Abstract:
A cooling structure for a servo valve includes a shroud to enclose at least a portion of the servo valve; and a base connected to the shroud to define a cooling chamber surrounding the servo valve, the base including an inlet port to receive cooling air, a flow channel connecting to the inlet port and a plurality of flow passages connecting the flow channel to the cooling chamber to allow cooling air flow from the inlet port into the cooling chamber.

Description:
BACKGROUND 
       [0001]    This invention relates generally to valves, and specifically to servo valves. 
         [0002]    Gas turbine engines typically include bleed systems for bleeding off air from the engine. This air is typically very hot, 500 degrees F. (260 degrees C., 533.15 K) or more, so components of the system must be able to withstand these temperatures. Valves in bleed system typically include a servo valve that can include electronics sensitive to the high temperatures. Because of this, the servo valve is sometimes remotely mounted away from the valve and high temperatures. 
       SUMMARY 
       [0003]    A cooling structure for a servo valve includes a shroud to enclose at least a portion of the servo valve; and a base connected to the shroud to define a cooling chamber surrounding the servo valve, the base including an inlet port to receive cooling air, a flow channel connecting to the inlet port and a plurality of flow passages connecting the flow channel to the cooling chamber to allow cooling air flow from the inlet port into the cooling chamber. 
         [0004]    A method of cooling a portion of a servo valve with electrical components includes providing a servo valve with a portion with electrical components; providing a cooling structure with a shroud with a vent port and a base, the base with an inlet port to receive cooling air, a flow channel connecting to the inlet port and a plurality of flow passages connecting the flow channel to the shroud to allow cooling air flow into the shroud; connecting the base to the portion of the servo valve with electrical components; and connecting the shroud to the base to form a cooling air cavity around the portion of the servo valve with electrical components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a perspective view of a servo valve. 
           [0006]      FIG. 2A  shows a perspective view of a cooling structure for a portion of the servo valve of  FIG. 1 . 
           [0007]      FIG. 2B  shows a bottom view of the cooling structure of  FIG. 2A . 
           [0008]      FIG. 2C  shows a cross-sectional view of the cooling structure of  FIG. 2A . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  shows a perspective view of valve  10  with valve body  12 , valve passage  14 , valve disk  16 , actuator  18 , servo valve  20  and cooling structure  22  with shroud  24  (with vent port  25 ) and base  26  (with bolts  28 , inlet port  30  and electrical connector  32 ). Valve  10  can be part of a bleed system on a gas turbine engine. 
         [0010]    Valve disk  16  sits in valve passage  14  and connects to actuator  18 . Actuator  18  is connected to and controlled by servo valve  20 . Servo valve  20  includes base  26 , which forms a part of cooling structure  22 . Cooling structure  22  can be integral to servo valve  20 . Actuator can include pressure ports (see  FIG. 2B ), one or more pistons and a linkage system (not shown) to connect to valve disk  16 . Servo valve  20  receives electronic signals from a controller (not shown) through wires connected to electrical connector  32  to control air in pressure ports. The pressure in pressure ports causes actuator to open or close valve  10  by rotating valve disk  16 , opening or closing valve  10 . 
         [0011]    Cooling structure  22  includes shroud  24  which connects to base  26  and encloses servo valve  20  to form a cooling chamber around servo valve  20 . Cooling structure  22  can be bolted to valve body  12  with bolts  28 . Inlet port  30  on base  26  receives a cooling airflow. In a bleed system on a gas turbine engine, this cooling flow can come from the fan and can be delivered by a thermal line (not shown). 
         [0012]    Air in the pressure ports typically comes from valve passage  14 , and when valve passage  14  is part of a bleed system, this air can be very hot, for example, 1200 degrees F. (649 degrees C., 922.15 K). The electrical components of servo valve  20  typically are not built to handle such high temperatures and may be susceptible to melting or servo valve failure if exposed. Past systems have prevented failure of electrical components in the servo valve by locating the servo valve away from the valve body and connecting it to the actuator with different linkage lines and components. In some past systems, the electrical components were bolted to a fan casing, which was six feet or more away from the valve. This resulted in additional components for the valve, increasing the weight and space which the valve needed. A second method of avoiding the melting and failure of electrical components was to direct a cooling flow at the electrical components. This proved to be an inefficient and oftentimes ineffective way of cooling. 
