US2755852A - Control devices - Google Patents

Description

July 24, 1956 E. ANDREWS ETAL 2,755,852

CONTROL DEVICES Filed July 17, 1955 RAISE To REsET 178* THERMOSTATIC SWITCH 'Q- 3 INVENTORS FRED B. AUBERT 98 98 By GLENN E. ANDREWS ATTORNEYS CONTROL DEVICES Glenn E. Andrews, Lexington, and Fred B. Aubert, Wellesley, Mass, assignors, by mesne assignments, to Detroit Controls Corporation, Detroit, Mich, a corporation of Michigan Application July 17, 1953, Serial No. 368,708 14 Claims. (Cl. 158-125) Our invention relates to electrical control devices and in particular to devices wherein a pair of mutually im pinging flames is employed as a path for the flow of electrical energy.

It has long been understood and appreciated that a flame will conduct electrical energy, presumably because of the ionized condition of the hot gases constituting the flame. For example Reissue Patent No. 20,210 to Knowles, reissued December 22, 1936, discloses a combustion control system including a flame and a pair of electrodes mounted in the path of the flame, the arrangement being such that the supply of fuel to a burner was cut ofl in the event the flow of electrical energy through the flame. between the electrodes was cut off, if for any reason the flame should be extinguished. it was discovered, however, that such an arrangement was unsatisfactory because the electrical behavior of flames of diflerent gases varied widely. Specifically one gas might result in a flame in which the outer envelope was positively charged while the interior of the flame was negatively charged, while other gases would display the opposite arrangement of charges. This difficulty was overcome by providing a pair of flames which impinged mutually and formed together a path for the flow of current, as shown in United States Letters Patent No. 2,386,648 issued October 9, 1945, to-Aubert. The dual flame arrangement was successful in overcoming polarity eifects and rendered it possible to construct a control system which would operate regardless of the nature of the gas employed.

However, the prior art devices suffered from the fact that the magnitude of the current which could be passed through the flame or flames was so severely limited as to introduce various difliculties and in particular to'require the provision of relatively expensive, extremely sensitive auxiliary equipment.

Our invention is based on the discovery that if a pair of mutually impinging flames are so arranged that at least one of the flames also impinges upon a conducting plate connected in the circuit, the amount of current passed is very much greater than would otherwise be possible;

The discovery that the amount of current passing through flames may be greatly increased by causingthem to impinge upon a grounded plate may usefully be applied in divers instruments. However, we shall here confine further discussion to a combustion control device utilizing our discovery, a preferred embodiment of which is set forth in the following. detailed description and illustrated in the accompanying drawings, in which:

Fig. 1 is an elec'tro-mechanical diagram of a combustiorr control system embodying. our invention,

Fig. 2 is a view in elevation of the cam and switch contacts, and

Fig. 3 is a fragmentary view showing the interlocking arms in engaged position.

As shown in Fig. 1 the device embodying" our invention isar'range'd to' control the supply of fuel to a metal gas ice burner 40 of conventional construction employed to produce a gas flame as suggested at 42. The metal burner 40' is electrically grounded and receives its supply of fuel through a pipe 44' controlled by a valve 46 actuated by means of a solenoid 48, the arrangement being such that the valve 46 is automatically closed when the solenoid 48 is deenergized. Above and to one side of the burner 40 there is mounted a nozzle 52 receiving fuel through a supply pipe 54 and so mounted as to play a flame 50 uponthe upper surface of the burner 40. The supply pipe 54 is controlled by a valve 56 operated by a solenoid 58. Secured to the nozzle 52 is a spark plug or other ignition device 60 connected by a lead 62 to the secondary 64 of a conventional ignition transformer having a primary winding. 66.

Adjacent the nozzle 52 is another nozzle 72 mounted in position to play a gas flame 70 upon the flame 50 emitted by the nozzle 52. The nozzle 72 is served by a supply pipe 76 which is interrupted by a sleeve or bushing 74 of insulating material, the result being that the nozzle 72 is not electrically grounded. The supply pipe 76 is controlled by means of a valve 78 actuated by a solenoid 80.

Connected to the nozzle 72 is an electrical lead 82 running to one terminal of a crystal relay 84 which in turn is connected to a rectifier 86 and thence to the grounded secondary 88 of a transformer having a primary winding 90. The crystal relay 84 operates a movable contact 92 which moves with respect to a fixed contact number 94. Although a crystal relay has been found satisfactory (preferably with an appropriate time constant effected by the shunt resistor R1 of perhaps 50 megohms), we also contemplate a transistor or thyratron switching circuit of conventional form employed in place of the crystal relay.

