US2621718A - Pulse jet heater with automatic starting and control system therefor - Google Patents

Description

5,1 2 w. F. KRAUTTER ETAL 2,621,718

PULSE JET HEATER WITH AUTOMATIC STARTING AND CONTROL SYSTEM THEREFOR Filed Dec. '7, 1950 3 Sheets-Sheet 1 INVENTORS WILLY F. KRAUTTER KURT STAIGER WUNIBALD I. E. KAMM lam 4. Au

KRAUTTER ETAL 2,621,718

3 Sheets-Sheet 3 INVENTORS WILLY F. KRAUTTER KURT STAIGER VwBALD I. E AMM BY a, 8N0

A TTO RIVE/ Dec. 16, 1952 w, r-

PULSE JET HEATER WITH AUTOMATIC STARTING AND CONTROL SYSTEM THEREFOR Filed Dec. 7, 1950 Patented Dec. 16, 1952 PULSE JET HEATER WITH AUTOMATIC STARTING THEREFOR AND CONTROL SYSTEM Willy F. Krautter, Kurt Staiger, and Wunibald I. E. Kamm, Dayton, Ohio Application December 7, 1950, Serial No. 199,696

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 6 Claims.

The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to us of any royalty thereon.

The present invention relates to a pulse jet heater havin operatively associated therewith an automatic starting and control system.

Briefly stated the present invention resides in a heater of the pulse jet resonant type and-particularly resides in a starting and control system for such a heater including means to preheat one spot on the wall of the heater combustion chamher in order to ignite afuel-air mixture flowing to the combustion chamber from a vapor generator, thus providing a starting flame in the combustion chamber and a secondary pulsing action which starts the flow of primary fuel into the chamber along with air for combustion. The present invention provides refinements in a heater and control system as described and particularly provides for means to automatically regulate fuel flow to the heater starting components and to terminate fuel flow thereto after the primary combustion process is fully started.

The primary object of the invention is to provide a pulse jet resonant type of heater including a starting system which is entirely automatic, at least as it relates to regulation of fuel flow from a fuel tank to the heater and to the components of the heater starting system,

A further object of the invention is to provide a heater starting system including a float controlled priming device to supply a priming fuel charge to a torch flame unit in response to elevation of a float having a fuel collecting basin thereon and including a fuel regulating valve under control of the float for maintaining an adequate supply of fuel in the float chamber from whence it is free to flow to a primary fuel jet associated with the heater itself.

Another object of the invention is to provide a heater starting system including a float chamber having a flexible wall subject to a static head of liquid fuel and adapted to displace limited quantity of fuel for flow from the float chamber to prime a torch flame unit automatically and including also a float actuated valve adapted to stop the flow of fuel into the float chamber after suflicient fuel has collected therein to provide an adequate torch flame unit priming charge.

Another object of the invention is to provide a pulse jet resonant type heater having a combustion chamber and a primary fuel charging means associated therewith and wherein the combustion chamber is provided with a pressure actuated valve at one point in the wall thereof for communicating pressure to a pressure actuated means adapted to open an escape valve for venting a fuel boiler or vaporizer formin part of the heater starting system, whereby the further flow of fuel vapor therefrom to the heater starting system will be reduced to negligible quantities when combustion of primary fuel is started in the combustion chamber to thereby deenergize the heater starting system.

Another object of the invention is to generally improve the reliability and safety of starting and control systems for heaters of the pulse jet resonant type.

The above and other objects of the invention will become apparent upon reading the following detailed description in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic view of the present pulse jet heater and control system and showing certain components in vertical cross section.

Fig, 1a is an enlarged fragmentary view of the hinge connection for a hollow float shown in Fig. 1.

Fig. 2 is a vertical cross section taken through a preferred embodiment of two of the principal components of the heater starting and control system.

Fig. 3 is a cross section taken through the automatic air and fuel valve mounted within the heater at the lower end of the combustion chamber.

Fig. 4 is a schematic view of the present pulse jet heater and control system and including cerll ainlrefinements not present in the system of For a description of the first or principal form of the inventionreference is made to Fig. l of the drawings wherein the resonant pulse jet heater itself is designated by numeral I. The heater proper includes a vertically arranged combustion chamber 2 of downwardly tapering cross section, and provided with an enlarged rounded dome section 3. At one side near the upper end the chamber 2 has an exhaust pipe or tail pipe 4 connected thereto. The tail pipe is of such length and conflgurationthat it is acoustically tuned to a desired resonant frequency. The length and cross sectional area of the tail pipe with relation to proportions of the combustion chamber will determine the resonant frequency and experiments will soon show the most desirable length for the tail pipe in a given installation. The chamber 2 is fed at one side by a combustion starting conduit 5 and above the conduit 5 is a 3 heating conduit 6 which stops short of the chamber wall whereby a hot blast issuing from conduit 6 first heats one limited area of the chamber wall and then escapes to the atmosphere. Both of the conduits and 6 are part of the heater starting system to be described below. At the lower end of the combustion chamber is an automatic check valve 1 which may have a form as shown in Fig. 3. v

