USRE20210E - Safety system - Google Patents

Description

Di" 22, 1936. D. D. KNOWLES SAFETY SYSTEM Original Filed May 26, 1928 2 Sheets-Sheet 2 INVEN TOR flewey D Know/e ATTORNEY Reissued Dec. 22, 1936 Re. 20,210 f Dewey D.

Knowles, Forest Hills, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Original No. 1,809,280, dated June 9, 1931, Serial No. 280,710, May 26, 1928. Application for reissue October 29, 1932, Serial No. 640,302

11 Claims.

The subject matter of this application is related to my application Serial No. 164,625, filed January 29, 1927.

My invention relates to safety control systems and particularly to control systems intended for a use in connection with furnaces using a liquid or gaseous fuel.

One object of my invention is to provide a safety system that will be actuated by a failure of the fuel supply pressure and will so operate as to pre'- vent the accumulation of unburned fuel in the furnace upon renewal of the fuel-supply pressure- Another object of my invention is to provide a safety control system that shall be controlled by a flame of the burning fuel.

Another object of my invention is to provide a safety control system that shall be controlled'by, and in accordance with, the conductivity of an ionizable gap.

.Another object of my invention is to provide a 20 safety control system that shall be controlled by, and in accordance with, the conductivity of an air gap subjected either directly or indirectly to the flame of a furnace or to a fluid medium.

Another object of my invention is to provide a safety system actuable in accordance with the conductivity of a gap normally subjected to' a moving fluid medium upon interruption of the flow of the medium.

Another object of my invention is to provide a safety system that will disconnect a furnace fuel-supply system. or other apparatus from a source of liquid or gaseous fuel upon ,failure of a flame of the furnace.

A still further object of my invention is to proof such a character as to retain the instantaneous-operation feature throughout its entire life and under substantially all ordinary conditions of operation of a furnace.

In practicing my invention, I provide a control means for the fuel, actuable in accordance with the conductivity ofan air gap subjected either directly to a flame of the furnace or indirectly thereto or to the heated products of combustion of the burning fuel. 'In a preferred form of my invention, as practiced at present, I associate with the electrodes defining an ionizable gap the conductivity of which is to be measured by an electricto the use of such an electric-discharge device.

5 In the drawings:

vide a system of the class described that shall be" discharge device, the operation of which is con- Figure 1 is a view, partly diagrammatic and partly sectional, of a furnace heater equipped with a preferred embodiment of my invention.

Fig. 2 is a diagrammatic view of an alternative form of my invention.

Fig. 3 is a view partly diagrammatic and partly sectional, of a still further modification of a device embodying my invention, and

"Fig; 4 is a view, partially diagrammatic and partially in side elevation, of another modification of a device embodying my invention;

' Referring m'ore particulanly to Fig.'1 of the drawings, a furnace or heater Ii is provided with a mobile-fuel-supply line i3 and a plurality of burners i5. Y 15 A supply line 13 feeds also a pilot flame ll which is usually continuous.

A grid glow tube-Ill is operatively associated with the furnace- I l and comprises a container or casing 2|, a cathode 23, an anode 25 and a con-.

trol grid 21. A conductor 5 is.connected to the 20 grid 21 and extends, throug an insulating bushing 3! in a wall of the furnace, into the space normally occupiedby the upper end of the pilot flame I1. The inner end of the conductor 29 is, of course, connected to a suitable electrode material capable of withstanding continuously the high temperature of a flame. The anode 25 is connected, by a conductor 33, to a second, electrode having its inner end located in the space occupied by the lower end of the flame ii, an insulating bushing 35, similar to the bushing 3|, being provided therefor. Instead of connecting the anode 25 to an electrode, as just described, the conductor 33 may be connected, either conductively or capacitatively, to the fuel-supply line l3 with substantially as good results. I preferably make the electrodes connected to the wires 29 and 33 of a heat-resisting and non-oxidizable alloy, such as nichrome or the like, and it is also essential that the insulating bushings 3i and 35, be made of a material having a very high surface resistivity. The grid glow tube hereinbefore described is constructed according to the disclosure of a co-pending application filed by me November 19, 1926 5 bearing Serial No. 149,290 and assigned to the- Westinghouse Electric & Manufacturing Co.

As explained in my earlier application, thegridglow tube I9 is a discharge device comprising a plurality of electrodes 23, 25 and 21 iminersedin so an atmosphere of a gas such as neon. The gas is maintained at a pressure of the order of 2 mm. of

mercury.

