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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a pressure compensated shear seal solenoid valve used in subsea hydraulic control systems for operating valves, blowout preventers and hydraulically actuated wellhead connectors. Such devices require pressurized hydraulic fluid, typically operated at 1500 or 3000 psi, for their operation. The solenoid valve of the present invention is used in the control of the flow of such pressurized hydraulic fluid. 
     These subsea hydraulic control systems typically consist of a group of accumulator bottles in which the pressurized hydraulic control fluid is stored, a control unit for operating the aforementioned solenoid valves, and high pressure lines or hoses to carry the hydraulic control fluid from the accumulator bottles to the control unit and its solenoid valves and thence to the function, such as open or close, of the designated valve, blowout preventer or wellhead connector. The pressurized hydraulic control fluid is stored in the accumulator bottles at the desired operating pressure of 1500 or 3000 psi. 
     Previous designs in the industry have suffered from such deficiencies as inadequate flow rates, unreliable operation, difficulty to service or repair and being too large which causes difficulties in fitting the required number of valves in the allowable space. It is therefore desirable to have a solenoid valve that offers improved flow rates over existing designs, ease of serviceability and reduced size for ease in designing hydraulic control systems. The pressure compensated shear seal solenoid valve of the present invention offers a substantial improvement by offering a solenoid valve that yields a substantially improved flow rate, ease of serviceability and reduced size. 
     2. Description of Related Art 
     U.S. Pat. No. 4,337,829 to V. Banzoli et al. shows a control system for subsea wellheads that comprises an electronic command and control unit, a valve actuating hydraulic electric unit, a power generator unit and interconnection devices for interconnecting the hydraulic lines for controlling the system from the surface. 
     A subsea control module is disclosed in U.S. Pat. No. 6,161,618 to W. C. Parks et al. The subsea control module consists of a lower portion with plate for carrying hydraulic couplings and hydraulic passages from valves to couplings, a one atmosphere dry nitrogen purged chamber in a pressure vessel dome contains electronics, wiring and solenoid valves and a mandrel for extending below for engagement with a central locking mechanism in a receiver baseplate. 
     U.S. Pat. No. 6,318,408 B1 to Y. Fukano et al. shows a directional control valve. 
     A method and apparatus hydraulic and electro-hydraulic control of subsea blowout preventer systems is disclosed in U.S. Pat. No. 6,484,806 B2 to M. Childers et al. 
     SUMMARY OF THE INVENTION 
     The pressure compensated shear seal solenoid valve of the present invention is designed for use in subsea hydraulic control systems for operating valves, blowout preventers and hydraulically actuated wellhead connectors. The pressure compensated shear seal solenoid valve includes a hydraulic section with a flow control member or piston for controlling fluid flow through the solenoid valve and a coil section that operates the piston. A manifold is positioned between the coil section and the hydraulic section with the coil section and the hydraulic section secured to the manifold. 
     The hydraulic section includes a valve body with fluid supply and outlet ports on an end face. An inlet flange and an outlet flange are secured to the valve body on opposite sides. Internal porting allows fluid communication between the inlet and outlet flanges and in turn with the fluid supply and outlet ports. A piston is positioned within the valve body and has a central bore therethrough. The piston is moveable between open and closed positions to control fluid communication between fluid supply and outlet ports. A supply seal plate and an outlet seal plate are positioned on opposite sides of the piston, with the outlet seal plate having an arcuate shaped fluid passageway to maximize flow rate while requiring a minimum amount of piston travel between its open and closed positions. 
     The coil section comprises a coil cover having a substantially cylindrical shape with a mounting flange disposed on one end with a solenoid section disposed within the coil cover. The solenoid section including an electrically operated coil, a fixed metal core and a moveable metal core axially positioned a predetermined axial distance from the fixed metal core. An end cap is arrayed on the coil cover on the opposite end from the mounting flange. A bore extends axially through the fixed metal core with a plunger positioned within the bore and extending from the bore a predetermined distance at either end. The plunger is impacted and moved by the moveable metal core when the electrically operated coil is energized and thereby moves the piston. A flux ring encircles a portion of the moveable core and is sealed thereto. A pair of electrical leads supply power to the electrically operated coil. 
