US3455640A - Compensated pilot burner - Google Patents

Description

July 15, 1969 F. M.WH|TE COMPENSATED PILOT BURNER 2 Sheets-Sheet 1 Filed July 26, 1967 INVENTOR.

FEEDER/CK M. WHITE mv Rm m mm BY M ATTOENE Y5.

July 15; 1969 F. M. WHITE COMPENSATED PILOT BURNER 2 Sheets-Sheet 23 Filed July 26, 1967 Fig.3

Fig. 5

INVENTOR. FREDERICK M. WHITE n. M M

ATTORNEYS United States Patent US. Cl. 431-51 6 Claims ABSTRACT GF THE DISCLOSURE The disclosure relates to a pilot burner having a pilot valve including a valve seat and cooperating valve member. An actuator means is provided for the pilot valve and includes first and second leg means. The second ends of the leg means are interconnected with the first end of the first leg carried on the valve body and the first end of the second leg means actuating the pilot valve. The leg means are formed of material having a positive thermal coeflicient of expansion to be acted on substantially equally by changing ambient temperatures for substantially constant ambient temperature compensation. Switch means is also provided as actuated by the actuator means, whereby the valve actuator leg may be heated as by a match to expand same and open the valve whereupon gas emitting therefrom is ignited and the pilot flame will maintain the valve rod expanded to maintain the pilot valve open. The switch is also actuated and this is used to control opening of the main valve to supply gas fuel to a main burner with which the pilot burner is used.

The fact that both leg means have a positive thermal coefficient of expansion establishes ambient temperature compensation and the fact that the pilot flame is essentially pirmarily on only one of the two leg means causes that one to be heated and expand more than the other to effect actuation of the pilot valve and of the switch. Pressure regulation is also achieved by the fact that if the pilot flame becomes larger because of increased gas pressure, this furnishes a greater proportion of heat to the other of the leg means and slightly increases the amount of closure of the pilot valve to decrease the pilot flame.

Background of the invention In gas burners such as used in household appliances, ranges, water heaters and the like, it is a common requirement that these devices be safe in operation. One requirement is that if the main burner be somehow accidentally extinguished, then the flow of gas to such main burner should be cut off. Uusally a standing pilot is employed in conjunction with such main burner and current safety regulations permit gas to escape from such pilot burner. even if accidentally extinguished, because this is a small amount of gas, so long as the appliance is adequately vented. However, other gas appliances which may or may not be adequately vented have more strict safety regulations whereby 100% gas shut-01f is required in the event that the main burner and pilot burner are extinguished. This means that the small amount of gas escaping from the pilot burner must also be shut off. This is termed a 100% gas shut off type of control. Such control systems which in the past have achieved 100% gas shut off have in general been fairly complicated requiring additional control systems, not only the one for the main burner but an additional control for the pilot burner, and the additional cost and complexity have mitigated against the general commercial use of such 100% gas shut off pilot burners.

Also, many of these pilot burners have not been compensated for changes in ambient temperature nor have Patented July 15, 1969 they been compensated for changes in gas pressure supplied to the pilot burner. This often has made the device erratic and unsafe in operation because false indications can be encountered by considerable changes in ambient temperature and also with different gas pressures. For example, the difference in gas pressure between winter and summer will cause a considerable difference in the size of the pilot flame and therefore cause a considerable difference in the temperature or length of time for operation in many prior devices.

Accordingly, an object of the invention is to provide a compensated pilot burner which obviates the above mentioned disadvantages.

Another object of the invention is to provide an ambient and pressure compensated pilot burner which is small and compact and simple and trouble free to manufacture and operate.

Another object of the invention is to provide a pilot burner having first and second leg means acting together as an actuator to actuate a pilot valve and also to actuate a switch controlling a main valve.

Another object of the invention is to provide a pressure compensated pilot burner wherein approximately the same gas flow is obtained even though the gas pressure input varies.

Another object of the invention is to provide a compensated pilot burner wherein approximately the same shut down time will be obtained for the different gas pressures.

Another object of the invention is to provide a compensated pilot burner wherein a combination of the pressure regulation and calibration will allow the use of a large orifice thus simplifying the manufacture and cost of the orifice considerably.

Another object of the invention is to provide a pilot burner which has fast opening and closing times.

Another object of the invention is to provide a compensated pilot burner wherein there is ambient temperature compensation with substantially constant gas flow and opening and closing times regardless of the change in ambient temperature.

