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 [Search a list of Patent Appplications for class 122]   CLASS 122,LIQUID HEATERS AND VAPORIZERS
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SECTION I - CLASS DEFINITION

This class relates to heating liquids, generating vapors from liquids, treating the vapors generated for use, such as superheating or cooling them, and conserving the heat remaining in the liquid or vapor after a part of the heat energy has been made use of for any purpose. To bring a liquid heater into this class, the chamber, receptacle or conduit in which the liquid is heated must be fluid tight.

This class includes combinations of steam superheaters, feed-water heaters, steam separators, condensers, traps, manhole-closures, safety devices, cleaners, and feeders with a boiler when the structure of necessity must form a part of the boiler structure combination, also parts of boilers unless they are of general application.

This class includes water-cooled grates whether or not in connection with a boiler for heating the boiler water. It also includes the boiler and furnace in combination or the boiler alone with the furnace alone.

The liquid containers classified in this class may be heated by solid or fluid fuel burned in any type of furnace or burner, by friction, or by chemical action other than combustion, or by electricity. The heat may be applied directly to the walls of the fluid containing chamber or indirectly by the interposition of a fluid in a distinct and separate chamber, which fluid being heated may impart its heat to the fluid to be finally heated. When the fluid is heated by the interposition of another fluid the heat generator must be a part of the unitary structure of the fluid heater, with one exception--to wit: devices for generating a vapor having a vapor separator within the fluid chamber may be heated indirectly by a fluid, the furnace for heating which does not form part of the unitary structure. The fluid may be heated also by a heat radiating body in either a liquid, or solid state, which body may be either on the inside or on the outside of the fluid chamber; but if said heating body be inside the fluid chamber its nature must be such that it will not mix with the fluid to be heated.

SECTION II - LINES WITH OTHER CLASSES AND WITHIN THIS CLASS

The distinction between water heaters in Classes 122 and 126 is this: The water heaters in Class 122 have a closed water containing chamber or receptacle for holding the water while it is heated or have one or more closed conduits through which the water flows while being heated; but the water heaters in class 126 are of the open type. In Class 122 are classified mechanism for regulating both the inflow of water to the boiler and the burning of the fuel in all cases when steam is generated and also in all cases when water is heated, excepting in devices for heating water where the opening of a valve to permit water to flow through the heater at the same time increases the heat of the heat generator, such devices being classified in Class 126, subclasses 351; but this subclass relates only to the controlling device for the water and fuel. The structure of the water heater or boiler together with such a controlling mechanism are classified in Class 122.

SECTION III - REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:

