US2154683A - Steam generator - Google Patents

Description

April 18, 1939.

Wv B. KERRICK STEAM GENERATOR Original Filed March 18. 1933 2 Sheets-Sheet 1 fN/E/v Toe lu/smrse 5 Keee/cz,

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April 18, 1939- w B. KERRICK 2,154,683

STEAM GENERATOR Original Filed March 18. 1933 2 Sheets-Sheet 2 f/W ENTOQ; Hm'se & Esme/cu Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE STEAM GENERATOR tion of California Application March 18, 1933, Serial No. 681,468 Renewed November 6, 1936 25 Claims. 122-5448)- My invention relates to a steam generator of the flash type, wherein steam may be produced from relatively cold water in a very short period of time.

Although the invention uses and in various capacities, I am herein disclosing. it in a relatively small form for use as a steam generator in connection with steampressing equipment. However, it will be obvious that the same is not limited to use with such equipment and that the invention may be used with other apparatus utilizing steam. Various types of boilers are now in use, and in some of them, for the purpose of initial heating of the water, a tubular coil is employed. My present invention employs a tubular coil but is so constructed that untreated water may be'employed therein without the accumulation of lime deposits on the inner wall of the coil, thereby maintaining a maximum efliciency in the device. It is an object of the invention to provide a steam generator having a heating coll which connects with an enlarged zone or chamber member of larger diameter than the tube from which the coil is made, together with means for supplying heat to bring the water to a desired temperature, and circulating means connecting the lower end of the enlarged chamber member with the inlet end of the coil, this circulating means including a pump for circulating the water through the .coil at such velocity that formation of steam in the coil is inhibited. Therefore, in the normal operation of my device the steam is formed in the upper part of the chamber member which has a steam outlet for connection to a device, such as a garment presser, in which the steam is utilized.

It is a further object of the invention to provide a steam generator of the above character in which the coil is so formed and a burner or heat producing means is so placed relative thereto that the water flowing through the coil from the inlet end to the outlet end thereof is gradually raised in temperature and receives its greatest heat and highest temperature at the outlet end thereof, and in this condition passes to the chamber member or expansion zone. In the preferred form of the invention this result is accomplished by placing the coil in vertical position with the inlet thereof at the upper end of the coil and with the outlet thereof at the lower end of the coil, such outlet being connected with the chamber member, and the burner being so disposed that the flames thereof will be proximate to the lower extremity of the coil. The

adapted for many circulating means takes water from the lower end of the chamber member and delivers the same to the upper end of the coil, where the temperature of the coil is the lowest. This water travels downwardly through the coil, and its temperature is raised progressively, such temperature reaching maximum at the outlet portion of the coil. Contributing to this efiect, the upper and major portion of the coil is preferably made of steel, and the outlet end of the coil is joined with a tubular member of metal of higher heat conductivity, such as copper or bronze. In a selected operation of my steam generator a substantially solid, downwardly moving column of water is maintained without formation of steam therein, this effect being contributed to by the fact that the water is brought to its highest temperature at the outlet end thereof and by the fact that the flow of water from the lower end of the coil is restricted in a manner to produce a suihcient back pressure against the movement of the water downwardly through the coil that a pressure condition is maintained which, in conjunction with the rapid downward movement, inhibits formation of steam. In the use of the general form of my invention it is recog--. nized that steam may at times be formed within the thermostat and the outlet portion of the heating coil of the device, especially when large quantities of steam are being drawn from the 3() expansion chamber of the steam generator. This steam is, however, moving at relatively high velocity toward the expansion chamber, with the result that sediment contained therein is carried into the expansion chamber.

It is a further object of the invention to pro-qv vide a steam generator of the above character having means for maintaining a substantially constant amount of water therein. In the preferred form of the invention, the automatic water 40 supplying means is controlled by and in accordance with the quantity of water in the lower part of the steam chamber. I have found that there is sufficient diiference in temperature between the lower end of this body of water and the upper level thereof to actuate controlling means, so that when the level of the water drops below a predetermined point due to the use of steam from the generator, the bringing of the upper surface of the water into closer proximity to a thermostatic controlling device will produce a temperature change in the active elements of the controlling device, which will cause a feeding of additional water into the steam generator, this water being preferably delivered into the so inlet end of the coil together with the water which is in circulation through the circulating system. I have also found that the feeding of make-up water into my device may be controlled by the pressure in the upper part of the steam chamber.

