US20080047596A1 - Vents for temporary shelters and coverings - Google Patents

Abstract

A venting system for a temporary shelter that includes one or more vents that are positioned in the exterior shell of the temporary shelter. Each of the one or more vents may include a membrane that is moisture vapor transmissive and resistant to liquid penetration. The membrane may have a moisture vapor transmissive rate of at least 4,000 g/m²/day. The membrane may be expanded polytetrafluoroethylene. The one or more vents may have a size such that there is approximately 4 m²of vent surface area in the exterior shell of the temporary shelter per 20 m³of interior space within the temporary shelter.

Description

TECHNICAL FIELD
• This present application relates generally to improved vents for temporary shelters and coverings. More specifically, but not by way of limitation, the present application relates to systems for providing breathable, water resistant membrane vents in temporary shelters or coverings to prevent humidity or heat build-up.
BACKGROUND OF THE INVENTION
• Temporary shelters, such as tents, temporary sheds, mobile military structures, typically are made from non-breathable fabrics or membranes. Because of the metabolic breathing process of occupants as well as other activities, such as cooking, occupation of these structures causes humidity build-up. Humidity build-up may create an uncomfortable condition for the occupants, condensation issues, damage to electrical equipment by water, and other problems. Further, coverings for electrical equipment and other types of equipment, such as weapons, automobiles or aircraft, may experience humidity or heat build-up, either from heat generation within the cover by the equipment or by exposure to the sun coupled with moisture.
• Certain types of vents have been employed in temporary shelters and coverings to vent built-up humidity or heat to the atmosphere. However, conventional vents often employ mesh, which is susceptible to water penetration. More specifically, mesh and other similar vent materials allow water to enter the temporary shelter or covering, which may be uncomfortable to the occupants, lead to issues with electrical equipment housed therein or cause other problems. The problem also has been solved with the use of electric dehumidifiers. However, temporary shelters often are located in remote areas where electric service is unavailable.
• Thus, there is a need for improved venting systems in temporary shelters and covering. Such improved venting systems will allow for excess water vapor to be vented to the atmosphere while preventing the penetration into the temporary structure of undesirable external conditions, such as water, dust, sand, insects, wind, microbes and the like.
BRIEF DESCRIPTION OF THE INVENTION
• The present application thus may describe a venting system for a temporary shelter that includes one or more vents that are positioned in the exterior shell of the temporary shelter. Each of the one or more vents may include a membrane that is moisture vapor transmissive and resistant to liquid penetration. The membrane may have a moisture vapor transmissive rate of at least 4,000 g/m²/day.
• The one or more vents may include a laminated fabric that includes the membrane and a base fabric. The base fabric may include a woven, non-woven or knit textile. The base fabric may include a flame retardant material.
• In some embodiments, the membrane may be air permeable and immune to liquid penetration. At least one of the vents may be positioned in the upper part of a side of the temporary shelter. In some embodiments, the membrane may be oleophobic. The membrane may be expanded polytetrafluoroethylene.
• In some embodiments, the one or more vents may be incorporated into the temporary shelter by a waterproof zipper. In other embodiments, each of the one or more vents may be welded onto a corresponding opening in the exterior shell of the temporary shelter. In other embodiments, each of the one or more vents may be stitched directly onto a corresponding opening in the exterior shell of the temporary shelter and seam tape may be used to seal the stitch holes from water leaks. The one or more vents may have a size such that there is approximately 4 m²of vent surface area in the exterior shell of the temporary shelter per 20 m³of interior space within the temporary shelter.
• The present application may further describe a structure for enclosing items, such as people or equipment, capable of generating heat or humidity. The structure may include an exterior wall and one or more vents incorporated in the exterior wall. The one or more vents may include a membrane that is moisture vapor transmissive to permit release of heat or humidity from within the structure and resistant to liquid penetration. The one or more vents may have a size such that there is approximately 4 m²of vent surface area in the exterior wall of the structure per 20 m³of interior space within the structure.
