraulic schematic diagram of the invented embodiment applied for piloting another hydraulic valve; and

[0020] Figure 10 shows an electromagnetic flux primary path using a simplified figure of the invented solenoid valve assembly.

[0021] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0023] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0024] It is to be understood that the singular forms“a,”“an,” and“the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to“a component surface” includes reference to one or more of such surfaces. [0025] By the term“substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic is intended to provide. [0026] Referring to figures. 1 through 10, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions, in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.

[0027] Those skilled in this technology can make various alterations and modifications without departing from the scope and spirit of the invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.

[0028] Figures 1-10 are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated, while others may be minimized. Figures 1-10 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.

[0029] In the foregoing detailed description of embodiments of the invention, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of embodiments of the invention, with each claim standing on its own as a separate embodiment. [0030] Disclosed herein is a three way, two position solenoid valve assembly incorporating redundant electrical coils for its operation. The solenoid valve can be interfaced with a separate manifold and can be used for piloting another hydraulic valve. The disclosed embodiment comprises three sets of ports namely pressure port, control port, and return port of which control and return ports remains interconnected under the influence of spring and whenever both the coils of said valve are not electrically energized. Upon energisation of either of the redundant coils, the pressure and control ports are interconnected with return ports isolated. Communication of various fluid ports is accomplished by means of a shuttling steel ball, selectively covering and uncovering fluid passages made inside valve seat and another return seat. Fluid flow through return port is also channelized to the core of the electrical stage for cooling. The said electrical stage is formed by said coils, diodes with the core consisting of combination of ferromagnetic bobbins and an axially slidable plunger defining an air gap there between. A paramagnetic ring sandwiched between the said bobbins functions to increase concentration of magnetic flux density across the air gap resulting low current required for operation of the said solenoid valve.

[0031] The hydraulic solenoid valve assembly which is an electro-hydraulic device operated through electrical energisation of coils. One or more coils after energisation accomplishes set of desired hydraulic inter-connections. The solenoid valves are classified based upon operating positions and number of hydraulic connections involved.

[0032] Referring to Figures 1 and 2, the disclosed embodiment is of a three-way two-position type with its general hydraulic representation is shown. As shown in these figures, the disclosed art has three hydraulic ports that is a pressure port (P), a return port (R) and a control port (C). A spring (26) keeps the port (R) connected to port (C) when the solenoid coil is de-energised. However, upon electrical energisation of the solenoid coils and with assistance of hydraulic pressure force, the connection of port (C) from port (R) is moved to port (P) with the same is shown by figure 2.

[0033] Referring to Figure 3, a hydraulic solenoid valve assembly (1), formed by a hydraulic stage (2) and an electrical stage (3) is illustrated. The hydraulic stage comprising the pressure port (P), the return port (R) and the control port (C) are capable of interfacing to corresponding suitable port in a manifold (4). An inlet screen (7) and various types of seals to accomplish hydraulic isolation between the passages are also housed in this stage with various passages along with components defining the passages. The electrical stage (3) houses a plurality of coils (29) and encapsulating an air gap (25) defined by a shim (28) abutting bobbin (31) and a plunger (21). The electrical stage (3) also houses means for back EMF suppression which is accomplished through a plurality of diodes (35) mounted over a printed circuit board (36) in the manner shown by figure 8.

[0034] High pressure hydraulic fluid is made available at pressure port (P) of solenoid valve assembly (1). Return port (R) is connected to return line which is usually further connected to reservoir of a hydraulic system. The control port (C), is where it is intended to communicate fluid flow from either of the ports (P) and (R). This selection is port communication i.e. either (R) to (C) or (P) to (C) depends upon the operational requirements of the system of which the hydraulic solenoid valve (1) is an integral part. A valve body (22) and the components encapsulated or mounted on the valve body (22) constitute hydraulic stage (2). A plurality of seals (6), (11) and (39) are provisioned to ensure leak tightness between port (P), (C) and (R) as shown. The inlet hydraulic flow from port (P) after flowing through passage (5) is screened by a conical filter screen (7). The filter screen (7) comprises of multiple micro holes which functions to remove contaminants in the incoming fluid of size greater than the micro hole size. The filter screen (7) has flange for support on a valve seat (9) as shown. To ensure accurate alignment of filter screen (7) inside valve body (22), the outer diameter of the valve seat (9) accurately confirms with the flange diameter of the filter screen (7). The fluid after screened through screen (7) passes through a passage (8)defmed by inner diameter of valve seat (9) as shown. Also, as per figure 3, since a ball (12) closes the other end of the passage, the hydraulic fluid flow available in the passage (8), cannot pass any further.

