US2334398A - Water heater - Google Patents

Description

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A JOM?, 15u65 NDV. 16, 1943- J. w. FARREN ErAL WATER HEATER Filed oct. 25. 193s w. w, ma 1W. FARREN'ETAL WATER HEATER Filed Oct. 25, 193 9 4 Sheets-Sheet 2 NGV i6 w43 J. w. FARREN ET AL.

WATER HEATER Filed oct.

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@65e/ll BY dem@ Patented Nov. 16, 1943 WATER HEATER John W. Farren, Russell W. Heywood, and James F. Donnelly, La Porte. Ind., assignora to Bastian-Morley Co., Inc., La Porte, Ind., a corporation of Indiana Application October 25, 1939, `Seriali No, 301,134

16 Claims.

Our invention relates to *water heaters and means for controlling flow of air thereto for combustion purposes, and it has to do particularly with water heaters of the intermittent ring type that embody a storage tank, a main burner of the so-called on and off type located in a combustion chamber, and a flue which extends from the combustion chamber lengthwise of and in heat transfer relation to the storage tank.

Conventional devices of the foregoing character usually include temperature controlling means adapted to shut off the gas to the main burner when the temperature of the water in the tank is raised to a predetermined point and to cut in the burner when the temperature of the water drops below that point, the burner being equipped with a small, constant-burning pilot burner for igniting the fuel (gas, for example) in the main burner when the latter is turned on by the temperature controlling means. Also, the combustion chamber of such heaters is located at the bottom below the storage tank, and it is fully open at that .of heat from the water, particularly during off periods of theburner. This loss is due mainlyto air passing directly and in an uncontrolled manner to the combustion chamber and thence into and through the flue, the amount of air naturally being in excess of that requiredl to support combustion in the pilot burner. formed Vof a heat conducting metallic material and, since the water in the tank is in contact with at least one wall of the flue and this water is hotter than the air passing through the flue during the off period of the burner, there is a direct transfer of heat from the water in the tank to the flue contents, which results in a considerable loss of heat from the water. These conditions are induced in part by the small pilot burner flame which burns at all times, in that it is sulcient to heat the air in the combustion chamber to a point Where its density, compared to that of the air externally of the heater, is such as to induce an upward ow of air through the flue. Also, the amount of heat loss from this cause is proportionate to the amount (including excess) passing through the flue during the ofP periods, and any material reduction in air flow will result in an increased over-all heater efflciency.

In some heaters of the foregoing character, flue means are employed which serve to more efficiently effect a transfer of heat from the flue The nue is gases to the water, such, for example, as disclosed in United States Letters Patent No. 1,947,606, dated February 20, 1934; but, for the same reasons,such structures, when excess air, as above stated, is passed through the ue, as during the od burner periods, serve to transfer a greater amount of heat from the water. to the upwardly moving all;` with resultant greater heat loss.

In some instances, it has been proposed to overcome such loss by the use of automatic dampers, and the like, adapted to open when the main burner is on, and to either shut off' air entering the combustion chamber or close the exit of the flue when the burner is ,o Such devices, while efficient in some respects, are objectionable because, in case of failure of the same to open at the proper time, incomplete combustion and explosions may occur.

One of the objects of our invention is to provide an improved heater oi the foregoing character which isy of simple and inexpensive construction, is highly emcient in operation, and whichincludes new and novel means for reducing heatV loss by limiting the flow of air to the combustion chamber` and through the flue during the off periods f the main burner to substantially the minimum amount of ai: required for operation of the pilot burner.

.Another object is to provide a heater having a ue with means for accomplishing a highly effective transfer of heat units from the ue contents to water in the tank and which, at the same time, is provided with air control means of such character that loss of heat from the Water by the tendency of the flue means to reverse the heat transfer from the water to the ue contents during off" periods of the main burner is minimized, thereby increasing the thermal and service erliciency of the heater.

