US3111161A

US3111161A - Safety system for gas burners

Info

Publication number: US3111161A
Application number: US788005A
Authority: US
Inventors: Frege Johannes; Sachse Kurt
Original assignee: W Krefft AG
Current assignee: W Krefft AG
Priority date: 1959-01-20
Filing date: 1959-01-20
Publication date: 1963-11-19
Anticipated expiration: 1980-11-19

Description

Nov. 19, 1963 J. FREGE ETAL 3,111,161

SAFETY SYSTEM FOR GAS BURNERS Filed Jan. 20, 1959 2 Sheets-Sheet 1 magnetic push resistance peroiure negufive tern oefficient Wm M Z i]: BY MMW W5,

Nov. 19, 1963 J. FREGE ETAL 3,111,161

SAFETY SYSTEM FOR GAS BURNERS Filed Jan. 20, 1959 2 Sheets-Sheet 2 magnetic push mm ham KW Fig.|a

United States Patent 3,111,161 SAFETY SYSTEM FOR GAS BURNERS Johannes Frege, Hasslinghausen Usher, and Kurt Saehse,

Gevelsherg, Westphalia, Germany, assignors to W.

Kreift Alrtiengesellsehaft, Gevelsherg, Westphalia, Germany Filed .llau. 2t), 1%), Ser. No. lililfidl 6 Claims. (Cl. 15-125) This invention relates to safety systems for gas burners, and lends itself to gas heating systems of any kind, particularly gas ranges.

It is a general object of this invention to improve prior art safety systems for gas ranges.

This invention is concerned with gas heating systems which are free from the dangers normally resulting from a temporary reduction of gas pressure, or a temporary interruption of the supply of gas, and the object of the present invention is to achieve this end with simpler and more effective means than in prior art gas ranges.

When a pilot burner fails to ignite a main burner, and gas is allowed to escape under such conditions through the main burner, the gas forms a highly explosive and generally toxic mixture with ambient air. Such mixtures tend to endanger life due to the toxicity thereof, and may cause great damage when accidentally ignited.

It is another object of this invention to provide gas heating systems having semi-automatic controls positively precluding the unintentional escape of gas from non-ignited gas burners, and thus precluding formation of dangerously toxic and/or explosive mixtures of gas and air.

Still another object of the invention is to provide gas heating systems wherein the main burner is provided with a pilot burner for igniting the main burner and with means responsive to the radiation emitted from the pilot burner which means, in turn, control interlocks adapted to assure safe operation of the heating system.

Still anoth r object of the invention is to provide means for accelerating certain changeover switching operations which are necessary to achieve the aforementioned ends.

Further objects and advantages of the invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to, and forming part of, this specification.

For a better understanding of the invention reference may be had to the accompanying drawings wherein FIG. 1 is a dia' rammatic representation of a gas range embodying the invention;

FIG. la is a diagrammatic representation of a modified version of the range shown in FIG. 1.

Referring now to FIG. 1, numeral 2 has been applied to generally indicate a transformed having three secondary windings 2', 2", 2 The primary circuit, or supply circuit, of transformer 2 includes fuse 1 and switching device it. Winding 2' feed by means of leads 1%, lit? the filament 3 of thyratron 3. Winding 2' is connected to a rectifier 5 made up of two rectifier cells. The DC. output circuit of rectifier 5 energizes

solenoid valves

12, 14 and when the winding of relay or change-over relay 6' is energized. Relay 6' comprises a pair of

movable contacts

6a, 6b. Contact 6a is adapted to cooperate with a pair of fixed contacts 6a of which the right contact is a blind contact i.e. a contact not connected to any circuit terminal. Contact 6]) is adapted to cooperate with a pair of fixed contacts 612 of which the left is a blind contact. When the winding of relay 6 is energized the two

contacts

6a, 6b controlled by relay 6' are in the right position thereof and the load circuit of rectifier 5 runs as follows: Center tap ltlti between the two rectifier cells 5; movable contact 611; right fixed contact 627'; lead a, relay 17 and solenoid valves 12, idand 15 in parallel; lead [1; and center tap of trans former Winding 2". When relay 6' is not energized the

