Floating reservoir cover tensioning system

A floating reservoir cover tensioning system that eliminates unsightly towers that are mounted on the upper surface of the surrounding containing walls of a reservoir. A plurality of tensioning assemblies are mounted in cases supported on the top surface of the surrounding containing wall of the reservoir at predetermined spaced intervals to assure that the tension forces are equally distributed. Each of the tensioning assemblies has a combined structure of a cable drum and a storage drum journaled on a bearing extending up from a mounting plate. A pair of laterally spaced spring motor drums are also journaled on their respective bearings extending up from the mounting plate. One end of a first coiled-band spring is secured to one of the spring motor drums and its opposite end is secured to the storage drum. A second coiled-band spring has its one end secured to the second motor drum and its other end secured to the storage drum. A plurality of cables each have their one end secured to one of the respective cable drums and their opposite ends secured to the peripheral edge of the skirt portion of a floating cover for a reservoir.

BACKGROUND OF THE INVENTION 
The invention relates to large liquid containers and more particularly to 
reservoirs having a floating cover assembly. 
Throughout the world the necessity for a pure water supply is essential to 
sustain the life and health of mankind. Many areas of the world have 
population concentrations where local water resources cannot support the 
demands placed on the limited supply. Through the ingenuity of engineers, 
construction of very complex water transport and storage systems have been 
successfully implemented to make remote water sources accessible to 
population centers hundreds of miles away from the water source. Increased 
demands for the limited water resources continue to challenge engineers 
for unique solutions to enhance water supplies. Drought weather patterns 
aggravate the situation where preserving and utilizing the precious 
resources have become of paramount importance to the government and the 
populous at large. 
In order to conserve water resources, many reservoirs are having floating 
cover assemblies installed to cut down on evaporation and contamination of 
the water in the reservoir. There is a great body of prior art with 
respect to floating reservoir covers and the advantages of and methods for 
imparting tension into the flexible membrane covers to make them function 
as desired. 
U.S. Pat. No. 3,815,367 teaches a method of imparting tension to the 
central portion of a floating cover using a plurality of weight towers 
around the outside of the reservoir. This patent describes what is 
commercially known as a "mechanically tensioned floating cover". U.S. Pat. 
No. 4,971,217 principally teaches the use of slip ring connections in the 
reservoir cover system design. This cover system could employ the 
tensioning system taught in this patent application. U.S. Pat. No. 
5,108,225 teaches the use of a mechanically tensioned floating cover in 
conjunction with an elevated wall reservoir. This cover system could also 
employ the tensioning system taught in this patent disclosure. 
It is important to note that the present state of the art in commercial 
practice of mechanically tensioned floating covers universally and 
exclusively utilize "weight towers" to provide the tensioning means. The 
use of floating covers for reservoirs has been around for approximately 25 
years. The weight towers extending up from the top surface of the 
surrounding containing wall of the reservoirs are found objectionable for 
both practical reasons and cosmetic reasons. They appear as a row of 
numerous four to fourteen foot high posts extending upwardly from the 
containing wall of the reservoir. Aesthetically, they are objectionable. 
The individual cost of the numerous towers that are laterally spaced from 
each other around the periphery of the surrounding containing wall is 
relatively costly. Added to this is the expense of installing these 
numerous weight towers. The weight of these towers is also a costly 
consideration when they have to be shipped to distant installation sites. 
It is an object of the invention to provide a novel floating reservoir 
cover tensioning system that eliminates the unsightly weight towers used 
in state of the art floating reservoir cover installations. 
It is also an object of the invention to provide a novel floating reservoir 
cover tensioning system that utilizes constant force springs mounted in a 
low profile case or housing for providing the required tension to the 
periphery of the floating reservoir cover. 
It is another object of the invention to provide a floating reservoir cover 
tensioning system whose tensioning assemblies are relatively inexpensive 
to install. 
It is a further object of the invention to provide a novel floating 
reservoir cover tensioning system whose tensioning assemblies are much 
smaller in size and weigh much less than existing prior art tensioning 
assemblies. 
It is an additional object of the invention to provide a novel floating 
reservoir cover tensioning system that is more economical to manufacture 
and market than existing floating reservoir cover tensioning systems. 
SUMMARY OF THE INVENTION 
The novel floating reservoir cover tensioning system utilizes flat strip 
reel springs on automatically retractable reels as the primary tension 
imparting means in place of weight towers such as are presently used. 
These reel springs are of the constant force spring variety. A constant 
force spring develops its resisting force by increments rather than 
cumulatively. Every constant force spring is produced to provide a 
specific force which is exerted through the entire extension of the 
spring. The force is constant as long as the radius remains constant. 
Constant force springs deliver more force per pound of material than 
gravity devices. 
Constant force springs have enormous expandability. Their final load is 
limited only by the length of the spring material. At all extensions, the 
load remains the same. The constant force springs provide a strong 
recoiling force. This force may result in a tendency on the part of the 
extended material to twist in its effort to regain preset curvature. To 
inhibit this curling, it is always advisable to engage the front end of 
the spring in a manner that will not permit turning axially about the line 
of force. The attachment member must not be free to rotate about that 
axis. 
The drum end and coiled body of the reel springs must be completely free to 
rotate. No torque load or friction load should be applied to the spool or 
shaft, as the extended portion must be taken up by the coil readily to 
maintain full tension. 
