Abstract:
The invention relates to an electromagnetic valve for distributing cryogenic propellant for a space launch vehicle. The valve comprises two seats each oriented in a direction opposite to the other seat; a passage connecting the seats; and two shutters opening and closing the seats. The valve also comprises a magnetic circuit with a magnetic coil and a magnetic plunger that is driven by the magnetic flux of the coil and which in turn drives the shutters relative to their respective seats so as to open and close the seats. The plunger is placed between the shutters such that each shutter closes its seat by moving the plunger away from the corresponding seat. The movement for opening a seat is performed by moving the plunger towards the seat so that it does not crush the shutters against their seats.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit, under 35 U.S.C. §119, of BE 2015/5306 filed May 19, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
       FIELD 
       [0002]    The invention relates to the field of electromagnetic valves. More particularly, the invention relates to an electromagnetic ball valve for supplying cryogenic fluid, such as propellant, to a space aircraft. The invention also discloses a distribution valve controlled by an electromagnetic valve. 
       BACKGROUND 
       [0003]    A rocket is propelled with the aid of fuel and oxidizing agent. The fuel is generally propellant, which is contained in tanks and then distributed under cryogenic conditions in order to supply the thrusters in a precise manner, solenoid valves are connected to the tanks. The valves generally have electromagnetic actuators that utilize the current of the electric network of the rocket. The actuators must adapt to the amperage available over the network. 
         [0004]    In order to keep an electromagnetic valve open, it is necessary to supply current continuously to the coil of the valve. However, the current that circulates there causes the valve to heat up, in some cases to as much as 100° C., which risks igniting the fuel. 
         [0005]    The fuel and the propellant circulate in gaseous form and at a temperature reaching −200° C. and a pressure of approximately 400 bar. This pressure exerts destructive forces on the sealing elements, as do the mechanical vibrations of a rocket during take-off thereof. These vibrations can translate into accelerations of 60 g, which speed up the wear of sealing surfaces, together with the closing motion impacts. 
         [0006]    Document FR 2 487 942 A1 discloses a valve with a distribution level and a regulation level of the distribution level. The distribution level comprises two balls cooperating with two opposite seats. A shaft disposed between these balls makes it possible to open and close them selectively, and a piston with bellows makes it possible to actuate one of these balls. The piston is controlled by the regulation level, which comprises two balls also connected by a shaft and held in a closed position by a spring. An electromagnetic actuator with a tappet plunger pushes one of the balls, which in turn pushes the other ball via the shaft. 
         [0007]    This configuration is bulky. In addition, the ball cooperating with the plunger balls is exposed to significant forces, which degrade the seat of the ball, and therefore the seal deteriorates with use. Indeed, the closing motion means that the seat absorbs the kinetic energy of the plunger of the electromagnetic valve. At the same time, the tappet of the plunger is progressively work-hardened under force in order to crush the ball against its seat. Consequently, it is not possible to assure effective centring and correct plating of the ball towards its seat, and therefore the seal is again compromised. It would therefore be beneficial to propose a valve with a ball pushed from its seat from the corresponding orifice. 
       SUMMARY 
       [0008]    The object of the invention is to solve at least one of the problems posed by the prior art. More precisely, one object of the invention is to increase the longevity of an electromagnetic ball valve. A further object of the invention is to improve the compactness of an electromagnetic valve. 
         [0009]    The invention relates to an electromagnetic valve, in particular for cryogenic fluid, the valve comprising: two seats each oriented in a direction opposite to the other seat; a passage connecting the seats; two shutters, which each cooperate with one of the seats so as to be able to block and open the seat; a movable tappet in contact with the shutters so as to transmit the opening and closing movements from one shutter to the other; a magnetic circuit intended to convey a magnetic flux originating for example from a magnetic source; this valve being noteworthy in that the tappet comprises a magnetic material and defines a variable air gap in the magnetic circuit so as to be able to be driven by the magnetic flux in order to move the shutters relative to their respective seats. 
         [0010]    In accordance with various advantageous embodiments of the invention the tappet is disposed between the shutters and possibly between the seats. 
         [0011]    The invention also relates to an electromagnetic valve, in particular for cryogenic fluid, the valve comprising: two seats, each oriented in a direction opposite to the other seat; two shutters, which each cooperate with one of the seats so as to be able to block and open the seat; a passage connecting the seats; a magnetic circuit with a magnetic plunger able to be driven by a magnetic field source, the plunger moving the shutters relative to their respective seats; the valve being noteworthy in that the plunger is placed between the shutters such that each shutter closes its seat by moving the plunger away from the seat. 
