US2489794A - Safety control and ignition apparatus for fuel burners - Google Patents

Description

Nov. 29, 1949 c. MAIN SAFETY CONTROL AND IGNITION APPARATUS FOR FUEL BURNERS Filed April 15,- 1948 IN V EN TOR. Robert v 0. Main BY Hi6 ATTORNEY Plasma Nov. 29, 1949 1 SAFETY CONTROL AND IGNITION APPARA- TUS FOR FUEL BURNERS Robert C. Main, La Canada, Calif., assig'nor to Robertshaw-Fulton Controls Company, Youngwood, Pa., a corporation of Delaware Application April 15, 1948, Serial N 0. 21,254

8 Claims. 1 V

This invention relates to control systems for fuel burners and more particularly to electrically operated systems for gas burning appliances.

Systems of the character indicated may utilize a constant burning pilot burner which serves to light the main burner upon a call for heat and also to maintain a thermoelectric automatic pilot control in operation. Since the main burner fuel is under control of an electromagnetic valve and electric ignition means is employed, it is obvious that a source of electric energy is required for the operation of the system. Various means have beenemployed to utilize such source of energy for resetting the automatic pilot when required in order to avoid a manual operation.

However, once the resetting operation is accomplished, the source of energy is no longer required in connection with the automatic pilot control as the thermoelectric energy is suflicient for such purpose.

An object of this invention is to utilize the same source of energy for ignition, condition control and resetting purposes in a simple and economical manner.

Another object of the invention is to include an automatic time delay during the resetting operation suflicient to insure reliable ignition of the pilot burner.

Another object of the invention is to render the system either recycling or non-recycling with a minimum of structural alteration.

Another object of theinvention is to demergize the igniter and discontinue the resetting action automatically upon the expiration of a predetermined starting period following initial turning on of the system.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing which is a schematic view of a control and ignition system for gaseous fuel burners embodying the invention.

Referring more particularly to the drawing, a main burner II is supplied with fuel by a main fuel pipe l2 in which a main fuel shutoff cock i4 is provided. The flow of fuel in the pipe I2 is also under the control of an electrically operable device such as an electromagnetic or solenoid valve I 6 having an operating coil l8 and being biased to closed position. A pilot' burner 20 receives a supply of fuel from the main fuel pipe l2 by way of a conduit 22 which is connected thereto intermediate the shutofi cock l4 and the solenoid valve l 6.

The solenoid valve l6 has its coil it under control of an electromagnetic device designated generally by the reference numeral 24. This device comprises a horseshoe magnet 26 having an armature 28 movable between attracted and released positions relative to the pole faces thereof. The usual winding 30 is associated with the horseshoe magnet 26 and is adapted when sufficiently energized to retain the armature 28 in its attracted position. The armature 2B is provided with a stem 32 depending therefrom and being reciprocable relative to the magnet 26 for moving the armature 2! to released position under bias of a coil spring 34. The electromagnetic device 24 is conveniently contained in a housing 36 through which the stem 32 projects and the coil spring 34 is operative between the underside of the housing 36 and a head 38 formed on the projecting end of the stem 32.

A contact bar 40 is secured to the head 38 and is therefore reciprocable with the armature 28 relative to the magnet 26. The contact bar 40 is spaced from the underside of the housing 36 and carries two contacts 42, 44 disposed one at either end thereof. The movable contacts 42, 44

-' are adapted to engage two relatively fixed contacts 46, 48 respectively when the armature 28 is in its attracted position. The fixed contacts 46, 48 are mounted on insulation on the underside of the housing 36 for the purpose described. It will be apparent that the contacts 42, 46, and 44, 48 comprise two contact pairs which are biased to open position by the coil spring 34.

The winding 30 of the magnet 26 is connected to thermoelectric means in the form of a thermocouple 50 which is exposed to the heat of a flame at the pilot burner 20. It will be understood that the winding does not receive sumcient energy from the thermocouple 56 to attract the armature 28 into engagement with the pole faces of the magnet 26. However, after the armature 28 has been thus positioned by a resetting means. the thermocouple 66 is capable of generating sufficient energy to retain it in such attracted position.

