IMPROVED WATER STORAGE TANK

Abstract: Liquid storage tank (10) for providing a liquid for pressure in such a way that pressurized air will not be absorbed by the liquid. According to one embodiment of this invention, the pressurized storage tank (10) of this invention having side walls (12) and an end wall (14) uses a plunger or a plate (24) having a seal (26) which is biased to move within the tank as water or liquid is forced into the tank or withdrawn from the tank. According to this embodiment, springs (38, 40, 42) may be positioned in different arrangements and used to provide the bias that maintains the water or liquid under pressure. Still other embodiments use mass (68) or weight while still others use power actuated means (56) or air pressure for providing the necessary bias. In other embodiments of the invention, the tank may include a seal and/or a collapsable liner (66) to prevent any of the liquid from passing the plunger or piston (24). The addition of a collapsable liner (66) is especially useful if the liquid to be maintained under pressure is corrosive.

Description: Description Improved Water Storage Tank Technical Field The present invention relates to pressurized liquid storage tanks in general and more particularly to liquid storage tanks which use a biased plunger or means other than air pressure to maintain the liquid under the desired pressure. Background Art Water storage tanks have, of course, been around for eons, including for example the simple gravity type, wherein rain water collected from the eaves of a roof is stored in a tank or cister 'in the attic 10 and then provided to the user at a lower level. Ho e er, such a technique is not suitable for water obtained from a well unless the water is first pumped to a level higher than the using facility. Since a huge or tall water tower is not always desirable, :3 other techniques of storing water so that it would be available for use throughout a building, were found to be necessary. To this end, water is often stored under pressure. To obtain the desired pressure, early water tanks were simply air tight tanks which ( - ) included enclosed air under pressure as well as water. This pressurized tank is connected directly to the water system. Therefore, according to this system, the tank is first pressurized with air so that as water is forced by the well pump into the *■ ' tank, the air would be further compressed. The pump continues to force water into the tank displacing the -2- air, until the compressed air in the tank itself exerts as great a force as is provided by the pump. When water is withdrawn from the tank the water leaves the tank under pressure until the water level **' is reduced to a level, where the air pressure against the water within the tank is reduced to a level sufficient to activate a pressure switch which in turn activates the water pump. Such pressure tanks have significant disadvantages in that the compressed 10 air within the tank will be absorbed by the water. This results in a condition where very little air can be withdrawn from the tank before the pressure is dropped to a point whereby the pump must again be activated. Thus, after a period of time and because • *- 5 the air is absorbed by the liquid, little air remains to be compressed, which causes continuous cycling of the pump. This in turn results in heavy wear and eventual malfunction of the pump. In addition, even under the best of conditions the actual amount of 0 water that can be withdrawn from this type pressure tank constitutes a very small percentage of the actual tank volume. For example, a 42 gallon capacity tank properly charged with air will only hold approximately 20 gallons of water which in turn can be drawn down 5 only about 6 gallons before the pump will reactivate. To overcome some of the deficiencies of this type air pressure tank, improvements which use a bladder or diaphram within the tank to separate the air from the liquid are available. For example, by 0 providing two compartments, one for air and one for water, which compartments are separated by a flexible diaphram the mixing of air and water can be avoided. For example, see U. S. Patent 2,594,833 issued to S. M. White on April 29, 1952 and U. S. Patent 3,346,014 issued to C. Jacuzzi on October 10, 1967. Each of these patents, show the two compartment tanks using a flexible diaphram between the two tanks to prevent the mixing of air and water. The White patent further includes a perforated inflexible metal separator to prevent over stressing of the flexible diaphram to prevent early failure. In a similar manner, the Jacuzzi patent includes a bellows type diaphram so that it is not stretched. However, even this type of diaphram still requires flexing during operation. Unlike the present invention, both*of these patents rely completely on the use of air pressure for opera¬ tion. However, U. S. Patent 3,487,855 issued to J. W. Lautenberger on January 6, 1970 discloses a pulsation