The check valve takes the form of spaced plates 8 and 9 having perforations which are out of register. The plates are maintained in spaced relation by the intermediate ring Ill and between the spaced plates are hemispheres H which rest in perforations of the bottom plate 9 when back pressure in the chamber 2 forces the hemispherical elements ll into flow stopping relation as shown. The plates 8 and 9 are suitably secured, as by welding, to the chamber 2 and to the air and fuel manifold I2 respectively. The manifold I2 is of downwardly tapering construction with a flaring mouth l3 at the lower end into which extends in central relation a fuel feed pipe M to supply a primary fuel flow to the chamber 2. The pulsing action inherent in the present heater construction results in a rapidly recurrent suction effect within the combustion chamber, whereby the air flow induced in the manifold l2 causes liquid fuel to be picked up in successive spurts from the fuel feed pipe 14 for combustion within the chamber 2. The general arrangement and mode of operation of the heater is the same as previously disclosed in our copending applications identified as follows: application Serial No. 129,861 filed November 28, 1949, application Serial No. 144,556 filed February 16, 1950 and application Serial No. 189,876, filed October 12, 1950. The present invention is concerned principally with the automatic starting and control system for the heater device described briefly above.

Fuel is supplied to the feed pipe hi from an adjacent reservoir l5 from which liquid fuel, preferably gasoline or other low gravity hydrocarbon, flows by gravity into pipe it. A hollow float l6 mounted for limited turning movement about pivot I! is adapted to control the position of a fuel control valve [8 slidably situated in a small housing [9 connected by pipe 2i? with the fuel tank 2i. A shut-off valve 22 is employed in the tank outlet line to shut off the heater altogether when desired. The valve l8 which opens the line 20 by dropping below the outlet end of the line 20 is moved to closed position by contact with the upper end portion of the float it when the liquid level in the reservoir l5 rises to a level approximately as shown. At the upper end of the float l6 there is a narrow necked catch basin 23 into which fuel may flow from the lower end of housing I9 when the valve i8 is open and when the float is in a lower position than that illustrated. Above the bottom wall the catch basin has opposite outlet apertures 22 and 25 which are intended for overflow outlets to fill the reservoir [5 and priming pipe 26 respectively. The outlet 25 opens into a groove or channel 25' formed in the upper side of a hinge arm It pivoted at I! in a reservoir side chamber l5. The chamber I5 is connected by the priming pipe 2t to the lower end end of a torch lamp housing 21. In order to force the float l5 downwardly, in case the basin 23 empties without desired initiation of combustion in lamp housing 21, there is provided a spring retracted push rod 23 extending upwardly through the upper end wall of reservoir [5. The float I6 carries a projection 29 for engagement by push rod 28. Thus in cases where it is necessary to refill the basin 23 in order to provide more priming fuel, the float It may be pushed down manually below the floating position shown so that fuel flow may be restarted through pipe 20 and into the basin 23. Then on release of the push rod 28 the float will rise again to the position shown, to spill part of the fuel in basin 23 into priming pipe 25.

After the heater is fully started, the normal function of the float operated valve i3 is the regulation of fuel flow into the reservoir l5 by periodic opening and closing action of the valve as the fuel level in the reservoir fluctuates downwardly and upwardly. The valve it includes a stem at the lower end having considerable clearance with the housing H) to permit fuel flow downwardly. Thus the fuel flows down around the valve stem and is directed thereby, so that when the mouth of basin 23 becomes located just under the stem all fuel flow will gravitate into the basin. After the float rises and flow continues the fuel will finally begin to strike outside the mouth of the basin, to continue filling up the reservoir to a level where final valve closing action will occur. It is clear that this construction, whereby all incoming fuel runs down around the valve stem, provides a definite point where flow into the basin 23 ceases and subsequent flow outside the basin mouth starts for supplying only the reservoir itself. Finally when the reservoir is partly filled as shown the float It will rise sufficiently to raise valve [8 to a point where the conical upper end thereof effectivel stops fuel flow from the feed pipe 29 until such time as consumption of fuel lowers float l6 and reopens valve I8.

