US3474960A - Space heating system - Google Patents

Description

A. A. STRU YK SPACE HEATING SYSTEM Oct. 28,. 1969 Filed Oct. 10. 1967 mvzm-on 7 ANTDNY ALBERTUS STRUYK United States Patent 3,474,960 SPACE HEATING SYSTEM Antony Albertus Struyk, Hilversum, Netherlands, assignor to Vulcanus Aktiengesellschaft, Zug, Switzerland, a corporation of Switzerland Filed Oct. 10, 1967, Ser. No. 674,251 Claims priority, application Netherlands, Oct. 14, 1966, 6614549 Int. Cl. F23n N06 US. "Cl. 2372 7 Claims ABSTRACT OF THE DISCLOSURE A space heating system, preferably fired with liquid fuel and provided with a burner suitable for a variable flame image in a combustion chamber, at least opening into a flue for gases of combustion, to which a draft regulator is connected, fuel being supplied to the burner via an adjustable fuel regulator by which the fuel supply can be continuously adjusted between zero and a definite maximum value by displacing an adjusting device, which is spring urged in the direction of maximum fuel supply and which is furthermore controlled by an adjustable room thermostat.

PRIOR ART In known space heating systems of this type, a room thermostat is used, which, when the space temperature falls below a definite value, the set temperature closes an electric contact, whereby an electromagnetic control mechanism is energized and an electric igniter in the burner is made operative. Then the control mechanism displaces the movable adjusting device of the fuel regulator from a first position in which fuel supply is prevented, to a second position for maximum fuel supply. The igniter is made inoperative after a time which is sufficient for ignition of the burner. After the desired space temperature has been reached, the room thermostat renders the control mechanism inoperative, which in turn resets the adjusting device of the fuel regulator. The conventional device is permanently connected to the electric current and is adapted for intermittent operation (ON-OFF system).

However, there are several drawbacks in the automatic operation of the conventional device. Particularly the electrical equipment causes an increase in initial expense and also a rise in operating expenses due to power consumption. The reliability in operation of the device is also limited by the vulnerability of the complicated parts and by the dependence on the condition of the electric current. Absence of the current voltage or a strong decrease thereof due to overload of the electric current can render the device temporarily inoperative. Another drawback of the conventional device is the fact that, in each firing interval initiated by the room thermostat, the fuel regulator is compelled to supply the maximum quantity of fuel, for which a suitable quantity of combustion 'air is necessary, which is not available, however, if the flue draft, which is liable to strong fluctuations, is too low at the beginning of or during the firing interval concerned.

In space heating systems fired with liquid fuel, flue draft is known to play an important part with regard'to efficiency. Flue draft shows divergent values under different atmospheric conditions such as fog, wind blowing past the mouth of the chimney, intense irradiation of the chimney by the sun, etc. Furthermore, flue draft may undergo great changes during firing, specifically when the chimney is cold and the heating system is ignited. Herewith, flue draft gradually increases as the gases of combustion transfer more heat to the inside wall of the chimney. With low flue draft, little air is drawn in, so that if in this case the burner is supplied with an excess of fuel in relation to the quantity of oxygen available, the combustion is incomplete causing formation of soot and possibly stench. When the soot deposits on the various parts of the heating system, the heat transfer and, therefore, also the efficiency may decrease appreciably in the long run. A decrease in efficiency also occurs when the flue draft is too high and too much of the heat produced by the burner is drawn away to the flue. It is known that complete combustion can be furthered by application of a forced draft such as with an electric fan. However, the drawbacks of a fan are the increased operating expenses due to power consumption and the initial expense of the device. Other drawbacks of the fan are a disturbing noise, limited working life due to deposition of dust and dirt drawn in, and dependence on the condition of electric current.