Observations of the operation of some types of my invention lead me to the conclusion that where, in the operation thereof, a relatively large quantity of steam is suddenly released from the expansion chamber, the reduction of pressure in the expansion chamber will be transmitted back into the thermostat and possibly the outlet end of the coil, with the result that some of the water therein will pass into steam. However, during the time the steam outlet of the expansion chamber is closed so that there is no delivery of steam from the generator, substantially 'no steam will be formed in the outlet end of the coil.

A further object of the invention is to provide a simple form of water make-up means comprising a water pump having its outlet connected through a check valve with the water piping of the steam generator and having a bypass connecting its outlet with its inlet. Accordingly, the operation of the pump will circulate water through the by-pass and through a valve in the by-pass. This valve has the closure element thereof connected with an actuating means which will cause its movement toward closed position as the water level in the steam chamber is low ered. This closing, or partial closing, of the valve will prevent a free circulation of water through the by-pass and accordingly will cause water to be forced under pressure from the outlet of the pump into the water piping of the generator.

It is a further object of the invention to provide a device of the above character having a water feeding system employing a constant volume pump and heat producing means, thermostatically controlled, capable of producing more heat than is necessary to vaporize the water delivered by the constant volume pump. In this form of the invention a pressure responsive device is connected with the upper portion of the steam chamber and is connected so as to open the electric circuit to the motor driving the feed pump and also the circulating pump, if desired. In this form of the invention, when the water level in the steam chamber rises, and when a sufliciently high pressure is produced in the upper portion of the steam chamber, the circulating system and the water feeding system are both shut down until usage of steam from the steam generator has reduced the quantity of water in the steam chamber and likewise the pressure of the steam therein.

Further objects and advantages of the invention will be made evident throughout the following part of the specification.

Referring to the drawings, which are for illustrative purposes only,

Fig. 1 is a vertically sectioned, schematic view showing a preferred embodiment of my steam generator, in which view some of the parts are drawn to enlarged scale.

Fig. 2 is a cross section on a plane represented by the line 2-2 of Fig. 1.

Fig. 3 is a schematic view similar to Fig. 1 lglut showing an alternative form of the inven- In the form of the invention shown in Figs. 1 and 2 I employ a shell ill of ovate cross section so as to receive in side-by-side relation an upright coil II and an upright cylindrical chamber member l2. The coil II has its inlet end 13 near the upper end of the shell l0 and preferably consists of a plurality of spiral coil sections M. The outlet end l5 of the coil H is disposed a material distance below the inlet end i3 thereof and connects to a thermostat l6 which controls a fuel valve H which is connected through piping ill with a burner 20. Ordinarily the burner 20 is of a type adapted to burn gas, and in such instances the valve I1 is connected with a gas feed pipe 2!. The outlet 22 of the thermostat connects through an upright pipe 23 with the interior of the chamber member i2, the outlet end 24 of the pipe 23 being disposed a distance above the bottom of the chamber member i2. From the upper end of the chamber member I2, a steam delivery pipe 25 having a valve 26 therein is extended.

A circulating system 21 is adapted to connect the lower portion of the steam chamber l2 with the inlet end I3 of the coil II. This circulating system includes a pipe 28 which connects into the lower end of the chamber member l2 at a point below the outlet end 24 of the pipe 23. The outer end 30 of the pipe 28 connects to the inlet 3| of a thermostat l6 which is essentially the same in construction as the thermostat IS in that it includes a head casting 32 with an inlet passage 33 connecting with a tube 34 which projects rightwardly within an outer tube 35, the leftward end of which is connected to the head 32, and the rightward end of which has a cap 36 thereon provided with a stem 31 adapted to move a valve closure member 38 relative to a valve seat 40 formed in a valve casing 41. The leftward end of the annular space 42 between the inner tube 34 and the outer tube 35 connects with an outlet passage 43 in the head 32. Leftwardly from the head 32 a stem 44 projects into a guide tube 45 carried by a frame or spider 4B. Leitwardly from the end of the stem 44 a screw 41 extends through a space 48 formed between the leftward end of the guide 45 and a metal bracket 50. .In the space 48 a nut '5! is threaded on the screw. The spider 46 is connected to the valve casing 4| by means such as tie bars 53. By rotating the nut 5i through use of a handle 52, the screw 5| may be caused to move relative to the spider 46, thereby moving the head 32, the tube 35, the cap 36, and the closure member 38 relative to the seat 48 of the valve casing 4|. The tube 35 is preferably made of a metal having a relatively high coefficient of expansion, such as copper or bronze. Accordingly, as the temperature of the water flowing through the interior of the tube 35 changes, such tube will expand and contract, thereby varying the position of the closure member 38 relative to the valve seat".

