US1562693A - Cistern - Google Patents

Description

R. E. DILL NOV. 24, 1925.

CISTERN Filed March 12. 1923 i f r: l

EICHAFED E. DILL. INVENTOR.

" [ATTORNEY Patented Nov. 24, 1925.

UNITED STATES RICHARD E. DILL, OF ALEXANDRIA, NEBRASKA.

CISTERN.

Application filed. March 12, 1923. Serial No. 624,449.

To all whom it may concern.

Be it known that I, RICHARD E. DiLL, a citizen of the United States, residing at Alexandria, in the county of Thayer and State of Nebraska, have invented certain new and useful Improvements in Cisterns, of which the following is a specification.

My invention relates to cisterns, and it has particular reference to a cistern which is specially adapted for use on farms and suburban places to furnish a constant supply of water for the home and for the barnyard.

Certain conditions affecting water supply systems are common to a large portion of the entire Mississippi V alley, and these conditions must be considered in designing a successful system of this kind. Nearly all farms and suburban homes in the middle west include one or more windmills as a part of their equipment. While the farm is largely dependent on the windmill for the power for raising the water, this power fluctuates and frequently does not function for short periods with the result that the owner must pump the water by hand or must use an engine until the wind blows again. This condition has resulted in the installation of many pressure tanks of various kinds, probably the most popular of which has been the steel tank.

The steel tank has not been altogether satisfactory owing to its high initial cost, its short life, and its tendency to rust and to thus taint the water. It has long been recognized that the underground pressure cistern made of concrete would be the ideal cistern, but the high cost of cast concrete and the tendency of the concrete to check and crack and to thus release the pressure have combined to discourage the use of concrete for this purpose.

A climatological factor of the middle west which affects the success of the underground cistern is the range of ten'iperatures between wide extremes. Such temperatures may vary in a single year between forty degrees below zero to a hundred and ten degrees above. During periods of extreme heat the water in storage may be so warm as to be unfit for drinking purposes, but when the opposite extreme is reached the system is apt to cease functioning or even to burst because of the freezing of the water. In the ideal system the water would of course have a fairly constant temperature regardless of variations in the outside temperatures.

Among the objects of my invention is an improved cistern and the method of constructing it are low cost of construction and installation, durability, and resistance to destructive chemical and climatological action. The cistern its designed for the storage of water at fairly even temperatures throughout the year, the water being aerated by the air under pressure, and the water being delivered to the faucet under substantially constant pressures.

Having in view these objects and others which will appear in the description, I will now refer to the drawings, in which The figure shows a median vertical sec tional view of my cistern and of a portion of the well pit.

The structure of my cistern can, at least partly, be best explained by reference to the method of constructing it. I first excavate a relatively deep cylindrical hole in the desired location, the hole having a relatively small diameter. In general the subsoil into which the hole is cut is a stiff, heavy, and tenacious clay which increases in tenacity with increase in depth. I plaster the floor and walls of the excavation with a concrete plaster, in some instances mixing therewith a small proportion of lime plaster. I then build the forms for casting the concrete partition and roof, positioning all of the necessary pipes and connections in the forms before pouring the concrete. The advantages of the plastered walls combined with the cast partition and roof will be fully explained in the subsequent description.

The space enclosed by the walls 10, the floor 11, and the roof 12 is divided by the partition 18 into an upper water chamber and a lower air chamber. This idea of ar ranging the water chamber above the air chamber is of considerable importance in the solution of the problem of designing a successful concrete pressure cistern, and so far as I am aware the idea is new with me.

The pipe 14 passes through the partition 13 and in water and air tight relation therewith. It may terminate at its lower end either immediately or at some distance beneath the partition, or it may extend almost to. the floor 11, but its upper end should be near the roof pipe 14: serves to transmit the air pressureto the surface of the water in the water chamber.

Water from the pump is forced through the pipe 15 into the water chamber, and as the water chamber fills up the air in both chambers becomes compressed, the communicating pipe 1d resulting in an equalization of air pressures in the two chambers. The.

outlet end of the pipe 15, which may beat any level inthe water chamber, is. provided with anautomaticfioat valve for shutting off the'fiow of water when the water reaches a predetermined level in the. water chamber. This level is preferably immediately beneath the upperend of the pipe 14, as otherwise the water might enter the pipe 14; and be carried down into the air chamber.