A further object is to provide a novel means for supplying secondary air for combustion purposes, the arrangement being such that the amount of air admitted to the combustion chamber and, in tum, passed through the ue is controlled by the combustion requirements of the burner and is llimited to substantially that amount required for combustion, whereby a greater utilization of the lheat units discharged by the burner is experienced and the water in the storage tank is heated more quickly and is maintained in a desired heated condition for longer periods lof time with less fuel consumption. Y

Still another object is to provide siphonic means .of the foregoing character so constructed and arranged that, as lthe burner requirements our invention.

creased, the flow of air through the flue isincreased. To this end, we, preferably, provide an inverted Siphon-type or U-shaped passage through which all air for combustion purposes must pass under the siphonic control of flue gases discharged from the flue. This U-shaped pas sage includes a so-called cold leg or air shaft open at oneend to the atmosphere and connected at its other end to the combustion chamber and a so-called hot leg or flue leading from the combustion chamber, the air shaft being of such size and capacity relative to the ue that it creates a drag condition for controlling the flow of air therethrough.

Additional objects are to provide trap means for supplying air to a combustion chamber and by which heat loss through such air is minimized; to provide a heater so constructedand arranged that all operating parts are completely enclosed, providing a compact structure of improved appearance; to provide a heater of the foregoing character wherein the fuel control devices are located in the air shaft leading to the combustion chamber, so that they are swept by incoming secondary air and are maintained in a comparatively cool condition; to provide an. improved form of heater casing that may be located in close proximity to a floor surface without danger of overheating: and to .provide an air control for an intermittent iring type of water heater which includes a passage having connected hot and cold legs, the hot leg being constructed and arranged to minimize the excess air admitted during the on periods of the burner and the' cold leg being constructed and arranged to minimize the excess air admitted during the off" y line 3-3 of Fig. 1;

Fig. 4 is a vertical sectional view, partially in 50 section, of another form of water heater embodying our invention; and

Fig.'5 is a vvertical sectional view of `still another form of water heater structure embodying v Referring particularly to the structure shown in Figs. 1 to 3, inclusive, it includes a cylindrical tank I0 surrounded, in spaced relation, by a cylindrical shell II, the space between the tank and shell being filled with an insulating material I2. The side walls of the tank I0 and shell II are extended downwardly as at I 0* and IIl, respectively, beneath the bottom IIIb df the tank to form, in part, a comparatively shallow combustion chamber I3. The tank I0 and shell II are supported by a cylindrical, imperforate pan-like bottom member I4 upon which the lower edgess of the tank and shell side walls seat. The bottom member I4 is supported upon legs I5 which 'space the heater as a whole from the supporting 70 floor surface. The combustion chamber' I3 is provided with a bottom in the form of a pan or plate-like member I9 supported above and in spaced relation to the bottom member Il and rorming with the latter an air space, the plate 76 member I9 having an opening II located near its central portion leading into the combustion chamber I3. It'will'be seen that, with this arrangement, the only inlet of air to the combustion chamber is through the opening I'I and the space II therebeneath, which space is closed of! from the atmosphere except through an air shaft, which will be described later. The lstorage tank I0 is provided with the usual cold water inlet I9 and hot water service outlet' I9.

The-heater structure is further provided with a cylindrical ilue structure 20 extending vertically or lengthwise through the interior of the tank I0 so that it is surrounded by the water in the latter. The flue 20 is so arranged that its lower end terminates in the bottom II)h of the tank, where it is connected directly to the combustion chamber Il, while its lupper end terminates in the top of the tank I9, where it is connected by an additional flue connection 2| passing through the outer shell II anda. draft diverter 22 to` a discharge stack (not shown). With this arrangement, heat from the hot gases of combustion passing outwardly through the flue 20 are transferred to the water in the tank surrounding the flue. In the particular arrangement illustrated (Fig. 1), the transfer of heat from the ilue products is amplified and improved by employing an additional heat transfer shell 24 extending into the fiueway and bonded thereto for heat transfer purposes., as well`as for the better distribution of the heated gases in the flue, all as more particularly and fully set forth in United states Letters Patent No. 1,947,-

606, granted to Bastian-Morley Company on February 20, 1934. In this arrangement, an efficient heat transfer is provided for Without undue 4restriction to iiow of the gases through the nue, but sufficient restriction is offered to mini-- mize excess air in the flue products when the burner is in its "on position and the heating of the water is in progress.

