US2687169A

US2687169A - Burner control apparatus with safety control means

Info

Publication number: US2687169A
Application number: US7203A
Authority: US
Inventors: Maurice George
Original assignee: Milwaukee Gas Specialty Co
Current assignee: Milwaukee Gas Specialty Co
Priority date: 1948-02-09
Filing date: 1948-02-09
Publication date: 1954-08-24
Anticipated expiration: 1971-08-24

Description

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Patented Aug. 24, 1954 BURNER CONTROL APPARATUS WITH SAFETY CONTROL MEANS George Maurice, Muskego, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis., a corporation of Wisconsin Application February 9, 1948, Serial No. 7,203

20, Claims. 1

This invention relates to a burner control apparatus with safety control means.

i While the particular embodiment of the invention which I shall describe hereinafter in connection with the drawings is a single point ignition system adapted for use with domestic gas ranges, it is to be understood that the invention is not limited to such use but may be employed for all similar purposes, for example, in connection with various commercial forms of apparatus having a baking oven burner, a broiler oven burner, or other burner remotely located relative tothe pilot burner.

In the usual domestic gas range, the pilot burner is in the form of a single, constantly burning pilot burner located in juxtaposition to the top burners at the upper part of the range, and the baking oven, broiler, or like burners are lo- Although the top burners are usually provided with a constantly burning pilot burner for lighting the same, at the present time a match is usually employed for lighting the baking oven, broiler or like burners.

The stooping and hazards of lighting an oven burner or thelike with a match are well known in the art.

An all gas ignition system has advantages over `electric systems, and it does not require electric supply connections and will maintain supply of gas to pilot burners,whereas a failure of electric power supply may interrupt the pilot burner operation. In general, electric power failure would automatically shut off the gassupply, i. e., `make the functioning of a gas appliance dependent upon another utility.

The copending `applications of Ernst Witzel, Serial No. 738,412, iiled March 31, 1947, and Serial No. 748,969, filed May 19, 1947, now U. S. Patent No. 2,527,286, and the copending application of Russell Matthews, Serial No. 742,017, led April 17, 1947, now U. S. Patent No. 2,578,194, provide an improved system of ash tubes and intermediate pilot burner means for assuring ignition of a pilot burner in juxtaposition to the oven or like burner from a constantly burning top pilot burner; also improved single point ignition systems wherein means, shown in the form of thermally responsive means, is providedfor extinguishing the intermediate pilot burner means and establishing a fiowoffuel to the oven or like burner after a time delay following ignition ofthe pilot burner for the main burner, and improved thermoelectric control devices and other instrumentalities for accomplishing the new and advantageous results set forth. The foregoing copending applications are owned by the assignee of the present application.

In the copending application of Ernst Witzel, Serial No. 744,905, led April 30, 1947, now U. S. Patent No. 2,645,280, the time delay is obtained by an orice limiting the escape of air compressed by the gas line pressure.

One of the main objects of the present invention is to provide a simple, improved, and effective system and control means which will provide the advantageous results obtained with the systems disclosed and claimed in the above identified copending applications, and in which the time delay does not require thermally responsive means and is not dependent upon the gas pressure in the fuel supply line.

Another object of the invention is to provide a system and control device of the class described in which the fuel supply for one or more intermediate pilot burners is denitely shut off after a given time interval and independently of the valve controlling the supply of fuel to the main burner.

Another object of the invention is to provide means wherein the time delay is set into operation by manipulation of the gas cock or other shut-off means.

Another object of the invention is to provide, for a system of the class described, one embodiment of the invention having improved shut-off and time delay means incorporated in a single device, and a thermoelectric generator operated device adapted to be separately installed, and another embodiment of the invention having improved shut-oi and time delay means and thermoelectric generator operated means incorporated in a single device.

Another object of the invention is to provide a system, control means, and instrumentalities therein, as will hereinafter appear, having various features of novelty and advantages, and which are particularly characterized by their simplicity in construction, their economy in manufacture and installation, and their eifectiveness in use.

Further objects and advantages of the invention will appear fromthe following detailed description, taken in connection with the accompanying drawings which illustrate the manner of constructing and operating an illustrative embodiment of the invention.`

In the drawings:

Figures 1 and 1A are parts of a diagrammatic View which, when placed with Figure 1A to the right of Figure l and the line B-B of Figure 1A on the line A-A of Figure l, form a complete diagrammatic view of one form of system and control means embodying the present invention;

Figure 2 is a fragmentary sectional view through the gas shut-off means taken substantially on the line 2 2 of Figure l; and

Figure 3 is a longitudinal sectional view through another form of device embodying the present invention.

