Control system

May 23, 1939.

W. D. HALL

2,159,658

CONTROL SYSTEM

Filed Dec. 9, 1936

Sheets-Sheet 1

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May 23, 1939. w. d. hall 2,159,658

CONTROL SYSTEM Filed Dec. 9, 1936 4 Sheets-Sheet 2

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<img file="US2159658A_D0003.tif" />

May 23, 1939.

W. D. HALL

CONTROL SYSTEM

Filed Dec. 9, 1936

2,159,658

Sheets-Sheet 3

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May 23, 1939.

W. D. HALL

2,159,658

CONTROL SYSTEM

Filed Dec. 9, 1936

Sheets-Sheet 4

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Patented May 23, 1939

2,159,658

UNITED STATES PATENT OFFICE

2,159,958 CONTROL SYSTEM William D. Hall, EIMne, W. Va. Application December 9,1936, Serial No. 115,270 28 Claim». (CL 158—99)

This invention relates to control systems and more particularly to means for automatically igniting the fuel at a gas burner and has for its objects to delay the opening ot the fuel valve 5 until the igniter has reached igniting temperature; to close the fuel valve whenever the flame is extinguished; to delay reopening of the valve and reIgnition until any unburnt gas has escaped; to break the ignition circuit after ignl10 tion has been effected; to remove the Igniter from close proximity with the flame; to close the fuel valve if ignition is not effected, and to guard against opening of the fuel valve when the igniter is burned out. *

W I have found that prior to the arrival of gas at a hot wire gas igniter certain quantities of air are discharged adjacent the igniter and occasionally such air will have sufficient cooling effects on the igniter that the gas will fail to M ignite. To overcome this effect, I have provided means for repeatedly operating the igniter and the valve so that if the gas falls to Ignite, the valve will be closed for a short period. Ordinarily, upon reopening of the valve, the gas will 25 ignite immediately. To perform this result, I utilize a switch which is adjacent the burner flame and which repeatedly opens and closes until it is finally opened by heat dissipations from the burner. Under normal conditions, the switch 30 is opened due to heat from the flame before It has had time to open automatically.

The dominating feature of my invention resides in the provision of separate switches for controlling the igniter coil, and the valve. These 35 switches are arranged to open and close their circuits at different temperatures of the burner in such a manner that as the burner cools due to an accidental extinguishment of the flame, that the valve will be closed at a higher burner tem40 perature than the temperature at which the igniter is reenergized. This feature prevents the Igniter from being energized while gas is issuing from the burner, or while the burner chamber is full of unburnt gas. This principle is more 45 specifically defined in the annexed claims and I will therefore not attempt to recite here the numerous modifications and adaptations of this principle.

In the drawings,

Figure 1 is a schematic diagram of one form of my invention.

Figure 2 illustrates a simplified arrangement.

Figure 3 is an elevation view showing a method of mounting the various elements of the device illustrated in Figure 1.

Figure 4 is a sectional view of Figure 3 taken along the axis 4—4.

Figure 5 illustrates an Improved form of my invention.

Figures 6, 7, 8, 9, and 10 illustrate various 5 stages of the operation of the device Illustrated in Figure 5.

Figure 11 illustrates another form of my invention.

Figure 12 is a side view of the combustion-re- 10 sponsive switch of Figure 11.