We have illustrated our invention, in Figs. 1 to 3, inclusive, as used in connection with a heater having a burner 25 supported upon the plate member I9 forming the bottom of the combustion chamber I3. Although the burner shown .is adapted for gas as a fuel, it is to be understood that any other desired fuel and burner construction may be employed with good results. The burner 25 is. preferably, but not necessarily, of the type disclosed in United States Letters Patent No, 1,753,962, granted to Bastian-Morley company on April 8, 1930, and it includes a manifold 29, a plurality of upstanding burner nozzles 21 and a pilot burner 28. Gas is furnished to the main burner manifold through suitable piping 29 having therein a valve mechanism 30 controlled by a thermostatic element 3i located within the water in the tank I0. The arrangement, which is well known, is such that gas is cut into the burner through pipe 29 when thetemperature of the water in the tank is reduced below acertain point and gas is cut olf from the burner when the water in the tank'reaches a. predetermined temperature. Theavalve mechanism 30 is further controlled by the pilot burner 28 in such a way that so long as the pilot burner is lighted so as to ignite gas admitted through the pipe 29 to the main burner, the'valve mechanism 90 will permit the flow of gas when the thermostat 3| functions to open the main gas Valve, but if, for any reason the pilot flame should be extinguished so that gas admitted to the main burner would not be ignited, the pilot control functions to close the main valve mechanism 30 and prevent the flow of gas to the main burner. The pilot control is of the thermoelectric type and it may include (Figs. 1 and 3) a thermocouple element32 (Fig. 3) and amagnetic valve-operating unit 33 (Fig. 1) with proper electric connections including the pilot line 34 and other connections (not shown) enclosed therein; the arrangement being such that, so long as the thermocouple element 32 is heated by the pilot flame, the magnetic unit 33 is energized sufficiently to hold its valve (not shown) of the valve mechanism 30 open and permit the flow of gas, but in the event that the thermccouple element 32 should become cooled by extinguishing the pilot name, the magnetic unit would become deenergized, permitting its gas l:flow control valve to close. In that event, no gas, regardless of the position of the valve controlled by the thermostatic element 3l could now to the burner. Since walls of the tank IIJ and shell II. The member this control mechanism may take any desiredL and well-known form, it will readily be understood by those skilled in the art and we do not believe it necessary to go further into details-'in showing and describing the same.

In carrying out our invention, we control the :dow of secondary air to the combustion chamber i3 in such a way that only substantially that amount of air required for combustion is admitted, whereby, during the "o periods of the burner, a minimum amount of Asecondary air is admitted thereby limiting the amount of air passing through the ue to the minimum. It will be seen from the foregoing description that burner is arranged for intermittent ring thereby t providing so-called burner on and burner oil periods. The thermostatic control for the main burner is, preferably, of the so-called snap-actionthe contour of the outer shell.

type, so that the burner is turnedd and on practically instantaneously, the arrangement being such that the burner is either on full or is' oi entirely. By thus limiting the amount of air admitted, as well as that which must eventually exit through the nue 20, we reduce heat loss through the flue products to a material extent during the off periods of the burner. The foregoing air-limiting control feature is important in the use of any arrangement wherein heat from the products of combustion are passed through or along a wall surfaceV separating the ue products from the water in the tank; and it jis especially important in the use of a ue structure of the character above described, since the heat transfer ability of such nue structure is reversed when excess cold air is passed through the flue, with the result that heat is rapidly extracted from the water in the tank surrounding the iiue. This condition, if permitted to exist, would cause a material emciency-lowering heat loss.

In controlling the air admitted to the heater as above mentioned, we employ an inverted-` siphon or U-shaped passage means. One leg (the so-called cold leg) of this passage takes the iorm of a cold air inlet passage or shaft 35, and the other leg (the so-called hot leg) takes the form of the ue passage 20B, the two legs being joined together to complete the U-shape by the Acombustion chamber I3 and the space II therebeneath. Substantially all of the air admitted to the combustion chamber I3, for combustion purposes or otherwise, must pass through the cold leg of this U-shaped passage. l

Specifically, the air shaft takes the frm of a tubular member 36, preferably of oblong, crosssectional shape, and it is disposed substantially parallel with the ilueway 20B 'between the side a shell-carried hood 38 which is wide enough to extend over the top of the upper end of the shaft, and laterally'thereof beyond the outer shell I I to provide an air inlet 39 located laterally of the shaft 35 and at such a position that the air iiows upwardly, then laterally and downwardly into the air shaft. f