In space heating systems fired with liquid fuel, draft regulation compensates for possible flue draft fluctuations at any moment so that in the combustion chamber near the burner there is a definite negative pressure, which can be at most equal to the available draft supplied by the flue. In order to ensure that the firing process always proceeds in such a way that the supply of combustion air is suflicient for sootless combustion, there should always be a definite negative pressure near the burner in the combustion chamber which pressure is adapted to the fuel consumption. This adapted negative pressure is called requisite draft. It is important to keep the requisite draft always smaller than the available draft for the efficiency of the heating system and to permit compensation for any possible fluctuations in the available draft so that a quiet flame can be maintained. As has already been observed, the available draft can have a very low value upon ignition of the system and increase gradually thereafter. This implies that the fuel consumption must first be adjusted to a very low value, the requisite draft having an adapted value substantially corresponding with the low initial value of the available draft, while in case the desired space temperature is to be reached as quickly as possible, the fuel consumption is to be gradually increased subsequently, as the available draft which appears in practice to increase more than the requisite draft increases Continuous observation of changes of the available draft and regulating the fuel supply to the burner with an adapted requisite draft, which is to follow changes of the available draft, constitute a problem, the solution of which requires great attention and skill with manual operation.

OBJECTS OF THE INVENTION It is an object of the invention to provide a space heating system which is reliable in operation and has a high efliciency combustion without formation of soot.

It is another object of the invention to provide a wholly self-supporting space heating unit capable of regulating by simple means the fuel supply to the burner and the draft in such a way that at any moment the flames of the burner are adapted to a requisite draft following changes of the available draft and generally being smaller than the available draft, but for small values thereof approaching the available draft.

These and other objects and advantages of the invention will become obvious from the following detailed description.

THE INVENTION The space heating system of the invention is arranged so that the displacement of the fuel adjusting device is restricted in the direction of maximum fuel supply, either by a first control mechanism or by a second control mechanism, and the displacement of the said adjusting device in the opposite direction is restricted to a position in Whicha definite, minimum fuel supply is possible, said first control mechanism uninterruptedly cooperating with the room thermostat so as to increase the fuel supply when the space temperature falls and the reverse, said second control mechanism uninterrupte'dly cooperating with a measuring device supplying information dependent on the difference between the negative pressure in the flue and atmospheric pressure, in order to increase the fuel supply upon a rise of this pressure difference and the reverse, and that the fuel adjusting device continuously cooperates with the draft regulator, which is of a type, the sensitivty of which is adjustable, so as to increase the sensitivity thereof when the fuel supply is decreased by the operation of the control mechanisms and the reverse.

According to the invention, the room thermostat and the measuring device, which is a thermal sensor, may be of the liquid type and may be connected via a capillary tube with the first and the second control mechanism, respectively, which are each pressure-sensitive. The thermal sensor can be fitted in a measuring duct connected on one end to the atmosphere and connected with an open end at some distance from a closed wall heated by the burner, in such a way that after flowing along this heated wall the air drawn in by the flue flows past the thermal sensor in the measuring duct. The open end of the measuring duct may be funnel-shaped.

Both control mechanisms of the invention, which are rigidly connected to the fuel regulator housing, can be operative upon a pressure change in the same sense, in opposite directions on one side of a stop, connected to the adjusting device of the fuel regulator, which stop is also coupled with the draft regulator via a mechanical linkage. The draft regulator can be balanced so that within the adjustment range the adjustment shaft thereof always provides a torque, effecting a forced displacement of the adjustment device to the position for maximum fuel supply via the mechanical linkage.

Referring now to the drawings:

FIG. 1 is a diagrammatic representation of an embodiment of the device according to the invention.

FIG. 2 is a graph in which available draft and requisite draft are plotted.

FIG. 3 is a graph of fuel consumption as a function of time.

FIG. 1 is a diagrammatic representation of one embodiment of the space heating system of the invention. For the sake of simplicity, details which are not of importance for the invention have been omitted. The device according to FIG. 1 comprises a combustion chamber 1 and a space 1a located thereunder between base 2 of the device and a horizontal partition 2a. On base 2 is fitted a burner 3 opening through partition 2a into combustion chamber 1, which as usual at the top thereof opens into a flue 4 for carrying off the gases of combustion. Between back wall 2b of combustion chamber 1 and back wall 5 of the heating device, there is a duct, which on one side opens into the flue and on the other side communicates with a draft regulator 6. Base 2 is provided with apertures 7 to admit combustion air to burner 3.

