US2711216A - Control system for fluid fuel burners - Google Patents

Description

June 21, 1955 T. T. ARDEN 2,711,216

CONTROL SYSTEM FOR FLUID FUEL BURNERS Filed June 5, 1951 2 Sheetsheet 1 's w a; w 7

1? Q E 3 4 8 1 Q T INVENTOR. :4 Thomas 774F020.

June 21, 1955 T. 'r. ARDEN 2,711,216

CONTROL SYSTEM FOR FLUID FUEL BURNERS Filed June 5. 1951 2 Sheets-Sheet 2 90 76 r 56 I1 4 =r56--= 92g; 122' r j r IN V EN TOR.

mamas 7741 0292.

' Ms AIFOHAZY CONTROL SYSTEM FGR FLUID FUEL BURNERS Thomas T. Arden, Newport Beach, Calif, assignor to RobertshaW-Fulton Controls Company, Greenshnrg, Pa., a corporation of Delaware Application June 5, 1951, Serial No. 230,015

9 Claims. ((1158-1249 This invention relates to control systems for fluid fuel burners and more particularly to automatic pilot controls therefor.

Automatic pilot control systems for fluid fuel burners may be arranged so that a thermocouple, which is responsive to the heat of a flame at a pilot burner, controls the energization of an electromagnetic device for shutting off the fuel supply to a main burner upon extinguishment of the pilot burner flame. In such devices the electric current generated by the thermoelectric device is usually insuflicient to attract the armature of the electromagnet, but is suflicient only to hold the armature in attracted position after it has been otherwise moved to such position. Manually operated devices have been employed for the purpose of resetting the armature in engagement with the electromagnet and it is a principal object of this invention to eliminate the necessity of a manual reset operation on an electromagnetic device through the utilization of automatically operated means. I

Another object of this invention is to continue operation of the automatically operated means for a period of suflicient length to establish a flow of thermoelectric current for controlling the electromagnetic control device.

Another object of this invention is to render the automatically operated means inoperative during the period that the electromagnetic control is effective to permit fuel flow to the main burner.

Another object of this invention is to prevent flow of fuel to the main burner during the resetting of the thermoelectric automatic pilot device.

Anothr object of this invention is to secure prompt recycling upon extinguishment of the flame at the pilot burner.

Another object of this invention is to effect automatic r operation of fuel burners at preselected intervals.

To accomplish the aforementioned objects, acontrol system for fluid fuel burners having main and pilot burners may comprise a solenoid valve for controlling fuel flow to the main burner, an electric igniter for the pilot burner, and a combined thermomagnetic device and relay for controlling the operation of the solenoid valve and igniter. In a preferred embodiment of the invention, the closing of a clock controlled switch causes energization of the relay to reset the armature of the thermornagnetic device and also causes energization of the igniter. A timer effects deenergization of the relay and igniter after a period long enough to insure ignition of the pilot. If the pilot burner is ignited, the armature of the thermomagnetic device is retained in its retracted position to permit the relay armature to actuate a double throw switch to energize the winding of the solenoid valve and deenergize the igniter timer. Failure of the pilot flame will cause release of the armature of the thermomagnetic device which moves into engagement with the relay armature and causes the same to actuate tates Patent the double throw switch thereby deenergizing the sole- 7 noid winding and energizing the igniter and the relay coil.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings wherein:

Fig. l is a schematic showing of control apparatus embodying this invention;

Fig. 2 is a schematic showing of a portion of the apparatus illustrated in Fig. 1 with the parts thereof in different operating positions; and

Fig. 3 is similar to Fig. 2 with the parts of the apparatus shown in still other operating positions.

Referring more particularly to the drawings, a main burner 10 is supplied with fuel through a main fuel pipe ll'and the flow of fuel therein is under the separate control of a manually operable valve 14, a thermostatically controlled valve 16 and an electrically operable valve 18. A pilot burner 20 is positioned adjacent the main burner 10 and is supplied with fuel by a conduit 22 in which the flow of fuel is controlled by the main valve 14 only.