15Brushing, Scrubbing, and General Cleaning,   subclass 104.03 for pipe and tube cleaners generally 314, 316.1+ and 406+ for pipe and tube cleaners and boiler tube blowers using air or steam blast and/or suction.
29Metal Working,   subclass 890.051 for a method of making a boiler or subclass 890.07 for a method of making a condenser, evaporator, or vaporizer.
60Power Plants,   where combustion products are used as a motive fluid, subclasses 39.53 through 39.59including addition of steam or water, or subclass 775 including introducing water or steam; or subclasses 641.1-641.15 using natural heat (e.g., sun, air, water, earth, etc.).
68Textiles: Fluid Treating Apparatus,   having significant structure for fluid treatment of a textile, subclass 15 for a textile fluid treating machine combined with a tank heater, or subclass 222 for an implement to apply steam to a textile.
73Measuring and Testing,   subclasses 215+ for weir maters combined with feed water heater structures.
99Foods and Beverages: Apparatus,   subclasses 276 , 277, and 359+ for beverages and food cookers using liquid heaters pertinent to this class; and subclasses 468+ for treatment of dairy food which includes milk treating apparatus using liquid heaters.
116Signals and Indicators,   for signals.
126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclass 5 for a cooking and heating stove having a water heater or steam generator; subclasses 20-20.2 for a cooking oven heated by steam or hot water; subclass 31 for a cooking stove having a water heater in a flue extension; subclasses 34 and 35 for a cooking stove having a water back; subclass 101 for a hot air furnace combined with a boiler; subclasses 344-363.1 for a liquid heater that may include a kettle, a steam generator, stove pipe for use with a stove, and a domestic water heater or boiler (e.g., kitchen boiler, range boiler, etc.) for use with a stove or furnace; subclasses 513 and 514 for a fireplace with a liquid heater; subclasses 561-568 for a solar heat collector for a pond or pool; subclasses 569-713 for a solar heat collector that may include a fluid medium; or subclass 714 for a process of heating by using solar heat.
137Fluid Handling,   subclass 11 for processes for regulating the boiler water level, subclass 94 for the control of the fuel in response to boiler or water heater condition subclasses 156+ for gas pressure discharge of liquid as to a boiler, subclasses 171+ for steam traps, subclasses 386+ for level responsive valves, and subclasses 557 and 558 for pressure and level responsive signals and indicators.
138Pipes and Tubular Conduits,   appropriate subclasses for the wall structure of a boiler tube or flue; subclasses 89+ for plugs for pipes; and subclasses 98+ for patches for pipes.
165Heat Exchange,   appropriate subclass, for a heat exchanger, per se.
202Distillation: Apparatus,   subclasses 152+ for liquid volatilization for the purpose of recovering material from the vapor produced by condensation or absorption.
204Chemistry: Electrical and Wave Energy,   subclasses 196.01 through 196.38for electrolytic protection apparatus (e.g., to prevent corrosion, scale formation, or other objectionable action upon liquid heaters or vaporizers, etc.).
205Electrolysis: Processes, Compositions Used Therein, and Methods of Preparing the Compositions,   subclasses 724 through 740for processes of electrolytic protection of metal objects (e.g., to prevent corrosion, scale formation, or other objectionable action upon liquid heaters or vaporizers, etc.).
210Liquid Purification or Separation,   subclasses 175+ for a heater or heat exchanger combined with liquid purification means.
219Electric Heating,   subclasses 281+ for water heaters and steam generators particularly adapted to be heated by an electric heater.
220Receptacles,   appropriate subclasses, for wall structures of containers of more general utility and for safety devices and for manhole covers.
237Heating Systems,   for an apparatus or process of heating an enclosure, subclass 7 for a combined radiator and boiler having automatic control, or subclasses 16-18 for a combined boiler and radiator.
264Plastic and Nonmetallic Article Shaping or Treating: Processes,   subclass 30 for furnace lining formation or repair and see the notes thereto.
411Expanded, Threaded, Driven, Headed, Tool-Deformed, or Locked-Threaded Fastener,   subclass 367 for a threaded fastener and nut having stay bolt spacer sleeve; subclass 370 for a threaded fastener and nut having a stay bolt bearing washer; subclasses 379+ for a threaded stay bolt, per se; and subclass 505 for an unthreaded stay bolt, per se.
417Pumps,   subclasses 36+ for liquid level control of a pump drive motor, subclasses 108+ for aerated column type pumps wherein is elevated by alternate globules of water and steam and subclasses 118+ for pumping of liquid by supplying or exhausting of gaseous motive fluid to or from a pump chamber.
451Abrading,   for structural features of a cleaner for a tube or flue.
510Cleaning Compositions for Solid Surfaces, Auxiliary Compositions Therefor, or Processes of Preparing the Compositions,   subclasses 247+ for compositions for descaling steam boilers or other water containers.

SECTION IV - GLOSSARY

BOILER

Used as a generic term for a liquid heater. The nature of the liquid heated is immaterial. Whether the liquid heated is conducted from the boiler as liquid or vapor depends upon the amount supplied and the degree of heat attained, and for this reason generally no distinction has been noted in the classification, similar structures being classified together regardless of the ultimate effect. In the type of boilers known as "flashers" this distinction is of importance and provision has been made therefor.

FIRE TUBES

Include both small and large tubes through which the products of combustion pass unless the term "flue" is used with them, in which case "fire tubes" would refer to the small tubes, and "flues" to the large tubes for the products of combustion.

STEAM

To be taken in a generic sense as meaning vapor.

STEAM TUBES

Designate vapor tubes whether the vapor therein be formed from water or any other liquid.

WATER TUBES

Designate tubes, both large and small, through which liquid or vapor passes.

