Abstract:
A valve comprises a valve body including an inlet through which fluid flows into the valve, a main valve including a main poppet positioned in the valve body and including a chamber therein, wherein the fluid flows into the chamber, a pilot valve including a pilot poppet positioned within the main valve and including a discharge port through which the fluid flows out of the chamber, a main poppet spring biased to force the main poppet closed in the absence of flow of the fluid into the valve, a pilot poppet spring biased to keep the discharge port open, and a plurality of bi-metal disks located within the chamber. The plurality of bi-metal disks curl at a predetermined temperature of the fluid to compress the pilot poppet spring and close the discharge port. As a result, the fluid is prevented from flowing out of the chamber and fluid pressure between the chamber and the inlet is equalized to close the main poppet.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a temperature control valve, and more specifically, to a temperature control valve that shuts off fluid flow at a specific temperature. 
         [0003]    2. Discussion of the Related Art 
         [0004]    Within the industrial and transportation fields, there exists a need to shut off fluid flow, for example, from a pump or from a venting system, if the fluid temperature becomes too hot. Such a controlling function is necessary in order to prevent damage to components, including those generating or receiving the fluid flow. The fluid in such cases may be, for example, oil or steam. 
         [0005]    An example of a device or system where fluid flow must be controlled is the gear case venting lines in large aircraft engines. Under most conditions, it is desirable to have a circulation of compressor bypass air through the case to prevent condensation, remove generated heat, and maintain proper gear geometry by maintaining a relatively constant gear case temperature. Should circulating air become too hot, such as if an internal seal starts to have excessive leakage, discharge from higher pressure compressor stages and even combustor heat can be drawn into the flow. Excessive heat can destroy the lubricant protecting the gears and generate coking. This flow must be shut off before such excessive temperature enters the gear case. 
         [0006]    Accordingly, there is a need for a temperature control valve that shuts off fluid flow at a specific temperature, regardless of altitude, operating pressure, or pressure drop. 
       SUMMARY OF THE INVENTION 
       [0007]    Embodiments of the present invention provide a pilot operated temperature control valve that employs bi-metal disks to throttle flow through a control port to open and close the valve, based on temperature. 
         [0008]    A valve, in accordance with an embodiment of the present invention, comprises a valve body including an inlet through which fluid flows into the valve, a main valve including a main poppet positioned in the valve body and including a chamber therein, wherein the fluid flows into the chamber, a pilot valve including a pilot poppet positioned within the main valve and including a discharge port through which the fluid flows out of the chamber, a main poppet spring biased to force the main poppet closed in the absence of flow of the fluid into the valve, a pilot poppet spring biased to keep the discharge port open, and a plurality of bi-metal disks located within the chamber. The plurality of bi-metal disks curl at a predetermined temperature of the fluid to compress the pilot poppet spring and close the discharge port. As a result, the fluid is prevented from flowing out of the chamber and fluid pressure between the chamber and the inlet is equalized to close the main poppet. 
         [0009]    The valve may further comprise a disk seat attached to the pilot poppet and positioned at an end of the bi-metal disks, wherein an increase in an end-to-end length of the bi-metal disks exerts a force on the disk seat, and a force on the pilot poppet spring. The disk seat may enclose a plurality of connector pins connecting the pilot poppet to the disk seat. There may be at least eight bi-metal disks, and a diameter of the main poppet may be larger than a diameter of the inlet. 
         [0010]    The valve may further comprise a groove formed in the pilot poppet, a pin positioned in the groove, a cam ring holding the pin in the groove, and a detent spring exerting a force on the cam ring, wherein the pin holds the pilot poppet to keep the discharge port open until a force from the bi-metal disks overcomes the force of the detent spring. 
         [0011]    A method for closing a valve based on a temperature change of fluid flowing through the valve, in accordance with an embodiment of the present invention, comprises biasing a main poppet closed with a main poppet spring in the absence of flow of the fluid into the valve, flowing the fluid into the valve through an inlet, and into a chamber positioned in the main poppet, flowing the fluid out of the chamber through a pilot valve discharge port, biasing the discharge port open with a pilot poppet spring, curling a plurality of bi-metal disks located within the chamber at a predetermined temperature of the fluid to compress the pilot poppet spring and close the discharge port to prevent the fluid from flowing out of the chamber, and equalizing fluid pressure between the chamber and the inlet to close the main poppet. 
         [0012]    The method may further comprise attaching a disk seat to the pilot poppet and positioning the disk seat at an end of the bi-metal disks, and increasing an end-to-end length of the bi-metal disks to exert a force on the disk seat, and a force on the pilot poppet spring. 
