To make retractable a very large roof so as to move it completely off the space it covers presents new challenges. Such a roof may be a barrel vaulted roof hundreds of feet long, or a pitched roof hundreds of feet long, or even a flat roof hundreds of feet long. The object is to move such a roof as one unit. The object also is to move the flat roof in sections.
The state of the art today shows no quick answer to these requirements. There are smaller retractable roofs often made of plastic or glass used over swimming pools and garden courts. There are unit skylights of various shapes either in glass or plastic that are made to slide. There are custom roofs in either glass, plastic, or other material. None of these roofs show how to move a large barrel vaulted roof, a pitched roof, or a flat roof in the large size required, completely on and off the opening they cover.
When the roofs become very large, one of the new issues is the temperature expansion of the retractable roof versus the supporting structure. In new stadiums this is sometimes accounted for by partially articulated wheel trucks. On smaller roofs this is sometimes accounted for by expansion and contraction of the retractable roof frame taken by sideway movement of the wheels on the supporting rails of the roof. In this invention the effort is not to mitigate the expansion and contraction movement of the roof on the wheels, but to create a system where the rail for the roof supporting wheels moves closely the same as the roof from temperature expansion and contraction, so no thermal expansion and retraction accommodating means are needed at all between the roof and the wheels. This is done by supporting the rail on an intermediate frame which spans the area being covered so that the rail and the support therefore will expand and contract as one. To manage this, the intermediate frame is supported on slide bearings resting on columns, or possibly walls or another beam structure, so that it is free to move in unison with the roof, both exposed to similar temperatures. In this manner the roof and wheels see limited to small differential movement so no measures such as articulated frames or rollers or even slide bearings are needed between the roof and the wheels.
This alone does not assure that the roof can be moved evenly. The retractable frame that is moved must be very rigid. Rigidity in panelized roofs on stadiums extends only to the individual panels. This invention moves the entire roof as a monolithic piece and therefore requires bracing of the entire roof. This is done very simply with X bracing or other forms of bracing in the retractable roof.
Thirdly to move a large monolithic roof evenly requires that the drive means, the wheels with attached motors or a cable and winch system, the two most common, must work evenly together. Other stadium roofs use various means of electro mechanical controls to assure one side moves the same as the opposite side so the roof moves evenly. Some stadiums use controls that measure the exact location of the sliding wheels at all times and correct motor speeds to adjust continuously so that the roof runs evenly. In other words so that one side reaches the end point at the same time as the other. Although this could be done with the roof in this invention, this invention uses X bracing in a horizontal frame supporting the roof to transfer differential traction forces directly between the wheels and motors which drive the roof. Direct transfer of traction forces evens out the movement of all the motors and wheels contributing to an even parallel movement of the roof. This invention also uses motors on all wheels. At the same time redundancy is achieved. Should one motor fail, the loss will be taken up by the others.
It is these ideas brought together in an artful and engineered manner that result in a smooth operating very large retractable roof to be used on a mall or other large area, which has never been done in this or a similar manner.
The following drawings together with the detailed description will describe this further.