dampner for controlling the pulsating or water hammer effect of a liquid system under pressure by means of a piston device which receives pressure from the system on both sides of the piston. However, according to this patent, one side is provided with smaller tubing. Therefore, it is an object of the present invention to provide a heavy duty self-contained pressure system suitable for substantially all liquid systems , and which does not permit compressed air to be absorbed by the stored liquid. -4- It is a further object of this invention to provide a pressurized liquid tank which requires significantly less space than tanks available heretofore. It is yet another object of the present invention to provide a pressurized liquid tank which allows a high level of draw down before the pressure in the tank is reduced and has to be replenished with additional liquid. Disclosure of the Invention Other objects and advantages will in part be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides an improved pressurized storage tank. Briefly, the pressurized tank of this invention comprises a tank having an end wall and side walls which define a liquid storage container. The liquid storage container has a selected cross-section which extends between a first portion and a farther portion along a travel axis which is perpendicular to and extends the length of the cross-section. The tank further includes means, such as a "T fitting" for receiving and discharging the liquid, which T-fitting is connected to the end wall. A plunger having ah outside shape corresponding to the cross-section of the tank maintains a sliding fit of the plunger within the liquid storage container. The plunger moves along the travel axis between the first and farther portions so that the volume of the container available for liquid storage is reduced as the plunger is moved from said first to said farther portion. The system further includes a biasing means fox rging the plunger toward the farther portion of the tank thereby maintaining pressure on the liquid. The apparatus may also, of course, include a seal between the plunger and the tank walls to prevent liquid from moving pass the plunger. In still another embodiment, a collapsable liner is included within the liquid storage volume to also provide protection of the system from the liquid. Such protection would be extremely valuable if the liquid itself was corrosive, The biasing means used to move the plunger and maintain- the liquid under pressure may be a massive weight which sets on top of the liquid to provide pressure or alternatively air pressure or various type of springs arranged such that the liquid is maintained under pressure may be used. Still other techniques include power actuated devices such as motor driven racks and/or hydraulic systems for maintaining the liquid under pressure. Yet another technique comprises the use of an electro-magnet located within the tank itself for drawing the plunger to itself thereby reducing the liquid storage area. A particularly effective system is a combination of air pressure with either weight, springs, or an electro-magnet providing the necessary bias. Brief Description of the Drawings Figure 1 is a cross-sectional view of a tank of this invention using compression springs located between an end member of the tank and the movable plunger for mai n taining pressure on the liquid therein. Figure 2 is a ross-sectional view of a tank of this invention shewing compression springs located 32 -6- between a floor support member and the plunger for maintaining the liquid in the tank under pressure. Figure 3 shows a cross-sectional view of another embodiment of this invention wherein tension springs •5 are located within the liquid container itself for maintaining the liquid under pressure. Figure 4 is a cross-section of the tank of this invention wherein the plunger maintains pressure on the liquid contained in the storage volume by means 10 of power actuators such as hydraulic cylinders and/or rack and pinion drives. » Figure 5 shows a cross-section of the tank of the present invention wherein the plunger is maintained under a heavy weight to provide the pressurization to 15 the liquid contained therein. Figures 6A and 6B show a cross-section of the tank of the present invention wherein an electro¬ magnet is used to attract the plunger thereby providing the pressure to the liquid contained therein. Best Mode for Carrv —inσ-* Out the Invention 20 Referring now to Figure 1, there is shown generally at 10 an embodiment of the system of the present invention having a tank or liquid container 11 formed by side walls 12 and an end wall 14. It will be appreciated that although any cross-section could be 25 used, it may be more advantageous to use a cylindrical cross-section for ease of manufacture and assembly. Connected to end wall 14 is a receiving and discharging means which as shown may be simply be a "T" shaped connector which receives liquid from a pump or