[0035] Referring to figure 3, 4 and 6, the ball (12) is assembled and allowed to translate between the gap defined by the valve seat (9) and a return seat (13). The translation of the ball (12) is however guided through a hole (42) made inside a retainer (14). The retainer (14) is like a cylindrical washer with four equi-spaced holes (41) and a recess (40) defined on both the faces of the retainer (14) to accommodate the flow passages as shown. A tip (45) of a push rod (15) under the influence of compression spring (26) forces the ball (12) in the position as depicted. Both the valve seat (9) and return seat (13) have peripheral sealing (10) and (17) respectively to prevent any fluid seepage across these. The return seat (13) is internally hollow with a space (44) defined internally to serve as a fluid passage and also for accommodating the tip (45) of push rod (15). The push rod (15) has a hollow pencil type construction with holes (47) and (48) defined for yet another fluid passage. A plunger (21) made up of ferromagnetic material accommodates the push rod (15) and also a compression spring (26) and spring seat (27) as shown. The spring (26) is sandwiched between an internal flange collar formed in plunger (21) and the spring seat (27). In addition, the plunger (21) axially guides spring (26) while transmitting the spring force directly to push rod (15) so as to keep the ball (12) in the position as shown. The spring seat (27) in addition to being internally hollow to define another fluid passage (53) also has a lower tail diameter axially assembled in a ferromagnetic bobbin (31). The passage (53) connects to air gap (25) by means of peripheral holes made in spring seat (27) as shown. The air gap (25) is defined by the gap between plunger (21) and a cylindrical shim (28) abutting bobbin (31). The shim (28) has a low thickness and is made up of paramagnetic material. The periphery of air gap (25) is defined by another paramagnetic ring (19) which is secured with bobbin (31) at one end and yet another ferro-magnetic flanged bobbin (18) at another end. The gap between the flanged bobbin (18) and inner surface of valve body (22) and return seat (13) defines yet another fluid passage (16) which further communicates to return port (R) as shown. To prevent fluid seepage suitable sealing (20) is provided on the periphery of flange portion of the flanged bobbin (18).

[0036] The ports (C) and (R) are accomplished through multiple peripheral drilled passages (43) and (46) respectively. Also, substantial gaps are provided between manifold port holes with corresponding (P), (C) and (R) port holes in valve body by introducing early butting of flange portion of valve body (22) with manifold (4). Adoption of this technique provides flexibility to position the respective manifold fluid ports (P), (C) and (R) anywhere within the peripheral reach of corresponding fluid passage ports in valve body (22).

[0037] The ring (19) and the flanged bobbin (18) are copper coils (29A) and (29B) wound over a spool (30) along the periphery of the bobbin (31). The spool (30) is made up of electrically non conductive material and is divided in two chambers to accommodate the coils (29A) and (29B).In addition, these coils (29A) and (29B) are terminated as individual wires for enabling interface with two independent electrical channels. The terminals of coils (29A) and (29B) are soldered to a printed circuit board (36) which houses circuitry for accommodating back EMF suppressing devices i.e. diodes (35 A) and (35B), in the manner as shown in figure 8. These diodes (35A) and (35B) are electrically isolated from each other and are specifically meant for coil (29A) and (29B) respectively. The printed circuit board (36) is fastened onto the spool (30) using screws and washers (33) and (34) at two places i.e. at either ends of spool (30). For interfacing with individual electrical systems, wire terminals (38) are further extended through a soft sleeve (37) from the printed circuit board (36). [0038] Now again referring to figure 3 and 4, it is also seen that the fluid through return port (R) remains available in the core of electrical stage (3) via fluid passages (46), (16), (44), (48), (47) and (53) till air gap (25) and remains connected to return port (R) for enabling cooling of electrical stage (3). This makes the entire solenoid valve assembly (1) tolerant to comparatively higher ambient operating temperatures.

