US2531741A - Apparatus for flame cultivation - Google Patents

Description

Nov. 28, 1950 A. w. PECK 2,531,741

APPARATUS FOR FLAME CULTIVATION Filed April 8, 1946 2 Sheets-Sheet l INVENTOR.

A.W. PECK ATTORNEY Nov. 28, 1950 A. w. PECK 2,531,741.

APPARATUS FOR FLAME CULTIVATIQN Filed April 8, 1946 2 Sheets-Sheet 2 FILLER 44 5e EQUALIZING VAPOR 2| I LIQUID VALVE VALVE WITHDRAWAL REGULATOR 46 RELIEF LINE I 48 VALVE 45 C.P 43 3 I I6 I VAPORIZER V 39%, I /22 49 l NEEDLE l9 TANK LIQUID BY-PASS 4| vALvE I WITHDRAWAL I LINE 24 I u EXHAUST I PIPE 34 27M 27 34 47 'g 23 TO 34 BURNERS INVENTOR.

AjWL PECK wag ATTORNEY Patented Nov. 28, 1950 APPARATUS FOR FLAME CULTIVATION Alvin W. Peck, Springdale, Ark., assignor to Phillips Petroleum Company, a corporation of Delaware Application April 8, 1946, Serial No. 660,579

4 Claims. (Cl. 47 1) This invention relates to flame cultivation. In one of its more specific aspects it relates to an apparatus for practicing flame cultivation and in 'a still more specific aspect it relates to a burner and shield assembly for use on flame cultivators. Flame methods for the destruction of weeds have gained in usage in the cultivation of certain crops as a substitute for or in conjunction with plow methods. Flame weeding has marked economic advantages over hand labor methods, as for example, in cotton, sugar cane or even in corn fields. In times of labor shortage other advantages become apparent. It is for the purpose of further extending the use of flame methods for weed killing or cultivation that my invention is mainly directed.

Distillate oils, such as light distillates or kerosene, which are suitable for use as tractor fuel, have been used as burner fuels in flame cultivators. Liquefied petroleum gases, such as propane, may also be used as burner and/or tractor fuels. The use of such volatile liquids for burner fuels offers many advantages over the use of the heavier fuel oils.

One object of my invention is to provide a flame shield for use on flame cultivators.

Another object of my invention is to Provide a flame shield or hood for use on flame cultivators in which the flame and hot combustion products are retained adjacent the ground for a longer period of time than when such shield or hood is not used.

Another object of my invention is to provide a shield or hood for confining the severe action of a flame to an area adjacent the ground and for simultaneously preventing too intimate contact of hot combustion gases with aerial foliage of plants being cultivated until these gases have been somewhat cooled.

Yet another object of my invention is to provide a hood or retaining element adapted to receive flame and hot gases therefrom and retain same adjacent the ground for such a period of time as required to destroy vegetation.

A further object is to provide proper flame sizes for flame cultivation with liquid petroleum gas fuel.

Still another object of my invention is to provide a heat retaining element adapted to receive flame and combustion gases therefrom after passage through a row of crop plants and retaining the hot gases adjacent the ground between crop rows for such a period of time as required to destroy vegetation or vegetation and insects found near the ground and yet to protect aerial foliage of the crop plants being weeded.

And still another object of my invention is to provide a protective hood .for receiving :a burner flame after the latter has passed through a row of crop'plants; the burners, and protective hood or hoods being mounted on a tractor orother vehicle for passing along a row or rows of crop plants.

Many other objects and advantages will be apparent to those skilled in the art from a careful study of the following description and attached drawing which respectively describes and illustrates a preferred embodiment of my invention.

In the drawing Figure 1 is a diagrammatic plan view of the flame cultivator assembly.

Figure 2 is a detailed view of the fuel containing and piping apparatus.

Figure 3 is a plan view of the protective hood.

Figure 4 is an end view of the protective hood.

Figure 5 is a side view of the protective hood.

Figure 6 is an elevation showing the relative arrangement of the hoods, burners and flames with respect to the crop rows.

