US2844195A

US2844195A - Cycling burner for vehicle heaters

Info

Publication number: US2844195A
Application number: US534029A
Authority: US
Inventors: John F Wein
Original assignee: Stewart Warner Corp
Current assignee: Stewart Warner Corp
Priority date: 1955-09-13
Filing date: 1955-09-13
Publication date: 1958-07-22
Anticipated expiration: 1975-07-22

Description

July 22, 1958 J.- F. WEIN CYCLING BURNER FOR VEHICLE HEATERS Filed Sept. 13, 1955 2 Sheets-Sheet 1 July 22, 1958 Filed Sept. 13, 1955 J. F. WElN CYCLING BURNER FOR VEHICLE HEATERS 2 Sheets-Sheet 2 United States Patent Warner Corporation, Chicago, 111., a corporation of Virginia Application September 13, 1955, Serial No. 534,029

1 Claim. (Cl. 158-28) The present invention relates generally to vehicle heaters of the combustion type and more particularly to a rapid cycling. burner for such heaters.

One of the objects of my invention is to provide a novel burner mechanism for a vehicle heater, which is well adapted for use in a type of service where it is required that the fuel to the burner be turned on and off in cycles of short duration.

Yet another object of my invention is to provide an improved vehicle heater burner in which combustion ceases substantially instantaneously upon connnand and in which substantially no residual fuel is present in the heater combustion chamber after the fuel has been turned off.

Still another object is to provide a novel burner and fuel control assembly as an integral portion thereof which greatly reduces the requirement for periodically cleaning elements of the burner, thereby insuring long periods of satisfactory operation between inspection and servicing.

Still another object is to provide a novel assembly of elements which can be manufactured at relatively low cost for accomplishing the above set forth objectives.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention which is illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer to similar parts throughout the several views:

Fig. 1 may be considered as a longitudinal vertical sectional view through a sealed combustion heater which incorporates a burner and fuel control assembly embodying features of the present invention;

Fig; 2 is a longitudinal vertical sectional. view through the heater burner drawn to larger scale. be considered essentially as an enlargement of a portion of Fig, l; and

Fig. 3 is a transverse sectional view which may be con- This view may 7 sidered as being taken substantially in the direction of the arrows substantially along the :line 33 of Fig. 2.

The heater shown consists essentially of a generally cylindrical air casing 10. through which ventilating air passes from right to left. The right .hand'end Of this case, therefore, may be considered-as being connected to a supply of ventilating air such as a blower for instance, while the left hand end of the-case will ordinarily be 'con nectetl to a ventilating air duct system for distributing the heated air to a desirable location- The case 10 has a section at the top thereof cutout as indicated by the line 12, and the opening thus produced isclosed by a sheet metal .cover 14 secured 'to-the case 10 by screws 16. V Within the case a sheet metal heat exchanger, as indicated at 18, is so positioned that ventilating air flows 2,844,195 Ratented July 2.2, 1958 "ice and which has a constricted inner end 24 which forms a loose fit with a flange 26 at the terminal end of a com bustion chamber 28.

The combustion chamber 28 is formed essentially as a drawn sheet metal cut and has its base secured as by rivets 30 to a circular plate 32 which in turn is connected by screws 34 across the mouth of a cup-shaped member .36 which may conveniently be fabricated as a die casting since it remains cool during operation of the heater.

At its open end the cup 36 has a flange 38 connected to a similar flange 40 at the outer end of the adapter fitting 22 by a split, screw-tightened, clamping band 42. Sealing between these members is effected by a resilient gasket 44.

Air for combustion is brought into the cup 36 through one of a pair of integrally formed hollow bosses extending radially from the body of the cup 36 and terminating in inlet openings, one of which is indicated at 46.

