US2576675A - Safety control system for heat appliances - Google Patents

Description

Nov. 27, 1951 D. F. DROW SAFETY CONTROL SYSTEM FOR HEAT APPLIANCES 2 SHEET'SSHEET 1 Filed Dec.

FIE-J D. F. DROW SAFETY CONTROL SYSTEM FOR HEAT APPLIANCES 2 Sl-iEETS--SHEET 2 Nov. 27, 1951 Filed Dec. 10, 1947 ff w I Patented Nov. 27, 195i UNITED STATES PATENT OFFICE 2,576,675 SAFETY eo'N'ritoL SYSTEM FOR HEAT APPLIANC Application Decem er 10, 1947, Serial No. 790,813

2 Claims.

The invention relates to thermostat control of the character described, there is usually p yided a main fuel burner for producing the us ful heatin the appliance and a constantly burning pilot burner designed for ignition of fuel as may from time to time issue from the main burner as the heating conditions for which the appliance is used callfor heat. In such control systems it is customary to provide a safety device operatedin conjunction with the pilot burner and responsive to the flame thereof to permit the flow of; fuel to the main burner only so long as the pilot burner is in proper operation and to shut off the fuel passage to the main burner on extinction of the pilot flame.

An objectof the present invention is to com bine in such control systems of the character described a safety thermo-responsive means which is operated by the attainment of an unusually high temperature of the appliance, that is a temperature somewhat above the upper limit of its normal operating range, to shut off the. flow of fuel to the pilot burner and thereby cause the shutting down of the appliance before a dangerously high temperature is reached, thus utilizing in a high temperature safety shut off control the safety pilot control customarily used with h a pli n ;lngther object of the. inventionis toprovide a high temperature safety shut off control which may beused in conjunction with all existing types of, pilot safety devices as. more fully hereafter characterized;

A further object ofthe invention is to provide a; safety device of the character described which may be incorporated in a self-contained unit for generally universal. attachment to existing types of safety controls.

Still anotherobject of the invention is. to provide asafety device. of the character above-which may be quickly and easilyadjusted to provide an forming'pa'rt of thespecification. It is to be understood, however, that variations in the show ing made by the said drawings and description may be adopted within the scope of the invention as set forth in the claims.

Referring to said drawings:

Figure 1 is a side elevation of a water heater incorporating the safety control system of the present invention.

Figure 2 is a side elevation partially in cross section showing a part of the safety control apparatus.

Figure 3 is a cross-sectional view of the control and is taken on substantially the plane of 3-4 of Figure 2. v

Figure 4 is a. cross-sectional view of the control taken substantially on the plane of 44 of Figure 3.

The safety control system of the present invention is illustrated in the drawing in conjunction with a water heater 6 of customary design including a storage tank I having water connections 8 and 9 therefor, and being heated at its base by a main burner II which is,'in turn, ignited by a pilot burner l2 here shown in conjunction with a safety control 13 more fully hereinafter to be described. Fuel such as gas, or the like, is fed to the burner I! through a thermostatically controlled valve device M which functions to open and close the fuel passage to the main burner as the Water temperature in the tank reaches predetermined low and high temperatures respectively. The device M is provided with what is sometimes referred to as a rod and tube thermostat it which extends into the tank in thermal contact with the water and is opera,- tively connected through an appropriate means 'to a valve in the fuel passage so that as the water temperature increases by reason of the heat generated by burner I I to a predetermined desiredfltemperature, the valve is closed to shut off the flow of fuel to the burner l l. Thereafter, as the water cools to a predetermined lower temperature, the valve is again opened by the thermostat so as to pass fuel to the main burner for ignition by the pilot burner l2. Various water heater thermostats are in use and are well un derstood in the art and, therefore, no fuller description is required here. For a complete description of such a thermostat reference is made to Vaughan, et al., Patent 2,238,837, dated April 15, 1941 for Temperature-Regulating Device.

Gas inlet conduit H is here shown connected to the thermostat I it and the latter is, in turn, connected by conduit I8 to the pilot safety control l 3 above noted, which is connected by conduit l9 to the burner H. The unit [3 may be of any one of a number of devices known in the art and functioning in response to the presence of flame at the pilot burner to normally retain open the passage connection between the thermostat l4 that the fuel issuing from the main burner be ignited by the pilot, as otherwise the fuel will escape from the appliance and become a potential danger, and since, in such instances, the main' burner is not in operation, the thermostat will continue to call for heat and thereby pour out additional fuel from the main burner. As aforesaid, several different types of pilot safeties have been used and are well understood in the art. These forms include a bimetal latch type of safety such as illustrated and described in Jenkins Patent 2,322,520 dated June 22, 1943; thermal electric types of safeties such as illustrated and described in Leins Patent 2,126,564, dated August 9, 1938; and deflecting tube type of safety such as illustrated and described in my Patent 2,530,942 issued on November 21, 1950. The latter type of safety is here used for purposes of disclosure.