The fuel which reaches the bottom of torch housing 21 is absorbed by fibrous wicking material and when a spark is provided therein by operation of magneto 30 the fuel will ignite and burn in the presence of air entering by way of port 3 l. The burning mixture flows up the combustion tube 32 thus heating fuel in the annular fuel vaporizer 33 which is partly filled with fuel by way of conduit or feed pipe 34. Vaporized fuel flows from vaporizer or boiler 33 by way of tube 35 to an enclosed fuel nozzle in the housin 33 supplying a combustible vapor to the conduit 5 for How into the combustion chamber 2 and also supplying vaporized fuel for return flow by way of tube 31 to a fuel nozzle 38 directed up the combustion tube or flue 32. The vapor issuing under pressure from the nozzle then ignites from the flames rising off the priming charge in the bottom of housing 21 and the burning vapors follow the tube 32 up to the flame directing tube 6 terminating adjacent to the combustion chamber wall. Additional air may be admitted to the combustion tube 32, as at 32, to further intensify the torch flame. The wall of chamber 2 now develops a hot spot to cause combustion to start as fuel vapors flowing in tube 5 reach the chamber. The limited supply of fuel is now capable of starting a resonant pulse jet action in the chamber, which causes an alternating rise and fall of pressure in the chamber 2. The effect of this pulse jet action is to cause primary fuel and air to flow periodically up the manifold l2 and into the combustion chamber 2, thus starting the pulse jet heater in steady operation. The constructional details of the heater starting components will be described below (see Fig. 2). It is noted however that a simple ball check valve 39 serves to prevent return flow of fuel in the feed pipe E i once the pressure in vaporizer 33 increases appreciably.

Further included in the starting and control system of Fig. 1 is a pressure control valve assembly 40 connected between the vaporizing chamber 33 and the vent tube 4! at the upper side of fuel tank 2!. The assembly 43 comprises a float chamber 42 connected at its lower end by tube 43 to the upper end of vaporizing chamber 33. A valve seat element 44 at the upper end of chamber 42 is connected by tube 45 to the tank vent tube 4|. Pivotally mounted within the chamber 42 is a flap valve 46 connected at one end to a float 41' depending therefrom and biased to valve closing position by means of a light spring 48. The spring force is adjustable by means of a threaded adjusting screw 43 having a grip portion 50 outside the float housing.

The pressure control valve is so adjusted that fuel in liquid form is required to close the valve 46 by causing the float 41 to be elevated to the position shown. This condition will come about when the vaporizing chamber 33 is almost filled and vapors flowing up the tube 33 are so cooled on their way'to the float chamber 42 that they condense and cause the float 41 to be lifted. It should be understood that filling of the chamber 33 above normal limits provides such a volume of liquid therein as to lower the average fuel temperature and particularly lower the fuel ternperature near the outside wall of the chamber 33. Thus the vapors flowing up the relatively long tube 43 will condense to liquid form and cause upward action of float 41. This action closes valve 46 and gradually increases the pressure in chambers 42 and 33 to cause firm seating of ball valve 39, thus preventin more now of fuel into vaporizing chamber 33 until the surplus fuel is vaporized. Float chamber 32 should be above vaporizing chamber 33 in order to allow condensate to drain back into the chamber 33.

The pressure control valve is further operative to correct a low level fuel condition in vaporizing chamber 33. Considering the chamber 33 with only a small amount of liquid fuel therein it is seen that the superheated vapors now flowing up the tube 43 will flow past the float 4? without condensing sufliciently to cause lifting of the float to its valve closing position. Thus the vapor will flow on to the fuel tank 2i by way of tube 45 and gradually condense by the time the tank is reached. Therefore the pressure in the vaporizing chamber 33 will be kept down, so that the static head of fuel in tank 2! can lift the ball valve 39 and refill the vaporizing chamber 33 at least to near normal levels.

Considering now the preferred construction of the starting system components reference is made to Fig. 2. The torch housing 2? is preferably made of two sections El and 52 of cylindrical form assembled in telescopic relation and welded together at their overlapping margins. Secured interiorly of the upper housing section 5! in concentric relation thereto is a chimney or combustion tube 32 having a flared mouth at the lower end and having a diverging annular wall thereabove. Between the tube 32 and the housing section 5! is an annular space 33 providing a fuel space wherein fuel may be heated and vaporized. Vaporized fuel may escape by way of the control tube 33 to the pressure control valve assembly 39. The main flow of vaporized fuel is by way of the tube 53 having its upper end opening at 54 into the fuel space 33 and having an intermediate portion passing 6 through the wall of tube 32 at 55 and continuing along the inside of the wall below the housing section 5| to finally pass through the wall of housing section 52 and 55. The tube continues into the adjacent nozzle housing 36, with the lower end of the tube secured into the nozzle 51 below the outlet thereof. Farther below the nozzle outlet a second tube 31 connects the interior of nozzle 51 with the interior of nozzle 38 located centrally within the torch housing 21.