Another object of the invention is to provide a pilot burner which is fail-safe.

Another object of the invention is to provide a pilot burner which is simple and rugged in construction and wherein the parts are protected against damage during shipping and in use.

Summary of the invention The invention may be incorporated in a pilot burner comprising, in combination, a valve body having a gas inlet to a recess, a pilot valve having a pilot valve seat and cooperating valve member, actuator means including first and second leg means, said first leg means having a first end carried on said valve body and having a second end remote from said body, said second leg means having first and second ends, means interconnecting said second ends of said leg means, means connecting said second leg means first end to actuate said valve member, said first and second leg means being made from materials having positive thermal coefficients of expansion, and one of said first and second leg means being heatable to expand and open said pilot valve to emit gas therefrom which will ignite and the pilot flame therefrom will maintain said pilot valve rod expanded and said pilot valve open, and the positive thermal coefficients of expansion of said leg means establishing ambient temperature compensation.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction With the accompanying drawings, in which:

Brief description of the drawing FIGURE 1 is a longitudinal sectional view of a pilot burner incorporating the invention;

FIGURE 2 is a sectional view on line 2--2 of the pilot burner of FIGURE 1;

FIGURE 3 is a side elevational view to a reduced scale of the pilot burner of FIGURE 1;

FIGURE 4 is an end View of the pilot burner of FIG- URE 3; and

FIGURE 5 is a schematic electrical and fluid circuit diagram.

Description of the preferred embodiment The figures of the drawing show the preferred embodiment of the invention, however numerous changes may be made as will appear herein. The figures show a pilot burner 11 including generally a valve body 12, actuator means 13, a switch 14 and a pilot valve 15. The valve body 12 may be made of metal such as steel and has a gas inlet 17 threaded at 18 to receive a gas inlet conduit, not shown. The gas inlet 17 leads to a recess 19 inside the valve body 12. The pilot valve 15 is incorporated in the valve body 12 and includes generally a valve seat 21 and a valve member 22. The valve seat 21 is conical as is the valve member 22, for cooperation therewith.

The actuator means 13 includes generally first leg means 24 and second leg means 25. The first leg means 24 is in the form of a U-shaped bracket having two legs 24A and 24B. The first leg means 24 has first and second ends with the first ends of these legs 24A and 24B fixedly attached to the valve body 12, as by welding 26. The bight 27 of the U-shaped bracket is the second end of this first leg means 24 and is positioned remote from the valve body 12.

The second leg means 25 includes a valve rod 29 and a switch actuator rod 28. Each of these rods has first and second ends and the second ends of these rods are threaded and received in tapped holes 31 and 30, respectively, in the bight 27 of the U-shaped bracket 24. The valve member 22 is coaxially fixedly attached to the first end of the valve rod 29 and may be unitary therewith. The first end of the valve rod 29 passes through a pilot flame port 32 from which the pilot gas may emerge to establish a pilot flame 33.

The switch 14 includes an insulator body 37 having a recess 38 closed by a metal cap 39. The metal cap 39 is fixedly attached to the metal valve body 12 in any suitable manner as by welding, and may serve the dual purpose of closing the switch body recess 38 as well as sealing the valve body recess 19. A movable switch contact 40 is carried in the switch 14 on a cantilever mounted movable switch blade 41. The movable switch blade 41 may be mounted in the insulator body 37 by a rivet 42 which fastens this blade and makes electrical connection to an external terminal 43. A relatively fixed contact 44 is mounted in the insulator body 37 and electrically connected to an external terminal 45. The movable switch blade 41 has a boss 46 for engagement with an insulator 47 on the first end of the switch actuator rod 28. The switch actuator rod 28 passes loosely through an aperture 48 in the valve body 12 as a guide for the first end of this switch actuator rod 28. Also this establishes the switch 14 on the opposite side of the valve body 12 from the pilot flame 33 for cooler and more trouble-free operation of the switch 14. The two rods 28 and 29 and the bracket 24 are preferably made from high-expansion stainless steel with a high positive thermal coeflicient of expansion. The pilot burner 11 is preferably mounted so that the rods 28 and 29 are horizontal and so that the planes of the two legs 24A and 24B are vertical and spaced on either side of the two rods 28 and 29 so that the pilot flame 33 impinges on the two rods 28 and 29 but not on the U-shaped bracket 24. The heat supplied to 4 this U-shaped bracket 24 is then by radiation rather than by direct impingement by the flame 33.