well *-*° (not shown) connected to end 18, which in turn provides liquid to a using system by means of pipe 20. The leg 22 of the "T" opens into the tank or container 11 wherein the liquid is to be stored. In the figure as shown, the side walls 12 may be mounted to the end wall 14 in any suitable manner such as be welding, bonding, or other means such that they are liquid tight. However, it will also be appreciated that the end wall could itself be molded or formed as a single unit with the side walls. This is especially true in the case of a tank having a cylindrical cross-section area. Thus, it can be seen that the side walls 12 and the end wall 14 provide a tank or liquid container 11, but which without more would not be under pressure. Therefore, the pressure of the liquid is provided by means of a plate or plunger 24, whLch plate or plunger has a cross-section corresponding substantially to the cross-section defined by the side walls 12 and moves along a travel axis 25. Also included is a seal 26 which is located between the plunger 24 and the side walls 12. It will be appreciated that the seal 26 could be made of any suitable flexible material such as nylone, polyethelene, leather, rubber or the like. In the embodiment shown, a top or end member 28 is located at the end of the walls 12 and opposite the end wall 14. For purposes of strength and support, and to withstand the pressure which may be required by -che biasing means to be discussed hereinafter, the present: embodiment shows straps 30 and 32 which may be included to securely maintain end member 28 in the proper location. According to certain embodiments of this invention, a complete air tight seal is not required of end member 28, and to assure the free movement of the plunger in the event a cap is used, there is also shown an air control device 34 to allow the free movement of air into the air space 36. However, as will be discussed hereinafter, other embodiments operate in conjunction with compressed air as the biasing means. In such embodiments, air control device 34 may operate as a valve for pro- viding pressurized air. Also included in this embodiment are compression springs 33, 40 and 42 for biasing the plate 24 against the liquid contained in tank or container 11. A plunger and a guide shaft 44 and 45 respectively may be used to maintain the plunger in a substantially horizontal location. It will be appreciated, that although springs 38, 40, and 42 are shown as helical compression springs, many suitable springs including leaf springs could be used. Also, of course, rather than three springs a variety of sizes of numbers of springs would also be appropriate. The amount of spring force required will, of course, depend upon the desired pressure of the liquid within the liquid container or tank 11. Also as will be discussed hereinafter, compressed air located in chamber or air space 36 may operate in combination with springs 38, 40 and 42 as the bias to provide the necessary pressure to the liquid in the tank or chamber 11. Thus, in operation the pump 41 would typically pump water from a well through pipe 13 into the tank or container 11. The plunger 24 in its initial state would be in a low position such as shown by dotted lines at 24A. As more and more water was introduced into the tank 11, plunger 24 would move along travel axis 25 to the solid line position at the top of the tank at which point a pressure switch 43 would sense that the liquid in the system was at the desired pressure. Thus, the pump would cut off and no further liσuid would be introduced into the tank 11. Upon need, water or liquid would be withdrawn from tank 11 through pipe 20 and the liquid would be maintained under pressure by the plunger 24 responsive to the springs 38, 40, and 42. As liquid was withdrawn plunger 24 would move downward along travel axis 25. Referring now to Figure 2, there is shown another embodiment of the present invention. Components shown in Figure 2 which are similar to those in Figure 1, previously discussed, maintain the same reference numbers. As shown, Figure 2 is similar to Figure 1 except that the tank is inverted. That is, the receiving and discharging means 16 is at the top of the tank and plunger 24 is at the bottom of the tank. The side walls 12 are securely mounted to a floor support member 46 by means of bolts or studs such as shown at 47 and 48. In this embodiment, the springs 38, 40, and 42 are between floor support member 44 and plate or plunger 24. Thus, as liquid is pumped into tank 11 through receiving/discharging means 16, springs 38, 40, and 42 are compressed. As OMPI liquid is drawn for service, springs 38, 40, and 42 urge the plunger 24 along travel axis 25 towards the end plate 14 to maintain the liquid under pressure. Again as was mentioned with respect to Figure 1 and 5 as will be discussed, hereinafter, compressed air located in air space 36 could be used in combination with springs 38, 40 and 42 to provide the necessary