Raised floors are commonly used to create a space between a sub-floor and the normal working environment of a room. The sub-floor is the surface that would serve as the floor of a room before a raised floor has been installed. The raised floor creates a new floor surface that is somewhat higher than the sub-floor. The space between the sub-floor and the raised floor is used to hold electrical wiring and fiber optic cables, to contain an air plenum chase, and more generally to contain anything that must be in a room but is more safely or conveniently enclosed in an area apart from the main area of the room.
Early manufacturers of raised floors attempted to meet the needs of the early computer industry, such as providing large amounts of space for cabling and effectively dissipating heat generated by the computers. One early cooling method was simply to cut holes in solid raised floor panels and place grilles over these holes. This method proved to be unsatisfactory as the grilles did not allow adequate air flow between the sub-floor area and the external room. Furthermore, the grilles could not support adequate loads and the rough surface of the grilles interfered with the smooth operation of wheeled devices, such as moving carts, that must frequently be rolled across a floor.
An advance in raised floor design occurred with the introduction of perforated panels. Perforated panels are created by placing numerous small holes in solid panels. Perforated panels allow better ventilation than solid panels and provide a smoother working surface and greater strength than grilles. A marked disadvantage of perforated panels is that they are not as strong as solid panels. Notably, newer applications of raised floors require strengths that standard perforated panels cannot provide.
A common method of constructing a raised floor panel is to construct the panel from several layers. A bottom pan is filled with a supporting layer made of wood, cement, resin, or other material, or the bottom pan may be left hollow. A top sheet covers the bottom pan and the supporting layer and forms the working floor surface. While such a design is stronger, quieter, and more cost efficient than a conventional single piece raised floor panel, designs using a bottom pan still have not achieved strengths necessary for some applications. Further, such designs tend to be overly physically heavy. Also, even though panel strength is improved by a bottom pan design, the perforated panels used with these designs must be structurally weakened in order to provide acceptable ventilation through the raised floor.
Several. variations of the bottom panel design have been developed. At least one manufacturer of raised floors has improved the strength of raised floors by running steel reinforcement beams beneath the perforated panels. However, raised floors constructed with this technique are still not strong enough to support the loads required by more recent applications. Furthermore, support beams decrease ventilation by blocking the perforations that lie over the beams. U.S. Pat. No. 5,115,621 of Kobayashi describes a panel including a bottom pan and a top sheet with discrete supporting props formed into either the bottom pan or the top sheet, with the top sheet and bottom panel crimped together. U.S. Pat. No. 4,319,520 of Lanting, et al. describes a panel including an articulated frame that surrounds an interfitted grid structure where notches in each grid member fit into notches in the perpendicular members. Lanting also describes a damper system where damping plates are attached to the frame of the floor panel. However, such damping plates cannot be adjusted when utilizing a center support pedestal.
The strength of a raised floor is affected by the method in which the raised floor panels are supported as well as by the intrinsic strength of the raised floor panels. The usual method to support a raised floor is to place a support pedestal under each corner of the floor panels. Innovations in raised floor support structures have focused on refinements in corner support systems. For example, U.K. Patent Application No. 2-267-720-A of Huang describes a system where the corner support pedestals are connected to one another by a grid. Another support system, described in U.S. Pat. No. 5,048,242 of Cline, includes stringers attached between support pedestals. Again, the pedestals support the panels at their corners, and additional support is achieved at the edges of the panels by the stringers. The panel centers, however, remain unsupported.
A desirable raised floor could support loads several times greater than present raised floors support. Additionally, the ventilation characteristics of the raised floors should be easily adjustable. Finally, it would be useful if the user could readily adjust the height of the raised floor and the angle between the sub-floor and the work surface. This would allow ramps to be created on the raised floor where none exist on the sub-floor, or for a flat surface to be created on a raised floor above a ramp on the sub-floor.