Patent Grant
7100329
This invention relates to a mechanism for attaching covers over openings, anchoring intermediate supports between covers and securing braces behind weak covers and more particularly to the specialized clamping lever which enables these capabilities. Such attachment assemblies are commonly used to attach shutters over window and door openings and to anchor structural columns to brace garage doors and provide intermediate support for shutters during hurricanes.
The present invention relates specifically to the connection and installation of covers of all types over openings of all types without defacing the surface of the openings. Herein after, one of the most severe and dramatic applications will be used to represent all applications—that of the protection of one's home at the approach of a hurricane. Novelty, simplicity, economy, vibration resistance and speed of installation are characteristics of this invention.
The down sides and obvious cost and damage due to hurricanes is common knowledge. The reader is referred to most all patents on the subject for this background and it will not be repeated herein.
Concrete is known and well documented in history as an excellent material in compression. However, in structural uses concrete has zero allowable strength in tension. Only metallic inserts, which create diagonal compression in the creation of a shear cone about the fastener, are attributed to producing tensile attachment. To exacerbate this problem, concrete is friable and subject to crumbling when exposed to cyclical compressive and tensile loading as by the turbulent winds of a hurricane. And yet, most buildings constructed close to ocean shores are concrete.
How then does one generate a resiliently soft but strong compressive force and eliminate the tensile forces as is required by the inherent nature of concrete? And further, how does one transfer this to the violently, fluctuating turbulent loads as generated by hurricane winds? And all the while, economics, ease of handling and speed of installation over a wide diversity of sites and shapes of openings must be provided. This is precisely the teaching of this patent.
The predominant direction of technology and investment is currently to create better inserts for concrete. That is, to try to pack tremendous resiliency in the small clearances between the concrete and the insert. All the while, these devices are making bigger scars on the face of buildings. The approach is generally accompanied by permanent mounting tracks or rails around the openings to further distract from the appearance of the home. (Ref. US2003/0134091 AL etc.) Installations of these critical devices are prone to error as witnessed by the following recent example.
It is no accident that after the landfall of the second tropical storm of 2003 in the USA, in Texas, the greatest cost of damage was attributed to failed inserts into concrete. Vibration loosened the inserts and the winds ripped off shutters burst windows and flooded the buildings with heavy rains. And this was only a class 1 hurricane. Even if the insert stays in, a tremendous disadvantage with inserts is that threaded metal female inserts or threaded studs are left permanently mounted outdoors in saltspray, rain and dusty environments, or, worse, being covered with paint. Even stainless steel in this application is subject to galling and cross threading and galvanized steel is no better. None of these concerns are comforting when a hurricane in rapidly approaching.
The approach of mounting a compressive device inside the opening and using compression to secure it is presented by Holvng in U.S. Pat. No. 5,579,604. As further precedence the reader is referred to his section 3 of this patent—“Description of the Prior Art”. His comments are referenced without exceptions.
The greatest problem, however, with all previous devices is that compressive members over large spans are subject to buckling or collapse due to bending. Therefore compressive members must be laterally braced and or increased in mass and cross section to prevent buckling. This results in more weight, complexity and therefore cost and failure potential. This, in turn increases the difficulty and time of installation.
One final problem, which can be overcome to the detriment of the teachings of U.S. Pat. No. 5,579,604, relates to the lack of detents or shallow holes in the sidewall of the building's openings. Concrete block construction is almost universally finished with stucco. Initial tests on the present invention revealed that most stuccoes crumble under compression and shears off the surface. This leaves sand and chips of debris, which act as a lubricant similar to gravel on a curve in a road. It is necessary to at least penetrate the finish layer and expose solid aggregate to rest the compressive member on. However, additionally, the addition of a slight ridge for the compressive foot to rise over assures that this will not be the weakest link in the design. The present invention relies on the rigidity of the shutter to carry the compressive force. The limiting requirement of a shutter is not its strength but the deflection required by codes. Therefore the specific requirements of each type of material, be it plywood or corrugated steel, plastic or aluminum vary and the allowable spans must be evaluated separately. In any event, the panel is already designed for stiffness and a small limitation of span or increase of metal gauge is the only consequence, depending on the class of hurricane and wind speed being assumed for the geographic area.
A final point regarding inserts and anchors. They require full penetration of the block's web and, in most cases, the introduction of leakage paths of water into the cores of the block. Indoor air quality and mold potential is only now beginning to be addressed. As required by the present invention, the small shallow dents are approximately ⅓ to ½ of the depth of the wall of the block. When painted like the wall and located on the side of the wall rather than the face of the wall it is virtually invisible with no concern of corrosion, thread damage, or contamination of interior air quality.
The object of the present invention is first to generate a tensile latching force by an inexpensive commercially available ratcheting device. And further, this tensile force is transmitted the width of the cover or the length of a structural column by inexpensive, light weight straps. This device is located between the fulcrum points of the panel. Therefore the material required to transfer these forces are only a very light, flexible, and inexpensive strap. Only then are the rigid and strong levers necessary to operate in cooperation with the cover to result in compression against the structure of the opening. The mounting of the assembly is accomplished by simply drilling holes at the margin of the panel, and inserting the levers to convert tensile forces outboard of the shutter to compressive forces bearing on the concrete inboard of shutter.
The geometry of the various load points of the lever and the location of the fulcrum generate an acute angle of the force vector relative to the panel. This clamps a portion of concrete between the lever and the shutters and snuggs the shutter against the outside face of the opening. On thin metal or plastic panels, a grommet is applied to the hole to relieve stress concentrations and deformation of the materials by uniformly distributing the point load over a larger area of the panel.
A further object of the invention is to use the inherent elasticity of the straps to provide constant compression of the levers against the concrete regardless of the turbulent buffeting of the winds. By initially preloading the straps in tension, a large compression force is superimposed over the cyclical loads. Therefore the resultant load is a varying compressive load. This totally eliminates the need for the unattractive inserts and their frequent failure. This concept is well proven by the use of this type of apparatus in cargo clamps on exposed trucks or trailers.
The present invention also is used, without modification to a closely related application of the ratcheting strap type tensioning system. This additional device is a structural column to be used as an intermediate support for spanning of long architectural openings by the shutters. A second object of these columns is the bracing of garage doors. This application consists of structural 2″ thick lumber, a plurality of clamp assemblies and metallic termination angles. This angle provides a narrow fulcrum point for the lever. It also converts what would be an instable bending connection into a stable and strong shear connection.
This design provides the same advantages as described in the shutter. The troublesome inserts are eliminated as they are shown in U.S. Pat. Nos. 5,383,509, and 5,620,038 among others.
Referring to
It will be noted that for stability to exist in the loaded lever, the load point of the fulcrum holes 23 must be located to the right of a line of centers through the load points 17 of the two ends as the lever is shown in
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| Number | Date | Country | |
|---|---|---|---|
| 20050091923 A1 | May 2005 | US |