biasing. Referring now to Figure 3, there is shown still 10 another embodiment of the present invention. As can further be seen in this embodiment, tension springs such as shown at ' 50 and 52 and located within the tank or container 11, tend to hold the plunger 24 in a lowermost position. As can be seen in this example, 15 however, plunger 24 may be domed or saucer shaped. » Such a shape, helps maintain contact of the plate 24 with sidewalls 12. As shown, leaf type springs are used at 50 and 52, but it will be appreciated, of course, that helical tension springs could be used, 20 Again, of course, compressed air could be provided in air space 11 to help provide the necessary biasing. Still another embodiment is shown in Figure 4. According to the embodiment of Figure 4, the primary biasing means rather than being springs could be a 25. hydraulic cylinder 56 which is shown being powered by a hydraulic pump 58. Alternatively, another power actuating source could be simply a rack member 60 attached to plate 24. The rack 60 is driven by means of an electrical motor 62 and gear box 64. Thus, 0 according to this embodiment, the desired pressure can be maintained by a power actuating device. The embodiment of Figure 4 also shows the use of a collapsable liner 66 for maintaining the liquid in the tank 11. The use of a collapsable liner is especially desirable if the liquid is corrosive to help prevent any contamination or leakage. Referring to Figure 5, there is shown a simple embodiment of the present invention wherein the plunger 24 sliding within side walls 12 uses as its biasing means a mass or weight 68 to maintain the desired pressure on the liquid in tank 11. The weight 68 can be of any suitable heavy material, but is preferably made of an inexpensive material such as sand, concrete, or the like. Also as shown in Figure 5, leg 22 of receiving/discharging means 16 which opens into tank 11 may also include a rubber stop 70 upon which plunger 24 may come to rest if sufficient liσuid is withdrawn to allow the plunger to move to that extent. Also shown are perforations 72 and 74 to allow liquid to move in and out of means 16. This embodiment is especially suitable for working in combination with compressed air in space 36 to provide the necessary biasing. Referring now to the cross-sectional view of Figure 6A and the perspective cut away view of 63, there is shown still another embodiment for obtaining the desired biasing means. According to this embodiment, electro-magnet 76 is located in the bottom of the tank 11 against end plate 14. In this embodiment tank walls 12, and end plate 14 are preferably made -12- of a nonmagnetic material; whereas, plunger 24 is made of a magnetic material such that the electro¬ magnet 76 attracts plunger 24 thereby providing the necessary pressure to the liquid contained in container 11. Since the pressure provided by electro-magnet 76 will be inverse with respect to the distance of the plunger, it may also be desirable to include some other biasing means such as springs or compressed air in space 36 to provide the pressure when plunger 24 is at its extreme travel away from end plate 14. Thus, it will be appreciated that there have been described various embodiments of the present invention for providing necessary force or biasing means to maintain the liquid under pressure. However, as has been mentioned, compressed air may also be used either by itself or in combination with the previous described biasing means to obtain the necessary liquid pressure. In order that compressed air may be used, it is ncessary, of course, that the air space 36 be air tight. Referring again to Figure 5, it will be appreciated that to maintain compressed air in space 36, end member 28 must be joined to side walls 12 with an air tight joint. This can, of course, be accomplished in any suitable manner, including a seal 78 and series of bolts such as shown at 80 and 82 which joins flanges S4 and 86. End member 28 could also simply be welded to side wails 12, but such construction would complicate repairs, etc. It is believed that even if compressed air is used in this manner along with another type of biasing means the absorption of air by the liquid is prevented even if a liner 66 is not used. This is because the pressure of the liquid which is under pressure due to both the compressed air and the weight is greater than the air pressure alone. Thus, any air which possibly seeped around seal 26 would be at less pressure than the liquid and therefore the air would not be absorbed by the liquid. It will further be appreciated that in the embodiment, the tank may be made of any suitable material including steel or metal or in some cases fiberglass or other materials. Thus, although the present invention has been described with respect to specific embodiments it is not intended that such specific references be considered as limitations of the scope of the invention except insofar as set forth in the following claims.