When an alternating potential is impressed between the anode and the vcathode, no current 5" will fiow therebetween, as the gridis eflectively insulated, but, upon establishing a grid leakage path, the gas in the tube will become ionized and a substantially rectified current will flow in the output circuit thereof. The transition from the non-conductive to the conductive condition of the tube is abrupt.

An output circuit is connected between the cathode 23 and .the anode 25 and comprises an actuating solenoid 31, a resistor 39 and the secondary winding 4| of a transformer 43. The primary winding 45 of the transformer is connected to a source 41 of alternating current.

A core member 49 of magnetic material cooperates with the coil 31 and is suspended from an arm II which is permanently connected to a fuel-supply -controlling valve 53 interposed in the fuel-supply line I3. The arm II is extended beextension 3| pivotally con- The lever 83 has a fulcrum point of its connectionwith nected to a lever 33. 35 intermediate the the link II and a handle 91 which projects beyond A spring II .is connected between the .end of, the lever opposite to the handle 41 and to thecasing and tends to so move closed position.

A movable latch element 93 is nected to, and carried by, the extension 8| and cooperates with a movable detent or latch 95 to retain the valve in its closed position. The latch 95 is connected to a bell crank 91, one arm 99 of which has a biasing spring IIII connected thereto, and .which may also be controlled by an electromagnet I03. The electromagnet is energized from a suitable source I95.-the circuit being controlled by a switch arm I51 and a fixed contact member I09 associated with, and controlled by. the relay 33. A biasing battery III, in series with a grid-leak resistor I I3, is connected between the grid 45 and the filament 53 of the pivotally contube and biases the grid negatively with respect to the filament. A conductor is connected to the grid 45 and to one terminal of the-resistor II3, as well as to aninsulated electrode II1, projecting through a wall of the furnace, the inner end of the electrode being located in the upper portion of the space normally occupied by a pilot flame Ill. The filament 43 of the tube is com nected to a metallic portion I2 I of the pilot burner through a biasing battery I23, the battery serving to impart a positive potential to the flame-ionized path and, consequently, a positive potential to the grid 55 when the flame is burning. A source of electric potential I25 energizes the filament 93.

Referring more particularly of furnace and fuel-supply mechanism comprising a metal IIIJ'naee-casingIILhaVIng associated detail in connection 5| has afilament 53,

maintain the valve II in its heavy weight I 93 being connected to Fig. 3 of the drawings, I have here illustrated another form an electric motor I35. The devlce'l33 may be i any positive pressure blower usually employed in connection with oil burners and is eifective to forms quantity of oil through a supply conduit I31 to be atomized by suitable means well known in the art and to burn I. At the same time, air is supplied, under pressure, within the conduit I39, whereby a highly effective flame is obtained within the furnace casing I3I.

A supply circuit for the control system and for the motor may comprise conductors HI and I43,

the supply of energy from which to the motor and to the safety system is controlled by protecting devices well known in theart. A relay within the furnace casing in the supply circuit to the motor comprises a coil I41, a core I49, having associated therewith a contact bridging member I5I and suitable substantially fixed contact members.

A gridglow tube I53, of the kind described in is provided and has its cathode connected to one. terminal of the coil I41. The other terminal of the coil I41 is connected to one terminal of the secondary coil I 55 of a suitable transformer comprising the usual core I51 and a primary windwith Fig. l of the drawings,

ing I58. The other terminal of the secondary winding I55 is connected 'to the anode of the grid glow tube and is also connected to ground. The control grid of the grid glow tube is connected to an electrode I59 extending through an insulating bushing I5I mounted in the wall of the casing iii, the electrode extending well into the zone or space normally occupied by the flame.

An ignition transformer is provided and comprises a primary winding I63, the usual core member and a secondary winding I65. One terminal of the secondary winding I95-is connected to ground while the other terminal thereof is connected to a suitable ignition device I61, usually constituted by a spark gap.

The primary coils or windings I58 and I53 are connected by suitable conductors to the supplycircuit conductors I and I49.