Before proceeding to a description of the control circuit and elements thereof it may be advantageous at this time to discuss the general operation of the device. The circuit to be described is so arranged that the solenoid 48 which controls the valve 46 serving the supply pipe 44 for the main burner '40 may only be energized when current is passing through the flame 70, the crystal relay 84 serving indirectly to control the operation of the solenoid 48. Inthe circuit to be described, the first operation is to open the valves 78 and 56 so that gas may flow to the nozzles 52 and 72-. Simultaneously the ignition device 60 isen ergized, and the result is the establishment of the flames 50 and 70 and the closing of a circuit from the secondary of the transformer 88' through the rectifier 86', the crystal relay 84, the'lead 82, the nozzle 72, the flame 50 and 70, theburner 40, and back to ground. The function of the contacts 92 and94 operated by the crystalrelay 84"is to energize the so'lenoiddfl and open the valve 46 thus ausing gas toflow to the main burner 40 and become ignited by the flames Siian'd 70'. The circuit is pro'- vided with: means for clbsi'ngthe valves 56 and" 78' in the event the flame 70 is not established;- also all the valves are closed if for any reason there is a failure of current supply. The net result is that the valves 46, 56 and 78 may only remain open so long as current flows through the flame 70, the valves all closing in the event either the flame or the supply of current is-lost.

Coming now to thedetails" of the control circui't the relay contact 92 is connected through a lead 174m one side of the main electrical supply line. The relay contact 94 is connected through a lead 176 to one side of a second relay coil 96'. The relay coil 96' operates anelongated pivotally' mounted arm 98' projecting from the end of which is a relatively weak leaf spring 9Z The relay coil 96 also operates a first movable contact member 100, cooperatin with'fixed' contacts Inland I04; and a second movable contact 106, cooperating with fixed contacts 108 and 110. There is provided a cam 112 mounted for rotation upon a shaft 113 driven by a slow speed motor 115. A pair of relatively movable contacts 114 follows the surface of the cam 112, and an arm 116 of insulating material also follows the surface of the cam 112. The arm 116 carries a contact member 120 ccoperating with a movable contact 118 which in turn moves to and from another contact 122 mounted on an arm 123 carrying an insulating bushing 124 disposed in position to move a contact member 128 secured to an arm 126. The contact 128 moves to and from a fixed contact member 130.

A reset lever 140 is mounted so that it is ordinarily not in contact with the arm 116 but may be moved upwardly to lift the arm 116.

The main electrical supply line consists of a lead 160 on one side and a corresponding lead 180 on the opposite side. The lead 160 is connected to a source of alternating current through a thermostatic switch operated in conventional fashion to indicate a demand for heat,

The position and condition of the elements shown in Fig. 1 correspond to a condition in which the thermostatic switch has signalled for no heat, and the control device is therefore in a condition ready to relight the burner upon demand. However, under these circumstances the flames 42, 50 and 70 would not be burning and in this one respect the figure departs from the condi tion described.

The cam 112 is at rest in a position in which the arm 116 is partially elevated and not in its lowermost position. The contacts 114 are open; the contacts 118 and 1.20 are closed as are the contacts 128 and 130, but the contacts 118 and 122 are open as are the contacts 92 and 94. The relay 96 is deenergized so that the arm 98 is moved outwardly with respect to the arm 116, and the movable contacts 100 and 106 are in their right hand position in touch with the stationary contacts 104 and 106. The ignition transformer 64-66 is not energized, and the valves 46, 56 and 78 are closed, the solenoids 48, 58 and 80 being deenergized.

If now the thermostat signals that the burner 40 is to be relighted, there is established a circuit through the lead 160, the lead 162, the contacts 120 and 118, the lead 164, the contacts 100 and 104, the lead 166, the motor 115, the lead 168, and thence back to the other side of the supply line 180. As a result of the establishment of the aforesaid circuit the motor 115 turns the shaft 113 and the cam 112. The first result is the closing of the contacts 114 so that the timer motor 115 is now energized in parallel through the contacts 114 as well as the contacts 100 and 104.

As the cam continues its motion the arm 116 is elevated until the contacts 118 reaches the contact 122. When that occurs there is established a circuit from the lead 160 through the lead 162, the contact 120, the contact 118, the contact 122 and its arm 123, the lead 170, both solenoids 58 and 80 and thence back to the other side of the supply line 180. The energization of the solenoids 58 and 80 opens the valves 56 and 70 thus supplying gas or other fuel to the nozzles 52 and 72.

There is simultaneously established a circuit from the contact 122 and the lead 170 through the contacts 106 and 110 to the lead 172 through the primary 66 of the ignition transformer and then back to the other side of the supply line 180. The establishment of that circuit causes the ignition device 60 to be operated and thus to ignite the flames 50 and 70.