The thermostatic valve 16 may be of any suitable type and is provided with a temperature sensing element here shown as a bulb 17 containing a thermal fluid and connected to a valve actuating device (not shown) by a capillary tube 19. The bulb 17 is subjected to the temperature of a medium heated by the main burner 10 and is adapted to close the valve 16 when such medium reaches a predetermined temperature ina manner well known in the art.

The electrically operable valve 18 may comprise a casing 24 provided with an internal partition 26 in which is formed a valve port 28. The valve port 28 is adapted to be opened or closed by a valve member 38 movable toward and away from the partition 26 in a manner well known in the art. The valve member 30 is biased toward the partition 26 by a suitable spring 32 and carries a valve stem 34 of suitable magnetic material which extends into the magnetic field of a solenoid coil 36.

The coil 36 is adapted, when energized, to move the valve stem 34 and its associated valve member 30 against the bias of the spring 32 to open the valve port 28 and permit flow of fuel through the casing 24. When the coil 36 is not energized, the spring 32 is effective to hold the valve member 30 in engagement with the partition 26 to close the port 28 and prevent flow of fuel through the casing 24.

To provide for the energization of the coil 36 of the valve 18, circuit means is provided for connecting the coil 36 to a source of electric energy here shown as a step-down transformer 38 having the primary thereof connected to line .wires L1, L2. The energizing circuit for the solenoid coil 36 includes a plurality of switches here shown as a clock operated switch 4i), a manually operable switch 42, and a switch 44 adapted to be responsive to a flame at the pilot burner 20.

The clock operated switch 40 may be of any suitable form and is here shown as comprising a fixed blade 46 juxtaposed to a flexible switch blade 48 which is engageable by a reciprocable operating member 50 arranged to be actuated by a clock mechanism 51. The clock mechanism 51 is effective to move the operating member 50 vertically as viewed in the drawings to flex the flexible switch arm 48 and move the same into and out of engagement with the fixed switch arm 46 at preselected intervals. It is to be understood that the clock mechanism 51 may be adjusted to maintain the operating member 50 in its lowest position to thereby hold the flexible switch arm 48 in engagement with the switch arm 46 at all times in a manner well known in the art.

The manually operable switch '42 may comprise a fixed contact 52 engageable by a movable switch arm 54 which is operatively connected by any suitable means to the manually operable valve 14. The connection between the valve 14 and the switch 42 is preferably such that the switch blade 54 is maintained out of engagement with the contact 52 when the valve 14 is closed and is moved into engagement with the contact 52 when the valve 14 is opened.

The pilot flame responsive switch 44 is here shown as a single pole double throw switch having a first pair of spaced contacts 56 and a second pair of spaced contacts 58. A contact bridge 69 is movable toward and away from the contacts 56 and is biased into engagement therewith by a suitable spring 62. Connected to the contact bridge 69 to be movable therewith is a second contact bridge 64 which is engageable with the contacts 58 to close a circuit therebetween. The contact bridges 6t), 64 are so spaced from each other that the bridge 64 is free of the contacts 53 whenthe bridge 69 is in engagement with the contacts 56 and the bridge 63 is free of the contacts 56 when the bridge 64 is in engagement with the contacts 53. The contacts 58 and contact bridge 64 of the switch 44 form a part of the aforementioned energiz ing circuit for the solenoid coil 36 while the contact bridge 60 and its contacts 56 perform a function which will more fully appear.

Actuating means for moving the contact bridges 6t 64 of the switch 44 against the bias of the spring 62 is here shown as a lever 66 pivotally engageable intermediate its ends by a knife edge fulcrum 68 which is rigidly mounted by any suitable means and is fixed relative to the contacts 56, 53 of the switch 44. One end of the lever 66 is provided with a bearing surface 79 which is operatively engageable with the contact bridge 64. Yieldable means, here shown as a spring 72, is connected to the other end of the lever 66 and to the support of the fulcrum 63 to urge the lever 66 into engagement with the fulcrum 68 and to bias the lever 66 in a clockwise direction as viewed in the drawings about the fulcrum 68 to move the bearing 79 into engagement with the contact bridge 64. The spring 72 is considerably stronger than the spring 62 of the switch 44 and is therefore effective to compress the spring 62 and hold the contact bridge 64 in engagement with the contacts 58.