[0039] Electrical stage (3) containing bobbin (31), ring (19), flanged bobbin (18), coils (29A)-(29B) and printed circuit board (36) is housed in a casing (32) in the manner as shown by figure 3. The casing (32) is made up of ferromagnetic material and is plated for magnetic insulation on its external surface. This eliminates the need of yet another paramagnetic casing needed for magnetic insulation of the solenoid valve assembly (1). Moreover, as depicted in figure 7 casing (32) has flanged means for fastening with the manifold (4) at four places using screws and washer (49) and (50). Also screws and washers (23) and (24) are used for fastening the electrical stage (3) to hydraulic stage (2). Moreover, wire terminals (38) are routable internally through manifold 4 thereby eliminating the need of thick environmental insulation or an additional tube for routing.

[0040] Solenoid valve assembly (1), when not energised or in de-energised state, remains in condition as depicted by figures 1 and 3. Now considering figure 3 and 4, supply pressure available through port (P) acts on ball (12), through fluid passage (8), over an effective diameter (Dl) as shown. However, the return pressure through port (R) acts on the ball (12), through fluid passages (46) and (44), over same effective diameter (Dl), but in opposite sense to that of force exerted by supply pressure through port (P). Therefore a net hydraulic force on the ball i.e. (Ps-Pr)*7t/4*D1² is exerted in order to further compress spring (26). Here (Ps) and (Pr) is supply and return pressure respectively. The force through spring (26) however exceeds the hydraulic force by a substantial margin and keeps the ball firmly abutted against valve seat (9), thereby keeping ports (P) and (C) disconnected from each other.

[0041] Electrical energisation of either of the solenoid coils (29A) or (29B) causes an electromagnetic force to be induced across the air-gap (25) resulting in an attraction force between bobbin (31) and plunger (21). This attraction force acts in opposite sense to that of spring (26) and increases with increasing amount of current fed to the coils (29A) or (29B).

[0042] Now referring to figures 4 and 5, upon attainment of a“pull-in” current value to the coils (29A) or (29B), the combination of the electromagnetic force and hydraulic force exceeds the spring force and causes the assembly of plunger (21) and push rod (15) to move towards bobbin (31) further causing the air gap (25) to reduce to (25’) which is equal to the thickness of shim (28). This also causes the ball (12) to shuttle inwardly until it butts the front end of return seat (13). This causes the communication of ports (P) and (C) through fluid passages (8), (40), (41) and (43) as shown. Thereby communication of supply pressure (Ps) to control port (C) is enabled. The pressure available through the control port (C) can be utilised to pilot yet another hydro-mechanical valve (51) as shown schematically in figure 9.

[0043] The primary magnetic flux lines produced due to energisation of coils (29A) and (29B) traverses a path as shown in figure 10. These primary flux lines are representatively shown as (52A), (52B), (52C) and (52D) and passes through ferromagnetic bobbin (31), casing (32) and flanged bobbin (18). It may also be seen provisioning of paramagnetic ring (19) in between ferromagnetic bobbin (31) and flanged bobbin (18) allows maximising the incidence of flux lines across the air gap (25’) with additional flux line (52A) also diverted to the air gap (25’). This results in efficient operation of solenoid valve assembly (1) with very low amount of un-useful magnetic flux. This arrangement also allows for low mass of plunger (21) and push rod (15) meaning low amount of current to either coils (29A) and (29B) is sufficient for“pull-in”. Also, with low mass inertia of plunger (21) and push rod (15), very low operational response times of solenoid valve assembly is achieved. Provisioning of a paramagnetic shim (28) ensures that under all times there exists an air gap (25’) which prevents permanent attachment of bobbin (31) with plunger (21) due to residual magnetisation and enables positive dropping out of solenoid valve assembly (1) whenever coils (29A) and (29B) are de-energised.

[0044] In case of solenoid valve assembly (1) is to be dropped out from figure 5 to figure 3, the current applied to coils (29A) or (29B) is withdrawn which results the spring force to once again dominate the hydraulic force which is (Ps- Pr)*7i/4*D2². Here (D2) is diameter of minor hole in return seat (13). The dominating spring force from spring (26) pushes the plunger (21), push rod (15) and ball (12) so that the ball closes the minor hole in valve seat (9) resulting isolation of port (P) from port (C) and interconnection of port (C) with port (R).

[0045] Electrical and hydraulic stages (3) and (2) of solenoid valve assembly (1) are sized such that the energization of either coils (29A) and (29B) leads to operation of the solenoid valve assembly (1). This makes the operation of the solenoid valve assembly (1) immune to electrical malfunction or shorts in any of the electrical systems associated with either of the coil (29 A) and (29B) enabling higher operational reliability.