The outlet passage 43 of the thermostat I6 is connected through a pipe 54 with a circulating pump 55 which may be of any desired type, such as piston displacement, rotary, or centrifugal, this pump acting to deliver the substantially constant excess water to the coil. The outlet 56 of the circulating pump 55 is connected through piping 51, having a check valve 58 therein, with the inlet end i3 of the coil ll. Accordingly, in the operation of the steam generator, a motor through a shaft Bl drives the pump so as to draw water from the body of water 62 in the lower end of the chamber member and at relatively high velocity force this water into the upper end of the coil and thence downwardly through the coil and through the thermostat l8 into thebody of water 82. As previously'explained, the water traveling downwardly through the coil II is raised to its highest temperature as it passes through the thermostat it, which may for practical purposes be considered the outlet portion of the coil II. The thermostat it, as hereinbefore stated, is of the same construction as the thermostat It and by operation of its handle it may be adjusted so that the valve l1 will control the feeding of fuel to the burner 20 in such quantity as to maintain a constant temperature in the water which flows through the pipe 23 into the lower portion of the chamber member l2. It will be noted that the thermostat I6 is so placed that it is closer to the burner 20 than is the steel tubing 55 forming the lower end of the coil ll proper. Accordingly. the outer face of the tube I! thereof is subjected directly to the heat of the flames from the burner 2il,'and the inner surface of the tube 35' is in direct contact with the water which flows leftwardly therein from the end it of the inner tube ll. Since the tube 35 is made from copper and has a higher rate of heat conductivity than the steel tube of the coil and since the flow of water within the tube 35' is spread out in contact with a larger heating surface. maximum heat is, delivered to the stream while passing through the thermostat It. This thermostat it, which is disclosed and claimed in my copending application filed November 14, 1930, for Fluid heater, Serial No. 495,636, is very sensitive and will not allow the temperature of the water passing therethrough to rise materially above the value for which the thermostat I6 is set. In view of the fact that the thermostat is closer to the burner than the remainder of the coil, the water flowing downwardly through the coil cannot be heated to a higher temperature than the maximum temperature desired in the tube 35' of the thermostat while passing through the steel tube 65. Accordingly, there is, in the normal operation of the device, little possibility of the water flashing into steam in the upper part of the coil II, and there is little deposit of lime on the inner walls of the coil or on the inner walls of the thermostat It. This is proved by an extended use of the invention under the normal operations of a cleaning and pressing establishment without liming up of the coil, as determined by the inspection of such steam generator approximately ten days before the signing of this application.

The water entering the chamber member if is of such temperature that a body of steam is maintained in the upper part of the chamber member I! and additional steam readily ebulliates from the body of water 82 when the pressure in the upper part of the chamber member I! is reduced, as by opening the valve 26 in the steam delivery pipe 25. The chamber member I! is supported on a shelf 88 so that its lower end is protected from direct heat of the flames from the burner ill, but theside walls of the chamber member I! are heated by hot combustion products which travel upwardly through the shell it. though this is not essential to the operation of the invention.

The thermostat 16 forms a controlling element for an automatib means III for delivering feed water to the steam generator. This 'water feeding means Ill includes a pump ll capable of pumping directly against the pressure in the piping 51. The outlet 12 of the pump II is connected through a pipe ll with a nipple ll leading to the valve seat 40 of the valve casing I and is connected through a pipe 1!, having a check valve "therein, with the piping 81 at a point above the check valve 58. From the outlet," of the valve casing ll, a return or bypass pipe IB connects with the inlet ill of the pumpv ll. When the closure member ll is in open position. a shaft 8| from the motor 60 drives the pump ll,'and in consequence thereof the pump II, the inlet of which is also connected to a water supply pipe 82. pumps water through the nipple H, the opening of the valve seat III. the casing 4|, and the pipe 18, which parts constitute a bypass for the pump II.

The wall of the tube 35 forming the expanding and contracting element of the thermostat It, being relatively thin, rapidly conducts heat therethrough from one surface to the other. The inner surface of the tube 35' is subjected to the heat of the water which is flowingtherein, and the outer surface. of the tube 35' is subjected directly to heat from the burner. Accordingly. the expansion and contraction of the tube 35 is approximately in accordance with the mean temperature of the wall of the tube, which mean temperature is one lying between that of the heat of the burner and the stream flowing ,through said tube. The flow in contact with the inner surface of the tube 35' is constantly replaced by fluid from the coil i5 owing to the fact that the pump 55 operates to continuously force a flow of the fluid from the inlet I! of the coil ll, downwardly through the coil, and then through the thermostat it into the expansion chamber i2. This construction produces a control for the heat producing means 20 which is very sensitive and therefore makes it possible to produce a steam generator capable of delivering steam which varies in quantity from zero value to a very large value without the need for a large steam drum having a large quantity of water therein to be kept constantly at substantially a steam forming temperature.