The pipe15 is of course provided with a check valve 16 to prevent. the water-from flowing-back into the well. To avoid dam age; to the windmill;v and the connections when the outlet of the pipe, 15 is automatically closed by; the float valve, Iprovide a relief alve' 17 of any suitable type, and

when I so desire I may make use of this relief valve to automatically shut 01f the windmill. One simple way of doing this is to suspend an empty pail fromthe shut off lover of the windmill with the mouth of the pail positioned where it will catch the overflow from the relief valve. The weight of the pail and'contentswillthen shut off the windmill. I may however accomplish the same result with any. one of a great variety ofmechanical or electrical controls. These cxpedientsarc so well known however that I do not deem it, necessary to illustrate them, in the. drawings.

Then my. cistern, is properly; set, up. and adjusted, the water from: the pump will tend-to maintain the requisite pressure, as there can benoloss of air frpm the-cistern. In the event however that the air pressure should becometoo low, it-is asimplemattento .forcemorc air into the cistern tl1rou 'h-the pipe 15; The water to bc used is. ofcourse withdrawn through the pipe 18.

llcspite all precautions there is a tendency-forg a ccrtainquantity of water to enter the airchamber, but this quantity. will seldom. be. sufficient to interfere with the operation of my cistern. For removing .water which has entered the air chambenl have: provided an outlet pipe19 with its lower end terminating just above. the floor of the; air chamber. The pipe l9 passes throughtheroof of the cistern and terminatesin a pit 20, the upper end being pro vided witlr a nozzle and avalve. To rid the air chambero'f water i-t'is only-necessary to openthe valveat the upper end of-the pipe 19 and toforce air through .the pipe. .15 and into the-cistern.

hlanh-oles are; provided in the partition and roof respectively. These manholes serve twopurposes, During the construction of the cistern it is necessary that the builder do considerable work on the inside, the manholes'being necessary to give the builder access to theinter'ior. Also after the cistern has been in operation for a number of years it may be necessary to enter the cistern for the purpose of repairing or renewing portions of the pipe or for other purposes. The difficulties of providing an air tight and water tight closure for any kind of opening in a concrete wall are-very great, and so far as. I; am aware Iain the first to produce an effective. closure of that kind andat a cost which will make its installation feasible wlierevensuch a closure is needed.

I will now briefly describe my closure and the method of making it. At the. time of casting the partition and roof of mycistern, I embed a. rubber; ring 21 in A, the concrete. In some of; the ciste1'ns wh ich Iha-ve con structed I used the material of which cushiontires for baby carriages, wheeled coasters, and bicycles are made; This I cut into strips of suitable length and united the ends byv means of rubber or gutta percha cement, thus. making ringswhich are"so1newhat larger in diameterthai'i the opening which isto beclosed. This ring I securedto the forms in sucha way that only a small portion, less than one fourth, would protrude from the, lower side of the concrete wall aftercasting. The closure p ropjer consists of a plate. 22 'having secured c'entrally thereto a rod23 which is'screw threaded at its upperend, Abo vetheopening-I place aplate 24 or other suitable ab'ut 'nei'it with the rod 93 passing, therethrough, and I then draw the. plate'22 tightly ag'ainstthe ring 21 by means of a nuton the screw threaded upper endof the rod 23. This structure may however belvaried in several important particulars Instead of making the ring of rubber,

Imay employ'leather, asphalt, or any other mater al'wh'ich' is suitable for the purpose.

The material must be appreciably compressible, and it shouldma-ke a fairly close bond with the concrete. This bond should be as nearly airtightaspossible, but even in the eventthat thjere should be a slight breaking away of the ring from th'econcrete, the distance around the, transverse circumference of the ring is too great to permit the escape of StilllClGIlbdll to make trouble in theoperation .ofth'e cistern, andthe natural tendency of the compressible material of the ring to fill up small gaps will entirely avoid the occurrence of trouble from this source.