Although the combustion chamber I3 is normally connected with the atmosphere only through the shaft 35, it may be desirable, at times, to have access to the burner for repair and other purposes. To this end, we provide adjacent the combustion chamber a doorway 40 leading through the sections I I8 and IIJa of the outer shell and tank(walls. The doorway, which is preferably of rectangular shape, is formed by a rectangularly shaped casing member lil in which is received a rectangularly shaped door d2 curved to The door ft2 is of the friction-lit type and it includes a metallic section 42a and an inner insulating section 32h and, with the door in place, its inner or insulating-section is adapted to seat firmly against a flange (i3 extending at substantially right angles from and around the door casing il (Fig. 3) at a point intermediate the inner and outer edges of the doorway. The door is held in place Within the opening by a hinge-like unit it at one side and a rotatable latch unit 45 at its other side. The hinge unit member 44 includes one or more pins 46 engaging suitably provided openings in the adjacent part of the casing member I. The latch 45 may include a rotatable latch element All carried by a rotatably mounted handle 48, the latch being adapted to enter a suitably provided slot in the adjacent part of the doorv casing 4I. To place the door in position, the pins or prongs "36 are iirst inserted in their openings and the door then rocked inwardly and pressed into tight seating engagement with the flange 43, after which the handle IIB is turned to move the latch 4l to its latching position. When this is done, the doorway is sealed substantially airtight, but it may readily be removed by releasing the latch structure.

In the use of the structure above described, as-

suming that the main burner 25 isl on, the

heated gases` discharged from the burner pass upwardly into and through the ueway 20a. The nue products are heated suiciently to lower their density tothe point where an updraft is created in the ueway 20B, causing suilicient air to be drawn down the cold leg shaft 35 to support combustion. In this operation, it is to be understood that the size of the inlet opening to the cold leg or shaft 35 is substantially 'in proportion to the volume of gas to be burned. The U-passage (35, I'I, I'I, I3, 20a) acts as an air siphon, the cold air drawn in plus the gas fed to the burner being substantially equal in amount to the-gases discharged through the llue; and, since the cold air inlet is proportionate to the volume of gas to be burned, the air thus admitted is substantially only that required for complete combustion of the gas then being discharged by the burner. Due to the siphoni-c action set up, the admission of secondary air depends upon the displacement of gases in the ue, and only when the flue gases are being displaced is cold secondary air drawn in; and, if the gases discharged by the burner were gradually reduced, with a proportionate reduction in displacement of gases in the ilueway, there would be a correspondingreduction in the amount of air drawn into the heater. Wherefore, when the main burner is turned oi'f by the temperature control means and only the pilot burner remains burning, the secondary air requirements are reduced to the very minimum and only that minimum requirement of air is supplied. When the pilot alone is operating, the ue products are still heated to some (but a lower) extent, thereby lowering the density of the flue products sufiiciently to create an updraft in the iiue 20H; however the temperature of the gases entering the hot leg or flue 2lia is sufficiently low to create only a slight updraft therein, thereby causing but little cold or secondary air to be admitted through the cold leg to the combustion chamber I3. A drag is imposed by the cold leg and, under the foregoing conditions of operation and in furtherance of the siphonic action that takes place, this drag aids in the foregoing result so that the amount of air entering the flue 20 or hot leg is reduced to near the minimum with a minimized loss of heat on account of transfer of heat from the water surrounding the i'iue 20 to the flue products.

By way of example, we have found that our purpose may well be served by employing a water heater construction including a storage tank I of approximately 28 gallons capacity; a burner 25 having a rated capacity of approximately 27,000 B. t. u.s located inv a combustion chamber approximately 14 inches in diameter and 8 inches in height; a flue 20 of approximately 42 inches and having a cross-sectional area of ap'-" proximately 7 square inches; and an air shaft 35 approximately 52 inches in length with a cross-sectional area of approximately 5.75l square inches and having an inlet approximately 5.75 square inches in area. In the use of such structure, the standby loss is reduced more than 2 per cent, asa result of which an operating efficiency of at least 81A per cent more than possible with prior heaters is obtained. It is to be understood that the foregoing structural dimensions are not to be in any sense limiting because they are given merely by way of illustration and, while the dimensions stated are capable of producing excellent results, they may be varied in some or all instances with good results and without departing from our invention.

