Abstract:
An electrically operated hydraulic valve comprises a valve assembly that provides a common valve passageway, an inlet port, an outlet port and a return port connected to the passageway and an axially movable valve device which allows in a first position fluid flow between the outlet port and the return port while closing the inlet and in a second position, axially displaced from the first position, fluid flow between the inlet port and the outlet port while closing the return port. A spring provides a restoring force urging the valve device to its first position. An electrically operated actuator coupled to the valve device comprises a permanent magnet and a cooperating electrical coil having an associated magnetic core, one or other of the magnet and the coil constituting a stator and the other constituting an armature which is coupled to the valve device to move it from the first position to the second position. The actuator is disposed for operation by an electrical supply which provides a unidirectional current pulse to the coil.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to electrically operated hydraulic valves and particularly to such valves as may be used in systems for the extraction of fluid hydro-carbons from subsea locations. 
       BACKGROUND TO THE INVENTION 
       [0002]    There are two principal difficulties in achieving an acceptable design of an electrically operated valve for use in the foregoing circumstances. One is the limited availability of electrical power. Another is the likelihood that the hydraulic fluid will be contaminated with particles. 
         [0003]    The general object of the invention is to provide a low-power valve which can tolerate use with hydraulic fluid that may be contaminated with particles having a maximum particle size greater than 100 microns. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides an electrically operated hydraulic valve comprising a valve assembly that provides a common passageway, an inlet port, an outlet port and a return port connected to the passageway and an axially movable valve device which allows in a first position fluid flow between the outlet port and the return port while closing the inlet and in a second position, axially displaced from the first position, fluid flow between the inlet port and the outlet port while closing the return port. A means providing a restoring force urges the valve device to its first position; and an electrically operated actuator which is coupled to the valve device comprises a permanent magnet and a cooperating electrical coil having an associated magnetic core. One or other of the magnet and the coil constitutes a stator and the other constitutes an armature which is coupled to the valve device to move it from the first position to the second position. The actuator is disposed for operation by an electrical supply which provides a unidirectional current pulse to the coil. 
         [0005]    In some embodiments of the invention the valve device comprises two opposed poppets engageable with respective valve seats one at each end of the said valve passageway, the inlet port and the return port being in communication according to the position of the valve device with respective ends of the valve passageway and the outlet port being in communication with the valve passageway at a location intermediate the ends thereof. Each poppet may comprise a head for engaging the respective seat and a nose which extends within the valve passageway to the nose of the other poppet. 
         [0006]    In another embodiment of the invention the valve device comprises a valve spool having a lateral valve chamber and the said ports intersect the valve passageway at locations spaced apart along the passageway. The outlet port may intersect the valve passage at a location between and substantially equidistant from the locations where the return port and the inlet port intersect the valve passageway. 
         [0007]    In this embodiment, the valve chamber may have end surfaces of different effective area whereby fluid pressure in the valve chamber can urge the valve device towards the first position. The valve passageway may be a blind bore and the valve device may have an internal relief passage extending between its ends. 
         [0008]    In any of these embodiments the permanent magnet is preferably a cylindrical magnet and the permanent magnet, the coil and a cylindrical magnetic core are coaxially arranged. The coil and the permanent magnet may both be disposed within an annular space between outer and inner parts of the magnetic core. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  illustrates sectionally and partly schematically one embodiment of a valve according to the invention. 
           [0010]      FIG. 2  illustrates a modified version of the valve shown in  FIG. 1 . 
           [0011]      FIG. 3  illustrates another embodiment of a valve according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIG. 1  illustrates a first embodiment of the invention. The illustrated valve is contained within a generally cylindrical housing  1  of which the interior constitutes a main chamber  2 , which has an interior step defining a well  3  at the right-hand end of the chamber. The interior of the well is partitioned from the chamber  2  by a bulkhead  4 . For the sake of convenience, the right-hand end of the housing and parts associated therewith are termed ‘lower’ in this description and the left-hand end and parts associated therewith are termed ‘upper’. This nomenclature is employed because it is customary, though not essential, for the valve actuator to be disposed in a subsea module with its central axis disposed upright. 
