Electromagnetic induction heating apparatus

BACKGROUND OF THE INVENTION

This invention relates in general to heating apparatus and deals more particularly with improved electromagnetic induction apparatus for heating liquid. The general aim of the present invention is to provide an improved electrically operated liquid heating apparatus which may be safely operated in any environment and which includes a heating unit which contains one or more electromagnetic induction heaters releasably supported and arranged for convenient access to facilitate servicing or replacement. The apparatus of the present invention may, for example, be arranged in a closed loop to continuously circulate a quantity of liquid heated to a predetermined temperature as, for example, in a heating system for a building or in a lubrication system. The present apparatus is also particularly well suited to receive liquid such as fuel oil from a supply source or storage tank and to supply it at a higher temperature to a remote location where it may be efficiently utilized to fire a boiler or the like.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved electromagnetic induction heating apparatus is provided which comprises a tank for receiving and containing a quantity of liquid to be heated and having a removably end cover and an inlet opening and an outlet opening. A least one electromagnetic induction heater is disposed within the tank and has a core assembly which includes a magnetic core which has parallel core sections and a primary coil wound therearound. The heater further includes a plurality of parallel heater plates having openings therein which receive the core sections and coils therethrough. Mounting brackets are provided for releasably supporting the core assembly in fixed position within the container in spaced relation to the walls thereof between the inlet and outlet openings and generally within the path of fluid flow therebetween. Rods are provided for supporting the heater plates in fixed position relative to the core assembly. A temperature responsive electrical control circuit is provided for energizing the coils to induce eddy currents in the heater plates whereby to heat the liquid to a predetermined temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat schematic side elevational view of heating apparatus embodying the present invention.

FIG. 2 is a somewhat enlarged sectional view taken generally along the line 2--2 of FIG. 1.

FIG. 3 is a somewhat enlarged fragmentary side elevational view of the heating apparatus of FIG. 1, a portion of the tank shown in vertical section to reveal heaters contained therein.

FIG. 4 is a diagrammatic view of a preferred electrical control circuit for the heating apparatus of FIG. 1.

FIG. 5 is a fragmentary plan view of another apparatus embodying the present invention.

FIG. 6 is a schematic fragmentary side elevational view of still another apparatus embodying the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings and referring particularly to FIGS. 1-3, the present invention is illustrated with reference to apparatus for heating a building or the like and designated generally by the reference numeral 10. The illustrated apparatus 10 comprises a heating unit indicated generally at 12 which includes a container or heater tank 14 containing a quantity of liquid, preferably oil, designated by the numeral 16 in FIG. 3. At least one electromagnetic induction heater such as indicated at 18a is mounted in fixed position within the tank and immersed in the liquid for heating it. The illustrated apparatus 10 comprises a closed liquid circulating system and further includes a plurality of radiation units or radiators 20, 20 connected in series with a circulating pump 22 and the heating unit 12 by conduits 24, 26, 28 and 30. The circulating pump 22 operates in response to an ambient temperature responsive control device located in the building to be heated, but not shown, as, for example, a thermostatic switch. The pump 22 circulates the heated liquid 16 through the conduits and radiator which comprise the system, in a manner well known in the art.

Considering now the heating unit 12 in further detail, the heater tank may vary in shape and may be either horizontally or vertically oriented. However, the illustrated tank 14 is generally cylindrical, supported in an axially upright position, and has a removable domed cover 32 at its upper end secured by suitable fasteners (not shown). The conduit 30 communicates with an inlet opening 34 at the lower end of the tank whereas the conduit 24 communicates with a fluid outlet opening 36 in the upper portion of the tank 14. A sight guage mounted on the wall of the tank provides visible indication of the level of the liquid 16 and a conventional pressure guage provides indication of tank pressure. The tank 14 may also be provided with a suitable pressure-relief valve (not shown) to prevent development of excessive pressure therein.

The number of electromagnetic induction heaters mounted in the heater unit 12 may vary. The illustrated heating unit 12 has three electromagnetic heaters designated 18a, 18b and 18c and supported in vertical series within the tank 14 generally between an inlet opening 34 and an outlet opening 36, respectively defined by the conduits 30 and 24, and disposed generally in the fluid flow path therebetween, the latter flow path being indicated generally by flow arrows in FIG. 3.

Referring now particularly to FIGS. 2 and 3, a typical electromagnetic induction heater, such as the heater 18a, has a core assembly which includes a generally rectangular laminated magnet core 38 which has horizontally disposed parallel core sections 40, 40 and a primary coil 42 wound around each of the core sections 40, 40, as best shown in FIG. 2. Each heater unit further includes a plurality of parallel heater plates 44, 44 which act as electrical secondaries in which eddy currents are induced to produce heat and which have openings 46, 46 therein to receive the core sections 40, 40 and the coils 42, 42 therethrough whereby the heater plates 44, 44 generally surround the core sections and the coils.