Concrete has been anexceedingly unsatisfactory material for containers for holding air under pressure. Excessive pressures on the walls fof such containers are liable to result in-hair, cracks in the concrete ant such hair cracksif permitted to develop in a cistern will entirely destroy the usefulness of the pressure system because they cause a loss of air pressure through the loss of air, and incidentally they permitthe water to seep away through the cracks. Because of the vital importance of this problem in a cistern of the kind which I describe, it is important that the various pressures in the cistern be considered. In the lower or air chamber of my cistern the air pressures are all directed outwardly from the chamber. The pressures on the side walls and floor of the air chamber are practically counterbalanced by the natural resistance of the clay subsoil, and my experience has been that with a favorable subsoil that the plastered wall and fioor of the air chamber will develop no hair cracks as the result of inter nal pressures. The resistance of the soil likewise protects the side walls of the upper or water chamber of my cistern. Air pressures on the top and bottom of the partition 13 are equal, the only inequality in pressures being due to the weight of the water in the upper chamber. This pressure is directed downwardly on the lower portions of the wall 10 but the compression can not develop the strains which result in cracks. The roof 12 is subjected to air pressure on its lower side, but this pressure is only partly counterbalanced by the pressure of the weight of the soil above it. The inequality of pressures on the roof results in a tension on the upper portions of the wall 10, and unless pro-vision is made for counteracting the upward pressure, cracks will develop in the wall of the water chamber."

I will briefly explain how I protect the side walls of the water chamber against the upward pressure against the roof 12. At the time of casting the partition and roof, I insert reinforcing rods or wires 25. After the setting of the concrete and the removal of the forms I subject the rods or wires to tension and then cover them with concrete plaster in order to protect them from the action of water and air and to prevent their rusting. In some instances I may apply the tension either beforeor during the setting of the concrete. I may apply the tension to the rods in any one of various ways, as for example by means of nuts and threads on the rods or by drawing together and tying the rods in pairs. The specific details of this feature and the reasons therefor will not be dwelt upon at length. in this application, since the structure is the subject matter of my copending application, Serial Number 618733, filed February 12th, 1923.

The dimensions of my cistern are susceptible of some variation, but the principles involved in its construction and operation depend very much on dimensions having a small range of variation. The first consider ation is of course the size, which should be amply large en ugh t meet the normal water requirements of the average farm. The present pressure systems will not do this. The cost of the steel tank of ample size is prohibitive. My problem has beenthe problem of so constructing the pressure cistern of ample size and ata reasonable costthat its installation would be profitable on the great majority of farms.

By reducing the diameter and increasing the length of the cistern I very materially reduce the surface of cast concrete and increase the amount of surface of plastered concrete. This results in a very material reduction in costs since it reduces the amount of farm work and since it requires less cement. This latter is readily apparent from the fact that the plastered wall is only about three-fourths of an inch thick while the cast wall is from five to ten inches thick. The reduction of the diameter has another advantage in that the danger of cracking the side walls is correspondingly reduced. This is true because the bursting pressure of a cylindrical container of gas under pressure varies directly as the diameter. Still an other advantage is due to the fact that the upward pressure of the air on theunder surface of the roof 12 varies directly as the square of the diameter of the roof. I find it advantageous to construct the roof with a diameter not to exceed five feet three inches. With this diameter and an air pressure of twenty pounds per square inch inside the chamber, the upward pressure on the roof is approximately sixty thousand. pounds, and since the weight of the roof is only about eighteen hundred pounds, there must be sufficient reinforcing material to properly anchor the roof to the partition. The reinforcing material is costly, and since there is a considerable reduction in the amount needed with a reduction in the diameter of the cistern, it is obvious that the diameter should be decreased as much as possible, the limit being determined only by the fact that it will be necessary for the operator or builder to do some of the construction work on the inside. If the diameter were reduced to three feet, the upward pressure on the roof would be so small that no reinforcing would be needed.

In a cistern of five feet three inches diameter and having a depth of from seven to seven and a half feet for the water chamber, there will be an ample supply of water for the average farm, with a liberal margin of safety to take care of the requirements for short periods when the Wind is not sumciently strong to pump the water, or when as in the threshing season the drain on the water supply is unusually heavy. In a cistern having these dimensions, I prefer to give the lower or air chamber a depth of from twelve and a haif te fourteen feet. The greater the volume of compressed a r in Cir theair-chamber, the less variation there will be atthefaucets. The pressure once established will be maintained by the inflow of water from the pump. No loss of air can occur except that dissolved in the water under pressure, and this quantity will be so small that long periodscan elapse; before it becomes necessary to restore the air pressure by forcing additional air into the cistern.

The cost of construction is of course materially reduced by making both chambers integral and in the same excavation. The equipment for making the excavation is in place and it is simply a continuation of the job to excavate deep. enough to provide room for the-air and water chambers in a vertical plane. Likewise, the plastering of the walls is simplified by the fact that there is only one continuous wall to be plastered.

