Abstract:
A sealed enclosure is provided. The enclosure includes a membrane vent adapted to mount through a wall of the enclosure, the membrane vent comprising an air permeable tubular membrane, a tubular structural support, wherein the tubular membrane is stretched over the tubular structural support, an air vent fitting attached to the tubular membrane at a first end, and an end cap attached to the tubular membrane at a second end.

Description:
TECHNICAL FIELD 
     The present invention relates to ventilation of enclosures. 
     BACKGROUND 
     Membrane vents are used, for example, in the automotive and telecommunications industries to equalize pressure between the interior and exterior of otherwise sealed enclosures. In membrane vents, membranes generally comprise porous air-transmitting material that is preferably impermeable to liquids. Membrane vents are therefore able to equalize pressure, while minimizing contamination of enclosure interiors. 
     The effectiveness of a membrane vent at pressure equalization is dependant upon both the material composition of the membrane, and upon the membrane&#39;s surface area. In the prior art, a membrane is approximately flat and arranged perpendicular to a small bore in the enclosure wall so as to completely cover the bore. This provides for a membrane surface area equal to or only slightly larger than the cross section of the bore, limiting the rate of pressure equalization. During periods of moderate to high changes in interior or exterior pressure, such limited rates of pressure equalization proves detrimental. 
     SUMMARY 
     A membrane vent is provided. The vent includes an air permeable tubular membrane, a tubular structural support adapted to be received by the tubular membrane, an air vent fitting attached to the tubular membrane at a first end and an end cap attached to the tubular membrane at a second end. 
     A sealed enclosure is provided. The enclosure includes a membrane vent adapted to mount through a wall of the enclosure, the membrane vent comprising an air permeable tubular membrane, a tubular structural support, wherein the tubular membrane is stretched over the tubular structural support, an air vent fitting attached to the tubular membrane at a first end and an end cap attached to the tubular membrane at a second end. 
    
    
     
       DRAWINGS 
         FIG. 1   a  depicts a perspective view of a tubular membrane vent prior to assembly in accordance with one embodiment of the present invention. 
         FIG. 1   b  illustrates a perspective view of the tubular membrane vent of  FIG. 1A  after assembly in accordance with one embodiment of the present invention. 
         FIG. 2   a  shows a side view of a threaded air vent fitting of the tubular membrane vent in accordance with one embodiment of the present invention. 
         FIG. 2   b  shows a cross sectional side view of the threaded air vent fitting of  FIG. 2A  in accordance with one embodiment of the present invention. 
         FIG. 2   c  illustrates a cut away of the threaded air vent fitting of  FIG. 2A  along the radial axis in accordance with one embodiment of the present invention. 
         FIG. 2   d  illustrates a cross sectional view of  FIG. 2C  in accordance with one embodiment of the present invention. 
         FIG. 3   a  illustrates a perspective view of a plug air vent fitting in accordance with one embodiment of the present invention. 
         FIG. 3   b  illustrates a representation of a plug air vent fitting in accordance with one embodiment of the present invention. 
         FIG. 3   c  illustrates a side view representation of a plug air vent fitting in accordance with one embodiment of the present invention. 
         FIG. 4   a  illustrates a perspective view of a vent cap of the tubular membrane vent in accordance with one embodiment of the present invention. 
         FIG. 4   b  illustrates a side view of a vent cap of the tubular membrane vent in accordance with one embodiment of the present invention. 
         FIG. 5   a  illustrates a tubular membrane in accordance with one embodiment of the present invention. 
         FIG. 5   b  illustrates a tubular membrane in accordance with one embodiment of the present invention. 
         FIG. 5   c  illustrates a tubular membrane in accordance with one embodiment of the present invention. 
         FIG. 5   d  illustrates a tubular membrane in accordance with one embodiment of the present invention. 
         FIG. 6   a  illustrates a perspective view of a tubular membrane vent in accordance with one embodiment of the present invention. 
         FIG. 6   b  illustrates a side view representation of a tubular membrane vent in accordance with one embodiment of the present invention. 
         FIG. 6   c  illustrates a side view representation of a tubular membrane vent in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. 