In the novel floating reservoir cover tensioning system the tensioning 
assembly are mounted around the perimeter of the reservoir. Optionally 
they are mounted in a protective weatherproof case or housing made of any 
appropriate material to keep the spring protected from rain and dirt. In 
this most basic form each tensioning assembly would have the free end of a 
cable extending directly out towards the respective points of connection 
on the flexible floating cover membrane. 
The height of the case or housing in which the constant force spring is 
mounted would normally be less than 8 inches high. This eliminates the 
unsightly weight towers such as are presently used in the industry. The 
low profile of the novel case or housing containing the constant force 
springs are very unobtrusive and barely noticeable. Aesthetically, they 
are a 1000% improvement. 
In addition to the aesthetic advantages, the new system eliminates the 
costly weight towers, their sheaves, and several bolts required to secure 
them. Not only is the cost of these components eliminated, the costliness 
of their having to be shipped to various installation sites has been 
dramatically decreased. The new profile cases or housings are much lighter 
in weight. This is a considerable advantage when considering the fact the 
housings for the constant force springs are located around the entire 
perimeter of the reservoir at intervals in the range of 3 to 30 feet. 
The tensioning assemblies each have a mounting plate having a length L2 in 
the range of 8-18 inches and a width W2 in the range of 3-10 inches. 
Laterally spaced from each other on the top surface of the mounting plate 
is a first spring motor drum and a second spring motor drum. Each is 
journaled on a bearing shaft extending up from the top surface from the 
mounting plate. 
Positioned between the two spring motor drums is a combination structure 
having a cable drum stacked on top of a storage drum and interconnected 
thereto so that they rotate as a single unit. This combination structure 
is also journaled on a bearing shaft extending up from the top surface of 
the mounting plate. 
A first coiled-band spring formed of a strip of metal has its rear end 
gripping the first spring motor drum so that it can be coiled thereon and 
its front end secured to the storage drum so it can be coiled thereon. A 
second coiled-band spring has its rear end gripping the second spring 
motor drum so it can be coiled thereon and its front end secured to the 
storage drum so that it can be coiled thereon. The length of the springs 
is L1 and L1 is in the range of 1-30 feet. The width of the springs is W1 
and W1 is in the range of 1-6 inches. 
A cable has its rear end wound on the cable drum with the free end passing 
through a cable guide structure and then having its front end secured to 
the skirt portion of the floating cover. 
As the level of the water beneath the floating cover recedes, the weight of 
the cover will pull the cable out of the tensioning assembly housing and 
this will cause the cable drum to rotate about its vertical axis. Since 
the storage drum rotates as a single unit with the cable drum, the first 
and second coiled-band springs will be drawn off of the respective spring 
motor drums and caused to coil on the storage drum. As the level of the 
water beneath the cover increases, the reverse action will cause the cable 
to be drawn back into the housing of the tensioning assemblies and the 
first and second coiled-band springs will be drawn onto their respective 
first and second spring motor drums.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The schematic view of an existing conventional and state of the art 
reservoir is illustrated in FIG. 1. Reservoir 10 has a periphery defined 
by the inner faces of a surrounding containing wall 12, commonly called a 
berm, the berm having a generally horizontal upper surface 13 serving as a 
walkway. Sloping inner and outer surfaces 15 and 16 extend downwardly from 
the walkway at angles shown. 
The inventor's novel floating reservoir cover tensioning system is 
illustrated in FIGS. 2-4. It is generally designated numeral 20 and it is 
installed on reservoir 22. Reservoir 22 has a concrete ring wall 24 
located on the horizontal upper surface of the reservoir and it extends 
around the entire periphery thereof. A concrete overflow and reservoir 
inflation structure 26 with a stairway is positioned along one of the 
inner sloping surfaces of the reservoir. Floating cover 28 is supported on 
the top surface of the water and it has a plurality of access hatches 30 
and a plurality of surface water cover drains 31. Floating cover 28 has a 
central portion 35 having a peripheral edge 36. Central portion 35 has at 
least 500 square feet of surface area. A skirt portion 38 surrounds 
central portion 35 and it has an inner peripheral edge 39 and an outer 
peripheral edge 40. Numerous cover tensioning stations 42 are positioned 
on the upper surface of the containing wall 12 of the reservoir. The cover 
tensioning stations 42 are separated from each other by a distance D1 and 
D1 is never greater than 30 feet. 
FIG. 3 is a top plan view of one of the tensioning assemblies 42 with its 
cover 43 removed. A first spring motor drum 44 has a Y1-axis and it is 
journaled on a bearing shaft 46 extending upwardly from mounting plate 48. 
A constant force spring 50 has its rear end gripp ing the first spring 
motor drum 44. A second spring motor drum 52 has a Y3-axis and it is 
journaled on a bearing shaft 54 extending upwardly from mounting plate 48. 
A storage drum 58 has a Y2-axis and it is mounted on a bearing shaft 60 
extending upwardly from mounting plate 48. A cable drum 62 is stacked on 
storage drum 58 and it is secured thereto so that they rotate as a single 
unit. A cable 66 has its one end secured to cable drum 62 and its free end 
passes through a cable guide 68 (such as an eye bolt) and is then secured 
to the floating cover. A stop member 69 limits the travel of cable 66 onto 
cable drum 62. The front end of constant force springs 50 and 55 are 
secured to the outer drum surface of storage drum 58.