However, to prevent energization of the solenoid coil 36 and thus prevent supply of fuel to the main burner 19 in the absence of a flame at the pilot burner 20, means responsive to a flame at the pilot burner is provided for preventing the lever 66 from contacting the bridge 64 of the switch 44 in the absence of a pilot flame. This means may take the form of an electromagnet having a horseshoe frame 74 provided with the usual winding 76 the ends 78, 80 of which are connected respectively to the hot and cold junctions of a thermocouple 82 positioned adjacent the pilot burner 20 to be subjected to the heat of a flame emanating therefrom. An armature element 84 of suitable magnetic material is movable between attracted and released positions relative to the magnet frame 74 and is biased to its released position by a spring 86 acting between the armature element 84 and the frame '74.

The electromagnetic device 74, 84 is positioned above the lever 66 so that a bearing surface 88 formed on the armature element 84 will engage the lever 66 in the released position of the armature element 84. The bearing 88 of the armature element 84 and the spring 72 engage the lever 66 on opposite sides of the fulcrum 68 so that the bias of the spring 86 exerted through the armature element 84 is opposed to the bias of the spring 72. The spring 86 is stronger than the spring 72 so that, in the released position of the armature 84, the bias of the spring 72 will be overcome and the bearing surface 70 on the lever 66 will be maintained out of engagement with the contact bridge 64 of the switch 44.

In electromagnetic devices utilizing a thermocouple as a source of electric power, the thermoelectric current generated by the thermocouple is usually insuflicient to move the armature to its attracted position but is sufficient to a horeshoe frame 99 with the usual winding 92. The

magnet frame 9% is preferably larger than the magnet frame '74 and is positioned over the frame 74 with the pole faces thereof disposed substantially lowerthan the.

pole faces of the magnet 7-4 so that the magnet 74 is nested within the magnet frame 94 The electromagnet 9t), 92 is adapted. when energized to move the lever 66 bodily away from the fulcrum 68 and into engagement with its pole faces. The lever 66 thus constitutes an armature for the magnet 90, 92.

Since the armature element 84 of the thermomagnetic device contacts, in its released position, the lever 66, movement of the lever 66 toward the pole faces of the electromagnet 99, 92 is effective to move the armature element 84 against the bias of the spring 86 and into engagement with the pole faces of the magnet 74, 76 as shown in Pig. 2. To insure seating of the armature element 84 on the pole faces of the magnet frame 74, the magnet frame 2 9i) is preferably so proportioned that there is clearance between one of the pole faces thereof and the lever 66 when the lever 66 is holding the armature element 84 in its attracted position.

To prevent energization of the solenoid coil 36 of the valve 18 during the resetting operation, the electromagnet 99, 92 is so positioned relative to the switch 44 that the lever 66 will not contact the bridge 64 of the switch 44 when the same is in its attracted position relative to the pole faces of the electromagnet 9t 92.

An igniter 94 of the electrical resistance type is disposed proximate the pilot burner 26 and is connected in series with the magnet coil 92 to be energized during the resetting operation. The coil 92 and igniter94 are connected to the secondary of the transformer 33 by circuit means which includes, in series connection, the clock operated switch 40, the manually operable switch 42, contacts 56 and contact bridge 66 of switch 44, and a time delay switch 96 effective to disconnect the coil 92 and igniter 94 from the transformer 38 upon the expiration of a predetermined period initiated upon connection of the coil 92 and igniter 94 to the transformer 38. e

The time delay switch 96 may be of any suitable form and is here shown as comprising a fixed contact 93 and a movable contact 1% carried on a deformable bimetal element 162. A heating coil 164 is wound on the bimetal element 102 with one end connected to one of the contacts 56 of the switch 44 and the other end connected to the movable contact 100.