likewise, it is believed that in the operation of the generator where the steam outlet value 26 is suddenly opened so that there is a reduction in steam pressure in the expansion chamber I 2, this reduction of pressure is transmitted back through the pipe 21 into the thermostat tube 35' and sometimes into the outlet portion of the coil II, the result being that the reduction in pressure in the tube 3! permits the ebullition of some steam from the water which is in the tube 35', this formation of steam absorbing some heat from the wall of the tube to instantaneously cause a contraction thereof and an immediate opening of the fuel valve i1 owing to the leftward movement of the rightward end of the tube 35'. The thermostat it therefore is responsive to and acts in accordance with the withdrawal of steam from thesteam generator and is also responsive to temperature changes in the water flowing from the coil into the thermostat. Accordingly, it is my theory that the improved operation of my device over those prior art devices of which I have knowledge is in part accountable for in the possibility that the formation of steam within the tube 35' may vary during the operation of the device in accordance with the pressure changes therein resulting from the withdrawal of steam from the expansion chamber II. In the use of the term "water it should be understood that both liquid and vapor forms thereof are included.

In the form of the invention shown in Fig. 3, the shell l and the parts therein, shown and described in detail in Fig. 1, are duplicated. In this second form of the invention the control of the feed water to maintain the total amount of water in the system substantially constant is accomplished in a different manner, and accordingly the circulating system 21' of Fig. 3 does not have a thermostat l6 therein but comprises piping 85 which connects the lower end of the chamber member I! with the inlet l3 of the coil II, and has a circulating pump 86 and a check valve Bl connected therein. A motor 88 for driving the circulating pump 86 also drives a feed water pump 9| through a-shaft 90, so as to transfer feed water from a supply pipe 92, through a pipe 93 and a check valve 94, to the piping 85 at a point above the check valve 81 thereof. In this form of the invention the feed water pump 9| is of constant volume type, such as a piston pump having a piston which is reciprocated at a constant rate of speed during the operation thereof, thereby delivering a measured positive flow of water into the water piping of the steam generator during the operation of the pump 9|. The size of the burner 20 is such that it is capable of vaporizing at boiler pressure a greater quantity of water than is pumped by the feed water pump 9|, the operation of this burner 20 being controlled by the thermostat I. Into the upper part of the chamber mem ber l2, a pressure responsive device 95 is connected. Associated with the pressure responsive device 95 is a switch 96 having a solenoid 91 for closing the same whenever such solenoid is energized in response to the closing of a switch 98 by the actuating element lllfl of the pressure responsive device which moves in accordance with the change in fluid pressure to which the device 95 is subjected. In this second form of the invention, We rise of the steam pressure in the upper part of the chamber member l2 above the value for which the pressure responsive device 95 is set results in opening the switch 96 which is disposed in an electric circuit lfll connected to the motor 88, thereby stopping the motor 88 at this time and consequently stopping the circulation of water through the circulating system 21' and stopping the delivery of feed water into the piping 85 by the feed water pump 9|. When the pressure in the upper part of the chamber member I! drops below a predetermined value, the pressure responsive device 85 and the switch 96 cause an automatic resumption of the operation of the motor 88 and the pumps connected thereto.

In my invention I have provided a means such as the piping 21 through which hot water is continuously circulated from the drum H to the inlet l3 of the coil, to which circulating flow of water, cool water is added in a relatively continuous and relatively small flow. In the form of the invention shown in Fig. 1, this is accomplished by the action of the valve 38 which is held by the thermostat means IS in such position that during the time steam is drawn from the drum I! through the pipe 25, there will be a relatively constant and proportionate flow of water from the pump into the pipe 51, which flow of cold water intermixes with the hot water flowing through the pipe 51. In the preferred operation of the device no large quantity of cold water is fed suddenly into the inlet end of the coil H, but instead thereof a smalland relatively continuous flow of cold water is added to the pipe 51 through which the hot water is circulating. In this manner, sudden changes in temperature in the coil are avoided and the amount of feed water added to the system is sufiicient to meet the steam demand and maintain the total amount of water in the system approxi mately constant over a period of time.

Although I have herein shown and described my invention in simple and practical form, it is recognized that certain parts or elements thereof are representative of other parts, elements, or mechanisms which may be employed in substantially the same manner to accomplish sub.- stantially the same results; therefore, it is to be understood that the invention is not to be limited to the details disclosed herein but is to be accorded the full scope of the following claims.

