Patent Application
20180298660
The following is a tabulation of some prior art that presently appears relevant:
Overhead doors are used for a variety of applications, from refrigerated area closures to light aircraft hangar doors. Design requirements include thermal insulation, structural resistance to lateral loads, such as pressure induced by wind, and security requirements. Among the most common uses are residential and commercial garage closures.
Existing overhead door designs are herein classified into two general categories: (a) single and dual panel designs and (b) designs primarily comprised of a plurality of panels or slats which are connected by hinge mechanisms. General category (a) is further refined to include: (a1) rigid panel designs, (a2) flexible single sheet panel designs and (a3) flexible multi-layer panel designs. General category (b) is also further refined: (b1) rollup designs where, in the open configuration, the panels are rolled onto a horizontal cylindrical mandrel and (b2) track supported designs where, in the open configuration, the panels are supported by tracks.
Due to the large number of overhead door designs, only representative examples of the design categories are discussed below.
(a1) U.S. Pat. No. 4,294,055, describing a single panel door, is included within the rigid panel design category. This design has a relatively large strength-to-weight ratio due to its utilization of a sandwich design consisting of thin interior and exterior sheets bonded to a metallic honeycomb core. The open-close mechanism consists of a relatively complicated strut and spring design. U.S. patent application 20150376933 also describes a single rigid panel design where the door structure is a heavy stiffened frame requiring the use of rams in the open-close mechanisms. Finally, U.S. Pat. No. 4,545,417 depicts a horizontally hinged two-panel rigid door whose weight is counterbalanced by a complicated cable-weight-pulley system. All of the designs in this category are characterized by relatively heavy—to very heavy structures requiring complicated open-close mechanisms. An additional disadvantage of this design category is the clearance space required during open-close operations.
(a2) U.S. Pat. No. 7,231,953 discloses a rollup design within the single flexible panel design category. The door consists of single flexible thin sheet, reinforced by attached horizontal bars. The complete assembly is rolled onto a cylindrical mandrel upon opening. U.S. patent application 20030173040 depicts a similar basic design (single flexible sheet with attached horizontal reinforcing bars) with the exception that the door is constrained to follow guide-support tracks, which transition to the horizontal during opening. The primary disadvantages of the single thin sheet designs are lack of transverse thermal insulation and minimal structural resistance to applied transverse loads.
(a3) The flexible multi-layer single panel design category is illustrated by U.S. patent applications 20100132894 and 20160024837. In both designs, the multi-layer panel is utilized primarily for thermal insulation rather than providing structural capability for lateral load resistance. The former panel design consists of two very flexible skins with a non-structural insulating material sandwiched between the skins. The latter panel design consists of a thin structural skin which is bonded to a thicker non-structural insulating material layer. The 2010 application design open-close operation is primarily in a vertical plane, whereas, in the latter application design, the flexible panel is supported and guided by rods which constrain the door to be in a horizontal position when open. Both designs have limited structural capability to resist lateral loads, such as pressures induced by wind.
(b1) Overhead rollup door, multi panel designs are ubiquitous, usually employed where security is a primary design requirement. U.S. Pat. No. 6,883,577 and U.S. patent application 20110265959 depict typical designs in this category. As with most of these designs, the individual panels are compact, having large aspect ratio and bending stiffness. This results in a heavy door design and, due to the large number of panel-to-panel hinge connections, non-optimal weather tightness and thermal insulation.
(b2) Overhead retracted, track supported, plural panel door designs are perhaps the most numerous within the discussed design categories. U.S. patent application 20040099382 and U.S. Pat. No. 4,460,030 present designs where the individual panels are compact with high aspect ratio, similar to those designs in the (b1) category. The former is stowed in the conventional horizontal plane whereas the latter is stowed in an accordion configuration. U.S. patent application 20120318468 and U.S. Pat. Nos. 4,452,293 and 5,555,923 all disclose designs there the individual panels are comprised of a number of rectangular cells, utilized for improved structural capability and thermal insulation. As with category (b1) designs, these designs have, generally, reduced weather tightness. Sandwich plates or shells, comprised of two relatively thin elastic sheets bonded to a core medium, have high lateral load to structure weight ratio and stiffness to weight ratio. A door utilizing conventional sandwich design, such as the design disclosed in U.S. Pat. No. 4,294,055, has the disadvantages summarized in category (a1) designs. As discussed in the following paragraph, the cellular panel designs summarized in design category (b2), utilize a sandwich-like design where strength-weight ratio is improved. However these designs retain the non-weather tightness limitation.
Arendts (1969), as summarized in Arendts and Sanders (1970), shows that structures, such as box girder bridges, consisting of two relatively thin elastic sheets connected by a plurality of transverse webs, theoretically and actually behave as sandwich plates with orthogonally differing core transverse shear properties. Such a structural panel may be modified, through hinging the web-sheet connections, so that it is flexible. Overall stiffness and strength of the panel is not significantly reduced by hinging the webs and stability is achieved through proper support of the overall structural system.