Figures 1 to 4 inclusive are duplicates of the drawings of my copending application entitled, Ignition system for gas heaters, filed October 1, 1934, Serial Number 746,435, where there is shown 15 a room thermostat 5 which opens and closes the circuit according to the temperature of the room, the thermostat being connected at one side with the input line 50 and the opposite side connected by a conductor 51 with the igniter 6. The ig- 20 niter 6 is a helical heating coil located above and close to the burner 18 and is wound on a porcelain strip 30 which is carried by the bimetallic arms 20, 20, secured thereto by bolts 31, 32 and by screws 30 to a porcelain base 27. 25 The igniter 0 is a rather large heating coil and attains red heat. It is sufficiently large that it radiates energy to circuit breaker 7 and thereby modifies the responsiveness of this circuit breaker to heat from the flame. A conductor 52 30 leads from the igniter to the circuit breaker 7, the contacts 0 of which are normally closed. This circuit breaker may be of any detailed construction, being shown essentially as a bimetallic disc or diaphragm having its edge engaged with the 35 edge of an iron ring or drum 34, as shown at 33, the ring being secured by bolts 35 to the insulated base 27. From the contacts 8, a conductor 53 leads into a box or case 13 of porcelain where it terminates in one of the contacts 9, the 40 other of said contacts being carried by a bimetallic strip 10 which is connected to the Input line 54. A low resistance heater 11 is inserted in the line 54 and a high resistance heater forms a shunt around the contacts, that is, between con- 45 ductors 53 and 54. The contacts are separated by expansion of the strip 10 due to heat given off by said heater i I, and to attain certainty in the interaction of the heaters, the box 13 is made rather thick and will store heat for several min- 50 utes.

Tapped into the conductor 53 is one end of a solenoid 16 which has for its core the stem (7 of the fuel valve 55. It will be readily seen that the valve will be raised when the solenoid is en- 55

2,158,658 ergized thereby opening valve 56 whereby gas may flow through pipe 56 to the burner, and the valve will be closed by gravity when the solenoid is deenergized. The upper end of the solenoid is 5 connected by a conductor 57 with one end of a resistance coil 19, which coil is arranged near the circuit breaker 7, and has its opposite end tapped into the conductor 53. The solenoid and the resistance 19 are therefore in parallel. The heater 10 19 is of such size that its heating effects alone will cause expansion of the circuit breaker 7 to break the circuit after several minutes heating.

A bimetallic strip 14 is arranged near the igniter and is tapped into the conductor 51 by a 15 wire 58. Said strip carries a contact 38 which engages the contact 15, this latter contact being adjustable toward or from the contact 14 by a screw 40 (see Figure 4). When the gas is ignited, the heat of the flame will cause the arms 28 and 20 29 to bend and carry the igniter away from the flame. The distance from the flame obviously depends upon the temperature attained by the flame and the burner chamber. Therefore, when the burner chamber is relatively cool or when 25 the gas flame is low, the switch 14 will not move very far from the flame and will be heated to a fairly high temperature by the small flame. When the flame is high, the strip 14 will move an appreciable distance and will therefore not be ³⁰ heated to the extremely high temperature which it would have if it had remained immediately adjacent the flame but will be heated to only a fairly high temperature. Therefore, the adjustment of screw 40 does not appreciably depend ³⁸ upon the height of the flame, and the device will operate uniformly under the influence of changing thermal conditions. Since the thermostatic switch 14 is moved from close proximity to the flame, the time required for it to open its circuit 40 in event the flame becomes extinguished is substantially less than the time interval that would have been required if switch 14 had remained immediately adjacent the flame.

As was heretofore stated, the igniter supplies 45 heat to the circuit breaker 7. This feature of my invention has the advantage of increasing the responsiveness of the circuit breaker 7 to the flame without at the same time decreasing the operating temperature of the circuit breaker. Be⁸⁰ fore the flame is established, the igniter preheats circuit breaker 7 and upon establishment of combustion, the circuit breaker will terminate the energization of the igniter, thereafter operating in response to heat from the burner ⁸⁸ and resistance wire 19.