     A principal object of the present invention is to provide a pressure compensated shear seal solenoid valve with an improved flow rate. 
     Another object of the present invention is to provide a pressure compensated shear seal solenoid valve that minimizes the piston travel required to open and close the valve. 
     A final object of the present invention is to provide a pressure compensated shear seal solenoid valve that allows the use of a smaller coil for its operation 
     These with other objects and advantages of the present invention are pointed out with specificness in the claims annexed hereto and form a part of this disclosure. A full and complete understanding of the invention may be had by reference to the accompanying drawings and description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and advantages of the present invention are set forth below and further made clear by reference to the drawings, wherein: 
         FIG. 1  comprises a perspective view of the pressure compensated shear seal solenoid valve. 
         FIGS. 2A and 2B  comprise a full sectional view of the pressure compensated shear seal solenoid valve taken along line  2 — 2  of  FIG. 1 . 
         FIG. 3  comprises an enlarged sectional view of the hydraulic section of the pressure compensated shear seal solenoid valve of  FIG. 2A  in the closed position, with the coil deenergized. 
         FIG. 4  comprises an enlarged sectional view of the hydraulic section of the pressure compensated shear seal solenoid valve of  FIG. 2A  in the open position, with the coil energized. 
         FIG. 5  comprises a perspective view of the piston of the pressure compensated shear seal solenoid valve. 
         FIG. 6  comprises a full sectional perspective view of the piston of the pressure compensated shear seal solenoid valve of  FIG. 5 . 
         FIG. 7  comprises a perspective view of the outlet seal plate of the pressure compensated shear seal solenoid valve. 
         FIG. 8  comprises a full sectional perspective view of the outlet seal plate of the pressure compensated shear seal solenoid valve of  FIG. 6 . 
         FIG. 9  comprises a full sectional perspective view of the coil section of the pressure compensated shear seal solenoid valve. 
         FIG. 10  comprises a full sectional perspective view of a plurality of the pressure compensated shear seal solenoid valves assembled into a manifold. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, and particularly to  FIG. 1  a perspective view of pressure compensated shear seal solenoid valve  10  of the present invention is shown. Pressure compensated shear seal solenoid valve  10  includes hydraulic section  12  and coil section  14 . Hydraulic section  12  and coil section  14  are secured to manifold  16  that is positioned therebetween by suitable securing means as bolts  18  and  20 , respectively. Attachment bracket  22  allows pressure compensated shear seal solenoid valve  10  to be secured to an appropriate support structure. 
     Pressure compensated shear seal solenoid valve  10  is shown in sectional view in  FIG. 2 . Coil section  14  is surrounded by outer compensation chamber  24  of a generally rectangular parallelepiped configuration with one of the ends secured to end section  26  by suitable means as welding. Bolts  25  secure outer compensation chamber  24  to manifold  16 . Outer compensation chamber  24  includes fittings  28  and  30  for attachment of a pressure transducer and a pressure compensator accumulator bottle (not shown). 
     Manifold  16  includes internal passages  32  which connect to fluid supply and fluid outlet connections  34  and  36 , respectively. Passages  32  connect to fluid supply and outlet ports  38  and  40  in hydraulic section  12 . Passages  32  are sealed to fluid supply and outlet ports  38  and  40  by seal subs  42 . Manifold  16  also includes plunger bore  44  centrally located therein for purposes to be explained hereinafter. 
     The details of construction of hydraulic section  12  are best seen in  FIGS. 3 and 4 . Hydraulic section  12  includes valve body  46  having fluid supply port  38  and fluid outlet port  40  formed therein. Inlet flange  48  and outlet flange  50  are secured to valve body  46  by bolts  52 . Inlet flange  48  includes inlet flange fluid port  54  which communicates with fluid supply port  38  while outlet flange  50  includes outlet flange fluid port  56  which communicates with fluid outlet port  40 . Seal rings in the form of O rings  58  ensure there is no leakage of pressurized hydraulic fluid from inlet flange fluid port  54  and outlet flange fluid port  56  to the outside. 
