US2553817A - Thermally actuated pump - Google Patents

Description

y 22, 1951 N. ERLAND AF KLEEN 2,553,817

THERMALLY ACTUATED PUMP Filed Sept. 1, 1948 2 Sheets-Sheet 1 INVENTOR M4 6 Fem/v0 AF KLEs/v BY m, M, @nh $662M ATTORNEYS y 1951 N. ERLAIND AF KLEEN 2,553,817

THERMALLY ACTUATED PUMP Filed Sept. 1, 1948 2 Sheets-Sheet 2 INVENTOR /v/Ls ERLAND AF Ines v 2 am), M, w? 115 ATTO R N EYS i atented May 22,

2,5531817 THERMALLY' ACTUATED PUMP Nils Erland af Kleen, North Stonington, Conn, assignor to Jet-Heat, Inc Englewood, N. J., a

corporation ofNew' York Application September 1, 1948, Serial No. 47167 11 Claims; (01. 103 255) This invention relates to thermally actuated pumps. More particularly, the invention contemplates a thermally actuated pump capable of delivering liquid fuel under pressure to a fuel burner or the like.

Thermally actuated pumps such as those described in United States Patents No. 11848226, issued March 8, 1932, and No. 2,015,240, issued September 24, 1935, both to Scott-Snell et al., have been proposed and used theretofore for'supplying liquid fuel under pressure to a burner. These pumps, as constructed and arranged heretofore, have been capable of functioning satisfactorily onl for a limited'period of time. The essential elements of such pumps comprise a heating tube in which the liquid fuel may be partially vaporized, a condensing tube adapted to provide an upright column of the liquid fuel, and a vapor tube connecting the heating and condensing tubes in such manner that vapor produced in the heating tube is conveyed to the upper portion of the condenser tube. The lower end of the condensing tube is connected to the heating tube in order to permit the flow of liquid fuel therebetween.

In operation, the various tubes comprising the pump are initially filled with the liquid fuel. Heat is then applied continuously to a pertion of the heating tube. The fuel vaporized within the heating tube creates an internal pressure within the pump system and forces a portion of the liquid fuel from the system through a one-way valve which is usually positioned adjacent the upper end of the condensing tube. Thus, as the fuel vapor displaces the liquid fuel in the vapor line,

liquid-fuel is continuously discharged from the system. However, when the vapor completely fills the vapor line andreaches the relatively cool liquid in the'ccndensing tube, condensation of the vapor. immediately commences with a resulting drop in the internal pressure within the systeml This lowered pressure permits the'liquid'fuel in the heating tube to flow therethrough and into the vapor line. Toward the end of 'theconden sation period a vacuum is created by the absence of that volume of liquidfuel which was-driven from the system during the vaporization. period. The fuel which has been discharged from the pump system'through the one-way valve cannot be drawn back into the pump to-restore the equilibrium, and advantage is taken-of this vacuum by connecting thesystem to a supply of liquid fuel through a secondone-way valve which permits this fuel to be drawnintothe system. Accordingly, the pumping cycle is started by the pressure of vaporization which forces liquid fuel from the- V pump. When the fuel vapors reach the cool liquid in the condensing tube and begin to condense; liquid fuel is drawn up through the heatingtube and into the vapor tube with the result that fur ther vaporization does not take place during condensation. As the condensation continues; a vacuum is createdwithin the system and this vacuum draws fresh liquid fuel into the system to replace that forced out of the system during the vaporization stage. When equilibrium is once again established and the flow of liquid fuel'through the system ceases, the heating tube again vaporizes more liquid fuel and'the cycle is repeated. De pending upon the relative cross-sectionalareas of theheating, condensing and vapor tubes, and the pressure against which the pump operates; the condensation and re-filling operation requires from 1 to 2 seconds and the vaporization'andldischarging operation requires from 6 to seconds, with the result that the pumping cycle varies from" about 6 seconds to about one minute.

As previously indicated, the utility of such pumps has been impaired by the fact that they generally cease functioning in an unpredictable period of time which is generally a matter of hours. Non-functioning appears to be the result of the heating tube running dry with consequent cracking and carbonization of the film of fuel within the heated portion of the heating tube; This characteristic failure of a therma-l1y actuated pump has defie'dall attempted rectification by variations in the size, proportions and contortions of the tubular elements thereof;

I have now discovered that operation of a thermally actuated pump may be' so prolongedas to operate indefinitely without failure when a reservoir adapted to holda'body of the liquidfuel is interposed in the connection between the lower end o'f'the condensing tube andthe heating tube.