WATER

To be taken in a generic sense as meaning liquid.

SUBCLASSES

[List of Patents for class 122 subclass 1]    1PLANTS:
 This subclass is indented under the class definition.  Combinations of elements and devices each performing different functions for the conservation of the heat generated in the furnace, the ultimate object of which is the production of steam or the heating of water.

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21,for "alkali" steam generators.
448.1,449, 450, and 452, for regulating means.

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60Power Plants,   generally for devices peculiar to that class.
91Motors: Expansible Chamber Type,   for plants involving the steam engine structure.
123Internal-Combustion Engines,   subclasses 2+ for combinations of internal combustion motors and other engines and steam boilers.
237Heating Systems,   subclasses 12.1 and 13 for vehicle plant and heating systems.
418Rotary Expansible Chamber Devices,   for plants involving rotary expansible chamber structure.
  
[List of Patents for class 122 subclass 2]    2Garbage:
 This subclass is indented under subclass 1.  Plants for the destruction of garbage relating either to the arrangement of the boiler or the boiler structure adapted for this special purpose.

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232,and 376, for water grate structure adapted to burn garbage or other waste material.

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110Furnaces,   subclass 234 , for garbage plants with a conventional arrangement of a boiler therewith.
  
[List of Patents for class 122 subclass 3]    3Motor vehicle:
 This subclass is indented under subclass 1.  Boiler plants specially adapted for motor vehicles.

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446+,448.1, 449, and 452, for analogous structure.

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60Power Plants,   subclass 668 for a steam power system physically related to a vehicle.
180Motor Vehicles,   subclasses 36+ for a motor vehicle of the steam traction engine type; subclasses 303+ for a motor vehicle having a traction motor of the kind which is driven by expansible gas from a source external of the motor and wherein the gas is produced by treating a volatile fluid (e.g., the gas is steam); and subclass 310 for a motor vehicle having means to generate steam for a propulsion purpose.
  
[List of Patents for class 122 subclass 4]    4MISCELLANEOUS:
 This subclass is indented under the class definition.  Boilers and parts thereof not otherwise classifiable.
  
[List of Patents for class 122 subclass 5]    5GAS-PRODUCER:
 This subclass is indented under the class definition.  Subject matter relating to combinations of a gas producing furnace and boiler when the structure of the boiler is intimately associated with the producer, so as to form a unitary structure, the gas from the producer being burned to heat the boiler.

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6+,for boilers heated by gas passing through a boiler from a gas producer, the heat of the hot gas being used for heating the boiler.

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48Gas: Heating and Illuminating,   for gas making plants including a boiler.
110Furnaces,   subclass 229 for gas producer furnaces and see the notes therewith.
  
[List of Patents for class 122 subclass 5.51]    5.51AIR-INJECTED:
 This subclass is indented under the class definition.  Devices for vaporizing a liquid, with means for mingling air therewith in the vaporizer.
  
[List of Patents for class 122 subclass 5.52]    5.52Combustion gas and vapor contact:
 This subclass is indented under subclass 5.51.  Devices wherein the vapor is combined with the byproducts of burning fuels.
  
[List of Patents for class 122 subclass 6]    6INDUSTRIAL:
 This subclass is indented under the class definition.  Subject matter relating to boilers, water heaters, or cooling devices for furnace walls having a closed chamber or conduit combined with a conventional type of furnace employed in a special art.
(1) Note. If the cooling device is not a closed chamber or conduit, it will be classified in the type of furnace of the special art. Class 122 includes such devices known as bosh plates, water cooled walls and roofs, linings, and water cooled tuyeres when the cooling device is a closed chamber or conduit and there is otherwise no novelty in the invention.

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48Gas: Heating and Illuminating,   subclasses 63+ and 67, for gas producers using similar structure.
266Metallurgical Apparatus,   subclasses 190 and 241 for cooling features in devices of that class.
431Combustion,   subclass 160 for a furnace type combustion chamber having means directing nonliquid cooling medium across elements of a device dispersing fuel into a furnace.
432Heating,   subclasses 233+ for a residual material heating apparatus element having protective cooling structure.
  