Referring to the drawing and specifically to Figure 1, the reference numeral ll refers to :a tractor assembly having as main parts, a frame 12, two front guide wheels 13, two main drive wheels M, a power plant IS, the latter being an internal combustion engine having among other auxiliary" parts an exhaust pipe I6, a steering apparatus I1, a seat IS, a liquid fuel tanklS, a fuel line 20, a constant pressure outlet valve 2 I, a fuel vaporizer 22, vapor fuel line 23 to a carburetor 25, a vapor fuel line 24 to a manifold header pipe 26, service gaseous fuel tubess2'l, burners 28 and hood protectors 29, two supports 30 supporting a cross member 32 to the main axle and some connectors 33 which hold. the hood protectors 29 in fixed relation with the cross member 32. Each of the individual burner fuel tubes 21 is equipped with a manually operable needle valve 34.

The liquid fuel storage Ill-pressure reducer 2l-f uel vaporizer 22 assembly identified broadly by reference numeral 35 is shown more in detail in Figure 2. In this figure may be easily identified the liquid fuel tank IS, the fuel line 20, the constant pressure outlet valve (liquid regulator) 2|, a liquid fuel line 36, a vapor fuel line 31, the vaporizer 22, gaseous fuel line 24, the gaseous fuel header pipe 26, and the individual burner fuel tubes21. Each of the latter service tubes 21 carries a needle valve 34. A by-pass line 38 when valve 39 is open and valves 4|! and 4| are closed, cuts out the vaporizer 22. The vaporizer 22, as illustrated but not limited thereto, may be an exhaust pipe heat exchanger in which hot exhaust gases passing through the exhaust pipe 16 give up heat for vaporization of liquid fuel inside the jacket 42.

The fuel tank 19 is fitted with a filler valve 43 and a filler tube 44 and a pressure equalizer valve 45. A relief valve 46- is also provided for safety purposes. Y

Then on referring to Figures 3, 4 and which show the plan view, end view and side view respectively, of the protective hoods, these members may be constructed around a main ridge row tube or rod member 5| having downward sloping side plates 52 on either side. These sloping side plates terminate at the top of vertically disposed side walls 53. The rear end 54 of the hood is straight across, the ,middle ridge row member 5|, the side plates 52 and side walls 53 all terminate in a single vertical plane. The front however, has a streamlined appearance, the .--ri dgB:row,-memberextending forward some .dis- "tance as .the couplings 3,3 to connect with the press member 32 shown in-Figure 1. The lower edge of each vertical side .wall is cutaway as shown in Figure .5 and a runner :member 55 attached as shown, similar somewhat .to a sled runner. However, I have found it preferable to attach the runner :to .the :Side in such a :manner that no part of the runner iextends horizontally outside of the side walls :53. By this arrange- :ment'there is no tendency for :the runnerimemhas to damagetheplants in'the crop row as the apparatus travels down the rows of plants being "Needed.

Understructure or framework for the hood 11 .9416 found .may be of substantially any desired design, the main requirement'being that the .hood be strong and sturdy andablexto withstand mechanical shock as well as heat from .the burners.

.Qn :referring to the apparatus and elements shown in Figure '2, the tank l9 may b of any construction desired provided it be sufficiently strong to hold such. a:liquid fuel as forexample, .liquid propane. andxtmstoresucha material at atmospheric pres- ;Sure requires a substantial pressure. This com- ;poundhasa vapor pressure ofabout 180 pounds per square inch at 190. F. and accordingly to maintain this material at this temperature re- ,quires 'a storage tank pressure of this value. or ,course the higher the temperature the greater will be :the tank pressure, so that in the summer sun some higher pressure than 180 pounds per square inch will exist in propane-storage. I have found that a tank of 60 to '75 gallons capacity serves to hold suificient liquid propane to operate :a a-burner flame cultivator without too frequent need for refilling. The relief valve 46 is adapted to pop oif or to vent gas when the tankpressure exceeds a predetermined value, as for example 250 lbs. This pressure will be developed by propane at about 126 F.

