US2192632A - Burner control system - Google Patents

Description

March 5, 1940. v. o. BEAM BURNER CONTROL SYSTEM OiiginaI Filed June 20, 1936 INVENTOR. V14 MW 0. 55AM MM J M ATTORNEYS Patented Mar. 5, 1946 UNITED STATES PATENT OFFICE BURNER CONTROL SYSTEM Original application June 20,' 1936, Serial No. 86,381. Divided and this application May 27, 1937, Serial No. 145,087

1 Claim.

tion being to provide a simple, reliable, and efficient control system by which the thermal element controls the supply of gas to the burner or the energization of the igniter, depending upon whether the pilot flame is burning or extinguished and therefore whether the thermal element is hot or cold.

In accordance with the present invention, the thermal element operates suitable switching means which renders effective either the control circuit for the valve or the energizing circuit for the igniter, and when one circuit is rendered efiective the other is inoperative so that the valve cannot be opened unlessthere is a flame at the pilot burner and so that the igniter circuit cannot be completed when the pilot is burning. In the preferred embodiment of the invention, the switching means is a double-throw switch so arranged with respect to the actuating member which is connected to the thermal element as to render either circuit effective and at the same time render the other circuit ineffective.

The invention may be further briefly summarized as consisting in certain novel combinations and arrangements of parts which will be described in the specification and set forth in the appended claim.

In the accompanying sheet of drawings,

Fig. 1 is a view partly in elevation and partly in section showing as much of the gas control system as is material to the invention;

Fig. 2 is a diagrammatic view showing the electric circuits; and

Fig. 3 is a fragmentary detail view showing how the middle contact of a three-pole switch, which is preferably employed with the thermal element, is actuated when the thermal element is heated.

Referring now to the drawing, l0 represents the main burner to which gas will be supplied from the supply pipe Illa in which will be located the main gas valve lflb (see Fig.2). Any suitable type of main valve may be employed, such, for example, as a commonly employed diaphragm valve which is opened and closed by the supplying of gas pressure to and the exhausting of gas pressures from the chamber above the diaphragm through the action of an auxiliary solenoid-type valve. A valve which is controlled or actuated by a solenoid-is contemplated in the diagrammatic view of Fig. 2. I wish it to be understood, however, that the present invention, although useful in connection with gas-fired boilers, furnaces, heaters, and the like, is not necessarily confined thereto and when used in connection with gas-fired equipment of this type any suitable type of main valve may be utilized.

In igniting relation to the main burner is a pilot H which, as well as the thermal element to be referred to presently, forms a part of a unit having a tubular casing H which may be rectangularly or otherwise shaped in cross-section, this casing having a horizontal main portion and at its inner end an upright or vertical portion l2a. Gas is supplied to the pilot II by a pipe l3 extending through the horizontal portion'of the casing, the pipe I3 being connected to the pilot II in a manner such that there will be supplied to the latter a suitable mixture of air and gas. The pilot H extends up from the horizontal portion of the casing H in front of the upright portion I2a thereof and is steadied by the flange of a bracket l4 secured to the upper part of the vertical portion I2a of the casing. If a main valve of the diaphragm type is utilized, a bleed pipe is employed to carry the gas from the upper chamber of the valve when the latter is to be opened by gas pressure beneath the diaphragm, and in that case the bleed pipe may also extend through the casing l2 alongside the pilot pipe l3 and it may have a vertical extension alongside the pilot H but will terminate short of the upper end thereof. However, this bleed pipe forms no part of the present invention and will not be further referred to.

The thermal element per se forms no part of the present invention as'it is claimed in my pending application referred to. The present invention is not limited to the particular construction of thermal element therein shown and claimed but is preferred and is therefore illustrated in the drawing of the present application. It will be observed that this element I6 is composed of two members I60. and "5b which are pivotally connected by cross-pins I6c to the upper part relatively short may be termed the hot memher of the thermal element. The other member IBb of the thermal element is relatively remote from and shielded from the pilot flame by the hot member Ilia and may be termed the cold member of the element. This member is relatively long and is in the form of a lever which extends down beyond its pivot pin I60 and at its lower end is connected to the gas controlling element which it is to operate. From their pivot pins I60 to the upper common pivot pin I6d the two members I60. and I6b are normally of equal length, the axes of the three pivot pins forming the corners of an acute isosceles triangle when the element is cold. Though the major portion of the member Mia and the major portion of the upper part of the member l6b are parallel or substantially parallel, their upper ends are in this instance curved inwardly and placed in overlapping relation so that they can be conveniently connected together by the pivot pin Hid. As will appear presently, the heat differential between the member Mia and the upper portion of the member I6b causes the member I6a to expand linearly, and the two fixed pivot points I60, together with the fact that the members are pivotally coupled together at their ends, compel the relatively hot member to rock on its pivot I60 (to the right as the same is viewed in Fig. 1), thus imparting a similar rocking movement to the member I6b which thus acts as a lever to transmit at its lower end to the part to be actuated a movement the extent of which can be made anything desired by the appropriate selection of the ratio of the lengths of the two lever arms above and below the pivot I6c.