Each core assembly is mounted in fixed position within the tank and in spaced relation to the walls thereof by mounting brackets attached to opposite ends of its core 38. Each mounting bracket 48 has radially outwardly extending legs 50, 50. The outer end of each leg 50 is received and releasably retained in an upwardly opening slot formed in an associated boss 52 welded or otherwise suitably secured to the inner surface of the tank 14. The mounting brackets 48, 48 are or may be bolted to the bosses 52, 52 by fasternern 53, 53 substantially as shown in FIG. 2. In the illustrated embodiment, the three heaters 18a-c are supported in vertical series by upper and lower mounting brackets 48, 48 connected together by parallel vertically extending support members 54, 54. An associated end of each core 38 is supported in fixed position between a pair of angle brackets 56, 56 mounted on each pair of support members 54, 54 and extending transversely therebetween. The heater plates 44, 44 are supported on rods 58, 58 which have threaded ends to receive nuts and extend between the plates 54, 54 at opposite ends of the core 38. Suitable spacers may be provided along the rods for maintaining the heater plates 44, 44 in spaced relation to each other and to the plates 54, 54. Preferably, the openings 46, 46 in the heater plates 44, 44 are substantially larger than the coils 42, 42 which extend therethrough so that the rods 58, 58 support the heater plates 44, 44 in spaced relation to the coils 42, 42.

The heaters 18, 18 are arranged for sequential operation in response to the ambient temperature sensing device immersed in the heating liquid 16. This arrangement avoids risk of circuit overload when the heaters are energized. Referring now to the circuit diagram of FIG. 4, a triac 60 is connected in series between the heater 18a and an AC power supply source. The gate trigger circuit for the triac 60 is connected to a temperature responsive switch or immersion thermocouple switch 61, which senses the temperature of the oil 16 and operates at a predetermined temperature, to energize the trigger circuit. Operation of the second inner 18b is controlled by another triac 62 which has its gate circuit connected to a time delay switch 64 arranged to operate to provide a predetermined time delay after the first heater 18a has been turned on. Another gate circuit associated with the third heater 18c and responsive to operation of the second heater 18b includes a time delay switch 66 which triggers a triac 68 associated with the third heater 18c to turn on the latter heater. The illustrated circuit also includes a low level cut-out switch 70 which operates to shut off all of the heaters in the event that the level of the liquid in the tank 14 falls below a predetermined level. It will now be apparent that any number of heaters may be provided to meet the requirements of the particular system, the heaters being generally arranged to operate sequentially as hereinbefore described.

When the apparatus 10 is in operation, the circulating pump 22 operates to circulate hot liquid through the conduits and associated radiators 20, 20 in response to a suitable room thermostat or the like (not shown). When the temperature of the liquid 16 reaches a predetermined low limit, the thermocouple switch operates to sequentially energize the heaters 18a, 18b and 18c as hereinbefore discussed.

The apparatus of the present invention may take other forms and may be utilized to heat liquid for other purposes. Referring now to FIG. 5, a fragmentary portion of another apparatus embodying the present invention is indicated generally at 10a. The apparatus 10a is particularly adapted to heat oil in a lubricating system wherein a part to be lubricated is exposed to relatively low temperature which tends to increase the viscosity of the lubricant. The illustrated apparatus 10a includes a drive unit which comprises a propeller 72 mounted on a drive shaft 74 and which may, for example, comprise a portion of the propulsion mechanism for a surface vessel, submarine or the like. The shaft 74 is journalled in a bearing 76 which may be disposed a substantial distance below the surface of water and, therefore, potentially exposed to relatively low temperature. Inlet and outlet conduits 28a and 24a are connected to an associated heating unit (not shown), such as the heating unit 12 previously described. The apparatus 10a comprises a closed loop lubricating system and preferably also includes a circulating pump such as the pump 22 to provide a continuous circulating supply of heated lubricant to the bearing 76.

Referring now to FIG. 6, another apparatus embodying the invention is illustrated schematically and indicated generally at 10b. The apparatus 10e is particularly adapted for preheating bunker fuel or the like used to fire a boiler. As shown, fuel oil contained in a supply tank 77 is force fed to a heating unit 12b through conduits 28b and 30b by a pump 22b.

The heating unit 12b is substantially identical to the heating unit 12 previously described, but as shown, is oriented in a generally horizontal position, the inlet and outlet conduits 30b and 24b being respectfully connected to opposite ends thereof. The outlet conduit 24b supplies preheated fuel oil to a conventional oil burner 78 which fires a boiler 80. When the apparatus comprises a fuel preheating system of the aforedescribed general type, additional conventional safety controls may be provided and electrically interlocked with the circuit network which controls the heaters associated with the heater unit 12b, as is well known in the art.

In the preceeding description and in the claims which follow the terms upper, lower, horizontal and vertical are employed for convenience to describe the orientation of the heater assemblies and supporting means relative to the heater tank, however, it should be understood that the tank which comprises the apparatus may be operated in either horizontal or vertical position.