     Valve body  46  includes central chamber  60  in which piston  62  is disposed. Piston  62  includes piston neck  64  extending from valve body  46 . Seal ring  66  is positioned on the exterior of valve body  46  and seals valve body  46  to manifold  16  when assembled. The opposite side of valve body  46  has end cap  68  secured thereto by bolts  70  and sealed by seal rings such as O rings  72  and  73 . End cap  68  has recess  74  formed on its interior surface with piston spring  76  positioned therein. Piston  62  has central bore  78  therethrough, perpendicular to the axis of travel of piston  62 . Shear seal rings  80  are disposed within central bore  78  with urging means in the form of coil spring  82  positioned therebetween to urge shear seal rings  80  outwardly toward supply and outlet seal plates  84  and  86 , respectively. Shear seal rings  80  include central bore  88  therethrough with tapered inner diameters  90  formed at their outer ends. Central bore  78  of piston  62  includes seal grooves  92  formed therein with O rings  94  disposed in seal grooves  92  and sealing the exterior of shear seal rings  80 . 
     Referring to  FIGS. 5 and 6 , details of construction of piston  62  are shown. Fluid vent groove  96  is formed in piston neck  64  and extends axially onto face  98  of piston  62 . Fluid vent grooves  96  allow vented fluids from hydraulic section  12  to flow out of body central chamber  60  to a vent port in manifold  16  (not shown). Piston  62  includes fluid bleeder ports  100  formed as shown in  FIGS. 3 and 5  for purposes to be explained hereinafter. 
     As shown in  FIGS. 3 and 4 , supply seal plate  84  and outlet seal plate  86  are generally cylindrical members with seal rings  102  on their exterior to seal within valve body  46 . Supply seal plate  84  includes port  104  therethough allowing fluid communication between inlet flange fluid port  54  and central bore  88  of shear seal rings  80 . Port  104  includes first fluid passageway  106  disposed on the side of supply seal plate  84  adjacent inlet flange fluid port  54  and is circular in cross section. Port  104  includes second fluid passageway  108  disposed on the side of supply seal plate  84  adjacent central bore  88  of shear seal rings  80  and is circular in cross section. First fluid passageway  106  and second fluid passageway  108  circular cross sections are of different diameters to give a gradual flow transition. When the circular cross section of second fluid passageway  108  of supply seal plate  84  is contained within the diameter of said tapered outlet face  90  of shear seal ring  80  when piston  62  is moved to an open position to allow fluid communication between inlet flange fluid port  54  and outlet flange fluid port  56 . 
     Referring to  FIGS. 7 and 8 , details of construction of outlet seal plate  86  are shown. Outlet seal plate  86  includes port  110  therethough allowing fluid communication between central bore  88  of shear seal rings  80  and outlet flange fluid port  56 . Port  110  includes first fluid passageway  112  disposed on the side of outlet seal plate  86  adjacent central bore  88  of shear seal rings  80  and is arcuate in cross section. Second fluid passageway  114  is disposed on the side of outlet seal plate  86  adjacent outlet flange fluid port  58  and is circular in cross section. The arcuate cross section of first fluid passageway  112  of outlet seal plate  86  has inner radius  116  and outer radius  118 . Outer radius  118  of first fluid passageway  112  of outlet seal plate  86  is substantially equal to the inside radius of tapered outlet face  90  of shear seal rings  80 . When piston  62  is moved to an open position to allow fluid communication between fluid supply port  38  and outlet port  40 , outer radius  118  of arcuate cross section of first fluid passageway  112  of outlet seal plate  86  is substantially coincident to the inside radius of tapered outlet face  90  of shear seal ring  80 . Inner face  120  of outlet seal plate  86  and inner face  122  of supply seal plate  84  are lapped to a polished finish to allow face to face sealing with shear seal ring  80 . 