         [0013]    The bulkhead  4  defines a passageway  5  between two valve seats, in this embodiment frustoconical valve seats  6  and  7  disposed at the lower end and at the upper end respectively of the passageway  5 . Extending into the passageway  5  from the lower end is a ‘lower’ poppet  8 . This poppet has a nose  9  that is substantially smaller than the passageway  5  so that particulate matter can be carried through the passageway. The poppet  8  has a frustoconical head  10  which can seal against the respective valve seat  6 , and a short rear shank  11 . To the rear of the head is an annular shoulder  12  against which bears one end of a return spring  13 , which is carried on the shank  11 . The other, lower, end of this return spring end bears against a datum provided by the lower end wall  14  of the housing  1 . This return spring is a means of providing a bias to keep the valve  8  normally closed. 
         [0014]    Opposing the lower poppet is a ‘upper’ poppet  15  which is generally similar to the valve  8 . Its nose extends into the passageway  5  between the valve seats  6  and  7  and into abutment with the nose of the valve  8 . By virtue of the spring  13  the two poppets can move in unison and constitute in effect a single elongate axially movable valve device. The upper poppet  15  has a head  16  which can make sealing engagement with the upper seat  7  and the upper poppet has a shank  17  extending axially into engagement with a yoke  18  which forms part of an armature of a linear electromagnetic actuator, denoted generally by the numeral  19 . 
         [0015]    Extending into the well  3  through the lower wall  14  is a passageway  20  constituting a fluid inlet port. This port is connected by any convenient means to a source of hydraulic fluid under pressure. Extending into the passageway  5  between the valve seats  6  and  7  and in particular through the side wall  21  of the valve housing  1  and through the bulkhead  4  is a passageway  22  constituting a fluid outlet port, or ‘function’ port. This passageway  22  is generally aligned with the location where the noses of the poppets  8  and  15  engage each other. Extending into the main chamber  2  and in particular through the side wall  21  of the housing is a passageway  23  constituting a fluid return port or ‘vent’ port. 
         [0016]    From the description thus far it may be understood that the inlet port  20  is effectively closed by the lower poppet  8  and that when this poppet is closed the upper poppet  15  is lifted from its seat  7  to provide communication between the fluid outlet port  22  and the fluid return port  23 . Conversely, if the upper poppet  15  is urged against its valve seat  7 , the lower poppet  8  is lifted, against the force of the return spring  13 , from its seat  6 . 
         [0017]    The size of the passageway  5  relative to the noses of the poppets can be made large enough to allow the passage of particulate contaminants in the hydraulic fluid controlled by the valve. In particular it can allow the passage of particles up to at least 100 microns. 
         [0018]    At the upper end of the chamber  2  is the actuator  19  aforementioned. In this embodiment, it is constituted by a permanent magnet stator  24  and a moving coil armature  25  coaxial therewith. The permanent magnet  24  is a cylindrical magnet disposed in an annular aperture  26  of a cylindrical E-section magnetic core  27  which has a cylindrical outer part  27   a  and a central solid cylindrical part  27   b . In an annular space between the central cylindrical part  27   b  of the magnetic core and the permanent magnet  24  is the moving coil armature  25  composed of an electrical coil to which there are electrical connections  28  extending through the upper end wall  29  of the housing  1 . The moving coil and its former (not explicitly shown) are fixed to the yoke  18 . 
         [0019]    The moving coil armature  25  may be energised by a short duration direct current pulse so as to move the yoke  18  and thereby the shank  17  of the upper poppet  15  in the downward (rightwards) direction against the force of the restoring bias provided by the return spring  13 . 
         [0020]    The movement required to lift the lower poppet  8  from its seat  6  is determined by the difference in the distances between the valve seats and the poppets when the poppets abut each other; it can be made just sufficient to allow the passage of particles of a predetermined maximum size, generally greater than 100 microns. Accordingly the electrical supply may be a simple direct current, low power supply which does not require any complex electronic switching circuit. 
         [0021]    In a ‘rest’ phase of the valve, the return spring  13  urges the lower poppet  8  against the respective valve seat, closing the outlet port  22  off from the inlet port  20  but allowing venting from the outlet port  22  to the return port  23 . 
         [0022]    Energisation of the moving coil actuator moves the upper poppet  15  against its seat, thereby opening the passage from the inlet port  20  to the outlet port  22  and closing the passage to the vent port  23 . 
         [0023]      FIG. 2  illustrates an embodiment similar to that shown in  FIG. 1 . The construction of the lower end of the valve is the same as that as shown in  FIG. 1  and need not therefore by described in detail. However, in this embodiment, the coil part of the actuator is the stator and the armature is constituted by a permanent magnet. In particular, the coil stator has an inner winding  25   a  on the central part  27   a  of the magnetic core  27  and an outer winding  25   b  adjacent the outer part of the magnetic core. The permanent magnet armature comprises a cylindrical permanent magnet  24   a  fixed to the yoke  18  and slidingly movable in the annular space between the outer and inner windings. Connections  28  provide direct current to the windings  25   a  and  25   b  of the coil  25 . 