The establishment of the flames 50 and 70 closes a circuit energizing the secondary 88 of the transformer and establishing a circuit from ground through the secondary 88, the rectifier 86, the crystal relay 84, the lead 82, the nozzle 72, the flames 70 and 50, the burner 40 and then back to ground.

As a result of energizing the crystal relay 84 in the aforesaid manner, the contacts 92 and 94 are closed thus energizing the relay 96, the circuit being traced in this instance from the supply line 180 through the lead 174, the contact 92 and 94, the lead 176, the relay 96, the lead 178, the contact arm 126, the contact 128, the contact 130, the lead 164, the contact 113, the contact 120, the lead 162 and thence back to the other side of the supply line 160.

Upon the energization of the relay 96, the arm 98 is pulled inwardly, and the leaf spring 99 then strikes against the extreme end of the arm 116 and the spring is stressed. That is to say, the arm 98 moves farther in than the spring (which encounters the arm 116). Also there is established a circuit from the supply line 160 through the lead 162, the contact 120, the contact 118, the lead 164, the contact 100, the contact 102 (the contact 100 has moved to the left) the lead 178, the relay 96, the lead 176, the contacts 94 and 92, the lead 174, and thence back to the other side of the supply line 130. Consequently the relay 96 is now held energized through the contacts 100 and 102 as well as through the contacts 128 and 130. This is an important point because inspection of the circuit will show that it its uppermost position the cam 112 will raise the arm 116 and cause a separation of the contacts 128 and 130. If the contacts 128, and are opened before the relay 96 has been energized as a result of the establishment of the flame circuit, the circuit to the relay 96 cannot thereafter be closed, and the main valve 46 cannot be opened. However in normal operation the contact 100 reaches the contact 102 prior to the opening of the contacts 128 and 130.

Movement to the left of the contact 106 opens the circuit to the ignition transformer primary 66. Simultaneously the opening of the contacts 100 and 104 places the timer motor 115 exclusively under the control of the contacts 114. Moreover the contact 106 now touches the contact 103 with the result that the solenoid 48 is energized and the main burner valve 46 is open. Fuel leaving the burner 40 is immediately ignited by the presence of the flames 50 and 70. It should be evident from what has been said that unless the circuit is established through the flame 70, the relay 84 will not cause energization of the relay 96, with the result that the valve 46 will remain closed. That is to say, the main fuel supply valve cannot be opened unless a flame is present and unless also a supply of current is present. The motor 115 continues to turn the earn 112 until the arm 116 reaches its most elevated position at which the contact 128 is forced away from the contact 130. At the same time the arm 116 has now cleared the upper end of the leaf spring 99 which immediately snaps inward to underlie the end of the arm 116. The cam continues to turn and the arm 116 would drop to its lowermost position were it not for the support of the spring 99. The cam then continues to turn until it reaches the position shown in Fig. 1 at which time the lower of the contacts 114 encounters a drop in the cam and springs away from the upper contact, thus opening the circuit to the motor 115 and stopping further rotation of the cam 112.

The device is then in normal position for operation of the burner and nothing further happens, in normal operation, until the thermostat opens the supply line 160. When that occurs, all the relays, transformers, and solenoids are instantaneously deenergized, the result being to extinguish all the flames. When the thermostat again closes the supply line the whole cycle is repeated.

If for any reason the flames 70 or 50 are accidentally extinguished, the relays 84 and 96 are similarly deenergized and all the valves closed; the same thing happens if for any reason there is a failure of current to the control device. Since the flame 42 cannot be supported if the flames 70 and 50 are not burning, it makes no difference whether the flame 42 is accidentally blown out. If it should be blown out without an extinguishment of the.

flames 70 and 50, it would immediately be re-ignited. If all three flames are blown out, all three valves are closed.

There remains to be discussed the operation of the device in the event there is a failure of ignition during the time the device is being cycled to light the burner. If for any reason the flames 7i! and 50 are not established,

- the relays 84 and 96 cannot be energized. The motor 115 will continue to turn the cam 112 until the arm 116 encounters the drop in the cam and falls to its lowermost position. When this happens, the contacts 113 and 120 are separated, and examination of the circuit will show that the operation of all the elements is dependent upon the flow of current through the contacts 118 and 120; consequently the device is locked out of operation and cannot again be started until the reset lever 140 is raised manually and the contacts 118 and 12!) once more connect. During the reset operation the lever 140 keeps the contacts 118 and 122 separated.