movable contacts

6a, 6b controlled by relay 6 are in the left position thereof and then transformer winding 2" applies an A.-C. voltage to three serially connected igniters '7 of the incandescent type of which each is associated with one of three pilot burners '7. The circuit of igniters 7 when closed runs as follows: Upper terminal of winding 2; lead c; movable contact 6a; left fixed contact 6a; all three igniters 7 in series; lead d; lower end of secondary winding 2". The three pilot burners '7' are supplied with gas by line T branching oif manifold M to which cooking burners or main burners B are connected by the intermediary of

solenoid valves

12, 14, 15. Transformer winding 2" is connected to a rectifier bridge circuit 4 whose D.-C. output circuit includes leads 111 and 1?.2 and two resistors 9, it forming a potentiometer. Resistors 9, Jill are shunted by a capacitor 22 for decreasing ripples in the output of rectifier 5. The grid bias of tube 3 is taken from potentiometer 9, 1h. The grid circuit of tube 3 includes serially connected resistors 8 having a negative temperature coefficient of resistance and also includes resistors 19, Ztl and 21. Each of resistors is arranged immediately adjacent one of pilot burners 7 and exposed to the heat radiated therefrom. Resistors 8 are connected by lead 2 to the point of potentiometer 9, it) between

resistors

9 and 10 and resistors i9, 20 and 21 are connected by lead 1 to the negative terminal of potentiometer 9, 16. Resistors l9 and it are adjustable making it possible to negatively bias the control grid 3" of thyratron 3, thus precluding any flow of plate current. Resistor 23 arranged immediately adjacent to the control grid 3" of thyratron 3 is a grid limiting resistor provided for grid protection. Grid 3" of thyratron 3 is conductively connected to the cathode 3 thereof. Manifold M comprises a manually operable cock R for admitting gas to cooking or main burners B and pilot burners '7'. This cool: which is arranged at a point upstream from the point where line T branches off manifold M is mechanically coupled with switch it in the primary circuit of transformer 2 in such a way that when gas is being admitted to pilot burners 7' by opening that valve, the primary or energizing circuit of transformer Z is being closed simultaneously by closing switch 1. As a result of energizing transformer 2 igniters 7 become immediately incandescent and ignite the combustible gas escaping at the pilot burners 7. The heat generated at pilot burners '7 is transferred to resistors 8, as the result of which their resistance instantly decreases. This, in turn, reduces the negative grid bias of tube 3, causing the flow of a current in the plate circuit. This circuit incl .des plate or anode 3", lead g and resistor it in addition to the aforementioned relay 6 and leads 103 and 1532. The latter and lead the are connected to the terminals of transformer winding 2". Resistor l8 shunts relay 5 when contact 17 under the control of relay 17 is in the left position thereof. The shunt across relay 6' includes lead [2, movable contact 17', resistor 18 and lead 1'.

The operation or" the arrangement of FIG. 1 is as follows:

Because of the mechanical coupling of the aforementioned cock R for admitting gas to manifold M and line T with switch 1, transformer 2 is always energized concornitant with admission of gas to the system. Upon admittance of gas to the system the gas escaping from pilot burners 7' is ignited by igniters 7. The heat radiated from pilot burners 7 results in a decrease of the resistance of resistors 8 directly included in the circuit of control grid 3 of tube 3. This swings the bias of grid 3" from negative to positive and initiates the flow in FIG. 1 to their rig .t position.

of plate current. The latter energizes relay 6', causing its two change-over contacts 6a, as to shift from their left position to their right position. This causes opening of the circuit of igniters 7 and closing of the circuit of solenoid valves l2, l4, l5 and opening of the latter and energizing of relay 17. The gas escaping at main burners B upon opening of solenoid valves 12, l4, is ignited by pilot burners 7. Energization of relay 17 causes movement of contact 17' from its right position to its left position, thus shunting resistor l3 across relay 6.

