Abstract:
A drain valve including a housing, a poppet, a seal, a follower pin, and a biasing mechanism. The housing defines a passage there-through from a first end to a second end, a cam surface at the second end with at least two detents therein, and at least one slot in the housing fluidly coupling the passage to exterior of the housing. The poppet is disposed within the passage. The seal is disposed between the housing and the poppet. The follower pin is coupled to the poppet near the poppet second end. The follower pin is configured to move along the cam surface and settle in at least one of the at least two detents. The spring is configured to bias the poppet away from the second end.

Description:
[0001]    The present application claims priority to U.S. Provisional Patent Application No. 60/469,076, filed May 7, 2003, which application is incorporated herein by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to a drain valve. In particular, the invention relates to a drain valve for aircraft fuel tanks that is simpler to operate, and, therefore, less prone to breakage.  
           [0004]    2. Description of Related Art  
           [0005]    Aircraft fuel tanks generally require drain valves located at the low points of the fuel tanks in order to remove water caused by condensation. These drain valves are also used to sample the fuel for contamination. Existing drain valves require the operator to perform a sequential, push-and-turn operation to open the valve. A different, sequential, push-and-turn operation is required to close the valve. If the operator wishes to change the valve seal by operating the valve to the “service” position, another, different, sequential, push-and-turn motion is required. Since valves that are made by different manufacturers are operated by means of different, sequential, push-and-turn operations, the operator must try to ascertain how a given valve is operated. If the information is not available, the operator is forced to experiment with various motions, and consequently, drain valve breakage occurs in some cases. An example of such a drain valve is disclosed in U.S. Pat. No. 4,880,029, which is incorporated by reference herein.  
           [0006]    Accordingly, a twist cam valve that addresses the drawbacks of the prior art would be highly desirable.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    According to the invention, there is provided a drain valve including a housing, a poppet, a seal, a follower pin, and a biasing mechanism. The housing defines a passage there-through from a first end to a second end. The housing also defines a cam surface at the second end with at least two detents therein. In addition, the housing defines at least one slot in the housing fluidly coupling the passage to exterior of the housing. The poppet is disposed within the passage. The seal is disposed between the housing and the poppet. The follower pin is coupled to the poppet. The follower pin is configured to move along the cam surface and settle in the at least two detents. The spring is configured to bias the poppet away from the second end. In use the poppet is configured to move along its longitudinal axis when rotated. The invention simplifies the operation of a drain valve to only a rotary actuation by an operator, instead of requiring the operator to use a sequential combination of axial pushing and rotary motion.  
           [0008]    The present invention provides a means of operation wherein the drain valve is operated from an “open” position, to a “closed” position, and to a “service” position by a simple, rotary, turning motion. No complicated or uniquely sequential motions are required to operate the drain valve. A stationary cam surface guides the internal portion of the valve axially to each position as the internal portion of the valve is turned. The invention provides for a detent in the cam at each distinct position, i.e., open, closed, and service, so that the valve is positively held in position when it reaches each of the three operating positions. The operator can feel, hear, and see when the valve reaches the desired position. Accordingly, attempting to operate the drain valve by pushing, turning, or a combination of both pushing and turning is not required, thereby avoiding damaging the drain valve. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    For a better understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 is a cross-sectional view of a drain valve according to an embodiment the present invention;  
         [0011]    [0011]FIG. 2 is an isometric view of the drain valve shown in FIG. 1;  
         [0012]    [0012]FIG. 3 is an isometric view of another drain valve according to another embodiment of the present invention;  
         [0013]    [0013]FIG. 4 is a cross-sectional view of another drain valve according to another embodiment the present invention; and  
         [0014]    [0014]FIG. 5 is a cross-sectional view of yet another drain valve according to yet another embodiment the present invention 
     
    
       [0015]    Like reference numerals refer to corresponding parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    [0016]FIG. 1 is a cross-sectional view of a drain valve  100  according to an embodiment the present invention. The drain valve  100  comprises a housing  102  having a first end  104  and a second end  106 . The housing  102  also defines a passage through the housing  102  that connects openings at the first and second ends of the housing. The passage preferably has a circular cross-section, i.e., the housing is formed by a cylindrical side wall extending from the first end to the second end.  