When the thermostat 5 changes from the “off” to the “on” position, the circuit is closed through the igniter 6, the circuit breaker 7, contacts 8, 9, strip 10 and small resistance ί I back to the source. ⁰⁰ The igniter heats and raises the temperature of the strip 14 so that it engages the contact 15, thereby establishing a circuit through the solenoid 16 and back to the line through the strip 10. Consequently, the valve is opened and gas flows to the ⁰ burner and is ignited, (the action of the parts in event the gas should fail to ignite is considered very shortly). Due to heat from the flame, the resistance 19, and the igniter, the circuit breaker ₇₀ will open and the igniter will be extinguished, the heat from the flame causing arms 28 and 29 to bend, as has been stated. Should the flame for any reason, be extinguished, the bimetallic elements 7 and 14 would cool, but since the element 75 i 4 is adjusted to open its circuit at a higher burner temperature than the temperature at which breaker 7 closes its circuit, the valve will be closed and unburnt gas given a chance to escape before reignition is attempted. Upon closure of the breaker 7 the igniter will be reenergized and an 5 attempt at ignition made. If this attempt at reignition, or if an original attempt at ignition fails, and the gas flows without igniting, the igniter will be deenergized after the heat therefrom with the heat from resistance 19 has caused the circuit 10 breaker 7 to open. Circuit breaker 7 opens and closes its circuit with a snap action; which I have found to be of importance. If this circuit breaker did not have a snap action, the operation thereof would be unstable inasmuch as upon closure it 15 reenergizes the igniter which liberates heat tending to reopen the breaker. By utilizing the “snap” feature, the breaker will open and close repeatedly with appreciable time intervals therebetween thus making several attempts to ignite the gas. In 20 each event, the resistance 19 is also active and this heater aids in producing the series of ignition attempts, and in fact, it is the operation of this heater which prevents the igniter from being energized before the valve is closed (during the 25 series of ignition attempts). After several ignition attempts, the heat liberated by heater 11 will have been stored around strip 10 in sufficient quantity to open the contacts 9 and the high resistance element 12 will be thereby placed in series SO with the line, and with the igniter, the solenoid, and the resistance element 19. Since resistance element 12 has a high value of resistance, it will limit the current through th^igniter etc. to such a low value that the igniter and solenoid will not 35 operate, however there will be sufficient heat liberated in casing 13 due to the heat dissipated by resistance 12 to maintain , the contacts 9 open. To restore the system to normal condition, it is necessary to turn off the line voltage until strip 10 40 has cooled. If the igniter should burn out, it would be impossible to operate any of the parts as all steps are dependent on the initial heating of the igniter.

In Figure 2, the burner is shown supplied with 45 gas through the valve 21 which has a stem 22. A bimetallic bar 23 is fastened at one end to a fixed bracket 25, and the other end thereof operates the stem 22. The igniter 24 is arranged under the strip 22 and directly over the burner and a time ⁸⁰switch 26 is inserted in the igniter circuit. The time switch is closed to energize the igniter and the heat of the igniter actuates the bimetallic strip so that after a definite time interval, the expansion of the strip will open the fuel valve permitting ⁸⁶gas to pass to the burner and burst into flame, The flame will keep strip 23 heated, thereby retaining the valve in open position as long as the flame continues to exist. After a definite time interval the switch 26 will automatically open ⁸⁰thereby deenergizing the igniter which need not operate once a flame is established.

The type of ignition control system described in connection with Figure 1 is intended for small stoves and heaters which are ordinarily located ⁸⁵directly in the room which is to be heated. The devices illustrated in Figures 5 and lO are more especially adapted for use on hot water heaters, gas furnaces, etc., where it is not desired to vary ₇θ the height of the gas flame and where it is not objectionable to locate a “flasher” in the burner flame. For these latter uses a quick acting device is necessary. The device of Figure 1 acts more quickly at every stage of its operation than the 75

9,158,608 ordinary devices of the prior art. The ignition devices of Figures 5 and 11, however, are very quick in operation and are capable of recycling at maximum burner temperature within twenty sec* onds. Ordinarily, however, at maximum burner temperature it is not necessary to relight the burner so quickly ancTl prefer to add weight to the sliding contacts until the recycling operation takes about one minute. In this case, should the 1· burner attain maximum temperature and for any reason, accidental or intentional, the flame become extinguished, the valve control switch will break its circuit in about ten or fifteen seconds. After one minute the Igniter will again be in the 15 circuit and the burner will be relighted if the thermostat calls for heat. With the adjustment of approximately one minute at maximum burner temperature, the recycling operation will occur in about twenty seconds at moderate burner temper99 atures. The thermal switches which control this quick operation are all arranged to be safe in their operation and in event of a fault or sticky switch, the gas cannot escape without igniting.