Burner 3 is suitable for a variable flame 8, and is preferably of a type in which liquid fuel is vaporized. Via feed line 9, the burner receives liquid fuel from fuel regulator 10, which, in connection with the special adjust- .ment thereof to be described in detail, has been shown in a larger scale than burner 3 for reasons of clarity.

Fuel regulator 10 is a conventional type in which the level of the fuel supplied via line 11 is maintained by a float mechanism. On the outside of cover plate 12 of the fuel regulator housing, an adjusting knob 13 and the end of adjusting pin 14 can be seen. Adjusting pin 14 is continuously movable longitudinally between a first adjustment position a near the cover plate, in which fuel supply is prevented, and a second adjustment position b facing away from the cover plate, in which the fuel supply via line 9 is at its maximum. In the fuel regulator housing, adjusting pin 14 which is constantly spring urged towards adjustment position b is coupled with a dosaging mechanism for dosaging the quantity of liquid fuel flowing per time unit to burner 3. With adjusting knob 13, it is possible to select in a number of steps a corresponding number of optimum adjustment positions for adjusting pin 14. From these optimum adjustment positions, such as adjustment position b, an external control force can urge the adjusting pin against the spring action to an arbitrary adjustment position, such as adjustment position 0, and further to adjustment position a, in which the fuel supply to the burner is stopped. It is here observed that the distance between the adjustment positions a and b, which adjusting pin 14 can traverse, is relatively small and amounts to approximately 3 mm.

The displacement of adjusting means 14 in the direction of maximum fuel supply is restricted either by a first control mechanism 15 or by a second control mechanism 16. These control mechanisms are pressure-sensitive and are connected, via associated capillary tubes 17, 18 respectively, to a room thermostat 19 and a thermal sensor 20, respectively. Both room thermostat 19, which is adjustable by means of adjusting knob 21, and the balloon-type thermal sensor 20 are of a generally known type in which a thermostatic liquid is used in a transfer medium. The first and second control mechanisms 15, 16, respectively, can cooperate by means of their longitudinally displaceable control pins 22 and 23, with a stop connected to the end of adjusting pin 14 of the fuel regulator and shown as a plate 24 for reasons of simplicity. It should be noted that both pressure-sensitive control mechanisms 15 and 16 are rigidly attached to the fuel regulator housing, though this is not represented in FIG. 1, and that upon a pressure change in the same sense, caused by the liquid, they act with their control pins 22 and 23 on one side of plate 24, in opposite directions. Therefore, upon a pressure increase, control pin 22 of the first control mechanism 15 will move downward as viewed in the drawing, whereas control pin 23 of the second control mechanism 16 moves upward.

Thermal sensor 20 is disposed as a measuring device in a measuring duct 25, opening on one side into part of flue 4 to communicate directly with the chimney and on the other end, after passing through wall 5, with an open, e.g., funnel-shaped, end 26 into space Id at a short distance from a closed wall 27, which may be a wall of burner 3, in such a way that after flowing along this heated wall 27, the air drawn in by flue 4 flows along thermal sensor 20. The selection of wall 27 is dependent on the construction of the burner, but preferably this is a wall having a high temperature. The distance between the funnel-shaped end 26 and this wall has been selected so that the passing air flow effects a favorable heat transfer to the thermal sensor. To prevent the thermal sensor from responding to heat transferred by conduction of the measuring duct material, it is desirable that at least part of the measuring duct consist of material with low thermal conductivity.

Draft regulator 6, by which the sensitivity of damper 28 can be considerably changed with a relatively small change of the angle of swing of adjusting pin 29, is described in French Patent No. 1,530,460, granted on May 20, 1968. Damper 28 is pivotally connected to a plate 30 which is tiltable with little clearance in the draft regullator housing and is coupled to adjusting pin 29. When plate 30 is vertical, the damper sensitivity is greatest, but when the plate is tilted counterclockwise as viewed in the drawing, the damper sensitivity is reduced. FIG. 1 shows plate 30 in a tlited position. Via a mechanical linkage system 31, comprising links and levers not shown in detail, adjusting pin 29 of the draft regulator is coupled with adjusting pin 14 of the fuel regulator so that the sensitivity of the draft regulator damper increases with the fuel consumption of the burner decreasing, and the reverse. As for the range in which the damper sensitivity is to be varied, only a small angle of swing of adjusting pin 29 is required. Draft regulator '6.is particularly suitable to cooperate effectively with adjusting pin 14 which can be displaced a small distance as already mentioned in the foregoing. However, in this'connection 'it is desirable with a view to accurate cooperation, that linkage 31 is substantially free from lost motion caused by play in the pivot points. Draft regulator 6 is balanced by a counterweight 32 secured to tiltable plate 30 so that in the adjustment range, adjusting pin 29always provides a torque, effectiving via linkage 31, a forced displacement of adjusting pin 14 of the fuel regulator to adjustment position b.