Our invention is equally well adapted for use A with a heater embodying a so-called ioater type of storage tank. Such a structural adaptation is illustrated in Fig. 4. The structure there shown includes a cylindrical storage tank 50 surrounded, in spaced relation, at its top and sides by a cylindrical shell or liner 5l, which, in turn, is surrounded by another cylindrical shell 52 in spaced relation, providing a space shells, forms a combustion chamber 55. the bottom of which is closed by a panor plate 58 having an opening 51. An imperforate bottom pan 58 carried -by legs 59 supports the shells 5I and 52 and, in turn, the tank 50, as in the firstdescribed form.

A burner 60 similar to the burner 25 (Fig. 1) is mounted in the combustion chamber 55, and it may be controlled in a manner similar to th'e previously described burner structure. The spacing of the shell 50 and liner 5| provides a flueway 5I connected at its lower end withythe combustion chamber 55 and at its upper end with an outlet flue section 52 and a draft' di-. verter 63 leading to a stack (not shown).

Air is supplied to the combustion chamber 55 through an air shaft 64 similar to the air shaft 35 (Fig. 1) and located in the insulation be- `I l tween the shells 5l and 52. The outer end of the shaft 64 is connected to atmosphere through a hood 64 and its irmer end is connected to the combustion chamber 55 through a space 55 `similar to the space i1 (Fig. 1). The air shaft 64, space 65, combustion chamber 55 and flueway Si constitute Aa continuous U-shaped siphonic passage. One of the main differences between this structure and/ that of Fig. 1 is that the hot leg or flue of the U-shaped. siphon passage takes thepform of a flueway passing around the tank wall instead of through it. overheating of the shaft 64 is avoided by locating it in the insulation in such a way that an insulated space 56 is provided between it and the fiueway 5i. Obviously, any other suitable means may 4be employed for, preventing or minimizing any tendency to preheat the air flowing through the shaft 54 before it reaches the combustion chamber.

The heater structure shown in Fig. 5 is similar to the structure first described except that it provides an air flow arrangement wherein the gas control devices are located directly in the path of incoming cold air so that they are maintained in asubstantially cold condition while, at the same time, providing a heater wherein practically all of the, operating parts are completely enclc ed. thereby not 'only enhancing the mechanical utility of the structure but also its appearance.

The structure shown in Fig. 5 is similar to that of Fig. l except that a rectangular shaped outer shell 10 surrounds a cylindrical storage tank 1i. Also, in this form, the cold leg of the U-shaped slphon passage takes the form. preferably, of a rectangularly shaped air duct section 12 near the upper front portion of the outer shell 10, the shell wall adjacent the' same being provided with a plurality of air louvres 13. Beneath the air duct 12, and extending substantially to the bottom of the heater, is anotherand wider and deeper air duct section 14 connected at its upper end to the lower end of the air duct section 12. The lower end of the air duct section 14 is covered by a plate 15 which also extends throughout the width and depth of the heater shell 10, in which plate are located a plurality of openings 18 connecting the shaft section 14 with a space 11 therebeneath.

- The space 11 is connected with the combustion chamber 18 by an opening 18 in the plate 15, whereby the cold leg (sections 12 and 14) of the U-shaped siphon passage are connected to the hot leg (fueway by' way of the openings 18, the space 11 and the opening 18 in the combustion chamber 19.

A burner 8| similar to the burner 25 (Fig. 1) is located in the combustion chamber 19 and the 82 and its connections are located in the air inlet section 'Il directly in the path of the cool air" owing therethrough so that it and its connections are constantly sweptrby cool air and are thus kept in the desired cool condition notwithstanding the fact that they are located within the heater shell. where they cannot be seen. Access to the valve mechanism is had through a rectangular shaped door 84 which is, preferably',

of the friction fitting type similar to the door t2` shown in Figs. 1 and 3. Access to the combustion chamber 19 through the cold air section 14 may 1 be had through an additional friction t door 85 mounted in the back wall of the section 14 and the side wall of the tank 1| forming aside wall of the combustion chamber 19. i