       FIG. 1A  illustrates a perspective view of a tubular membrane vent prior to assembly, shown generally at  99 , in accordance with one embodiment of the present invention. The tubular membrane vent comprises an air vent fitting  117 , a tubular membrane  121 , a tubular structural support  125 , and a vent cap  129 .  FIG. 1B  shows the tubular membrane vent  99  of  FIG. 1A  after assembly, shown generally at  100 . As illustrated, the tubular structural support  125  is inserted inside the tubular membrane  121  to provide strength and maintain the shape of the tubular membrane  121 . The air vent fitting  117  is affixed to one end of the tubular membrane  121 , and the vent cap  129  is affixed to the opposite end. In one embodiment, the connections between the air vent fitting  117  and the tubular membrane  121  and the vent cap  129  and the tubular membrane  121  are air tight connections. This permits air and pressure transfer only through the tubular membrane  121 , preventing leakage at the interconnects. 
     In the illustrated embodiment, the tubular membrane  121  comprises a cylinder having a diameter approximate to the diameter of the bore, and a length. In one embodiment, the tubular membrane  121  has a length of between 3 and 10 inches and a diameter between ⅛ and 1 inch. In alternative embodiments, the tubular membrane  121  comprises cylinders larger in diameter than the enclosure opening and diameters smaller than the enclosure opening. In still further embodiments, the tubular membrane  121  comprises alternative shapes, such as a tubular membrane  121  having a flared end or a bulbous tubular membrane  121 . 
     In one embodiment, tubular membrane  121  comprises an air permeable hydrophobic material. In an alternative embodiment, tubular membrane  121  comprises air permeable material that is both hydrophobic and oleophobic. In certain embodiments, tubular membrane  121  comprises a polytetrafluoroethylene (PTFE) membrane. In one embodiment, tubular membrane  121  comprises TETRATEX Performance Fabrics by Donaldson Corporation. 
     In the illustrated embodiment of  FIG. 1A , tubular structural support  125  comprises a metal coil spring. In one embodiment, the metal coil spring is coated with a non-conductive material. In alternative embodiments, nonmetal coil springs are used, such as springs comprising various plastics, elastomer, nylon, or the like. In still other alternative embodiments, non-spring structural supports  125  are implemented. 
       FIG. 2A  depicts a side view representation (along the longitudinal axis) of a threaded air vent fitting, shown generally at  117 , of the tubular membrane vent  100  in accordance with one embodiment of the present invention. In the illustrated embodiment, the air vent fitting  117  has an upper tip  122  and a lower tip  225  disposed at opposite ends along the longitudinal axis.  FIG. 2B  shows a cross sectional side view representation of  FIG. 2A , cut along line A-A′  205  (illustrated in  FIG. 2C ).  FIG. 2C  shows the threaded air vent fitting of  FIG. 2A  along the radial axis, looking up from the lower tip  225 .  FIG. 2D  shows a cross sectional view of  FIG. 2C , cut along line B-B′  206  (illustrated in  FIG. 2A ). The threaded air vent fitting  117  has a body comprising, for example, an acetal resin engineering plastic such as DELRIN, a polytetrafluoroethylene (“PTFE”) such as TEFLON, polypropylene, stainless steel, nylon, or other corrosion resistant material. The lower tip  225  comprises a hexagonal end  227  situated such that torque can be applied, such as by a wrench, along the radial axis. In alternative embodiments, other torque enabling configurations may be used, such as shapes designed to accept the application of rotational force by means of, for example, screw drivers, allen wrenches, and the like. 
     A plurality of vents  230  are separated from the lower tip  225  by a radial flared region  232  and disposed perpendicular to the longitudinal axis. In certain embodiments, the radial flared region  232  promotes the ease of applying torque and protects the plurality of vents  230 . In alternative embodiments the flared region  232  is absent. The threaded air vent fitting  117  has a hollow core  233  that extends from the upper tip  122  to the plurality of air vents  230 . In alternative embodiments, the hollow core  233  extends slightly beyond the plurality of vents  230 . In further embodiments, the hollow core  233  extends from the upper tip  122  to the lower tip  225 . 
     A flange  235  is situated adjacent the plurality of vents  230  along the longitudinal axis. A circumferential groove  237  is located along the side of the flange  235  nearest the upper tip  122 . Disposed within the circumferential groove  237  is a gasket (not shown). In one embodiment, the gasket is comprised of silicone, rubber, polyurethane, or the like. Adjacent the flange  235  along the longitudinal axis is disposed a threaded region  242 . The threaded region  242  is designed to couple, for example, with a threaded bore of an electrical enclosure. 
