Patent Application
20130186008
This invention relates to flexible protective barriers which may be temporarily or permanently erected to protect buildings and occupants or other structures from the effects of high velocity winds or shock waves, with associated debris, resulting from natural phenomena, such as wind storms, and man made events, such as, explosive blasts.
2. Description of the Prior Art
As is known by one skilled in the art of protecting buildings and the like from damage caused by missile-like objects that are occasioned by the heavy winds of hurricanes or tornadoes, there are commercially available variations of hurricane protective devices, often called shutters, that fasten immediately over the frangible area to be protected. These devices are typically expensive to purchase, cumbersome, made from stiff, heavy material such as steel and aircraft quality aluminum alloy or occasionally reinforced plastic. Many shutters need to be manually connected and then removed and stored at each threat of inclement weather. Many others require unsightly and difficult-to-mount reinforcing bars at multiple locations. Further, these known shutters are usually opaque, preventing light from entering a shuttered area and preventing an inhabitant from seeing out. Likewise, it is desirable that police be able to see into buildings to check for inhabitants and to prevent looting which can be a problem in such circumstances. Missiles, even small not potentially damaging missiles, striking these heretofore known shutters create a loud, often frightening noise that is disturbing to inhabitants being protected.
There are many patents that teach the utilization of knitted or woven fabric such as netting, tarpaulins, drop cloths, blankets, sheets wrapping and the like for anchoring down recreational vehicles, nurseries, loose soil and the like. Other protection devices use fabric or netting material to cover a unit to be protected. Typically, the device completely covers the unit, and edges of the fabric are fastened to the ground. Examples of fabric-employing devices are shown in the following patents: U.S. Pat. No. 3,862,876 issued to Graves, U.S. Pat. No. 4,283,888 and U.S. Pat. No. 4,397,122 issued to Cros, U.S. Pat. No. 4,858,395 issued to McQuirk, U.S. Pat. No. 3,949,527 issued to Double et al., U.S. Pat. No. 3,805,816 issued to Nolte, U.S. Pat. No. 5,522,184 issued to Oviedo-Reyes, U.S. Pat. No. 4,590,714 issued to Walker and U.S. Pat. No. 5,347,768 issued to Pineda. The U.S. Pat. No. 5,522,184 for example, provides a netting that fits flush over the roof of a building and uses a complicated anchoring system to tie down the netting.
What is needed in the art is a wind, rain and debris protective system, for individual openings, that can be installed during the construction of a building, either on the inside or outside of windows and doors or can be added to existing structures.
A kit for protecting openings in a structure from penetration by debris, rain, and the force of high wind. The basic kit employs a polypropylene, woven monofilament geotextile material for use in temporary coupling to a structure opening, such as a window opening. The basic kit includes fasteners that secure the material over the opening and, should the opening be breached such as when a window is broken, the material maintains the envelope of the structure.
Alternatively the material can be used in combination with a retainer permanently secured to the structure wherein the material is temporarily placed into the retainer. In a preferred embodiment, the retainer has a flat flange with a channel on one edge and a longitudinal slit. The flat flange is adapted to cooperate with fasteners to connect the retainer to the structure with said channel extending parallel with the openings, and a flexible material with reinforced margins. The reinforced margins include a slide adapted to telescopically engage the channel with the material in the slit whereby the flexible material spans the openings when the slide is secured in the channel.
Thus, an object of this invention is to provide a barrier made from flexible material to protect the weak portions of the structure envelope including but not limited to, EIFS walls, windows, covered sections and openings of a building and the like from the force of wind, rain and impact from wind-borne debris.
Another objective of this invention is to provide the use of a retainer for securing the two opposing edges of a wind barrier material to retainer anchors located so as to form a structure envelope about the openings with the barrier spanning the opening.
Another object of this invention is that it may be sold as an after market kit to be installed on existing structures.
Yet another object of this invention is that it can be included in manufactured components, such as windows and doors, for installation in new or existing structures.
A further object of this invention is that the material fabric can be installed as an integral part of a structure during new construction.
Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.
This invention contemplates the use of a flexible barrier, preferably a reasonably transparent, woven synthetic textile material that is able to satisfy stringent testing requirements. The flexible material is capable of withstanding high impact loads without bursting, can be disposed in front of a window or door intended to be protected, and anchored on opposing edges by either direct fastening to the walls of the structure or by use of a retainer for anchoring. Once the material is anchored it is able to contain the impact of foreign objects hurled by the high winds.
When the kit is used with a building, for example, the kit may include retainers that are permanently fastened to the top of a window or door and the bottom of the window, door, or opening. The fabric material may then include a flexible rod formed integral with the material along the opposing edges that is slidably secured into the retainer. Alternatively, the fabric may be anchored at the opposed sides of the window or door. Knitted or extruded material can be used if the material itself meets the criteria described later herein.
Although air travels through the material 11, the barrier is approximately 95% closed, and the velocity of wind passing is greatly reduced and passage of rain effectively stopped. The preferred embodiment has interstices such that rain sheets on the barrier or air flow through the barrier is reduced or stopped. For example, the velocity of a 100 mph wind is reduced by approximately 97% by passing through the fabric material 11 of the present invention. The material fabric of the present invention substantially reduces the force of wind passing through the fabric material and also provides protection against wind-borne missiles having diameters of approximately 3/16 inch in diameter or larger. The ability to provide protection from wind forces and solid debris in the form of an envelope structure represents a step forward in this field. Further, the barrier maintains integrity of the structure, even if the frangible portions of the opening are broken.
The use of the barrier allows very large areas with spans of greater than 25 feet to be covered with ease. Thus, most window groupings could be readily protected. This invention is light in weight, easy to use, does not require reinforcing bars, can be constructed in varying degrees of transparency, can be weather tight, is economical, and is capable of dissipating far greater forces without damage than stiff devices. Missiles striking this barrier make very little sound.
The material 11 does not have rigidity but rather is very flexible, which gives several positive features including allowing for ease of storage as by rolling or folding. Also, the material fabrics may be easily installed by sliding the reinforced margins through the channels. The flexible barrier may be placed a distance out from the surface to be protected to prevent window breakage. However, if the barrier is not distanced from the surface from the window, an impact may cause loss of the window, the material maintains the structure envelop to prevent total loss of the building, which typically occurs when the structure envelop integrity is breached and high winds are allowed inside the structure.
In operation, an impacting missile stretches the material fabric until it decelerates to a stop or is deflected. The fabric material has a predetermined tensile strength and stretch that makes it suitable for this application. Said known strength and stretch, together with the speed, weight and size of the impacting missile, all of which are given in test requirements, permit design calculation to ascertain barrier deflection at impact. This deflection is a determinate of the optimum distance that this barrier is to be spaced out from the frangible area to be protected. Other determinates which may be included are additional deflection from wind pressure and from slack from an improper installation.
If the decision is to position the barrier out a distance from a window, the frangible surface need not be great and may be sufficient without the use of a standoff. If the window is proximate the outside wall of the structure, or is a large window, the distance can be ascertained which permits a time of deceleration such that the barrier will stop far stronger impacts than with the heretofore known rigid devices. In simple terms, the missile is slowed to a stop by elasticity as the barrier stretches. The greater the impact, the greater the stretch. Thus the building is not subjected to an abrupt harsh blow as the impact on the shutter is transferred to the building. The energy transfer is much gentler and less destructive than with the rigid devices.
The interstices of the material fabric permit the light to pass through and is reasonably transparent. If transparency is not desirable, the fabric can be made sufficiently dense to minimize or eliminate the interstices. To assure a long life, the material of the fabric preferably would be resistant to the ultra violet radiation, and to biological and chemical degradation such as are ordinarily found outdoors. This invention contemplates either coating the material or utilizing material with inherent resistance to withstand these elements. A synthetic material such as polypropylene has been found to be acceptable. An example of a coated material is vinyl coated polyester. Materials intended to be used outdoors in trampolines, for example, are likely candidates for use in this invention. Black colored polypropylene is most resistant to degradation from ultra violet radiation. Other colors and vinyl coated polyester are sufficiently resistant, particularly if the barrier is not intended to be stored in direct sunlight when not in use.