[List of Patents for class 122 subclass 6.5]    6.5Port:
 This subclass is indented under subclass 6.  Subject matter comprising water circulation devices applied to the gas or air ports of a furnace.

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431Combustion,   subclass 160 for a fuel disperser installed in a combustion chamber cooled by a gas additional to the combustion materials.
432Heating,   subclass 173 for a specific furnace having a protective cooling means for combustion material feed structure.
  
[List of Patents for class 122 subclass 6.6]    6.6Tuyeres:
 This subclass is indented under subclass 6.  Subject matter comprising conduits for feeding air to furnaces and provided with a closed water-circulation.

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110Furnaces,   subclasses 182.5+ for tuyeres of general application and for other water circulation means therefor.
266Metallurgical Apparatus,   subclasses 265+ and especially 270 for tuyeres used in metallurgical apparatus which may include a liquid cooled tuyere element where the tuyere element is combined with additional structure, as for example, an external gas supply pipe, means for feeding diverse materials, flow control valves or a tuyere cooler, Further, see subclasses 186+ and 218+ for tuyeres combined with the treating vessel.
  
[List of Patents for class 122 subclass 6.7]    6.7Forge:
 This subclass is indented under subclass 6.6.  Devices with water circulation, of a type used in a forge and in which the direction of the air blast is usually vertical.

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110Furnaces,   subclass 182.6 for tuyeres in forge furnaces.
  
[List of Patents for class 122 subclass 7]    7Waste heat:
 This subclass is indented under subclass 6.  Devices comprising combinations of a conventional type of industrial furnace and a boiler located so as to be heated by the waste heat of the furnace.

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20,421 and 470, for analogous devices.

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432Heating,   subclasses 90+ for (1) a structure in which the waste heat of a nominal boiler heats a material heating chamber of the Class 432 type (2) a structure in which the waste heat of a specific furnace heats a closed water chamber or conduit or (3) for a residual combination of a liquid heater and a work heater of the Class 432 type in which the heated liquid is utilized in heating the work.
  
[List of Patents for class 122 subclass 8]    8Water firebox:
 This subclass is indented under subclass 6.  Industrial boilers having a water jacket firebox.
  
[List of Patents for class 122 subclass 9]    9Water tube type:
 This subclass is indented under subclass 8.  Industrial boilers including a firebox the walls of which are provided with water containing tubes.
  
[List of Patents for class 122 subclass 10]    10FOR FLUID FUEL BURNER:
 This subclass is indented under the class definition.  Boilers for generating steam for feeding a fluid fuel burner.

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431Combustion,   subclasses 207+ for a burner assembly including as an element a supply line in which burner feed; e.g., air, oil, or fuel atomizing water; is heated.
  
[List of Patents for class 122 subclass 11]    11ROTARY:
 This subclass is indented under the class definition.  Boilers in which a substantial part or the whole of the fluid-containing chamber is designed to be continuously-rotated while heating the water or generating steam.
  
[List of Patents for class 122 subclass 12]    12ROTATABLY SUPPORTED:
 This subclass is indented under the class definition.  Boilers that are supported in bearings so that the whole boiler or a substantial part thereof may be turned on an axis, generally either vertical or horizontal, after its connecting steam and water pipes have been uncoupled.
  
[List of Patents for class 122 subclass 13.01]    13.01STAND BOILER (E.G., WATER HEATER, ETC.):
 This subclass is indented under the class definition.  Subject matter comprising heating means applied directly or indirectly to the wall of the fluid containing chamber, where the fluid is water, to provide hot water for domestic or household use (e.g., cooking, cleaning, washing, bathing, space heating, etc.).
(1) Note. The stand boiler (e.g., water heater, etc.) may be found in other than a house or home (e.g., apartment building, office building, restaurant, laundry, recreational vehicle, etc.) to provide hot water for domestic or household use (e.g., cooking, cleaning, washing, bathing, space heating, etc.).

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20,for a subsidiary liquid heater consisting of a pipe, coil, hollow plate, or cylinder in a firebox, combustion chamber, or offtake flue of a furnace in a boiler to generate steam or hot liquid for other than the boiler.
233,for a horizontal disposed tank combined with a wall of a furnace.
234,for a vertically disposed tank combined with heating means.