Thus, the termally actuated pump of my present invention comprises a heating tube provided with means for heating liquid fuel in the tube, a condensing tube adapted'to containliquidjfuelfor condensing vapors of the fuel produced in'sa'id heatin tube, a vapor tube for conveyingfuel vapors produced in the upper portion ofthe heating tube to the upper portion of the condensing tube, and a reservoir adapted to hold a body of the liquid fuel in communication with both the lower portion of said heating tube and the lowerportion of said condensing tube and providing a liquid fuel connection therebetween. v I

I have been unable to ascertain with certainty the reason for the'efiecti-veness of such a reser voir interconnecting the heating and condens- ,it would rise to the top of ing tubes in preventing failure of the thermally actuated pump under prolonged operation. However, a plausible explanation may be that the reservoir of liquid fuel prevents the transfer of heat from the heating tube to the condensing tube to such an extent that the temperature of the liquid fuel in the condensing tube does not rise to such a value as to prevent effective condensation. It appears likely that failure of the pumps of the prior art may be caused by heat transfer from the heating tube through the liquid fuel into the lower portion of the condensing tube. As the liquid fuel in the lower portion of the condensing tube becomes heated, the condenser tube. The presence of relatively hot liquid fuel in the upper portion of the condensing tube would prevent effective condensation of the fuel vapors rising through the vapor line so that at least a portion of these vapors would be discharged through the one-way discharge valve at the top of the condensing tube. The resulting passage of vaporized fuel through the hot liquid in the upper portion of the condensing tube would thus maintain the over-heated condition in the condensing tube while the liquid fuel in the heating tube continued to be vaporized. As a result, the liquid level in the heating tube would be lowered progressively until no liquid other than a filrn of the fuel on the heated side walls of the tube would remain in the heating zone. This explanation would account for the carbonization, resulting from cracking of the fuel, which occurs in the heating zone when such a pump fails. Carbonization Within the heating tube would preclude further efficient transfer from the heating means to additional liquid fuel which may subsequently be introduced into the system and would thus prevent further operation. The interposition of a reservoir of liquid fuel between the heating tube and the lower end of the condensing tube in accordance with my present invention may conceivably function as a barrier to the transfer of heat from the heating tube to the condensing tube and thereby makes possible continuous and uninterrupted pump operation by insuring the presence of an adequate quantity of liquid fuel in the pump during operation. The provision of an adequate amount of liquid fuel in the pump for starting conditions is insured by a hand-operated pump as more fully discussed hereinafter.

The thermally actuated pump embodying these and other novel features of the present invention will be more fully understood by reference to the accompanying drawings in which Fig. 1 is a side View, partly in section, of the pump and starting pump system of my invention connected, for the purpose of illustration, to a vaporizing-type burner; and

Fig. 2 is a partial sectional side View of a modified form of starting pump and fuel supply system for use with the pump of the invention.

The vaporizing-type burner ill shown in Fig. 1 is of conventional design and is provided with burner ports ll through which vaporized fuel issues. Liquid fuel for the burner is delivered under pressure through a supply line i2 connected thereto. The heat of combustion of the fuel in the burner is used to volatilize the liquid fuel therein so that the fuel is burned in vapor form as it issues from the burner ports H. The heat of the burning fuel may also be used, as described hereinafter, to supply heat for operating the pump of my invention.

The heat operated pump of my invention comprises, as shown in Fig. 1, an upright heating tube l3. Heat is advantageously applied to the tube by a metallic conductor M which carries heat from the flame of the burner IE3, or other suitable heat source, to a portion of the side wall of the heating tube [3. I have found it ad- Vantageous to have the heat conductor la make contact with the heating tube throughout only about one-half of the circumference of the tube. Thus, as shown in Fig. l, the heat conductor or bar I4 makes contact with the heating tube 13 through the medium of a yoke I la at one end of the conductor. The yoke is advantageously removably secured to the heating tube by a clamping screw Mb extending through the arms of the yoke. The conductor is covered with heat insulation it in order to insure a relatively high temperature at the unheated end of the conductor which makes contact with the heating tube.

The upper end of the heating tube is provided with an inverted U-shaped bend it. The bend serves as a trap to accumulate vapor as it is formed in the heated portion of the heating tube. The end of the bend it communicates with a vapor line I! which is of considerably smaller cross-section than the heating tube in order to insure delivery of the vapor to the condenser tube as a coherent body rather than as a series of bubbles.