Returning now to the torch unit or housing 2'! it is noted that the fuel supply conduit 34 connects with the fuel chamber 33 by way of a ball valve 39 having a gravity-seated ball element 39' therein. Vapor pressure in the chamber 33 is adapted to close the ball valve against the static head of liquid fuel in the fuel tank and fuel supply line. 52 includes an inspection door 58 for viewing the flame and also for lighting the fibrous Wicking 39 by a match in case the spark plug 60 fails to cause ignition. The wicking 59 is supplied with fuel through the priming pipe 23, as previously described. An aperture 3| in the wall of housing section 52 supplies air for combustion of fuel therein, as well as combustion in the upwardly extending chimney 32. The fuel nozzle 38 is threaded into a tubular housing 6| welded or otherwise secured on the bottom wall of torch housing section 52, with the nozzle 38 extending into the housing section centrally thereof. The nozzle 38 has a flow governing needle valve 62 slidable therein and guided by a bushing 63 threaded into the lower end of the nozzle 38. A coil spring 64 tends at all times to open the needle valve. It is noted that a narrow passage 63 in the bushing 63 transmits pressure developed within the nozzle to a bellows 65 secured at its upper end to the bushing 63. The lower end of the bellows is secured to a disk 66 forming an abutment for the lower end of needle valve 32. The bellows is biased toward a collapsed condition by a compression spring 61 extending between the disk 66 and the bottom Wall of housing 6|. An aperture 68 in the bottom wall admits atmospheric pressure into the housing BI and an adjustment screw 69 threaded through this same wall acts as a limiting abutment or stop for the disk 66 and thus determines the maximum amount of opening for the needle valve 62. The setting of the screw 63 may be fixed by means of a locknut 39'.

The torch flame lamp including housing 2'! and parts therein acts to produce a hot spot on the wall of combustion chamber 2. This in turn acts to fire a stream of combustible vapors passing along conduit 5 into the combustion chamber. The vapors are produced by a combustion starter or vapor metering device included within the housing 36. The housing itself comprises a cylinder 10 having a bottom wall H apertured at T2 to admit atmospheric pressure. The upper end of the cylinder is outwardly and upwardly flanged, as at 73, to receive a cup-like top wall member 14 opening upwardly and receiving therein a fitting l5 welded, brazed or otherwise secured rigidly within the upper end of the member 14. A series of holes 16 arranged in I circular manner pass through the fitting l5 and an upward tubular extension 1'! on the fitting receives the vapor tube 5 and is secured thereto as at 11'. The lower end of the fitting 15 provides a downwardly facing valve seat against which is seated a circular valve element 78 of rubber or other resilient material. A group of valve control The lower housing section rods 19 support the valve element 18 and are 'slidably "mounted in short tubular guides 83 welded in the lower wall portion of the member 14. At their lower ends the rods 19 support a ring 8| having two interfltting and threaded elements 82 and 83 mounted centrally therein. Each of the rods 19 carries a Washer or flange l9 near'its lower end serving as an abutment for a light compression spring 84 extending downwardly to contact the ring 8|. The upper threaded element 83 is hollowed out to slidably receive the lower headed end of a needle valve element 85, so as to allow limited movement of the element 85 with respect to the elements 32 and 83 and the ring 81. Encircling the element 83 and fixed thereto is a bellows 86 having its upper end fixed to a threaded nipple 87 within which is guided the needle valve element 85. A narrow groove 8'! internally of the nipple Bl transmits pressure within the hollow nozzle to the interior of the bellows 85. As may be seen in the drawing, the nipple or bushing El is threaded into the lower end of the nozzle El. A light coil spring 83 surrounds the needle valve element 85 near its lower end and has its opposite ends abutting the bushing {3i and an annular shoulder 89 above the headed lower end of valve element 85. The lower limit of the assembly 8 I-83 is determinedby an adjustable stop member 90 threaded into the wall H and maintained in adjusted position by a locknut 33. The assembly Bl83 is biased away from the wall H by means of a compression spring 8!.

Operation The heater and starting system as shown in Figs. 1 to 3 forms a complete and emcient apparatus to burn liquid fuel, such as gasoline, in a chamber from whence the hot products of combustion may flow by way of an exhaust pipe for space heating, for warming up machinery and engines in cold climates or for heating living quarters by the use of a heat transfer unit through which the hot gases from the heater are passed. To start the apparatus after filling the fuel tank 2|, the operator must turn on the fuel valve 22. Fuel now gravitates to the fuel reservoir by way of pipe 29 and to the fuel vaporizer 33 by Way of pipe 34 and ball valve 39. When fuel first flows down the pipe 23 and past valve l8, the float I6 is down in a level position and the first fuel enters the catch basin 23 on top of the float. As it reaches the overflow hole 23 the fuel runs out to start filling the reservoir 15 and feed pipe I4. As the reservoir becomes partly filled the float rises and begins to spill fuel outvof the hole 25, part of which runs into the reservoir and part of which runs over the hinge arm l3 and. into the side chamber l5 and pipe 2'6. As the float rises farther the flow of fuel down the stem of valve I8 falls outside of the catch basin 23 and fills the reservoir It: to a level where the valve I8 is closed, as in Fig. 1. The float I6 having tilted still farther, more fuel flows into side chamber l5 and by way of pipe 23 to the bottom of housing 21. Now the operator turns the magneto 33 to fire the torch flame unit, whereupon flames rise from the wicking 59 to start heating the fuel in the vaporizing chamber 33. As the fuel heats up, the vapor generated in the chamber 33 flows down the tube 35. The tube includes a portion 53 within the combustion tube 32 whereby the vapor is superheated to prevent excessive condensation on the way to the fuel nozzles.