The operation of the'space' heating system according to the invention will now be described with reference to FIGS. 2 and 3. By way of example, the available draft A and the requisite draft B have been plotted in FIG. 2, represented in mm. head, for a definite range of fuel consumption (in cubic centimeters per hour) of a space heating system of the invention connected to a flue. A condition is that the draft and the fuel supply to the burner are regulated so that at any moment the flames 8 supplied by the burner 3 are adapted to the requisite draft B to ensure that there is sufficient supply of combustion air for sootless combustion. From FIG. 2 it is seen that the available draft A supplied by the flue to the heating system increases with the fuel consumption, and consequently the quantity of heat produced is increased. To obtain the greatest effect from the heating system as a heat source, it is important that changes of the available draft A are always followed by the requisite draft B. Furthermore, it can be seen from FIG. 2 that in general the requisite draft B is smaller than the available draft A except as low values thereof approach the available draft, as is the case for a low fuel consumption V FIG. 3 shows a curve showing the fuel consumption (in cubic centimeters per hour) as a function of time (in minutes). This curve is typical of the heating system of the invention. In the time interval t t the fuel consumption increases considerably which is indicative of the fact that in the heating system according to the invention both the fuel regulation and the draft regulation are carried out efficiently, so that the requisite draft B can increase when the available draft A increases in accordance with FIG. 2. Such a situation occurs if the heating system is ignited when the flue is still cold. Starting from a low fuel consumption, the available draft, which is low at the beginning, is built up to a definite value as more heat is transferred to the inside wall of the flue. During the build-up of the available draft, the fuel consumption increases with a suitable requisite draft, e.g., from V to V cubic centimeters per hour.

The heat, which the thermal sensor 20 fitted in measuring duct absorbs at any moment from the heated air flow, is in fact not only dependent on the available draft A, but also on the fuel consumption which is related to the heat imparted by the burner to wall 27. It has been found that the information supplied by the thermal sensor to the second control mechanism 16 provides an effective regula tion of the fuel consumption and the draft upon changes of the available draft A.

When for example the available draft A increases, thermal sensor 20 will increase the pressure of the thermostatic liquid so that control pin 23 of the second control mechanism 16 rises. Fuel regulator adjusting pin 14, connected to plate 24, can reach another adjustment position while the contact with control pin 23 is maintained, or reach another adjustment position farther away from cover plate 12. In the latter adjustment position, which is limited by the position of control pin 22 of the first control mechanism 15, control pin 23 may or may not be in contact with plate 24, depending on the position of control pin 22 at the moment. As described in the foregoing, an upward displacement of adjusting pin 14 causes an increase in the fuel supply and simultaneously a decrease in the sensitivity of the damper of draft regulator 6. In this fashion, a suitable requisite draft B for the changed flames 8 of burner 3 is obtained upon a rise of the available draft A. If, on the contrary, thermal sensor 20 establishes that the available draft decreases, a correction takes place in opposite sense, the fuel supply being decreased and the sensitivity of the draft regulator damper being simultaneously reduced. Therefore, a modulating flame image can be visually observed due to the changes of the available draft.

Room thermostat 19 cooperates continuously with the first control mechanism 15 in such a way that, upon an increase of the space temperature, the fuel supply of the fuel regulator is decreased, and the reverse. To cause the heating system of the invention to operate in modulating fashion under all circumstances, it is necessary that the control mechanisms 15 and 16 can never bring adjusting pin 14 of the fuel regulator completely in adjustment position 11 whereby the fuel supply is completely blocked in this adjustment position. The restriction of the displacement of adjusting pin 14 to a position in which a definite minimum fuel supply is possible, the so-called economical position, can be realized in different ways, among other things by making the arrangement of the two control mechanisms 15 and 16 adjustable. The heat developed in said economical position can be advantageously used for heating a reservoir, not shown in FIG. 1, with water for household purposes. If it is necessary to make the heating system completely inoperative, this can be done by setting adjusting knob 13 of the fuel regulator at zero.