The heater structure shown in Fig. 5 may be mounted in such a way that` the combustion chamber 19 is in close proximity to the supporting .door surface, and it may be desirable to provide additional insulating means to prevent any possible overheating of the floor surface. To that end, we may employ a heat baille plate 8B detachably supported below and shaped similarly to the opening 18. The baille plate B6 is suppoi'tedby hanger legs 86a thereon that pass through the opening 18 and engage the upper surface of the plate 15. A deilector plate 81 is supported beneath the baiiie 86 by a plurality of brackets @d carried by the plate 15, as'shown, or by the side wall of the shell, or in any other desired manner. The baille plate 8E and plate 81 are, preferably, formed of metal of any desired kind adapted to serve as a radiant heat deflector, and the advantages thereof will be well understood. We'may additionally mount upon the plate 81, directly beneath the combustion chamber, another plate 89 which is shaped to provide, when assembled with the plate 81, a dead air space 90. 'Ihe use of the plates 86, 81 and 89 entirelyavoids thepossibility of overheating the floor surface, all without undue restrictionin the flow oi' air from the cold leg of the U-shaped siphon passage to the combustion chamber portion thereof. Other than abovedescribed, the construction and operation of this fornrof device-is the same as that shown and described in connection with Fig. 1.

We believe that the operation and' advantages of our invention will be readily understood from the foregoing description. The air that must be heated by the burner, as'well as the air passing throimh the flue, is limited to substantially only that required. for combustion at all stagesof burner operation. This results in a maximum transfer of heat from'the flue products to the water and prevents, or at least reduces to the minimum, any tendency for' backfiow 'of heat from the water to the flue products during the "off" period of the burner. 'Ihe added eiciency insured by our invention makes possible a more economical operation, all with the minimum oi attention on the part of the user.

It is to be understood that, while we have shown and described three. forms of structure embodying our invention and have giYen one typical dimensional embodiment, other changes in details, arrangements and dimensions of parts may be made without departing from the spirit and scope of our invention as defined by the claims that follow.

v We A l. Water heater structure comprising a storage tank. means providing a combustion chamber bel Aneath said tank, means providing a iiueway extending upwardly from said combustion chamber v A lengthwise of said tank, a burner in said combustion chamber, means for supplying fuel to said burner, and means for gravitationally Supplying air to said combustion chamber for combustion purposes which includes an air shaft extending substantially parallel with said iiueway and externally of said tank and having its upper end connected to atmosphere. and the other end connected to said combustion chamber, a shell surrounding said tankandconibustion chamber-,said shaft being positioned within said shell and spaced from said tank and ueway, said shaft being the only air inlet to said combustion chamber and being so constructed and arranged that the ilowof air therethrough is self-induced solely bythe normal displacement of the products of Icombustion in said combustion chamber and llue- Way.

2. Water heater structure comprising a storage tank, means providing a combustion chamber beneath said tank, 'meansprovding a flueway ex-l tendingupwardly from said combustion chamber lengthwise of said tank, a burner in said combustion chamber, means supplying fuel to saidburner, and means for gravitationally supplying air to said combustion chamber for combustion purposes which includes an air shaft extending Asubstantially parallel with said uewayand externally of said tank and being substantially the only'air inlet to said combustion chamber, said shaft having an-inlet at a height adjacent the exit of said iiue, and having an outlet connected directly to said combustion chamben-a shell surroundingsaid tank and combustion chamber, said shaft being positioned within said shell and spaced from s'aid tank and said ueway, said shaft, combustion chamber and flue constituting '.-a U-shaped or inverted siphonic passage so con- "structed and arranged that the iiow of air therev"through is self-induced solely by the normal displacement of the products of combustion in said combustion chamber and iiueway.

3. A water heater which comprises a storage tank, means providing a combustion chamber directly beneath said tank, means providing a flueyway extending vvertically from said combustionv -chamberl en-dwise of and beyond said tank, a shell surrounding lsaid tank and combustion chamber and so constructed and arranged that it seals said tank and chamber from the atmosphere, a burner located in said combustion chamber, and means for gravitationally supplying air to said combustion chamber and burner which comprises a vertically disposed air-shaft-forming member mounted between said shell and tank and spaced from said tank and said fiueway, means supported by said vshell formingan air inlet to said shaft, and conduit means extending'horizontally and forming an exit from said shaft leading into said combustion chamber.

4. lA water heater which comprises a storage tank, means providing a combustion chamber directly beneath said tank, means providing a iiueway leading vertically fromsaid chamber endwise .of and beyond saidtank, a burner .located in said chamber, an `outer shell completely enclosing said tank and combustion chamber, and

ently of and within the connes of said shell a subv stantially vertical passage leading from a point adjacenta the exit of said fiueway to the lower part of said shell, means providing an inlet of xed size to the upper end of said passage, and means providing an exit from the lower end of said passage leading to said combustion chamber, said passage, yexit means, chamber and flue providing a continuous, U-shaped passage constituting substantially the only source of air entry and flow through said heater.