         [0013]    Cooling structure  22  provides for effective and efficient cooling of electrical components of servo valve without the need for much increased space and weight of past cooling systems. Cooling structure  22  receives cooling air through inlet port  30 , circulates the cooling air close to servo valve  20  by forming a cooling chamber with base  26  and shroud  24 , and then vents that cooling air out vent port  25  to keep a continuous flow. 
         [0014]      FIG. 2A  shows a perspective view of cooling structure  22  for a portion of the valve  10 ,  FIG. 2B  shows a bottom view of cooling structure  22 , and  FIG. 2C  shows a cross-sectional view of cooling structure  22  of  FIG. 2A . Cooling structure  22  includes shroud  24  with vent port  25  and base  26  with inlet port  30 , electrical connector  32 , flow channel  34 , flow passages  36 , holes  38  for bolts  28 , control pressure port  40 , supply pressure port  42  and ambient vent for servo valve  43 . Servo valve  20  inner workings are not shown, and only the outer housing is illustrated in  FIGS. 2A-2C . 
         [0015]    Cooling structure  22  can be made of aluminum, steel or other materials that can withstand high temperatures and contain cooling air flow. Shroud  24  can be flat on a top portion with a cylindrical side wall connecting to base  26  to form a sealed cavity or chamber around servo valve  20 . The connection can include screwing shroud  24  onto base  26 , bolting or any other method of connection that can withstand the temperatures in the particular system. Shroud  24  forms a cavity or chamber around servo valve  20  to contain a cooling air flow around servo valve  20 . Cooling air enters inlet port  30 , flows around cooling channel  34  and through flow passages  36 . In the embodiment shown, base  26  includes four flow passages  36 , but other embodiments can include more or less flow passages depending on cooling requirements. Base  26  also includes ports  40 ,  42 ,  43  for directing flow to actuator  18 . Flow channel  34  is in an arcuate shape to channel cooling airflow to all flow passages and to cool the bottom of servo valve  20  (as in this embodiment, servo valve  20  is contained in a cylindrical housing). Flow passages  36  then deliver cooling airflow to shroud  24  to cool electrical components of servo valve  20 . The cooling air in shroud  24  is vented through vent port  25  so that airflow stays continuous for adequate cooling of servo valve  20 . 
         [0016]    As discussed above, servo valve  20  controls valve  10  by regulating high temperature air delivered through supply port  42 . Servo valve  20  meters this air in response to an electrical command and modulates the control pressure sent out through control port  40 . The pressure in control port  40  triggers actuator to open or close valve disk by moving the pistons and/or linkage system to cause rotation of valve disk  16 . The air going through control port  40  and supply port  42  is typically taken from valve passage  14 . When valve is part of a gas turbine engine, and particularly part of a bleed system, the air is very hot, up to 1200 degrees F. (649 degrees C., 922.15). The electronic components in servo valve  20  are not able to withstand temperatures that hot, and are susceptible to melting, overheating and failure if exposed to the hot bleed air. 
         [0017]    Cooling structure  22  acts to protect servo valve  20  from exposure to high temperatures, protecting electrical components without adding significant weight or additional components and without requiring extra space for valve  10 . By containing servo valve  20  with shroud  24  and base  26  to form a small cavity around servo valve  20 , cooling structure  22  can provide the cooling needed to protect electrical parts efficiently. This allows the placement of electrical components directly on or near valve  10 , avoiding the extra space needed in past systems that located the electrical components away from valve  10  due to the high temperatures. This also provides for more efficient cooling than some past systems by containing the cooling airflow in a small area (in flow channel  34 , flow passages  36  and within shroud  24 ), only where it is needed to provide cooling directly to only the parts needing it (electrical components). 
         [0018]    While the cooling structure  22  has been described in relation to having an arcuate cooling channel  34  with four flow passages  36  into shroud  24 , the cooling channel  34  and flow passages  36  can be shaped and/or sized differently according to cooling needs. Additionally, the system can have more or fewer cooling passages. While cooling structure  22  has been described in relation to cooling electrical components of a bleed valve, it could be used for cooling any components necessary in other valves used in other systems. Cooling structure  22  could also have different shapes and/or sizes depending on cooling needs of the valve. 
         [0019]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.