Abstract:
A jet pipe arrangement for a servo valve, the jet pipe arrangement including a jet pipe, at least two receivers in operable communication with the jet pipe. The jet pip arrangement further includes an electromagnet in direct magnetic communication with the jet pipe such that, in use, the jet pipe is movable in response to changes in a magnetic field created by the electromagnet to distribute flow from the jet pipe asymmetrically between the at least two receivers.

Description:
FOREIGN PRIORITY 
       [0001]    This application claims priority to European Patent Application No. 16156561.9 filed Feb. 19, 2016, the entire contents of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    This disclosure relates generally to a hydraulic servo valve. In particular, the disclosure relates to an electromagnetic jet pipe arrangement within a hydraulic servo valve. 
       BACKGROUND OF THE INVENTION 
       [0003]    Servo valves are generally used when accurate position control is required, such as, for example, control of a primary flight surface. Servo valves can be used to control hydraulic actuators or hydraulic motors. They are common in industries which include, but are not limited to, automotive systems, aircraft and the space industry. 
         [0004]    A known type of hydraulic servo valve is a flapper or jet pipe arrangement. In this arrangement, the primary components in the servo valve are the torque motor, flapper nozzle or jet pipe and one or more servos. 
       SUMMARY OF THE INVENTION 
       [0005]    In one example, there is provided a jet pipe arrangement for a servo valve, the jet pipe arrangement including a jet pipe, at least two receivers in operable communication with the jet pipe. The jet pip arrangement further includes an electromagnet in direct magnetic communication with the jet pipe such that, in use, the jet pipe is movable in response to changes in a magnetic field created by the electromagnet to distribute flow from the jet pipe asymmetrically between the at least two receivers. 
         [0006]    In another example, there is provided a servo valve. The servo valve includes the jet pipe arrangement discussed above and a spool located between a first chamber and a second chamber, wherein the spool is movable between the first chamber and the second chamber. The servo valve further includes a supply pressure inlet and a flexible tube connected to the supply pressure inlet and the first end of the jet pipe. The one or more receivers are fluidly connected to the first and second chambers, such that, in use, when the torque motor is activated, the spool can move position between the first and second chambers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows a known arrangement of a servo valve; and 
           [0008]      FIG. 2  shows an example of a new type of servo valve. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  shows generally a known arrangement of a hydraulic servo valve  10 . The hydraulic servo valve  10  shown in  FIG. 1  represents a jet pipe type arrangement as discussed above. The primary components of the jet pipe type arrangement are the jet tube  101  for receiving a supply pressure, an armature  102  connected to the jet pipe  101 , and an electromagnet  105  surrounding the armature  102 . In known arrangements, the jet pipe  101  and the armature  102  are separate components. An electrical input (not shown) is connected to the electromagnet  105 . When an electrical current is supplied to the electromagnet  105 , the armature  102  changes position due to electromagnetic forces supplied by the electromagnet  105 . The jet pipe arrangement shown in  FIG. 1  may be contained within a housing  106 . 
         [0010]    In the example shown, the armature  102  is connected in a perpendicular manner to the jet pipe  101 , or is an integral part of the jet pipe  101 —the integral part being perpendicular to the jet pipe  101 . The electromagnet  105  provides a torque that is proportional to the electrical current that is provided by the electrical input. The armature  102  may include coils (not shown) and the electromagnet  105  consists of a set of permanent magnets (not shown) surrounding the armature  102 . When a current is applied to the armature  102 , magnetic flux acting on the ends of the armature  102  is developed. The direction of the magnetic flux (force) depends on the sign (direction) of the current. The magnetic flux will cause the armature tips ( 102   a,    102   b ) to be attracted to the electromagnet  105  (current direction determines which magnetic pole is attracting and which one is repelling). This magnetic force creates an applied torque on the jet pipe  101 , which is proportional to applied current. The jet pipe  101  rotates and interacts with a spool portion (shown generally as  107  in  FIG. 1 ). 
         [0011]    The primary components of the spool portion  107  are receivers  108   a  and  108   b  that are in fluid communication with chambers  104   a  and  104   b.  There is also provided a spool  103  which is movable between chambers  104   a  and  104   b.  The movement of the spool  103  is accurately controlled by the jet pipe  101  and the pressure provided in chambers  104   a  and  104   b.    
         [0012]    The hydraulic servo valve  10  also includes a supply pressure inlet flexible tube  111  connected to a supply pressure inlet  109  that provides fluid into the flexible tube  111 . The fluid passes through a filter  112  and then through jet pipe  101 . At the end of the jet pipe  101  is a nozzle  113 . 
         [0013]    In use, the jet pipe  101  converts kinetic energy of moving fluid into static pressure. When the jet pipe  101  is centred between the receivers  108   a  and  108   b,  the pressure on the spool  103  is equal. However, when the jet pipe  101  is rotated by the armature  102  and electromagnet  105  toward one of the receivers—say  108   a,  the pressure at this receiver  108   a  is greater than the other receiver  108   b.  This creates a load of imbalance on the servo  103  causing the spool  103  to move. If, for example, the jet pipe  101  is rotated toward the receiver  108   a,  this could cause the spool  103  to move to the right and into chamber  104   b,  as the pressure would be greater in chamber  104   a,  and the pressure would be decreased in chamber  104   b.  As the spool  103  moves from a null position—i.e., when the pressure is equal in chambers  104   a  and  104   b — outlets  110   a  and  110   b  can control pressure in an actuator (not shown). The actuator part of the servoactuator has the same characteristics as any known hydraulic actuator. 