The vapor tube I! slopes upwardly from the end of the heating tube to the upper portion of an upright condensing tube l8. The condensing tube is of substantially the same cross-sectional size as the heating tube and is adapted to hold a body of liquid fuel in communication with the liquid fuel in the heating tube. The upper end of the condensing tube is provided with an outlet tube l9 communicating with a valv assembly 29 which controls the discharge of liquid fuel from and the delivery of liquid fuel to the pump system. The valve assembly 20 includes two one-way valves 2| and 22. One of thes valves (2|) permits only the discharge of liquid fuel from the system and into the fuel supply line 42 for the burner. The other one-way valve (22) permits only the entry of fresh liquid fuel into the pump system from a suction line 23 communicating with an external body of liquid fuel. The valve assembly is also provided with a release or safety valve 2 which is adapted to bypass liquid fuel from: the burner supply lin i2 (1. e. the output line of the pump) to the suction line 23 in the event that the fuel pressure in the burner supply line exceeds a safe value.

It will be noted that the valve assembly 25 maintains only a small volume of liquid fuel between the two valves 2! and 22. This arrangement appears to contribute to an important extent to the characteristic smooth operation of the pump system of the invention inasmuch as it makes it possible to draw relatively cool liquid fuel into the top of the condensing tube it. Only a small amount of the previously discharged warm liquid fuel remaining in the valve assembly 20 is drawn back into the condensing tube l8, and this warm fuel is well cooled by admixture with the relatively large quantity of fresh liquid fuel drawn into the system through the suction line 23. Thus, the valve assembly 28 promotes the maintenance of a relatively low temperature in the condensing tube with concomitant improvement in the functioning of the pump sys- As pointed? out hereinbefore, the. lower end ofthe heating tube [3 communicates with the' lower end of the condensing tube i8. In accordance with my present invention; this: communication is effected by means of a reservoir 2'5 adapted to hold a body of. the liquid fuel in communication with the lower portions of both the heating and condensing tubes. The reservoir should be of such size as to hold a body of liquid fuel of sufficient mass to minimize heat transfer from the liquid fuel in the lower end of the heating tube to the liquid fuel in the lower endv of the condensing tube. The effectiveness of the reservoir 25 for this purpose is lost when the heating tube is and condensing tube I8 communicate merely with the top of the reservoir 25. It appears that under these latter conditions liberated air or fuel vapor, or both, collects in the upper portion of the reservoir and bridges the lower ends of the heating and condensing tubes. The lower ends of these tubes l3 and It should be so connected to the reservoir 25 as to insure a liquid fuel path of relatively large volume (at least about 20% and advantageously at least 35% of the total volume of the pump system) bridging or interconnecting the heating and condensing tubes and thereby presenting an impediment to heat transfer therebetween. By thus minimizing the heat transfer from the heating tube to the condensing tube it is possible to prevent elevation of the temperature of liquid fuel in the upper portion of the condensing tube to a non-condensing value.

Further stabilization of temperature conditions in the condensing tube is effected by immersing the reservoir. 25 in a body of the liquid fuel 26 to be supplied to the burner. The fuel in which the reservoir is immersed tends to cool the reservoir and assists in maintaining the temperature of the condensing tube below the critical non-condensing value. Moreover, the preheating of this body of fuel by the heat transmitted to it from the reservoir tends to remove dissolved or entrapped air from this fuel supply before it is delivered to the pump system. The elimination of air from the fuel supplied to the system contributes materially to the smooth and uninterrupted operation thereof'inasmuch as it prevents the development of an air lock within the system.

In order to initiate operation of the pump, it is necessary to fill the pump system with liquid fuel. For this purpose I provide an auxiliary hand-operated pump 21. A particularly advantageous arrangement is shown in Fig. 1 wherein the pump 2'! is connected to the pump system. In this arrangement, the hand pump is connected into the pump reservoir 25 and is provided with two one- way valves 28 and 29 in the. conventional manner. As the pump handle 30 is withdrawn, liquid fuel is drawn into the pump cylinder, and as the pump handle is forcedv inwardly this fuel is expelled into the pump system through the reservoir 25; It will be seen, accordingly, that the pump 2'! in this arrangement not only insures the filling of the pump system with liquid fuel before starting its operation, so as to avoid the possibility of carbonization of the interior of the heating tube I3, but further makes possible the delivery of liquid fuel under pressure to the burner so that operation of the burner may be initiated. without waiting for the main pump system to operate. The further provisionv of an accumulator tank 36 in the fuel supply line I2, as shownin Fig. 1, makes it possible to store sufilcient liquid fuel under pressure to maintain operation of the burner until the main: pump system commences operation without having to.

operate the hand pump 27 after the initial pressure has beenestablished thereby.