I claim as my invention:

1. A steam generator of the character described, including: a coil having an inlet and an outlet; a chamber member connected to said outlet of said coil, there being a steam outlet leading from the upper part of said chamber member; means for producing heat to heat said coil; a circulating system connecting the lower part of said chamber member with the inlet of said coil, said circulating system having pumping means therein for pumping water from the lower end of said chamber member to the inlet of said coil and through said coil at a high velocity so that formation of steam in said coil is inhibited; and means operative in consequence of the change of temperature of the water in the lower end of said chamber member to feed water to said steam generator so as to maintain a substantially constant volume oi water in said chamber member.

2. A steam generator of the character described, including: a coil having an inlet and an outlet; a chamber member connected to said outlet of said coil, there being a steam outlet leading from the upper part of said chamber member; means for producing heat to heat said coil; a circulating system connecting the lower part of said chamber member with the inlet of said coil, said circulating system having pumping means therein for pumping water from the lower end of said chamber member to the inlet of said coil and through said coil at a high velocity so that formation of steam in said coil is inhibited; means arranged to feed make up water to said steam generator; and thermostat means, subject to the heatof the water in said circulating system, for controlling the operation of said water feeding means.

3. A steam generator of the character described, including: a coil having an inlet and an outlet; a chamber member connected to said outlet of said coil, there being a steam outlet leading from the upper part of said chamber member; means for producing heat to heat said coil; a circulating system connecting the lower part of said chamber member with the inlet of said coil, said circulating system having pumping means therein for pumping water from the lower end of said chamber member to the inlet of said coil and through said coil at a high velocity so that formation of steam in said coil is inhibited; means arranged to feed fresh water to said steam generator; and thermostat means, subject to the heat of the water in said circulating system, for causing operation of said water feeding means in response to the rise in temperature of the water in said circulating system above a predetermined value.

4. A steam generator the character described, including: a coil having an inlet and an outlet; a chamber member connected to said outlet of said coil, therebeing a steam outlet leada water supply and its outlet connected to said steam generator through a check valve; means ior continuously driving said feed water pump; a

' by-pass connecting the inlet and the outlet of said feed water pump; a valve in said by-pass; and thermostatic means operative in consequence of the rise in temperature oi the water in said circulating system to move said valve toward closed position whereby to cause water from said feed water pump to flow to said steam generator through said check valve.

5. A steam generator of the character described. including: a vertical coil having an inlet at the upper end thereof and an outlet at the lower end thereof; a chamber member connected to said outlet end of said coilso as to receive heated water therefrom, said chamber member having a steam outlet in the upper part thereof; a circulating system connecting the lower part of said chember member with the inlet end of said coil, said circulating system having means for pumping water under pressure from the lower end of said chamber member to the inlet end of said coil and through said coil at such velocity that'formation of steam in said coil is inhibited; means for producing heat at the lower end of said coil whereby the lower extremity of said coil will receive more heat than the upper part thereof; a feed water pump having its inlet connected to a water supply and its outlet connected to said steam generator through a check valve; means for continuously driving said feed water pump; a by-pass connecting the inlet and the outlet of said feed water pump; a valve in said by-pass: and thermostatic means operative in consequence of the rise in temperature of the water in said circulating system to move said valve toward closed pmition whereby to cause water from said 'ieed water pump to flow to said steam generator through said check valve;

6. A steam generator of the character described, including: a coil having an inlet and an outlet; a chamber member connected to said outlet of said coil, there being a steam outlet leading from the upper part of said chamber member; feed means operative to feed a continuous flow of water to the inlet 0! said coil; a circulating system connecting the lower part or said chamber member with the inlet of said coil, said circulating system having pumping means therein for pumping water from the lower end of said chamber member to the inlet of said coil and through said coil at a high velocity so that formation of steamin said coil is inhibited; heating means for said coil capable of producing more heat than is required to vaporize said continuous flow of water delivered to said coil by said feed means; control means operative in response to pressure changes in saidchamber member to shut down the operation of said feed means when the pressure in said chamber member exceeds a predetermined value; and a thermostatic control means subiect to heat of the water in said steam generator, said control means operating to control said heating means in a manner to produce a predetermined temperature in the water enters ing said chamber member.