         [0012]    In accordance with various advantageous embodiments of the invention the valve comprises tappets cooperating with the shutters, in various instances each tappet being able to move one of these shutters by passing through the associated seat. 
         [0013]    In accordance with various advantageous embodiments of the invention at least one, or each tappet is mounted movably relative to the plunger so as to be retractable in the plunger, in various instances the plunger comprising at least one or two springs configured to deploy the tappets outside the plunger. 
         [0014]    In accordance with various advantageous embodiments of the invention at least one, or each tappet, comprises a portion of reduced thickness cooperating with one of the shutters. 
         [0015]    In accordance with various advantageous embodiments of the invention the plunger comprises a through-duct configured to connect the seats of the passage. 
         [0016]    In accordance with various advantageous embodiments of the invention the valve comprises at least one plunger guide, in various instances two plunger guides are disposed on either side of the plunger. 
         [0017]    In accordance with various advantageous embodiments of the invention at least one, or each seat, is formed on a plunger guide, and at least one, or each plunger guide, is made of nonmagnetic material. 
         [0018]    In accordance with various advantageous embodiments of the invention the valve comprises at least one or two shutter carriers, each shutter carrier being configured to center its shutter relative to the associated seat during the opening and closing movements of the shutters. 
         [0019]    In accordance with various advantageous embodiments of the invention the valve comprises a magnetic field source, in particular a coil, one of the seats being disposed in the interior of the magnetic source, in various instances the passage passing through the magnetic source. 
         [0020]    In accordance with various advantageous embodiments of the invention the valve comprises a plunger spring holding the plunger in a closed configuration in which one of the two shutters, referred to as the entry shutter, is closed, and in which the other of the two shutters, referred to as the exit shutter, is open. 
         [0021]    In accordance with various advantageous embodiments of the invention the valve comprises at least one shutter spring, in various instances two shutter springs configured to hold each associated shutter in a closed position against the associated seat. 
         [0022]    In accordance with various advantageous embodiments of the invention the passage comprises a side with an entry and an exit, and the plunger has a face configured to allow communication between the entry and the exit when the plunger is plated towards or against the entry exit side. 
         [0023]    In accordance with various advantageous embodiments of the invention the passage comprises an opening, in particular a third opening, which is distanced from the seats connected by the passage. 
         [0024]    In accordance with various advantageous embodiments of the invention at least one, or each shutter is a ball, in various instances having a diameter less than 4.00 mm, for example less than 2.00 mm. 
         [0025]    In accordance with various advantageous embodiments of the invention the passage is a regulation passage, and the valve additionally comprises a fluid distribution level in communication with the regulation passage, the distribution level comprising a distribution passage, a distribution entry with a seat, a distribution exit with a seat, and two valves selectively opening and closing the distribution entry seat and the distribution exit seat. 
         [0026]    In accordance with various advantageous embodiments of the invention the distribution valves are controlled by a distribution piston in communication with the regulation passage. 
         [0027]    In accordance with various advantageous embodiments of the invention the face of the plunger has a clearance in order to allow a communication between the entry and the exit when the plunger is plated towards or against the entry exit side. 
         [0028]    In accordance with various advantageous embodiments of the invention the plunger is placed between the shutters such that each shutter opens its seat by moving the plunger towards the seat. 
         [0029]    In accordance with various advantageous embodiments of the invention the seats are fixed. 
         [0030]    In accordance with various advantageous embodiments of the invention the valve is a three-way valve. 
         [0031]    In accordance with various advantageous embodiments of the invention each shutter is able to close off the circulation via the passage. 
         [0032]    In accordance with various advantageous embodiments of the invention the plunger remains in contact with the shutters in each position. 
         [0033]    In accordance with various advantageous embodiments of the invention the space between the shutters is constant, or the space between the shutters is greater in a closed position than in an open position. 
         [0034]    In accordance with various advantageous embodiments of the invention the opening or the third opening is a supply path. 
         [0035]    In accordance with various advantageous embodiments of the invention at least one, or each tappet, is made of nonmagnetic material. 
         [0036]    In accordance with various advantageous embodiments of the invention at least one, or each shutter, is made of nonmagnetic material. 
         [0037]    In accordance with various advantageous embodiments of the invention the course of the plunger and/or of each tappet relative to the seats is less than 5.00 mm, for example less than 2.00 mm, e.g., less than 1.00 mm, in some instances less than 0.50 mm or 0.20 mm. 