For filling the cultivator tank with-propane the filler valve 43 and tube 44 are providedthe outer end of tube t4 beyond the valve 43 is connected with a tube from the propane storage tank, not

shown, and the equalizing tube 561s connected withatube leading to the vapor space above the liquid propane in the above mentioned propane storage tank, not shown. Thus when liquid propane enters the cultivator tank [9 through tube '44 vapor will be displaced by the liquid and said vapor will pass out through the equalizing valve 45 and equalizing line 155 into .the main propane Propane boils Wellbelow 0 F. 1

storage tank. In this manner as propane liquid enters the tractor tank l9 pressure will not build up therein due to compression of the vapor.

The hoods 29 are preferably constructed in such a manner as to leave a side opening through which the burner may direct its flame for rapid disposal after it has served its main purpose. This opening is identified in ihfgures 5 and 1, reference numeral 57. In Figure 5 the void space or open spot in the side wall is clearly visible while in Figure l the purpose of this open or cut away portion appears obvious.

As illustrative, I have shown a 2-row cultivator which is adapted to cultivate or destroy weedscompletely from two rows of crop plants, the ground between the two rows and the ground between each of the two rows being cultivated and adjacent rows.

By reference to Figure 1, flames from the burners mounted on the outer hoods are directed through :the rows of crop plants and under the :front portion of the middle hood for disposal. .In likemanner the two'burners mounted in 'front of "the center hood point/outwardly and direct their respective :fiames through "the two rOWs of .crop plantsin directions oppositeirom thefiames -from:the outer burners and under the respective outer hoods. Thus, the crop row St "has flame passing through it from left *to right and from .right to'left and in like manner'thecrop row 52 has flames passing through it in both directions. This flaming operation may be further clarified on reference toi-Figure 'fi which illustrates, in elevation, the arrangement of the burners, the

hoods, and the-orientation of the flame with respect to the rows of crop plants and-ground surface.

Burner "23a directs flame through row GI, the flame sweeping "the ground surface beyond the row or" plants then passing under the hood 2%. The-burner 23b directs flame through the row BI from the opposite side, this flame sweeps the ground between'therow iii and the hood 29a and finally passes under this hood. Burners 28c and 280? direct flames through row 82, sweeping the ground on either side and passing under the respective hoods 2 3c and2tb. Thesehoools hololor confine the flames under them close to the ground. This operation serves several important purposes, one of which is to insure killing of weeds between the rows at a point remote from the burner tips, and at which point the combustion gases, etc. have considerably cooled andaccordingly are not as effective in Weed extermination as atfpoints Within "the-row of plants or in close proximity to the burner tips. A second function of the hoods is to change the direction of flow ofhot'gases from across the row to parallel with the row so as not "to injure an adjacent row of plants'by two long time of exposureto high temperature. Still another function is to retain the hot gases adjacent 'the'relatively cool ground so as to cool the gases and prevent damage to the underside of the crop plant leaves as the hot gases rise. And yet another .iunctionis todirect the hot gases away from "he cultivator operator, especially if the atmospheric wind is blowingin a direction from the'burners toward the operator. Thefiames shouldbe directed insuch a manner tousweep over the groundsurface for destruction of small weeds as well .as of larger weeds.

.Bumersof diilerent sizes may be used. At certainstages in the. growthrand development of the. crop .piant, aboutsapertaintype and size of flame should be used, forexample, when the plants are small, a relatively small and possibly pointed flame should be used so that the retention time of the stem of the crop plant in a high temperature area will be very short and yet the flame will linger long enough to damage the leaves of the weed plants. Later in the growing season when the crop plants are larger and their trunk stems more resistant larger burners which produce wider and longer flames may be used. It will be understood, however, that the size of burners to be used will be dependent upon many considerations, such as the distance between crop rows, the type of weeds to be killed, the relative resistance of the crop plant to flame temperature, the stage of development of both the crop plants and the weeds to be killed.