         [0024]      FIG. 3  illustrates another embodiment of the invention. The illustrated valve is contained within a generally cylindrical housing  1  of which the interior constitutes a main chamber  2  which has an interior step defining a well  3   a  at the right-hand end of the chamber. In this embodiment the well is occupied by a valve block  30 , which has a valve passageway  31  constituted by a blind bore extending axially from the upper end of the block almost to the lower end. Within this bore  31  is slidingly moveable a single elongate axially movable valve device, comprising a valve spool  33 , which at its upper end is secured to a yoke  18 . A bias urging the yoke  18  and thereby the valve spool, in the leftwards (upward) direction is provided by a return spring  34  between the yoke and the upper face  32  of the valve block  30 . 
         [0025]    Communicating with the valve passageway  31  are three ports, the fluid inlet port  20 , the fluid outlet or ‘function’ port  22  and the fluid return or ‘vent’ port  23 . The fluid inlet port  20  comprises a passage extending from the exterior through the side wall  21  of the housing  1  and the valve block  30 . The fluid outlet port  22  comprises a passage through the side wall of the housing and the valve block. The fluid return port  23  comprises a passage  23   a  through the valve block  30  from the passage  31  to the chamber  2  and a passage  23   b  from the chamber  2  through the side wall of the housing  1 . 
         [0026]    The three ports open into the valve passageway at locations which are spaced apart along the passageway  31 . The outlet port  22  where it intersects the passageway  31  is substantially equi-distant from the effective locations of the inlet port  20  and the return port  23 , i.e. where these ports intersect the passageway  31 . 
         [0027]    The valve spool  33  defines a valve chamber  35  comprising an annular peripheral recess. The end shoulders of this recess are separated by a distance slightly less than the sum of the effective width of the return port  23  and the effective distance between the inlet port  20  and the return port  23 . 
         [0028]    The bore  31  is stepped at a shoulder  36 , the lower end having a smaller bore than the upper end and the two ends of the valve spool are of different sizes, the lower end fitting within the smaller lower end of the bore  31  and the upper end fitting within the larger upper end of the bore  31 . The valve spool  33  also has a relief passage  37  extending from the chamber  2  along and inside the valve spool  33  to the lower end thereof. 
         [0029]    The valve spool is moveable against the force of the return spring  34  from the position shown in  FIG. 3  of the drawings towards the lower end of the housing. In the position shown the outlet port  22  is connected to the return port  23  by the valve chamber  35  and the inlet port  20  is closed. Movement of the valve spool  33  brings the spool to an intermediate position wherein the inlet port  20  is opened; then further movement of the valve spool allows full connection of the inlet port  20  to the outlet port  22  and closure of the return port  23 . The necessary stroke for the valve spool is approximately the effective width (in the axial direction) of the return port  23 . 
         [0030]    The relief passage  37  prevents any fluid or vacuum lock. Also, by virtue of, in this embodiment, a difference in the effective areas of the two ends of the valve chamber  35 , fluid pressure in the chamber  35  will tend to drive the valve spool  33  to a fail-safe position in which there can always be exhaust from the return port  23 . 
         [0031]    This embodiment of the invention, like those previously described, is adapted to accommodate the use of hydraulic fluid which may be contaminated with particulate matter. The valve can readily accommodate particles having a particle size greater than 100 microns. 
         [0032]    The valve spool  33  can be moved by an electrical actuator similar to that described with reference to either of the foregoing Figures, whereby either one of a stator and an armature is constituted by a permanent magnet and the other is constituted by a coil and an associated permanent magnetic core, all these elements being coaxial. In the described embodiment, the coil is stationary and the armature is a permanent magnet. In particular, the coil stator has an inner winding  25   a  on the central part  27   a  of the magnetic core  27  and an outer winding  25   b  adjacent the outer part of the magnetic core. The permanent magnet armature comprises a cylindrical permanent magnet  24   a  fixed to the yoke  18  and slidingly movable in the annular space between the outer and inner windings. Connections  28  provide direct current, i.e. a unidirectional current pulse, to the windings  25   a  and  25   b  of the coil  25 . Owing to the very short stroke required, the electrical supply may be a direct current, low power supply which does not require any complex electronic switching circuit.