7. A steamgenerator of the character described, including: a coil having an inlet and an outlet; a chamber member connected to said outlet oi! said coil, there being a steam outlet leading irom the upper part of said chamber member; feed means operative to tech a continuous flow oi water to the inlet of said coil; a circulating system connecting the lower part of said chamber member with the inlet of said coil, said circulating system having pumping means there in for pumping water from the lower end oi said chamber member to the inlet of said coil and through said coil at a high velocity so that formation of steam in said coil is inhibited; heating means for said 0011 capable of producing more heat than is required to vaporize said continuous flow of water delivered to said coil by said feed means; control means operative in response to pressure variations in said chamber member to shut down the operation or said feed means and said circulating system when the pressure in said chamber member exceeds a predetermined value; and a thermostatic control means subject to heat of the water in said steam zenerator, said control means operating to control said heating means in a manner to produce a predetermined temperature in the water entering said chamber member.

8. The method of producing steam which comprises circulating water through a closed circuit including an elongated heating zone and an expansion zone at arate materially in excess oi the rate of steam production, withdrawing steam from said expansion zone, maintaining the excess of water circulating through said heating zone substantially constant and substantially independent of variation in steam withdrawal, maintaining the velocity of the water in said heating zone at a rate sumciently high in relation to the application of heat to said heating zone to provide a back pressure substantially inhibiting steam generation in said heating zone,- adding feed water to the circulating water, and regulating the application of heat to said heating zone in accordance with the rate of steam withdrawal.

9. The method of producing steam which comprises circulating water through a closed circuit including an elongated heating zone and an expansion zone at a rate materially in excess of the rate of steam production, applying external heat to said heating zone to raise the water therein to steam-forming temperature, withdrawing steam from said expansion zone, maintaining the excess of water circulating through said heating zone substantially constant and substantially independent of variation in steam withdrawal, adding feed water to the circulating water, and automatically regulating the application of said external heat to said heating zone in inverse accordance with the variations in a mean value between the temperature of said water and the temperature of said external heat.

iected to a higher temperature as it moves toward the outlet of said heating zone, withdrawing steam from said expansion zone, maintaining the excess of water circulating through said heating zone substantially constant and substantially independent of variation in steam withdrawal, adding feed water to the circulating water, utilizing the heat of said water and said external heat to produce a mean value, and controlling the application of heat to said heating zone so as to substantially maintain said mean value.

11. A steam generator of the character described, including: a heating coil having an inlet and an outlet; an enlarged chamber connected to the outlet of said heating coil; heat producing means so placed that said coil will be progressively subjected to higher temperatures from its inlet to its outlet; circulating means connecting the lower part of said enlarged chamber with the inlet of said coil, said circulating means including a pump operating to force through said heating coil from the inlet to the outlet thereof a quantity of water materially in excess of the rated maximum capacity of said steam generator, and in such a manner that the pressure in the inlet portion of said coil will be greater than the pressure in the outlet portion thereof; a thermostat connected so as to automatically control said heat producing means so that the water discharged from the outlet of said coil into said enlarged chamber will be maintained substantially constant; means for withdrawing steam from the upper end of said enlarged chamber; and means responsive to a decrease in pressure in said enlarged chamber below a predetermined minimum for starting said pump and for stopping said pump when the pressure in said chamber rises to a predetermined maximum value.

12. A method of generating steam, which method includes the steps of: circulating a substantially constant volume of water under pressure through a circulation path closed from the atmosphere and including an elongated heating zone and a chamber only partially filled with water; applying heat to said heating zone to supply suflicient heat to maintain the temperature of the water in said chamber at the boiling point at the pressure then existing therein while maintaining such flow conditions in said heating zone as to preclude separation of steam therein and thus preclude formation of steam pockets; controlling the heat applied to said heating zone at this time to supply only enough heat to maintain said water in said chamber at said temperature at the boiling point of the water at the pres sure then existing; then reducing the pressure in said chamber to flash some of said water therein into steam and withdrawing said steam from said chamber; then supplying additional feed water to said circulation path at a point which is between said chamber and the inlet of said heating zone in an amount corresponding to that necessary to meet the steam demand, thereby keeping the total amount of water in said circulation path substantially constant; and increasing the heat applied to said heating zone in an amount sufiicient to supply the heat necessary to vaporize said added water.

13. A method of generating steam, which method includes the steps of: circulating water under pressure through a closed circulation path confined from the atmosphere and including an elongated heating zone and a chamber which is only partially filled with water, the upper portion of said chamber containing steam; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein and thus preclude formation of steam pockets; withdrawing steam from said chamber; and controlling the amount of water entering said elongated heating zone in response to said steam withdrawal from said chamber.

14. A method of generating steam, which method includes the steps of: circulating water under pressure through a closed circulating path confined from the atmosphere and including an elongated heating zone and a chamber which is only partially filled with water, the upper portion of said chamber containing steam; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein while said flow continues and thus preclude formation oi steam pockets; and controlling the circulation of water through said closed circulation path in response to pressure conditions in said chamber.