It should also be explained that if there is a failure of flame or current while the main burner is on, the arm 98 will at once pull out and permit the arm 116 to drop, not to its lowermost position, but to the position shown in Fig. 1. Upon the restoration of current the device will accordingly repeat its normal ignition cycle, since the contacts 118 and 120 are not broken under these circumstances. If, however, the device goes through its cycle without establishing the flames, the arm 98 will not pull back in, and the arm 116 will accordingly then drop to its lock-out position.

In other words, the device of our invention discriminates between loss of current and loss of flame. If current is lost, the cycle will repeat automatically upon restoration of current to re-establish the flames. However if the flames are lost, one attempt is made to re-establish them and then the device is locked out of action. A discovery that the device is in lock-out position indicates trouble at the burner, generally with the fuel supply or the valves. At no time may the main fuel valve be open and no flame present.

It will now be apparent that we have devised an extremely effective and completely reliable device for controlling a burner. While we have illustrated a gas burner, those skilled in the art will readily appreciate that the device is equally applicable to an oil burner or, in fact, to any burner dependent upon a supply of fuel which may be valved.

It should also be noted that While the control circuit is through the flame 70, the presence of the flame 50 is also important not only as providing a pilot light, but also because when two impinging flames are used, the operation of the device is not dependent upon the polarization of the flame (which in turn depends on the chemical content of the gas and combustion conditions) but makes possible a device capable of being operated on any conventional gas or liquid fuel.

It must be borne in mind that the details of the embodiment herein shown and described are merely illustrative as but one of many modes possible. It will readily be appreciated that there are many possible variations in relays and cams, etc. which permit the desired operation of the device and that there are further axuiliary controls which might advantageously be employed, such as thermostatically controlled limit switches operating to cut off the flame when the temperature at a given location rises be yond a predetermined level.

Having thus disclosed our invention, What we claim as new and desire to secure by Letters Patent of the United States is:

1. A combustion control device comprising a burner of conducting material, a pair of metal nozzles disposed in position to play mutually impinging flames at least one of which impinges upon said burner, a fuel supply line to said burner, an electrically controlled valve controlling said supply line, means supplying fuel to said nozzles, means for applying a potential across one of said nozzles and said burner, and means responsiveto the flow of current through at least'o'ne of said'flames for operatingsaid electrically controlled valve.

2. A combustion control device comprising an electrically grounded fuel burner, a fuel supply line connected to said burner, a valvecontrolling said supply line, electrically operated means for actuating said valve, a pair of fuel burning nozzles disposed in position to play mutually impinging flames at least one of which impinges upon the surface of the grounded burner, means for applying a potential upon one of said nozzles through its flame to the burner, and circuit connections rendering. said valveactuating means responsive to the flow of current through said flame.

3. A combustion control device comprising a metal fuel burner, a fuel supply line-connected to said burner, a valve controlling said supply line, electrically operated means for actuating said valve, a pair of fuel burning nozzles disposed in position to play mutually impinging flames at least one of which impinges upon the surface of the burner, means for applying a potential upon one of said nozzles through its flame to the burner, and a relay actuated by the flow of current through the flame and connected to operate said valve-actuating means.

4. A combustion control device comprising. a metal fuel burner, a fuel supply line connected to said burner, a valve controlling said supply line, electrically operated means for actuating said valve, a pair of fuel burning nozzles disposed in' position to play mutually impinging flames at least one of which impinges upon the surface of the burner, meansforapplying a potential upon one of said nozzles through its flame to the burner, and a crystal relay actuated by the flow of current through the flame and connected to operate said valvev-actuating means.

5. A combustion control device comprising an electrically grounded fuel burner, a fuel supply line connected to said burner, an electrically operated valve controlling said supply line, a pair of'fuel. burning nozzles disposed in position to play mutually impinging flames at least one of which impinges. on the surface of said burner, an igniter disposed adjacent one of said nozzles, means electrically insulating the other nozzle from ground, means for passing electric current through the insulated nozzle and its flame to the grounded burner, and means actuated in response to the flow of' current throughv said flame for operating said valve.

6'. A combustion control device comprising an electrically grounded burner of conducting material, a pair of metal nozzles disposed in position to play mutually impinging flames at least one of Which'impinges upon said burner, a fuel supply line to-said burner, an electrically controlled valve controllingsaid supply line, means sup plying fuel to said nozzles, means for applying a potential across one of said nozzles and said burner, and means responsive to the flow of current through at least one of said flames for operating said electrically controlled valve.

