US2308555A - Fuel burner system - Google Patents

Description

Jan. 19, 1943.

V. R. TATE FUEL BURNER SYSTEM Filed Aaron 22, 1940 Patented Jan. 19, 1943 FUEL BURNER SYSTEM Virgil Robins Tate, Milwaukee, Wis., assignor to 'Perfex Corporatiom Milwaukee, Wis.,' a corporation of Wisconsin Application March 22, 1940, Serial No. 325,383 4 Claims. (01. 236-1) The invention relates generally to fuel burner systems, and more particularly it relates to automatically controlled burner systems of the twostage type.

In the heating of some types of buildings it is often desirable to employ a heating system wherein the fuel burner is capable of two stages or rates of heat supply, so that when the room temperature is considerably below the desired value the burner will operate at a relatively high flame or intensity, and when the room temperature is relatively close to the desired value, the burner will operate at a lower intensity. Thus the high level flame is used to raise the room tem perature at a rapid rate until the room temperature reaches a level relatively close to the desired value and thereafter the low level flame serves to raise the room temperature at a lower rate until the desired room temperature is attained.

Since the provision of such a two-stage burner operation, in both gas and oil burning systems, involves the selective operation of a lowstage fuel valve and a high stage fuel valve, the provision of an automatic control therefor has heretofore been quite difiicult and costly. The difliculties involved in producing prior automatic controls for such a two-stage system have been caused principally by the fact that the most desirable fuel valves are of the solenoid-actuated type or the type which is actuated by electrically heated thermostatic means, and to actuate two such valves at different temperatures a relatively com-1 plicated room thermostat, having a snap action at each control temperature, has been required. Such snap action has been required at each control temperature because of the relatively heavy current drawn by the actuator of each Fig. 1 is a schematic view showing a two-stage 5 oil burner system embodying the invention.

Fig.2 is a similar view illustrating the invention as embodied in a two-stage gas fired heating system.

While I have illustrated in the drawing and will hereinafter describe in detailtwo embodiments of the invention, in both of which the high.

flame operation is attained by simultaneous opening of the two parallel fuel'feed lines, and low fiame operation is attained by opening one of these fuel feed lines and closure of the other line, it is to be understood that this disclosure is. made merely for illustrative purposes and that various changes may be made in the piping and valve arrangement and operation, and in the circuit arrangements, Without departing from the spirit and scope of the invention as defined in the appended claims. I

While the present invention is applicable to various types of heating systems and to either .oil or gas fired burners, it is herein disclosed in Fig. l as embodied in an oil burning, warm air heating system having a two-stage oil' burner of 1 the pot type, indicated diagrammatically by the reference numeral is. The fuel oil from a source such as a main supply pipe H flows through a by-pass I2 to the burner to provide fuel for a constant pilot flame, and under the control of a flow of fuel to the burner is stopped with the exception of the pilot fuel which continues to flow through the pilot by-pass I2.

Different arrangements of the valves I4 and I5 are, of course, possible for attaining selectively the desired high rate flow, low rate flow or shutoff of the main fuel supply to the burner, but as herein shown each of the valves l4 and I5 is used in cooperation with an adjustable metering means, and such metering means serves to modify and simplify the piping and valve arrangement. Thus the main fuel pipe II has the lated by metering valves i6 and [1' located in the branches l6 and I1 respectively. A similar metering valve i2 is also used in the pilot fuel by-pass I2. When with this particular valve arrangement the low rate of fuel feed is desired, the valve i4 is closed while the valve I5 is maintained open; and to shut oh the main flow of fuel, both of the valves 14 and ii are closed, although it will be noted, of course, that closure of the valve I5 would serve to shut oil. the main fuel flow.

To circulate the heating medium, such as the air heated by the burner I0, the system herein shown has a circulating fan driven by a twospeed motor 19. The fan motor is has its low speed winding constantly connected by wires and 2| across the line voltage wires 22 and 23, while its high speed terminal is connected to the wire 23 by wires 2| and 25 and a switch 26 which is adapted to be closed during high flame operation of the burner ill.