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclasses 350.1 through 350.2for a fluid fuel burner other than a top-accessible liquid heating vessel.
220Receptacles,   subclass 567.3 for a stationary tank for a hot water heater or boiler.
392Electric Resistance Heating Devices,   subclasses 322 and 323 for an electrically conductive fluid (e.g., water, etc.) forming part of the circuit that heats the fluid including a reservoir or tank, or subclasses 449-464 for a line-connected tank- or container-type liquid heater.
  
[List of Patents for class 122 subclass 13.3]    13.3And delivery means to dispensing feature:
 This subclass is indented under subclass 13.01.  Subject matter and means to convey the hot water from the stand boiler to some end use such as a domestic fixture (e.g., faucet, shower, washing machine, dishwasher, etc.).

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclass 362.1 for a boiler receiving hot liquid or steam from a stove or furnace (e.g., kitchen boiler, range boiler, etc.) having liquid circulation means, or subclass 365.1 for a liquid heater and stovepipe having liquid circulation means.
237Heating Systems,   for an apparatus or process of heating an enclosure, subclass 7 for a combined radiator and boiler having automatic control or subclasses 16-18 for a combined boiler and radiator.
  
[List of Patents for class 122 subclass 14.1]    14.1And condition responsive feature:
 This subclass is indented under subclass 13.01.  Subject matter and means to sense a state or change in the state of the stand boiler or the water heated by the stand boiler to effect a change in the operation of the stand boiler or the heated water.

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448.1through 448.4, for automatic control of fluid fuel and feed water to a boiler.
504through 507, for a boiler safety device.

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclass 351.1 for a fluid fuel burner other than a top-accessible liquid heating vessel and a condition responsive feature or subclass 374.1 for an open-top liquid heating vessel that may include a lid and a condition responsive feature.
340Communications: Electrical,   subclasses 500 through 693.12for an electrical automatic condition responsive indicating system.
  
[List of Patents for class 122 subclass 14.2]    14.2Controls burner:
 This subclass is indented under subclass 14.1.  Subject matter wherein the condition responsive feature effects change in the burner.

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137Fluid Handling,   subclass 94 for a condition responsive system where fuel is proportioned or correlated to some boiler or water system condition.
  
[List of Patents for class 122 subclass 14.21]    14.21By other than temperature of water:
 This subclass is indented under subclass 14.2.  Subject matter wherein the condition responsive feature controls the burner by other than responding to the condition of the water having a degree of hotness or coldness measured on a definite scale.
(1) Note. This may also include a temperature condition responsive means for the liquid.
  
[List of Patents for class 122 subclass 14.22]    14.22By temperature of water in water containing chamber or external tank:
 This subclass is indented under subclass 14.2.  Subject matter wherein the condition responsive feature controls the burner by responding to the condition of the water having a degree of hotness or coldness measured on a definite scale stored in the water containing chamber or a closed receptacle outside of and for storing water heated by the stand boiler.

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374Thermal Measuring and Testing,   subclasses 100 through 207for a temperature measuring device (e.g., thermometer, etc.).
  
[List of Patents for class 122 subclass 14.3]    14.3Having water flow control feature:
 This subclass is indented under subclass 14.1.  Subject matter wherein the condition responsive feature includes means to effect direction of movement or quantity of the water.

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451.1,451.2, for a feed water heater having automatic control of the feed water flow by thermally responsive means.
456,457, for a feed water heater having a tank or receptacle that includes automatic control of inlet and outlet valves allowing the feed water to flow by gravity to the boiler.

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137Fluid Handling,   a residual class for process or apparatus, subclasses 87.01 through 87.06for a condition responsive system where fluid flow in a flow line is proportioned or correlated to some condition of a fluid flowing in another fluid flow line or subclasses 455-543.23 for a valve controlling a flow line responsive to a change in the condition of the fluid.
417Pumps,   subclasses 279 through 311for a pump having condition responsive control of the pumped fluid.
  