5. Water heater structure comprising a water storage tank, means providing a combustion chamber directly beneath said tank, means providing a fiueway leading upwardly from said chamber through the water in said tank, a burner and combustion chamber, means for admitting air to said chamber which includes means inside said shell forming a passage extending substantially parallel with said fiueway and externally of said tank and spaced from said tank, and means connecting the upper end of said passage with the` said chamber, ashell surrounding said tank and combustion chamber and means for gravitationally controlling the admission oi air to said chamber for combustion purposes and controlling the exhaust of burned gases which comprises a U shaped, inverted siphonic passage including a hot leg in the form of a fiueway extending substan- .tially vertically from said chamber lengthwise of said tank, and a cold leg in the form oi a passage positioned inside of said shell and spaced from said tank and fiueway, said passage extending substantially parallel with said hot leg and having its inlet end terminating at a height near the height' of the upper or exit end of said hot leg, and said cold leg having its outlet end connected to said chamber at a point below the inlet to 3said flue whereby said chamber'completes said siphonic passage by connecting said legs, the said U-shaped passage constituting substantially the sole source of air entry and flow through said heater.

'7. Water heater structure comprising a storage tank, meansproviding a closed combustion chamber beneath said tank, a shell surrounding said tank and combustion chamber, a flue member extending upwardly from said combustion chamber in said chamber, a shell surrounding said tank longitudinally through said tank in heat transfer contact with the water therein and having an upper exit, a burner in said combustion chamber, means for supplying fuel to said burner, and means by which substantially all of the air for combustion purposes is supplied to said combustion chamber. which means includes an air shaft member extending longitudinally and exteriorly of said tank and providing an air shaft extending substantially the length oi said heater struct-ure parallel with said flue member and having its outer end connected to atmosphere near the height of the exit of said iiue member and its inner end connected to said combustion chamber at a point below the connection between the combustion chamber and said flue member, said air shaft 'member being disposed between said tank and said shellin spaced relation to said tank. y

8. Water heater structure comprising a storage tank, an outer shell member surrounding said tank in spaced relation thereto, insulation means disposed in the space between said tank and shell, means providing a closed combustion chamber beneath said tank and disposed inwardly of said insulating means, means providing a ilueway leading ,vertically from said chamber endwise of and beyond said tank, a burner in said combustion chamber, means for supplying Afuel to said burner, and means for supplying substantially all of the air to said combustion chamber for combustion purposes, which includes a tubular member surrounded by said insulating means disposed between said tank and shell and providing an air shaft extending substantially throughout the length of the heater structure in substantially parallel relation to said fiueway, the upper end of said shaft being connected directly to atmosphere with its lower end connected to the lower portion of said combustion chamber.

9. Water heater structure comprising a water storage tank, means providing a combustion chamber directly beneath said tank, means providing a ilueway I leading upwardly from said chamber through the water in said tank, a burner in said chamber, a shell surrounding said tank and combustion chamber, and means for admitting air to said chamber which includes members forming a passage extending substantiallyl parallel with said ueway and externally of said tank, said members being positioned inside said shell and spaced from said tank, means connecting the upper end of said passage with the atmosphere at a point adjacent the upper end of said ilueway and its lower end with said chamber at a point beneath the latter, said passage, chamber and ilueway being constructed and arranged to provide a continuous inverted siphonic passage of which said air passage constitutes a cold leg and substantially the only inlet for air to said combustion chamber, said fiueway a hot leg, and said chamber a connection between said legs, said passage inlet having an area proportionate to the area of said fiueway and the volume of'the gases to be burned by said burner to insure a siphonic action in the siphonic passage.