         [0038]    In accordance with various advantageous embodiments of the invention the distribution piston is connected to the regulation passage via the seat that uses the regulation passage. 
         [0039]    In accordance with various advantageous embodiments of the invention the entry of the regulation passage communicates with the distribution entry independently of the opening or the closing of the valve. 
         [0040]    In general, the advantageous embodiments of each subject of the invention can also be applied to the other subjects of the invention. Insofar as feasible, each subject of the invention can be combined with the other subjects. 
         [0041]    The present valve has a more durable operation than know valves. The regulation level maintains its tightness in spite of the repetition of the actions. The surfaces providing the seals are exposed to weaker forces, both during the opening and the closing. The invention also proposes a solution decoupling the plunger from the shutters, which makes it possible to utilize the inertia of the plunger without creating any direct impact on the shutters. These benefits are maintained in spite of short response times and elevated autoclave pressure, for example reaching 400 bar. 
     
    
     
       DRAWINGS 
         [0042]      FIG. 1  shows an electromagnetic valve in a closed position, according to various embodiments of the invention. 
           [0043]      FIG. 2  shows the electromagnetic valve in an open position, according to various embodiments of the invention. 
           [0044]      FIG. 3  shows an enlargement of a distribution level in a closed position, according to various embodiments of the invention. 
           [0045]      FIG. 4  shows an enlargement of the distribution level in an open position, according to various embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    In the following description, the terms interior or inner and exterior or outer relate to a positioning relative to the axis of movement of the plunger. The axial direction corresponds to the direction along the movement axis of the plunger. 
         [0047]      FIG. 1  shows an electrically actuated valve  2 , in various instances an electromagnetically and mechanically actuated valve. The valve  2  makes it possible to generate a flow of a pressurized, for example gaseous, fluid. The valve  2  is shown here in a closed state, the valve being in the state in the absence of electrical supply. However, the valve could be configured so as to remain open at rest and so as to close when energized. 
         [0048]    The valve  2  comprises a distribution level  4  allowing the distribution of the fluid, and a regulation level  6 , or control level  6 , controlling the distribution level  4 . The valve  2  can comprise a main body  8 ; in various instances common to the two levels, or alternatively formed in two parts. The regulation level  6  can comprise a ferromagnetic frame  9  making it possible to form a magnetic circuit in the regulation level  6 . The frame  9  can form a material block with an inner chamber. The valve has an entry  10  common to the distribution level  4  and to the regulation level  6 . 
         [0049]    The distribution level  4  comprises a distribution passage  12  connecting a distribution entry  14  with a seat to a distribution exit  16  or user port. The distribution passage  12  optionally comprises an exhaust  18 , possibly with a seat, the exit  16  being between the entry  14  and the exhaust  18 . The distribution level  4  also comprises distribution valves ( 20 ;  22 ) cooperating with the seats of the distribution level  4  so as to block them. The valves ( 20 ;  22 ) are fixed to one another and are held in the closed position by a spring  24 . 
         [0050]    The distribution valves ( 20 ;  22 ) are controlled by a distribution piston  26  which is actuated by the pressure of the pressurized fluid of the valve  2 . The piston  26  can be a piston  26  having bellows  28 , or can be a piston inserted into a bore of corresponding diameter. The interior of the bellows  28  can be in communication with the nearby exhaust  18  with the aid of an orifice  30 . The piston  26  is accommodated in a chamber  32  in which the pressure variations move the piston in translation; this translation is communicated to the valves ( 20 ;  22 ) via a rod  34 . The pressure in the chamber  32  of the piston is controlled by the regulation level  6 . The piston  26  assures a mechanical, pneumatic/hydraulic actuation. 
         [0051]    The regulation level  6  comprises a regulation passage  36  connecting a regulation entry  38  with a seat to at least one regulation exit  40  or third opening  40 . The regulation exit  40  is in hydraulic communication with the piston  26  of the distribution level  4  via a conduit  42 . When the regulation level  6  opens, the pressure at the entry  10  of the valve  2  is thus exerted onto the piston  26  and moves it. 
         [0052]    In various embodiments, the regulation passage  36  can comprise a regulation exhaust  44  with a seat, the regulation exit  40  being between the regulation entry  38  and the regulation exhaust  44 . The regulation exhaust  44  accelerates the reduction in pressure on the piston  26  when the regulation level  6  is shut off. 
         [0053]      FIG. 2  shows the valve  2  in the open position. The regulation level is open and allows the pressure of the pressurized fluid to act in and on the distribution level. 