Air for combustion is supplied from a suitable source, a blower for instance, to one of the inlets 46, the other being almost closed. It could be completely closed, but leaving a small opening has the effect of making the burner less sensitive to the length of the exhaust line. Air thus delivered to the chamber within the cup 36 passes through louvers 48 formed through the plate 32 into the annular space 50 between the combustion chamber 28 and the adapter fitting 22. It then passes into the combustion chamber through openings 52 in the side Wall of the cup 28 and through openings in the base thereof, one of these openings being centrally located as indicated at 54. I 1

The .cup 361's formed to provide a hollow stem 56 in the center thereof with its end connected to a conventional fuel spray nozzle 58, the tapered nose of which projects through a close fitting opening in the plate 32 so as to align the nozzle 58 with the opening 54 at the base of the combustion chamber. a

The insulator 60 ofan igniter extends through-an open- .ingin the base of the cup 36 and through aligned open 'ings in the plate. 32 and the base 'of the combustion chamber and within the combustion chamber is provided withan exposed electrode 62 spaced from a grounded electrode 64. The spark plug is retained in position by a pair vOfgaskets 66 and a screw-retained clamp -fitting 68 at the base of the cup 36. In use it is anticipatedthat a cable connected to a source of high tension electricity will be connected to the terminal 70 of the spark plug thereby producing sparking betweenthe electrodes 62 and .64 in a position to ignite fuel sprayed from the'nozzle 58.

The hollow stem in a position just behindthe nozzle 58 is provided with a poppet type fuelvalve indicated gener y at which opens under the influence of an electromagnet 74 whenever the circuit of this magnet is energized. j t

More specifically, the hollow stem 56 has a passage formed completely therethrough. from the nozzle and to the exterior surface at the base of the cup 56. Atiits thereover, and this heat exchanger is supplied with hot 22 which is formed as a portion ofthe heat exchanger inner end this passage is threaded to receive the base of the nozzle 58 and this threaded portion continues somewhat therebeyond to receive a threaded retaining nut or ring 76 having a hexagonal hole 78 extending there- 'through to provide a fuel passage and to pl'flvide .a means for wrenching the nut into position. This nut presses against the back surface of a Valve seat forming member 80 which is sealed against the-'bottorn of-the threaded recess by a resilient gasket 82. A smaller Passage 84 extends through the stem 56 beyond the threaded recess and is fluted at each side as at 86 for a purpose to appear presently. I V 1 .Near the back of the cup 36 the passage 84 axially int s s he tom f a shallowrecess 88 Which opens to the rearward face of the cup 36. A shallow annular groove'is formed in the die casing around the recess 88 and contains a resilient sealing gasket 90 which projects slightly beyond the back face of the cup 36 when in the uncompressed condition. -The re,cess 88 is con.- nected by .a drilled passage 92 'to a cored opening 94 which is threaded to receive a fuel inletffitting 96. This fitting is in turn connected to a source of fuel under pressure, such as a motor driven pump for instance.

\ Therecess at 88 is' closed by the base ot'a generally cylindrical sheet metal cup 98 which houses the electromagnet for the operation of-the valve 72. This coil structure will be described in further detail presently. For the present it is pointed out merely that it has a flat base end pwhich is secured against the back surface of the cup 36 bymeans of screws 100 so as to compress the seal for the back of the chamber 88.

A poppet valve 102 has a stem portion 104 which fits the bore 84 so as to slide freely therein. This stem is drilled longitudinally to provide a central passage 106 extending from end to end of the valve member which intersects a transverse passage 108at about the center thereof. The ends of the transverse passage 108 communicate with a circumferential groove 110 formed in stem 104. The inner end of the stem is fitted with a resilient rubber disc 112 which is brought into engagement with the valve seat 80 when the valve poppet is urged toward the left as seen in Fig. 2. This closes a passage 114 which extends through the member 80, and communicates with the hexagonal hole 78 through the retaining ring' 76.

At its outer end the stem 102 is provided with a head 116 which lies within the recess 88 and has a thickness somewhat less than the depth of this recess. This valve poppet is urged toward closed position by a coil spring 118 which extends into a cavity in the center of the head .116, with its opposite end bearing against the base of the coil housing 74.

The magnetic structure for operating the valve poppet which is formed of steel or other magnetic material, is constructed as follows: The cup 98 previously referred to is formed of sheet steel and has a central opening formed therein which is shown as having a diameter of the order'of two-thirds the diameter of the head 116 of the poppet valve. A circular plate 120 formed of brass or other suitable non-magnetic material, is located within the cup .98 against the base thereof, and this plate is threaded to receive the screws 100 previously referred to which extend through clearance openings 122 in the base of the cup 98. This plate also has an opening through the center thereof, which is surrounded by a circular ridge which fits the opening at the center of the cup 98; This ridge projects almost to the outer surface of the cup.