When the cultivator passes through a field, and the weeds or weed leaves are exposed to high temperature flames for such short periods of time as herein contemplated, the weeds or their leaves are of course not charred or burned up in the true sense of the term. However, the exposure of living leaves to high temperatures causes certain changes in the leaves to take place, which changes may or may not be apparent or visible at the time of flaming, which changes then ultimately cause the leaves to dry and die, thereby causing the death of the entire plant. Certain leaves upon exposure to the flame becomedarkened in color slightly, other leaves acquire a smooth feel, as if rubbed or polished, in general if a leaf feels "slick to the touch, it will wilt and die. 1

In conjunction with the cultivator as herein described, I have mentioned the use of such a liquefied petroleum gas as propane for the fuel to the burners. I have also hereinbefore described the filling of the tank l9 with liquid propane from a main propane storage tank, not shown.

The hydrocarbon liquid should be gasified prior to passage to the burners 28 and for carrying out such a gasifying or vaporization step such an apparatus as illustrated in Figure 2 of the drawing may be used.

As mentioned above, propane is stored in tank 1 l9 under its own vapor pressure which may vary from say 170 pounds to 200 pounds per square inch or more depending upon the temperature. Propane passes from the tank as a gas through tube 37 and as a liquid through tube 36, which tubes join to form a propane flow line identified by reference numeral 20. This feed passes through a pressure reducing valve 2! which may be of such a type as to discharge propane at a constant pressure, and preferably so. The constant pressure propane, some as gas and some still liquid, is considerably cooled by the pressure reduction in valve 2!. This propane then passes through line 48, valve it into the vaporizer 22 which for exemplary purposes an exhaust pipe heat exchanger. In this jacket 42 the vaporous propane is warmed and the liquid propane is vaporized and the vapors warmed. This propa e then passes from within the vaporizer jacket #2 through an outlet line 49, through valve 41 and into the fuel manifold line 24 from which it passes into the several individual burner lines 2i.

In case the tractor motor operates on this same propane, the gas for motor fuel passes from the vaporizer 22 through the main vapor line 49, valve 4! and then through the carburetor fuel line 23 to the carburetor 25.

At times when the burners are not operating, as for example when the apparatus is in transit from storage to the field, or one field to another or from one plantation to another, only little propane is required to operate the tractor motor. Upon such conditions it is usually advisable to open the by-pass valve 39, and closing valves 40 and 4|, thus permitting the propane fuel to pass through the by-pass pipe 38 directly into the carburetor fuel line 23, the manifold line control valve 4'! of course being closed. Under such conditions I have found that suflicient heat may be furnished from the atmosphere directly to the fuel tank 19 to evaporate suflicient propane for carburetor purposes.

As mentioned hereinbefore, gaseous propane leaves the tank l9 by tube 31 while liquid propane leaves simultaneously through tube 36 This double fuel outlet arrangement is used because it permits some evaporation of propane by absorption of atmospheric heat to take place in the tank 19 itself. If only tube 36 was provided, then only liquid would pass through the pressure reducer 21 and all heat for evaporation of the liquid would then have to be furnished by the exchanger 22 and/ or the auxiliary lines and tubes.

I have found that when operating my apparatus on warm summer days, frequently sufficient atmospheric heat was absorbed by the full tank H) to evaporate propane at a sufficiently rapid. rate to satisfy even the burner requirements. Nevertheless, the vaporizer is provided so that when necessary it may be used to insure suflicient propane vapors for the burners and carburetor.

The regulator 2'! may be substantially any type of regulator available on the market, the only requirement being that it be adaptable to the pur-' pose at hand as herein disclosed. The same holds true for the tractor itself, its make or kind is immaterial. Likewise it may operate on gasoline, kerosene or other fuel, or it may have proper carburetion for operation on propane as herein before mentioned. f

The cultivator burners, similarly, may be of any standard or special make or type provided they serve the purpose at hand. As mentioned hereinbefore, various size burners may need be used during various times of the growing season. Early in the season a burner producing a relatively narrow flame may be most desirable, while as the crop plants become larger and sturclier and therefore more resistant to the action of a flame, a burner producing a broader and longer flame may be used.

The hoods 29 may be made of such width and length as best to suit any given set of conditions. For example, the greater the distance between crop rows, the wider should be the hood, and similarly the longer it is desired to hold the flame and hot gases adjacent the ground, the greater should be the length of the hood.

