Patent Application
20180366257
The present invention relates to cap sealing electric inductor assemblies formed from cap sealing electric inductors encased in a thermally conductive powder and electric power transformer assemblies used in electric induction material heating and melting apparatus formed from electric power transformers encased in a thermally conductive powder.
Induction sealing, otherwise known as cap sealing or electric induction foil cap sealing, is a non-contact method of induction heating a sealing material over the opening of a container such as the opening of a bottle after filling the bottle with product that will be used at a future time when the sealing material will be removed. The term foil cap sealing is also used since in some cap sealing applications an aluminum foil layer liner is inductively heated to bond a polymer film in the sealing material to the lip of the opening of the bottle or other container.
Since its development in the 1920's, electric induction heating systems have found a countless range of application in manufacturing processes, materials, and food processing as well as in multiple metallurgy practices, among others. In an electric induction industrial or commercial heating application, a variable magnetic field of high frequency heats up an object by means of electromagnetic forces. The variable magnetic field is produced due to the electric current in an electrical conductor that is commonly known as an induction work coil. When an object is exposed to a variable magnetic field, eddy electric currents are induced in the object itself. The magnitude of the eddy electric currents depends on the electrical and the magnetic properties of the object. The eddy electric currents produce Joule power losses that overheat the object. The power losses increase as the magnitude of the electric current and the frequency increases.
On the other hand, the electric current that flows through the induction work coil (also referred to as electrical conductor or inductor) produces Joule power losses in the induction work coil itself. The power losses increase as the resistance of the induction work coil increases. Typically, the resistance of an electrical conductor increases as the temperature of the conductor increases. Therefore, the Joule power losses contribute to the overheating of the induction work coil and to the decrease in the efficiency of the electric induction heating system. Nevertheless, typical induction work coils are built with hollow copper tubing where a cooling flow, commonly water, is injected to avoid the overheating of the induction work coil. Additionally, in low power (for example 5 kW or less) applications, as those implemented in cap sealing applications, the induction work coils are formed with litz wire that can be cooled with the forced flow of a cooling fluid or heat exchangers that require a large surface area of heat dissipation transfer elements (fins) for a sufficient rate of cooling.
At certain frequencies, litz wire has a lower electrical resistance than a solid electrical conductor. The lower electrical resistance of the litz wire contributes to reduce the amount of power losses and overheating of the induction work coil.
In some conventional foil cap sealers litz wire coils are used as the cap sealing inductor and are encapsulated in hard potting materials. Hard potting materials have relatively poor thermal properties. The poor thermal properties of the encapsulation potting materials contribute to the overheating of the induction cap sealing coil. Therefore a more robust cooling system is required to cool down an induction cap sealing coil that has been encapsulated in a hard potting material. Also, induction cap sealing coils that are encapsulated in hard potting materials are more susceptive to mechanical fractures that are produced by thermal stresses and electromagnetic forces.
Abreast of the development of the industrial and commercial induction heating apparatus that are used to heat or melt workpieces, electric transformers have been extensively used and improved to increase the efficiency of the electric power transmission from the power source to the induction work coil. Commonly electric power transformers are used as matching impedance devices in electric induction heating applications to enhance and increase the tuning capabilities of the system's power sources with the induction load, for example, a cap sealing, welding or soldering induction coil. A typical electric power transformer is formed with windings in the shape of circular cables, solid conductors and/or cylindrical shaped conductors that are wrapped and lumped around a shell form magnetic core.
In an electric power transformer the Joule power losses in the windings, as well as eddy current and the hysteresis losses from the magnetic core, increase as the frequency of the electric induction heating system's power source increases. The power losses produce overheating and hot spots that impact negatively on the performance of the electric power transformer. To avoid overheating damages, ordinary cooling apparatus implement the injection and/or the immersion of the entire transformer unit or assembly in a cooling fluid, which is generally mineral oil or water.
Water cooling and fan systems require the implementation of auxiliary equipment and movable parts such as water connectors, water pumps, fan blades and motors, among other components, that contribute to an increase in the overall volume and weight of the electric induction heating system and also complicates cleaning and maintenance procedures for a cap sealing electric inductor or an electric power transformer used in an electrical induction heating system.
U.S. Pat. No. 6,713,735 B2 discloses one example of an induction foil cap sealer with separately mounted sealing head module and power supply module where both modules are convection air-cooled and heat pipes are used to transfer heat from the sealing head module.