FIGURE 5 shows the foregoing pilot burner schematically in an oven burner circuit.

The terminal 43 of the switch 14 is connected to the lower end of a secondary winding 50 of a step-down transformer 51, which primary winding 52 thereof is connected through a manual switch 53 across a conventional 110l20 volt A.C. house current source 54. In one practical embodiment, the secondary voltage of the transformer may be 12 volts.

The upper end of the transformer secondary winding 50 is connected through a clock switch 55, an oven thermostat switch 56 and a conductor 57 to an operating coil 58 of an electrical device to actuate a main gas valve 59. The other end of the operating coil 58 is connected by a conductor 61) to the terminal 45. Terminal 43 is connected to the lower end of the secondary 50. The main gas valve 59 is connected in the gas supply line to a main burner 61, which may be the bake burner or the broil burner in the oven. A manually operable main shut off valve 62 is connected between a gas inlet manifold 63 and the electrically operated main burner valve 59.

The switch 53 is under the control of a manually 0perable control knob 65. The control knob 65 also is arranged to operate a pilot burner valve 66 connected to control the flow of gas from the outlet side of the main shut off valve 62 to the pilot burner 11.

Operation The pilot burner 11 is an ambient and pressure compensated pilot burner which achieves a gas shut off of the gas flow upon the flame being extinguished. In the room temperature position the switch 14 will be open and the pilot valve 15 will be closed. To light the pilot burner 11 one would move the manual knob 65 to open the pilot burner valve 66 and close the energizing switch 53. This energizes the transformer 51 and readies the circuit for energization of the operating coil 58. The circuit of FIGURE 5 is one typical application of use of the pilot burner 11 and many other circuits and applications are usable with the pilot burner 11.

Next, in putting the pilot burner 11 into operation, the valve rod 29 may be heated in any suitable manner as by a match flame, for example, or a glow coil 15, for example as shown in the Patent 3,311,157 issued March 28, 1967 and assigned to the same assignee as the instant invention. Upon heating the valve rod 29, the positive thermal coefiicient of expansion thereof will cause this valve rod 29 to expand longitudinally to open the valve member 22 relative to the valve seat 21. This will cause escape of the pilot gas from the flame port 32 and the gas will be ignited by the match flame for example to establish the pilot flame 33. This pilot flame 33 will contrnue to heat the valve rod 29 because it surrounds this valve rod thereby maintaining it heated and elongated to mainfiin the valve member 22 open relative to the valve seat The pilot flame 33 will also be directed upwardly by the escaping heated gas and the flame 33 will impinge on the switch actuator rod 28. This will heat such rod causing it to expand longitudinally to close the switch 14. In one actual application the opening of the pilot valve 15 was accomplished in about six seconds and closing of the switch 14 was accomplished in about 35 seconds. Closing of this switch 14 will energize the operating coil 58 to open the main gas valve 59 whereupon gas emitting from the main burner 61 will be ignited by the pilot flame 33. The pilot flame 33 will not impinge directly upon the two legs 24A and 24B of the bracket 24 but instead will be spaced in between these two legs and directed upwardly. Accordingly, these legs are heated not by impingement of the flame but only by radiation from the flame. Also the outer surfaces of these two legs 24A and 24B will not be subject to radiation from the flame 33 and hence these legs 24A and 243 will not be heated to as great an extent as the heating of the rods 29 and 28. Further legs 24A and 24B have a larger heat radiating surface and a larger surface radiating to a cold ambient, compared to the rods 28 and 29. Accordingly, even though the bracket 24 may have the same or substantially the same positive thermal coefiicient of expansion as the rods 28 and 29, this bracket 24 will not be heated to as high a temperature and hence will not expand longitudinally to as great an extent. The expansion of this bracket 24 will tend to reclose the pilot valve and will tend to reopen the switch 14, but the expansion of the bracket 24 will be insufficient under normal pilot flame operating conditions to actually close the pilot valve 15 or to open the switch 14. The action will be such that initially the pilot flame 33 is slightly larger than it will be after steady state conditions are reached in one or two minutes. This promotes rapid initial opening of the valve and closing of the switch. The slight closing of the pilot valve 15 will slightly reduce the proportion of heat given to the bracket 24 and accordingly a steady state condition will be reached when the proportion of heat to the bracket relative to the heat imparted to the rods 29 and 28 is just suflicient to expand the bracket 24 to the extent establishing the slightly smaller size pilot flame 33. This can be changed during manufacture by slightly changing the proportion of the mass of the rods 28 and 29 relative to the mass and size of the bracket 24 and also varying the spacing between the legs 24A and 24B. A closer spacing of these two legs transversely relative to the flame 33 will impart a greater proportion of heat thereto from the flame 33 whereas conversely a greater lateral spacing of these legs from the flame will impart a lesser proportion of heat to this bracket from the flame relative to the heat being imparted to the valve rod 29.

