US2258042A - Heating system - Google Patents

Description

2 Sheets-Sheet 2 K. P. BRACE HEATING SYSTEM Filed Jan. 14, 1938 Oct. 7, 1941.

IN VENTOR.

Patented Get. 7, 1941 UNITED STATES PATENT OFFICE HEATING SYSTEM Application January 14, 1938, Serial No. 184,971

8 Claims.

This invention relates to heating systems, and is illustrated as embodied in a domestic heating system utilizing an oil burner.

An important feature of the invention relates to a novel control system especially adapted for burners of the type in which the fuel seeps through a porous refractory element into an air stream, in that while the fuel and the air-supply are both turned on when the room temperature drops to a predetermined level, when the temperature rises again only the fuel supply is turned off, the fan continuing to operate as long as there is any fuel still burning.

Since the porous refractory member in effect stores up a substantial amount of fuel, this novel method of operation insures that it will be entirely burned before the air supply stops, thereby guarding against explosions. This method of operation also has the effect of burning ofl any deposits of carbon which may have formed during extended periods of operation. Preferably the circuit for this control system also includes a novel safety igniter circuit asspciated with the fuel-supply and fan-motor circuits.

Another feature of novelty relates to a compact and simple but reliable compound switch or equivalent control device controlled by the burner temperature for effecting the necessary changes in the igniter and fan-motor circuits to cause the above-described method of operation. The illustrated embodiment is operated by the expansion and contraction of air in a bulb or the like subject to heat produced by the burner, in such a manner as to be operated by the initial expansion or contraction of the air, so that it acts promptly. Novel means is provided for relieving excess pressures due to subsequent further expansion or contraction.

The above and other objects and features of the invention, including a novel igniter arrangement and various other novel arrangements of form of control switchfor use in such a circuit;

and

Figure 3 is a vertical section through a domestic steam heating boiler and furnace showing an installation of a burner with my novel control circuit.

In the arrangement illustrated in Figures 1 and 3, a suitable furnace ID of any'desired type is provided for heating a house or the like space under the control of a room thermostat l2. The bottom of the furnace I0 may be lined with firebrick M or equivalent refractory material, to such height as may be necessary. An oil burner described below is mounted to discharge through a refractory shield I6 into the interior of the furnace.

The burner, in the form illustrated in Figure 3, includes a generally cylindrical casing l8 having a conical end projecting through the shield l6 and open at the end opposite the furnace, for the intake of air. The casing I8 is mounted on a suitable support 20. Inside the casing there is a ledge or dam 22, forming a sump into which excess fuel drains, and directing the fuel away through a suitable drain conduit 24. This conduit may, if desired, lead to one of the standard commercial safety devices (not shown) such as a bucket switch, for opening the control circuits of the burner in case of excessive drainageof fuel therefrom.

In the open end of the casing l8, and arranged coaxially with respect thereto, suitable brackets 26 support a motor 28 provided with air-circulating means such as a fan 30 on the motor shaft.

The blast of air from the fan 30 is preferably directed through a set of guide vanes 32, which are mounted in the casing l8 just beyond the fan, and which in the form shown insure a substantially straight flow of the air current and prevent spiral movement of the air. The shape and arrangement of these vanes may be suitably modified if it is desired to direct the air otherwise than in a straight path.

In the conical end of the casing I8 suitable brackets 34, riveted at their outer ends to the casing, support (coaxially of the outer casing l8) an inner casing 35. The space between the casings l8 and 36 provides an annular outer passage for secondary air from the fan 30. The inner casing 36 has in its end adjacent the fan 30 a reduced-diameter opening 38 forming an intake for primary air from the fan 30.

The oil or other fuel is supplied, for example through a conduit 40 controlled by a suitable fuel valve 42 operated by a solenoid 44, and in the arrangement illustrated dripping through a feed conduit 46, to a porous refractory member 48, and seeps down through the porous structure. of that member to be vaporized and taken up by the primary air.

The fuel need not necessarily be supplied on niter "6B, the fuel-valve solenoid 44.

the upper surface of the refractory member, as the capillary action of its porous structure will distribute the fuel satisfactorily even if it is supplied at a lower point.

The refractory member 48 may have its outlet end conical in form, so that its surface parallels the conical outlet end of the casing I8. Thus combustion of vaporized fuel and air at the base of the refractory serves to heat the tip and there by increases the capacit of the burner.

The fuel conduit 46 discharges onto the refractory member 48, and the fuel seeps through the porous structure thereof and crosswise of the passages 62 or 64. The heat of the combustion taking place around the end of an'd'i-n the passages of the refractory member vaporizes the fuel and it is taken up by the primary air. This gives unusually effective carburetion for the large volume of primary air required in a burner of this character.