Relay 6', i.e. the operating winding thereof, is energized by the maximum plate current which thyratron 3 is capable of supplying, and thus contacts 6a, 6b are rapidly moved against their bias from their left position shown A smaller magnetic action is required to maintain

contacts

6a, 6b in their right position than to rapidly move the same to their right position. Hence relay winding 6' may be de-energized to some extent after

contacts

6a, 6b have completed their travel to their right position. This accelerates their movement to their left position as a result of a renewal of a cut-off of thyratron 3 and cessation of the flow of its plate current.

The flames at burners B may be turned off in different ways. All burners B may be turned off by closing the aforementioned cock R in manifold M, simultaneously de-energizing transformer 2. Then the entire system, including all its electrical components, is inoperative. As long as pilot burners 7 burn, the flame on any burner B will be re-ignited when the respective burner is being resupplied with gas. As soon as one or more of pilot burners 7' are extinguished, the temperature of one or more resistors 8 decreases and, therefore, the bias of control grid 3" tends to become negative, to interrupt the flow of plate current and deenergize relay 6, causing both

contacts

6a, 6b to move from their right positions to their left positions illustrated in P16. 1. This causes interruption of the circuits of solenoid valves 1.2, 14-, 15 and closing of these valves, and it also causes closing of the circuit of igniters 7 and the igniters to become incandescent. Shunting of relay d by contact 17 and resistor it; accelerates the changeover operation of relay 6' when the bias of grid 3" swings from positive to negative since it diverts a portion of the plate current of tube 3 from relay 6.

The arrangement of parts of FIG. la is substantially the same as that shown in FIG. 1 and the same reference characters have been applied in FIGS. 1 and in to indicate like parts. Hence the arrangement of FIG. 1a calls only for an additional description inasmuch as it deviates from that shown in FIG. 1.

FIG. la illustrates another shunt arrangement causing a portion of the plate current of tube 3 to by-pass relay 6'. The arrangement shown in FIG. 1a may, if desired, take the place of parts l7, 17', 18 of FIG. 1. According to FIG. la relay 6' is shunted by two variable resistors l8, 18'. The latter has a high negative temperature coefficient of resistance. The plate current of tube 3 flows in parallel paths through relay 6 and resistors 13 and 1S". Resistor 18" is heated by z' -r losses as a result of the how of current through it, causing its resistance to decrease and to carry a progressively increasing portion of the total plate current of tube 3. In other words, relay 6' is being progressively deenergized by resistor 18", thus accelerating the change-over of

contacts

6a, 6b from their right positions to their left positions on cooling of resistors 8.

Interruption of the gas service causes simultaneous extinction oi the main burners B and of the pilot burners 7'. Therefore resistors 3 cool down, their resistance increases, the bias of grid 3" swings from positive to negative and interrupts the flow of plate current through discharge tube 3. This deeuergizes relay 6' causing contacts 6a, db to move from right to left and to close the circuit of igdniters '7. Therefore pilot burners 7' will be ignited whenever service is restored and gas escapes at the nozzle of pilot burners 7 N T he same sequence of steps occurs whenever one of the main burners should be extinguished by a draft. It is possible to manufacture resistors having a negative temserature coefficient of resistance and changing their resistance drastically at the occurrence of relatively small changes in temperature in sub-miniature size.

It will be observed that the circuitry of FIGS. 1 and.

la involves three separate and distinct stages: (1) The grid circuit of thyratron 3 including sensing resistors 8', (2) the energizing circuit of relay 6 which is identical with the plate circuit of thyratron 3; and (3) the circuits of solenoid valves l2, l4, l5 and electric igniters 7. As nienttioned, these three stages are separate and in the above sequence each of the three stages is adapted to carry increasingly larger currents and each stage involves an increasingly larger power.

The combinaiton of a temperature sensing element in the form of a resistor having a negative temperature coellicient of resistance with a thyratron yields an extremely critical or sensitive on-olf characteristic which could neither be achieved by combining a temperature sensing element in the form of a resistor having a positive temperature coefiicient of resistance with a thyratron or by combining a temperature-sensing element in the form of a resistor having a negative coefficient of resistance with a grid-controlled high vacuum electron tube.

Since the thyratron 3 carries either its full plate current or no plate current at all, relay 6' will either be fully energized, or de-energized, depending upon the condition the thyratron 3 is in. In other words, the operation of

contacts

6a, 6b of relay 6 is positive and is not affected by mechanical properties such as inaccuracies of relay 6'.