The vapor pressure in the nozzles 51 and 33 now develops to cause opening of the needle valves and 52 by actuation of the bellows 85 and (55. Since the torch flame at nozzle 38 should start before vapor is allowed to escape from the nozzle 51, the spring 3'! opposing expansion of bellows 65 is made more responsive than the spring! under the bellows 86. For example the needle valve 62 in nozzle 38 may be made to open at a vapor pressure of 25 p. s. i. and the needle valve 85 in nozzle 5'! may be made to open at a vapor pressure of p. s. i., these responses being determined by the relative strength of springs 61 and 5H. It may now be assumed that the needle valve 82 has opened after expansion of bellows 65 and corresponding downward movement of the disk 66, which determines the position of the needle valve in conjunction with the valve biasing spring 64. The vapor flowing from the nozzle 38 now ignites by reason of the flames rising off the wicking 59, thus starting a substantial torch action up the combustion tube 32 to cause a hot spot to form at one point on the combustion chamber wall. Furthermore the fuel in vaporizing chamber 33 now heats up still more to increase the vapor pressure at the nozzles 51 and 38. As the pressure in bellows :36 increases the member 83 moves along the lower end of the needle valve 85 from the original position adjacent to flange 83 to the position shown (Fig. 2). The needle valve remains closed during this portion of the bellows expansion, in spite of the spring 88, because the upper end of the needle valve is subject to atmospheric pressure while the lower end is subject to very substantial positive pressures. It is understood of course that the upper'pointed end of the needle valve is tight- 1y engaged in the conical opening at the upper end of the nozzle 51. Now as the bellows expands still more, the member 83 at the lower end of bellows 86 acts to positively 'open the needle valve 85 whereupon the excess downward force caused by spring 88 snaps the valve open and allows full flow of vapor from the nozzle 5'5. The position of the needle valve as shown in Fig. 2 corresponds to the condition where the Valve has just been positively moved away from its contact with the conical valve seat but has not yet snapped fully open to a position where the flange 83 will contact the upper end of member 83. As the valve is opened slightly to the position shown. the fluid pressure will become the same on all surfaces thereof and the coil spring 88 will have the desired effect of causing sudden full opening of the valve. As the bellows 83 expanded it also caused the rods ii] to move downward slightly and thus the air valve it opens sufficiently to allow flow of air through passage H3. The air and fuel vapor mixture now flows into the combustion chamber 2 by way of tube 5 where the mixture ignites, due to the presence of the hot spot on the chamber wall. The initial explosion of the fuel and air in the chamber 2 is followed by a condition of low pressure whereby fuel and air start flowing up the manifold l2 to start the pulse jet action of the heater. The steady flow of fuel vapor from the nozzles 5'! and 38 soon lowers the vapor pressure to a point where both needle valves 85 and 62 close and the starting system ceases to function until the next start. Fuel continues to flow steadily into the fue1 feed pipe M from the reservoir E5, the float l5 acting to open and close the fuel valve 13 to keep a maximum amount of fuel in the reservoir 15. The slight up and down movement of the float 56 will 9. not. be suffic'ient to .let any fuel into the basin 23, therefore the wicking 59 in housing 21 will not be supplied with any additional fuel until the reservoir I5 is emptied or until the float I6 is pushed down by means of the push rod 28. To stop the pulse jet heater it is merely necessary to close the main fuel valve 22, whereupon the fuel remaining in the reservoir I5 is used up entirely by normal flow through the feed pipe Modified fuel control system The modifiedfuel control and starting system of Fig. 4 is shown in association with a pulsejet heater of the resonant type, including a combustion chamber 2', an exhaust pipe 4', inlet valve I and inlet manifold I2 all exactly similar to corresponding elements as previously described. Fuel and air flows through the manifold I2 and automatic valve 1 just'as in the principal form of the apparatus and the fuel issues into the manifold from the feed pipe 94 supplied by gravity with liquid fuel from the reservoir 05, in which is pivotally mounted a float 95 turning aboutthe pivot 31. A valve element 98 is reciprocably mounted in a small cylinder 99 on the upper wall of the reservoir 95. Thus the float is adapted to'open and close the va ve 98 as the fuel level in'the reservoir falls and rises to thus maintain a constant fuel quantity in the reservoir. In order to vent the reservoir 95 to allow atmospheric pressure on top of the fuel, there is provided a tube I extending from the reservoir to the vent tube M on top of fuel tank 2I'. Fuel is supplied to the reservoir 95 by way of the fuel feed pipe IOI having a fuel shut-off valve 22' interposed therein close to the tank. Fuel flowing in pipe If is also under control of the thermostatically controlled valve I02, so that fuel'flow to the reservoir 95 is not started until the hot spot on the chamber wall at the conduit 6' is well developed. The valve I02 includes an actuating arm I03 connectedby a rod I04 to a pivoted arm I05 actuated by a bimetal ic element I00 in a small housing I01 open at one end to the combustion chamber 2. The outer surface of the housing I01 may be coated with an insulating layer, as shown.