The lower .part of the member 48, at its outlet end, has arranged crosswise thereof a hotwire igniter 68, connected by supporting posts I to the lead wires described below. This igniter is arranged in a recess formed in the refractory member, out of the direct path of the primary air, in a sort of eddy current due to the passage of the primary air. Preferably it is in direct contact with the surface of the refractory member, so that a small part of the latter is heated up to vaporize the fuel therein and bring about immediate ignition thereof in the air of the eddy current.

It will be seen that so long as fuel-is supplied and the motor 28 operates, the fuel and primary air mixed in the passages 62 burns and then in turn is mixed with an outer envelope of secondary air from the annular passage between the casings 36 and I 8. It will be noted that the combustion takes place immediately adjacent the refractory member, and to some extent actually in the passages 62, heating the refractory member to a high enough temperature tocause rapid vaporization of the fuel.

The burner described above, except as included in the control system hereinafter described, is

claimed in my copending application No. 145,706, filed June 1, 1937.

Figure 1 shows one manner of controlling the described burner or its equivalent. A source of current, such as the secondary of a transformer 14, is connected through line wires 16 and I8, one of which contains a switch 80 operated by the room thermostat I2, to the motor 28. The

switch 80 has a second contact so that it also closes a parallel circuit through wires 82 and 84and the igniter 68. The wires 82 and 84 have connected therebetween, in parallel with the-ig- Thus closing the switch '80 closes three circuits through (1) the motor, (2) the igniter, and (3) the fuel valve solenoid.

As a safety measure, in order to shut-off the fuel supply after a predetermined interval if the igniter does not-operate, there is connected in shunt with the igniter a heating resistance 86 which, after the desired time interval, deflects a bimetallic strip 88, causing a plunger 90 to open a switch contact 92 in the line 82, thereby shutting off both the fuel valve and the igniter.

The wires I8 and'82 terminate in contacts 94 in an enlarged upwardly extendingspace 96 in a member 98 of suitable insulating material.

space 96.

This member is formed with a lower horizontal passage I00 of capillary size, communicating at its ends with the space 96 and with another and somewhat higher upwardly-extending enlarged space I02 which is open to the atmosphere through a porous plug I04 held by a perforated threaded cap I 06. The space I02 contains contacts I08 connected to the lines I6 and I8 around the room-thermostat switch 80.

The above passages form a U-shaped passage containing a globule of mercury, shown in the The mercury can pass through the passage I00 only when forced by a substantial pressure thereon. The mercury cannot pass the porous 'plu'g I 04, nor a similar plug llI held by a perforated locking ring H3 leading to a passage II5 communicating with the mouth of a sealed air bulb Ill.

The bulb is arranged in the path of the burned gases from the burner, for example in the flue connection from the furnace as shown in Figure 1. It is not necessary that the burned gases actually impinge on the bulb, but the air in the bulb must be subject to the heat of the gases so that it expands when the burner is going and contracts when it-is notgoing.

In operation, when-the room temperature drops to a predetermined level, the thremostat I 2 closes the double switch contact member 80, thereby closing the three circuits through the motor and the solenoid 44 and the igniter. The globule of mercury is at this time in the space 96, and completes the igniter circuit.

As soon as the burner ignites, the hot exhaust gases act on the bulb II! to expand the air therein, driving the globule of mercury through thecapillary tube I00 into the space I02, thereby breaking the igniter circuit at 94 and closing the contacts I08.

When the room temperature rises, the contact opens, breaking the circuit through the solenoid 44 and shutting off the fuel supply. A substantial amountof fuel remains in the pores of the member 40, however, so the burner is not immediately'extinguishe'd. The motor circuit remains closed through contacts I08, therefore, until this fuel is all burned. Thereupon the air in the bulb =I IIcoolsand contracts, and the atmospheric pressure in space I02pushes the mercury'globule back through the capillary passage I00 into the space 96, leaving the circuits'ready for the next cycle. 'Excess air, after the mercu'ry has been pushed from one side to the other, merely bubbles i'dly through the mercury.

Figure 2 shows an alternative form of stack switch 'which'has most of the advantages of the form shown in Figure 1, as well'as certain other advantages. In this embodiment, the body I 98 of the stack "switch device contains an enlarged space I96 (shown containing the mercury globule) connected by a vertically-arranged capillary U-pa'ssa'ge 200 to a second enlarged space 202 which is at substantially constant (e. g.,

atmospheric) pressure.

The space 202 communicates by means of a passage through a pointed tip 204 (designed to and through the lower portion of a plug or fitting 213, with a transverse opening 215 opening at one end into an air bulb 2H which corresponds to the air bulb H1 in Figure 1. The other end of the opening 2l5 registers with an opening 220 in the switch body 198 and thereby communicates, by means of a small passage through a stem 222 threaded into the side of the switch body, with the interior of an expansible metallic bellows 224 in the housing 208, the bellows being supported by the stem 222,

The opposite face of the bellows 224 carries a stem 226 adjustably threaded into a socket in one end of a thrust member 228 which carries, threaded adjustably thereon, spaced abutments such as nuts 230 and 232. Between these abutments is the resilient operating blade 234 of a standard commercial snap-action switch. Such a switch will be opened or closed, as the case may be, or if double-acting will be reversed in position, by the initial motion of abutment 230 or 232, but will not be operated in the reverse direction unless positively actuated in the reverse direction by the opposite abutment.