A flexible unitary sandwich-like panel overhead door consists of two relatively thin elastic sheets connected by a plurality of elongated parallel web panels. These connections are hinged so that the panel may be flexibly moved from a closed vertical position to an open overhead nearly horizontal configuration. Stability and strength of the panel are achieved through proper internal and external support of the door structure.
This flexible unitary sandwich-like panel door has the following advantages when compared with other existing door system designs:
(a) Very large allowable transverse load to structural weight ratio,
(b) Very large lateral stiffness to structural weight ratio,
(c) Weather tightness,
(d) Ability to provide closure for pressure boundaries,
(e) Excellent transverse heat insulation due to constrained air in the panel void spaces,
(f) Ability to quietly transition the door between closed and open configurations.
In the drawings, closely related figures have the same number but differing alphabetical suffixes.
This embodiment is illustrated in
Note that two support rollers 16 are provided at each end of beam 17 so as to prevent axial rotation of the beam with respect to the door supports. This is important for maintenance of strength and stiffness of the door: overall door bending strength about an in-plane horizontal axis is dependent on limiting relative vertical motion of the inner and outer sheets, 12 and 13. Also important for limiting this relative motion are relatively large torsional and flexural beam 17 stiffnesses: a beam with hollow closed rectangular cross-section (box-beam) is optimal for this usage. An extruded high strength metallic material or fiber reinforced polymer (FRP) could be used to construct the box-beam.
The elastic sheets, 12 and 13, could be comprised of homogenous metallic material or of composite construction (FRP). The webs, 14, are subject to only in-plane stresses due to bending stress relief of the hinges, and may thus be constructed of light homogeneous materials or a FRP wrapped core. The hinges, 15, could be conventional mechanical hinges or constructed of flexible polymer composite. Various methods may be employed for hinge attachment to sheets and webs, including mechanical (rivets or spot welds) or adhesives. Also, the webs may be designed to include the hinge elements so that the only attachments required are web-to-sheets.
Operation of the first embodiment door is shown in the cutaway views depicted in
Maximum strain, emax, in a cylindrically bent elastic sheet is given by the following well known relationship:
emax=t/(2R),
where t is the thickness and R (32) is a typical radius of curvature of the bent sheet. From this relationship, a design t/R ratio is determined by equating emax with the material design strain, as determined in the preceding paragraph.
It is noted from the cross-sections (
The net result of this web rotation effect is that the maximum allowable support track rotation angle 31 (
Construction methods required for production of this door embodiment are extremely simple, especially when adhesives are utilized for hinge attachments. For the manufacture of an adhesive bonded planar part of the embodiment, web elements, together with attached support rollers and hinges, are premanufactured. Then, a single elastic face sheet is placed on a horizontal surface, web assemblies and adhesive positioned on the sheet, and the other face sheet placed on this subassembly. Finally, pressure and/or heat is applied to the final assembly, as required for adhesive curing.
Construction of a planar part of the embodiment utilizing mechanical hinge attachment methods is somewhat more complicated. In this case, after pre-manufacture of the web-roller-hinge elements, both sheets may be elastically bent so as to more easily allow mechanical attachment of the webs to the sheets.
After manufacture of the planar portion of the embodiment, relative in-plane motion of the sheets then allows the sheets to separate, and the box-beam to sheet attachments to be made. Additional nonessential parts (not shown in the drawings) such as a floor contact wear strip and seal may be easily attached to this embodiment.
Operation of the embodiment is identical to the majority of track supported and guided overhead doors (category b2 doors discussed above): conventional support tracks and a commercially available powered open-close mechanism are utilized
For those applications where the elevation of an adjacent ceiling or roof truss is only slightly greater than the door height (limited clearance applications), two additional embodiments are presented in which the support track bend angle 31 is increased to 90 degrees.
Second embodiment cross-sections are shown in
Also shown in
It is noted that for a given web width (or embodiment unit weight), the overall bending strength and stiffness of the second embodiment are somewhat less than corresponding first embodiment characteristics.
A third embodiment presents an alternate design where the bend angle 31 is increased to 90 degrees with similar bending strength and stiffness as the first embodiment corresponding properties.
A cam mechanism causes a purely translational motion of the third embodiment box-beam 71 when the beam support rollers 16 follow the initial portion of the support track curve centerlines 73 (embodiment motion between
A number of advantages are evident in the embodiments described above:
(a) Very high stiffness and strength to weight ratios of the closed configurations enable light weight embodiments to carry large environmental transverse loads, such as those induced by rain and wind.
(b) Embodiment seamless surfaces enable the closed embodiments to be weather tight and capable of forming static pressure boundaries.
(c) Air confined in the cells of the closed configurations enables natural insulation of transverse heat transfer in the embodiments.
(d) Embodiment construction is extremely easy with no requirements for use of specialized equipment.
(e) Embodiment installation and operation utilizes existing commercially available equipment.
A flexible unitary sandwich-like panel overhead door design has been disclosed. This design is simple in concept and construction, yet has many potential uses which take advantage of this design's unique capabilities:
Although the above discussion contains many specificities, these should not be construed as limiting the scope of the embodiments, but as merely providing illustrations of some of several possible applications. Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given.