A'core for the coil is indicated at 126. It is formed as a length of round iron rod which is knurled near one end with this end pressed into the central hole through the brass plate 120 so that the knurling brings about a rigid assembly as between the members. After this coil core or post has been pressed into position, the space around its end is filled with silver solder 124 and the outer face of the cup is ground smooth so that the face at the end of the cup, the outer surface of the silver solder 124 and the end'of the post 126 all lie in the same plane. 1 g

The head 116 of-the poppet valve is provided with an annular outstanding shallow ridge 128 opposite the silver solder ring 124 for a purpose to be pointed out presently.

The outer end of the coil core 126 is internally threaded to receive a cap screw 130 which secures a circular cover 132 with a depressed center so that the cover closes the opening at the outer end of the cup 98. This cover is formed of a magnetic material such as steel for instance. r

The coil is indicated at 134 and is formed as a prefabricated unit in which the, wire is wound upon a spool or bobbin 136 having a hole therethrough which slides over the stem 126.v The bobbin is preferably formed of a molded plastic substance. The outer flange of this bobbin carries a radial extension 138 formed of the bobbin material which is provided with a radially projecting terminal tab 140 soldered to one of the coil leads indicated at 142 in Fig. 3. The other coil lead 144 is soldered to a tinned thin strip of brass or similar springy metal 146 which extends across the top of the bobbin flange'136 with its ends 148 notched and bent downwardly to form tabs hooked into shallow slots 150 out into the periphery of the top flange 136 of the bobbin, thereby retaining the strip 146 against the bobbin flange. Near its midpoint this strip is slotted longitudinally as at 152 to permit passage of the cap screw 130, and the metal of the strip alongside this slot is bent outwardly somewhatas indicated at 154 so that the-outer surface of the strip at the center is concave in a transverse direction.

During assembly, therefore, the wound bobbin is simply slid over the outer end of the post 126 and the cover 132 then is secured in place by the cap screw 130. Under these conditions the inner face of the cover 132 will engage the outwardly turned portions 154 of the strip 146 before the cap screw has been fully tightened, so that the inside surface of the cover 132 will spring these tabs 154 inwardlyand form a good electrical contact between the strip 146 and the cover, and hence with the end 144 of the coil which it is intended to ground. Conveniently, therefore, the ground terminal for the coil can be connected to the outer surface of the cover plate 132 as is indicated'at 156 if any separate ground lead is needed. With this arrangement the prewound coil can be removed and replaced in the electromagnetic structure without the necessity of exercising care to insure that a good ground connection is made during reassembly.

When the terminals and 156 are energized, a magnetic circuit will be established from the end of the core 126, into the central portion of the head 116 of the valve poppet, through the valve head in an outwardly direction past the region occupied by the silver solder ring 124, then back to the metal of the cup 98, through the Wall'of this cup .and across the cover plate 132 to the opposite end of the stern 126. The head 116 of the valve poppet is therefore attracted against the pressure exerted by the spring 118, until the annular ridge 128 is brought into contact with the ring of silver solder 124, thereby so limiting the outward movement of the valve poppet that there is no direct engagement between the magnetic material of the poppet valve head 116 and the magnetic material of the stem 126 and case 98. This action moves the soft rubber disc 112 away from the nose of the valve seat 80 and permits fuel to flow from the fitting 96, through the passage 92 into the recess 88 and thence through the passage 106 and cross-passage 108 into the longitudinally extending flutes 86. From here the fuel flows through the valve seat passage 114 and retaining ring passage 78 to the base end of the nozzle 58.

When the magnetic coil is deenergized, the spring 118 urges the valve poppet inwardly so as to bring its end 112 against the valve seat 80 thereby closing off communication from the inlet fitting 96 to the nozzle 58. Motion of the valve poppet in both directions is free, since the large passage 106 and 108 through the valve poppet prevents any substantial hydraulic cushioning action and of course permits ready equalization of fuel pressure on both sides of the head 116.

