US2585477A - Thermostatic control for hotwater heaters and the like - Google Patents

Description

Feb. 12, 1952 J. H. LESLIE, IL, ET AL 2,585,

THERMOSTATIC CONTROL FOR HOT-WATER HEATERS AND THE LIKE! Filed Dec. 22, 1945 5 Sheets-Sheet l Feb- 12, 19 2 J. H. LESLIE, 11., ETAL 2,5

THERMOSTATIC CONTROL FOR HOT-WATER HEATERS AND THE-LIKE Filed Dec. 22, 1945 5 Sheets-Sheet 2 F b. 12, 1952 J. H. LESLIE, IL, ETAL THERMOSTATIC CONTROL FOR HOT-WATER HEATERS AND THE LIKE Filed Dec. 22, 1945 5 Sheets-Sheet 3 Patented Feb. 12, 1952 THERMOSTATIC CONTROL FOR HOT- WATER HEATERS AND THE LIKE John H. Leslie, 11, and William A. Marshall, .Ir.,

assignorsto Stewart- Warner Corporation, Chicago, 111., a corpora- Indianapolis, Ind.,

tion of Virginia Application December 22, 1945, Serial No. 636,743

1 Claim. 1

The present invention relates to water heaters and more specifically to a type of small liquidfrom a conventional hot water heater located within the drivers compartment of an automobile, it will be appreciated thatthe invention relates more generally to hot water-heaters and also to similar heaters intended for heating liquids other than water.

Ordinary hot water heaters used in automobiles comprise a heat exchanger which receives hot water from the engine cylinder block on the inlet side and which discharges the water from the heat exchanger back to the cylinder block. Water heated by the engine is therefore passed through the heat exchanger and a portion of the heat is removed therefrom by an electric fan which passes air to be heated through the heat exchanger. One disadvantage of such a heating system is that no heating effect is produced until the water in the engine cooling system rises some substantial amount.

The heater of the present invention is inserted in the hot water line which leads from the engine block to the hot water heater of conventional design in such manner that all of the water passing from the engine to the conventional hot water heater must pass through the device of the present invention. The present device has a combustion chamber in which gasoline is burned at a comparatively high rate so that heat can be transferred to water passing through the device of the present invention at a rate of approximately 50,000 B. t. u. an hour. It is apparent, therefore, that water passing to the conventional hot water heater is raised to a substantial temperature within a matter of a few seconds after the device of the present invention is started.

It 'is the principal object of the present invention to provide an improved hot water heater of the above type which has a novel control system for the regulation of the flow of fuel to the heater.

An additional object of the present invention is to provide a novel hot water heater control which is operative to shut off the flow of fuel to the heater whenever the water in the heater jacket rises to some predetermined level, and which also acts as a safety device to turn oil ill the heater in the event that water is not present in the heater jacket in suilicient quantity for safe operation.

A further object of the present invention is to provide a novel hot water heater having an improved control system which can be supplied at comparatively low cost, is safe and sure in operation and requires substantially no maintenance in service.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention which is illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer to similar parts throughout the several views:

Figure l is a top view of a hot water heater embodying the present invention with a portion of the liquid connection broken away to Show interior structure;

Fig. 2. is a longitudinal sectional view of the heater illustrated in Fig. 1 and may be considered as taken substantially along the line 22 of Fig. 1 in the direction indicated by the arrows;

Fig. 3 is an irregular transverse sectional view which may be considered as taken substantially along the line 3-3 in the direction indicated by the arrows of Fig.2; and

Fig. 4 is an electrical circuit diagram illustrating the control circuit for the heater illustrated in the foregoing figures.

The heater indicated generally by the numeral I0 comprises a conical combustion chamber I 2 located within a cylindrical inner shell I with the large end of the burner toward one end of the shell while the smaller end thereof empties into the generally cylindrical space. The shell 14 togther with a concentric larger sleeve I6 forms an inner water jacket [8 which is closed at its ends by means of annular flanged rings 20 and 22 soldered or brazed to the cylindrical sleeves l4 and [6. This inner water jacket I8 is surrounded by an outer water jacket 24 spaced therefrom and comprised of a pair of generally cylindrical concentric spaced sleeves 2G and 28 At the bottom of the heater the inner of these sleeves 2B is formed to provide a depressed area 30 which is brought into contact with the sleeve 16, this depressed area being punched to provide a circular opening through which a portion of the metal of the sleeve I6 is extruded and rolled over to form a circular seam 32 around an opening which provides communication between the outer water jacket 24 and the inner water jacket 3 II. To prevent leakage. this scam is soldered. At the bottom of the heater this opening or passage is indicated by the numeral 34 while at the top 01' the heater a similarly formed passage is indicated by the numeral 38.