The coaction between temperature sensing elements in form of resistors 8 having a negative temperature coer cient of resistance with a thyratron is a pre-requisite for providing a series arrangement of such sensing resistors 8 of which each is associated with a pilot burner 7' and each controls the operation of relay 6' and that of its movable contacts 6a, db. A change in the resistance of each of resistors 8 is but a relatively small change in the aggregate resistance of all resistors 25, and if the change of the resistance of one single resistor 53 due to a relatively small change in temperature would not sufilce to swing the bias of thyratron 3 so as to fully open or fully close the same, the above series connection of all sensing resistors 8 would be impossible.

It will also be understood that we have illustrated and described herein two preferred embodiments of our invention and tnat various alterations may be made in the details thereof without departing from the spirit and scope of our invention as defined in the appended claims.

We claim:

1. A gas distribution system comprising in combination:

(a) a manifold;

(b) a main gas burner supplied with gas from said manifold;

(c) an electromagnetic valve having a de-energized closed position and an energized open position admitting gas from said manifold to said main burner;

(d) a pilot burner supplied with gas from said manifold and operatively related to said main burner;

(e) an electric igniter operatively related to said pilot burner;

(f) an electromagnetic change-over relay for controlling said valve and said igniter and including an operating winding, said relay having a first position upon de-energization of said operating winding adapted to cause de-energization of said valve and energization of said igniter and said relay having a second position upon energization of said operating #3 winding adapted to cause energization of said valve and de-energization of said igniter;

(g) a thyratron having a plate circuit including said operating winding and a grid circuit including a control grid;

(h) means for biasin said grid sufificiently negatively to inhibit the flow of current in said plate circuit as long as the resistance in said grid circuit exceeds a predetermined value;

(i) a temperature sensing resistor having a negative temperature coefiicient of resistance exposed to heat radiation emitted from said pilot burner arranged in said grid circuit; and

(j) means for accelerating the switching operation of said relay from said second position thereof to said first position thereof, said accelerating means including normally ineffective shunt means across said operating winding of said relay adapted to become effective only upon completion of the movement of said relay from said first position thereof to said second position thereof.

2. A gas distribution system comprising in combination:

(a) a manifold;

(b) a main gas burner supplied with gas from said manifold;

(e) an electric igniter operatively related to said pilot burner;

(1) an electromagnetic change-over relay for controlling said valve and said igniter and including an operating winding, said relay having a first position upon de-energization of said operating winding adapted to cause de-energization of said valve and energization of said igniter and said relay having a second position upon energization of said operating winding adapted to cause energization of said valve and de-energization of said igniter;

(12) means for biasing said grid sufiiciently negatively to inhibit the flow of current in said plate circuit as long as the resistance in said grid circuit exceeds a predetermined value;

(7) means for accelerating the switching operation of said relay from said second position thereof to said first position thereof, said accelerating means including an additional electromagnetic relay adapted to be energized in response to completion of the movement of said first mentioned relay from said first position thereof to said second position thereof; and

(k) said accelerating means further including means for shunting said operating winding in response to energization of said additional relay.

3. A gas distribution system comprising in combination:

(a) a manifold;

(b) a main gas burner supplied with gas from said manifold;

(c) an electromagnetic valve having a de-energized closed position and an energized open position admitting gas from said manifold to said burner;

(e) an electric igniter operatively related to said pilot burner;

(1) an electromagnetic change-over relay for controlling said valve and said igniter and including an op erating winding, said relay having a first position upon de-energization of said operating winding adapted to cause de-cnergization of said valve and energization of said igniter and said relay having a second position upon energization of said operating winding adapted to cause energization of said valve and de-energizaiton of said igniter;

(11) means for biasing said grid sufficiently negatively to inhibit the flow of current in said plate circuit as long as the resistance in said grid circuit exceeds a predetermined value;

(i) a temperature sensing resistor having a negative temperature coefficient of resistance exposed to heat radiation emitted from said pilot burner arranged in said grid circuit; and

(1') means for accelerating the switching operation of said relay from said second position thereof to said first position thereof, said accelerating means including means establishing a shunt across said operating Winding of said relay, said shunt-establishing means including a resistor having a negative temperature coefiicient of resistance.

