Static structures (e.g. – buildings) – Enclosure including flaccid nonmetallic or foraminous surfacing
Reexamination Certificate
1998-11-10
2001-07-17
Safavi, Michael (Department: 3635)
Static structures (e.g., buildings)
Enclosure including flaccid nonmetallic or foraminous surfacing
C052S066000
Reexamination Certificate
active
06260308
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to greenhouses. More specifically, the present invention relates to devices that allow the user to cover and uncover the top of a greenhouse at will.
2. Discussion of Background
A greenhouse is a lightweight enclosure that provides covering for plants and seedlings, whether planted in flowerpots or trays or in the earth enclosed by the greenhouse. Typically, a greenhouse comprises a framework and a covering. The framework can be made of metal, wood or plastic; and the covering can be made of glass, flexible plastic sheeting or panels. Invariably, the covering is light-transmitting although not necessarily light-transparent and is most often “fixed”; that is, it remains permanently in place and is not easily openable or removable. For ventilation, greenhouse will often have louvers, perhaps, with assisted by large fans, on the ends.
The purpose of the greenhouse is to protect the plants and seedlings from the extremes of the environment: excessive heat or cold, excessive amounts of rain or “hard” rains. However, greenhouses can also cause problems for growing plants. They trap heat, for example. Also, because plants naturally grow toward the light—a tendency known as phototropism —and because greenhouse coverings invariably attenuate the light, plants in greenhouses can tend to be spindly.
Ideally, greenhouses should have a cover that can be opened when the weather is clear and warm, and that can be closed on nights when the temperature is expected to drop to unacceptably low levels, or on days when it will rain excessively or rain hard, or when too much heat has built up in the greenhouse. Such a cover would not only help to regulate the temperature within the greenhouse, but would reduce watering costs and make plants healthier, thicker and fuller.
There are greenhouses that can be opened up or uncovered. Theoretically, greenhouses can have windows similar to those in homes. However, it is simply not practical to incorporate ordinary windows into greenhouse designs. First, a system for uncovering a greenhouse must be simple structurally so that it is not cost-prohibitive. It must be easy to use so that greenhouses can be uncovered and covered quickly and without special training. Furthermore, commercial greenhouses often cover several acres of ground. If the closure mechanism is too complicated or slow, operating it may require extensive manpower or time or both. Finally, if the covering for the greenhouse is made of plastic, the covering mechanism must accommodate the characteristics of plastic. These characteristics include (
1
) a tendency to “bathtub” or collect water where the plastic sags, (
2
) the tendency to catch the wind and (
3
) limited structural strength.
However, the advantages of a system that can meet this requirement are considerable. An inexpensive, easy to use and reliable system for covering and uncovering the greenhouse can make growing of plants much easier and result in higher quality plants, better yields and lower costs. Moreover, such a system is not limited to use as greenhouses. Temporary structures for out-of-door events can also benefit from such a mechanism.
There remains a need for a covering mechanism for greenhouses that operates easily and simply and does not add undue cost to the overall cost of greenhouse construction.
SUMMARY OF THE INVENTION
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. The inner edges of the two sheets are firmly attached to the tension shaft.
A first leading edge is also firmly attached by a first clip to the side of the greenhouse and a second leading edge is attached to a second clip. The second clip is not attached to the frame; rather it is connected by the first set of cables to the central shaft at the top center of the greenhouse framing. As the central shaft turns, these cables pull the second clip and second leading edge of each panel toward the top center of the greenhouse, unrolling the covering material from the tension shafts as the tension shafts themselves roll up from the sides to the top of the greenhouse. By the time the second leading edge of each panel reaches the top center of the greenhouse, each tension shaft has reached a position approximately halfway between the top center and the sides of the greenhouse. Tension on the covering material is applied and maintained by the second set of cables and the counter weights. As the second set of cables is unwound from the driving shaft, it is wound onto the tension drums. The springs automatically take up the slack in the second cable set. When the greenhouse is to be uncovered, the process is simply reversed.
Keeping the covering under tension using opposing sets of cables and the counter weights is a very important feature of the present invention. By maintaining tension, not only is sagging of the covering avoided with the attendant problems of rainwater collection, but also the cover winds onto and unwinds from the tension shafts more smoothly and uniformly so that the covering does not bunch or catch.
Having two panels that move from the sides to the top center to cover the greenhouse is another important feature of the present invention. The easiest way to vent the greenhouse is through the top center, that being the highest point. Partially uncovering the greenhouse may be sufficient to ventilate it, a feature that may be important, for example, during a long rain on a warm day when the need for ventilation competes with the need for protection from the excessive rain, or when ventilation is needed, but the outside temperature is much lower than the inside temperature.
Using one central shaft to operate two symmetric panels is another feature of the present invention, especially since the driving shaft turns with the central shaft. This feature simplifies the control requirements and power requirements for the present invention. Essentially one motor rotates both shafts at the same time; therefore, one motor (or hand crank) is needed to op
Jaderloon Company INC
Mann Michael A.
Nexsen Pruet Jacobs & Pollard
Safavi Michael
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