Referring to Fig. 4,- I have there illustrated another modification in which a control air gap is located in the stack or flue ill of a furnace I13, which is supplied with mobile-fuel through a supply pipe I15. A valve I11 is connected in the pipe and is held in the open position by the action of a core I19 connected to one end of a lever IOI mounted on the valve stem, a relatively to the other end of the lever. An electric discharge device I95, as hereinbefore described, has its anode connected to one electrode I81 located in the sta'ck or flue. A second electrode I89 cooperates with the electrode I91 to define a gap the conductivity of which is a'ifected by the products of combustion of the furnace, and is connected to the control electrode of the device I35. The cathode of the device is electrically connected to one terminal of a secondary coil I9I of a transformer the primary coil I93 of which is energized from a suitablesource of potential (not shown). The other terminal of the secondary coil I9I is connectedto one terminal of a relay coil I95 operatively associated with the core I19.

Referring more particularly to Fig. 1 of the drawings, it is assumed that" the pilot .fiame is burning and that the transformer 43 is ener- 'gized, whereby the grid glow tube I9 is energized between the cathode and the anode. As is pointed out in my co-pending prior application, a discharge will be maintainedin the tube so long electrical y as a leak e path is maintained between the anode and the rid, and, in Fig. 1 of the drawings. this leakage, path is provided more particularly by the piloti flame. I have found that the conductivity of amine is sufllciently high to prevent the accumulation of a blocking charge on the grid 31 of the tube so that, as long as the pilot flame is burning, a current will flow in the circuit including the anode and cathode of the tube, the coil 31, the resistance 33 and the secondary winding it. I

The resistance of the resistor 33 is so selected that the current traversing the coil 31, as long as the pilot flame is burning, is just suflicient to retain the core 43 in the position illustrated in Fig.4 of the drawings, it being understood, of course, that suitable initial adjustments have been made. To start the operation of, the furnace, it is merely necessary that the core member 45 be forced downwardly against the action of the weight 55, thus opening the valve and permitting ignition of the fuel issuing from the burners I5. Should the pilot flame I1 be extinguished, for any reason whatsoever, the leakage path provided thereby between the grid electrode and the anode of the grid glow tube would be no longer present and the grid 21 would acquire a sufllciently high negati e charge to stop the discharge between the anode and the cathode, all as explained in my application Serial No. 149,290. As soon as the glow discharge between the anode andthe cathode ceases, the coil 31 is, of course, deenergized, whereby the weight 55 is permitted to" drop and to close the valve to shut off any further supply of fuel.

It is, of course, obvious that, when the coil 31 is not energized, the valve 53 cannot be kept open except by manually holding the core 43 down against the action of gravity on the weight 55, and the likelihood of the furnace being filled with unburned fuel when the pilotflame is not burning is, therefore,-very remote.

It will also be obvious that the occurrence of flame at the electrodes 3|, will result in reductionto a low value of the potential diflerence therebetween. Hence, sputtering or arcing of the electrodes is absent, thereby prolonging their useful life.

While Fig, 1 shows the use of a grid glow tube in combination with a safety control system, I have found that an ordinary thermionic amplifying device may be used, particularly in places where an alternating-current supply of electric energy is not available. Such a system is shown in Fig. 2 of the drawings. By suitably adjusting the voltage of the biasing batteries H3 and I23, the potential of the grid 35 may be maintained so long as the pilot flame H3 is burning.

As is well known in the'art, a positive bias on the grid of a thermionic tube permits the flow of space current, and this current is utilized to energize the relay 53 whereby to maintain the contact arm ll1'ln engagement with the contact I member III3.

So long as the I31 is in engagement with the contactmember its, the' electromagnet III Upon extinction of the pilot flame, the gridbias balance is destroyed, the grid being then biased negatively by the battery III to a potential sumcient to block the tube and stop the current in the relay 59. Switch arm I01 is then moved to disengage contact I33, whereby electromagnet I03 is deenergized and valve 11 is permitted to close under the action of spring 9i, the movable detent 95 being moved to the left into operative position under the influence of spring IB'I.

In its downward travel, the latching'element 33 passes by the end of the latch or detent 95, and the, subsequent engagement of member 93 with the under portion of the member 95 prevents the extension 3i and, therefore, the rack bar 19, from being raised by the lever 83 until the detent 35 is moved toward the right by the action of electromagnet I03.

It is thus apparent that, by utilizing my invention in connectionwith gas or oil-fired furnaces or the like, it will be substantially impossible for a careless workman to.open the main fuel-supply valve and to leave it in the open position if the pilot flame is not burning.