The burner tubes 21 should preferably be of a flexible nature on account of continual vibrational movement of the hoods due to irregulari ties of the ground over which the hoods pass.

, I have herein shown the middle hood as lagging some distance behind the two outside hoods, this distance of lag being determined by the 10-, cation of the two exterior burners 28a and 28d (of Figure 6) and the angles that flames from these burners make with the rows of crops being cultivated. If so desired, the center hood may be positioned in advance of the two exterior hoods, the position of the burners then being arranged accordingly.

The angle which the axis of a flame makes with a row of crop plants is determined at least in part by the position of a burner with respect assign to tl-ie note which receives inflame; meansof i the name may be at right angles to the crop row as far as the crop row is concerned or as far as killingof the weeds is concerned, but this axis should have a directional component pointing toward the rear end of the flame cultivator so that the flame and hot gases will pass fromiront'to back under the hood. Under this latter condition atmospheric wind may affect the cultivator operation to a lesser extent.

The individual apparatus parts, such as the regulator 29, relief valve 36; the flexible tubes 21; allvalves, the burners 28, and in fact substantially all parts may be selected from commercially available equipment.

A specific example The general design of a. flame cultivator incorporates two high velocity flames placing maximum heatacross the row or drill of cotton from either side. Flam s should have a maximum temperature at a point at least 7 inches from the burner tip. ttern of the flame should be long and very narrow to prevent flame from touching plants being cultivated except at the base of the stalk. A spreading flame will hit leaf growth on the plant and will kill the plant by destroying leaf growth. Each row of cotton or other crop cultivated is touched by two flames, one from either side of the row. These flames should be staggered so that flames can cross rows, one leading the other, so that flames cannot cont'act one another and flare up into the crop being cultivated causing serious damage to the underside of the leaves of the crop.

The burners should be held in position so that flames can cross row at a uniform distance of 6 to 8 inches from tip of burner to the row or crop being cultivated. lhey should also be held in a position so that flame will cross row at to 2; inches above the ground level. This position can be held with individual slides or wheels on each burner; with one slide for each two burners; or'in the case of rigid mounting with positicner's at the end of the machine; or in the case of'the Ferguson cultivation system, burners may be placed on the cultivation frame itself, which is a rigid frame carried by the tractor.

Up to the time of first cultivation weed control and cotton thinning may be handled by one: of several methods. In the case of hill dropped cotton, that is planting about 16 inches apart in hills, conventional row cultivation may be satisfactory. Drilled cotton is easier to handle as this cotton may be cross cultivated or cross plowed as well as cultivated in the conventional manner thereby furnishing rather eflective weed control up to the time flame cultivation can begin.

Cotton may be flame cultivated when the minimum stalk diameter reaches A inch. This minimum disagrees with some of the leading authori'ties' on flame cultivation but the fine control of a propane fire makes the use of flame cultiva tion at an earlier date possible. Extreme care must be taken while cultivating a crop of n1ini=- mum cultivation size. Flame should be directed across the row approximately 91G to direction of row and 10 down from horizon, using a very narrow flame which can be obtained with a tip" size, preferably an inch and a quarter or one inch. This will hold a flame pattern of approximately 1% inches in diameter even'at a point 12 inches from the of the burner. By directing the flamestraight across the row the crop is 8. xpdsed for a minimum period of time, thereby lessening thec'hance of damage to the crop. The kill (ii-the effect on vegetation will be less than can be obtained but the chance of damaging the young crop is considerably less. This setting can be used for the first time through the crop. The second time through the crop, which probably would come when the stalk diameter has reached to men should be handled with the sameburner tip but with the burners directed back from so to 45 and possibly moved as close to the crop row itself as 6 inches from the drill this setting exposes the crop to the flame for a longer period of time, thus getting a more efiicient kill. This second cultivation will allow the user of the flame cultivator to hold the weed growth in check. On these operations, regular cultivation can be done simultaneously or should follow soon afterwards.