In the operation of the apparatus, it may be assumed that the main valve 14 is closed, the transformer 38 is energized by the line wires L1, L2 leading from an alternating current source, and the various elements of the apparatus are in the positions shown in Fig. l of the draw ings. In this condition of the apparatus, it will be noted that the valve member 30 of the electrically operable valve 18 is biased closed, the valve 16 is open, the contacts 46, 43 of the clock operated switch 46 are open, the manually operable switch 42 is open, the contact bridges 6t), 64 of the switch 44 are positioned to connect only the contacts 56, and the contacts 98, 189 of the time delay switch 96 are closed.

, The system may be placed in operation by adjusting the clock mechanism 51 to depress the operating element 59 thereby moving the contact 43 into engagement with V Accordingly, reset means must be provided for opened to allow fuel to flow in the main fuel pipe 12 as far as the electrically operable valve 18 and in the conduit 22 to the pilot burner 26. Opening of the valve 14 is also effective to close the switch 42.

The reset coil 92, igniter 94, and heater coil 104 of the time delay switch 96 are now connected in series circuit with the secondary of the transformer 38. This series circuit may be traced as follows: from one terminal of the secondary of the transformer 36 to wire 106, contact 48 of switch 4!), contact 46 of switch 40, Wire 1198, switch blade 54 of switch 42, contact 52 of switch 42, wire 110, igniter 94, wire 112, coil 92, wire 114, one of the contacts 56 of the switch 44, contact bridge 66, the other of the contacts 56 of the switch 44, Wire 116, heater coil 104, movable contact 100 of the time delay switch 96, fixed contact 98, and wire 113 to the other terminal of the secondary of the transformer 38. Current now flows through the igniter 94 raising the temperature thereof suficiently to ignite gas flowing from the pilot burner 20 and current flowing through the coil 92 creates a magnetic field of sufficient strength to move the lever 66 to its attracted position as shown in Fig. 2.

Movement of the lever 66 to its attracted position will move the armature element 84 against the bias of the spring 86 and into engagement with the pole faces of the magnet 74, 76. The flame at the pilot burner 26 will heat the thermocouple 82 sufliciently to cause the same to energize the magnet winding 76 and hold the armature 84 in engagement with the pole faces of the magnet frame 74.

During this resetting operation, current is flowing through the heater coil 104, raising the temperature thereof and thus raising the temperature of the bimetal element 102. At the expiration of a predetermined period of sufficient length to insure ignition of the pilot burner and heating of the thermocouple 82, the bimetal element 102 is heated sufiiciently to warp and move the contact 161) out of engagement with the contact 98 to break the above traced series circuit and deenergize the igniter 94, reset coil 92 and heater coil 164.

Upon deenergization of the reset coil 92, the lever 66 moves away from the magnet frame 90 and into engagement with the fulcrum 68 under the bias of the spring 72, the bias of the spring 72 being further effective to rotate the lever 66 in a clockwise direction about the fulcrum 68 to move the bearing surface 70 into engagement with the contact bridge 64. Since the spring 72 is considerably stronger than the spring 62, the spring 62 is compressed and the contact bridge 60 is moved out of engagement with the contacts 56 while the contact bridge 64 moves into engagement with the contacts 58 to close a circuit therebetween. The armature element 84 remains in its attracted position due to the continued energization of the winding 76 by the heated thermocouple 82 and the various parts of the device are now positioned as shown in Fig. 3.

Deenergization of the heater coil 104 causes it to cool and permit the bimetal element 102 to return to its original form thereby closing the contacts 98, 160.

Movement of the contact bridge 64 into engagement with the contacts 58 of the switch 44 completes a circuit which connects the solenoid coil 36 of the electrically operable valve 18 across the secondary of the transformer 38 which circuit may be traced as follows: from one termi nal of the secondary of the transformer 33 to Wire 196, contacts 48, 46 of switch 40, wire 108, switch blade 54 and contact 52 of switch 42, wire 120, solenoid coil 36 of the electrically operable valve 18, wire 122, one of the contacts 53 of the switch 44, contact bridge 64, the other of the contacts 58 of the switch 44, wire 124, and wire 118 to the other terminal of the secondary of the transformer 38.

