Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1998-12-11
2001-02-06
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S461100, C338S283000
Reexamination Certificate
active
06184502
ABSTRACT:
The invention relates to a heater, particularly for kitchen appliances.
Such heaters can in particular be used for the heating of a hotplate. They are preferably constructed in radiant heater form and usually constitute a closed assembly, which can be fixed as such to a corresponding appliance, e.g. in a hob of an electric cooker. Such heaters have a single or multipart insulating substrate and at least one electric heating conductor fixed to the top of the insulating substrate. The insulating substrate material is appropriately at least electrically insulating, but preferably also thermally insulating, so that thermal energy is only eliminated to a limited extent towards the rear of the insulating substrate. The heating conductor can e.g. be in the form of an at least zonally straight and/or helical heating conductor wire. Particularly in the case of radiant heaters, a heating conductor can also be in flat strip form and optionally longitudinally corrugated. The assembly constituted by the insulating substrate and heating conductor appropriately has a through, normally roughly planar surface extension and, in operation, it can give off and in particular emit thermal energy substantially over the entire surface area provided with heating conductors.
The insulating substrate of such heaters is provided on its top side with a profiling having raised portions and depressions or cavities. Known heaters of this type can be subdivided into two classes. In one class the depressions are slot-like and are used for fixing the position of a heating conductor to be inserted into the slot. The heater according to U.S. Pat. No. 3,991,298 has an insulating substrate with a planar surface, in which is made a spiral slot. A heating conductor in the form of a smooth flat strip is upright in the slot and projects out of the slot over most of its height. The heater according to U.S. Pat. No. 3,612,828 also has a substantially planar insulating substrate with a spiral, relatively wide slot, in which is inserted a longitudinally corrugated flat strip heating conductor. The depth of the slot corresponds to the height of the heating conductor, so that the latter is flush with the top sides of the raised portions between the slots. In both cases the heating conductors are secured against lifting out of the slot by separate fastening elements. A similar construction occurs in the case of the heater disclosed by European patent 612 195, in which arcuate slots receive a heating conductor in the form of an upright, longitudinally corrugated flat strip, in order to fix the position of the heating conductor on the insulating substrate. In the longitudinal direction of the slot are arranged therein spaced crosswebs or crossbars made from the material of the insulating substrate and in which the heating conductor engages. The crosswebs serve to fix the heating conductor to the insulating substrate.
In the second class of heaters with profiled insulating substrate, the raised portions are in the form of straight webs, which project over a planar surface of the insulating substrate and which serve to support and fasten the heating conductors zonally embedded therein. As an example, German patent 27 29 930 discloses a heater having a circular insulating substrate and helical heating conductors installed spirally around the centre. The webs of the insulating substrate have a radial orientation, so that the heating conductor must pass over the same substantially perpendicular to the web. The rectangular heater of German patent 28 20 114 has longitudinally parallel, helical heating conductors, which are carried by uniformly spaced crosswebs of the insulating support and are zonally embedded in the latter. Here again the path of the webs is adapted to that of the heating conductor in such a way that the webs run substantially perpendicular to the longitudinal direction of the heating conductor.
The problem of the invention is to so further develop a heater according to the preamble, that it can be particularly easily manufactured.
To solve this problem the invention proposes a heater having the features of claim
1
.
A heater according to the invention is characterized in that raised portions and depressions are distributed over the top side of the insulating support in the manner of a network and that the heating conductor engages in the raised portions. The term “network” here means a surface distribution of substantially longitudinally extending structures running in different directions along the top side and which preferably meet at junctions or intersections. The junctions or intersections also have a predetermined surface distribution.
A network-like distribution of raised portions and depressions over the top side of the insulating support offers a heating conductor to be fixed to the top side fixing points or locations arranged in specific intervals predeterminable by the dimensioning of the network in the vicinity of the raised portions and in which the heating conductor can engage. Network-like, raised portions running in criss-cross manner over the top side or raised portions between network-like slots on the top side offer the heating conductor a plurality of engagement or retaining points substantially independently of the way in which the heating conductor runs on the surface. It can therefore be possible to use an insulating substrate with a specific, network-like, honeycomb or studded structuring of its surface for carrying differently designed and/or constructed heating conductors, because the profiling of the surface need not necessarily be oriented with respect to the desired manner of the installation of the heating conductor. An inventively constructed insulating substrate can be used as a universal insulating substrate, thereby facilitating the manufacture of heaters.
Although the surface distribution of intersections and longitudinally extending structures can be irregular, it is preferably uniform, so that identical configurations of raised portions and depressions are regularly repeated in different directions in the insulating substrate surface. The network can be formed by channels or slots, between which raised portions remain. As a result, e.g. surfaces with a studded structure can be created and the studs can have e.g. a truncated cone-shaped or spherical configuration. In other constructions, the network gaps are formed by depressions or cavities, so that the raised portions form the network. As a result of the meeting at the intersections, the raised portions stabilize one another.
The invention makes it possible to construct the insulating substrate by appropriate network-like, honeycomb or studded structuring of its top side for punctiform, positive fixing and securing of the heating conductor engaging in the raised portions so as to prevent a lifting out from the insulating substrate. The density of the fixing points is determined by the “mesh size” of the network and the path of the heating conductor relative thereto. There is no need to construct on the actual heating conductor fixing members for positive engagement in the insulating substrate, as is e.g. the case with the heating conductors of DE 25 51 137 or EP 590 315. The flat strip-like heating conductors according thereto have fixing feet, which are longitudinally spaced and constructed in one piece with the heating conductor and which can be manufactured by a punching process and which are provided for engaging in an insulating substrate with a planar surface. Such fixing elements on the heating conductor can be avoided in the case of an insulating substrate structured according to the invention. The invention makes it possible for the heating conductor to have a substantially constant cross-section along its length. Such heating conductors can be particularly easily manufactured, have a uniform, resistance-active cross-section along their length and consequently, when a voltage is applied, heat very uniformly along their length.
A heating conductor can e.g. be circular in cross-section, but according to a preferred embo
Dahbour Fadi H.
E.G.O. Elektro-Geratebau GmbH
Senterfitt Akerman
Walberg Teresa
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