Covering mechanism for a greenhouse

DETAILED DESCRIPTION According to its major aspects and briefly stated, the present invention is a mechanism for covering a greenhouse.
The mechanism allows the user to pull a cover over the top of the greenhouse frame and to retract the cover from the top of the greenhouse frame while keeping tension on the covering material so that the problems of the prior art mechanisms are avoided.
Putting its operation simply, in the present covering mechanism, a rotating central shaft unrolls two flexible covers from driving shafts onto the top of the greenhouse, pulling them up to the top center of the greenhouse from its sides.
Each cover is pulled using two sets of cables, one set pulling the covers and the other set operating in an opposing direction to apply tension to the covers during the covering and uncovering process.
A counter weight or spring achored to the floor is used with the second set of cables to assure that adequate tension is applied regardless of the direction the cover is moving.
The cables of the first set wind around the central shaft.
The cables of the second set wind around a driving shaft mounted to the end of the central shaft so as to be coaxial with it.
The first set of cables pulls the cover toward the top center of the greenhouse when winding around the central shaft.
The cables of the second set wind around the driving shaft and the tension drums.
When the cables of the first set is being wound up, the cables of the second set are unwinding from the driving shafts and winding onto the tension drums.
The springs are applied to the second of set cables to tension them, counter to that applied by the first set of cables.
More specifically, two sheets of flexible covering material are wrapped about a tension shaft simultaneously, one tension shaft for each side of the top of the greenhouse, so that, when the tension shafts are fully wound, the inner and outer edges of the sheets are adjacent to each other and the outer edges are the "leading" edges, that is, they are the first parts of the covering material to be freed from the tension shaft when it is unrolled