In the embodiment illustrated in Fig. 1 of the drawing, the valve I4 is normally closed, and is opened by an electrically energized actuator 21 which is in this embodiment illustrated as an electrically heated thermostatic means; while the valve I5 is normally open, and is closed by a similar electrically energized thermostatic actuator 28. The actuators 21 and 2| have similar thermostatic elements 21 and 2| respectively, each of these thermostatic elements being herein shown as a bimetallic element, and these thermostatic elements 21' and 28' are operatively connected to the valve members of their respective valves 14 and 15. The thermostatic elements 21' and 28 have electric heaters 21" and 2|" respectively, and these heaters are adapted to be energized under the control or the room thermobeing included in circuit with the transformer secondary 2| and the heater 21" o! the actuator 21. This circuit includes wires II and ll extending in series from one end or the secondary 2|, an auxiliary heater l2, and a wire 4| to the flxed end of the bimetallic element ll. From the contact 26 wires II and II extend in series to one end of the heater 21", while wires 4|, l1 and 4| extend in series from the other end 01' the heater 21" to the other end or the secondary 2|.

To control the other or low flame valve IS, the present invention provides a control circuit governed by the slow acting switch oi the room thermostat I in such a manner as to re quire but a relatively small current flow between these slow acting contacts To this end an energizing circuit is provided for the heater 2|" of the actuator 2| which is controlled by a stat 13 from a power source such as the secondary 29 of a transformer 3|, the primary 3| of which is connected acrossthe line voltage leads 22 and 23.

Electrical actuating devices adapted to open the valves l4 and I5, such as the electrically heated thermostatic actuators 21 and 2|, normally require a current flow which necessitates the use of snap action contacts in making and breaking the energizing circuits thereof, and it has been found that where two snap action contacts or switches are embodied in a single room thermostat, it is difficult and costlyto establish an accurate or relatively 'narrow diflerential in the thermostat. To overcome this difliculty the present invention provides a control circuit for the two electrical actuators 21 and 2| whereby a room thermostat having but a single snap acting switch may be employed. Thus the thermostat I: has its thermostatic element N, which is herein shown as a bimetal member, adapted, as it cools, to engage a cold contact 3| with a snap action induced by means such as a permanent magnet 31, the bimetal acting, of course, as an armature. As the thermostatic element II increases in temperature, it snaps away from the contact to a central or mid-position as shown in Fig. 1, and, upon continued temperature in-' crease, engages a stationary hot contact 3|. Thus thermally actuated switch II, and the thermally actuated switch N is in turn governed by the thermostat contacts |l-||. The energizing circuit to the heater 2|" comprises a wire ll connected at one end to the juncture of the wires 4| and 4| and at its other end to a stationary contact 52 of the switch The movable contact of the switch 50 is formed by a bimetallic element 53 which is connected by a wire 54 to one end oi the heater 2|", and the other end or the heater 2|" is connected by wires l5 and II in series to the juncture of the wires 46 and 41.

Where the valve I! is of the reverse acting or normally open type, the circuit through the switch II is normally open, which is to say, the thermostatic or bimetal element II is mounted so that when the element 53 is cold it is separated from the contact '2. With this construction the bimetal element is arranged when heated, as by means oi an electric heater 51, to move into engagement with the contact l2, and in this movement a snap action is obtained by means such as a permanent magnet which acts on the bimetal element N as it approaches the stationary contact I2. A similar snap action takes place, or course, in the opening of the switch II. The heater 51 has an energizing circuit comprising a wire N from the thermostat contact to one end of the heater I1, and a wire from the other end of the heater I! to the juncture of the wires ll and l|.

Thus when the operation of the burner has caused a room to reach a sufllciently high temperature, the closure 0! the thermostat contacts |5-||.serves to energize the heater 51, so that the bimetallic element [3 is heated and switch 5| closed with a snap action. The low flame valve 15 is thereby actuated from its normally open position to its closed positlom so that the main fuel feed is stopped at what might be termed a pilot level due to the continued flow of a pilot fuel supply through the by-pass l2. As the room cools the bimetallic element I! o! the room there mostat moves away from the contact 3| so as to break the circuit to the heater II. The bimetallic element ll of the thermal switch l| then starts to cool, and when it has stored suflicient power to overcome the attraction of the magnet 5|, the switch 8| snaps to its normal open position, thereby to de-energize the heater 2|" of the actuator 2| and allow the valve II to return to its normally open position. Fuel is then allowed to flow through the pipe [1 to the burner II at such a rate as to produce low flame operation of the burner. Ordinarily the low flame operation has a heat. producing action which is about one-fourth the heat producing action of the high flame operation of the burner. If the room temperature continues to fall despite the heat produced by the low flame operation of the burner, the bimetallic element 35 of the thermostat l3 continues to move to the left, and upon a suflicient drop in temperature, is engaged with the contact 36 with a snap action. The circuit to the heater of the actuator 21. is thereby completed, and the high flame fuel valve I4 is opened. The burner then operates at its high flame level so as to supply heat to the room at a comparatively high rate. To prevent over-shooting of the room temperature the auxiliary heater 4! is preferably employed to apply added or supplemental heat to the thermostatic element 35 during periods ofv high flame operation. This auxiliary heater 42 operates in a known manner to compensate for time lag or sluggishness in the heating system. When the thermostat l3 opens the contacts 35-35, the circuit to the heater of the actuator 21 is broken, so that the fuel valve I4 is closed and the burner is returned to its low flame operation.