In this instance, the lower end of the lever member I6b is connected to a rod ll' which extends horizontally and forwardly through the lower part of the horizontal portion of the casing I2, and operates a double-throw switch I8 located within a switch box l8a secured to the casing I2 and consisting in this case of a movable switch member [8b which is formed of a suitable insulating material and is secured to the rod I1,

and three switch blades or contacts I80, id, and I8e which at their outer ends are suitably attached by screws I81 to the top of the switch box I8a and near their free ends are provided with contact points I8g. The middle contact I8d extends outwardly beyond the other two and is adapted to be engaged by the movable switch member I8b. Normally or when the thermostat is cold, the switch contact I811 engages the lower contact I80, as shown in Fig, 1, and when the thermal element is heated and functions in the manner pointed out above, it moves the middle contact into engagement with the upper contact I8e, as shown in Fig. 3.

By reference to Fig. 1, it will be seen that the pilot has a lower orifice IIa for the emission of gas to produce the flame F (shown by dotted lines in Fig. 1), which heats the adjacent member I6a of the thermal element, and an upper orifice I lb for the emission of gas for the flame F, also shown by dotted lines in Fig. 1, for igniting the main burner or burners, these two orifices being connected by a spiral slot Ilc so that when the gas is ignited at the lower orifice Ila it will travel up the slot and ignite the gas at the upper orifice IIb.

It is desirable that the pilot be lit by a suitable ignited generally electrically actuated, and while different forms of igniters may be employed, I prefer to use an igniter of the hot wire type generally in the form of a coil which on the passage of current therethrough becomes incandescent and therefore sufiiciently hot to ignite the gas surrounding it. To accomplish this desirable result, I mount on top of the vertical portion I2a of the casing I2 at the side of the two members of the thermal element a block I9 of heat-resisting material having a channel I9a extending horizontally therethrough, this channel being located alongside and facing the members of the thermal element and projecting inwardly beyond the same toward the pilot II, the inner end of the channel being located adjacent the lower orifice Ila-of the pilot II. In this channel is placed the igniter coil held in place by terminal screws 20a to which current supplying conductors may be connected.

This device functions as follows: The parts are so related that the gas emerging from the lower orifice Ila of the pilot envelops the coil 20, and when current ispassed through the coil and the latter becomes incandescent, it ignites this gas and therefore starts flames at the pilot orifices, but as soon as the flame F is established it is caused by convection to curl upwardly into the channel of the hot member I6a of the thermal element and no longer impinges upon the igniter coil so that its life is substantially unaffected by the heat of the flame.

In Fig. 2 I have shown an electric circuit by which the parts heretofore described may be utilized very effectively, the electric circuit or system herein illustrated being simple, reliable, and involving a maximum degree of. safety in the respect that it is impossible for the main valve to be opened to permit the flow of gas to the main burner or burners unless the pilot is burning and the thermal element heated, and in the further respect that the electric circuit cannot be completed through the igniter coil unless the pilot is out and the thermal element is cold. For operating the system, the ordinary house lighting circuit may be utilized the conductors of which circuit are designated 2|. The voltage is stepped down to a suitable safe voltage by a transformer 22 composed of a primary 22a and a secondary 22b. One terminal of the secondary is connected by a conductor 23 to one terminal or contact 24a of a room thermostat 24, the other terminal of which is connected by a conductor 25 to one terminal of a solenoid 26 which actuates or causes the actuation of. the main gas valve IDb supplying current to the main burner or burners. -When a diaphragm valve is used, this solenoid actuates an auxiliary valve which controls the supplying of gas pressure to and the exhausting or bleeding of gas pressure from the upper chamber of the diaphragm valve so that the latter may be closed or opened by gas pressure. The other terminal of the solenoid coil is connected by a conductor 21 to the upper contact We of the double-throw switch I8 adapted to be operated by the thermal element, as previously described. The lower con tact I80 of this switch is connected by conductor 28 to one terminal of the igniter coil 20, the other terminal of which is connected by a conductor 28a to one terminal of a manually operated singlethrow switch 29 which is preferably of the pushbutton type, the other terminal of the switch being connected by conductor 30 to the conductor 23 leading to one terminal of the secondary 22b of the transformer. The other terminal of the secondary of the transformer is connected by a conductor 3| to the middle contact 4811 of the switch I8 which contact is adapted to be actuated or moved from the position shown in Fig. 1 to the position shown in Fig. 3 by the movable switch member I8b which is shifted by ment.

