|Publication number||US2494660 A|
|Publication date||Jan 17, 1950|
|Filing date||Nov 29, 1946|
|Publication number||US 2494660 A, US 2494660A, US-A-2494660, US2494660 A, US2494660A|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (6), Classifications (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
aienied cian. i?, i195@ HCE THERMGSTATICLHY @NTRLLED SFE- 'EY PMAM? BURNER AND lS'CH DEVKCE F915@ BURNER SYSTEMS to improvements in a provide the above described combination wherein the hood is of channel form adapted to protect the dame, and special means is provided for controlling the heating of the hood by the pilot :dame when the latter is relatively low.
My invention also contemplates the construction of the hood and operating arm of material having substantially similar coemcients of expansion and of approximately equal length so that they are substantially equally affected by changes in ambient temperature.
My invention also contemplates the com-bination of the preceding paragraph wherein the control member is an electrical switch of the type operable upon movement of the order of a few thousandths of an inch and wherein the switch and the fixed end of the hood have a common mounting means whereby a very ne control is obtained, as will be later described.
Other objects and advantages of my invention will be apparent from the accompanying drawings and description, and the essential features thereof will be set forth in the appended claims.
In the drawings,
Fig. 1 is a. side elevational view of one embodiment 'ofmy device, parts being broken away to more clearly show the construction;
Fig. 2 is a. bottom plan view of the same:
Figs. 3 and 4 are sectional views taken along similarly numbered lines of Fig. 1; while Fig. 5 is a diagrammatic view showing schematically one use of my device in a fuel control system.
Without in any way limiting myself to the speciflc form shown in the various views, I have disclosed a main burner I0 and pilot means II for lighting the same which is connected at I2 with a source of combustible fuel. The pilot is mounted in a block I3 which is rigidly secured in one end of the hood I4 which is of elongated channel form having an upper web Ila and down-turned iianges Ilflb so that the pilot name is protected against accidental extinguishing by being blown out and the pilot dame is directed to burner i0. The right-hand end of the hood it, as viewed in Figs. l and 2, is nxed to bracket means it. The lefthand end is free and positioned adjacent the burner i@ so that the pilot dame issuing from the left-hand end of the hood lights the fuel issuing from the burner. The channel ifi is of a material adapted to contract and expand under the in uence of the pilot flame for e, thermostatic control purpose, as will presently appear. Rigidly secured to the free end of the hood It is an operating arm i6. The securing means here shown comprises a V-shape band I'I welded or otherwise secured to the hood I4 and the arm I6. The free end of the arm I6, moving unrestrained in the opening ita of the bracket I5, is adapted to engage the operator I8 of an electrical switch I9 which is preferably mounted in the bracket I5. Obviously, any control device, either mechanical or electrical, might be so positioned to be engageable by the arm I6 to provide a control eiect upon expansion and contraction of the hood I4. For the purpose of providing a very fine control, where necessary, I have shown a switch I9 of the ty-pe adapted to be operated by movement of the member i8 a very small amount of the order of a few thousandths of an inch or less. Such a switch is shown in Patent No. 1,960,020 granted May 22, 1934 to P. K. McGall, but I do not Vdesireto be limited as to the actual switch used.
Obviously, various devices may be provided to 'prevent damage to the control member I9 upon over-travel of the arm I6. The specific means here shown comprises a plunger 20 held outwardly from arm IS by means of a relatively stiff spring 2I housed in the arm. The projection 2| acts as a part of arm I6 until the operator Il can move no farther, after which, spring 2| may Y lbe slightly compressed.l `"=This provision vfor overtravel is not essential tothe operationof my invention, butsome such provision is generally desirable.
Various means may be provided for controlling the adjustment of the plunger 20 with respect to the operator I8. I have here shown an adjustment Iwhich comprises the mounting of the member IBa on the arm I6 by a threaded connection, together with a lock nut 22 so that the effective length of arm IB may be adjusted as desired. My invention is not limited to any specific form for providing the adjustment of the space between members 20 and I8.
One manner of using my invention is shown schematically in Fig. where valve 2l controls the ow of fuel'through line 24 to burner I0. This valve is normally closed by spring 25 and is moved to open position -by the solenoid 28 when the same is energized from the electrical source LI,L2. The switch I 8 is of the normally closed type and is opened whenever the operator I8 is depressed. Obviously, whenever switch I9 ls in its normally closed position depression of the button 21 will close the electrical circuit so as to open valve 23 to supply fuel to the burner Iii.
In operation, when the hood I4 is cold, it is contracted in length and the operating arm Iii holds the member I8 depressed so that the switch I9 is open. In this position of the parts, the burner I0 cannot be supplied with fuel as there .is no pilot name to light it. When the pilot II is lit, the flame travels along the hood I4 issuing adjacent the burner I0 and the hood I4 is heated; causing it to expand. This draws the arm I6 toward the left, as viewed in Fig. 1, so that the plunger 2U finally releases the operator I8. whereupon switch I9 attains its normally closed position, whereupon the operator may press the button 21 so as to energize solenoid 26 causing opening of valve 23 and the supply of fuel through line 24 to the burner I0 where the fuel is ignited by the flame issuing from the hood I6.
It will be noted that the operating arm I6 is below the hood I4 in a position where it receives very little heat from the pilot ame.