Referring now to the drawings, the burner I is the baking oven, broiler, or other remote burner. It is usually located in the lower part of the range or other appliance.

The pilot burner 2 is the constantly burning pilot burner. It may be, for example, the top pilot burner for the top burners of a gas range, or other constantly burning pilot burner. The pilot burner 2 is usually located in the upper part of the appliance.

A fuel supply pipe 3 leads to the burner I for the delivery of gaseous or other fuel thereto, for example, through a mixing chamber 4 to which air is admitted through adjustable air inlets (not shown) as well understood in the art. The flow of gas through pipe 3 is controlled by a shut-off and time delay device 5, and by a thermoelectric generator (such as a thermocouple or thermopile) operated device 6.

The oven or like burner I is provided with an oven or like pilot burner 1 for igniting it. A flash tube 8 opens at its upper end directly beneath the flame 9 of the constantly burning pilot 2. This tube extends vertically downwardly from the pilot burner 2, and opens at its lower end at Ill directly above the flame (not shown) of an intermediate pilot burner I2. The intermediate pilot burner I2 is spaced laterally from another intermediate pilot burner I3 in juxtaposition or igniting relation with respect to the oven pilot burner 1. The lower end of the tube 8 has a branch I4 extending laterally therefrom and opening at its outer end at I directly above the flame (not shown) of the intermediate pilot burner I3.

The shut-off and time delay device 5 comprises a pair of valve body parts 2B and 2! secured together with a flexible diaphragm 22 clamped marginally therebetween.

Valve body part has a fuel chamber 23 pro- 5 l vided with a fuel inlet 24 (Figure 2) and fuel outlets and 23. Contiguous sections of fuel supply pipe 3 are connected to inlet 24 and outlet 25, which is for the delivery of fuel to the main burner I and pilot burner 1. connected by a pipe or tube 21 with intermediate pilot burners I2 and I3 for the purpose of supplying fuel thereto, as will presently appear. The constantly burning pilot burner 2 is supplied with fuel through a pipe or tube 23 connected at 29, with the fuel supply line 3' anterior of the shutyoff and time delay device. yA pipe or tube 33 is adapted to supply fuel to pilot burner 1 from fuel supply line 3.

Gas cock 32 or other gas shut-off means-such as a remotely controlled valve-has, for example, a tapered plug part rotatable in the wall of valve body part 20 adjacent tofinlet 24. The shut-off means 32 has a port 33 (Figure 2) adapted by turning of the shut-off means to be placed in register with inlet 24 and a passage 34 opening into chamber 23. The shut-olf means 32 is closed by turning it to position in which port 33 is out of register with passage 34 and inlet 24.

.An eccentric pin 35 projects from the inner end Thel ouder. 2t is f of shut-off means 32 for operation beneath levers 35 and 48. Lever 35 ispivoted at one end at 31 on body part 20. The opposite end of lever 36 is suitably connected, for example, by a slot and pin connection at 31' with a collar 33 slidable on a valve stem 39. One end of valve stem .'39 has sliding movement through a valve d3 at the axis thereof, and has a head or abutment 4I. The opposite end of stem 39 has sliding movement through a valve 42 at the axis thereof, and has `a head or abutment 43.

Valve 4i) is adapted to seat on a Valve seat surrounding the adjacent end of the outlet 25. Valve 42 is adapted to seat on a valve seat surrounding the adjacent end of the outlet 25. The valves 40 and 42 preferably have suitable yielding facings for cooperation with their respective valve seats. A coiled spring 44 is interposed between valve lil and the adjacent end of collar 38.

A coiled spring 45 is interposed between the valve 42 and the adjacent end of collar 38. A coiled spring 46, positioned as shown or otherwise as desired, is interposed between the lever 3B and the wall of the valve body part 23.

The second lever 43 is pivoted at one end, for example, by pivot 31 on Valve body part 25. The opposite end of this lever has an arcuate slot in which a pin 49, carried by lever 38, engages. A pin or stem 5E) is secured at one end to lever 48. The opposite end of pin 5I) is secured at 5I to diaphragm 22 at the axis thereof. A coiled spring 52 is interposed between lever 46 and a cover 53 attached to body part 20, preferably with a gashet therebetween.