The material fabric of the instant invention allows air passage through it when dry, albeit at substantially reduced rate. Moisture on the fabric further reduces air passage. An upwind over pressure of 1″ of mercury, which roughly translates into a 100 mph wind, forces air through at 250 cubic feet per minute (cfm) or approximately 3 mph. The amount of air passage depends on the interstice size. If further protection is desired, the polypropylene material may be laminated with a flexible plastic skin.
It is of importance that the material affords sufficient impact protection to meet the regulatory agencies' requirements in order for this to be a viable alternative to other hurricane protective mechanisms. While stiff structures, such as panels of metal, are easily tested for impact requirement and have certain defined standards, fabrics on the other hand, are flexible and react differently from stiff structures. Hence the testing thereof is not as easily quantified as the stiffer materials. However, certain empirical relationships exist so that correlation can be made to compare the two mediums. Typically, the current impact test of certain locales requires a wood 2×4 stud be shot at the barrier exerting a total force of approximately 230 pounds, or 61.3 pounds per square inch (psi), over its frontal (impacting) surface. This impact and resultant force relate to the Mullen Burst test commonly used by manufacturers to measure the bursting strength of their fabrics. Thus the impact test heretofore used on rigid devices will work equally well on this flexible device.
The preferred embodiment of this invention would use a textile having at least a burst pressure of 675 psi or a total of 2,531.25 pounds over the same 3.75 square inch frontal surface of the nominal 2×4 test missile and would stretch 21% immediately prior to failure. The strength and stretch characteristics of the material are known. The strength of this fabric is more than eleven (11) times the 230 pounds of strength required to withstand the above-described 2×4 missile test as presently required by said regulatory agencies. Stronger fabrics are available. Others are available in various strengths, colors and patterns.
In the alternative embodiment, the use of flexible fabric material distanced out from the frangible area as a protective barrier allows extended deceleration. When the strength and stretch properties of the fabric are known and allowed for, the extended deceleration becomes controlled.
The material fabric 11 of this invention is easy to install, requires low maintenance and has low acquisition cost. There is much flexibility with storage. It is preferable but not essential, that the material selected to be used in the material fabric of this invention be inherently resistant to elements encountered in the outdoors or can be coated with coatings that afford resistance to these elements. A suitable material is polypropylene formed in a monofilament and woven into a geotextile (style 20458) manufactured by Synthetic Industries of Gainesville, Ga. The fabric is woven in a basket (plain) weave as shown in
The material selected must meet certain strength criteria. These criteria, together with the size of span covered by the barrier, constitute the basis for calculating the deflection of the barrier. Said deflection is calculated as follows:
1) The fabric must be sufficiently strong that the impact force it is required to withstand is less than the failure force (Mullen Burst).
2) The impact (test) force is then divided by the force required to cause failure (Mullen Burst). This quotient is then multiplied by the known stretch at failure to obtain the stretch factor. The woven polypropylene synthetic fabrics of the type used in the preferred embodiment stretch 20-22% just prior to failure, depending on manufacturing technique. This stretch information is available from the manufacturer.
3) The actual stretch measurement is then calculated and in conjunction with the span of the barrier used to ascertain the maximum deflection.
The preferred embodiment is used as an example to demonstrate this formula. The preferred embodiment is a polypropylene, woven monofilament geotextile. The individual filaments are woven into a basket weave network and calendered so that the filaments retain dimensional stability relative to each other. This geotextile is resistant to ultra violet degradation and to biological and chemical environments normally found in soils. This fabric is often used as the mat for outdoor trampolines and is intended to be very resistant to weathering. The fabric is known to stretch a maximum of 21% prior to failure and requires a force of 675 psi to fail.
1. The present test that was originally legislated by Dade County Florida and may become the standard in the industry, requires the barrier to withstand a force of only 61.3 psi. Consequently the fabric meets and exceeds the first requirement of strength.