[List of Patents for class 122 subclass 14.31]    14.31Using valve actuated by flow or pressure (e.g., check valve, etc.):
 This subclass is indented under subclass 14.3.  Subject matter wherein the water flow control feature is an element having a definite predetermined motion to open, close, or partially obstruct a port or passageway and is moved into action by the movement, quantity, or force per unit area of the liquid.

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251Valves and Valve Actuation,   subclasses 12 through 63.6for a valve actuated or retarded by fluid acting on the actuating means.
  
[List of Patents for class 122 subclass 15.1]    15.1Heated by liquid or steam (e.g., indirect heating, etc.):
 This subclass is indented under subclass 13.01.  Subject matter wherein the stand boiler uses a hot fluid that is shapeless, virtually incompressible, has a definite volume (e.g., water, etc.) or a vapor emitted from such a fluid to transfer thermal energy to the water in the stand boiler.
(1) Note. This may include a burner for heating the liquid or steam that transfers the thermal energy to the liquid in the stand boiler.
(2) Note. The heating liquid or steam may have a pressure higher than the liquid in the stand boiler.

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32through 34, for a liquid indirectly heated by a separate heating fluid.
  
[List of Patents for class 122 subclass 16.1]    16.1Solid fuel burner:
 This subclass is indented under subclass 13.01.  Subject matter wherein the stand boiler is heated by the solid fuel burner.

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22,for a residual solid or liquid fueled boiler.
211,for a solid or liquid fueled sectional boiler.
368through 370, for a residual boiler having a water-jacketed firebox.

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110Furnaces,   a residual class for solid material combustion apparatus or a method of operating solid material combustion apparatus.
126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclasses 367.1 and 368.1 for a liquid heater having a solid fuel burner submerged underneath the surface of the liquid.
  
[List of Patents for class 122 subclass 17.1]    17.1Fluid fuel burner:
 This subclass is indented under subclass 13.01.  Stand boiler wherein the stand boiler is heated by the fluid fuel burner.

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23,for a residual boiler heated by fluid fuel.

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431Combustion,   for a residual process or apparatus of combustion or combustion starting.
  
[List of Patents for class 122 subclass 17.2]    17.2Liquid fuel burner:
 This subclass is indented under subclass 17.1.  Subject matter wherein the fluid fuel is shapeless, virtually incompressible, and has a definite volume.
  
[List of Patents for class 122 subclass 18.1]    18.1Having heat exchange feature:
 This subclass is indented under subclass 17.1.  Subject matter wherein the stand boiler includes means to transfer heat from the burned fuel directly or through the interposing fluid to the wall of the water containing chamber without allowing them to mix.

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclasses 376.1 through 391.1for an open-top liquid heating vessel that may include a lid having a heating fluid confining, directing, or shielding feature; or subclass 390.1 for an open-top liquid heating vessel that may include a lid having a heating wall structure.
165Heat Exchange,   for a residual heat transfer apparatus or process.
  
[List of Patents for class 122 subclass 18.2]    18.2Preheater:
 This subclass is indented under subclass 18.1.  Subject matter wherein the heat exchange feature is used to transfer heat, usually waste heat, to a fluid (e.g., air, liquid, water, etc.) before it is heated by the stand boiler.

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412through 444, for a feed water heater.

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431Combustion,   for a residual process or apparatus of combustion or combustion starting, subclasses 207 through 248for a heated fuel line section that feeds a burner.
  
[List of Patents for class 122 subclass 18.3]    18.3Fire tube or flue surrounded by water containing chamber:
 This subclass is indented under subclass 18.1.  Subject matter wherein the heat exchange feature consists of the fire tube or flue enclosed on all sides by the water containing chamber.

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44.1through 45, for a residual boiler having a fire tube.
135.1through 156, for a boiler having a large fire tube or flue wholly or partly surrounded by the water space.
  
[List of Patents for class 122 subclass 18.31]    18.31Penetrates one side of water chamber to another:
 This subclass is indented under subclass 18.3.  Subject matter wherein the fire tube or flue passes through a wall of the water chamber to an opposing wall.
  
[List of Patents for class 122 subclass 18.4]    18.4Water tube surrounded by burned fuel:
 This subclass is indented under subclass 18.1.  Subject matter wherein the heat exchange feature consists of the water tube enclosed on all sides by the burned fuel.