At the end of the heater opposite the burner I2, the outer water jacket is extended to form a reentrant portion by means of inner and outer cones 38 and 40, respectively. As will be seen in Fig. 2, the inner cone 38 is rolled over near its outer edge to provide a cylindrical portion 42 which is soldered to the end of the sleeve 28. Similarly, the outer cone 40 is rolled over and soldered to the end of the outer shell 28. In order to space the cones 38 and 40 a proper distance apart to provide a water jacket, these cones near their centers are provided with mutually abutting extrusions 44 and 48 which prevent the cones from approaching each other more than a predetermined distance. Similarly, extrusions 48 are provided in the outer shell 28 so as to space this shell from the next adjacent shell 26.

At the burner end of the heater, a flanged ring 9 acts as a cap to provide a closure for the end of the outer water jacket space 24 while a stepped cup closes the space between the shell 28 and a cylindrical bailie 52 which acts to prevent products of combustion from flowing directly from the burner to the exhaust connection. The central portion of the cup 50 also acts as the closure for the back of the burner I2.

Near the bottom of the burner I2 the closure cup 50 is provided with a pocket 54 into which liquid fuel flows by way of a tube 56 and fitting 58. This pocket also is equipped to receive an igniter 60 of the hot wire type energized through an igniter wire 62. The igniter when energized acts to vaporize gasoline or other liquid fuel in the pocket 54 and subsequently ignites the combustible vapor to start the fire in the combustion chamber I2. After the fire has been started, the igniter may be de-energized. Air for combustion is introduced through a tube 84 which enters the combustion chamber tangentially at the top thereof. The opposite end of this tube extends through baflie 52 and the heater shells 26 and 28 and outside the heater case is bent at right angles and is connected to the outlet of a centrifugal blower '68. This blower is driven by a small electric motor 88 which is secured to the heater case by means of a suitable bracket I0.

When the burner is operating, products of combustion flow from the burner I2 into the cylindrical space adjacent thereto and heat the inner sleeve I4. Heat is therefore transferred to the water within the jacket IS. The hot products of combustion also flow against the conical surface 38 and heat the water jacketed between this cone and the outer cone 40. After transferring a considerable portion of heat to the water as above indicated, the products of combustion flow around the end of the ring and between the shells I6 and 26, thereby transferring more heat to the water within the jacket I8 and to the water within the outer jacket 24. At the burner end of the heater the products of combustion are collected within the annular plenum chamber 12 and pass outwardly through an exhaust spud I4 which communicates with the plenum chamber I2 through an opening I6 in the shells 28 and 28, this opening being sealed against water leakage in the same manner as the openings 34 and 36.

Water is introduced into the outer jacket space 24 by means of a tubular fitting I8 rolled over the edge of an opening in the shell 28, the fitting then being soldered in place to insure against leakage. Water flowing into the heater, therefore, directly enters the outer jacket 24 and passes into the jacket I8 by way of the opening 38. At the top of the heater the outer water jacket 24 is provided with an outlet opening directly opposite the passage 38 which communicates between the inner and outer jackets. The metal around the opening 80 is extruded outwardly and rolled over to form a connection with an elbow fitting 82, the joint being sealed with solder to prevent leakage. Elbow fitting 82 is connected at its outlet by means of a rubber sleeve 84 with an adapter 88 which in turn is connected to a rubber hose 88 which carries the hot water away from the heater. In a conventional installation the hose 88 will be connected to a conventional hot water heater located within the driver's compartment. In order to control the flow of liquid through the system, the hose connection 84 contains a liquid thermostat 90 which may be of conventional type and which opens at a predetermined temperature, as an example, degrees R, so as to permit water to flow through the system as long as the water temperature is above this predetermined level and to inhibit flow through the system until this level has been reached.

The top of the elbow fitting 82 in a position directly opposite the passages 80 and 36 is provided with a threaded boss 92 to receive the head 94 of a thermostatic bulb 96 which is connected by means of a capillary tube 98 with a pressure responsive control switch I00. Whenever,-with this system, the temperature of the bulb 98 rises, the vapor pressure therein will rise, thus raising the pressure in the tube 98 and in the pressure responsive switch I00. The bulb 98 contains a quantity of fluid with proper vapor pressure characteristics to operate within the temperature range desired. Preferably air is exhausted from the bulb 98 before it is sealed and the liquid filling is so chosen that throughout the temperature range the pressure within the bulb is subatmospheric. As the temperature rises, the vapor pressure of the liquid increases and operates the switch I00 at a, higher but still subatmospheric pressure. For the purpose of controlling a heater of the type indicated, we have found that ethyl alcohol has good vapor pressure characteristics and is satisfactory for use in the control bulb 96 and associated mechanism although other liquids may be used if desired.

Inasmuch as the specific switch I00 forms the subject matter of a separate application, no further description need be given as to the details of its construction. For the present purpose, it is sufficient to indicate that the tube 98 is connected to a bellows I02 which forms a portion of the switch mechanism I00 and this bellows upon being elongated operates in sequence three separate switches I04, I08 and I08.

As indicated in Fig. 4, all three of these switches are closed at ambient temperature and are so arranged that as the bellows I02 elongates switch I04 opens at a comparatively low temperature and disconnects the igniter 60 from the automobile battery IIO, the battery being connected to the switches I04, I06 and I08 by way of a main heater switch II2. At a higher temperature, switch I06 is opened, thereby de-energizing an electromagnetic restricting valve II4 located in the fuel line 56 leading to the heater I0. Valve H4 is of the type which permits a full flow of fuel therethrough when energized, but which permits a low rate of flow when de-energized.

Closure of this valve, therefore, acts to shift the heater from high heat operation to low heat operation.

At a still higher temperature the switch I08 is opened, thereby de-energizing a second magnetic valve II6 which is'of the on-oil type. The de-energization of this valve, therefore, interrupts the flow of fuel from the fuel pump II8 to the heater I0, thereby turning off the heater. Under normal operating conditions it is desirable to shift the heater from high heat operation to low heat operation as the temperature of the water rises slightly above that at which the liquid thermostat 90 opens. When the water temperature rises somewhat thereabove, the heater is turned oil, since such temperature conditions of the water indicate that the engine is supplying enough heat so that it alone can maintain a comfortable level within the driver's compartment. Because of the possibility that the heater may be started without suflicient water being present in the water jackets, it is desirable to have some type of safety device for turning off the heater in the event that the jacket metal temperatures exceed some predetermined level. In order to accomplish this objective, the bulb 96 of the thermostat is slipped longitudinally into a deep drawn cup I in such manner that good metal to metal contact is obtained between the cup I20 and the bulb 96. This may be accomplished by slotting the cup I20 longitudinally and then providing a clamping band I22 which is tightened after the bulb is in place so as to squeeze the side walls of the cup against the surface of the bulb. Preferably the cup I20 should be formed of a metal having high thermal conductivity, such as brass or copper, for instance, and the lower end of the cup is welded or brazed or otherwise suitably attached, as indicated at I24, to the surface of the inner shell I4. The cup I20 is also provided with a plurality of perforations I26 in the side walls thereof in a position beneath the end of the bulb 96 and above the point of attachment of the cup I20 to the inner shell I4. These perforations permit water from the Jacket to enter the space within the cup I20 below the bulb 96.

We have found that with a device constructed as above indicated the liquid within the water jacket will circulate through the openings I20 and into the space beneath the bulb 96 and will flow in contact with the portion of the bulb above the cup I20. It will act, therefore, to transfer heat away from the cup I20 in such manner that the temperature of the bulb 96 will always be at substantially the water temperature, so long as water is present within the jacket. On the other hand, if the heater is operating and water is absent from the jacket, heat will be conducted from the shell I4 to the cup I20 and up the side wall of the cup to the bulb 96 so as quickly to raise the temperature of the bulb. The result is that whenever the inner shell I4 is excessively heated because of the absence of water from the system, this dangerous condition will quickly result in heat being conducted to the temperature responsive bulb 96 so as to raise the temperature of the liquid therein sufflciently to elevate the vapor pressure to the point where the bellows I02 expands and opens all three of the switches I04, I 08 and I06, thereby turning oil the heater. It is apparent, therefore, that by the simple expedient of arranging the bulb 96 in good heat conducting relation with the tube I 20 and by connecting this tube to the inner shell I4 and further by forming the tube or cup I20 of a metal having a high rate of thermal conductivity, the bulb l8 and control switch associated therewith act in a normal manner to sense the water temperature when water is present in the system and also serve to sense the metal temperature, so as quickly to shut off the heater in the event that combustion is started without sufllcient water being present in the system.

Inasmuch as the liquid filling for the bulb is so chosen that its vapor pressure is below atmospheric at normal control temperatures, thereby permitting all three of the switches I04, I06 and I09 to be opened before the pressure within the bulb 96, tube 98 and bellows I02 reaches atmospheric, the system is inherently safe, or as it is commonly expressed "fails safe. In other words, if any portion of the vapor system should 'leak, the subatmospheric .pressure therein will cause air to leak into the system, thereby permitting the bellows I02 to elongate so as to turn off the heater. The heater, of course, remains off until the defect has been repaired.

From the above it will be seen that by a simple mechanical expedient which adds very little to the cost of the heater, we have caused the water temperature control system to do double duty by also serving as a safety control to turn 01! the heater in the event that it is started without sufficient water being present in the Jackets.

Having described our invention, what we claim as new and useful and desire to secure by Letters Patent of the United States is:

In the combination which includes a water heater or the like having a metal surface heated on one side and cooled on the other side by water to be heated and a thermally responsive element immersed in water for regulating the heater according to the water temperature, the improvement in the thermally responsive element which comprises a thermostatic bulb, a generally tubular metallic element of relatively high thermal conductivity to support said bulb in the upper region of the water space in said heater in spaced relation to said surface, said bulb being telescopically received in and closely embraced by one end of said tubular element and the opposite end of the latter being secured directly to said surface to form a metallic heat conducting path for rapidly conducting heat from said surface to said bulb whenever the level of the water falls below said opposite end, the wall of said tubular element having openings therethrough between said bulb and said opposite end to afford free passage of water between the inside and outside of said tubular element.

JOHN H. LEsLm, Ir.

WILLIAM A. Jn.

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

UNITED STATES PATENTS Date

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