Means for automatically resetting the armature 26 in its attracted position are provided and comprise temperature responsive means in the form of a heat motor 52 shown as an expansible bellows. The entire resetting means is contained within a lower housing 68 which depends from the upper housing 24. Preferably, the bellows 52 contains a suitable expansive fluid including a partial charge of cymene and no movement of the bellows is adapted to occur below a temperature of 350 F. The bellows 52 is provided with a central depression 84 on its underside within which a support post 58 projects from the bottom of the housing 88. An electric heater or coil 88 is mounted on the post 58 within the depression 54 for causing expansion and contraction oi. the bellows 52 when heated and unheated respectively. A coil spring 62 is operative between the upper surface of the bellows 52 and an annular flange 64 on the housing 88 and serves to bias the bellows 52 to its contracted position.

Movement of the bellows 52 is transmitted to the contact bar 40 and thus to the armature 28 for resetting purposes by the provision of suitable motion transmittin means which includes an override mechanism for preventing damage to the bellows 52 in the event that further expansion thereof occurs after the armature 28 is in its attracted position.

Such motion transmitting means is positioned in the lower housing 58 intermediate the contact bar 40 and the bellows 52 and takes a form of a cup-shaped member 66 seated upon the bellows 52 and having its open end projecting through the flange 64. The inner rim portion of the cup-shaped member 66 is threaded for the reception of an inverted cup-shaped closure member 68 within which a slidable plug member I0 is mounted. The plug member 10 projects through an axial aperture II in the closure member 68 into engagement with the head 38 of the connecting stem 32 but such projection is limited by engagement of a shoulder 12 formed on the plug member I0 with the apertured surface of the closure member 68. A coil spring I4 is housed partly within an axial recess I3 formed in the underside of the plu member I0 and is operative between this member and the bottom of the cup-shaped member 66. The arrangement provides the override mechanism previously mentioned inasmuch as excess expansion of the bellows 52 will serve to compress the coil spring 62 and cause joint axial movement of the cup-shaped member 66 and the closure member 68 relative to the plug member 70.

The electric heater coil 60 is controlled by switching means in the form of a relay I6 having a coil I8 and an armature 80 which is normally biased to a released position. The armature 88 is engageable with a. pair of spaced contact means,82 and 84 in its released and attracted positions, respectively, for establishing circuits which will be described hereinafter.

Electric igniting means in the form of a resistance coil 86 is provided adjacent the pilot burner 20 for automatically igniting this burner. The solenoid valve It in this embodiment is adapted to be operated in response to variations in a temperature condition such as that prevailing in a space to be heated by operation of the main burner I0. To this end, thermostatic switching means in the form of a conventional room thermostat 86 having its contacts 88 and 98 in circuit with the coil I8 is provided, as will be more clearly apparent hereinafter. The usual stepdown transformer 92 and a double pole main switch 94 are provided in conjunction with the electrical portion of the system, it being noted that the main switch 84 may be arranged for operation upon manual rotation of the main fuel cock I4.

In the starting operation of the device, the manual opening the main fuel cock I4 simultaneouslycloses the main switch 94 to connect the primary of the transformer 92 to the line wires 96 and 91. Fuel is supplied to the pilot 4 burner 28 through the conduit 22 but the solenoid valve I6 which is biased to the closed position prevents fuel from beingsupplied to the ma n burner I0 by way of the main fuel pipe I2.

With the remaining parts of the system in the positions shown in the drawing a first circuit is established which may be traced from the upper terminal of the secondary of transformer 82, wire 88, wire I00, igniter 86, wire I02, heater coil 60, wire I04, contact 82, armature 80, and wire I06 to the lower terminal of the secondary of transformer 92. The igniter 86 being energized in this first circuit the fuel from the pilot burner 20 is ignited and the resulting flame serves to heat the thermocouple 50. As previously mentioned, th energy so supplied to the winding 30 of the magnet 26 is insuflicient to attract the armature 28 but the automatically resetting means now become employed for this P p Thus, when the bellows 52 becomes sufficiently heated by the heater coil 60, then the contact bar 40 is raised sufliciently to cause engagement of the contact pairs 42, 46 and 44, 48. Simultaneously, the armature 28 is seated against the pole faces of the magnet 26. As previously mentioned, this expansion of the bellows 52 does not occur until after a sufllcient time delay which permits the igniter 86 to produce a flame at the pilot burner 28 and the thermocouple to be sufflciently heated thereby to energize the winding 30 for holding urposes.