     The details of construction of coil section  14  are best seen in  FIG. 9 . Coil section  14  includes coil cover  124  which has a substantially cylindrical shape with integral flange  126  disposed on one end. Solenoid section  128  is disposed within coil cover  124  and includes electrically operated coil  130 , fixed metal core  132  and moveable metal core  134  axially positioned a predetermined axial distance from fixed metal core  132 . Fixed metal core  132  sealed at one end to the interior of coil cover  124  by seal rings  136 . Pressure transfer cap  138  is constructed of a suitable elastomeric material and is fitted on coil cover  124  on the opposite end from mounting flange  126 . Pressure transfer cap  138  is expandible and collapsible to accommodate pressure changes within coil section  14 . 
     Bore  140  extends axially through fixed metal core  132  and has plunger  142  positioned within bore  140 . Plunger  142  extends from bore  140  a predetermined distance at either end and plunger  142  is impacted and moved by moveable metal core  134  when electrically operated coil  130  is energized. Flux ring  144  encircles a portion of moveable core  134  and is sealed thereto by a plurality of seal rings  146 . Paired electrical leads  148  supply power to electrically operated coil  130 . Electrical leads  148  extend through pressure transfer cap  138  and are sealed by pressure transfer cap  138 . The interior of coil section  14  is filled with a predetermined amount of dielectric fluid  150  which displaces any air within coil section  14  and prevents ingress of foreign matter into coil section  14 . Fill ports  152  provide a means for filling coil section  14  with dielectric fluid  150 . Fixed metal core  132  and moveable metal core  134  have complimentary tapered faces  154  and  156  on their mating faces. Securing means in the form of snap ring  158  secures solenoid section  128  within coil cover  124 . 
     A typical sequence of operation for pressure compensated shear seal solenoid valve  10  is as follows. Pressurized hydraulic fluid is supplied from a manifold of accumulator bottles, well known to those of ordinary skill in the art, to fluid supply connection  34  in manifold  16 . The pressurized hydraulic fluid then flows through internal passage  32 , through seal subs  42  to inlet flange fluid port  54  and to supply seal plate  84 . The pressurized hydraulic fluid is then directed through shear seal rings  80  where the flow is stopped by outlet seal plate  86 , if coil  130  is deenergized, as shown in  FIG. 3 . When it is desired to supply pressure to a control function, coil  130  is energized and piston  62  is moved to the position shown in  FIG. 4 , where the pressurized hydraulic fluid flows through first fluid passageway  112  which is arcuate shaped and to second fluid passageway  114  and thence to outlet flange fluid port  56 , through seal subs  42  and internal passage  32  to fluid outlet connection  36 . The pressurized hydraulic fluid then is directed through appropriate piping to the control function being operated. 
     In a typical installation of pressure compensated shear seal solenoid valve  10 , it is often desired to install a plurality of valves  10  in an integrated unit commonly referred to as a multi-function manifold. Such a manifold allows for the functioning of multiple subsea devices such as valves, blowout preventers and hydraulically actuated wellhead connectors. Construction details of such a typical unit using a plurality of pressure compensated shear seal solenoid valves  10  are shown in  FIG. 10 . Manifold assembly  160  includes an outer compensation chamber  162  with a plurality of pressure compensated shear seal solenoid valves  10  mounted along one edge. Fill port  164  is provided to allow dielectric fluid to be added to manifold assembly  160  to fill its interior and protect pressure compensated shear seal solenoid valves  10  mounted therein. Electrical leads  148  extend to the rear of manifold assembly  160  for connection to the appropriate controls. Manifold assembly  160  can then be mounted in a convenient location on a subsea hydraulic control system to facilitate routing of the necessary piping. 
     The construction of our pressure compensated shear seal solenoid valve will be readily understood from the foregoing description and it will be seen that we have provided a pressure compensated shear seal solenoid valve that offers an improved flow rate and ease of serviceability. Furthermore, while the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalent alterations and modifications, and is limited only by the scope of the appended claims.

Summary:
A pressure compensated shear seal solenoid valve for use in subsea control systems is disclosed utilizing an arcuate cross section fluid passageway to improve flow rates, ease of serviceability and reduce size.