Referring more particularly to Fig. 3 of the drawings, it is assumed that a room thermostat (not shown) closes to effect closing of the cir- "cuit of the motor I35, whereby oil is forced into the casing I3I in an atomized condition and-is ignited by the ignition device I61 in a manner well known in the art. Theelectrode I53 is so located as to project into the flame and a conducting or grid leakage path is, therefore, provided between the grounded anode of the grid glow tube I53, the usually more or less grounded metal casing I3I and the electrode I59, the outer end'of which is connected to the control grid of bridged by member I5I, should be included in the system, to permit of starting up the systemand a conductor I91 is shown as being provided for this purpose. As this part of the system constitutes no part of my invention, it is not illus trated or described in detail.

If, for any reason, the supply of an atomized mobile fuel should be interrupted, as may happen in case of a slug of water occurring in the pipe line, the flame would be extinguished and the tendency of the room thermostat would, *of course, be to remain closed for a certain length of time, which may be as much as 60 seconds, during which time the motor would continue to operate and a supply of atomized fuel might collect In the burner casing I3I. As soon as the flame is extinguished, however, the grid leakage path will no longer exist, so that the current traversing the coil I" of thecontrol relay will be interrupted within a few seconds, whereby the motor-control circuit is opened and the motor is shut down. The initial control means is thus a normally continuously energized closed-circuit means, which is, also, avoltage-responsive means.

While Figs l and 2 show the use of a pilot flame as constituting a conducting path between two electrodes connected, respectively,.to a control grid and another electrode of the electrical discharge device, it is possible also to use the main flame of the burning fuel to provide this However, the device embodying my invention is not restricted to the use of a flame-ionized products of combustion thereof, the main requisite being that the gap is ionized to a suflicient extent to increase its conductivity to suchvalue as will permit a current to flow therethrough to operate the control-circuit means. Such location is shown in Fig. 4 of the drawings.

It is, of course, obvious that it is not always necessary to employ two special electrodes, as shown in Figs. 1 and 4. Only one special electrode-may be utilized, as shown in Figs. 2 and 3, the other electrode being constituted by the pipe l2| in Fig. 2 or by the grounded casing 'III of Fig. 3. i

As my invention, in its broadest aspects, is not limited to a control valve or *even to an electric motor, I prefer to use the phrase an actuable means to designate the device, appliance, or system, which is controlled or actuated by, and in accordance with, my invention.

I have elected to show the operation of an electrical discharge device in connection with. a.

safety system for fuel burners and have also shown and described specific locations of the electrodes in connection therewith. Obviously, nLv system is not limited thereto and I may make modifications therein without invading the field of the pertinent prior art, and I desire, therefore,

that the appendedclaims shall be limited in scope only as demanded by such-prior art.

I claim as my invention: I

1. In a fuel-supply system of the general type having means for burning mobile ifuel, said means including a pilot burner, current-operated means-for controlling the flow of said fuel, means including an electric-discharge device having main electrodes and a control electrode, a source of potential, an output circuit for the discharge device including said potential and fuel-fiow-controlling means, a pair of conductors making contact with the flame of said pilot burner and connections between one of said conductors and one of said main electrodes and between the other of said conductors and said control electrode.

2. In a fuel-supply system of the type including a fuel burner and means for supplying fuel thereto, a current-controlled shut-off means for said fuel-supply means, conducting terminals positioned in the path of flow of the products of combustion of said burner, an electric-discharge device having main electrodes and a control electrode, means for including said main electrodes in circuit with said shut-off meansand a source of voltage, and conductors connecting one of said terminals to one of said main electrodes and the other said terminal to said control electrode.

3. Ina fuel burner system of the type includinga fuel-supply means and a shut-off device therefor, current-controlled means for controlling said shut-ofl device, including a gaseous electricdlscharge device having main electrodes and a contrclelectrode between them, said main electrodes being connected in series with said current-controlled means and a source of alternatmain "electrodes, source .of

20,210 conducting path, and this is illustrated in Fig. 3.

ing voltage, and conductors, connected respectively to said control electrode and one of said main electrodes, electrically connected by contact with the flame of said fuel.

4. In a fuel burner of the type including a fuel-supply means, an electrically actuated control means for maintaining fuel flow through said fuel-supply means and a normally-closed-circuit, including an electric-discharge device having a casing having a plurality of main electrodes and a control electrode within it, said principal electrodes being in circuit with said control means and a source of voltage, said control electrode being connected to a conductor positioned in the path of flow of the products of. combustion of the burner, and one. of said main electrodes being connected to another conductor positioned in said path.