Referring to Figure 5, current is supplied to the 9* control system through the room thermostat RT and the safety switch SS and to the metallic supports 71 and 79 which are preferably composed of stainless steel. These supports are mounted on a base, such as the base 27 of Figure 4. Slidably ³⁰ supported by the supports 71 and 79 are bars 79 and 77 which are also composed of some form of stainless steel. The current traversing from support 71 to bar 74 Is negligible and the sliding contact is amply sufficient whereas for bar 77 it is ³⁵ preferable to Insert a small flexible conductor in parallel with the sliding contact 77, 79.

The strips or bars 74 and 77 are not rigidly fastened to supports 71 and 79 but are arranged to slide through these supports. Hence, the bars 10 will move when the bimetallic strips exert a force on them. Mounted on the base 65—99 are the bimetallic strips 66 and 79 which respectively carry contacts 94 and 95. The leg 69 of movable member 74 is composed of an insulating material 15 and consequently when this member is engaged by the bimetallic strip 66, no current will flow in the circuit 62; however, the short leg or finger 69 is composed of metallic material, preferably some high grade of electrical contact mate50 rial, and in event this finger is engaged by contact 94, a current will flow In circuit 92 as hereafter specifically recited. The bimetallic switch 79 engages 75 and 76, of which member 75 Is a high grade of electrical contacting material and is 55 in electrical connection with member 77, whereas member 76 is composed of an insulating material. When the burner is cool, the bimetallic strips have a relationship to the sliding members such as is illustrated in Figures 5 and 6. Stops 90 and 10 91 illustrated as dotted rectangles are fastened to bars 74 and 77 and prevent these bars from moving any farther to the right than their Illustrated position. Said stops are in engagement with the stationary supports 71 and 79 when the burner 15 is cool. Disposed adjacent the bimetallic strip 66, I have located the heating element 63 which may radiate heat to strip 66 but due to baffle 63 it cannot radiate heat to the bimetallic strip 79. In operative relation with one jet of the burner, Γ0 I have located a “flasher” 61 which consists of a hollow body portion having a hole near one end thereof. The Igniter 62 is located adjacent said hole and is connected in series with switch 95 and resistor 63. In the appended claims, the _rB word “igniter” or the words “ignition means” are considered broad enough to cover such variations in my principle wherein an added resistor is connected to the igniter-proper of Figure 1, the resistor serving to heat the thermal member 14. The flasher 61 may be used with either of my 5 other forms of devices but it is not recommended when the products of combustion of the stove are discharged into the room which is to be heated.

The principle of operation of the device which Is illustrated in Figure 5, may be explained in the jo following manner. When the room thermostat. RT closes the circuit, only one current path exists and this path may be traced as follows: 71—79— 77—75—65—79—igniter 62—resistor 13—68— RT. The current flow through the igniter raises j₅the temperature thereof to igniting temperature and the heat radiated from resistor 63 to bimetal lic strip 96 causes this strip to flex. The original positions of the bimetallic strips are illustrated in Figure 6. When heated, strip 96 flexes until con- «θ tacts 94 and 69 engage each other. This relationship of parts is Illustrated in Figure 7 and allows current to flow through two paths, one similar to the circuit previously recited, the other comprising: 71—74· 69 94 66 82—72—88— 25 RT. The energization of solenoid 72 causes the valve to be opened thereby establishing a flow of gas to the , burner. In event that the flow of gas should fail to ignite, the arrangement of parts illustrated in Figure 7 will not change apprecia- 30 bly until after a definite period of time when the safety switch will trip to its open position thereby deenergizing the igniter and the solenoid 72. In construction, the safety switch S3 may be similar to the switching arrangement in curing 13 « of Figure 1. Under normal conditions, the safety switch never operates due to the fact that gas from the burner flows into flasher 61 and is ignited by igniter 62. Upon ignition, the gases in the hollow body portion of said flasher expand 40 and tend to pass out of the flasher; however, since the hole adjacent the igniter is relatively «man practically no flames will pass out of this hole. Consequently, the greater percentage of the ignited gases in flasher 61 flash over the burner 4· ports 87 and 98 igniting the gases which emanate from those ports. The entire supply of fuel is soon ignited and the heat therefrom causes the bimetallic strips to bend to the left thereby opening contacts 85. In Figure 8, I have illustrated _Mthe relationship of the parts just after the igniter circuit is broken. As the burner continues to heat, the bimetallic strips 66 and 79 continue to move the members 74 and 77 to the left until at a very high temperature they reach a position — such as is illustrated in Figure 9. At this position, assume that the gas supply is accidentally stopped and immediately restarted, or «.«sump that the room thermostat RT is turned off and immediately turned back on. In either of these _mcases, the Are would be extinguished and when the flow of gas resumes it would escape. However, I have provided a control switch capable of recycling, and therefore, within a short period of time the burner will cool a few degrees and the u bimetallic strips 66 and 79 will disengage members 69 and 76 respectively. This operation is performed quickly due to the sliding feature hereinbefore mentioned. Immediately upon such disengagement the circuit to the valve is broken, ₇₀but the igniter will not be reenergized until a later period of time due to the fact that in addition to disengaging the member 76, the contact 85 must traverse the distance D (of Figure 9), before it closes its circuit, (see Figure 10). When yg

