US Patent 7510230 Dust-proof end closure for contractible canopy

A foldable canopy cover can be automatically extended over the open top of a container. The canopy is supported by a series of arcuate booms transversally spanning the top of the container. Each boom is secured at opposite ends to a pair of train members riding on rails running along the lateral upper edges of the container. At the end of the covering movement, as the leading edge of the canopy approaches the end of the container, it is brought down flush with the container rim by contact between a cam ramp associated with the container and a roller pin on a lever supporting the leading edge of the canopy, in order to tightly close the open top.