         [0054]    The regulation level is open. The fluid passes through this level. A balance of the pressures is reached between the entry  38  and exit  40  of the level via the regulation passage  36  of the level. The conduit  42  communicates this pressure to the piston  26 , which shifts the valves ( 20 ;  22 ). These then occupy an open position, in which the entry valve  20  opens its seat whereas the exhaust valve  22  closes its seat. The distribution entry  14  then communicates with the distribution exit  16 , in various instances directly. The valve  2  is open. 
         [0055]      FIG. 3  shows an enlargement of the regulation level  6  in the closed position, at rest, when the valve is not electrically supplied. The control level is not shown. The closed state of the regulation level  6  can be obtained by blocking the entry  38  thereof and/or by blocking the exit  40  thereof. 
         [0056]    The regulation entry  38  comprises an entry shutter  46 , such as an entry ball  46  making it possible to close the entry. The ball  46  can be disposed upstream of the entry seat, such that the pressure of the fluid keeps the entry closed, thus conferring an autoclave character. A spring  48  can participate in this closing effect. The choice of a ball  46  is advantageous because this element can be produced with strict tolerances of sphericity in the order of a micrometre, which limits leaks. The ball  46  can be impacted on its seat so as to deform the seat so that the sealing interface is more fitted. 
         [0057]    The regulation exhaust  44  can comprise an exhaust shutter  50 , such as a ball  50  on the downstream side of the seat in order to seal the seat, so that the pressure can contribute to opening the exhaust shutter. It should be noted that the two seats of the regulation level  6  are turned opposite one another. The seat faces each receiving a shutter face in the opposite direction to where the other seat is located. The shutters ( 46 ;  50 ) are placed in separate chambers, in various instances separated by another chamber; in this case the regulation passage  36 . In the shown state the exhaust ball  50  is spaced apart from its seat such that the two faces of the piston remain at the pressure of the exhaust, that is to say with a pressure balance. The balls ( 46 ;  50 ) can be made of ceramic material in order to increase their durability and in order to limit their inertia. Their diameter can be equal to 1.59 mm, and the corresponding diameter of the orifices of the seats can be equal to 1.12 mm. These dimensions limit both the mass and the effects of the pressure of the fluid on the balls, which resist opening. An exhaust spring  51  acts on the exhaust shutter in order to hold it closed. 
         [0058]    The regulation level  6  comprises a magnetic actuation means. The level can comprise a coil  52 , which in various instances surrounds the regulation passage  36  and/or the regulation entry seat and/or the entry shutter  46 . The coil  52  can comprise a plurality of units (a plurality of solenoids) disposed axially side-by-side and/or fitted one inside the other. The coil  52  can be disposed between the entry  38  and the exit  40  of the regulation level  6 . The regulation passage  36  can also be surrounded by the magnetic frame  9  forming the magnetic circuit. The passage  36  comprises a face to which the entry  38  and the exit  40  lead. As a result, they are closer to one another and the pressure losses are limited for quicker reactions. However, it is conceivable to place the exit of the exhaust side relative to the magnetic means. 
         [0059]    The regulation level  6  comprises a magnetic plunger  54 , which is disposed in the interior of the coil  52 , where it is subjected to the magnetic flux of the magnetic circuit. The magnetic plunger  54  is disposed between the shutters ( 46 ;  50 ) so as to be able to open each seat by moving towards the seat and by pushing the corresponding shutter. The regulation level  6  becomes axially shorter. By moving the plunger  54  away from the seat, the shutter closes the seat again by moving towards the seat. Each shutter is pushed or pushes towards the plunger  54 . 
         [0060]    The plunger  54  can form a movable face of the passage  36 . The plunger  54  can comprise a ferromagnetic material so as to direct magnetic flux field lines. The plunger  54  is movable, and the movements thereof make it possible to open and close the regulation level  6 . The plunger  54  can have a passage  55  connecting the entry  38  to the exhaust  44 . This passage is optional because the controlled leaks around the plunger  54  can be sufficient to balance the pressures depending on the prevailing pressures and the time of the desired response. 
         [0061]    At least one, or each shutter ( 46 ;  50 ) can comprise a ball, and in various instances a ball carrier  56  or shutter carrier  56 . Each ball carrier  56  can comprise an orifice allowing circulation from one face to the other. However, the presence of this orifice is not indispensable because the leaks, in various instances controlled, around the ball carrier  56  can be sufficient to reach the pressure actuating the piston of the distribution level. Each ball carrier  56  can make it possible to center its ball ( 46 ;  50 ) and to form an intermediary with the associated spring ( 48 ;  51 ). 