Fuel consumption for the first two times over with the flame cultivator should average be} tween 3 and 4 gallons per acre cultivated. If Eclipse compound injectors are used an orifice size of 54 to 56 and a fuel pressure between and pounds will give the desired results. Other types of burners at similar operating pressures will show comparable fuel consumption.

For the third and subsequent flame cultivations, larger burner tips and greater heat output may be used. Orifice sizes may be increased to as great as 52 drill size and fuel pressures ranging from 30 to pounds may be used depending on the density of the weed growth and the rate of speed at which the unit is to be operated. Field speeds as high as l to 4 /2 miles per hour may be used (that would be third gear, governed speed on most tractors). Burner settings for the larger nozzles and higher output burners is practically the same as with smaller burners and smaller tips, except that the burners can be backed further away from the rows to obtain wider coverage. With the output of the burners increased this coverage may be increased to approximately 20 inches across the rows, with the tips as far as 10 inches from each row. At the start the flame should be directed straight across the rows or if the crop is large enough, directed back slightly to obtain a greater time of exposure to the crop and to the weed growth in the drill of cotton.

About thi time in the growth of the cotton crop, tie vines, morning glories, red vines and other climbingvines begin to show in the crop. These vines will climb the cotton stalks and will .follow the 'row of cotton and if allowed to grow v unmolested will finally tie the cotton row all together and render cultivation or handling of the crop very difiicult. Intense heat from a high velocity fire directed across the row at a tempera ture of 2000 to 2200" will so stricture these vines Eli? that they will die into the top of the crop. The user of the flame cultivator need not be alarmed if the vines fail to die in the top of the cotton for a week or 10 days following application of fire as the retained plant food in the vine will be stopped. Finally the obnoxious vine growth will die in the top of the crop of cotton, sometimes as long as two weeks following flame cultivation. It is not unreasonable to expect Johnson grass, rabgrass and practically all vegetation except possibly large weeds to be killed from the crop of cotton. Wild coffee beans and wild okra grow ing in the crop will probably not be killed. These large plants have to be controlled with hoe labor as thatis practically the only method of killing them due to the fact that the size of the stalk these large weeds will also kill the cotton plants.

For normal plantation operations two flame cultivations using high output burners, one while the cotton is blooming and the bolls are beginning to set on, and another just before the bolls open will be satisfactory. This will normally carry the crop to picking time, but there may be occasions when during periods of wet weather, weed growth will become serious making a third application of the high output burnersnecessary.

Using the high output burners for flame cultivation, fuel consumption of 3 /2 to 5 gallons per acre may be expected. This fuel consumption will depend on the orifice size of the burners, the type of burners used and the pressure at which the burners are operated, as well as field speed. This period represents the greatest saving to the user of flame cultivation equipment as the cotton crop is getting large at this time and it is very dllflcult for hand hoe labor to do satisfactory work, because they damage the crop to a much greater extent than the flame cultixation equipment. The user of a flame cultivator need not be alarmed at obvious damage to the low stalks of cotton as it is the opinion of many very successful planters that the low limbs of cotton which develop early actually lower the grade of the cotton. They are exposed to dirt and are shaded, which sometimes result in boll rot, damage to the fiber of the cotton and a general lowering of the grade of the entire crop due to the fact that the early open cotton on the low limbs becomes damaged, unless picked a the bolls open. This is especially true in case the crop is picked with a mechanical picker, which operation must wait until all the bolls are open on the plants. The lower bolls will normally open 2 to 4 weeks ahead of the later bolls at the top of the crop. Due to this condition, some planters consider it an advantage to have the lower limbs of the crop killed by high output burners being used on the crop. This allows the strength that would go into low limbs to go into the upper limbs to develop a slightly later crop which has a higher grade and a greater market value.

It is suggested that the user of the flame cultivator adapt the machine to his particular problearn. In some cases it may be necessary to flame cultivate only three times, possibly once with the lower output and twice with the higher output burners. Other pieces of land and operations may require as many as five cultivations, and sometimes even six as the vegetation growth on different plantations will vary with the season, rainfall. fertility of the soil and previous cultivation practices.