An air filter 55 is clamped marginally between body part 2I and a filter cover plate 56. Chamber 51 is adapted for the entry of air into the same from atmosphere through port 59, air filter 55, and passage or port 58. Passage or port 58 is adapted to be closed by a valve 53 which seats on an annular valve seat under the action of a spring 3 I as shown.

A passage 62 opens from chamber 51 into a bore 63 which, in turn, opens through passage E4, air filter 55 and port 53 to atmosphere. The communication between chamber 51 and atmosphere through bore S3 is controlled by a tapered pin 65. vThe pin 55 is adjustable for the purpose of adjusting the amount of restriction or displacement of air from chamber 51 through bore 63, and thereby the time delay secured by the action of the diaphragm 22, as will presently appear.

The device B, which is operated by the thermoelectric generator, comprises a valve body part 15 having an inlet 16 and an outlet 11. Contiguous sections of the fuel supply pipe 3 are connected to inlet 16 and outlet 11, for example, by connecting the section of the pipe leading from the outlet 25 of the shut-off and time delay devi-ce 5 to the inlet 15 and the section of the fuel supply pipe 3 leading to the main burner I to the outlet 11.

Internally, valve body part 15 has a generally L-shaped outlet chamber 18 having a longitudinally extending part in open communication with the outlet 11 and a transversely extending portion dened by a cylindrical wall 13. An inlet chamber 8l] in open communication with the inlet 15 terminates at its inner end in a generally annular chamber which embraces the wall 19.

The wall 19 terminates in an annular valve seat 8l. An armature 82, of disc-like form, has a yielding or other suitable valve or valve facing 83 adapted to seat against the seat BI to shut olf the flow of gas from the inlet 16 to outlet 11. A

` hood 84 is clamped to the valve body part 15 by side of the coil 81 is connected by a lead 88 to one of the thermocouple elements 89 of a thermocouple 98 or other suitablethermoelectric generator (such as a thermopile). The other element 9| of the thermocouple 90 is connected to a lead 92 to the other side of the coil 81.

The thermocouple 98 and lead connections therefor may be of the general character disclosed and claimed in Oscar J. LeinsPatent No. 2,126,564, granted August 9, 1938, or it may be of any other suitable character, or in the form of a thermopile or other thermoelectric generator. The thermoelectric generator has one or more hot junctions, for example, the hot junction 93 which is placed in position to be heated by the flame of intermediate pilot burner I3 and by the flame of the pilot burner 1.`

In the illustrated embodiment of the invention, the electromagnet has a flux shell 95 and a spacer ring 96. The lower end of the coil spool 86 has an axial recess, and `disposed in this recess and interposed between spool 86 and armature 82 is va coiled spring 91 which operates to move armature 82 to retracted position and to seat valve 83 on valve seat 8| when the electromagnet is `deenergized. Energization of the electromagnet by heating of the hot junction of the thermocouple 90 is sufficient to lift valve 83 to open position against the action of spring 91. A hoodspring 98, interposed between the top of the spool 86 and hood 84, seats the shell 95 in the valve body part at |80. Assuming that the apparatus is in shut-down position with the main burner valve 40 and the shut-off means 32 in their closed positions and the intermediate pilot burner valve 42 in open position as shown in Figure l, the operation is as follows: y

When shut-off means 32 is turned (counterclockwise) as viewed in Figure l, pin 35 lifts levers 36 and 48;.c1osing valve 48 and opening valve 42. No gas can `flow to the intermediate pilot burners vI2 and I3 at this time however, since shut-,off means 32 is then closed. The lowen edge of lever 36 adjacent to pin 35 may be notched to permit the `pin to lift lever 48 to the desired position, although this may vary.

When gas cock or shut-off means 32 is turned to open position the pin 35 moves downwardly into spaced relation beneath levers 36 and 48.

This permits spring 52 to move lever 48 downr wardly. Due to the tapered pin 65, the air in or flashes back lto light theintermediate pilot burners |2 and I3.

The springs and headed ends of valve stem 39 are so arranged that as the lever 36 is moved downwardly by engagement of lever 48 withpin 49, it operates to open valve 40, and, a few seconds later, to close valve 42. The thermoelectric generator has been heated by intermediate pilot burner I3 to open Valve 83 during the delay, and the delay is such that a gas supply is set upto the pilot burner 1 `and main burner I for ignition of the pilot burner 1 from the intermedia-te pilot burner I3 before the valve 42 is closed to shut off the supply of fuel to the intermediate pilot burners I 2 and I3.