In the position shown, the blade 234 has just snapped to the right due to expansion of the air in bulb 2H, where it will remain until operated by movement of abutment 232 to the left caused by contraction of the air in bulb 211. In this embodiment, the first expansion or contraction of the air operates the switch, and excess pressure thereafter is relieved by shifting of the mercury in one direction or the other through the U-passage 200, followed by passage of air through the mercury.

By utilizing a double-acting snap-action switch in this device, it can be substituted directly for the stack switch shown in Figure 1, and will operate in the same manner in the control circuit.

While one desirable control circuit, and two forms of stack switches, have been described in detail, it is not my intention to limit the scope of my invention by that description, or otherwise than by the terms of the appended claims. The present application is a partial continuation of my Patent 2,174,818 of October 3, 1939.

I claim:

- l. A device for controlling circuits such as the igniter and motor circuits of a burner 'com- I prising a member having formed therein a U- passage having a central portion of capillary size such that it will not pass mercury except under substantial pressure and having enlarged upwardly-extending end portions one of which opens to atmosphere and which are closed by porous parts which will pass air but not mercury, a sealed air bulb opening into the other of said enlarged portions, a pair of circuit contacts in each of said enlarged portions and a globule of mercury normally positioned in one or the other of said enlarged portions and shifted back and forth through said capillary portion in response to variations in pressure in said bulb.

2. A device for controlling circuits such as the igniter and motor circuits of a burner comprising a member having formed therein a U-passage having a central portion of capillary size such that it will not pass mercury except under substantial pressure and having enlarged end portions one of which has means opening to atmosphere, a sealed air bulb opening into the other of said enlarged portions, a globule of mercury normally positioned in one or the other of the enlarged end portions and shifted back and forth through said capillary portion in response to variations in pressure in said bulb, and circuit closing devices operated in response to such variations in pressure. I v

3. A device for controlling circuits such as the igniter and motor circuits of a burner comprising a member having formed therein a U passage having-a central portion of capillary size such that it will not pass mercury except under substantial pressure and having enlarged end portions one of which has means opening to atmosphere, a sealed air bulb opening into the other of said enlarged portions, a globule of mercury normally positioned in one or the other of the enlarged end portions and shifted back and forth through said capillary portion in response to variations in pressure in said bulb, and a pressure-operated switch connected to said bulb and opened and closed in response to such variations in pressure.

4. A device for controlling circuits such as the igniter and motor circuits of a burner comprising a member having formed therein a U-passage having a central portion of capillary size such that it will not pass mercury except under substantial pressure and having enlarged end portions one of which has means opening to atmosphere, a sealed air bulb opening into the other of said enlarged portions, a globule of mercury normally positioned in one or the other of the enlarged end portions and shifted back and forth through said capillary portion in response to variations in pressure in said bulb, and contacts in at least one of said end portions and bridged by the mercury when in said end portion.

5. A control switch comprising an air container adapted to be subjected to the temperature of part of a heating system, a device having enlarged spaces connected by a capillary passage and arranged with one space communicating with said air container and with the other space of substantially constant pressure, mercury in said device shifted back and forth through the capillary passage from one of said spaces to the other in response to variations in pressure in said air container and a switch opened and closed in response to said variations in pressure.

6. A control switch comprising an air container adapted to be subjected to the temperature of part of a heating system, a device having enlarged spaces connected by a capillary passage and arranged with one space communicating with said air container and with the other space at substantially constant pressure, mercury in said device shifted back and forth through the capillary passage from one of said spaces to the other in response to variations in pressure in said air container, and a snap action switch having means operated by an initial variation in said pressure, excess pressure due to subsequent variation in the same sense being relieved by the shifting of the mercury and the passage of air past the mercury,

7. A control switch comprising an air container adapted to be subjected to the temperature of part of a heating system, a device having enlarged spaces connected by a capillary passage and arranged with one space communicating with said air container and with the other space at substantially constant pressure, mercury in said device shifted back and forth through the capillary passage from one of said spaces to the other in response to variations in pressure in said air container, and a circuit opened or closed sense'being relieved by the passage of 'air past the mercury.

8. AcontrOI-device comprising an'a'ir container adapted to be subjected to the temperature of 'part of a heating system, -a device having enlargeti spaces connected by a capillary passage and arranged with one space communicating by an initial variation in said pressure, excess pressure 'due to subsequent variation 'in-the-same with -said=air containeriand with-the other space KEMPER P. BRACE.

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