[0046] The solenoid valve according to the present invention has a high degree of operational reliability for extended usage under extreme environmental conditions. The usage of the solenoid valve results in low operational response times for enabling a swift operation of a hydro-mechanical flow control valve. The usage of solenoid valve also results in minimal back electromagnetic force (EMF) emissions during operation. Also, the cartridge type solenoid valve with modular construction enables easy maintenance.

[0047] Although the invention has been shown and described with respect to certain preferred embodiment, it is obvious that equivalent alterations and modifications will occur to other skilled in the art upon the reading and understanding of the description.

[0048] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention.

[0049] It is understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms“including” and“in which” are used as the plain- English equivalents of the respective terms “comprising” and “wherein,” respectively.

Claims

Claims

1. A solenoid operated three way two position hydraulic valve (1), comprising:

a hydraulic stage (2) formed by a pressure port (P), a return port (R) and a control port (C) respectively having a passage in a manifold (4) with a seal to facilitate hydraulic isolation therebetween;

an electrical stage (3) fastened to said hydraulic stage (2), said electrical stage formed by a casing (32), the casing (32) housing a plurality of coils (29) with the core having a combination of ferromagnetic bobbins (31) and an axially slidable plunger (21) defining an air gap (25) therebetween; and

a retainer (14) having a recess (40) to accommodate a spring (26) loaded shuttling ball (12), said ball (12) facilitating communication between the fluid ports (P to C or R to C) by selectively covering and uncovering fluid passages inside a valve seat (9) and a return seat (13),

wherein

when the valve is in a de-energized state, the spring force exceeds the hydraulic force of the pressure port (P) which causes the ball (12) to cover passage (8) of the valve seat (9), connecting the control port (C) and the return port (R) isolating the pressure port (P);

when the valve is in an energised state, the coil (29) causes an electromagnetic force (EMF) induced across the air-gap (25) resulting in an attraction force between bobbin (31) and plunger (21), in opposite to that of spring force such that the sum of electromagnetic force and the hydraulic force of the pressure port (P) exceeds the spring force to cause the ball (12) to cover the return seat (13), connecting the control port (C) and the pressure port (P) isolating the return port (R).

2. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein an air gap (25’) is defined by a shim (28) abutting the bobbin (31) and the plunger (21) under energised state.

3. The solenoid operated three way two position hydraulic valve as claimed in claim 1 or 2, wherein, the electrical stage (3) further houses a paramagnetic ring (19) in between the ferromagnetic bobbin (31) and a flanged bobbin (18) to maximise the incidence of flux lines across the air gap (25’).

4. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein said return seat (13) is internally hollow with a space (44) defined to serve as a fluid passage.

5. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein said plunger (21) made of ferromagnetic material accommodates a push rod (15), the compression spring (26) and a spring seat (27), the spring (26) is sandwiched between an internal flange collar formed in plunger (21) and the spring seat (27).

6. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein said spring seat (27) is internally hollow to define fluid passage (53) and has a lower tail diameter axially assembled in a ferromagnetic bobbin (31), the passage (53) connects to air gap (25) by means of peripheral holes made in spring seat (27).

7. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein said retainer (14) is a cylindrical washer with four equi- spaced holes (41) and the recess (40) defined on both the faces to accommodate the flow passages.

8. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein, the hydraulic stage (2) further houses a conical filter screen (7) mounted on a valve seat (9) receives inlet hydraulic flow from pressure port (P) through passage (5), the filter screen (7) comprises multiple micro holes to remove contaminants.

9. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein a tip (45) of push rod (15) loaded by the compression spring (26) keeps the ball (12) in the position.

10. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein said energized state provides communication between pressure port (P) and control port (C) through plurality of fluid passages (8, 40, 41 and 43).

11. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein said de-energized state provides communication between return port (R) and control port (C) through plurality of fluid passages (46, 16, 44, 40, 41 and 43).

12. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein fluid flow through the return port (R) is channelized through a plurality of fluid passages (46, 16, 44, 48, 47 and 53) to the core of the electrical stage (3) for cooling.

13. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein the electrical stage (3) houses a plurality of diodes (35) mounted over a printed circuit board (36) to suppress the back EMF.

14. The solenoid operated three way two position hydraulic valve as claimed in claim 1, wherein the pressure available through the control port (C) is employed to pilot an another hydro-mechanical valve (51).