' With reference to Figure 2 of the drawing, the pilot safety device l3 includes a body casting 2| having an interior passageway 22 connected at its opposite ends to inlet and discharge openings arranged for attachment of the conduits I8 and [9 above referred to. Formed interiorally in the passage 22 are annular valve seats 23 and 24 which are respectively engaged by valves 26 and 21 which are normally spring pressed to closed or seated position by springs 28 and 23. The valves are coaxially mounted on a reset mechanism 3| having one end extending from the front side 32 of the body and fitted with a knob 33 for manual engagement, and having an opposite end 34 projecting from the rear side of the body for abutment with a pin end 36 of a thermostat rod 31. The latter is enclosed in a thermally responsive tube 38 which is, in turn, heated on one side by the pilot burner l2 extending from the body 2| substantially parallel to the tube 38. Heating and cooling of the tube 38 by the pilot burner causes a lateral deflection of the tube, bringing the pin end 36 into an from abutting relation with the end 34 of the reset mechanism. The device is illustrated in its closed or off position corresponding to a failure or extinction of the pilot burner.

In this position of the parts, shut off valve 26 is closed, thereby preventing the flow of gas through the passage. To place the device in operation, the pilot burner I2 is ignited so as to heat the tube 38, and the reset knob 33 is pulled out so as to open valve 26 and position the end 34 in abutment with the pin end 36. In this resetting operation, valve 2'! is moved to a seated position before the opening of valve 26 so as to prevent the flow of fuel to the main burner until after the ends 34 and 3B are properly placed in abutment. Should the pilot flame thereafter be extinguished, the discontinuance of the application of heat to one side of the tube 33 will cause a deflector of the tube and a corresponding movement of the pin end 36 away from the reset end 34, thereby causing the va1ve'26 to move to a closed position under the urge of its closing spring 28. For a detailed description of this type of safety device and the full construction and operation of the reset mechanism 3!, reference is made to my co-pending application, Serial No. 783,284, above noted.

As will be seen from Figures 2 and 3, gas for the pilot burner 12 is supplied to the device by conduit 39 communicating with an interior passage 4! which terminates at its opposite end in a discharge opening 42 in which an end 43 of the pilot burner is mounted. In accordance with the present invention and as an important feature thereof, thermal safety means is provided, operated by an unusually high tank temperature, for shutting off the flow of fuel to the pilot burner in the event that malfunctioning of the other control parts causes such a high temperature to be attained. Thus, before a dangerously high temperature of the appliance and/or the associated or connected parts is attained, the gas flow to the pilot burner is shut off which, in turn, through the operation of the safety device 13, cuts off the flow of fuel to the main burner and thereby shuts down the operation of the heater. In the present disclosure, the high temperature safety responsive means is constructed as an essentially self-contained unit having a part 44 threaded through an opening 46 in the body 2! and containing a valve 41 which is engageable with a valve seat 48 formed in the passage 4 I.

With reference to Figures 1 and 3, the high temperature safety includes a capsule 49 which is adapted for mounting in direct thermal engagement with the tank 1, preferably at the top thereof as shown in Figure l, and is connected by a tube 5| to a bellows actuator 52 contained within the part 44 aforesaid, and actuated by the expansion of fluid in the capsule 49 to displace the valve 41 to its closed or seated position upon the attaining of a predetermined high temperature of the tank 1. Preferably the valve is actuated by snap action within a relatively narrow temperature range so that the operation of the pilot is not interfered with until the predetermined high temperature is reached and at that time the pilot flame is abruptly cut off. Accordingly, an appropriate snap action mechanism is interposed between the bellows actuator and the valve. As illustrated in Figure 3, one end 53 of the valve 41 is engaged by a tongue 54 formed centrally in a concave-convex, snap-acting disk 56 of the type illustrated in Vaughan Patent 1,988,345, dated January 15, 1935, for Snap Action Device. The latter is loosely supported at its outer periphery against a shoulder 51 provided internally in the part 44 contiguous with a cylindrical bore 58. Mounted for reciprocation within the bore 58 is a plunger 59 which is formed on one end thereof with an annular knife edge 6| engageable with the disc 56 adjacent its periphery, whereby upon movement of the knife edge 6| against the disk, the latter will be displaced to snap the tongue 54 through the center of the disk to thereby move valve 41 to its seated position. Desirably the end 53 of the valve is necked down to provide a recess 62 and the tongue 54 is slotted at 63 so as to fit into the recess (see Figures 2 and 3), thereby holding the valve and tongue in desired relation.

The bellows 52 is mounted within a tube part 64 which is attached to the body 44 to position the bellows 52 and the plunger 59 in coaxial relation whereby, on expansion of the bellows, its inner end 65 will move into engagement with the opposing end face 61 of the plunger. Desirably the bellows 52 is supported freely within the part 64 as by mounting an outer threaded shank end 68 only of the bellows to the part 64. As here shown, this arrangement is effected by means of a mounting washer 69 secured in place on the shank 68 by means of a lock nut H and which is, in turn, secured in an end recess 12 provided in the part 64 by means of a snap ring 13.