The auxiliary pump shown in Fig. 2 forces liquid fuel directly into the output line E2 of the main pump system, andisparticularly advantageous where the main pump is so assembled that it. always contains sufficient liquid fuel to permit operation without auxiliary filling by a hand-operated pump such as that shown in Fig. 1. The auxiliary pump shown in Fig. 2 makes it possible to deliver liquid fuel under pressure to an appropriate burner so as to initiate operation of the main pump system. The body of liquid fuel 25' in the. tank SI in which the reservoir 25 is immersed may be maintained by any suitable manner such as a suction supply line 32 from a main body of fuel or an auxiliary supply tank 33 (as shown in Fig. 2) provided with a float controlled delivery valve 34.

In operation of the pump of the present invention, the auxiliary pump 2? is operated until the liquid fuel, such as kerosene or the like, in the supply tank 3'! is forced into and completely fills the entire pump system and the burner system under a pressure of at least 20 p. s. i. A small amount of volatile combustible such as methanol is poured into the annular dish 35 surrounding the lower portion of the burner. The methanol is ignited and is allowed to heat and volatilize the liquid fuel in the burner system. When fuel vapors begin to issue from the burner ports ll, these vapors are ignited and are permitted to heat the metallic conductor it. The conductor then heats the side wall of the heating tube [3 in contact therewith and effects volatilization of the liquid fuel in this heating zone. The contact of the conductor 54 with only a portion of the periphery of the heating tube 93 is of particular value in that it aids in insuring the presence of some liquid fuel within the heating tube at all times in order to prevent cracking of the fuel with resulting carbonization. As the fuel vapors are generated they collect in the inverted U- shaped portion it of the heating tube and gradually pass into the vapor tube H. The generation of fuel vapor within the pump system is accompanied by the generation of internal pressure within the system. This generated pressure causes liquid fuel to be forced through the oneway valve 25 into the burner supply line S2. The vapors continue to form and to displace the liquid fuel in the vapor tube ll until the vapors reach the body of relatively cool liquid fuel in the upper portion of the condensing tube it. The resulting contact between the small crosssectional mass of fuel vapors and the relatively large cross-sectional mass of liquid. fuel initiates condensation of the fuel vapors. As condenses tion' of these vapors proceeds, the difference in liquid level between the fuel in the upper portion of the condensing tube 28 and the fuel in the heating zone of the heating tube 53 causes the liquid fuel to flow upwardly through the heating tube. Theresulting ingress of relatively cool liquid into the heating zone terminates further vaporization under these conditions and. expedites the condensation taking place in the upper portion of. the condensing tube. Thus, once condensation is initiated it continues rapidly andquickly establishes a partial vacuumin the pumpsystem. Under these conditions,- liquid fuel flows into: the pumpisystemi through the suction line 23 and its one-way valve 22 with the result that relatively cool liquid flows into the upper portion of the condensing tube 18 until the pressure within the system returns to normal. At this point in the operating cycle, the liquid again substantially completely fills the pump system and is at rest. The continued application of heat to the heating tube 13 once again establishes vaporizing conditions therein and the pump cycle is repeated. It will be seen therefore that heat is continuously applied to the heating tube by the conduction thereto of the heat of the burner flame and that the thermally actuated (or main) pump system cyclically discharges liquid fuel therefrom under pressure and draws fresh liquid fuel thereinto. In general, the pumping cycle will start within about 1 minutes after the burner flame has been ignited. The accumulator tank 36 not only aids in maintaining the initial fuel pressure provided by operation of the auxiliary pump 21 until the main pump system begins to operate, but also serves to absorb the pulse-like discharge of liquid fuel from the main pump so that the output pressure of the main pump is substantially uniform.