The closure of the contact pair 44, 48 serves to establish a second circuit which may be traced as follows: upper terminal of the secondary of transformer 98, contacts 88 and 90, thermostat arm 86, wire IIO, solenoid valve coil I8, wire II2, contact pair 48, 44, wire H4 and wire I06 to the lower terminal of the secondary of transformer 92. This second circuit serves to energize the coil I8 sufiiciently to open the solenoid valve I6 and permit fuel to flow to the main burner I0 where it is ignited by the flame at the pilot burner 20. It will be observed that this second circuit is under control of the thermostat 86 and will be opened and closed responsive to the temperature conditions sensed thereby, it being assumed that in this starting period the thermostat contacts 88, 90 are closed.

The closure of the contact pair 42, 46 serves to establish a third circuit which may be traced as follows: upper terminal of the secondary of transformer 92, wire 98, wire I00, wire H6, relay coil 18, wire H8, contact pair 46, 42, contact bar 40, wire H4, and wire I 06 to the lower terminal of the secondary of transformer 82. The completion of this third circuit serves to energize the relay coil 78 and attract the armature 80 from its released position in engagement with the contact 82. In the disclosed embodiment, the armature 80 thereupon engages with contact 84 and thereby establishes a holding circuit for the relay coil 18. Moreover, the disengagement of the armature 80 from the contact 82 serves to open the first circuit and deenergize the heater coil 60 and the igniter 86.

ture 28 is retained in its attracted position, the

holding circuit is not required inasmuch as the third circuit through contact pair 48, 42 is still effective. Hence, during normal running conditions at the main burner [8, the contact pairs 42, 48 and 44, 48 remain engaged while the coil [8 may become deenergized and reenergized by operation of the thermostat contacts 88, 98 to control the flow of fuel to the main burner l8 during the normal running conditions of the burner.

In the event that the flame from th pilot burner is extinguished then the thermocouple 50 cools so as to deenergize the winding and cause release of the armature 28 from the magnet 26. The contact pairs 42, 46 and 44; 48 are then opened by movement of the stem 32 under bias of the spring 34. Thus. the second and third circuits described are simultaneously opened and the solenoid valve It moves to a closed position to shut off the flow of fuel to the main burner l0 regardless of the closed position of the thermostat contacts 88, 90. However, due to the provision of the holding circuit for the relay coil 18, the armature 80 is retained in its attracted position and the first circuit is not re-established by operation of the contact pair 42, 46 to open position. In order to again place the system in operation the electrical system must be completely deenergised either by operation of the main switch 94 or by the provision of actuating means (not shown) to force the armature 80 away from engagement with the contact 84. Thus. u on engagement of the armature 88 with the contact 82, the system is again in condition for another sequence of operations to place it in normal running condition as previously described.

It will be apparent that where a recycling sys-- tem is desired the contact 84 could be dispensed with and the armature 80 caused to assume its released position in engagement with contact 82 whenever coil 18 is deenergized by operation of the contact pair 42, 46 to open position. Consequently the provision of the contact 84 and establishment of a holding circuit for the relay coil 18 is not considered essential in this invention as a non-recycling system is described merely as a preferred embodiment. These and many changes may be made in the details and construction and arran ement of parts within the scope of the appended claims and the invention is not limited to the precise embodiment shown and described herein.

I claim:

1. A control system for fuel burners having main and pilot burners and a source of electric energy, the combination of electri ally operable means connected to the source and being movable between positions for controlling the supply of fuel to the main burner, an electromagnetic device having an armature carrying contacts operable between positions for controlling the energization of said electrically operable means, means for biasing sa d armature for establishing one controlling position of said contacts, means responsive to a flame at the pilot burner for controlling the energization of said device but insufiiciently to overcome said biasing means, means responsive to variations in a temperature condition for movement to a position for resetting said armature and causing operation of said contacts to another controlling position thereof, and electric heating means connected to the source and located in proximity of said thermally responsive means for varying said temperature condition.

2. A control system for fuel burners having main and pilot burners and a source of electric energy, the combination of electrically operable means connected to the source and being movable between positions for controlling the supply of fuel to the main burner, an electromagnetic device having an armature carrying contacts operable between open and closed positions for controlling the energization of said electrically operable means, means for biasing said armature for establishing the open position of said contacts, thermoelectric means responsive to the heat of a flame at the pilot burner for controlling the energization of said device but being incapable of overcoming said biasing means and causing operation of said contacts to said closed position, means responsive to variations in a temperature condition for movement to a position for resetting said armature and causing closure of said contacts, electric heating means connected to the source and located in proximity of said thermally responsive means for varying said temperature condition, and switching means responsive to closure of said contacts for deenergizing said electric heating means.