• In some embodiments, the membrane may be oleophobic. The membrane further may be air permeable and immune to liquid penetration. The membrane may be expanded polytetrafluoroethylene. The membrane may have a moisture vapor transmissive rate of at least 4,000 g/m²/day. In some embodiments, a positive air pressure may be maintained in the structure. These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of an exemplary temporary shelter with vents in accordance with exemplary embodiments of the present invention.
• FIG. 2 is a schematic sectional view of a laminated fabric that includes a composite membrane which may be used in accordance with certain embodiments of the present invention.
• FIG. 3 is an enlarged schematic plan view of a portion of the membrane illustrated inFIG. 2, viewed approximately along the line2-2 inFIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 illustrates a perspective view of a tent ortemporary shelter2 in which exemplary embodiments of the present application may be used. Thetemporary shelter2 may include an exterior fabric orshell3 that is supported by two flexible, crossingrods4 such that thetemporary shelter2 has four sides and an approximate dome shape. Those of ordinary skill in the art will recognize that the configuration oftemporary shelter2 is exemplary only and that other tent or temporary shelter configurations may be used with the invention described herein. Further, one of ordinary skill in the art will recognize that the inventive concepts described in relation to thetemporary shelter2 may be readily applied to other types of coverings, such as coverings for electrical equipment, weapons, automobiles or aircraft, that may experience heat or humidity build-up. Thus, for the sake of simplicity, exemplary embodiments will be discussed in relation to thetemporary shelter2 example, though it will be appreciated that the embodiments may be used with other types of tents, temporary shelters, and other coverings.
• Thetemporary shelter2 may include adoor6 for egress, which may zipper between and open and closed position. Thetemporary shelter2 further may include one ormore vents8. Thevents8 may be made of a laminated fabric that includes a breathable, water-resistant or waterproof membrane. Thevents8 thus may allow water vapor to be vented to the atmosphere while being resistant or immune to water penetration, as described in more detail below. Thevents8 may be located in theexterior shell3 of thetemporary shelter2. As shown, it may be advantageous to locate thevents8 in the upper part (i.e., the top third) of each of the sides of the temporary shelter such that the warmer, more humid air inside thetemporary shelter2 is vented to the atmosphere. In some embodiments, as depicted inFIG. 1, thetemporary shelter2 may includerectangular vents8 that are located in the upper part of each of its sides.
• The membrane of thevent8 may be: 1) breathable, including moisture vapor transmissive and 2) resistant or immune to liquid penetration (which, in combination, is often referred to as “waterproof breathable”). In some embodiments, thevent8 maybe air permeable. In general, “moisture vapor transmissive” is used to describe a membrane that readily permits the passage of water vapor. In some embodiments of the current application, the moisture vapor transmissive rate (“MVTR”) of the membrane is at least 4,000 g/m²/day (as tested per JIS L 1099 B-2 procedures). The term “immune to liquid penetration” is used to describe a membrane that is not “wet” or “wet out” by a challenge liquid, such as water, and prevents the penetration of liquid through the membrane under varying ambient conditions.
• In one embodiment, thevent8 of the present application may include a membrane that is made from expanded polytetrafluoroethylene (“ePTFE”). In general, an ePTFE membrane is air permeable and moisture vapor transmissive, yet resistant or immune to liquid penetration at moderate pressures.FIG. 2 demonstrates a cross-section of an exemplary ePTFE laminatedfabric10, which may be used according to exemplary embodiments of the present application. TheePTFE laminate fabric10 may include anePTFE membrane12 and a shell orbase fabric14. TheePTFE membrane12 may include amembrane16. TheePTFE membrane12 is typically laminated to thebase fabric14 to create theePTFE laminate fabric10. TheePTFE membrane12 and thebase fabric14 may be laminated pursuant to a thermal lamination process, adhesive lamination process, or other conventional methods. Thebase fabric14 may be laminated to one side for both sides of theePTFE membrane12. Thebase fabric14 may be a woven, nonwoven or knit textile.
• As demonstrated inFIG. 3, themembrane16 of theePTFE membrane12 may be porous, and preferably microporous, with a three-dimensional matrix or lattice type structure ofnumerous nodes22 interconnected bynumerous fibrils24. Surfaces of thenodes22 andfibrils24 may define numerous interconnectingpores26 that extend through themembrane16 between oppositemajor sides18,20 of the membrane. ePTFE membranes are more fully described in U.S. Pat. Nos. 6,228,477; 6,410,084; 6,676,993; 6,854,603; and U.S. Published Patent Application U.S. 2004/0059717, which are incorporated herein in their entirety. In some embodiments, themembrane16 may be oleophobic. Those of ordinary skill in the art will appreciate that the description herein of thespecific ePTFE membrane12 is exemplary only and that other types of membranes may be used with the exemplary embodiments described herein. For example, such similar membranes may include microporous or non-microporous polyolefins, polyurethanes, polyesters, polyamides, polyethersulfones, cellulose acetate and the like.