By appropriate choice of the dimensions of the various tubes of the pump system, the system can be made to operate with a cycle of about 20 to 45 seconds and with an intermittent discharge of liquid fuel therefrom at a pressure of 20 to 35 pounds per square inch. For example, when operating with a petroleum distillate of which 90% is volatile at 466 F. and 99% is volatile at 504 F., liquid fuel is discharged to the burner at a pressure of 20-25 p. s. i. when heating is so applied that for the specific tube sizes a temperature of about 120 F. is established in the fresh liquid fuel supply tank 3!, a temperature of about 200 F. is established at the lower end of the condensing tube 58 and a temperature of 225-250 F. is established in the upper portion of the condensing tube l8. This pressure and the general operation of the pump are not materially affected by variations in the ambient air temperature within the range of 60-l10 F. The foregoing temperature and pressure conditions prevail when the heating is such that the fuel within the heating zone of the heating tube reaches a temperature of 425 F. during the pumping portion of the operating cycle and drops to 405 F. during the condensing portion of the cycle. By increasing the heating rate so that the fuel temperature within the heating zone rises to 460 F. during the pumping portion of the operating cycle, the pressure of the liquid fuel discharged from the pump is increased to 3035 p. s. i. The foregoing temperature and pressure conditions were recorded for apparatus in which the internal diameter of the heating tube is was 9e inch, that of the vapor tube IT was inch, that of the vcondensing tube E8 was s inch, and that of the reservoir 25 was A; inch. The reservoir 25 was 3 inches in length and held 29 cc. of liquid fuel. The total volume of the main portion of the system consisting of the heating tube E3, the vapor tube H, the condensing tube 58, and the reservoir 25 was 60.2 cc. When operated as described hereinabove, this pump system was capable of delivering to the burner 0.5 gallon of liquid fuel per hour at a pressure of 20-25 p. s. i. for days at a time without any interruption or incipient interruption due to the heating tube running dry. Experimental reduction of the length of the reservoir 25 to about 2 inches, on the other hand, caused the system to run dry in a matter of hours. It will be seen, accordingly, that the size and shape of the reservoir must be such as to limit 7 the rate of heat transfer from the lower end of the heating tube to the lower end of the condensing tube to a value below that at which the liquid in the condensing tube will be heated to a non-condensing temperature.

I claim:

1. A thermally actuated pump capable of delivering a liquid under pressure comprising (1) a closed system including a heating tube provided with means for heating liquid in the tube to a vaporizing temperature, a condensing tube adapted to contain the liquid for condensing vaporized liquid produced in said heating tube and conveyed to the condensing tube, a vapor tube for conveying vapor produced in the upper portion of the heating tube to the upper portion of the condensing tube, and Connection means providing liquid communication between the lower portions of the heating and condensing tubes, said connection means having a cross-sectional area greater than that of the cross-sectional area of the heating and condensing tubes and having a liquid volume capacity of at least 35% of the liquid volume capacity of the entire closed system, and (2) valve means associated with the condensing tube adapted to permit discharge of the liquid from the closed system by the pressure produced within the heating tube upon vaporization of the liquid therein and adapted to permit drawing of additional liquid into the tube from a supply thereof upon a lowering of the pressure within the pump by condensation of said vapor in the condensing tube.

2. A thermally actuated pump capable of delivering a liquid under pressure comprising (1) a closed system including a heating tube provided with means for heating liquid in the tube to a vaporizing temperature, a condensing tube adapted to contain the liquid for condensing vaporized liquid produced in said heating tube and conveyed to the condensing tube, a vapor tube for conveying vapor produced in the upper portion of the heating tube to the upper portion of the condensing tube, and connection means providing liquid communication between the lower portions of the heating and condensing tubes, (2) an outlet-inlet valve assembly, and (3) a single outlet-inlet tube for the closed system communicating between the upper portion of the condensing tube and the outlet-inlet valve assembly, said valve assembly comprising two oneway valves one of which permits discharge of liquid from the outlet-inlet tube by the pressure produced within the heating tube upon vaporization of the liquid therein and the other of which permits drawing of additional liquid from a supply thereof into the system through the outletinlet tube upon a lowering of the pressure within the pump by condensation of said vapor in the condensing tube.