When the shut-off means 32 is turned in the opposite direction to closed position, pin 35 returns levers 36Iand 48 to their lifted positions. At this time the diaphragm 22 raises with the upward movement of the stem 5U, producing a suction in the chamber 51 which opens the valve 68 for free entry of air through the port 58 so that the closing of valve 4|) and opening of valve 42 will occur promptly upon closing of shut-off means 32 and without time delay such as would result if the air had to be drawn in through the restricted duct 63 in this operation of the device.

The time delay prevents the flow of gas to the burner when, after some operation, the gas cock or other gas shut-off means is closed and immediately opened again. In such case the 'thermocouple or other thermoelectric generator would chamber 51 beneath diaphragm 22 is released very slowly, thereby effecting a predetermined `and adjustable timedelay. The arcuate slot in lever 48 adjacent to pin 49 also provides a time delay before the pin 49 is engaged by lever 48. As the pin 49`is engaged by lever 48, the lever 36 moves downwardly with lever 48.

As long as valve 42 and shut-off means 32 are open, gas is delivered from chamber 23, outlet 26 and pipe or tube 21 to intermediate pilot burners I2 and I3. The unburned gas from the intermediate pilot burners rises in the tube 8, which is relatively cool to permitthis action. As it reaches the dame of constantly burning pilot burner 2, the gas is ignited and then` recedes be still hot enough to hold the valve 83 open and supply the burner with gas which could not be ignited by the pilot burners which have been extinguished by the closing of the gas cock. 'Ihis gas would then escape unburned and constitute a hazard. However, the arrangement and time delay of the present invention provides:

l. That upon opening the shut-off means 32 the time ldelay means maintains the valve 40 closed until the thermoelectric generator 98 is heated sufficiently by the flame of the intermediate pilot burner I3 to energize the coil 1 and open or maintain open the valve 83.

2. That a certaintime is given the thermocouple or other thermoelectric generator to cool and deenergize and close valve 83 so that, in case the flash tube system should fail to function, the valve 83 will be closed before valve 48 opens.

In the embodiment of the invention shown in Figure 3, the thermoelectrically operated means and the shut-off and time delay means are com bined in a single device.

The valve body parts |||l and III are secured together with a diaphragm I I2 clamped marginally therebetween. A stem or pin |I3 is secured at one end at ||4 to diaphragm 2 at the axis thereof, and operates reciprocably through an opening I I5. Theopposite end of the stem ||3 has an abutment ||6 between which and flange I|1 (in which opening I I5 is provided) is conned a coiled spring ||8. Intermediate its ends the stem I I3 carries a member ||9 which, with the device in the position shown in the drawing,`

cooperates with the adjacent end of a pin |20 to hold the thermoelectric valve |2| open and armature |22 in attracted position against the pole ends of the magnet frame I 23.

The outlet |24 is for delivering fuel to the main burner and the pilot burner for the main burner, and the outlet |25 is for the delivery of fuel to the intermediate pilot burners. The outlets |24 and |25 correspond to the outlets 25 and 26 of erated to open and closed positions.

The gas cock or other shut-oil means |40, which may be similar to the gas cock shown at 32 in Figures l and 2, is shown in closed position and may be rotated manually or otherwise op- It carries an arm |43 which cooperates with the adjacent plate of diaphragm ||2 and carries an actuating lmember |44 for actuating valve |2| to open position and armature |22 to attracted position by cooperation with the adjacent end of an arm |45, the opposite end of which is pivotally mounted at |46. which operates between the prongs of a fork |42 on the adjacent end of the lever |28.

When valve |2| is open, gas enters through the inlet |41 of the thermoelectric valve and passes through passage |48 and a tube |49 into the chamber for the gas cock |40. The pin |20 abuts endwise with the abutment |50 at the adjacent end of the stem of armature |22 and valve |2|. The member ||9, by cooperation with the adjacent end of pin |20, is adapted to hold armature |22 in attracted position and valve |2| in open position until the electromagnet has a chance to energize and the member i I6 has moved up to position clear of pin |20. The diaphragm ||2 and related mechanism constitutes a time delay, and the member ||9 holds the armature |22 in attracted position and valve |2| in open position during the time delay which is such as to permit the electromagnet to be energized by the heat of the pilot means on the thermoelectric generator. When the member ||9 is clear of the adjacent end of the pin and the electromagnet is deenergized, for example, upon extinction of the pilot flame, a coiled spring |52 closes valve |2|, and abutment of stem |5| with pin |20 moves pin |20 to the right from the position shown in Figure 3; a coiled spring |53 swinging arm |45 in a counterclockwise direction from its illustrated position.