5. In combination with a burner, means for controlling the flow of fuel thereto and spaced electrodes positioned in the path of flow of com- .bustion products from said burner, electrical means operative when combustion products from said burner contact said electrodes to cause between said electrodes an electric discharge so minute as tobe incapable of igniting fuel and as a result of such discharge to render operative said fuel controlling means.

6. In combination with a burner, means for controlling the flow of fuel thereto, a pilot burner for igniting said fuel, and spaced electrodes positioned in the pathof flowof combustion products from said pilot burner, electrical means operative when combustion products from said pilot burner contact with said electrodes to cause between said electrodes an electric discharge so minute as to be incapable of igniting fuel and as a result of such discharge to simultaneously render operative said fuel controlling means.

7. In combination with urner, means for controlling the flow ofjfuel thereto and spaced electrodes positioned in the path of flow of combustion products from said burner, electrical means operative when combustion products from said burner contact said electrodes to cause between said electrodes an electric discharge so minute as to be incapable of igniting fuel and for amplifying said discharge and as a result of such discharge to render operative saidfuel controlling means. I

8. In combination with a burner and electrically operated means for controlling the flow of fuel thereto, an electrical control device normally operative to block current flow in circuit with said electrically operated means and a source of electrical power; .a second circuit including said control device, and spaced electrodes positioned in the path of flow of combustion productsfroi'n said burner whereby combustion products contacting said electrodes will cause an electric discharge between said electrodes so minute as to be incapable of igniting fuel,,which discharge renders said control device operative to permit current flow.

9. In combination an electric discharge device having a control electrode and a plurality of principal electrodes and a gaseous medium, said device being of the type that has'an energized condition and a deenergized condition and is capable only of abrupt transition from one condition to the other, means for impressinga potential diiference between said control electrode and one of said principal electrodes to maintain said discharge device in one of said conditions,-

and means for controlling the condition oi said device, said means comprising an'electrical conduction path including a space and means for producing combustion in the region of said space, whereby said space is ionized by combustion products. and means for directly coupling said conduction path between said control electrode and said one '01 said principal electrodes whereby in the absence of a flame in said space a potential difference exists across said space and occurrence of a flame in said space produces a decrease in said last-named potential diii'erence and a change in the condition of said discharge device.

10. In combination a plurality of cold electrodes disposed in an evacuated containercontaining a gaseous medium, means for impressing an energizing potential between said electrodes,

a third electrode interposed between said first namedelectrodes and normally insulated therefrom, means, comprising an-eiectricaLconduc-v tion path including a gap, directly coupled between said third electrode and one oi said flrst-' named electrodes, whereby a diflerence oi potential is. normally impressed across said gap and between said third electrode and said one of said first-named electrodes and the passage of a space ,current between said first-named electrodes is blocked, and means for producing combustion in the region of said gap wherebysaid gap is ionized by combustion products, and said third electrode is electrically connected to said one of said iirstnamed electrodes, thereby substantially at the same time to reduce the potential difference across said gap and to render said third electrode ineflective' in blocking a space current between said first-named electrodes. V

1i.-In combination an electric discharge device having. a control electrode and a plurality of principal electrodes in a gaseous medium, said device being of the type that has an energized condition and a deenergized condition, is capable 6 only of abrupt transition from its deenergized condition to its energized condition as the distribution of potential between said control elec-: trode and said principal electrodes is varied and is capable only 01' abrupt transition from its en- 10 ergized condition to its deenergized condition when the potential impressed between its princip'ai electrodes is reduced to a predetermined value, means for impressing, between said principal electrodes a potential that periodically falls below the predetermined value at which said device becomes deenergized immediately after being energized, thereby to periodically produce a tendency to deenergize said electric discharge device after its energi'zation and to render it periodically responsive to the electrical condition of said control electrode, an electrical con- 1 duction path including a'gap directly coupled be-' tween said control electrode and one 01 said principal electrodes whereby the potential diiierence 7 existing between said control electrode and said .one principal electrode is impressed across said gap, and means for producing combustion in the region of said gap whereby id gap is ionized byv the products of said .combustion, thereby substantialiy at the same instant to reduce the potential across said gap and to energize said device when it is in deenergized condition.

newer 13. Known-as.

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