4. A gas distribution system comprising in combination:

(a) amanifold;

(b) a plurality of main gas burners connected in parallel and supplied with gas from said manifold;

(c) a plurality of electromagnetically operated valves each arranged between said manifold and one of said plurality of main burners and each having a closed position and an open position admitting gas from said manifold to said one of said plurality of main burners;

(d) a plurality of pilot burners supplied with gas from said manifold each operatively related to one of said plurality of main burners;

(e) a plurality of electric igniters serially connected into an igniter circuit and each operatively related to one of said plurality of pilot burners;

(f) an electromagnetic change-over relay for controlling said plurality of valves and said plurality of igniters and including an operating winding, said relay having a first position upon de-energization of said operating winding adapted to cause closing of said plurality of valves and energization of said plurality of igniters and said relay havin a second position upon energization of said operating winding adapted to cause opening of said plurality of valves and deenergization of said plurality of igniters;

(g) a thyratron having a plate circuit including said operating Winding and having a grid circuit including a control grid;

(h) means for sufficiently negatively biasing said control grid to inhibit the flow of current. in said plate circuit as long as the resistance of said grid circuit exceeds a predetermined value.

(1') a plurality of temperature sensing resistors having a negative temperature coefiicient of resistance serially connected in said grid circuit each exposed to heat radiation emitted from one of said plurality of pilot burners and each adapted to inhibit the flow of current in said plate circuit and energization of said operating winding upon extinction of but one of said plurality of pilot burners and concomitant increase of said resistance of said grid circuit; and

(j) means for accelerating the switching operation of said relay from said second position thereof to said first position thereof, said accelerating means int eluding means responsive to the flow of current in said plate circuit for establishing a shunt across said operating winding of said relay upon movement of said relay from said first position thereof to said second position thereof. 5. A gas distribution system comprising in combination:

(a) amanifold;

(b) a plurality of main gas burners connected in parallel and jointly supplied with gas from said manifold;

(d) a plurality of pilot burners jointly supplied with gas from said manifold each operatively related to one of said plurality of main burners;

(1) an electromagnetic change-over relay for controlling said plurality of valves and said plurality of igniters and including an operating winding, said relay having a first position upon de-energization of said operating winding adapted to cause closing of said plurality of valves and energization of said plurality of igniters and said relay having a second position upon energization of said operating winding adapted to cause opening of said plurality of valves and deenergization of said plurality of igniters;

(h) means for biasing said control grid sufiiciently negatively to inhibit the flow of current in said plate circuit as long as the resistance of said grid circuit exceeds a predetermined value;

(1') a plurality of temperature sensing resistors having a negative temperature coefiicient of resistance serially connected in said grid circuit each exposed to heat radiation emitted from one of said plurality of pilot burners and each adapted to inhibit a flow of current in said plate circuit and energization of said operat ing Winding upon extinction of but one of said plurality of pilot burners and concomitant increase of said resistance of said grid circuit; and

(j) means for accelerating the switching operation of said relay from said second position thereof to said first position thereof, said accelerating means including an additional electromagnetic relay adapted to be energized in response to completion of the movement of said first mentioned relay from said first position thereof to said second position thereof, said accelerating means further including means for shunting said operating winding of said relay in response to energization of said additional relay.

6. A gas distribution system comprising in combination:

(a) amanifold;

(b) a plurality of main gas burners connected in parallel and jointly supplied with gas from said manifold.