2,158,668 the Igniter switch 85 recloses, resistor 63 will raise the temperature of strip 66 until contact at 84 is remade. This latter action will reopen the valve 73 and an attempt to relight the burner will 5 be made as heretofore stated.

It is specifically pointed out that the sliding feature is a substantial improvement over a control system In which members 74 and 77 do not move. However, this improvement should not 10 act as a limitation to my broader claims as such are clearly of sufficient scope to cover the simple, yet effective, system wherein contact members 74 and 77 are stationary. In fact, my principle is even broader than electrical circuit arrangements 15 specifically recited above, and rather than attempt to list the numerous modifications which I have experimented upon and conceived, I am defining the principle in the appended claims.

The control system of Figure 11 illustrates 2o an improved form of sliding contact, in which the contacts rotate. Member 91 is pivoted to support 90 by means of the pivot 92. Bimetallic strip 97 is solely and rigidly supported at its left end and moves the rotatable structure with its free 25 end. The metallic member 91 carries the insulating member 94 and the metallic contact 93. When the burner temperature is falling, the strip 97 engages insulating member 94, whereas as the burner temperature is increasing, the contacts 30 93 and 96 are in engagement. Operatively related with strip 97 and in series with igniter 99, I have connected the heating element 98. The thermal switch 97 is associated with the burner flame, however, I prefer not to associate thermal 35 switch ί 01 with the heat from the burner. This latter thermal switch is heated by passage of current therethrough from the current transformer 100. The contacts of thermal ^switch 101 are closed when the switch is cool (ftb current from 40 the current transformer) and open when the switch is hot. The primary winding (high voltage or low current) is connected in series with member 91 and the gas valve solenoid 102.

When the thermostat calls for heat, current 45 passes through the igniter circuit, through thermal switch 101 and to the supply line. Upon closure of contacts 93—96 due to heat from element 98, the valve is opened and thermal switch I Of is energized. If the flame ignites, contacts 93 and ₅₀ 96 will remain in engagement, but if for any reason, the gas fails to ignite the heat generated in switch 101 will break the igniter circuit, and the current transformer will remain energized until resistor 98 has cooled and strip 97 disen55 gaged its contacts. When such disengagement occurs, switch 101 will close after a delay due to its thermal capacity, an inherent feature, and will make another ignition attempt. If several such attempts are unsuccessful, the safety switch will ₆₀ operate. Should the burner properly ignite and operate for any period of time after which the supply of gas should temporarily cease, strip 97 will cool and quickly open the valve circuit. As soon as switch 101 recloses, an attempt to relight ₆5 the burner will be made by reenergizing the igniter and element 98, the latter reheating switch 97 to thereby close its contacts.

In each ignition control, the valve arrangement of Figure 2 may be substituted for the solenoid valve with a consequent saving in cost.

This application is a continuation in part of my prior copending application #746,435, filed in the United States Patent Office on Oct. 1, 1934, and entitled Ignition system for gas heaters.