The thermocouple |60 or other thermoelectric generator, such as a thermopile, which may be arranged, for example, as shown in Figure lA, is connected in circuit with the coil |6| of the electromagnet which includes the magnet frame |23 and the coil |6|.

Chamber |62 is adapted for the entry of air into the same from atmosphere through a port |63 and passage |64. Communication between atmosphere and chamber |62 is controlled by a tapered pin |65. The pin |65 may be adjustable for the purpose of adjusting the amount of restriction or displacement of air into chamber |62 through the passage |64 and thereby the time delay secured by the action of the diaphragm ||2.

The stem or pin ||3 carries a pin i4? Ports or passages |66 open from the chamber |62 to atmosphere. These ports or passages |66 are adapted to be closed by a valve |61 which seats on an annular valve seat |68, for example, under the action of a spring |69. An air filter may be provided as shown at 55 in the preceding embodiment of the invention.

The operation of the system shown in Figure 3 is, in general, as follows:

With gas cock in closed position as shown, the thermoelectric safety shut-off valve is held in open position by cooperation of the member H6 with the pin |20, admitting gas through passage |46 and tube |49 into the gas cock chamber. When the gas cock |40 is turned in a clockwise direction (Figure 3) to open position, the arm |43 moves away from the adjacent plate of the diaphragm ||2 permitting the spring ||8 to actuate the pin or stem ||3 upwardly as shown in Figure 3, and pin |4| carried by stem ||3 positions levers |28 and |29 in preparation for shutting off the intermediate pilot burner gas by the valve |21 and for opening valve |26 to supply the burner and the pilot burner therefor, which may be arranged as in Figure 1A. The diaphragm ||2 is urged upwardly by the spring H6. The time delay is secured by adjustable tapered pin |65 which permits a slow replacement of the air into the chamber |62 below diaphragm ||2.

After a regulated time interval the pin |36, through levers |26 and |29, and pin |li| and fork |42, operates to move valve |26 slowly to open position to establish a supply of fuel to the main burner and the pilot burner for the main burner. At the same time the valve |21 slowly closes to shut off the gas to the intermediate pilot burner. During the time delay provided by the diaphragm |i2, the electromagnet is energized by the heat of the pilot burner means on the thermoelectric generator, and as the member ||9 moves up to position clear of the pin |20 the energized electromagnet holds the armature |22 in attracted position and valve |2| .in open position. In case of pilot failure, the armature |22 is released from the electromagnet and the valve |2| closes and automatically shuts off all supply of fuel to the burner and pilot burners.

It is evident from the foregoingI that the system shown in Figure 3 has advantages over the preceding embodiment of the invention as follows:

a. Only one combination valve is required.

b. In case of ash tube failure, both the intermediate and the oven pilot burners and also the main burner supply are shut off by the thermoelectric valve after the time delay.

c. The thermoelectric valve may be operated by a thermocouple as distinguished from a thermopile.

d. The magnet and coil may be much smaller, and many of the parts are of standardized form.

The device illustrated in Figure 3 shows only one of the possibilities of arranging the various elements of such a device. It is to be understood that the arrangement may be altered completely without disturbing the general function of the control.

The sequence rof operations shows that intermediate pilot burners |2 and I3 are definitely closed to gas supply after the time delay, no matter whether they have been ignited or not; thus no gas can escape in case of flash tube failure. The particular mechanisms shown in the drawings represent only -certain illustrated solutions within the scope of the present invention for operating the valves 40 and 42 or |26 and |21 in the manner described.

Therefore the embodiments of the invention shown in the drawings are for illustrative purposes only, and it is to be expressly understood that said drawings and the -accompanying specification are not to be construed as a definition of the limits or scope of the invention, reference being had to the appendedclaims for that purpose.

I claim: i 1. In apparatus of the class described, in combination, a pair of valve body parts, a flexible diaphragm secured marginally between said valve body parts, one of said body parts having a fuel chamber provided with a first outletfor supplying fuel to intermediate pilot burner means and a second Aoutlet for supplying` fuel to a main burner, the other body part having an air chamber provided with a restricted and adjustable outlet, a first valve for `said first outlet, a second valve for said second outlet, a fuel supply line, shut-off means in said fuel supply line, and means within said fuel chamber, under the control of said shut-off means, and connected to said diaphragm for opening said second` valve and then after a time delay closing said nrst valve upon iznovement of said shut-o means to open posiion.