10. Water heater structure comprising a water storage tank, means providing a combustion chamber beneath said tank, a burner located in said chamber, means for controlling the admission of air to said chamber for combustion purposes and controlling the exhaust of burned gases which comprises a U-shaped, inverted siphonic passage including a hot leg in the form of a fiueway extending from said chamber through said tank, and a cold leg in the form of a passage extending substantially parallel with said hot leg and disposed exteriorly of said tank and spaced from the wall thereof, said cold leg having an inlet at its upper end connected to atmosphere near the height of the exit of said fiueway and its outlet end connected to said chamber at a point below the connection between the combustion chamber 'and said fiueway whereby said chamber completes said siphonic passage by connecting said legs, a shell surrounding said tank and combustion chamber, said. passage having at least a tank and providing with the side wall of the latter a ilueway, means providing a closed combustion chamber beneath said tank and' with which the inner end of said flue communicates, a second shell surrounding said combustion chamber and said first shell means for supplying fuel to said burner, iiue discharge means connected with the outer. end of said flueway, and means for supplying to said combustion chamber substantially all of the air used for combustion purposes, which comprises an elongated member located exteriorly of said first shell member and spaced therefrom and extending substantially throughout the length of the heater structure with the outer end of said shaft connected directly to atmosphere and its inner end connected to said combustion chamber below said flueway,

said elongated member being positioned inside of said second shell.

12. Water heater structure comprising a storage tank, a shell member surrounding said tank and providing with the side wall of the latter a ueway, means providing a closed combustion chamber beneath said tank and with which the inner end of said flueway communicates, means for supplying fuel to said burner, ilue discharge means connected with the outer end of said ueway, means for supplying to said combustion chamber substantially all of the air used for combustion purposes, which comprises an elongated member located exteriorly of said shell member and extending substantially throughout the lengthof the heater structure with the outer 'end of said shaft connected directly to atmosphere and its inner end connected to said combustion chamber below said flueway, and another shell member surrounding said iirst shell member in spaced relation thereto and enclosing said air shaft member, and insulating means disposed in flueway around the entire side wall of said tank,

said tank having a bottom wallwhich together with the lower portions of said shell members and said bottom closing means forms a combustion chamber, flue discharge means connected with the upper end of said flue space, a burner located in said combustion chamber, means for supplying fuel to said burner, and means for supplying subn stantially all of the air to said combustion chamber for combustion purposes, which comprises a member disposed between said shell members and insulated therefrom by said insulating means and extending substantially throughout the length. of said shell members, means connecting theoutlet end of said shaft directly with the atmosphere. andy means for connecting the inner end of said shaft member with said combustion chamber at a point below said iiue space.

14. Water heater structure comprising a storage tank, a first shell member surrounding said tank in spaced relation thereto and forming therewith aflueway, said shell member extending below said tank and forming with the latter a combustion chamber, imperforate means for closing the bottom of the combustion chamber, a vertical air shaft constituting substantially the only inlet for air to said combustion chamber and having its upper end connected to the atmosphere and its lower end to the bottom of said combustion chamber so thatsaid shaft, combustion chamber and fiueway constitute an inverted siphonic passage, a second shell member surrounding said first shellmember and spaced therefrom to form an insulation chamber, said air shaft being disposed between said rst shell member and said second shell member and positioned in said insulation chamber.

15. Water heater structure comprising a storage tank, means providing a combustion chamber directly beneath said tank, a flue leading from said chamber through said tank, a burner in said chamber, an outer shell enclosing said tank and chamber and extending below the latter and adapted to support the heater upon a surface, a bottom member carried by said shell above its lower edge and providing a bottom for said chamber, said member having an opening leading into 'said chamber, and means for supplying substantially all of the combustion air to said chamber through said opening which includes a member located between said shell and tank and spaced from said tank and providing an air shaft extending from near the top of said tank to said bottom member, said bottom member having one or more openings therein connecting the lower end of said shaft with said opening leading into said chamber.

16.` Water heater structure comprising a water storage tank, means providing a combustion chamber beneath said tank, a shell having a closed bottom enclosing said tank and chamber and shutting off the same from the atmosphere, a ilue member extending upwardly from said chamber through the water in said tank, a burner in said chamber, and means for supplying substantially all of the air to said chamber for combustion purposes which includes means spaced from said tank and forming a passage between said shell and tank leading from near the top of the latter to near its bottom, the upper part of said passage being connected to the atmosphere and its lower part being connected to said chamber, and means including fuel conduits connected to said burner and adapted to cut in and out said burner according to the temperature of the water in said tank, said latter means being disposed in the lower part of said passage where the same is swept by air incoming for combustion purposes.

JOI-DI W. FARREN.

RUSSELL W. HEYWOOD.

JAMES F. DONNELLY.

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