U.S. Pat. No. 4,343,989 discloses a cast magnesium based structure as a heat storage material.
It is an object of the present invention to provide a cap sealing electric inductor assembly with improved thermal dissipation and mechanical performance.
It is another object of the present invention to provide an electric power transformer assembly with improved thermal dissipation as used in electrical induction heating apparatus, for example, where the application is cap sealing, welding or soldering.
In one aspect the present invention is a cap sealing electric inductor assembly formed from a cap sealing electric inductor encased in a thermally conductive powder either in direct contact with the cap sealing electric inductor or contained in a non-metallic thermally conductive powder enclosure conformed to the outer shape of the cap sealing electric inductor with the thermally conductive powder in direct or indirect heat transfer contact with a heat exchanger array to transfer heat generated by operation of the cap sealing electric inductor to ambient.
In another aspect the present invention is an electric power transformer assembly in an industrial electric induction workpiece heating application where the electric power transformer assembly is formed from an electric power transformer encased in a thermally conductive powder either in direct contact with the electric power transformer or contained in a non-metallic thermally conductive powder enclosure conformed to the outer shape of the electric power transformer with the thermally conductive powder in direct or indirect heat transfer contact with a heat exchanger array to transfer heat generated by operation of the electric power transformer to ambient.
The above and other aspects of the invention are set forth and described in the present specification and the appended claims.
The appended drawings, as briefly summarized below, are provided for exemplary understanding of the invention, and do not limit the invention as further set forth in this specification and the appended claims.
There is shown in
The cap sealing electric inductor 12 in various embodiments of the invention is formed as a single or a plurality of induction coils, cables or litz wire configured as a cap sealing electric inductor assembly in a cap sealing electric induction apparatus.
There is shown in
The electric power transformer 22 in various embodiments of the invention comprises transformer windings and one or more magnetic cores as known in the art.
In some embodiments of the invention the thermally conductive powder is contained in a non-electrically conductive powder enclosure that conforms to the outer surface area of the cap sealing electric inductor or the electric power transformer to encase the inductor or transformer, which configuration achieves uniform heat conduction from operation of the cap sealing electric inductor or the electric power transformer to the environment (ambient) external from the cap sealing electric induction apparatus or the electric induction heating application in which the cap sealing electric inductor or electric power transformer is installed.
In some embodiments of the invention if the thermally conductive powder also has a high electrical resistivity, for example when the thermally conductive powder is a magnesium oxide powder composition, the thermally conductive powder is applied directly to the outer surface area of the cap sealing electric inductor to encase the inductor without producing additional Joule power losses that can occur when, for example, conventional aluminum based thermally conductive inductor encapsulants are used. If the thermally conductive powder is also used in an application where the cap sealing electric inductor or the transformer windings have an outer (dielectric) insulation applied to the inductor (for example formed from cables or litz wires) or the windings, the outer electrical insulation can be eliminated and replaced with the thermally conductive powder applied directly to the outer surface area of the cap sealing electric inductor or windings to encase the inductor or windings with improved thermal contact and heat transfer between the cables, wires or windings and a weight reduction of the assembly.
In some embodiments of the invention a heat transfer array 16 or 26 is a heat sink as known in the art, with the heat absorption element in thermal contact with the exterior of a powder enclosure, if used in a particular application, with the transferred heat dissipation element of the heat exchanger located in ambient. In other embodiments of the invention the heat sink is in direct contact with the thermally conductive powder either within a powder enclosure or the thermally conductive powder in direct contact with the cap sealing electric inductor on the electric power transformer with heat transfer surface to ambient.
Cap sealer assembly 30, shown in exploded view in
In the example of the invention shown in the drawings, top powder encased inductor plate 38 provides physical containment and protection of inductor 42 encased in thermally conductive powder 44. The frame, lower cover plate and top powder encased inductor plate form an exterior powder enclosure for the inductor encased in thermally conductive powder 44. The detailed form and configurations of these components will vary as the shape and type of the inductor varies for a particular application. As illustrated in cross section of the assembled cap sealer assembly 30 in
In other embodiments of the invention where the inductor is formed from one or more induction coils and the thermally conductive powder is in direct contact with the induction coils, the induction coils are provided without outer dielectric insulation and the thermally conductive powder is configured for electrical insulation between the induction coils without outer electrical insulation. Other types of air-cooled inductors with suitable current densities and heat dissipation rates can also be used in other embodiments of the invention.