It will be seen that the flame heats one of the leg means 24 and 25 more than the other of the leg means. In this preferred embodiment, the one which is heated more is the leg means 25 or rod means, including the rods 28 and 29, and such greater heating is because of the direct play of the flames on these rods.

The slight closing of the pilot valve 15 establishes a fast shut down time of the pilot burner 11 upon extinguishing the pilot flame 33. If this flame 33 should b extinguished accidentally for example, the rod 29 will cool relative to the bracket 24 and this will be accomplished rapidly to close the pilot valve 15. Also the switch actuating rod 28 will rapidly cool relative to the bracket 24 to open the switch 14. This will de-energize the operating coil to shut oif the main supply of fuel to the main burner 61. Accordingly, there will be a 100% gas shut off, not only of the gas to the main burner 61 but also the gas to the pilot flame port 32.

Of course, the manual knob 65 may be operated off, when the main burner 61 is burning and the pilot flame 33 is also burning, to extinguish this main burner 61 and pilot flame 33. With the knob 65 turned to the off position, this will close the pilot burner valve 66 and open the energizing switch 53. This will de-energize the operating coil 58 to close the main gas valve 59 and it will also shut off flow of fuel to the valve body 12. However, the cooling of the pilot burner 11 will rapidly close the pilot valve 15 so that it will be ready for the next operation. Also the switch actuator rod 28 will shorten in length relative to the bracket 24 to open the switch 14 and hence the entire pilot burner 11 will be ready for the next cycle of operation, as described above.

The pilot burner 11 is ambient temperature compensated because the three elements 28, 29 and 24, namely the first leg means 24 and the second leg means 25 which includes the valve rod 29 and switch actuator rod 28 may all be made from the same material or very similar materials having a high positive temperature coeflicient of expansion. With this construction changes in the ambient temperature will aflect all of the leg means equally and therefore this will not have any substantial change on the position of the pilot valve 15 nor will it have any affect on the condition of the switch 14.

The pilot burner 11 is also pressure compensated because should the gas pressure increase this will temporarily increase the gas flow emitting from the pilot flame port 32. This will make a larger pilot flame 33. This will not heat the rods 28 and 29 to any materially greater extent, because they are already completely enveloped in the pilot flame. However, a greater proportion of this heat from the enlarged pilot flame 33 will be imparted to the legs 24A and 24B of the bracket 24 and hence this bracket 24 will expand slightly to slightly close the pilot valve 15. This will establish a measure of gas pressure regulation: Conversely, should the gas pressure be reduced, the pilot flame 33 will initially be reduced to impart an even lesser proportion of heat to the bracket 24 which will then be cooled and contract to slightly open the pilot valve 15 and slightly increase the size of the pilot flame 33.

The fact that the bracket 24 will be heated and will slightly elongate is a part of the construction of the pilot burner which establishes rapid shut down of the pilot burner in the event of the pilot flame being extinguished. In many prior art devices it often took as long as two minutes for the device to cool, especially with high ambient temperatures, in order for the pilot gas flow to shut off. In the present case, the pilot valve 15 may be closed in as short a time as 10 seconds. Also approximately the same shut down time will be obtained for different gas pressures as well as for different ambient temperatures;

The combination of the pressure regulation and calibration of the pilot burner 11 as manufactured and assembled, will allow the use of a large orifice at the valve seat 21 thus simplifying the manufacture and cost of the orifice considerably. Also, if the ceramic switch housing 37 or the ceramic insulator 47 should break, the flame switch will fail-safe. By this it is meant that the switch 14 will then be opened to de-energize the operating coil 58 to turn off the gas and the device will cool and thereby close the pilot valve 15. The U-shaped bracket 24 is a small rugged compact assembly which will protect the valve rod 29 and switch actuator rod 28 from accidental damage in shipping, handling and usage. The rods 28 and 29 may be provided with a screwdriver slot at the outer end for adjusting the position of these rods during initial calibration. They may then be sealed to maintain this exact calibrated position.