• As stated, thevents8 may be made of a laminated fabric that includes a membrane. Further, according to certain embodiments, the laminated fabric may be the ePTFE laminatedfabric10 that includes anePTFE membrane12. TheePTFE membrane12 may be laminated to thebase fabric14, which may be chosen for its strength (tensile and tear strength), durability, durability against ultraviolet radiation, ability to block-out light, flame retardant characteristics, softness, drapeability, and ability to seamseal. Thus, for example, thebase fabric14 may be made of polyamides, polyesters, polyolefins or other similar materials. Flame retardant fibers, such as Nomex® also may be blended into thebase fabric14. As described, thebase fabric14 may be laminated on one or both sides of theePTFE membrane12 pursuant to the processes described above.
• Thevents8 may be integrated into the sides of thetemporary shelter2 by several means. In some embodiments, waterproof zippers may be attached to the periphery of thevent8 and onto the corresponding opening in theexterior shell3 of thetemporary shelter2. Thevent8 then may be zipped into place. This method of integration may allow for the easy replacement of worn or damagedvents8. In other embodiments, thevent8 may be stitched directly into theexterior shell3 of thetemporary shelter2. Seam tape or other similar material may be used to seal the stitch holes from water leaks. In other embodiments, thevents8 may be weld onto the corresponding openings in theexterior shell3. Any of the known processes for imparting energy for completed the weld may be used, such as ultrasonic, radio frequency, hot air gun, hot plate and the like.
• Thevents8 may be sized in thetemporary shelter2 so that thevents8 perform efficiently while also being cost effective. More specifically, thevents8 may be sized to a minimum size at which thevents8 maintain a comfortable humidity level within thetemporary shelter2 assuming a certain level of occupation. In this manner, thevents8 are not sized too large, which might be wasteful from a cost perspective, or sized too small, which might not be able to maintain a comfortable humidity level within thetemporary shelter2. Given these competing criteria, it has been discovered that an efficient size for thevents8 is approximately 4 m²of vent surface area in the exterior shell of thetemporary shelter2 per 20 m of interior space within thetemporary shelter2. This sizing assumes an occupancy rate of approximately one person per 10 m³of interior space.
• Accordingly, if the vent sizing ratio of approximately 4 m²of vent surface area in the exterior shell of thetemporary shelter2 per 20 m³of interior space within thetemporary shelter2 is maintained, the relative humidity will not exceed comfortable levels. For example, it has been discovered that in a hot, dry desert environment, given the parameters and occupancy rate described above, the relative humidity will stabilize at about 60-70% if thevents8 are included at the described vent sizing ratio (i.e., approximately 4 m²of vent surface area in the exterior shell of thetemporary shelter2 per 20 m³of interior space within the temporary shelter2). Note this example assumes that the inside temperature of thetemporary shelter2 is maintained at 25° C. and that the outside conditions include a temperature of 45° C. and 10% relative humidity. If, given the occupancy rate described above. thevents8 were not included in this example, the relative humidity inside thetemporary shelter2 would exceed 100% in approximately one hour.
• To take another example, it has been discovered that in a cold, wet environment, given the parameters and occupancy rate described above, the relative humidity will stabilize at about 40-50% if thevents8 are included at the described vent sizing ratio (i.e., approximately 4 m²of vent surface area in the exterior shell of thetemporary shelter2 per 20 m³of interior space within the temporary shelter2). Note this example assumes that the inside temperature of thetemporary shelter2 is maintained at 25° C. and that the outside conditions include a temperature of −10° C. and 60% relative humidity. If, given the occupancy rate described above, thevents8 were not included in this example, the relative humidity inside thetemporary shelter2 would exceed 100% in approximately one hour. Note that in some alternative embodiments thevents8 may be sized smaller or larger than the ratio described above. Further, in other alternative embodiments, a positive air pressure may be maintained in thetemporary shelter2 pursuant to conventional means. The positive air pressure may aid with the egress of moisture vapor through thevent8.
• From the above description of preferred embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.