3. A thermally actuated pump capable of delivering a liquid under pressure comprising (1) a closed system including an inverted U-shaped heating tube, a substantially vertically disposed condensing tube adapted to contain the liquid for condensing vaporized liquid produced in said heating tube and conveyed to the condensing tube, one leg of the inverted U being provided with heating means adapted to substantially continuously heat liquid contained in said tube, connection means providing liquid communication between the lower end of said heated leg of the heating tube and the lower portion of the condensing tube, and a vapor tube for conveying vapor produced in the heating tube to the con- :9 densing tube, said vapor tube communicating-between the lower end ofitheother'leg of theLheat ing tube anda portion of the condensing tube located above the level ofthetopof .said inverted U -shaped heating tube, and (2) valve associated with the condensing tube adapted to permit discharge of the liquid from the closed system by thepressuite produced within theheating tube upon vaporization of the liquid therein and adapted to permit-drawing'of additional liquid into the tube from a supply thereof upon a lowering of the pressure within the pump by condensation of said vapor in the condensing tube.

4. -A thermally actuated pump capable of -de livering a liquid under pressure comprising (1) :a closed system includin an inverted U -shaped heating tube, a substantially vertically disposed condensing tube adapted to contain the liquid for condensing vaporized liquid produced in'said heating tube and conveyed to the condensing tube, one leg of the inverted U being provided with heating means adapted 'tosubstantially continuously heat liquid contained in said tube,'connection means providing liquid communication between the lower end-ofsaid heated leg of the heating tube and the lower portion of the condensing tube, and a vapor tube for conveying vapor produced in the heating tube to :the condensing tube, said vapor tube communicating between the lower endof the other leg of the heating tube and a portion of the condensing tube located above the level of the top of 'said inverted U-shaped heating'tube, and ('2) a single outlet-inlet tube for'the closed-system communicating between the upper portion of-the condensing tube and an outlet-inlet valve assembly, said valve assembly comprising a housing enclosing two one-way valves one of which permits discharge of liquid from the outlet-inlet tube by the pressure produced within the heating tube upon vaporization of the liquid therein and the other of which permits drawing of additional liquid from a supply thereof into the system through the outlet-inlet Ltube upon a lowering of the pressure within therpump by condensation of said'vapor in the condensingtu'be.

5. A thermally actuated pump capable of dielivering a liquid under pressure comprising (1) a closed system includin a heating tube provided with means for heating liquid in the tube to a vaporizing temperature, a condensing tube adapted to contain the liquid for condensing vaporized liquid produced in said heating tube and conveyed to the condensing tube, a vapor tube for conveying vapor produced in the upper portion of the heating tube to the upper portion of the condensing tube, and connection means providing liquid communication between the lower portions of the heating and condensing tubes, said connection means being provided with an extended heat-transfer surface such as to permit cooling of the liquid contained therein and thereby limit the rate of heat transfer from the liquid in the heating tube to the liquid in the condensing tube to a value below that at which the liquid in the condensing tube will be heated to a non-condensing temperature in the course of operation of the pump, and (2) valve means associated with the condensing tube adapted to permit discharge of the liquid from the closed system by the pressure produced within the heating tube upon vaporization of the liquid therein and adapted to permit drawing of additional liquid into the tube from a supply thereof upon a low-.

ering of the pressure within the pump by-condensation of said vapor in the condensing tube.

6. A thermally actuated pump capable of delivering a liquid under pressure comprising (1) a closed system including a heating tube provided with means for heating liquid in the tube to a vaporizing temperature, a conde'nsingtube adapted to contain the liquid for condensing vaporized liquid produced in said heating'tube'and conveyed to the condensing tube, a vapor tube for conveying vapor produced in the upper portion of the heating tube to the upper portion of the condensing tube, and connection means providing liquid communicationbetween the lower portions of the heating and condensin tubes, said connection means being immersed'in a supplyof the liquid to be pumped, and (2) "valve means associated with the condensing tube adapted "to permit discharge of the liquid from the closed system by the pressure produced within thehe'ating tube upon vaporization of the liquid therein and adapted to permit drawing of additional liquid into thetube from said supply thereof upon a lowering of the pressure within the pump by condensation of said vapor in the condensing tube.

7. A thermallyactuated pump capable of delivering a liquid under pressure comprising ('1) a closed system including a heating tube provided with means for heating liquid in the tube to a vaporizing temperature, a condensing tube adapted to contain-the liquid for condensing vaporized liquid produced in said heating tube and conveyed to the condensing tube, a vapor tube for conveying vapor producedin the upper portion of the heatin tube to the upper portion of the condensing tube, and connection means providing liquid communication between the lower portions of the heating and condensing tubes, said connection means having a crosssectional area at least about-8 times that of the cross-sectional area of the heating and condensing tubes and having aliquid volume capacity of at least 35% of the liquid volume capacity of the entire closed system, and (2) valve means associated with the condensing tube adapted to permitdischarge of the liquidfrom the closed system'by the pressure produced within the heating tube upon vaporization of the liquid therein and adapted to permit drawing of additional liquid into the tube from a supply thereof upon a lowering of the pressure within the pump by condensation of said vapor in the condensing tube.