1. The stretch factor calculation is (test load/maximum load×% stretch at maximum load=stretch factor) 61.3/675×21=1.9%. This becomes a constant factor insofar as this fabric and the Dade test remain involved. The calculation will change if any one or more of the strength, energy or stretch characteristics of the test or fabric are modified Likewise, it is known that stretch varies directly with force up to the maximum at failure. To calculate the actual stretch, the calculation is stretch factor×height=actual stretch. Therefore if the distance between the two fastened sides is eight feet (96 inches), the stretch measurement will be 96×1.9%=1.83″.
2. To calculate the deflection, right triangles are used such that the hypotenuse is ½ of the sum of the height plus stretch (97.83/2=48.92″). The known side is ½ of the height (96/2=48″). Thus the deflection=the square root of the difference between the square of the hypotenuse less the square of the known side. This result is 9.4″ which is the maximum deflection on impact by test missile.
3. Thus the barrier will deflect at least 9.4 inches if an eight (8) foot span is to be used. A longer span will require wider spacing, a shorter will require less. The table shown below reflects this deflection for various sample distances of span with this preferred fabric.
Table demonstrating relationship between Span and Maximum Deflection if spacing apart from a window is preferred.
As the deflection is intended to be minimum, and although the barrier is intended to meet or exceed test standards as opposed to warranting protection in actual situations which are difficult to predict, this invention can include an additional factor in the deflection to allow for maximum wind pressure. Arbitrarily assuming a 115 mph wind at 90 degrees to the barrier and assuming the barrier has been made weather tight with no air flow through the barrier to somewhat relieve pressure, and assuming the barrier is installed at sea level where air is densest, the additional pressure on the barrier will be 0.237 pounds per linear inch of span. This additional pressure can be resolved into a vector and added directly to the test force of 61.3 pounds. Thus an 8 foot barrier will have an additional (0.237×96=) 22.75 pounds added for a total of 84.05 pounds. A 40 foot barrier will have (0.237×480=) 113.76 pounds added for a total of 175.06 pounds. This number should be substituted into the above formula to give a more accurate calculation of deflection.
For example: an 8 foot barrier could deflect 10.9″ when allowing for a 115 mph wind factor rather than 9.7″ if the wind was not factored in. The deflection of a 40 foot barrier becomes 80.28″ (6.69°) rather than 47″ (3.9°). If the window is not necessary to salvage, deflection is not of concern as the fabric material will prevent loss of envelop integrity.
The fabric must be anchored in a suitable manner so as to absorb the loads without being torn from its support. While various hardware devices may be used to anchor the fabric in place, general criteria include stainless steel screws or nails 13 with sufficient pull out strength in both wood and concrete to withstand the stress created by the material fabric 11. These criteria are merely exemplary and not limiting. Other anchoring hardware may be used to install the protective barrier of this invention.
In
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The retainer 16, shown in
The channel 19 cooperates with the bead 23 to connect the retainer 16 and the material fabric 11. The slots 22 may be oriented in the channels to face each other across the span of the material fabric 11. This places the strain directly on the selvedge edge of the material fabric, the joint with the bead, and the opposite edges of the slots 22. In the alternative, the slots may be rotated at an angle from each other so that the material fabric engages one edge of each slot continuously and reduces the strain on the selvedge and the bead.
In
Depending on whether the barrier is purchased as part of new construction, or part of manufactured components, or as after market improvements, the end result places the retainers along two opposed sides of windows and/or doors, either inside or outside the building. The material fabrics are supplied either pre-cut to size or in a supply roll. Once the building is finished or the retainers installed, the sized material fabrics can be removably mounted quickly. The opposite beads are threaded into the opposed channels of the retainers and the material fabrics are slid into position covering the frangible elements of the doors and windows.
A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiment but only by the scope of the appended claims.
This application is a continuation of U.S. patent application Ser. No. 10/871,557, filed Jun. 18, 2004.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10871557 | Jun 2004 | US |
| Child | 13725948 | US |