Current will now flow through the solenoid coil 36 of the electrically operable valve 18 to move the valve member 30 against the bias of the spring 32 to open position and fuel will flow to the main burner 10 where it will be ignited by the flame at the pilot burner 21 The electrically operable valve 18 will remain in fuel flow permitting condition as long as a flame exists at the pilot burner 20 and the switches 40, 54 remain closed and the flow of fuel to the main burner 10 will be under the control of the thermostatically controlled valve 16.

At the expiration of the predetermined heating period, the clock mechanism 51 will move the operating member 50 upward to separate the contacts 46, 48 of the switch thereby breaking the connection between the solenoid coil 36 of the electrically operable valve 18 and the transformer 38. Upon deenergization of the solenoid coil 36, the valve member 36 will return to its closed position under the bias of the spring 32 and fuel flow to the main burner 16 will be prevented.

If, during normal operation, the flame at the pilot burner 20 should be accidentally extinguished, the thermocouple 82 will cool and the supply of thermoelectric current provided thereby will be cut off to deenergize the magnet Winding 76. The armature element 84 will then move to its released position under the bias of a spring 86 and into engagement with the lever 66. Since the spring 86 is stronger than the spring 72, the bias of the spring 72 will be overcome and the lever 66 will be rotated in a counterclockwise direction, as viewed in the drawings, about the fulcrum 68 to move the bearing surface 70 out of operative engagement with the switch 44. The contact bridges 60, 64 of the switch 44 will move downward, as viewed in the drawings, under the bias of the spring 62, the bridge 60 moving into engagement with the contacts 56 and the bridge 64 moving out of engagement with the contacts 58. Such movement of the contact bridge 64 out of engagement with the contacts 58 will break the hereinbefore traced energizing circuit for the solenoid coil 36 of the electrically operable valve 18 and the valve member 30 will move to its closed position under the bias of the spring 32. No fuel can now flow to the main burner 16, however, movement of the contact bridge 69 into engagement with the contacts 56 once again completes the hereinbefore traced series circuit which includes the igniter 94, reset coil 92 and heater coil 104 and the hereinbefore described automatic starting operation to place the system in normal operating condition will be repeated. Thus, the system is recycling upon failure of the pilot burner and no attention on the part of the operator is required to return the systemto operating condition after flame failure.

While a single embodiment of this invention has been shown and described, it will be apparent to those skilled in the art that many changes may be made in the details of construction and arrangement of parts to accomplish the purposes of this invention without departing from the scope thereof as defined in the appended claims.

It is claimed and desired to secure by Letters Patent:

1. Control'apparatus for fluid fuel burners having main and pilot burners comprising in combination, valve means movable between controlling positions for controlling the flow of fuel to the main burner, electrically operable means for moving said valve means between said controlling positions, a switch for controlling the energization of said electrically operable means, an electromagnet having anarmature movable between attracted and released positions, said armature being operatively engageable with said switch in said released position for energizing said electrically operable means, thermomagnetic means responsive to a failure of flame at the pilot burner for preventing said armature from operating said switch to energize said electrically operable means in the absence of said flame, and switch means for controlling energization of said electromagnet, said armature being operatively engageable with said thermomagnetic means in said attracted position for resetting the same.

2. Control apparatus for fluid fuel burners having main and pilot burners comprising in combination, valve means movable between controlling positions for controlling the flow of fuel to the main burner, electrically operable means for moving said valve means between said controlling positions, a switch for controlling the energization of said electrically operable means, an electromagnet having an aramature movable between attracted and released positions, switching means controlling energization of said electromagnet, a fulcrum engageable by said armature in said released position, resilient means connected to said armature and effective in said released position to pivot said armature on said fulcrum into operative engagement with said switch for energizing said electrically operable means, and thermomagnetic means responsive to a failure of flame at the pilot burner for preventing said armature from operating said switch in the absence of said flame, said armature being operatively engageable with said thermornagnetic means in said attracted position for resetting the same.