`2. Apparatus according to claim 1 wherein said last means comprises a first` spring actuated lever connected to said diaphragm and a second lever operable by said first lever after lost motion movement thereof for operating said rst and second valves as set forth.

3. Apparatus according to claim 1 wherein said last means comprises a rst spring actuated lever connected to said diaphragm and a second lever operable by said i'irst lever after lost motion movement thereof for operating said first and second valves as set forth and wherein there is intermediate pilot burner means connected to said first outlet, a main burner connected to said second outlet, an additional pilot burner in juxtaposition to said intermediate pilot burner means and said main burner, an electroresponsive valve in the fuel supply line for the main burner, and a thermoelectric generator subject to the heat of both said intermediate pilot burner means and said additional pilot burner and connected in cir-` cuit with said electroresponsive valve for operation of said valve to open position by the heating of said thermoelectric generator.

4. In apparatus of the class described, in combination, a first valve for intermediate pilot burner means, a second valve for a main burner, lever means for said valves, a shut-off device for shutting oif the fuel supply for both said pilot burner means and said main burner and comprising :a part mounted for turning movement, means under the control of said shut-off device and having means operable to prepare said lever means for closing said first valve and opening said second valve, time delay means operable firstly to open said second valve and then to close said first valve, thermoelectric control means comprising an electromagnet, an armature for said electromagnet, a safety shutoif valve connected to said armature, and means operated by saidshut-off means for actuating said armature to attracted position and said safety shutoff valve to open position.` i i `5. Apparatus according to claim 4 wherein said shut-off device has means for actuating the armature to attracted position and said shutoif valve to open position. i i

6.` Apparatus according to claim 4 wherein the time delay means has a chamber provided with means for displacing air from said chamber and wherein there is a restricted inlet for relatively slow replacement of air into said chamber.

7. Apparatus according to claim 4 wherein the time delay means has a chamber provided with means for displacing air from said chamber and wherein there is a restricted inlet for relatively slow replacement of air into said chamber, said chamber having a diaphragm and a stem connected to said diaphragm and carrying means for holding the armature in attracted position and said safety shuto valve in open position until the electromagnet has a chance to energize.

8. Ina system of the class described, in combination, a constant burning pilot burner, a main burner remote from said pilot burner, an ignition pilot burner adjacent to said main burner for igniting same, intermediate pilot burner means intermediate said constantly burning pilot burner and said ignition pilot burner for igniting said ignition pilot burner from said constantly burning pilot burner, a fuel supply line, a main burner valve for shutting off the supply of fuel for said main burner, an intermediate pilot burner valve for shutting off the supply of fuel for said intermediate pilot burner means, shut-off means in said fuel supply line, mechanical actuating mechanism operated by closing operation of said shut-off means to open the intermediate pilot burner valve for the intermediate pilot burner means and to close said main burner valve, timing mechanism having a time delay action Aimposed thereon by the operation of said mechanical actuating mechanism by the opening operation of said shut-oif means, said timing mechanism being operatively associated with said main burner valve and said intermediate pilot burner valve and rendered effective by the opening of said shut-off means to open said main burner valve for the main burner and to close the pilot burner valve after a time delay following opening of said shut-off means, a safety shut-off valve biased to closed position shutting off the flow of fuel to said main burner and said intermediate pilot burner means, a thermoelectric generator, an electromagnet energized by said thermoelectric generator and effective when so energized to hold said safety shut-off valve in open position, and means actuated by closing of said shut-off means for holding said safety shut-off valve in open position during the time delay in the opening of said main burner valve and closing of said intermediate pilot `burner valve.

9. In apparatus of the class described, in combination, a rst valve, a second valve, a third valve, mechanical actuating means operated by operation of said third valve rst to open said rst valve and to close said second valve, and pneumatic timing mechanism comprising a chamber having an inlet which is relatively unrestricted during the opening of said first valve and closing of said second valve and an outlet which is relatively restricted during the opening of said second vvalve and closing of said rst valve, said timing mechanism having a diaphragm for imposing a time delay action thereon by said mechanical actuating means upon operation by said third valve, said timing mechanism operating to close said first valve and to open said second valve after a delay period following opening of said third valve.