Assuming that the main gas valve is closed and that the pilot is extinguished, in which event the thermal element is of course cold, the parts of the thermal element are in the position shown in Fig.1 and the middle contact |8d ofthe dou ble-throw switch I 8 engages the lower. contact Be. This establishes two conditions-it keeps the circuit through the solenoid 26 open, making it impossible for the main gas valve to be actuated even though the room thermostat calls for heat, and, at the same time, the engagement of the middle contact l8d of the switch l8 with the lower contact I80 makes it possible to energize the igniter coil 20 by closing the switch 29, attention again being called to the fact that the circuit through the ignited coil cannot be closed if the pilot is burning and the thermal element heated.

Accordingly, when the operator desires to start the furnace of other fuel-consuming apparatus, he has simply to close the switch 29 which will very shortly cause the pilot to be ignited. As soon as the pilot is ignited, the flame F rises and instantly after the ignition occurs the flame is out of contact with the igniter coil.

The flame now plays on the hot member Ilia of the thermal element, and while the cold member lGb remains relatively cool, the hot member expands and lengthens, changing the distance between its pivot I60 and the upper pivot l6d which pivotally connects the upper ends of the thermal members. As the hot member I60. gradually lengthens, it transmits lateral thrust to the upper end of the cold member Nib, causing the pivot pin lid to move in a clockwise direction as the same is viewed in Fig. 1 so that both members rock in a clockwise direction about their respective pivots 16c and move the switch actuating rod H to the left as the same is viewed in Fig. 1. The movement imparted directly by the long arm or member of the thermal element to the switch member I8!) is sufficient to move the middle contact iBd from the position shown in Fig. 1, i. e., in engagement with the lower contact I80, into engagement with the upper contact me, as shown in Fig. 3. It might be stated at this point that the time element of this part of the cycle can be varied by-adjusting the positions of the two contacts 18c and l8c with reference to the middle contact IN. This can be done by means of an adjusting screw l8h which extends through the top of the switch box 18a and engages the upper contact l8e. This contacts is connected with the lower contact l8c by an insulating spacer I81 which passes freely through an opening in the middle contact l8d so that by adjusting the screw the two contacts [8e lowered with reference to the middle contact Md.

The forward end of the rod I! is reduced and through a suitable support at the front of the switch box. A spring "a surrounding the reduced end of the rod I1 is compressed when the thermal eleand 18c can be raised or the thermal element acts in the manner Just explained on being heated, but when the pilot is extinguished and the thermal members are cool or reach equal temperature, the parts are restored to their former positions shown in Fig. 1, the spring l'la assisting this action.

When the thermal element is actuated by the pilot flame in the manner just explained so as to bring the middle contact lad into engagement with the upper contact l8e of the switch l8, the circuit may be completed through the coil of the solenoid 26 which, as previously pointed out, controls the supply of gas to the main burner, and the solenoid will be energized whenever the room thermostat calls for heat, and completes the circuit at the contact 24a. The middle contact of the switch l8 remains in the position just stated so long as the pilot flame is burning and the thermal element is heated, and, accordingly, the main valve will be opened and closed in accordance with the functioning of the room thermostat. Of course, if the equipment is used in a system not involving a room thermostat, the main gas valve can be controlled, i. e., caused'to open and close, by other means, such as a manually operable switch which would replace in function the switch automatically operated by the room thermostat.

It should be noted also that, during the entire period that the thermal element is heated by the pilot flame, not only is the-switch l8 maintained in a condition such that the main gas valve can be operated whenever desired or as required by temperature conditions in the vicinity of the room thermostat, but, during this period, it is impossible to complete the circuit through the igniter coil.

While I have shown the preferred embodiment of the present invention, I do not desire to be confined to the details or specific members described above, as the principle of the invention may be otherwise utilized, and I therefore aim in my claim to cover all modifications which do not involve a departure from the spirit and scope of the invention in its broadest aspects.

Having thus described my invention, I claim:

In fuel burning equipment, a main burner, a normally continuous pilot therefor, an igniter for the pilot, a thermal element adjacent the pilot in heat transferring relation thereto, a valve for supplying fuel to the burner, an actuating or controlling member therefor, a-source of current, a circuit for said member, a circuit for the igniter, a double-throw switch remote from said thermal element mechanically associated therewith, whereby the changes in the thermal element render either circuit effective, a thermostatically operated switch in the circuit for said valve actuating member and a push button switch in the igniter circuit, said thermostatic and manual switches cooperating with said double-throw switch to complete the circuit through either said member or said igniter depending upon whether or not the thermal element is heated by the pilot.

VILYNN O. BEAM.

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