The heater starting components including housings 21' and 36' are exactly similar to those shown in Fig. 2, except that the vapor flow tube 35" is arrangedin a coil 35" within the vaporizing chamber 33'. of-the torch flame unit extends to a nozzle-like element 6 which stops short of the combustion chamber wall. A check valve I I I is interposed in the vapor flow tube 35 in order to prevent vapor flow to the fuel nozzles until there is sufficient pressure developed to provide an effective flame at nozzle 38' of the torch flame unit. Fuel flow to the vaporizing chamber 33' is by way of pipe I 0| branch pipe H2 and ball check valve II3. Possible fuel condensation or leakage into the lower portions of housings 2'! and 36' is drained away by pipes H4 and I I5 into the drain pipe I I6. The pipe I I5 also includes a branch extending to the bottom of a drip pan II'I under the outlet end of fuel feed pipe 94 and also under the flared mouth of manifold I2.

Priming fuel for the wicking in the torch flame unit may besupplied by a pipe I I8 and fuel may be supplied manually through a funnel I I 9. However the preferred manner, is through the action ofa special fuel feed component I20. .The ,device I20 includes a two-part housing I2 I. and .between the two parts thereof a ,highly flexible As before the combustion tube I I0 10. diaphragm I22 is provided. The pipe I23 extends from the fuel pipe IOI to the upper side of the housing I2I, while a similar pipe I24 extends from the fuel pipe IM to the lower side of the housing I2I. At the point where the pipe I24 enters the housing there is a restriction I25, to give a delayed action in elevating the diaphragm after the upper part of the housing has filled with fuel and the float I25 has risen to cause the valve element I21 to close off the pipe I23. Now with the upper part of the housing partly filled with fuel, the static pressure on the lower side of diaphragm gradually forces it upward to displace some fuel for flow throughthe housing extension I28 and thence down the feed pipe I I8 to the wicking in housing 27'. It is understood of course that the upper part of the housing I2I will not usually fill quite up to the level of housing extension I20 before the valve element I21 closes off the feed pipe I23. Subsequent raising of the fuel level in the upper part of the housing I2I is accomplished by pressure which develops slowly as fuel enters the pipe I24 and moves through the choke I25. As the fuel level in the upper part of the housing 7 IZI is raised the valve I21 becomes more'firmly seated and no further influx of fuel occurs until the next time the system is started by turning on the main fuel valve 22.

In the present heater. control system there is provided a pressure control valve unit I30 associated with the torch flame unit for controlling the fuel level therein and also for venting accumulated air found therein, especially when it is time to start up the heater. As in the system of Fig. L'the pressure control valve I30 includes a housing I3I having a float I32 slidably mounted therein. The walls of the float may be of ribed or fluted construction to minimize frictional resistance to'float movement. The upper end of the float is'cone-shaped to provide a valve element I33 adapted to close a valve seat inside the housing at the lower end of tube I34 extending to the fuel tank vent 4I'. Such closing action will not occur until there is sufficient liquid fuel accumulated in the housing I3I to cause lifting action of the float I32. Fuel vapor, air and liquid may enter the lower end of housing I3I byway of the inlet tube I35 extending from the upper end of the fuel vaporizing chamber 33'. The passage of air or fuel vapor into the housing I3I has little effect on the float I32, since such gaseous flow is merely vented by way of the tube I34 to the fuel tank vent 4|. Thus the pressure control valve I30, as well as the similar valve 40 in Fig. 1, acts to de-aerate the fuel vaporizing chamber as the fuel and fuel vapor displaces accumulated air which enters the chamber'when the system is shut down.