10. In apparatus of theclass described, in combination, a valve body, a flexible diaphragm dividing the interior of said valve body into a fuel chamber and an air chamber, said valve body having a first outlet for supplying fuel from said fuel chamber to intermediate pilot burner means and a second outlet for supplying fuel from said fuel chamber to a main burner, said valve body having an unrestricted inlet and a restricted outlet for said air chamber, a first valve for said first outlet, a second valve for said second outlet, a fuel supply line, shut-off means for said fuel supply line, and means within said fuel supply line under the control of said shut-olf means and connected to said diaphragm for-opening said second valve and then, after a time delay, closing said iirst valve upon movement of said shut-off means to open position, said air chamber being operatively related to said shut-off means and said rst and second valves to provide by said restricted outlet from said air chamber a time delay in closing said rst valve and opening said second valve following opening of said shut-off means, said unrestricted inlet for said air chamber enabling quick closing of said second valve and opening of said first valve upon actuation of said shut-off means to closed position.

ll. Apparatus according to claim l wherein there is a third valve ahead of said nrst and second valves and means for actuating said third valve to open position by the closing of said second valve.

12. Apparatus according to claim l0 wherein there is a third valve ahead of said first and second valves, and means for actuating said third valve to open position by the closing of said second valve, said third valve being held in open position after said second valve is opened by energization of an electromagnet.

13. In apparatus of the class described, in combination, a pair of coaxial valve seats, a pair of coaxial valve members one cooperable with one valve seat and the other cooperable with the other valve seat, a valve stem projecting axially through both of said valve members for movement therethrough, a collar slidable on said valve stem between said valve members, a pair of springs one interposed between said collar and one valve member and the other interposed between said collar and the other valve member, a pair of abutments on the projecting ends of said stem, and means for actuating said collar in opposite directions.

14. Apparatus according to claim 13 wherein the means for actuating the collar in opposite directions comprises lever means connected to said collar, movement of said collar in one direction actuating one of said valve members to a closed position through its cooperating spring and the other valve member to open position through one of the abutments onthe stem and movement of said collar in the opposite direction actuating the other valve member to closed position through its cooperating spring and the other valve member to open position through the other abutment on said stem.

15. Apparatus according to claim 13 wherein the means for actuating the collar in opposite directions comprises a pair of levers having a lost motion connection therebetween.

16. In a system of the class described, in combination, a constantly burning pilot burner, a main burner remote from said pilot burner, an ignition pilot burner adjacent to said main burner for igniting same, intermediate pilot burner means intermediate said constantly burning pilot burner and said ignition pilot burner for igniting said ignition pilot burner from said constantly burning pilot burner, a fuel supply line, a main burner valve for shutting oir the supply of fuel for said main burner, an intermediate pilot burner valve for shutting off the supply of fuel for said intermediate pilot burner means, shut-off means in said fuel supply line, mechanical actuating mechanism operated by closing operation of said shut-off means to open the intermediate pilot burner valve for the intermediate pilot burner means and to close said main burner valve, and timing mechanism having a time delay action imposed thereon by the operation of said mechanical actuating mechanism by the opening operation of said shut-olf means, said timing mechanism being operatively associated with said intermediate pilot burner valve and said main burner valve to close said intermediate pilot burner valve for the intermediate pilot burner means and to open the main burner valve after a delay period following opening of said shut-off means, said timing mechanism comprising a chamber provided with means for displacing air from said chamber, said chamber having a restricted outlet opening therefrom.

17. In a system of the class described, in combination, a constantly burning pilot burner, a main burner remote from said pilot burner, an ignition pilot burner adjacent to said main burner for igniting same, intermediate pilot burner means intermediate said constantly burning pilot burner and said ignition pilot burner for igniting said ignition pilot burner from said constantly burning pilot burner, a fuel supply line, a main burner valve for shutting off the supply of fuel for said main burner, an intermediate pilot burner valve for shutting off the supply of fuel for said intermediate pilot burner means, shut-off means in said fuel supply line, mechanical actuating mechanism operated by closing operation of said shut-off means to open the intermediate pilot burner valve for the intermediate pilot burner means and to close said main burner valve, and timing mechanism having a time delay action imposed thereon by the operation of said mechanical actuating mechanism by the opening operation of said shut-on means, said timing mechanism being operatively associated with said intermediate pilot burner valve and said main burner valve to close said intermediate pilot burner valve for the intermediate pilot burner means and to open the main burner valve after a delay period following opening of said shut-oir means, said timing mechanism comprising a chamber provided with means for displacing air from said chamber, said charnber having a restricted outlet opening therefrom which is adjustable to adjust the time delay.