         [0014]    Whilst the type of arrangement shown in  FIG. 1  controls the position of the jet pipe  101  and the spool  103 , this arrangement is costly and complex due to the amount of components necessary for the servo valve  10 . What is needed therefore is a new type of servo valve that reduces the weight and size of known arrangements of servo valves, and to simplify the structure in order to reduce costs and complexity of the device. 
         [0015]      FIG. 2  shows a new type of hydraulic servo valve  20 . Here, the jet type arrangement includes a jet pipe  201  for receiving a supply pressure, and an electromagnet  205 . The jet pipe arrangement shown in  FIG. 2  may be contained within a housing  206 . The jet pipe  201  may have a first end  201   a  and a second end  201   b.  The electromagnet  205  is arranged to surround the jet pipe  201 . In the example shown in  FIG. 2 , the electromagnet  205  surrounds the second end  201   b.  However, it is to be understood that the electromagnet  205  may surround the first end  201   a  or any portion of the jet pipe  201  extending between the first end  201   a  and the second end  201   b.  The jet pipe  201 , of  FIG. 2 , has no armature. Therefore, the electromagnet  205  interacts with the jet pipe  201  only. The jet pipe  201  of  FIG. 2  may include a coating (not shown) with magnetic properties that interact with the electromagnet  205 . In one example, the coating of the jet pipe may be iron oxide nanoparticles. In another example, the jet pipe  201  of  FIG. 2  may include neodymium magnets (not shown) on an outer surface of the jet pipe  201  that interact with the electromagnet  205 . In a further example, the jet pipe  201  may include windings around the outer surface of the jet pipe  201  to interact with the electromagnet  205 . 
         [0016]    An electrical input (not shown) is applied to the electromagnet  205 . When an electrical current is supplied to the electromagnet  205 , the jet pipe  201  changes position due to electromagnetic forces supplied by the electromagnet  205 . The rotation of the jet pipe  201  is controlled by the electromagnetic forces supplied by the electromagnet  205 . In the example shown in  FIG. 2 , there is no armature—therefore, the electromagnet  205  directly causes the jet pipe  201  to rotate. Advantageously, this reduces the overall weight of a servo valve and reduces the number of parts in the servo valve, which reduces the overall complexity and cost of the servo valve. 
         [0017]    The electromagnet  205  provides a torque that is proportional to the electrical current that is provided by the electrical input. The jet pipe  201  may include a coating or windings, as discussed above, and the electromagnet  205  may consist of a set of permanent magnets surrounding the jet pipe  201 . When a current is applied to the jet pipe  201 , magnetic flux acting on the jet pipe  201  is developed. The direction of the magnetic flux (force) depends on the sign (direction) of the current. The magnetic flux will cause the jet pipe  201  to be attracted to the torque motor  205  (current direction determines which magnetic pole is attracting and which one is repelling). This magnetic force creates an applied torque on the jet pipe  201 , which is proportional to applied current. The jet pipe  201  rotates and interacts with a spool portion (shown generally as  207  in  FIG. 2 ). 
         [0018]    The spool portion  207  may include receivers  208   a  and  208   b  that are in fluid communication with chambers  204   a  and  204   b.  There is also provided a spool  203  which is movable between chambers  204   a  and  204   b.  The movement of the spool  203  is accurately controlled by the jet pipe  201  and the pressure provided in chambers  204   a  and  204   b.    
         [0019]    The hydraulic servo valve  20  may also include a supply pressure inlet flexible tube  211  connected to a supply pressure inlet  209  that may provide fluid into the flexible tube  211 . The fluid may pass through a filter  212  and then through jet pipe  201 . At the end of the jet pipe  201  may be a nozzle  213 . 
         [0020]    In use, the jet pipe  201  converts kinetic energy of moving fluid into static pressure. When the jet pipe  201  is positioned relative to the receivers  208   a  and  208   b  such that fluid flow through the jet pipe  201  is evenly divided between the receivers  208   a  and  208   b,  the pressure in the chambers  204   a  and  204   b  on opposing sides of the spool  203  is equal. However, when at least a portion of the jet pipe  201 , such as second end  201   b,  for example, of the whole of the jet pipe  201  is moved by the electromagnet  205  such that fluid flow through the jet pipe  201  is unevenly distributed between the receivers  208   a  and  208   b,  the pressure in the receiver that receives the greater flow causes a load of imbalance on the spool  203  by providing greater pressure to the chamber  204   a  or  204   b  that is fluidically connected to the receiver  208   a,    208   b  receiving the greater flow. This pressure difference causes the spool  203  to move. If, for example, the jet pipe  201  is rotated toward the receiver  208   a,  this could cause the spool  203  to move to the right and into chamber  204   b,  as the pressure would be greater in chamber  204   a,  and the pressure would be decreased in chamber  204   b.  As the spool  203  moves from a null position—i.e., when the pressure is equal in chambers  204   a  and  204   b— outlets  210   a  and  210   b  can control pressure in an actuator (not shown). The actuator part of the servoactuator has the same characteristics as any known hydraulic actuator. 
         [0021]    Although this disclosure has been described in terms of preferred examples, it should be understood that these examples are illustrative only and that the claims are not limited to those examples. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims.