US3402887A

US3402887A - Burner control device for a water heater

Info

Publication number: US3402887A
Application number: US558012A
Authority: US
Inventors: Charles D Visos
Original assignee: Emerson Electric Co
Current assignee: Emerson Electric Co
Priority date: 1966-06-16
Filing date: 1966-06-16
Publication date: 1968-09-24
Anticipated expiration: 1985-09-24

Description

. Patent 3,402,ss1.. i BURNER CONTROLDEVICE FORA ,WATERHEATER h les' l y s l t. Lm [Mo-f ss E e ectri'cCo.,"St.L0uis, Mo., a corporation of Missouri Filed June16,"196 6,"Ser.' No; 558,012

4"Cl'aims;(Cl.'236;21)

xThisinvention relates to automatic fuel .flow control devices'for water heater gas burners which have valve and temperature responsive'valveactuator means for controlling the flow of gas to the burner in accordance with heat requirements to maintain a selected Water temperature and an electromagnetically operated cutoff valve dependentupon'e'lectrical energy generated by a pilot burner heated thermocouple to hold it open; and it particularly concerns the provision, .construction,--and disposition within the water tank of a normally closed, temperature responsive switch which controls the thermocouple, electromagnetic, cutolf valve circuit and. which opens in response to a predetermined high water temperature to de-energize the electromagnetic cutoff valve and effect its closing.

.An object of the invention is to.provide a fuel flow control device for water heater gas burners having an electromagnetically operated cutoff valve and an energizing circuit therefor including asa. power source a thermocouple heated by a pilot burner flame, in which a normally closed. temperature responsive switch disposed in good heat. transfer relationship, with the water being heated isincluded in. the energizing circuit and is .operative in response to. a predeterminedhigh water temperature to open, therebyto de-energize .the .electromagnetically operated-cutoff valve.

,1 Afurtherobject is to ,providemeans encapsulating and supporting a temperature responsive switch within a water heater tank in good heat transfer relationship with the water being heated. i

Other objects and advantages will appear from the following .description and accompanying drawing.

- In the drawing: M I

FIG. 1 is across-sectional view,-.With parts shown in full, .of acontrol device forwater-heater gas burners constructed, in accordance with the present invention and shown in association .with, awater, heater tank;

FIG." 2 is. an enlarged fragmentary, cross-sectional view taken on line 2- 2 of. F,IG. 1; 1

F IG..3.is alongitudinalcrossrsectional view of the electromagnetically operated cutoff valve and its circuit connections;

FIG. 4 is a side elevational View of the temperature responsive switch; 1 'FIGUS is across-sectional view-of the temperature responsive switch taken on line 5-5 =of FIG. 4; and

FIG, 6 is an enlarged cross-sectional view taken on line 66ofFIG. 1. .2

Referring to the drawing, the, fuelflow control device comprises a valvebody 1 0 h'avingfront and rear cover members 12 and 14, respectively, attached to the body "by screws 16. The body 1Q' is provided with an inlet passage 18, a. cutoff .valve'- chambe"r"20, a main valve chamber 22, and a main burner fuel supply outlet 24. A tapered bore 26;and*anlaxially aligned cylindrical bore 28 extend inwardly from opposite sides of the body 10 and intersect the cutoff Valve chamber 20. The tapered bore 26 receives a hollow, tapered, rotatable plug cock 30, the open inner end of which extends into cutoff valve chamber 20 and forms an annular valve seat 32. The cylindrical bore 28 receives an electromagnetic cutoff valve assembly, generally indicated at 34, which includes a poppet valve 36 biased against valve seat 32 by a spring 13. An operating rod 11 axially slidable in plug cock 30 ice and having an external hand knob 17 is arranged to engage cutoff valve 36 and move it openward when knob 17; is pushed inwardly. The operating rod 11 and knob 17 are biased outwardly by a spring ,19.

The hollow plug cock 30 is provided with a circumfer entially extending slot in the wall thereof forming a pilot burner port 38 which permits flow from the interior of the plug cock to. a pilot burner outlet. passage 40 from whence the fuel is conducted to a pilot burner 43 through a conduit 41. The plug cock 30 is also provided with a circular main port 42 in the wall thereof which, when in registry with a body passage 44, permits fuel flow from the interior of the hollow plug cock to the main valve chamber 22. The circumferentially extending pilot port 38 permits rotatable positioning of the plug cock so as to permit flow to the pilot outlet 40 only, or so as to permit flow to the pilot outlet 40 and main valve chamber 22 simultaneously. A main poppet valve 46 biased in a closed position on an annular seat 48 by a spring 50 controls the flow from main valve chamber 22 to the main burner outlet passage 24. The main valve 46 has a stem 52 attached at one end to the valve and its opposite end is arranged to *be engaged under certain conditions by the central portion of a thin, circular, concave-convex, flexible metal disc 54. The disc 54 has a normal free form, as shown in FIG. 1, in which it is concave with respect to the adjacent end of valve stem 52. The disc 54 is poised between a fixed, annular, knife edge 56, which engages the disc on its concave side very near its peripheral edge, and an annular knife edge 58 of slightly smaller diameter formed on the inner face of an axially movable member 60, which engages the disc on its convex side. A slight inward movement of member 60 causes disc 54 to pass through a planar shape to an opposite concavo-convex form with a snap action to engage the adjacent end of valve stem 52 and open the valve 46.

The outer face of movable member 60 is provided with a hemispherical boss 62 engaged by the free end of a lever 64, the lever 64 being pivoted at its other end on the ballshaped end 66 of a threadedly adjustable rod 68. The rod 68 is provided with a hand knob 70 on its exteriorly projecting end. The rear body cover member 14 is provided with an integrally formed, outwardly extending, cylindrical, hollow boss 72 having an exteriorly threaded outer end portion threadedly engaged in an internally threaded bushing 74 welded into an aperture in the wall of a water heater tank, shown fragmentarily at 70 in FIG. 1.

The cylindrical hollow boss 72 has a circular concentric bore 76 extending inwardly from its outerend to a square bottom 78. Extending inwardly from the bottom 78 of bore 76 and through the boss 72 to the interior of the body is an eccentrically positioned bore 80 and a crescent-shaped passage '82 concentric with the bore 80. The bore 80 is threaded to receive the reduced diameter end portion 84 of a tube 85. The tube 85 and a concentric rod 86 of a lower thermal expansion rate than the tube form a conventional rod and tube, differential expansion thermostat,'the operation and construction of which is well known in the art. The rod 86 extends inwardly beyond the inner end of tube 85 and engages the lever 64 at an intermediate point therealong. The rod 86 and tube 84 extend outwardly from boss 72 into the water tank.

An elongated tube 88 having a closed outer end and an open inner end is arranged closely alongside and coextends with tube 84 into the water tank. The tube 88 'has a crescent form, cross-sectional configuration, as shown in FIG. 2, and is provided with a circular flange 90 at its inner open end, which flange lies flat against the square bottom 78 of bore 80 and fits the bore 80. The tube 88 is preferably constructed of copper, and

is thin walled, and is aligned with the crescent-shaped passage 82 extending through the base portion boss 72. The flange 90 is provided with a circular perforation 92, see FIG. 2, which receives the reduced diameter threaded portion 84 of tube 85, and the flange 90 is clamped against the bottom 78 of bore 76 by the shoulder for-med on tube 85 by the reduced diameter portion 84.

Positioned in the tube 88 near its outer closed end is a normally closed temperature responsive switch generally indicated at 94. Referring to FIGS. 4 and 5, the switch 94 comprises a flat base member 95 of dielectric material. A first long, fiat strip conductor 98 is attached at -a point near its outer end to base member 95 by a solid rivet 96 and is further attached to base member 95 at a point yet nearer its outer end by a hollow rivet 97. A second, long, flat co-extending strip conductor 99 having its outer end portion overlying conductor 98 and separated therefrom by an insulating strip 100 is attached to the base near its outer end by the solid rivet 96 only. The conductor strip 98 carries a stationary contact 102 at its extreme outer end, and conductor strip 99 carries a movable contact 104 at its extreme outer end which cooperates with stationary contact 102. The outer free end portion of conductor strip 99 is flexible and has a free form which normally spaces the movable contact 104 from contact 102 in open circuit position. However, a thin, circular, concavo-convex, bimetal disc 106, with its concave side facing the base member, overlies the end portion of conductor strip 99 and with a portion of its peripheral edge engaging the outer end of conductor strip 99 presses movable contact 104 against stationary contact 102 in closed circuit position under normal water temperature conditions. When the bimetal disc 106 is heated by the ambient water to a predetermined temperature, it snaps through a planar shape to an opposite concave-convex form and permits the free end portion of conductor strip 99 to assume its free form and separate the movable contact 104 from stationary contact 102.

The hollow rivet 97 is internally threaded and the bimetal disc 106 is centrally perforated and receives an adjustment screw 108 threadedly engaged in hollow rivet 97. The screw 108 has a head 110 at one end thereof bearing against the convex side of bimetal disc 106 and a screw driver slot at its other end. As the adjusting screw 108 is turned inward so as to increase the pressure on the convex side of bimetal disc 106, the temperature setting at which the disc will snap over center is reduced.

The conductor strips 98 and 99 co-extend inwardly from switch 94 in spaced relationship through tube 88 and into crescent-shaped passage 82 in boss 72. The inner ends of conductor strips 98 and 99 are fixed in spaced relationship in passage 82 by a mass of relatively rigid dielectric material which is preferably a synthetic thermoplastic or thermosetting material. The conductor strip 98 is connected at its inner end, as by soldering, to an insulated lead 112 which extends from boss 72 to the electromagnetic cutoif valve device 34, and the inner end portion of conductor strip 99 lies against and is electrically grounded to the boss 72. The circular bore 76 in stud 72 is also at least partially filled with the material 110 which forms a liquid seal to prevent any passage of liquid from the water tank through hollow boss 72. It is to be understood that the flat conductor strips 98 and 99 are sufiiciently rigid to support the switch 94 in position in tube 88.

Referring to FIG. 3, the electromagnetic cutoff valve assembly comprises a cylindrical casing 114 which is connected at one end to a terminal plug 116. The other end of casing 114 slidably supports a valve stem 118 which extends exteriorly and interiorly of the casing. Valve stem 118 carries the valve 36 on its exteriorly projecting end and an armature on its interior end. The terminal plug 116 has a threaded bore 117 and a smaller through bore 121 resulting in an internal shoulder 119. The terminal plug 116 is also provided with an enlarged diameter, threaded, flange portion which is threadedly engaged in the threaded entrance portion 122 of cylindrical bore 28. The casing 114 houses a U-shaped magnet core 124 having a winding 126 surrounding its parallel leg portions 128. A conductive rivet 132 extends through a bore in the leg connecting portion of the magnet core and-through the bore 121 in terminal plug 116 and rigidly connects the core to the terminal plug mechanically. The inner end of conductive rivet 13-2 is connected to one end of winding 26 at 131. A circular, molded, dielectric member 134 is interposed between the casing 114 and terminal plug 116, and the member 134 includes encased therein a conductor 136 having one end extending into casing 114 and being connected to the other end of winding 126 and having its other end extending exteriorly of body member 10 and being connected to lead 112.

A thermocouple junction encased in casing 138 is disposed with relation to pilot burner 43 so as to be impinged by the flame thereof. Coaxial tube and

wire conductors

140 and 141, respectively, lead from the thermocouple junction to terminal plug 116. The end portions of tube and

wire conductors

140 and 141 pass through a hollow nut 143 which is threadedly engaged in the threaded bore 117. The tube conductor 140 has a flared end which bears against the end of nut 143, and the wire conductor 141 has an enlarged diameter contact element 142 at its end which bears against the inner end of conductive rivet 132. An insulating washer is interposed between the fiared end of conductor tube 140 and the contact element 142. Dielectric grommets insulate the conductive rivet 132 from the terminal plug 116 and the portion 130 of the magnet core.

The thermocouple electromagnet circuit may be traced from the end of a strip conductor 99 grounded to metal cover 14 through the conductor 99, through normally closed

switch contacts

104 and 102, through strip conductor 98, lead 112 and conductor 136 to one end of winding 126, through winding 126, rivet 132, and wire conductor 141 to the thermocouple junction in casing 138, and from the thermocouple junction through tube conductor 140 to hollow nut 143, and terminal plug 116 which is grounded to cover member 14.

Operation When it is desired to start burner operation, the plug valve 30 is rotated to a pilot position which will permit fuel to flow from the hollow portion of plug valve 30 to the pilot burner 43 through the circumferentially slotted port 38, but will not permit flow through circular port 42 to chamber 22. The knob 17 is then pushed inward to open cutoff valve 36 and to move armature 15 into contact with the ends of magnet core legs 128. The pilot burner is then ignited by any suitable means and the knob 17 is held inward until electrical energy is generated at the thermocouple junction and is sufficient to energize winding 126 and hold the armature 15 against core 124 and the cutoff valve 36 open. Thereafter, the plug cock 30 is rotated to an on position in which fuel flows through port 42 to chamber 22 as well as through slotted port 38 to the pilot burner.

If the water temperature as sensed by the tube 85 of the rod and tube thermostat is less than that selected by the positioning of knob 70, the tube will be in such contracted position as to cause rod 86, through lever 64 and member 60, to open main valve 46. Fuel will thereby be permitted to flow to the main burner outlet 24 and to a main burner (not shown) where it is ignited by the pilot burner. When the water reaches the selected temperature due to operation of the main burner lengthwise expansion of tube 85 will cause the withdrawal of rod 86 and permit disc element 54 to return to its normal free position, as shown, and will permit valve 46 to close under the bias of spring 50. Under normal conditions, the main valve 46 will now be operated between open and closed positions to supply fuel to the main burner as required to maintain a selected Water temperature.

If, however, for any reason, the temperature of the water in the water tank exceeds that which has been predetermined as a safe upper limit, the bimetal disc 106 will warp and snap to an opposite concavo-convex form than shown in FIG. 5, and

contacts

102 and 104 will ,separate, thereby breaking the thermocouple electromagnet circuit. As a result the winding 126 will be deenergized and spring 13 will return cutoff valve 36 to a closed position, thereby cutting off the flow of fuel to both pilot and main burners.

The foregoing description is intended to be illustrative and not limiting, the scope of the invention being set forth in the appended claims.

I claim:

1. In a device of the kind described having a valve body, an externally threaded mounting boss projecting from said body, a main valve in said body, a rod and tube type thermostat operatively connected to said main valve, a biased closed cutoff valve in said body, electromagnetic means which when energized holds said cutoff valve open, and a circuit including an electrical power source for energizing said electromagnetic means; the improvement which consists in providing said mounting boss with a relatively large longitudinal bore extending inwardly from its outer end and terminating in a flat bottom and in providing two relatively small longitudinal passages extending inwardly from said bore bottom to the interior of said valve body, one of which passages is internally threaded; in providing a relatively thin-walled encapsulating tube of good heat conductive material having a closed end, an open end, and a circular off-center flange at its open end, which flange fits said relatively large bore, is entered into said bore, and lies flat against said bore bottom, and said tube being aligned with the other of said relatively small passages and extending outwardly from said mounting boss, said off-center flange having a perforation therein aligned with said one relatively small passage; in providing the tube of the rod and tube thermostat with a reduced diameter, externally threaded, inner end portion passing through said flange perforation in fitting relationship and being threadedly engaged in said one relatively small passage, thereby clamping said flange against said bore bottom; in providing a normally closed thermostatic switch responsive to open at a relatively high temperature and in supporting said switch with its thermostatic actuator in said encapsulated tube near the outer closed end thereof; and in providing circuit connections connecting said thermostatic switch in series with said electromagnetic means and said power source in said energizing circuit.

2. A device as set forth in claim 1 in which said encapsulating tube has a generally crescent form, crosssectional configuration with its major arcuate walls having their centers of curvature substantially on the axis of said rod and tube thermostat.

3. A device as set forth in claim 1 in which said circuit connections include a pair of spaced conductors coextending longitudinally in said encapsulating tube and being attached at their outer ends to said thermostatic switch and at their inner ends to said valve body and being of sufiicient rigidity to support said thermostatic switch in a fixed position in the outer end of said encapsulating tube.

4. A device as set forth in claim 3 in which the inner ends of said conductors extend into said other relatively small passage in spaced relationship, in which said other relatively small passage is substantially filled with a relatively rigid dielectric cementing material, thereby to support the inner ends of said conductors and to seal said passage, and in which said relatively large circular bore is at least partially filled with a fluid-sealing cementing material.

References Cited UNITED STATES PATENTS 3,291,390 12/1966 Solomon 236-21 3,320,388 5/1967 Kreuter 200-437 EDWARD 1. MICHAEL, Primary Examiner.

Claims

1. IN A DEVICE OF THE KIND DESCRIBED HAVING A VALVE BODY, AN EXTERNALLY THREADED MOUNTING BOSS PROJECTING FROM SAID BODY, A MAIN VALVE IN SAID BODY, A ROD AND TUBE TYPE THERMOSTAT OPERATIVELY CONNECTED TO SAID MAIN VALVE, A BIASED CLOSED CUTOFF VALVE IN SAID BODY, ELECTROMAGNETIC MEANS WHICH WHEN ENERGIZED HOLDS SAID CUTOFF VALVE OPEN, AND A CIRCUIT INCLUDING AN ELECTRICAL POWER SOURCE FOR ENERGIZING SAID ELECTROMAGNETIC MEANS; THE IMPROVEMENT WHICH CONSISTS IN PROVIDING SAID MOUNTING BOSS WITH A RELATIVELY LARGE LONGITUDINAL BORE EXTENDING INWARDLY FROM ITS OUTER END AND TERMINATING IN A FLAT BOTTOM AND IN PROVIDING TWO RELATIVELY SMALL LONGITUDINAL PASSAGES EXTENDING INWARDLY FROM SAID BORE BOTTOM TO THE INTERIOR OF SAID VALVE BODY, ONE OF WHICH PASSAGES IS INTERNALLY THREADED; IN PROVIDING A RELATIVELY THIN-WALLED ENCAPSULATING TUBE OF GOOD HEAT CONDUCTIVE MATERIAL HAVING A CLOSED END, AN OPEN END, AND A CIRCULAR OFF-CENTER FLANGE AT ITS OPEN END, WHICH FLANGE FITS SAID RELATIVELY LARGE BORE, IS ENTERED INTO SAID BORE, AND LIES FLAT AGAINST SAID BORE BOTTOM, AND SAID TUBE BEING ALIGNED WITH THE OTHER OF SAID RELATIVELY SMALL PASSAGES AND EXTENDING OUTWARDLY FROM SAID MOUNTING BOSS, SAID OFF-CENTER FLANGE HAVING A PERFORATION THEREIN ALIGNED WITH SAID ONE RELATIVELY SMALL PASSAGE; IN PROVIDING THE TUBE OF THE ROD AND TUBE THERMOSTAT WITH A REDUCED DIAMETER, EXTERNALLY THREADED, INNER END PORTION PASSING THROUGH SAID FLANGE PERFORATION IN FITTING RELATIONSHIP AND BEING THREADEDLY ENGAGED IN SAID ONE RELATIVELY SMALL PASSAGE, THEREBY CLAMPING SAID FLANGE AGAINST SAID BORE BOTTOM; IN PROVIDING A NORMALLY CLOSED THERMOSTATIC SWITCH RESPONSIVE TO OPEN AT A RELATIVELY HIGH TEMPERATURE AND IN SUPPORTING SAID SWITCH WITH ITS THERMOSTATIC ACTUATOR IN SAID ENCAPSULATED TUBE NEAR THE OUTER CLOSED END THEREOF; AND IN PROVIDING CIRCUIT CONNECTIONS CONNECTING SAID THEREMOSTATIC SWITCH IN SERIES WITH SAID ELECTROMAGNETIC MEANS AND SAID POWER SOURCE IN SAID ENERGIZING CIRCUIT.