It is important to note that the passage through the valve member 80 and through the retaining ring 76 to the base of the nozzle 58 is extremely short and small and therefore has a minimum of volume. This is important because it insures that when the valve has been closed "by de energizing the electromagnet, there will be very little fuel trapped between the valve and the nozzle and therefore practically no tendency for fuel to dribble from the nozzle after combustion has been extinguished. The result is that it is not necessary to have a delay circuit to continue the combustion air blower in operation for a period of time after the fuel has been turned off in order to make sure that liquid fuel does not remain in the heater. In addition, it has been found that the principal source of the carbon deposit which forms upon the end of a spray nozzle and which eventually interferes with the spray pattern is the gradual oozing of fuel from the nozzle after the burner has been turned off. Under ordinary circumstances this produces a rapidly accumulating carbon deposit which requires frequent nozzle cleaning. The present arrangement, however, has been found to eliminate this problem to such an extent that in ordinary heater service in an automotive vehicle it should not be necessary to clean the face of the nozzle 58 oftener than once every two or three years or so even though the burner is used in a type of service requiring rapid cycling.

A rapid cycling system is one in which a thermostat in the hot air duct turns the burner fuel valve off and on as necessary in order to maintain a substantially constant outlet air temperature with the ventilating air stream flowing continuously. Such systems are effective and simple, but place great demands upon the burner because of the high frequency of the on-olf cycles.

A specific control system for a heater of this type is described in the copending application of Frank A. Ryder, for Automotive Vehicle Heating System which was filed on August 5, 1955 and which has been given Serial No. 526,714.

From the above description of a preferred embodiment of my invention it will be apparent that the mechanism described is compact, rugged and easy to assemble and service. Furthermore, it overcomes the principal objection to heater systems of the rapid cycling type in that the substantial prevention of fuel dribbling from the nozzle greatly increases the operating life of the burner between servicing operations ordinarily frequently necessary to remove carbon accumulations from the nozzle. This is a particular advantage in heaters for automotive vehicles where leaded, high unsaturated fuels are ordinarily used, such fuels being more susceptible to the formation of solid deposits than such liquid fuels as fuel oil for instance.

It will also be evident that variations and substitutions may be made in the structure shown and described without departing from the scope or spirit of the invention and that therefore the scope of the invention is to be measured by the scope of the following claim.

Having described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

In a burner for supplying hot products of combustion to the heat exchanger of a sealed combustion heater for an automotive vehicle, a sheet metal cup forming a combustion chamber, a plate secured to the base of said cup, means forming a larger cup, means securing said plate across the mouth of said larger cup, said plate having a central opening therethrough, the base of said combustion chamber cup having a central combustion air and fuel inlet opening in alignment with the last said opening, a generally cylindrical shell enclosing said combustion chamber cup and fitted thereto at the open end thereof, said shell being sealed against the end of said larger cup and closed by said plate thereby to define an annular space between said combustion chamber cup and said shell, said larger cup having a hollow stem at substantially the axis thereof, a spray nozzle secured in the end of said stem, said nozzle having a tapered forward face adapted to project through said plate central opening and seal said opening when said plate and said larger cup are secured together, said combustion chamber forming cup having air inlet openings formed through the side wall thereof to communicate the interior thereof with said annular space, said plate being formed with a plurality of openings therethrough to communicate the interior of said larger cup with said annular space surrounding said combustion chamber cup, means for supplying air for combustion to said larger cup, means providing a valve seat in said hollow stem immediately adjacent to said nozzle, the passage through said stern providing a practical minimum of volumetric space between said valve and said nozzle, a valve poppet in said hollow stern on the side of said seat opposite said nozzle, resilient means for urging said poppet against said seat, means for supplying fuel under pressure to said hollow stem on the side of said seat away from said nozzle, and an electromagnet assembly secured to the base of said larger cup and sealing the end of said hollow stern and adapted when energized to attract said poppet away from said seat.

References Cited in the file of this patent UNITED STATES PATENTS 1,664,612 French Apr. 3, 1928 2,022,513 Macchi Nov. 26, 1935 2,124,443 Wotring July 19, 1938 2,531,939 Jacobs Nov. 28, 1950