3. Control apparatus as claimed in claim 2 wherein said flame responsive means comprises coil means, an armature element movable between attracted and released positions relative to said coil means, and means responsive to the heat of a dame at the pilot burner for energizing said coil means sufficiently to hold said armature element in said attracted position, said element being operatively cngageable with said armature in said released position of said element to overcome said resilient means, said armature being operatively engageable with said element in said attracted position of said armature to position said element in said attracted position thereof.

4. Control apparatus for fluid fuel burners having main and pilot burners comprising in combination, valve means movable between controlling positions for controlling the flow of fuel to the main burner, electrically operable means for moving said valve means between said controlling positions, a switch for controllingenergization of said electrically Operable means, an electromagnet having an armature movable between attracted and released positions, said armature being operatively engageable with said switch in said released position for controlling the position thereof, switching means for controlling energization of said electromagnet, coil means, an armature element movable between attracted and released positions relative to said coil means, and means responsive to the heat of a flame at the pilot burner for energizing said coil means sufliciently to hold said element in said attracted position, said element being operatively engageable with said armature in said released position of said element to prevent said armature from operating said switch, said armature being operatively engageable with said element in said attracted position of said armature to position said element in the attracted position thereof.

5. Control apparatus as claimed in claim 4 wherein timing means is provided for controlling the operation of said switching means.

6. Control apparatus for fluid fuel burners having main and pilot burners and a source of electric energy comprising in combination, valve means movable between controlling positions for controlling the flow of fuel to the main burner, electrically operable means for moving said valve means between said controlling positions, a switch for controlling energization of said electrically operable means from the source, an electric igniter for the pilot burner, a switch for controlling energization of said igniter from the source, an electromagnet having an armature movable between attracted and released positions, said armature being operatively engageable with said switches in said released position for controlling the operation thereof, and thermomagnetic means responsive to a failure of flame at the pilot burner for preventing said armature from operating said switches in the absence of said flame, said armature being operatively engageable with said thermomagnetic means in said attracted position for resetting the same.

7. Control apparatus for fluid fuel burners having main and pilot burners comprising in combination, valve means movable between controlling positions for controlling the armature and effective in said released position to pivot said armature on said fulcrum into operative engagement with said switches, and thermomagnetic means responsive to a failure of flame at the pilot burner for preventing said armature from operating said switches in the absence of said flame, said armature being operatively engageable with said thermomagnetic means in said attracted position for resetting the same.

8. Control apparatus for fluid fuel burners having main and pilot burners comprising in combination, valve means movable between controlling positions for controlling the flow of fuel to the main burner, electrically operable means for moving said valve means between said a controlling positions, a source of electric energy, circuit means for connecting said electrically operable means to said source, said circuit means including a first switch, an electric igniter for the pilot burner, circuit means for connecting said igniter to said source and including a second switch, an electromagnet having an armature mov able between attracted and released positions, said armature being operatively engageable with said switches in said released position for controlling the positions thereof, circuit means for connecting said electromagnet with said source, coil means, an armature element movable between attracted and released positions relative to said coil means, means responsive to the heat of a flame at the pilot burner for energizing said coil means suificiently to hold said element in said attracted position, said element being operatively engageable with said arma ture in said released position of said element to prevent said armature from operating said switches, said arma-f ture being operatively engageable with said element in said attracted position of said armature to position said element in the attracted position thereof.

9. Control apparatus as claimed in claim 8 wherein said circuit means for connecting said electromagnet to said source includes timing means for disconnecting said electromagnet from said source upon the expiration of a predetermined period initiated with the connection of said electromagnet to said source.

References Cited in the file of this patent UNITED STATES PATENTS 2,180,675 Gille NOV. 21, 1939 2,290,048 Hildebrecht July 14, 1942 7 2,391,753 Strobel Dec. 25, 1945 2,427,178 Aubert Sept. 9, 1947 2,449,135 Unger Sept. 14, 1948 2,475,430 Kronmiller July 5, 1949' 2,486,306 Main Oct. 25, 1949 2,510,265 Strobel June 6, 1950' 2,577,787 Mayer et a1. .Dec. 11, 1950 2,549,633 Ottman Apr. 17, 1951 2,610,682 Weber Sept. 16, 1952

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