         [0017]    An annular insert  108  is coupled to the housing  102  within the opening at the first end of the housing. In a preferred embodiment, the insert  108  is coupled to the housing  102  by thermal welding.  
         [0018]    The housing also preferably includes a flange or lip  110  that extends substantially perpendicular to a longitudinal axis of the housing  102  at the fist end  104 . When installed, the housing extends into a fuel tank  112  such that the flange or lip  110  rests against the outside surface of the fuel tank. An annular seal  114  is preferably installed between the flange  110  and the exterior wall of the fuel tank  112  to prevent fluid from leaking from the fuel tank. Rivet or screw holes  116  may also be provided in the flange for fastening the flange  110  to the exterior wall of the fuel tank  112 .  
         [0019]    Further, the housing  102  preferably defines one or more slots  118  in the side wall thereof for fluid communication between the fuel tank  112  and the passage formed within the housing  102 . The housing  102  also preferably defines a cam surface  120  at the second end  106  of the housing  102 . The cam surface is described in further detail below in relation to FIG. 2. The housing  102  also preferably defines a chamber  126 . The chamber  126  has a diameter slightly larger than the passage. The chamber  126  is defined between the side wall of the housing and the poppet  122  (described below), and the insert  108  and a shelf  128 . The shelf  128  defines a step between the diameter of the chamber and the diameter of the passage.  
         [0020]    The drain valve  100  also preferably includes a poppet  122 . The poppet  122  is an upright member that rises perpendicularly to plug or unplug the opening at the first end of the housing. In a preferred embodiment, the poppet  122  is a solid cylindrical shaft having a first end, near the housing&#39;s first end, and a second end, near the housing&#39;s second end. The poppet  122  preferably has a diameter slightly smaller than the diameter of the passage defined by the housing. The poppet  122  is configured to both rotate within the passage formed by the housing  102 , as shown by arrow  124 , and move transversely within the passage in a direction parallel to the poppet&#39;s and housing&#39;s longitudinal axis.  
         [0021]    A follower pin  130  is preferably coupled to the poppet  103 , such that the follower pin travels along the cam surface  120  of the housing  102 , as described below in relation to FIG. 2. The follower pin  130  may be screwed into a hole in the poppet or attached by any other suitable means. A biasing mechanism  132 , such as a compression spring, is positioned within the chamber  126 . One end of the biasing mechanism  132  rests against the shelf  128  of the housing  102 , while the other end of the biasing mechanism  132  rests against a lip  134  that extents substantially perpendicularly from the poppet. The lip  134  preferably has a diameter slightly smaller than the diameter of the chamber  126 .  
         [0022]    A seal  136  is preferably disposed between the poppet and the insert  108  near the first ends of the poppet and the housing. In a preferred embodiment, the seal  136  is disposed within an annular groove formed in the poppet neat the poppet&#39;s first end. The annular groove is preferably substantially perpendicular to the longitudinal axis of the poppet and has a diameter slightly smaller than the poppet. In an alternative embodiment, a lubricant  138  may replace or supplement the seal  136  to prevent leakage through the closed drain valve.  
         [0023]    In another embodiment, the housing  102  may have a protruding lip (not shown) at the opening near the housing&#39;s first end to cause fluid emanating from the valve to drip free of the fuel tank surface.  
         [0024]    A rotation mechanism  140  formed at one end of the poppet  122  is provided to drive the rotate the poppet, as indicated by arrow  124 . In one embodiment the rotation mechanism  140  is a depression or slot, such as a hexagonal depression or a depression for receiving a regular or PHILLIPS screwdriver head, into which a tool can be inserted to turn the poppet  122 . The poppet  122 , housing  102 , and insert  108  are preferably made from a metallic material, although any other suitable material may be used.  
         [0025]    [0025]FIG. 2 is an isometric view of the drain valve  100  shown in FIG. 1. In a “closed” position, the poppet  122  is located as shown in FIG. 1, with the seal  136  (FIG. 1) engaged with insert  108  (FIG. 1), thereby preventing fluid flow through the drain valve. In this “closed” position, the follower pin  130  settles in a closed notch or detent  202  in the cam surface  120  formed in the housing  102  at the second end  106  of the housing  102 . In this position, the follower pin  130  is held in place by the biasing mechanism  132  acting between the poppet  122  and an internal shelf  128  in the housing.  