Another feature of the valve I30 is the float control device I36 comprising a two-part housing having a diaphragm I31 secured between the two parts of the housing. The housing section nearest to the control valve I30 is provided with a mounting arm or bracket I30 fastened on one side of the float housing I3I. A push rod I30 fixed to the diaphragm I 31 extends into the housing I3I to actuate the float I32 when pressure on the upper side of diaphragm I31 exceeds the pressure on the lower side thereof. The lower side of the diaphragm is exposed to atmospheric pressure becauseof holes in the lower part of the diaphragm housing. The upper side of the diaphragm is exposed to the pressure of the combustion chamber 2', such pressure being communicated by way of tube I40 and check valve Ml. As soon as resonant combustion is established the pressure rise will cause actuation of the push rod I39 and float I32 will be forced down. This will help to lower the vapor pressure in the chamber 33 more quickly, so that the starting system will cease operation by closing of the fuel nozzles in the torch flame unit and the heater starting unit of Fig. 2.

Operation of modified fuel control system In general the operation and use of the modified system shown in Fig. 4 is the same as in the previously described system. The combustion chamber, torch flame unit and heater starting unit are almost identical in construction and arrangement in both forms of the apparatus. The auxiliary control units are somewhat different and in Fig. 4 the control units are more numerous in order to offer the ultimate in automatic control of the present type of heater.

In order to start the heater, the fuel valve 22' is first turned on. Fuel will not flow past the thermostatically controlled valve [32, since the control element I is cold. However fuel will flow through branch I23 and partly fill the upper part of housing H21. Fuel flow will stop as the float I26 rises to close the outlet end of branch pipe 123. Fuel pressure will gradualy cause a pressure build-up below diaphragm I22 to lift the diaphragm and displace some fuel into the housing extension I28 and thence down pipe I It to the wicking in the bottom of torch flame unit 21'. The fuel vaporizing chamber 33 will also fill up at least part way by way of the branch pipe H2. Now the fuel absorbed by the wicking in the torch flame unit is ignited by a match or by means of a spark plug 60 (see Fig. 2). The fuel in chamber 33 is now vaporized by the heat of the burning fuel rising up along tube I l9, and the fuel vapor will flow by way of tube 35', valve I H and tube 3i to the nozzle 38'. Now the vaporized fuel will begin to issue from the nozzle 38 as the pressure rises sufficiently to retract the needle valve within the nozzle. A torch flame now flows up the tube I I!) to develop a hot spot on the combustion chamber wall and to further vaporize fuel in chamber 33. When the vapor pressure rises sufliciently the fuel nozzle in the heater starting unit 35 opens to start a flow of fuel vapor to the combustion chamber. the hot spot has been developing in the meantime the thermostatic control will have heated sufiiciently to open valve I02 and permit flow of liquid fuel to the reservoir 95 and to the fuel feed pipe 9d. The fuel vapor flowing in the tube 5' will fill up the combustion chamber and will fire from the hot spot on the chamber wall. The sudden drop in pressure in the chamber after the first explosion will cause some air and fuel to be sucked in by Way of the automatic air-fuel valve 1. This new charge will fire and the resonant pulse jet action will begin. Since the vapor pressure in chamber 33' will now be reduced to a very low level, the nozzles in the torch flame unit and heater starting unit will close to put the starting apparatus out of operation. Since the pressure developed in the combustion chamber 2 will maintain the vapor escape line I35 open by reason of the diaphragm l3! and push rod I39, any temporary vapor pressure in the chamber 33' due to residual heat will be vented to the tank vent 4| The pulse jet heater will now continue in operation as long as fuel is supplied by way of the pipe I01 and reservoir 95.

The embodiments of the invention herein shown Since 12 and described are to be regarded as illustrative only and it is to be understood that the invention is susceptible of variations, modifications and changes within the scope of the appended claims.

We claim:

1. In a pulse jet heater of the resonant type including walls forming a combustion chamber provided with an air-fuel inlet, a fuel control and starting system comprising, a fuel tank, conduit means to conduct liquid fuel from said tank to said air-fuel inlet, a torch flame unit near said combustion chamber and including a housing and connected combustion tube extending upwardly to a point near to but just short of the wall of said combustion chamber, means forming a fuel vaporizing chamber in heat transfer relation with respect to said combustion tube, a first fuel nozzle inv said torch flame unit, a first spring actuated means normally closing said first fuel nozzle, a heater starting unit near said torch flame unit and including a housing and connected tube extending into said combustion chamber, a second fuel nozzle in said heater starting unit, a second spring actuated means normally closing said second fuel nozzle and exerting more closing force than said first spring actuated means, means to supply vaporized fuel to the interior of said second fuel nozzle and to the interior of said first fuel nozzle from said fuel vaporizing chamber, and first and second pressure responsive means subject to the fuel vapor pressure to open said first and second fuel nozzles respectively.