Claims: Clai s 1. A liquid storage container for maintaining liquid contained therein at a pressure within a selected range of pressures comprising: a tank comprising an end wall and side walls defining a liquid storage container, said liquid storage container having a selected cross-section extending between a first and farther portion, and a travel axis perpendicular to and extending the length of said selected cross-section,- said tank further including liquid receiving and discharging means connected to said end wall; a plunger having an outside shape corresponding to said selected cross-section for providing a sliding fit of said plunger within said liquid storage container along said travel axis and between said first and farther portions such -that the volume of said liquid storage container is reduced as said plunger moves biasing means for urging said plunger towards said farther portion. 2. A liquid delivery system for maintaining liquids under pressure comprising the storage container of Claim 1 and further including a pump to force liquid into said tank through said liquid receiving and discharging means such that said plunger is moved against said biasing means from said farther portion towards said first portion, and a pressure switch to turn said pump on and off as the pressure of sai liquid in said tank varies between selected pressure limits. 3. The apparatus of Claims 1 or 2 and further including a seal between said plunger and said tank walls to prevent a liσuid contained with said storage container from moving past said plunger. 4. The apparatus of Claims 1 or 2 and further including a collapsable liquid impervious liner located within the liquid storage container- and connected to said receiving and discharging means such that any liquid provided by said receiving means is contained within said liner. 5. The apparatus of Claims 1 or 2 and further including an end member secured to said side walls to provide an air tight seal therebetween, and wherein compressed air is provided between said end member and said plunger such that said compressed ' air provides said biasing means. 6. The apparatus of Claims 1 or 2 wherein said biasing means comprises a spring connected to urge said plunger toward said farther portion. 7. The apparatus of Claim 6 and further including an end member fixedly attacned to said tank opposite said end wall and outside of said liquid storage container, and wherein said spring is a compression spring located between said end member and said plunger. 3. The apparatus of Claim 7 wherein said end member is attached to said side walls to provide an air tight seal therebetween, and compressed air is provided between said end member and said plunger such that said compressed air works in conjunction with said springs as said biasing means. 9. The apparatus of Claim 6 wherein said spring is a tension spring connected between said end wall and said plunger inside said liquid storage container. 10. The apparatus of Claim 6 wherein said end member is a support floor. 11. The apparatus of Claim 9 and further including an end member secured to said side walls to provide an air tight seal therebetween, and wherein compressed air is provided between said end member and said plunger such that said compressed air works in conjunction with said springs as said biasing means. 12. The apparatus of Claims 1 or 2 wherein said tank is oriented such that said plunger is the top most portion of said liquid containing tank and said biasing means is a mass of material for providing weight on top of a liquid in said liquid containing tan . 13. The apparatus of Claim 12 and further including an end member secured to said side wails to provide an air tight seal therebetween, and wherein compressed air is provided between said end member and said plunger such that said compressed air works in conjunction with said weight as said biasing means. 14. The apparatus of Claims 1 or 2 and further including an end member fixedly attached to said tank opposite said end wall and outside of said liquid storage container, and said biasing means being a -* ■* wer actuating means connected between said end ...ember a * - ** ' said plunger. 3*.tfλ ' A " • 1 15. The apparatus of Claim 14 wherein said end member is attached to said side walls to provide an air tight seal therebetween, and compressed air is provided between said end member and said plunger such that said compressed air works in conjunction with said power actuating means as said biasing means. 16. The apparatus of Claims 1 or 2 wherein said tank walls are made of a non-magnetic material and said plunger is made of a magnetic material, and further including an electro-magnet within said liσuid storage container and adjacent said end wall such that when the said electro-magnet is activated said plunger is attracted toward said* electro-magnet. 17. The apparatus of Claim 16 and further including an end member secured to said side walls to provide an air tight seal therebetween, and wherein compressed air is provided between said end member ana said plunger such that said compressed air works in conjunction with said electro-magnet as said biasing means.

Inventors: WILKINSON P
Applicants: WILKINSON P
Application year: 1981
Main classification: F04B49
IPC codes: F04B49