Patent Application
20050102941
The present invention relates generally to expansion joints for building panels and more particularly to expansion joints for building panels such as concrete floor slabs that provide the necessary flexibility for expansion and contraction and at the same time, block fire and heat flow between adjacent panels.
It is generally understood that in building construction, it is necessary to provide expansion joints between abutting floor or wall panels to allow for expansion and contraction of the material under varying temperatures. In concrete construction, such joints typically comprise a strip of a relatively soft material interposed between the edges of abutting slabs of concrete when poured. Over time, the joint material tends to dry out and pull away from the opposed concrete surfaces. While this effect poses little problem in concrete slabs poured on grade, it is a matter of significant concern when the slabs constitute the floors of a multilevel structure. Not only would the joint material tend to separate from the slabs over time, it could even fall out completely during periods of extreme contraction. In either event, this would leave gaps between adjacent slabs that would act as chimneys in the event of a fire in the structure, thereby enabling the fire to rapidly spread to upper levels.
In one known form of expansion joint, described in U.S. Pat. No. 4,756,945, a blanket of non-combustible, heat-expansible material is folded over on itself to form a barrier strip and inserted between adjacent building panels. The strip, comprising inter alia, a combination of non-combustible fibrous material and heat expandable particles, is secured between the panels by backer rods pressed in on either side of the strip. Elastomeric sealing material is then added to cover the backer rods.
While the material described in the above-mentioned patent, manufactured and sold by Backer Rod Manufacturing, Inc. of Denver, Colo., under the name Ultra Block, has suitable heat-resistance and expansion characteristics for building applications, the manner disclosed in the patent for securing the material between building panels is relatively complex and suffers the disadvantage that the sealing rods and elastomer used to retain the material in place are subject to drying over time and dropping out.
In another type of expansion joint, manufactured by the Watson Bowman Acme Corp. of Amherst, N.Y. and marketed under the names Wabo Fire Flex and Wabo Flame Guard, heat-resistant material is formed into a U-shaped trough and secured between adjacent panels by sheet metal strips along the edges of each leg of the U. The material is otherwise unsupported or protected against accidental damage. A similar fire barrier is manufactured by MM Systems and sold under the name PYRO-FLEX.
The object of the present invention is to provide a fire-resistant joint for building construction that overcomes the disadvantages of prior art expedients.
In accordance with the invention, this object is achieved with a two-piece joint system comprising a strip of fire-resistant, flexible sheet material formed into a U-shaped trough or drape and an elongated mat of expandable fire-resistant mat retained within the drape. The edges of the flexible drape are bent outwardly to overlay the surfaces of the adjacent building panels and secured thereto by suitable fasteners. Little or no adhesives and no sealants are required to secure the joint in place and the impervious nature of the drape guards against the chimney effect. The savings in installation time and cost of the invention provides a further significant advantage over prior art systems.
The foregoing objects, features and advantages of the invention will become apparent from the following detailed description thereof, taken in conjunction with the appended drawings, in which:
Referring now to the drawings,
The joint structure 10 comprises a heat shield or drape 16 made of 2 mil (0.002 inch) thick impermeable stainless steel foil, formed into a longitudinally extending generally U-shaped trough, the opposite legs of which are indicated at 18 and 20. The legs 18, 20 are bent along their longitudinal edges at 90° to form flanges 18a and 20a. The drape 16 can be either metallic or woven ceramic. The drape 16 can also be woven from fire retardant fabric and should be flexible. When installed between slabs 12 and 14, the flanges overlay the upper surfaces of the adjacent slabs and bolts or other fasteners 22 secure the drape to the slabs. These fasteners may also serve to secure rails of a raised floor system installed over the slabs.
Between legs 18 and 20 of the U-shaped drape 16 is inserted an elongated mat 24 of expandable fire resistant material, such as the Ultra Block discussed above. The material is compressible at nominal (room) temperatures and is partially compressed when inserted between the legs 18, 20 of the drape, as shown in
As seen in the drawings, a space is left between the bottom of mat 24 and the curved bottom of drape 16. This allows the drape to flex without impediment during expansion and contraction of the joint. A small amount of adhesive may be applied to secure the mat to the drape after the mat is inserted.
The stainless steel foil drape 16 is impermeable to gases and thus forms an impenetrable fire and smoke barrier between the adjacent slabs. This prevents the occurrence of the so-called chimney effect, which would otherwise enable heat and fire to rise up through the floor and enter the space above the slabs. This increases the fire rating and safety of the structure and aids in compliance with Underwriters Laboratory standards.
It will be seen that the expansion joint of the invention is readily adaptable to different slab thicknesses and separation, because of the flexibility of the foil drape and the compressibility of the mat material. Moreover, the joint is assembled and installed on site, with minimal off-site preparation required.
Where the nominal separation between slabs is greater than 3 inches, it may be desirable to supplement the stiffness and fire resistance of the drape. This may be accomplished, as illustrated in
Although the invention has been described above as applied to horizontal concrete slabs in a building structure, it will be apparent that it has equal utility between vertical wall panels of a building, whether such panels are concrete slabs or wallboard-covered framing.
Moreover, while the heat and fire resistance characteristics of the inventions have been discussed above, it will be realized that the enhanced flexibility of the inventive expansion joint enables it to retain its integrity when the adjacent panels are moved as a result of seismic activity, as well. This is yet another advantage of the invention not found in prior art devices.
Although the invention has been described above in connection with its preferred embodiments, it will be appreciated that other embodiments and variations of the invention will occur to those skilled in the art. Accordingly, it is understood that the scope of the invention is to be limited only as set forth in the appended claims.