During the low flame operation of the burner, as Well as during. the off periods of the main burner, the heating medium, such as the warm air, is circulated continuously by the warm air fan, since the motor of the warm air fan is continuously connected across the linevoltage leads through the low speed winding of the fan motor i9. During periods of high level operation of the burner ID, the high speed winding of the fan motor I9 is energized through the closure of the switch 26. To effect such closure the switch 26 is in the present instance constructed in the form of a warp switch having a bimetal element 60 which in its normal or cold position is separated from the stationary contact 6| of the switch. To close the switch 26, a heater 62 is provided having one end connected by wire 63 to the juncture of the wires 4'! and 48, While the other end of tinues for a short time after the opening of the a thermostat switch 3536.

When the operationof the heating system is to be discontinued for the season, a main valve 63 in thefuel line II is closed, and a line switch 64 in the line voltage lead 22 is opened.

In Fig. 2 of the drawing the invention is em-' bodied in a warm air heating system having a gas fired burner Hi, the fuel supply connections of which are substantially the same as those shown in the oil burning system of Fig. 1. In this system, however, the main fuel line H has two parallel branches l6a and Ila in which valves Ma and l5a are mounted. The branch pipes lSa and Ho have similar metering valves i6 and ll. The fuel lines lSa and "a terminate in individual burner elements b and [1b which are herein shown diagrammatically, one above the other, it being understood that this showing is merely illustrative and would be different in practice. In the embodiment of Fig. 2, however, the low flame valve l5a is of also the direct acting type, in that it is normally closed, as indicated by the arrow beside the valve stem, and is opened when its actuator 28a is energized. The actuators 21a and 28a of both of the valves' are of the solenoid type, having actuating coils 21b and 281) respectively. In the embodiment of Fig. 2 all of the circuit connections are the same with the exception of the thermal switch which has its bimetal element 53' mounted so as to be normally closed when the element 53' is cold, and the switch 50 is opened by the heating action of its heater 51'. The disposal of the magnet 58' is of course such as to bias the switch member 53 to its'switch'closing position.

When a relatively high temperature in the room causes the thermostatic element 35 of the room thermostat i3 to close its contacts 3538, the heater 51' is energized, thereby to cause heating of the bimetal element 53 and consequent opening of the thermal switch 50 with a snap action. Opening of the switch 50' de-energizes the coil 28b of the actuator 28a of the valv I5a so that the valve |5a closes. This results in shutting off all of the fuel to the burner i 0 with the exception of the pilot fuel which continues to flow through pilot by-pass I la and pilot metering valve I2 to a pair of conventional gas pilot burners. When a reduction in room temperature causes opening of the contacts 35-38 of the room thermostat, the warp switch 50 is allowed to cool and thereby closes the circuit to the coil 28b of the solenoid actuator 28a. This opens the valve l5a so as to produce low flame operation of the main burner, which low flame operation continues so long as the thermostatic element 35 remains in its switch opening relation to contact 38. If the thermostat I3 continues to cool, it causes closure of the thermostat contacts 35-36 with a snap action, thereby to open the high flame valve Ma and cause high flame operation of the burner i0. Soon after the opening of the valve Ma the high speed fan switch 26 is closed due to the action of its heater 52. When the room thermostat has been heated sufiiciently to open contacts 3536, the high flame fuel valve I40: is allowed to close, and the high speed fan switch opens soon thereafter. Operation of the burner then continues at its low flame level until heating of the room causes closure of the contacts 3538 of the room thermostat.

From the foregoing it will be apparent that the present invention provides a new and improved two-stage fuel burning system wherein a comparatively simple room thermostat may be employed to overn the operation of the two elec trical actuators which are required for controlling the fuel supply. It will be apparent that with the present system the control thermostat has but a single snap action, so that the problem of providing an accurate differential in the thermostat is simplified.