         [0026]    When the poppet  122  is rotated to an “open” position, the follower pin  130  leaves the “closed” notch, slides along the cam surface  120 , and is raised by the cam to the open notch or detent  204 , thereby displacing the poppet  122  axially inward away from the insert  108  (FIG. 1) and causing the poppet seal  136  (FIG. 1) to become disengaged from the insert  108  (FIG. 1). To do this, an operator must not only turn the poppet  122 , but also apply a force in the longitudinal axis direction from the first end  104  toward the second end  106 , against the force of the biasing mechanism  132 . This change in axial position creates an open path for the fluid to pass from the fuel tank  112  (FIG. 1) through the slot(s)  118  in the housing  102  (FIG. 1) to the exterior of the fuel tank  112  (FIG. 1). In other words, fluid communication is facilitated from the fuel tank, through the passage in the housing, and out of the opening in the housing at the housing&#39;s first end  104 .  
         [0027]    In the “open” position, the follower pin  130  engages the open notch or detent  204  in the cam surface  120 , and is held in the open notch by the biasing mechanism  132  acting between the poppet  122  and the internal shelf  128  of the housing  102 .  
         [0028]    When the poppet  122  is rotated further in the same direction, the follower pin  130  disengages from the open notch  204  and slides along the cam surface  120  until the pin reaches a “service” notch or detent  206 . In this position, the follower pin  130  is at the lowest portion of the cam surface  120 , and is held in that position by the biasing mechanism  132  acting on the poppet  122 . In this position, the seal  136  extends outward away from the second end  106  of the housing  102 , thereby being accessible for replacement, i.e., the seal  136  extends outward from the tank  112  (FIG. 1). In this service position, the lip or shoulder  134  (FIG. 1) of the poppet  122  contacts the insert  108  to form a seal, thereby blocking fluid flow from the tank out of the fuel tank while the seal  136  is being serviced or replaced.  
         [0029]    When the poppet  122  is rotated further in the same direction, the follower pin  130  leaves the service notch or detent  206  and rides up the cam surface  120  until the pin again reaches the “closed” position. The follower pin  130  then again enters the closed notch or detent  202  in the cam surface  120 , and is held there by the biasing mechanism  132  acting between the poppet  122  and the housing  102 . In the “closed” position, the poppet seal  136  engages the insert  108  and prevents fluid flow through the drain valve  100 .  
         [0030]    The rotation direction of the poppet is preferably optional. The poppet  122  can be rotated in the either direction to cause the poppet  122  to move from one position to the next position. In another embodiment, the rotation is restricted to one direction by a ratchet mechanism (not shown). However, such an mechanism may cause damage if an operator tries to force the poppet against the ratchet.  
         [0031]    [0031]FIG. 3 is an isometric view of another drain valve  300  according to another embodiment of the present invention. This view includes a nut  306  that is used to fasten the drain valve to the fuel tank in some installations. Here, the nut  306  is placed inside the fuel tank and threads  308  on the drain valve  100  are threaded into the nut  306  to secure the drain valve through a wall of the fuel tank.  
         [0032]    [0032]FIG. 4 is a cross-sectional side view of another drain valve  400 . In this embodiment, the slots  118  (FIG. 1) in the housing are eliminated. Rather, the poppet defines a passage  404  there-through. The poppet also defines an outlet  408  fluidly coupled to the passage  404 . In use, when the valve is in the “open” position, fluid flows from the tank through the passage  404 , out of the outlet  408 , and out through the opening at the housing&#39;s first end. In the service position, a seal is formed between the poppet and the insert to close the outlet  408 .  
         [0033]    [0033]FIG. 5 is a cross-sectional side view of yet another drain valve  500 . Here, the cam surface  504  is enclosed within a portion of the housing. This prevents the follower pin  502  from accidentally unseating and moving to a different position. Alternatively, an overhang or guide may be provided above the closed position detent to prevent the follower pin from unseating and opening the valve. This embodiment may be required where an aircraft using the drain valve of the invention operates in a Lightning Zone 1 area, where lightning may unseat the follower pin and open the valve.  
         [0034]    The foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. For example, any methods described herein are merely examples intended to illustrate one way of performing the invention. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously many modifications and variations are possible in view of the above teachings. For example, the drain valve may be used in any fluid vessel, not just in fuel tanks. Also, any figures described herein are not drawn to scale. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.