18. In a system of the class described, in combination, a constantly burning pilot burner, a main burner remote from said pilot burner, an ignition pilot burner adjacent to said main burner for igniting same, intermediate pilot burner means intermediate said constantly burning pilot burner and said ignition pilot burner for igniting said ignition pilot burner from said constantly burning pilot burner, a fuel supply line, a main burner valve for shutting off the supply of fuel for said main burner, an intermediate pilot burner valve for shutting off the supply of fuel for said intermediate pilot burner means, shutoff means in said fuel supply line, mechanical actuating mechanism operated by closing operation of said shut-off means to open the intermediate pilot burner valve for the intermediate pilot burner means and to close said main burner valve, and timing mechanism having a time delay action imposed thereon by the opening operation of said shut-01T means, said timing mechanism being `operatively associated with said intermediate pilot burner valve and said main burner valve to close said intermediate pilot burner valve for the intermediate pilot burner means and to open the main burner valve after a delay period following opening of said shut-oir means, said timing mechanism comprising a chamber provided with means for displacing air from said chamber, said chamber having a restricted outlet opening therefrom and a less restricted air inlet to said chamber.

19. In a system of the class described, in combination, a constantly burning pilot burner, a main burner remote from said pilot burner, an ignition pilot burner adjacent to said main burner `for igniting same, intermediate pilot burner means intermediate said constantly burning pilot burner and said ignition pilot burner for igniting said ignition 4pilot burner from said constantly burning pilot burner, a fuel supply line, a main burner valve for shutting off the supply of fuel for said main burner, an intermediate pilot burner valve for shutting on the supply of fuel for said intermediate pilot burner means, shut-off means in said fuel supply line, mechanical actuating mechanism operated by closing operation of said shut-off means to open the intermediate pilot burner valve for the intermediate pilot burner means and to close said main burner Valve, timing mechanism having a time delay action imposed thereon by the operation of said mechanical actuating mechanism by the closing operation of said shut-off means, said timing mechanism being operatively associated with said intermediate `pilot burner valve and said main burner valve to close said intermediate pilot burner valve for the intermediate pilot burner means and to open the main burner valve after a delay period following opening of said shut-ofi means, a safety shut-off valve biased to closed position shutting oir the flow of fuel to said main burner and said intermediate .pilot burner means, a thermoelectric generator, an electromagnet energized by said thermoelectric generator and effective `when so energized to i hold said safety shut-off valve in open` position,

and means for actuating said safety shut-off valve to open position by the closing operation of said shut-off means.

20. In a system of the class described, in combination, a constantly burning pilot burner, a main burner remote from said pilot burner, an ignition pilot burner adjacent to said main burner for igniting same, intermediate pilot burner means intermediate said constantly burning pilot burner and said ignition pilot burner for igniting said ignition pilot burner from said constantly burning pilot burner, a fuel supply line.

a main burner valve for shutting off the supply of fuel for said main burner, an intermediate pilot burner valve for shutting ofi the supply of fuel for said intermediate pilot burner means, shut-off means in said fuel supply line, mechanical actuating mechanism operated by closing operation of said shut-off means to open the intermediate pilot burner valve for the intermediate pilot burner means and to close said main burner valve, timing mechanism having a time delay action imposed thereon by the operation of said mechanical actuating mechanism by the opening operation of said shut-off means, said timing mechanism being operatively associated with said main burner valve and said intermediate pilot burner valve and rendered eiective by the opening of said shut-off means to open said main burner valve for the main burner and to close the pilot burner valve after a time delay following opening of said shut-olf means, a safety shutoff valve biased to closed position shutting 01T the fl'ow of fuel to said main burner and said intermediate pilot burner means, a thermoelectric generator subject to the heat of said intermediate pilot burner means, an electromagnet energized by said thermoelectric generator and effective when so energized to hold said safety shut-on valve in open position, means actuated by closing operation of said shut-off means for actuating said safety shut-off valve to open position, and means for holding said safety shut-olf valve in open position until said thermoelectric generator is energized by the heat of said intermediate pilot burner means, said last means being operated to released position by the ,time delay mechanism when the time delay mechanism is rendered effective by the opening of said shutoff means,

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