15. A method of generating steam, which method includes the steps of circulating water under pressure through a system providing a closed circulation path confined from the atmosphere and including an elongated heating zone and a chamber which is only partially filled with water, the upper portion of said chamber containing steam; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein while said flow continues and thus preclude formation of steam pockets; and controlling the circulation of water through said closed circulation path and adding feed water, thereto in re-' sponse to pressure conditions in said system.

16. A method of generating steam, which method includes the steps of: circulating water under pressure through a closed circulation path confined from the atmosphere and including an elongated heating zone and a chamber which is only partially filled with water, the upper portion of said chamber. containing steam; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein while said flow continues and thus preclude formation of steam pockets; stopping said circulation through said closed circulation path when the pressure in said chamber rises to a predetermined value; and starting said circulation through said closed circulation path when the pressure in said chamber decreases to a value lower than said predetermined value.

17. A method as defined in claim 16 including the additional step of controlling the heat supplied to said elongated heating zone in response to thermal conditions of the stream discharged from said heating zone into said chamber. 18. A method of producing steam, which method includes the steps of: circulating water under pressure and at a rate exceeding that required to meet the steam demand through a system providing a closed circulation path including an elongated heating zone and an enlarged chamber which is only partially filled with water and which contains steam in its upper end; sup plying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein and formation oi steam pockets while said flow continues; controlling the amount of heat supplied to said heating zone in response to changes in the thermal conditions of the stream discharged from said heating zone to said chamber to maintain these thermal conditions of this stream substantially constant and to maintain the upper portion of said body of water in said chamber at the boiling point at the pressure existing therein; thdrawing steam from said chamber to meet t e steam demand; and introducing into said closed circulation path an amount or make-up water, substantially corresponding to the amount of steam withdrawn from said chamber to maintain a substantially constant amount.o water in the system.

19. A method of producing steam, which method includes the steps oi: circulating water under pressure and at a rate exceeding that required for the steam demand through a closed circulation path including an elongated heating zone and a chamber which is only partially filled with water and which contains steam in its upper end; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steamtherein and formation of steam pockets while said how continues; controlling the amount of heat applied to the heating zone in response to variations in the thermal conditions of the stream discharged from said heating zone to said chamber to maintain these thermal conditions of the str'eam substantially constant and to maintain the upper portion of the body of water in said chamber at the boiling point at the pressure existing therein, the heat thus tending to maintain the pressure in the system; and adding make-up or feed water to said system at such ratetas the steam demand requires.

20. A method t of producing steam. which method includes the steps of: circulating water under pressure and at a rate exceeding that required for the steam demand through a closed circulation path including an elongated heating zone and a chamber which is only partially filled with water and which contains steam in its upper end; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein and formation or steam pockets while said flow continues; periodically stopping said circulation; controlling the heat supplied to said heating zone both during circulation and during cessation of circulation to maintain the upper portion of the body of water in said chamber at the boiling point at the pressure existing therein; and again starting the circulation when the pressure in the system drops below a desired value r 21. A method of producing steam, which method includes the steps of: circulating water under pressure and at a rate exceeding that required for the steam demand through a closed circulation path including an elongated heating zone and a chamber which is only partially iilled with water and which contains steam in its upper end; supplying heat to said heating zone while maintaining such flow conditions therein as to preclude separation of steam therein and formation of steam pockets while saidflow continues; periodically stopping said circulation: controlling the heat supplied to said heating zone during periods of cessation of said circulation to maintain the upper portion of the body or water in said chamber at the boiling point at the pressure existing therein; withdrawing steam from said chamber at a variable rate to meet a changing steam demand whereby an increased withdrawal of steam from said chamber will tend to decrease the pressure in the system; and again lstarting said circulation when this pressure .drops 75 below a desired value.

22. In combination in a device for producing steam: a closed system providing a closed circulation path and including a chamber, an elongated heating zone providing a discharge end communicating with. said chamber and a conduit means connecting said chamber to the intake end or said elongated heating zone; a circulating pump associated with said conduit means to draw water from said chamber and circulate same through said closed path at a rate materially in excess or that amount of water required to meet the steam demand; heating means for applying heat externally to said elongated heating zone; means responsive to the thermal condition of the stream moving from said heatingzone to said chamber for varying the amount of heat applied to said elongated heating zone by said heating means; means for withdrawing steam from said chamber; a feed water pump for introducing make-up water to said closed circulation path; and means for simultaneously stopping said pumps when the pressure in said closed system rises to a predetermined maximum value and for simultaneously starting said pumps when the pressure in said closed system drops to a predetermined minimum value.