The main gas valve 59 may be double valve, one for a bake burner 61 and one for a broil burner, in a double burner oven for example. In such case there would be two operating coils, one for each portion of the double valve. The pilot burner valve 66 would in such case be a three way valve with one inlet and two outlets to selectively direct pilot gas to a pilot burner 11 associated with each main burner 61. Alternatively, with only the single burner 61 being used, the pilot burner valve 66 may be eliminated because the gas shut off of the pilot valve 15 will adequately control the pilot gas flow. In such case the manual knob 65 would control only the energizing switch 53 in order that an operator may selectively turn on or off the main burner 61 via the pilot burner 11.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of the circuit and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. A burner assembly comprising, in combination,

a valve body having a gas inlet to a recess,

a pilot valve having a pilot valve seat and cooperating valve member, actuator means including generally parallel first and second leg means, said first leg means having a first end carried on said valve body and having a second end remote from said body, said second leg means having first and second ends, means interconnecting said second ends of said leg means, means connecting said second leg means first end to actuate said valve member, said first and second leg means being made from materials having positive thermal coefficients of expansion, one of said first and second leg means being heatable to expand and open said pilot valve to emit gas therefrom which will ignite and the pilot flame therefrom will maintain said one of said first and second le means expanded and said pilot valve open, means including means positioning said first and second leg means to be heated substantially equally by ambient temperature changes and relying on the positive thermal coefficients of expansion of said first and second leg means to establish ambient temperature compensation, and said positioning means positions said leg means t efiect heating of the other of said leg means by the pilot flame as an incident to heating of said one of said leg means to tend to reclose said pilot valve, whereby pressure regulation is achieved by the fact that an increasing pressure causes a larger pilot flame to furnish a greater proportion of heat to said other of said leg means and slightly increase the amount of closure of said pilot valve to decrease the pilot flame. 2. A burner assembly as set forth in claim 1, wherein said first leg means is a U-shaped bracket with two legs, the first end of said legs thereof fixedly attached to said valve body, the bight of the U-shape being said second end of said bracket, the legs of said U-shaped bracket being disposed vertically on each side of said second leg means to be out of the path of the pilot flame but to be heated by radiation therefrom.

3. A burner assembly as set forth in claim 1, including a switch carried on said valve body, said second leg means including a switch actuator rod having first and second ends, means interconnecting said second ends of said switch actuator rod and said first leg means, and means to cause actuation of said switch by movement of said actuator rod first end.

4. A burner assembly as set forth in claim 3 wherein said switch actuator rod is made from a material having a positive thermal coefiicient of expansion, said second leg means including a valve rod, whereby changes in ambient temperature affect the two rods and first leg means substantially equally in expansion for ambient temperature compensation.

5. A burner assembly as set forth in claim 3 including a bracket as said first leg means, a valve rod as part of said second leg means to actuate said pilot valve, and wherein said switch actuator rod is positioned close to said valve rod for both to be heated by direct impingement of the pilot flame thereon for expansion of the switch actuator rod relative to said bracket to actuate said switch, and said bracket being spaced to one side of said pilot flame to be heated by radiation therefrom for expansion to a lesser degree than that of said switch actuator rod to tend to reopen said switch but not to open said switch under normal conditions of maintenance of the pilot flame, whereby upon the pilot flame being extinguished the two rods rapidly cool to rapidly open the switch and to rapidly close the pilot valve for 100% gas shut off.

6. A burner assembly as set forth in claim 3 including a main valve, electrical means to actuate said main valve to an open position, and circuit means connecting said switch to control said electrical valve actuating means.

References Cited UNITED STATES PATENTS 858,279 6/1907 Hall 431- 1,058,046 4/ 1913 Garber 431-77 2,578,087 12/ 1951 Peterson 431-42 3,282,325 11/1966 Jackson et a1. 43 l56 3,311,157 3/1967 Mertler et a1 431-46 FOREIGN PATENTS 476,204 8/1951 Canada.

FREDERICK KETTERER, Primary Examiner 1 US. Cl. X.R. 236-101; 431-77

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