Asbefore stated, the position of the water chamber above instead of below the air chamber is ofvital importance, both in the construction and in the successful operation of my cistern. It'is true that if the water were stored in the bottom of the cistern the dividing partition could be dispensed with and that the cost of this partition could thus be saved, but I believe the commercial failures of "many of the concrete cisterns heretofore placed on the market are due to fundamental principles which were .overlooked inthe designing of such cisterns. In the-consideration of concrete as a material for pressure cisterns, the chief factor to be considered is air pressure, because as before stated, internal pressures if excessive are apt to rupture the walls and to produce hair cracks which release the air. In a cistern of the dimensions as I usually employ, a pressure of twenty pounds to the square inch is sufficient to lift the water in. the bottom of the water chamber to tlie required height without causing any undue strain on the walls of the cistern. The thin shell of concrete alone would notresist this pressure. The soil wall however has an ample margin of safety in resisting a pressure of twenty pounds. The concrete wall serves very lit tle more than as an airtight lining for the soil wall. If the water however were stored at the bottom of the cistern, a pressure of about forty-five per cent greater would be requiredto lift the water atthe bottom of the cistern to the same height above the ground- For some soils this pressure is beyond the margin of safety, the only. solution of the difiiculty being to strengthen the walls at-a cost which makes the installation of the concrete cistern entirely out ofthe question on the great majority of farms. The air pressure is however exerted in all directions with the result that the lifting force against the under side of thereof of the cistern is proportionately increased. This also demands construction which will resist the increased pressure, and whether such constuction involves the use of suflicient additional concrete or sufiicient additional reinforcing or both, the additional cost must result in the commercial failure of the cistern.

lVhile I have described the preferred form of my invention in very specific terms, I do not desire to restrict' myself to the exact structure described, since it is obvious that nun'ierous changes could be made without departing from the spirit of my invention. This is especially true'of the cistern itself, which I have described as being made of plastered walls and cast top and partition. In some instances it may be desirable to cast the walls-also, or even to use other than cementitious materials in the construction of the cistern.

Having described my invention and its advantages, what I believe to be new and desire to secure by Letters Patent of the United tit-ates is 1. In a cistern. an underground cavity having an air tight lining on its sides and an air tight roof, a substantially horizontal partition dividing the cavity into an upper water chamber anda lower air chamber, means for equalizing the air pressure air chamber and the upper part of the water chamber, and water-inlets and outlets for said water chamber, the arrangement being such that water cannot normally enter said lower or air chamber.

2. In a cistern, a cavity having an air tight lining on its sides and bottom and'having also an air tiglit'roof, a partition dividing the cavity into an upper water chamber and a lower air chamber, means for equalizingthe air pressure of said chambers, means for. conducting water under pressure into said water chamber, means for automatically stopping the inflow of water when the water reaches a predetermined level in said water chamber, and an outlet for the water whereby the water. from the water chamber may be withdrawn.

3. In a cistern, anunderground cavity, a relatively thin shell of concrete secured to the earth walls and floor ofsaid cavity, a roof for said cavity, a partition dividing the cavityinto an upper and a lower chamber, said lower chamber being designed to serve as acontainer of air under pressure and said upper chamber being designed to serve as a reservoir for the storage of water, means for equalizing. the internal pressures of the two chambers, means for conducting water under pressure into said water chamber, and means for withdrawing the water from the bottom of said water chamber, the arrangement being such that water cannot normally enter said lower or air chamber.

at. In a cistern, an underground cavity, a relatively thin sheet of concrete secured to the'earth walls and to the floor of the cavity, a concrete roof for the cavity, said roof being positioned beneath the surface of the ground, a concrete partition intermediate the floor and roof and dividing said cavity into an upper, Water storage reservoir and a lower air pressure chamber, an open pipe terminating in said air pressure chamber and above the water level of said water storage reservoir for equalizing the pressures of the two chambers, means for anchoring the roof to the partition, and means for conducting water into and out of said water chamher.

5. In a cistern, an underground cavity, a

vessel Within said cavity, said vessel being enclosed on all sides, a substantially horizontal partition dividing the interior of said vessel into an upper water chamber and a lower air pressure .ehamber, means for equalizing the internal pressures of said two chambers, means for forcing out water which collects in the bottom of said air pressure chamber, and means for conducting Water into and out of said water chamber.

In testimony whereof I affix my signature.

RICHARD n. DILL.

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