In other embodiments of the invention the exterior powder enclosure is extended to around the outer surface area of inductor 42 with inner powder boundary enclosure region 45a comprising a thermally conductive non-metallic material so that the thermally conductive powder is contained in a non-metallic thermally conductive powder enclosure that conforms to the outer surface area of cap sealing electric induction coil 42 for an embodiment of the invention where the cap sealing electric inductor in indirect contact with the thermally conductive powder in the non-metallic thermally conductive powder enclosure.
In other examples of the invention cap sealing electric inductor 42 is formed from litz wire with the thermally conductive powder providing electrical insulation between the multiple strands comprising a litz wire or the exterior electrical insulation of each litz wire in applications where the inductor is formed from multiple litz wire.
In some embodiments of the invention shown in the drawings the upper side of top powder encased inductor plate 38 provides a location for: mounting electrical components associated with inductor 42, such as electric power transformer 52 and a capacitor for tuning an LC circuit formed by the inductor and the capacitor; connecting components that may be required for electrical conductors from a cap sealing apparatus power supply (not shown); and connecting means for the terminating ends 42a and 42b of inductor 42 to components mounted on the top powder encased inductor plate 38.
In some embodiments of the invention, as shown in the drawings, electric power transformer 52 is mounted on the upper surface of top powder encased inductor plate 38 as shown in
In embodiments of the invention where the windings of the electric power transformer are formed from insulated wires or cables and the thermally conductive powder is in direct contact with the windings of the transformer, the wires or cables are provided without outer dielectric insulation and the thermally conductive powder is configured for electrical insulation between the wires or cables without outer electrical insulation.
In other examples of the invention electric power transformer 52 is formed from litz wire with the thermally conductive powder providing electrical insulation between the multiple strands comprising a litz wire or the exterior electrical insulation of each litz wire in applications where the inductor is formed from multiple litz wire.
In some embodiments of the invention shown in
One example of a heat exchanger array used in some embodiments of the invention is shown in
In other examples of the invention, top powder encased inductor plate 38 is not used and is replaced by evaporator elements 62 as a section of the external powder enclosure, or alternatively embedded in the thermally conductive powder, so that the heat exchanger array is in direct heat transfer contact with thermally conductive powder 44 to remove heat from the powder to ambient at the one or more condenser elements 66. The heat transfer fluid, such as a water-based fluid or other suitable liquid, contained within the sealed evaporator elements 62 absorbs the heat. Each connecting tube 64 has one end of its interior passage connected to the sealed interior of an evaporator element, and the opposing end connected to the sealed interior of a condenser element 66. The connecting tube 64 serves as a connector that provides a path for the heat transfer fluid from an evaporator element to a condenser element. The heated fluid moves through the one or more connecting tubes 64 to the one or more condenser elements 66 in which the transfer fluid radiates heat to the surrounding ambient environment, which is generally air within a normal room temperature range.
In other examples of the invention, the heat absorbing element of the heat exchanger array, for example, the evaporator elements 62 in
A preferable thermally conductive powder for the present invention is a powder composition with a thermal conductivity of greater than 30 W/m·K, for example, a magnesium oxide power composition refined to a thermal conductivity greater than 30 W/m·K or another powder composition with a thermal conductivity greater than 30 W/m·K.
Selected thermally conductive powders, such as magnesium oxide, have a secondary benefit of eliminating thermal stress fractures and fractures from electromagnetic forces in a cap sealing electric inductor or an electric induction power transformer when compared with conventional hard potting materials.
Reference throughout this specification to “one example or embodiment,” “an example or embodiment,” “one or more examples or embodiments,” or “different example or embodiments,” for example, means that a particular feature may be included in the practice of the invention. In the description various features are sometimes grouped together in a single example, embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects.
The present invention has been described in terms of preferred examples and embodiments. Equivalents, alternatives and modifications, aside from those expressly stated, are possible and within the scope of the invention. Those skilled in the art, having the benefit of the teachings of this specification, may make modifications thereto without departing from the scope of the invention.
This application claims priority to U.S. Provisional Application No. 62/520,165 filed Jun. 15, 2017, hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62520165 | Jun 2017 | US |
