Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
1999-10-14
2001-05-15
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S624000, C219S670000
Reexamination Certificate
active
06232586
ABSTRACT:
The invention relates to a core structure for an induction heating element for use in a cooker for food.
Induction heating coils are well-known, comprising as a minimum a flat “pancake” coil fitted below and parallel to the cooking vessel. The magnetic field around such a coil has large stray field which does not contribute to the heating but rather heats up irrelevant metal parts. In order to improve the situation it is known to place a number of radially disposed ferrite rods on the underside of the coil. In order to further improve the functioning of this heating method, a more complete core structure is known, being constituted of a shallow dish-shaped structure having an upwards-facing rim and a central pole piece.
Particular losses are occuring because of the stray field at the junction between the rim and the cooking vessel. This stray field is considered undesired and it is also under regulation in that it is considered that it should exceed a certain maximum value. There is hence a need to improve the magnetic coupling between the core and the cooking vessel. The problem is that without forcing the consumer to use cooking vessels constructed in a particular manner, it is only possible to use a change in the disposition of the core as a parameter.
According to the invention a reduction of leakage flux is obtained by means of a rim structure which presents a large area towards the lower edge of the cooking vessel. This has the effect that the edge of the cooking vessel acts as an “attractor” for flux lines, and hence reduces the flux which has to take a lengthy path via the air. The pole piece area will in practice be greater than the cross sectional area of the rim itself, and this may e.g. be obtained by means of a slanted cut of the rim.
In one advantageous embodiment of the invention, the mean diameter of the rim has essentially the same diameter as the cooking vessel and the outer edge of the rim is raised above the inner edge.
In a further embodiment of the invention both the lower and the upper edge of the rim are disposed above the level of the cooktop. In this manner, an automatic centering of a cooking vessel is obtained, and the bottom of the cooking vessel is raised above the level of the cooktop which prevents conductive heating of the cooktop and the coil below the surface. Preferentially the outer edge of the rim is rounded.
In a further advantageous embodiment of the invention the rim of the core is inwards slanted and has a maximum diameter which corresponds to the cooking vessel. In this embodiment, the slanted rim is cut off horizontally, and the core surface is essentially flush with or raised slightly above the cooktop surface. The area presented to the edge of the cooking vessel is actually the outer side of the inwards slanting rim part.
REFERENCES:
patent: 3949183 (1976-04-01), Usami et al.
patent: 4467162 (1984-08-01), Konda et al.
patent: 4527031 (1985-07-01), Aparicio
patent: 4789767 (1988-12-01), Doljack
patent: 5690851 (1997-11-01), Yoshioka et al.
patent: 44 29 183 A1 (1996-02-01), None
patent: 762183 (1934-04-01), None
patent: WO 94/05137 (1994-03-01), None
Aktiebolaget Electrolux
Leung Philip H.
Pearne & Gordon LLP
LandOfFree
Core structure for an induction heating element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Core structure for an induction heating element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Core structure for an induction heating element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2554853