8. The method of delivering a liquid under pressure which comprises maintaining a body of liquid in a system having a vaporizing zone and a condensing zone and closed except for a pressure-actuated inlet thereto and a pressure-actuated discharge therefrom, applying heat to the vaporizing zone in an amount suihcient to vaporize liquid therein and to create a pressure on the liquid in other parts of the system sufiicient to cause its discharge through the outlet, conducting the resulting vapor to the condensing zone where it is condensed by contact with liquid therein with resultant reduction of pressure in the system sufficient to cause liquid to flow through said inlet into the system, and cooling the liquid in that part of the system between the condensing zone and the inlet to the vaporizing Zone sufficiently to limit the transfer of heat from liquid in the vaporizing zone to liquid in the condensing zone to a value below that at 11 which the liquid in the condensing zone will be heated to a non-condensing temperature.

9. A thermally actuated pump capable of delivering a liquid under pressure comprising (1) enclosure means defining a closed system including a vaporizing zone, a condensing zone, liquidcommunicating means between the vaporizing zone and the condensing zone, and vapor-communicating means between the vaporizing zone and the condensing zone, the liquid-communicating means having a liquid capacity of at least 35% of the liquid volume of the entire closed system and being capable of limiting the transfer of heat from the vaporizing zone to the condensing zone through the medium of liquid in said liquid-communicating means to a value below that at which the liquid in the condensing zone will. be heated to a non-condensing temperature, (2) heating means associated with the vaporizing zone of the closed system for heating liquid in said zone to a vaporizing temperature, and (3) valve means associated with the closed system adapted to permit discharge of the liquid from the system by the pressure produced therewithin as a result of vaporization of liquid in the vaporizing zone and adapted to permit drawing of additional liquid into the system from a supply thereof upon a lowering of the pressure within the closed system by condensation in the condensing zone of vapors communicated thereto through said vapor-communicating means.

10. A thermally actuated pump capable of delivering a liquid under pressure comprising (11 enclosure means defining a closed system including a vaporizing zone, a condensing zone, liquid communicating means between the vaporizing zone and the condensing zone, and vapor-communicating means between the vaporizing zone and the condensing zone, the liquid-communicating means being provided with an extended heat transfer surface such as to permit cooling of the liquid contained therein and thereby limit the transfer of heat from the vaporizing zone to the condensing zone through the medium of liquid in said liquid-communicating means to a value below that at which the liquid in the condensing zone will be heated to a non-condensing temperature,

(2) heating means associated with the vaporizing zone of the closed system for heating liquid in said zone to a vaporizing temperature, and (3) valve means associated with the closed system adapted to permit discharge of the liquid from the system by the pressure produced therewithin as a result of vaporization of liquid in the vaporizing zone and adapted to permit drawing of additional liquid into the system from a supply thereof upon a lowering of the pressure within the closed system by condensation in the condensing zone of vapors communicated thereto through said vapor-communicating means.

11. A thermally actuated pump capable of delivering a liquid under pressure comprising (1) enclosure means defining a closed system including a vaporizing zone, a condensing zone, liquidcommunicating means between the vaporizing zone and the condensing zone, and vapor-communicating means between the vaporizing zone and the condensing zone, the liquid-communicating means being immersed in a supply of the liquid to be pumped, (2) heating means associated with the vaporizing zone of the closed system for heating liquid in said zone to a vaporizing temperature, and (3) valve means associated with the closed system adapted to permit discharge of the liquid from the system by the pressure produced therewithin as a result of vaporization of liquid in the vaporizing zone and adapted to permit drawing of additional liquid into the system from a supply thereof upon a lowering of the pressure within the closed system by condensation in the condensing zone of vapors communicated thereto through said vapor-communicating means.

NILS ERLAND AF KLEEN,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,745,568 Dienner Feb. 4, 1930 1,773,551 Scott-Snell et a1. Aug. 19, 1930 1,848,226 Scott-Snell et a1. Mar. 8, 1932 2,015,240 Scott-Snell et al. Sept. 24, 1935

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