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235.11through 365, for a boiler having a water tube through which the water circulates or passes while being heated.
  
[List of Patents for class 122 subclass 18.5]    18.5And external water tank:
 This subclass is indented under subclass 17.1.  Subject matter and a closed receptacle outside of and for storing water heated by the stand boiler.

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19.2,for a stand boiler (e.g., water heater, etc.) that provides hot water for domestic or household use (e.g., cooking, cleaning, washing, bathing, space heating, etc.) that may be in other than a house or home (e.g., apartment building, office building, restaurant, laundry, recreational vehicle, etc.) and a casing for the stand boiler or an external tank therefor.

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclasses 361.1 through 363.1for a boiler receiving hot liquid or steam from a stove or furnace (e.g., kitchen boiler, range boiler, etc.).
  
[List of Patents for class 122 subclass 19.1]    19.1Water containing chamber or external tank having circulation feature within:
 This subclass is indented under subclass 13.01.  Subject matter wherein the water containing chamber or a closed receptacle outside of and for storing water heated by the stand boiler having means inside to direct the movement or development of the water.
(1) Note. This may include means to create (e.g., inlet, outlet, mixer, etc.) or prevent (e.g., baffle, dampener, diffuser, etc.) circulation within the water chamber.

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclass 362.1 for a boiler receiving hot liquid or steam from a stove or furnace (e.g., kitchen boiler, range boiler, etc.) having liquid circulation means or subclass 365.1 for a liquid heating stovepipe having liquid circulation means.
392Electric Resistance Heating Devices,   subclass 452 for a line connected tank or container type liquid heater having an immersion heating element and a baffle or guard to direct the liquid.
  
[List of Patents for class 122 subclass 19.2]    19.2And casing feature for stand boiler or external water tank therefor:
 This subclass is indented under subclass 13.01.  Subject matter and covering, jacketing, or sheathing means for the stand boiler or a closed receptacle outside of and for storing water heated by the stand boiler.

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18.5,for a stand boiler (e.g., water heater, etc.) that provides hot water for domestic or household use (e.g., cooking, cleaning, washing, bathing, space heating, etc.) that may be in other than a house or home (e.g., apartment building, office building, restaurant, laundry, recreational vehicle, etc.) having a fluid fueled burner and an external liquid tank.
494,for a miscellaneous casing surrounding a boiler.

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29Metal Working,   subclass 455.1 for a method of assembling or joining a spaced wall tube or receptacle.
220Receptacles,   subclasses 592.22 and 592.23 for a thermally insulated receptacle for heated contents (e.g., fireless cooker, etc.) or subclass 694.1 for an external covering for a hot water heater or boiler.
312Supports: Cabinet Structure,   subclass 236 for a cabinet structure intended for heating, cooling, or heat exchange means.
  
[List of Patents for class 122 subclass 20]    20SUBSIDIARY:
 This subclass is indented under the class definition.  Steam generators or water heaters located either in the firebox, combustion chamber, or offtake flue of a furnace whose main purpose is not for the generation of steam or the heating of water in such boiler. These boilers may be of any form consisting of mere pipes or coils, hollow plates, or cylinders with or without fire flues or tubes.

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6+,10, 37, 38, 439, and 498, for analogous structure.

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126Stoves and Furnaces,   for a water heater or steam generator of an open or unpressurized type, or may be a closed or pressurized type if it is part of the stove or furnace structure, subclass 5 for a cooking and heating stove having a water heater or steam generator, subclass 31 for a cooking stove having a water heater in a flue extension, subclass 34 for a cooking stove having a water back, subclass 101 for a hot air furnace combined with a boiler, subclasses 364.1 and 365.1 for a liquid heater stovepipe, or subclasses 513 and 514 for a fireplace with a liquid heater.
  
[List of Patents for class 122 subclass 21]    21CHEMICAL:
 This subclass is indented under the class definition.  Boilers wholly or partly heated by chemical action other than that of the combustion of fuel. This subclass includes that type of liquid heater and steam generator known in the art as "alkali" generators for steam.