7. A combustion control device comprising an electrically grounded fuel burner, a fuel supply line connected to said burner, a valve controlling said supply line, electrically operated means for actuating said valve, a pair of fuel burning nozzles disposed in position to play mutually impinging flames at least one of which impinges upon the surface of the grounded burner, means for applying a potential upon one of said nozzles through its flame to the grounded burner, and circuit connections rendering said valve-actuating means responsive to the flow of current through said flame.

8. A combustion control device comprising a metal fuel burner, a fuel supply line connected to said burner, a valve controlling said supply line, a solenoid associated with the said valve to actuate it, a pair of fuel burning nozzles disposed in position to play mutually impinging flames at least one of which impinges on the surface of said burner, one of said nozzles being insulated electrically from said burner, a source of current connected to said insulated nozzle, a switch, means interposed between the source of current and said electrically insulated nozzle for actuating said switch, and means controlled by said switch for actuating said solenoid.

9. In combination with a main burner, a pilot burner means for igniting said main burner, and means for igniting said pilot burner; control apparatus comprising a motor, a cam rotatably driven by said motor, first switching means actuated to closed position by said cam when said cam is in a first position, said first switching means controlling energization of said motor, second switching means actuated to closed position by movement of said cam to a second position for controlling energization of said igniter and passage of fuel to said pilot burner means, third switching means, means responsive to ignition of said pilot burner for closing said third switching means, an arm adapted to be moved to operative position for holding said first and second switching means in closed position, a relay energized by closing of said third switching means for moving said arm toward and adjacent its operative position, and means responsive to motion of said cam to a third position for permitting said arm to complete movement into operative position.

10. In combination with a main burner, pilot means for igniting said burner, and ignition means for said pilot burner means; control apparatus comprising a motor, a cam rotatably driven by said motor, switching means operable by said cam when said cam is in a first position for controlling energization of said motor, means including a switch for energizing said ignition means and passing fuel to said pilot burner means, said switch being closed when said cam is moved to a second position, a second switch, means responsive to ignition of said pilot burner means for closing said second switch, holding means adapted to be moved to operative position for holding said switch means and said first switch in operative position, a relay energized by closing of said second switch for moving said holding means toward and adjacent its operative position, means responsive to movement of said cam to a third position for permitting said holding means to complete movement into operative position, and means including a third switch operated by energization of said relay for supplying fuel to the main burner.

11. The device as set forth in claim 10 wherein a fourth switch is operated to open position when said cam returns to said first position for deenergizing said motor.

12. In combination with with a main burner, a pilot burner means for igniting said main burner, and means for igniting said pilot burner; control apparatus comprising a motor, a cam rotatably driven by said motor, a switch movable to closed position by said cam when said cam is in a first position for energization of said motor, means including a second'switch movable to closed position by movement of said cam to a second position for energizing said igniter and for passing fuel to said pilot burner means, a third switch, means responsive to ignition of said pilot burner means for closing said third switch, a holding member operative to hold said first and second switches in closed position, a relay adapted when energized to move said holding member toward and adjacent its operative position, circuit means including a normally closed fourth switch and said third switch for energization of said relay, a holding circuit means including a fifth switch and said third switch for said relay, said fifth switch being closed when said relay is energized, and means including a sixth switch actuated to closed position by energization of said relay for passing fuel to said main burner.

13. A device as set forth in claim 12 wherein said fourth switch is moved to open position and said holding member is moved into operative position when said cam is moved to a third position.

14. Combustion control device comprising a metal burner, a. fuel supply line connected to said burner, a valve controlling said supply line, a solenoid arranged to actuate said valve, a pair of nozzles arranged to play mutually impinging flames at least one of which impinges upon said burner, one of said nozzles being electrically insulated from said burner, an electric ignition device mounted adjacent the other of said nozzles, fuel supply lines connected to said nozzles, valves controlling said latter fuel supply lines, solenoids actuating said valves, a motor, a cam driven by said motor, a relay having switch contacts controlling said ignition device and valve solenoids, a switch arm bearing on said cam and having contacts controlling the circuit to one side of said relay, means for passing current through said insulated nozzle through its flame to the burner, means controlled by establishment of the circuit through said flame for controlling the circuit to the other side of said relay, the switch arm at one position on the cam being effective to cut off the supply of current to the relay and motor, and a member actuated by said relay for holding said switch arm out of said position unless the flame from said insulated nozzle ceases and thereby opens the circuit to the side of said relay through operation of said controlling means.

References Cited in the file of this patent UNITED STATES PATENTS 2,386,648 Aubert Oct. 9, 1945 2,427,178 Aubert Sept. 9, 1947 2,519,889 Crawford Aug. 22, 1950 2,618,323 Aubert Nov. 18, 1952 2,624,399 Thompson Jan. 6, 1953

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