23. The method of producing steam which cornprises circulating a stream of water under pres-V sure through a system including a heating zone and into an enlarged zone or zone 01 reduced pressure at a rate of how in excess of a given rate of steam consumption, supplying heat to the heating zone so that said water is heated to a temperature, as it moves toward the outlet of said heating zone, such that at least a portion thereof will flash into steam in said enlarged zone, maintaining the excess water circulation substantially constant to maintain the velocity of the water in said heating zone sufliciently high in relation to the supply of heat to said heating zone to provide a back pressure while heat is being supplied to said heating zone and to substantially prevent accumulation of steam or the formation of steam pockets in said heating zone, adding feed water to the circulating water, and regulating the supply of heat to said heating zone in accordance with changes in the thermal condition of the stream at the outlet end of said heating zone.

24. The method of producing steam which comprises forcing a stream of water under pressure through a system including a heating zone at a rate of flow materially in excess of a given rate of steam consumption, supplying heat to said heating zone so that said water is progressively heated to the boiling point at the pressure existing in said heating zone as it moves toward the outlet of said heating zone, discharging said stream from said heating zone into an enlarged zone to flash at least a portion thereof into steam, withdrawing steam from said enlarged zone to meet a consumption demand, adding circulating and feed water to the heating zone to compensate for that withdrawn from said eniarged zone in the torm of steam and to maintain said excess rate of flow; and increasing and decreasing the supply oi' heat to said heating zone in accordance with changes in a mean temperature lying between thentemperature oi the stream discharging irom said heating zone and the temperature of said external heating medium.

25. A steam generator of the character described, lncluding: a heating coil having an inlet 'andan outlet; an enlarged chamber; means including a thermostat connecting the outlet of said coil to said enlarged chamber; circulating means including a pump operative to force a quantity of water materially in excess of the rated steam-producing capacity of said steam generator through said heating coil from the inlet to the outlet thereof at such velocity as to preclude the formation of steam pockets in said heating zone; heat-producing means for heating said water as it passes through said coil, said thermostat being in the path of flow of said water and directly exposed to said heat-producing means and automatically controlling said heat-producing means in a manner tending to maintain the temperature of the heated water entering said enlarged chamber substantially constant; and

means for supplying feed water to said heating coil at a rate substantially corresponding to a rate at which steam is withdrawn from said enlarged chamber to meet a given demand, thereby maintaining the volume of water in the system substantially constant, said feed water supply means including a feed water pump and means operatively associated with said enlarged chamber for starting said feed water pump when the pressure in said enlarged chamber decreases and for stopping said feed water pump when the pressure in said enlarged chamber increases.

WALTER B. KERRICK.

CERTIFICATE OF CORRECTION- Patent No. 2,15l 6B5.

April 13, 19 9.

HALIER B. KERRICK. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page}, second column, line I 6 for "value" read valve;

page 5, first column, line 5h,

claim 5, for "chember"- read chamber; page 6, second column, line 10, claim 11+, for the word "circulating" read circulation; and thatthe said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 50th day of May, A. D. 1939.

(Seal) Henry Van Arsdale Acting Commissioner of Patents.

means including a pump operative to force a quantity of water materially in excess of the rated steam-producing capacity of said steam generator through said heating coil from the inlet to the outlet thereof at such velocity as to preclude the formation of steam pockets in said heating zone; heat-producing means for heating said water as it passes through said coil, said thermostat being in the path of flow of said water and directly exposed to said heat-producing means and automatically controlling said heat-producing means in a manner tending to maintain the temperature of the heated water entering said enlarged chamber substantially constant; and

means for supplying feed water to said heating coil at a rate substantially corresponding to a rate at which steam is withdrawn from said enlarged chamber to meet a given demand, thereby maintaining the volume of water in the system substantially constant, said feed water supply means including a feed water pump and means operatively associated with said enlarged chamber for starting said feed water pump when the pressure in said enlarged chamber decreases and for stopping said feed water pump when the pressure in said enlarged chamber increases.

WALTER B. KERRICK.

CERTIFICATE OF CORRECTION- Patent No. 2,15l 6B5.

April 13, 19 9.

HALIER B. KERRICK. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page}, second column, line I 6 for "value" read valve;

page 5, first column, line 5h,

claim 5, for "chember"- read chamber; page 6, second column, line 10, claim 11+, for the word "circulating" read circulation; and thatthe said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 50th day of May, A. D. 1939.

(Seal) Henry Van Arsdale Acting Commissioner of Patents.

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