3. A control system for fuel burners having main and pilot burners and a source of elec ric energy, comprising in combination, an electromagnetic device having an armature carrying two contact pairs biased to an open position when said armature is in released position, an electric igniter for thepilot burner, thermoelectric means responsive to the heat of a flame at the pilot burner for energizing said device sufliciently to hold said armature in attracted position and said contact pairs in closed position but being incapable of overcoming said bias and causing operation thereof from said released position and said open position respectively, means responsive to variations in a temperature condition for movement to a position for resetting said armature in said attracted position and causing movement of said contact pairs to closed position, electric heating means located in proximityof said thermally responsive means for varying said temperature condition sufliciently to cause said resetting operation, initially closed switching means for controlling a first circuit including the source, said igniter and said heating means, electrically operable means movable between fuel flow permiting and preventing 'positions for controlling the supply of fuel to the main burner, a second circuit including the source, said electrically operable means and one of said contact pairs, and means responsive to closure of the other said contact pair for causing operation of said switching means to open position.

4. A control system for fuel burners having main and pilot burners and a source of electric .energy, comprising in combination, an electromagnetic device having an armature carrying two contact pairs biased to an open position when said armature is in released position, an elec ric igniter for the pilot burner, thermoelectric means responsive to the heat of a flame at the pilot burner for energizing said device sufliciently to hold said armature in attrac ed position and said contact pairs in closed position but being incapable of causing operation thereof from said released position and said open position respectively, electric heating means located in proximity of said thermally responsive means for varying said temperature condition sufliciently to cause said resetting operation, a relay having a coil and a relatively movable armature biased to a released position, contact means engageable by said relatively movable armature in said released position thereof, a first circuit including the source, said igniter and said heating means and closed by said relatively movable armature engaging said contact means, electrically operable means movable between fuel flow permitting and preventing positions for controlling the supply of fuel to the main burner, a second circuit including the source, said electrically operable means and one of said contact pairs, and a third circuit including said relay coil and the other of said contact pairs for causing operation of said relatively movable armature to open said first circuit.

5. A control system for fuel burners having main and pilot burners and a source of electric energy, comprising in combination an electromagnetic device having an armature carrying two contact pairs biased to an open position when said armature is in released position, an electric igniter for the pilot burner, thermoelectric means responsive to the heat of a flame at the pilot burner for energizing said device sufliciently to hold said armature in attracted position and said contact pairs in closed position but being incapable of causing operation thereof from said released position and said open position respectively, electric heating means located in proximity of said thermally responsive means for arying said temperature condition sufficiently to cause said resetting operation, a relay having a coil and a relatively movable armature biased to a released position, spaced contact means engageable by said relatively movable armature respectively in said released and attracted positions thereof, a first circuit including the source, said igniter'and said heating means and closed by said armature in said relatively movable released position thereof, electrically operable means movable between fuel flow permitting and preventing positions for controlling the supply of fuel to the main burner, a second circuit in- 8 1 cluding the source, said electrically operable means and one of said contact pairs, a third cir; cult including said relay coil and the other of said contact pairs for causing operation of said relatively movable armature to open said first circuit, and a holding circuit for said coil established by said relatively movable armature in said attracted position thereof for preventing establishment of said first circuit when said other contact pair returns to an open position.

6. A system as claimed in claim 5 wherein the second circuit includes the thermostatic switching means for controlling the energization of said electrically operable means in response to variations in a temperature condition.

7. A control system for fuel burners having main and pilotburners and a source of electric energy, the combination of electrically operable means connected to the source and being movable between positions for controlling the supply of fuel to the main burner, an electromagnetic device having an armature carrying contacts operable between positions for controlling the energization of said electrically operable means and biased to one controlling position, means responsive to a flame at the pilot burner for controlling the energization of said device but insufficiently to overcome said bias, a heat motor movable between positions for resetting said armature and causing operation of said contacts to another controlling position thereof, an electric heater for said motor efiective when energized to cause said movement of said motor, and switching means operable upon said motor movement for deenergizing said heater.

8. A control system as claimed in claim 7 wherein said heat motor comprises a fluid operated bellows adapted for expansive movement only when said fluid becomes heated above 350 F.

ROBERT C. MAIN. No References Cited

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