A satisfactory device is provided where the hood I4 is of material which expands and contracts under the inuence of the pilot flame while the operating arm I6 is of material whose length is relatively unaffected by heat, such as Inval'.
There are special cases where a very fine adjustment is desired between the members 20 and I8 and this is particularly difficult where the safety pilot device is subject to ambient temperatures which vary widely. In such cases, I find it advisable to make the hood I 4 and the arm I8 of materials of substantially the same coeiicient of expansion. For instance, I have made them both of stainless steel with very good results. Utilizing this construction, if the ambient temperature should increase considerably, the hood I4 will expand and, since the right-hand end is xed, as viewed in Fig. 1, the left-hand end will move toward the left carrying the band I1 and the end of arm I6 in the same direction. However, the arm I6 being of substantially the'same length as the hood I4, and parallel thereto, will expand a substantially equal amount so that the end of the plunger 2|) will remain in substantially the same absolute position relative to the switch operator I8. When the switch andthe hood I4 are fastened to the same rigid body, as for instance the bracket I5, this setting may be held within extremely narrow limits. It will thus be seen that using this construction and using a micro-switch at I9, I have provided a control which is much finer than others known to me.
An improvement which may be used to obtain a still finer control is illustrated in Fig. 1, where the hole I4c is provided in the upper wall I4a of the channel-shaped hood, whereby an escapement of hot gases will provide a greater heat loss, thus producing a contraction of the channel I4 sufficient to shut off gas supply to burner I0 at gas pressures as high as one and eight-tenths inches of water pressure.
My safety pilot, however, provides an ignitable flame from the open end of channel I4 at extremely low gas pressures, even after the channel has contracted to a point where gas can not be supplied to burner III. 'Ihis device will provide suiilclent flame to ignite burner I0 at pressures as low as two-tenths of one inch water pressure. In other words, my device can be set to prevent gas supply to burner I!) when gas pressure drops below 1.8 inches water gage although the pilot name is still available at the open end of channel It until gas pressure drops below 0.2 inch water gage. This provides a wide margin of safety.
What I claim is:
1. Safety pilot construction comprising an elongated generally horizontal hood having xed and free ends, pilot means communicating with one end thereof for heating said hood, an elongated operating arm generally parallel to said hood and having one end fixed to the free end of said hood, said arm being relatively unaffected by the heat of said pilot means, said arm and said hood being substantially straight in both heated and cooled condition, a control member adjacent the other end of said arm and adapted to be operated thereby responsive to elongation and contraction of said hood under influence of said pilot means, and said hood and arm having closely similar coeiilcients of expansion and being of approximately equal length whereby they vary similarly in length responsive to ambient temperatures.
2. Safety pilot construction comprising an elongated generally horizontal hood having flxed and free ends, pilot means communicating with one end thereof for heating said hood, an elongated operating arm generally parallel to said hood and having-one end fixed to the free end of said hood, said arm being relatively unaifected by the heat of said pilot means, said arm and said hood being substantially straight in both heated and cooled condition, an electrical switch adjacent the other end of said arm and adapted to be operated by contraction of said hood when said pilot means is not heating.
3. Safety pilot construction comprising an elongated generally horizontal hood having iixed and free ends, pilot means communicating with one end thereof for heating said hood, an elongated operating arm generally parallel to said hood and having one end xed to the free end of said hood, said arm being relatively unaffected by the heat of said pilot means, said -arm and said hood being substantially straight in both heated and cooled condition, an electrical switch adjacent the other end of said arm and adapted to be operated by contraction of said hood when said pilot means is heating at a low rate.
4. Safety pilot construction comprising an elongated generally horizontal channel, said channel being of material expansible when heated, said channel having one end fixed and the other end free, a main burner adjacent the free end of said channel, pilot means providing a name within said channel adapted to travel from the xed end toward the free end thereof, an elongated operating arm generally parallel to said channel and having one end xed to the free end of said channel, said arm and said channel being substantially straight in both heated and cooled condition, and a control member adjacent the other end of said arm and adapted to be operated thereby responsive to elongation and contraction of said channel under influence of said ame, whereby 'said channel protects said flame from being extinguished while acting as a thermostatic control member and said channel provides means for conducting said pilot ilame to said main burner.
5. The combination of claim 4 wherein a hole is provided through the top wall of said channel intermediate its ends in position to pass a portion of the heat of said pilot flame through the top wall of said channel, whereby to reduce the heating effect of a flame upon said channel so that the latter will contract and operate said control member while pilot flame is s'till available adjacent said main burner.
6. Safety pilot construction comprising an elongated generally horizontal hood having xed and free ends. pilot means communicating with one end thereof for heating said hood, an elongated operating arm generally parallel to said hood and having one end fixed to the free end of said hood, said arm being relatively unaffected by the heat of said pilot means, said arm and said hood being substantially straight in both heated and cooled condition, an electrical switch operable by movement of the order of a few thousandths of an inch and having an operator adjacent the other end of said arm adapted to be operated by l5 UNITED STATES PATENTS Number Name Date 1,886,876 Gauger Nov. 8, 1932 1,963,957 Cunningham June 26, 1934 m 2,269,356 Beam et al Jan. 6, 1942 y 2,392,065 Rodgers Jan. 1, 1946 LEO KATHE.
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