     A connector member  245  extends along the longitudinal axis from the upper tip  122  towards the threaded region  242 . In the illustrated embodiment, the connector member  245  comprises a first cylindrical section  248  approximately matching the diameter of the tubular membrane  121 . A ring shaped projection  249  is formed along the circumferential face of the first cylindrical section  248 . The ring shaped projection  249  has a first diameter  250  disposed near the upper tip  122  and a second diameter  252  disposed further from the upper tip  122 , the first diameter  250  corresponding to the diameter of the cylindrical section  248 , and the second diameter  252  being greater than the cylindrical section  248  in diameter. Between the first diameter  250  and second diameter  252  is formed a truncated cone  255 , as illustrated in  FIG. 2A . In one embodiment, the connector member  245  further comprises a second cylindrical section  260  extending from the upper tip  122  to the first cylindrical section  248 . The second cylindrical section  260  has a diameter approximately equal to the inner diameter of the tubular structural support  125 . 
     When the connector member  245  is inserted into tubular membrane  121 , the ring shaped projection  249  expands tubular membranes  121 &#39;s diameter. In one embodiment, this expansion causes a tight seal due to the tubular membrane&#39;s  121  elasticity and resistance to expansion. Concurrently, the second cylindrical section  260  couples to tubular structural support  125 , providing additional mechanical strength. In certain embodiments a clamping member (not shown) is implemented along the first cylindrical section  248  after insertion into tubular membrane  121  to apply additional securing force. In one embodiment, clamping member is comprised of heat shrink tubing, a wire tie, a cable tie, or the like. 
     In alternative embodiments, securing means other than a threaded fitting are used to attach tubular membrane vent  100  to an enclosure.  FIGS. 3   a ,  3   b , and  3   c  illustrate one possible alternative securing means.  FIG. 3   a  shows a perspective view of a plug air vent fitting, shown generally at  315 , in accordance with one embodiment of the present invention.  FIG. 3   b  illustrates a representation of the same plug air vent fitting  315  in the Y-Z plane.  FIG. 3   c  shows a side view representation of plug air vent fitting  315  cut along line C-C′  318  in the X-Y plane. Plug air vent fitting  315  comprises a first radial portion  317  and a second radial portion  319 , the second radial portion  319  intersecting the first radial portion  317  at a ninety degree angle. In one embodiment first radial portion  317  has a diameter greater than the diameter of second radial portion  319 , and a length less than the length of second radial portion  319 . First radial portion  317  has a first opening  320  and second radial portion  319  has a second opening  324 , second opening  324  intersecting first opening  320  at a right degree angle to form a through air passageway. First radial portion  317  comprises a plug  325 . In one embodiment, plug  325  has a diameter equal to a corresponding bore in an electrical enclosure. In certain embodiments, plug  325  further comprises a flared end  330 . In the illustrated embodiment, second radial portion  319  comprises a connector member  245  as described with respect to  FIGS. 2A and 2B  above. 
       FIGS. 4   a  and  4   b  illustrate a perspective view and a side view, respectively, of a vent cap  129 , in accordance with one embodiment of the present invention. In one embodiment, vent cap  129  comprises substantially the same material or materials as air vent fitting  117 . In the illustrated embodiment, vent cap  129  comprises a connector member  245  described with respect to  FIGS. 2A and 2B  above. Vent cap  129  further comprises a flared end  405 . In alternative embodiments, no vent cap  129  is implemented. Where no vent cap  129  is implemented, in one embodiment tubular membrane  121  is sealed at one end by folding tubular membrane  121  as illustrated in  FIGS. 5   a  and  5   b . In alternative embodiments, tubular membrane  121  is sealed at one end by pinching it off, as illustrated in  FIGS. 5   c  and  5   d . In one embodiment, an adhesive is used to maintain the seal of the pinched off or folded over end. 
       FIG. 6   a  illustrates a perspective view of a tubular membrane vent  100  coupled to an electrical enclosure  503 , shown generally at  500 , in accordance with one embodiment of the present invention.  FIG. 6   b  shows a side view representation of a tubular membrane vent  100  having a threaded air vent fitting  117  coupled to an electrical enclosure wall  505 . As illustrated, the threaded region  242  has a diameter equal to the diameter of a threaded bore  508  in the electrical enclosure wall  505 .  FIG. 6   c  shows a side view representation of a tubular membrane vent  100  having a plug air vent fitting  315  coupled to an electrical enclosure wall  505 . In the illustrated embodiment, the plug air vent fitting  315  has a plug  325  with a flared end  330 , the plug being the same diameter as a bore  510  in the electrical enclosure wall  505 . 
     Tubular membrane vent  100  enables enclosures to maintain weather tight status and protection from wind, rain, icing, dust and the intrusion of water when submersed.