Claims (20)

1. A venting system for a temporary shelter, comprising:

one or more vents positioned in an exterior shell of the temporary shelter;

wherein each of the vents include a membrane that is moisture vapor transmissive and resistant to liquid penetration.

2. The system ofclaim 1, wherein the membrane comprises a moisture vapor transmissive rate of at least 4,000 g/m²/day.

3. The system ofclaim 1, wherein the one or more vents comprise a laminated fabric that includes the membrane and a base fabric.

4. The system ofclaim 3, wherein the base fabric comprises a woven, non-woven or knit textile.

5. The system ofclaim 3, wherein the base fabric comprises a flame retardant material.

6. The system ofclaim 1, wherein the membrane is air permeable and immune to liquid penetration.

7. The system ofclaim 1, wherein at least one of the vents is positioned in the upper part of a side of the temporary shelter.

8. The system ofclaim 1, wherein the membrane is oleophobic.

9. The system ofclaim 1, wherein the membrane comprises expanded polytetrafluoroethylene.

10. The system ofclaim 1, wherein the one or more vents are incorporated into the temporary shelter by a waterproof zipper.

11. The system ofclaim 1, wherein each of the one or more vents is welded onto a corresponding opening in the exterior shell of the temporary shelter.

12. The system ofclaim 1, wherein each of the one or more vents is stitched directly onto a corresponding opening in the exterior shell of the temporary shelter and seam tape is used to seal the stitch holes from water leaks.

13. The system ofclaim 1, wherein the one or more vents comprise a size such that there is approximately 4 m²of vent surface area in the exterior shell of the temporary shelter per 20 m³of interior space within the temporary shelter.

14. A structure for enclosing items, such as people or equipment, capable of generating heat or humidity, said structure comprising:

an exterior wall; and

one or more vents incorporated in the exterior wall, the one or more vents comprising a membrane that is moisture vapor transmissive to permit release of heat or humidity from within the structure and resistant to liquid penetration.

15. The structure ofclaim 14, wherein the one or more vents comprise a size such that there is approximately 4 m²of vent surface area in the exterior wall of the structure per 20 m³of interior space within the structure.

16. The structure ofclaim 14, wherein the membrane is oleophobic.

17. The structure ofclaim 14, wherein the membrane is air permeable and immune to liquid penetration.

18. The structure ofclaim 14, wherein the membrane comprises expanded polytetrafluoroethylene.

19. The structure ofclaim 14, wherein the membrane comprises a moisture vapor transmissive rate of at least 4,000 g/m²/day.

20. The structure ofclaim 14, wherein a positive air pressure is maintained in the structure.

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