2. In a pulse jet heater of the resonant type including walls forming a combustion chamber provided with an air-fuel inlet, a fuel control and starting system comprising, a fuel tank, conduit means to conduct liquid fuel from said tank to said air-fuel inlet, a torch flame unit near said combustion chamber and including a housing and connected combustion tube extending upwardly to a point near to but just short of the wall of said combustion chamber, means forming an annular fuel vaporizing chamber within said housing and around said combustion tube, conduit means to conduct liquid fuel from said tank to said fuel vaporizing chamber, a first fuel nozzle in said torch flame unit, a first spring actuated means normally closing said first fuel nozzle, a heater starting unit near said torch flame unit and including a housing and connected tube extending into said combustion chamber, a second fuel nozzle in said heater starting unit, a second spring actuated means normally closing said second fuel nozzle and exerting more closing force than said first spring actuated means, means to supply vaporized fuel to the interior of said second fuel nozzle and to the interior of said first fuel nozzle from said fuel vaporizing chamber, a first pressure responsive means connected with the interior of said first fuel nozzle to open the nozzle at a first predetermined vapor pressure, and a second pressure responsive means connected with the interior of said second fuel nozzle to open the nozzle at a second predetermined vapor pressure greater than said first predetermined pressure.

3. In a pulse jet heater of the resonant type including walls forming a combustion chamber provided with an air-fuel inlet, a fuel control and starting system comprising a fuel feed pipe and nozzle extending to a point within said airfuel inlet, means for feeding liquid fuel to said fuel feed pipe including a float chamber, a pivotally mounted float in said float chamber, a

fuel inlet valve movably mounted above said float and adapted to be closed by said float as said float is raised by partial filling of said float chamber, a torch flame unit near said combustion chamber and including a housing and connected combustion tube extending upwardly to a point near to but just short of the wall of said combustion chamber, wicking in said torch flame unit housing, means to admit air to said torch flame unit housing, a priming conduit extending from said float chamber to the wicking in the torch flame unit housing, and means on said float to collect liquid fuel and divert at least part of the collected fuel to said priming conduit upon tilting of said float as said float chamber starts to fill.

4. In a pulse jet heater of the resonant type including walls forming a combustion chamber provided with an air-fuel inlet, a fuel control and starting system comprising, a fuel feed pipe and nozzle extending to a point Within said air-fuel inlet, means including a fuel tank for feeding liquid fuel to said fuel feed pipe, a torch flame unit near said combustion chamber and including a housing and connected combustion tube extending upwardly to a point near to but just short of the Wall of said combustion chamber, wicking in said torch flame unit housing, means to admit air to said torch flame unit housing, a priming unit including a housing divided by a movable wall element, conduit means to supply liquid to both sections of the divided housing from said fuel tank, means to conduct fuel from an overflow pipe connected with one of said divided housing sections above the other section to said wicking, and choke means in the conduit means leading to said other section in order to retard application of maximum pressure on said movable wall element.

5. In a pulse jet heater of the resonant type including walls forming a combustion chamber provided with an air-fuel inlet, a fuel control and starting system comprising, a fuel tank, conduit means to conduct liquid fuel from said tank to said air-fuel inlet, a torch flame unit near said combustion chamber and including a housing and connected combustion tube extending upwardly to a point near to but just short of the wall of said combustion chamber, means forming an annular fuel vaporizing chamber within said housing and around said combustion tube, conduit means to conduct liquid fuel from said tank to said fuel vaporizing chamber, a fuel nozzle in said torch flame unit, means to conduct vaporized fuel to said fuel nozzle, a pressure control unit including a housing enclosing a float and float actuated valve means, conduit means extending from the upper wall of said fuel vaporizing chamber to said pressure control unit housing, and a vapor escape conduit controlled by said float actuated valve means and communicatively extending from an upper portion of said pressure control unit housing to an upper portion of said fuel tank.

6. In a pulse jet heater of the resonant type including walls forming a combustion chamber provided with an air-fuel inlet, a fuel control and starting system comprising, a fuel tank, conduit means to conduct liquid fuel from said tank to said air-fuel inlet, a torch flame unit near said combustion chamber and including a housing and connected combustion tube extending upwardly to a point near to but just short of the Wall of said combustion chamber, means forming an annular fuel vaporizing chamber within said housing and around said combustion tube, conduit means to conduct liquid fuel from said tank to said fuel vaporizing chamber, a fuel nozzle in said torch flame unit, means to conduct vaporized fuel to said fuel nozzle, a pressure control unit including a housing enclosing a float and float actuated valve means, conduit means extending from the upper wall of said fuel vaporizing chamber to said pressure control unit housing, a vapor escape conduit controlled by said float actuated valve means and communicatively extending from an upper portion of said pressure control unit housing to an upper portion of said fuel tank, and pressure responsive means connected by a pressure sensing tube to said combustion chamber for opening said float actuated valve means when resonant combustion is started in said combustion chamber.

WILLY F. KRAUTTER.

KURT STAIGER.

WUNIBALD I. E. KAMM.

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

UNITED STATES PATENTS

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