(f) an electromagnetic change-over relay for controlling said plurality of valves and said plurality of igniters and including an operating winding, said relay having a first position upon deenergization of said operating winding adapted to cause closing of said plurality of valves and energization of said plurality of igniters and said relay having a second position upon energization of said operating winding adapted to cause opening of said plurality of valves and de-energization of said plurality of igniters;

(It) means for biasing said control grid sufficiently negatively to inhibit the flow of current in said plate circuit as long as the resistance of said grid circuit exceeds a predetermined value;

(i) a plurality of temperature sensing resistors having a negative temperature coefficient of resistance serially connected in said grid circuit each exposed to heat radiation emitted from one of said plurality of pilot burners and each adapted to inhibit a flow of current in said plate circuit and energization of said operating winding upon extinction of but one of said plurality of pilot burners and concomitant increase of said resistance of said grid circuit; and

(j) means for accelerating the switching operation of said relay from said second position thereof to said first position thereof, said accelerating means including means establishing a shunt across said operating winding of said relay, said shunt-establishing-means including a resistor having a negative coeflicient of temperature.

References Cited in the file of this patent UNITED STATES PATENTS 1,858,265 Dahlstrorn May 17, 1932 2,212,352 Plein Aug. 20, 1940 2,327,690 Ackerman Aug. 24, 1943 2,411,642 Strobel Nov. 26, 1946 2,448,475 Strobel et a1. Aug. 31, 1948 2,479,797 Wasser Aug. 23, 1949 2,511,881 Snyder June 20, 1950 2,608,609 Fitch Aug. 26, 1952 2,614,621 Main Oct. 21, 1952 2,624,398 Thomson Jan. 6, 1953 2,839,132 Blackett et al. June 17, 1958 2,924,270 Deziel Feb. 9, 1960

Claims

1. A GAS DISTRIBUTION SYSTEM COMPRISING IN COMBINATION: (A) A MANIFOLD; (B) A MAIN GAS BURNER SUPPLIED WITH GAS FROM SAID MANIFOLD; (C) AN ELECTROMAGNETIC VALVE HAVING A DE-ENERGIZED CLOSED POSITION AND AN ENERGIZED OPEN POSITION ADMITTING GAS FROM SAID MANIFOLD TO SAID MAIN BURNER; (D) A PILOT BURNER SUPPLIED WITH GAS FROM SAID MANIFOLD AND OPERATIVELY RELATED TO SAID MAIN BURNER; (E) AN ELECTRIC IGNITER OPERATIVELY RELATED TO SAID PILOT BURNER; (F) AN ELECTROMAGNETIC CHANGE-OVER RELAY FOR CONTROLLING SAID VALVE AND SAID IGNITER AND INCLUDING AN OPERATING WINDING, SAID RELAY HAVING A FIRST POSITION UPON DE-ENERGIZATION OF SAID OPERATING WINDING ADAPTED TO CAUSE DE-ENERGIZATION OF SAID VALVE AND ENERGIZATION OF SAID IGNITER AND SAID RELAY HAVING A SECOND POSITION UPON ENERGIZATION OF SAID OPERATING WINDING ADAPTED TO CAUSE ENERGIZATION OF SAID VALVE AND DE-ENERGIZATION OF SAID IGNITER; (G) A THYRATRON HAVING A PLATE CIRCUIT INCLUDING SAID OPERATING WINDING AND A GRID CIRCUIT INCLUDING A CONTROL GRID; (H) MEANS FOR BIASING SAID GRID SUFFICIENTLY NEGATIVELY TO INHIBIT THE FLOW OF CURRENT IN SAID PLATE CIRCUIT AS LONG AS THE RESISTANCE IN SAID GRID CIRCUIT EXCEEDS A PREDETERMINED VALUE; (I) A TEMPERATURE SENSING RESISTOR HAVING A NEGATIVE TEMPERATURE COEFFICIENT OF RESISTANCE EXPOSED TO HEAT RADIATION EMITTED FROM SAID PILOT BURNER ARRANGED IN SAID GRID CIRCUIT; AND (J) MEANS FOR ACCELERATING THE SWITCHING OPERATION OF SAID RELAY FROM SAID SECOND POSITION THEREOF TO SAID FIRST POSITION THEREOF, SAID ACCELERATING MEANS INCLUDING NORMALLY INEFFECTIVE SHUNT MEANS ACROSS SAID OPERATING WINDING OF SAID RELAY ADAPTED TO BECOME EFFECTIVE ONLY UPON COMPLETION OF THE MOVEMENT OF SAID RELAY FROM SAID FIRST POSITION THEREOF TO SAID SECOND POSITION THEREOF.