The heating system of the invention operates fully automatically as a completely self-supporting unit and has a high efiiciency and sootless combustion of liquid fuel. However, the low fuel expenses, which are related to the fuel consumption in the economical position, are not offset by the saving, obtained while the device is used as a space heating system.

It can be seen that the invention does not exclude the use of gaseous liquids. Some changes necessary therefore and within the scope of those skilled in the art, specifically with regard to the fuel regulator and the burner, come within the scope of the invention.

Various modifications of the heating system of the invention may be made without departing from the spirit or scope thereof and it is to be understood that the invention is to be limited only as defined in the appended claims.

I claim:

1. A space heating system fired with fluid fuel and provided with a burner suitable for a variable flame image in a combustion chamber opening into a flue for gases of combustion, to which a draft regulator is connected, fuel being supplied to the burner via an adjustable fuel regulator by which the fuel supply can be continuously adjusted between zero and a definite maximum value by displacing an adjusting device, which is spring urged in the directionof maximum fuel supply and which is furthermore controlled by an adjustable room thermostat, with the characteristic that the displacement of the adjusting device (14) of the fuel regulator (10) is restricted in the direction of maximum fuel supply, either by a first control mechanism (15) or by a second control mechanism (16), whereas the displacement of the adjusting device in the opposite direction is restricted to a position in which a definite, minimum fuel supply is possible, said first control mechanism (15) uninterruptedly cooperating with the room thermostat (19) so as to increase the fuel supply when the space temperature falls, and the reverse, said second control mechanism (16) uninterruptedly cooperating with a measuring device (20) supplying information on the difference between the negative pressure in the fine (4) and the atmospheric pressure near the burner (3), in order to increase the fuel supply upon a rise of this pressure difference and the reverse, and that the adjusting device (14) continuously cooperates with the draft regulator (6), the sensitivity of which is adjustable, so as to increase the sensitivity thereof when the fuel supply is decreased by the operation of the control mechanisms, and the reverse.

2. The heating system of claim 1 fired with a liquid fuel.

3. The heating system of claim 1 wherein the measuring device is a thermal sensor (20) and is fitted in a measuring duct (25), on one side opening into the flue (4) and on the other side connected to atmosphere with an open end (26) at some distance from a closed wall (27) heated by the burner (3), in such a way that after flowing along this heated wall the air drawn in by the flue flows along the thermal sensor in the measuring duct.

4. The heating system of claim 3 wherein the open end (26) of the measuring duct (25) is funnel-shaped.

5. The heating system of claim 1 wherein upon changes of the temperature or draft observed by the room thermostat and the sensor both control mechanisms (15, 16) which are rigidly secured to the housing of the fuel regulator (10), are operative in the same sense in opposite directions on one side of a stop (24) connected to the adjusting device (14) of the fuel regulator, said stop being also coupled with the draft regulator (6) via a mechanical linkage (31).

6. The heating system of claim 1 wherein the draft regulator (6) is balanced so that in the adjustment range the adjusting pin (29) thereof always provides a torque, elfecting, via the mechanical linkage (31), a forced displacement of the adjusting device (14) towards the posi tion for maximum fuel supply.

7. The heating system of claim 1 wherein the room thermostat (19) and the thermal sensor (20) are of the liquid type and are connected to the first and second control mechanism (15, 16, respectively) via an associated capillary tube (17, 18, respectively), said control mechanisms being pressure-sensitive.

References Cited UNITED STATES PATENTS 1,833,921 12/1931 Stem 2369 1,980,789 11/ 1934 Dillman. 2,164,882 7/1939 Miles 236-9 2,329,473 9/ 1943 Landon.

EDWARD J. MICHAEL, Primary Examiner US. Cl. X.R. 91-412

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