         [0062]    The regulation level  6  can comprise tappets  58  driven by the plunger  54 . These cooperate with the shutters ( 46 ;  50 ). The tappets  58  can push the shutters ( 46 ;  50 ) away from their seats so as to allow an opening and a circulation of fluid via the passage  36 . Each tappet  58  can also move away from its associated shutter ( 46 ;  50 ) such that the latter returns to its seat in order to assure a seal. 
         [0063]    The tappets  58  can be mounted movably relative to the plunger  54 . The plunger  54  can comprise cavities  60  receiving portions of tappets  58 , and in various instances elastic means such as springs  62 . The tappets  58  can thus retract and extend relative to the plunger  54 . For each shutter ( 46 ;  50 ), the spring  62  of the tappet pushes in the direction opposite the shutter elastic means ( 48 ;  51 ). It is possible to create a mechanical chain, in various instances continuously, from one shutter ( 46 ;  50 ) to the other. In various instances, this makes it possible to eliminate the play between the tappets  58  and the shutters ( 46 ;  50 ), and also the contact impacts. 
         [0064]    The elastic means  62  of the tappets  58  are superordinate to the elastic means ( 48 ;  51 ) of the shutters ( 46 ;  50 ). The elastic means  62  of tappets  58  can be stiffer than the elastic means ( 48 ;  51 ) of shutters ( 46 ;  50 ). The opposite is possible, for example by acting on the preloads. 
         [0065]    The movement of the plunger  54  can be decoupled from the tappets  58  and therefore the shutters ( 46 ;  50 ). The plunger  54  can have a longer course than the movement necessary to open a shutter ( 46 ;  50 ). It is therefore possible to modulate, and in various instances increase, the air gaps  64  on either side of the plunger  54 . 
         [0066]    The plunger  54  can comprise stop surfaces, in particular axial stop surfaces, cooperating with the tappets  58 . The elastic means  62  of the tappets  58  can then be less stiff than the elastic means ( 48 ;  51 ) of the shutters ( 46 ;  50 ). This arrangement makes it possible to shift the mechanical play, such that the play is no longer present at the shutters, but between the plunger  54  and the tappets  58 . The interfaces with the shutters ( 46 ;  50 ) are thus preserved over time. 
         [0067]    At least one, or each tappet  58 , can be made of an nonmagnetic material, for example in order to avoid magnetic short circuits. They can comprise portions of reduced thickness, such as needles passing through each seat. A shutter ( 46 ;  50 ) can then be actuated from the face opposite the seat. 
         [0068]    The seats of the regulation level can be formed on connected parts  66 , in various instances made of nonmagnetic materials. They can also serve as a tappet guide  66 . At least one, or each tappet guide  66  can comprise a guiding surface in which the corresponding tappet  58  slides. A passage can be formed between each or at least one pair constituted by a tappet  58  and tappet guide  66 , for example on the tappet  58 . This passage allows a circulation of fluid and/or a balancing of the pressures. 
         [0069]    A regulation spring  68  can plate the plunger  54  in its closed position. This spring  68  bears against the face incorporating the entry and the exit. The regulation passage  36  passes through this spring. 
         [0070]    The tappets  58  are introduced into the plunger  54 . However, each tappet interface can be brought towards the adjacent shutter. For example, these interfaces can be in the interior of the tappet guides. The plunger can comprise bearing surfaces introduced into, and sliding in the interior of the guides. These guides can then be plunger guides. 
         [0071]      FIG. 4  is a view of the valve in the open position. The actuation means  52  are energized. Current circulates in the coils  52 . 
         [0072]    The magnetic means  52  generate a magnetic flux in the magnetic circuit of the frame, and therefore a force tends to close the air gap  64  by moving the plunger  54  towards the entry shutter  46 . By means of the entry tappet  58 , the plunger pushes the entry shutter  46  out of its seat and opens the regulation level  6 . The opening can be partial. It allows a circulation or a balancing of the pressures, making it possible to actuate the distribution level and to open it as shown in  FIG. 2 . 
         [0073]    The different embodiments presented above can be combined. Different arrangements between the entry, the exit and the exhaust are envisioned. The entry and the exit can be on two opposite faces of the passage and/or relative to the plunger. The plunger can be fitted in the passage. The regulation level has three paths, but could have two paths, similarly to the valve.