         [0013]    The method may further comprise positioning a pin in a groove formed in the pilot poppet, holding the pin in the groove, wherein the pin is held in the groove by a cam ring, and exerting a force on the cam ring, wherein the pin holds the pilot poppet to keep the discharge port open until a force from the bi-metal disks overcomes the exerted force on the cam ring. A detent spring can be used to exert the force on the cam ring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Exemplary embodiments of the present invention will be described below in more detail, with reference to the accompanying drawings, of which: 
           [0015]      FIG. 1  is a perspective view of a temperature control valve, according to an embodiment of the present invention; 
           [0016]      FIG. 2  is a front view of a temperature control valve, according to an embodiment of the present invention; 
           [0017]      FIG. 3  is a left side view of a temperature control valve, according to an embodiment of the present invention; 
           [0018]      FIG. 4  is a right side view of a temperature control valve, according to an embodiment of the present invention; 
           [0019]      FIG. 5  is a sectional view of a temperature control valve when fluid temperature is below a set point, according to an embodiment of the present invention; 
           [0020]      FIG. 6  is a perspective sectional view of a temperature control valve when fluid temperature is below a set point, according to an embodiment of the present invention; 
           [0021]      FIG. 7  is a sectional view of a temperature control valve when fluid temperature is above a set point, according to an embodiment of the present invention; 
           [0022]      FIG. 8  is a perspective sectional view of a temperature control valve when fluid temperature is above a set point, according to an embodiment of the present invention; 
           [0023]      FIG. 9  is a sectional view of a temperature control valve including a detent mechanism, according to an embodiment of the present invention; and 
           [0024]      FIG. 10  is a perspective sectional view of a temperature control valve including a detent mechanism, according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0025]    Exemplary embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 
         [0026]    Referring to the figures, a temperature control valve  10  includes a main valve body  11  housing a main poppet  13 . Fluid, for example, oil or gas, enters the valve body  11  through valve inlet  12 . 
         [0027]      FIGS. 5 and 6  show the operation of the valve  10  when the fluid temperature is below an allowed/set point. The valve  10  employs a main poppet  13  that is larger in diameter than the main valve seat  14 . The seat diameter is the same as the diameter of the inlet port  12 . A light spring  15  holds the main poppet  13  against the seat  14  in the absence of inlet flow. A small portion of the incoming fluid is leaked into a chamber  16  in the interior of the main poppet  13 . This chamber will be referred to as the control chamber  16 . Pressure in the control chamber  16  acts on the full diameter of the main poppet  13 . 
         [0028]    A pilot valve is positioned within the main valve and includes a pilot poppet/valve sleeve  23 . Fluid enters the pilot valve through a pilot valve inlet orifice  22 . As shown in  FIGS. 5 and 6 , when the pilot valve is open, the pilot poppet spring  25  keeps the pilot poppet/valve sleeve  23  positioned to the left in  FIG. 5 , thereby keeping the pilot valve port  27  open. As a result, fluid from the control chamber  16  may vent through the pilot valve port  27  to discharge conduit  28 . 
         [0029]    When fluid is discharged from the control chamber  16  through the open pilot valve, fluid pressure within the control chamber  16  remains less than fluid pressure at the valve inlet  12 . As long as the fluid pressure on the inside of the main poppet  13  is enough lower than the incoming fluid pressure from inlet  12 , the valve will allow incoming fluid to overcome the main poppet spring  15  and force the main poppet  13  open, compressing the main poppet spring  15 , which then allows fluid to flow through the valve. Accordingly, the main poppet  13  is maintained in the open position. 
         [0030]    Referring to  FIGS. 7 and 8 , when the fluid temperature rises to above an allowed/set point, a curl of bi-metal disks  30  increases so that the end-to-end length of the plurality of bi-metal disks  30  increases. For example, the end-to-end length of the bi-metal disks  30  when the fluid temperature is below a set point may be about 0.060 inches, and, when the fluid temperature is above a set point, the end-to-end length of the bi-metal disks  30  may be about 0.064 inches. The increase in the end-to-end length of the bi-metal disks  30  drives a disk seat  24  to the right in  FIG. 7  to compress pilot poppet spring  25 . As a result, the pilot valve port  27  is closed, so that fluid from the control chamber  16  no longer vents through port  27  to valve discharge  28 . 
         [0031]    When fluid no longer drains from the control chamber  16 , since the piston area of the controlling portion of the main poppet  13  is larger than that of the seat  14 , the fluid pressure in the control chamber  16  increases to the fluid pressure at the inlet  12 , so that poppet  13  moves to the left in  FIG. 7  to close the main valve and prevent further fluid flow. 
         [0032]    Accordingly, as long as the fluid leaked into the control chamber  16  passes through and drains into the valve discharge  28 , the main poppet  13  will be pushed open, compressing the poppet spring  15 , and allowing flow through the valve. If the draining of the control chamber  16  is blocked, pressure in the control chamber  16  will increase to inlet pressure. Since the control chamber pressure works against the full poppet diameter, and that diameter is larger than the inlet port  12 , the main poppet  13  closes, shutting off flow. 
         [0033]    Bi-metal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bimetallic objects consist of layers of different metals. Bi-metallic strips and disks convert a temperature change into mechanical displacement. According to an embodiment of the present invention, the layers include, but are not limited to, for example, iron-nickel-chrome alloy against Invar or copper against stainless steel, and are responsive to temperature ranges including, for example, −200° F. to +600° F. The number of bi-metal disks  30  may be, for example, eight (8), to over 40. 