The user of flame cultivation equipment can expect a marked saving in the cost of the cultivation of the row of cotton. Flame cultivation costs between $3.00 and $5.00 per acre, depending on the cultivation required, may be expected.

Exhaust pipe Vaporizers such as described in my copending application, Serial No. 638,405, filed December 29, 1945, or in copending application in which I am a joint inventor, Serial No. 638,407, filed December 29, 1945, may be used as vaporizer 22. Both of these exhaust pipe vaporizers are adapted to vaporize sufiicient propane or other liquefied petroleum gas to serve as many burners as required and also to furnish fuel vapors to tractor engine carburetor in case the tractor engine operates on this material as fuel. However atmospheric Vaporizers may be used.

The tractormotor, however, may use gasoline as fuel in which case the vaporized propane need not be piped to the carburetor. Further, the tractor may be powered by any fuel desired.

It will be obvious to those skilled in the art that many modifications or alterations in appa- Jratus parts and methods herein described may be made and yet remain within the intended spirit and scope of my invention.

Having described my invention, I claim:

1. In a flame cultivator assembly adapted to burn a liquefied petroleum gas to produce flames for killing weed growth in and around crop rows, the improvement comprising in combination a cultivator body, a means supported by said body for storage of the liquefied petroleum gas fuel, a plurality of burners supported by said body and so disposed as to direct flames through said crop rows, a conduit means connecting said storage means and said burners, means in said conduit means for reducing pressure in said liquefied petroleum gas, means in said conduit means for evaporating said liquefied petroleum gas for burning in said burners, and hoods supported by said body and adaptedto be positioned between pairs of adjacent crop rows to receive flames from burners disposed outside said adjacent crop rows and so positioned as to direct said flames across said adjacent crop rows to a point under said hood.

2. A hood for use in the disposal of a flame from a burner of a flame cultivator, said flame having passed across a row of crop plants, comprising a pair of parallel vertically disposed side walls, the tops of which are joined by a roof-like member, said walls and roof being impervious to passage of gases and said ends of the structure being open; the bottoms of said vertically disposed side walls having sled-like runners adapted to serve as skids for the sliding of the hood across the surface of the ground; the rooflike member extending beyond one end of each side wall and said extended roof member having means for attachment to the cultivator assembly; the space under the extended roof member being adapted to receive flame from said burner.

3. In a flame cultivator assembly adapted to cultivate row crops for control of weed growth, the combination comprising a cultivator body, means supported by said body for storage of a liquefied petroleum gas fuel, a plurality of burners adapted to burn said fuel and supported by said body in such a position as to direct flames through crop rows, conduit means connecting said fuel storage and said burners, a pressure reducing means and a fuel vaporizing means in said conduit means, and a hood supported by said body and positioned between two adjacent c'rop rows to receive flames from said burners disposed outside said two adjacent crop rows.

4. In a flame cultivator assembly adapted to cultivate row crops for control of weed growth, the combination comprising a cultivator body, means supported by said body for storage of a liquefied petroleum gas fuel, a plurality of burners adapted to burn said fuel and supported by said body in such a position as to direct flames through said crop rows, conduit means connecting said fuel storage and said burners, a pressure reducing means and a fuel vaporizing means in said conduit means, a plurality of hoods sup ported by said body, one hood of said plurality of hoods positioned between two adjacent crop rows to receive flames from a burner disposed outside of each of said two adjacent crop rows, a second of said plurality of hoods positioned between 20118 ofsaid two adjacent crop rows and the next crop row and disposedto receive flame from a,

burner disposed between said two adjacent crop rows, and a third of said plurahty of hoods p0- sitioned between theother crop row of said two adjacent crop rows and the next crop row and disposed to receive flame from a burner disposed between said two adjacent crop rows.

ALVIN W. PECK.

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

STATES PATENTS 7 Number Name Date Rea-22,303 McLemore Oct. "15, 1946 1554 983 Collins Apr. 8, 1930 2,327,204 M'cLemore Aug. 17, 1943 OTHER REFERENCES Pacific Rural Press, vol. 144, No. 13, page 365,

article entitled Weeding Onions with Fire 4, Guns, published Dec. 26, 19.42.

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