In accordance with the construction described,

and as an important feature thereof, adjustment is afforded between the various parts so as to enable selection of the predetermined temperature at which the device will operate. As shown in Figure 3, the part 64 is threaded into the bore 58 of the part 44 so as to selectively control the space between the bellows end 66 and the plunger face 61. In this manner the device may be set to operate at a desired predetermined high temperature and because of the snap action provided in the construction the operating range of the device can be reduced to a very narrow amount. Where the device is applied to a water heater, here illustrated, the adjustment is preferably set at the factory for about 200 F., and the snap action range can be reduced to about plus or minus 2. Usually the high temperature setting on a storage type water heater will be under 200 F. so that the high temperature safety device is not placed in operation unless there is a malfunctioning of the water temperature regulating thermostat 14. As will be understood, if the thermostat i4 fails to shut off the main burner after the water temperature has increased to the upper limit for which the thermostat I4 is set, the water temperature will continue to rise and unless stopped will ultimately produce steam and a backing up of the superheated water into the connecting lines where damage can be done to toilet bowls and the like. of the tank and connected parts is apt to cause the running of soldered joints variously used in controls and water heaters, and result in irreparable damage to the installation. Desirably,

therefore, the high temperature shut off device of the present invention is adjusted to operate at a temperature below the danger point to the installation and, as aforesaid, around 200 F. is entirely satisfactory. After adjustment, the parts 64 and 44 may be sealed in adjusted position by means of a solder ring I4.

Preferably and in accordance with the present construction the valve 41' is returned to an open position as soon as the temperature falls below the predetermined high temperature for which the device is set thereby leaving the pilot safety device I 3 in control of the operation of the heater as is intended for this type of device. This operation is effected in the present construction by using a spring acting disk 56 which will snap the valve 4'! to open position when the temperature has been reduced, the bellows 52 contracted and the pressure on the disk by the plunger released sufficiently to permit the disk to spring back to its normal position corresponding to the open position of the valve 41.

While the control system has been particularly described in connection with a form of pilot safety as illustrated in Figures 2-4 of the drawing, it will be readily understood that the high temperature cut off device can be used in the gas supply line to any other type of pilot burner and safety therefor. This adaptability is particularly facilitated by the construction of the high temperature cut off in an essentially self-contained unit including the capsule 49, tube 5|, and integrally associated parts 64 and 44, whereby the capsule 49 may be thermally engaged with any portion of a heat appliance to be controlled and the part 44 and associated valve 4'! connected in the fuel passage to the pilot burner. Where greater movement of the valve or of the snap actuating mechanism is desired, the capsule 49 may be replaced by a bellows.

Also, the overheating 3 I claim:

1. In a safety control system for a water heater having a storage tank and a main burner and constant burning pilot burner therefor, a valve adapted for mounting in the fuel line to the main burner for controlling the flow of fuel thereto, thermally responsive actuating means connected to said valve and adapted for thermal connection to said tank for opening and closing said valve in accordance with predetermined minimum and maximum temperatures respectively of the water in said tank, thermo-safety valve means responsive to the presence of flame at said pilot burner mounted in said fuel line to said main burner and functioning to permit fuel flow to said main burner only so long as said pilot flame is present, a valve positioned in the fuel line leading to said pilot burner, a capsule of thermally expansible fluid mounted in thermal contact with said tank, and expansible bellows having fluid connection to said capsule and expanded by the expansion of said fluid and connected to said last named valve for closing thereof and shutting off the fuel supply to said pilot burner upon increase of the temperature of the water in said tank to a predetermined high value above said predetermined maximum water temperature.

In a safety control system for a water heater having a storage tank and a main burner and constant burning pilot burner therefor, a valve adapted for mounting in the feul line to the main burner for controlling the flow of fuel thereto, thermally responsive actuating means connected to said valve and adapted for thermal connection to said tank for opening and closing said valve in accordance with predetermined minimum and maximum temperatures respectively of the water in said tank, thermo-safety valve means responsive to the presence of flame I at said pilot burner mounted in said fuel line to said main burner and functioning to permit fuel flow to said main burner only so long as said pilot flame is present, a valve positioned in the fuel line leading to said pilot burner, a capsule of thermally expansible fluid mounted in thermal contact with said tank, an expansible bellows having a fluid connection to said capsule and expanded by the'expansion of said fluid, and a snap acting mechanism positioned between and operatively connected to said bellows and said last named valve for snapping thereof to close position and shutting off the fuel flow to said pilot burner upon heating of the water in said tank to a predetermined high temperature above said predetermined maximum water temperature.

DONALD F. DROW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,711,443 Boyer Apr. 30, 1929 1,842,330 Le Pas Jan. 19, 1932 2,025,413 Hegwein et a1 Dec. 24, 1935 2,040,762 Spencer May 12, 1936 2,047,015 Dunham et al July 7, 1936 2,086,294 Craver July 6, 1937 2,210,446 Cerny Aug. 6, 1940 2,295,455 Dillman Sept. 8, 1942 2,383,401 Mantz Aug. 21, 1945

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