         [0034]    Referring to  FIGS. 5-6 , when the temperature is below the set temperature of the valve, the pilot poppet/sleeve spring  25  keeps the pilot poppet/sleeve to the left, lightly compressing, via a plurality of (e.g., 3) connector pins  29  and the disk seat  24 , a stack of partially curled bimetallic disks  30 . This allows control chamber fluid to drain, keeping the pressure in that chamber  16  close to the (lower) pressure on the discharge side of the valve. The disk seat  24  surrounds the plurality of connector pins  29 , which are attached to the pilot valve sleeve/poppet  23  to connect the pilot valve sleeve/poppet  23  to the disk seat  24 . 
         [0035]    Referring to  FIGS. 7 and 8 , as the fluid temperature increases to above an allowed/set point, the bi-metal disks curl more to increase their end-to-end length. As a result, the pilot poppet/sleeve  23  is forced to move to the right in  FIG. 7  via the disk seat  24  and the three connector pins  29 . This compresses the pilot sleeve spring  25  and closes the pilot valve port  27 . This shuts off the flow draining the control chamber  16 . As a result, control chamber pressure raises to that of the inlet port  12 . Since the piston area of the control chamber portion of the main poppet  13  is larger than the main poppet seat  14 , force from control chamber pressure and the main poppet spring  15  closes the main poppet  13  and prevents fluid flow. 
         [0036]    The pilot valve includes a pilot valve adjuster  26  which can be turned with, for example, a hexagonal shaped wrench, to adjust the compression force of the pilot poppet spring  25 . As a result, the required temperature to compress the spring  25  and close the pilot port  27  can be made higher or lower. 
         [0037]    According to an embodiment of the present invention, once the fluid temperature cools and returns to below an allowed/set point, the curl of the bi-metal disks  30  decreases, thereby decreasing the end-to-end length of the disks  30  so that the pilot poppet/sleeve spring  25  is no longer compressed. As a result, the spring  25  is once again able to push the pilot poppet/sleeve  23  to the left, lightly compressing, via the plurality of (e.g., 3) connector pins  29  and the disk seat  24 , the stack of partially curled bimetallic disks  30 . As a result, the pilot valve port  27  is opened and the fluid in the control chamber  16  is again allowed to drain, thereby keeping the pressure in that chamber  16  close to the lower pressure on the discharge side of the valve so that the main poppet  13  can open. 
         [0038]    According to alternative embodiments, the action of the pilot valve can be restrained so as not to allow the valve to respond to a change in temperature until a specific temperature different from that causing a response by the bi-metal disks alone is reached. At which point, the valve can snap to the open or closed position. For example, one or more detents having the same or different designs can be used to keep the valve open or closed after the valve has responded to a temperature change. For example, such restraints may be required for safety to avoid a situation where a brief temperature excursion occurs, causing damage the valve system, and then the valve resets itself without any record of the event. With one type of detent or latch design, the valve needs to be manually reset so as not miss any potential damage to the system. 
         [0039]    Referring to  FIGS. 9 and 10 , a detent pin  41  engages a groove  44  formed in the pilot valve poppet  23 , holding the poppet/sleeve  23  back to keep the pilot valve port  27  open until force from the bi-metal disks  30  overcomes the restraining force of the detent spring  45 . The detent spring  45  may be formed as a curved disk, which pushes on cam ring  42 , thereby holding the detent pin  41  in the groove  44 . There may be one or more detent pins  41 . For example, according to an embodiment of the present invention, three (3) detent pins  41  are positioned in the groove  44 . The detent pins  41 , which are held in place by the cam ring  42 , continue to hold the pilot valve open. The cam ring  42  holds the detent pins  41  in the groove  44  until force from the bi-metal disks  30  overcomes the force of spring  45 . 
         [0040]    Depending on factors, such as the strength of the spring  45 , where and how the groove  44  is positioned on the poppet  23 , the depth of the groove  44 , and the angle of the groove&#39;s sides, the valve can be held open, closed or biased to open or close later than if operating with the bimetallic disks  30  working alone. 
         [0041]    For example, the angle of the cam ring  42  and/or the shape/depth of the groove can be changed such that the force from the bi-metal disks  30  cannot be overcome. According to an embodiment, an outside collar can connect to the cam ring  42 . As a result, the cam ring  42  can then be pulled back, compressing the detent spring  45  and allowing the detent pins  41  to be pushed out of the groove  44 . 
         [0042]    In an embodiment, a detent mechanism may be employed, for example, between the disk seat  24  and the pilot valve body, to keep the pilot port  27  closed until a specific lower temperature is reached, at which point, the pilot sleeve spring  25  will overcome the detent force and move the pilot poppet/sleeve  23  to the left to open the pilot port  27 . 
         [0043]    As an alternative to the detent mechanism, a mechanical latch may be employed to lock the pilot valve closed until it is manually or remotely (via, for example, a solenoid or piston) reset. 
         [0044]    Although exemplary embodiments of the present invention have been described hereinabove, it should be understood that the present invention is not limited to these embodiments, but may be modified by those skilled in the art without departing from the spirit and scope of the present invention, as defined in the appended claims.