What is claimed is:

1. In a two stage control system for fluid fuel burning means, the combination of, fuel supply means for said fuel burning means including supply piping having a single portion and a branched portion, a first fuel valve for controlling the flow of fuel through said single portion, a second fuel valve for controlling the flow of fuel through one of the branched portions, a first electrically operated device for controlling said first valve and arranged to open said first valve when energized and to close the same when deenergized, a second electrically operated device for controlling the second valve, a three position thermostatic switching mechanism located so as to respond to the demand for heat from said fuel burning means, said thermostatic switching mechanism assuming a first position when the demand for heat is satisfied, a second position when the demand for heat is light, and a third position when the demand for heat is heavy, electrical connections controlled by said thermostatic switching mechanism for controlling said electrically operated devices, said electrical connections being arranged to cause closing of both fuel valves when the thermostatic switching mechanism is in its first position, to cause opening of said first fuel valve when the thermostatic switching mechanism is in its second position, and to cause opening of the second fuel valve when the thermostatic switching mechanism is in its third position, an electric heater associated with said thermostatic switching mechanism for applying false heat thereto, and means including said electrical connections for energizing said heater [when the thermostatic switching mechanism is in its third position while substantially deenergizing said heater when the thermostatic switching mechanism is in its second position.

2. In atwo stage control system for fiud fuel burning means, the combination of, first and second normally closed fuel valves for cont-rolling the supply of fuel to the fuel burning means, opening of the first valve providing a low rate of fuel supply and opening of the second valve pro viding a high rate fuel supply, first electric motor means for operating said first valve, second electric motor means adapted when energized to open said second valve, a three position thermostatic switching mechanism responsive to the demand for heat, said switching mechanism comprising first and second switches, the first switch being closed when the temperature to which the switching mechanism responds with said thermostatic switching mechanism,"

means providing an electric circuit including said secondswitch for energizing said second electric motor means and said electric heater when the second switch is closed, a slow acting relay for is above a predetermined value, the second switch beheat is heavy, snap action means for causing said switching mechanism to move with snap action between its second and third positions, said switching mechanism being arranged to move slowly between its first and second positions, a slow actingrelay moving from one position to another a period of time following movement of the switching mechanism between its first and second positions, electric heating means associated with said thermostatic switching mechanism for adding false heat thereto, means including electrical connections between said switching mechanism said slow acting relay and said control means for causing a supply of heating medium at a high rate when the switching mechanism is in its third position, at a low rate when said mechanism is in its second position, and for substantially discontinuing said supply when the switching mechanism is in its first position, and means including said electrical connections for energizing said electric heating means when the switching mechanism is in its third position and for substantially deenergizing the same when the switching mechanism is in its second position.

4. In a two stage control system for a tempera ture changer, the combination of, control means for controlling the effectiveness of the temperature changer, said control means being effective selectively to cause the temperature changer to operate at a high rate, at a lower rate or to be substantially inoperative, a three position thermostatic switching mechanism located so as to respond to the demand for temperature changing, said thermostatic switching mechanism assuming a first position when the demand for temperature change is satisfied, a second position when said demand is light, and a third position when said demand is heavy, snap action means for causing said switching mechanism to move with snap action between its second and one of said positions, said switching mechanism being arranged to move slowly between said second and'the other of its positions, a slow acting relay controlled by said, thermostat switching mechanism and moving from one position to. another a period of time following movement of the switching mechanism between its second and said other of its positions, electric heating means associated with the thermostatic switching mechanism for adding false heat thereto, means for V energizing and deenergizing said electric heating controlling said first motor means, and means 1 providing an electric circuit including said first switch for controlling said relay.

3. In a two stage control system for heating means, the combination of, control means for controlling the supply of heating medium to the heating means, said control means being effective selectively to cause supply of heating medium at a high rate, at a low rate, or to substantially discontinue the supply of heating medium, a three position thermostatic switching mechanism located so as to respond to the demand for heat,.

said thermostatic switching mechanism assuming a first position when the demand'for heat is satistied, a second position when the demand for heat is light, and a third position when the demand for means in a manner tending to cause cycling of the thermostatic switching mechanism between its second and said one position whereby the electric heating means supplies power foroperating the thermostatic switchingmechanism against said snap action means, and means including electricalconnections between said thermostatic switching mechanism, said slow acting relay and said control means for causing the temperature changer to operate at said high rate when the switching mechanism is in its third position, at said lower rate when said mechanism is in its second position, and for rendering the temperature changer substantially inoperative when the switching mechanism is in its first position.

V. ROBINS TATE.

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