US 2272658 A
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Description (OCR text may contain errors)
Feb. 10,1942. E, CHALLET 2,272,658
ELECTRIC HEATING PLATE Filed 001:. 29, 1938 Fi .3 B94 -/7' .5 '1' )2 Patented Feb. 10, 1942 ELECTRIC HEATING PLATE Etienne Challet, Paris, France, assignor of onefourth to Enterprises Electriques Fribourgeoises, Fribourg, Switzerland Application October 29, 1938, Serial No. 237,733 In Switzerland November 4, 1937 3 Claims.
The present invention has for its object an electric heating plate comprising at least two concentric parts which are adapted to be arranged at different levels, according to Swiss Patent No, 193,023, said invention being further characterized by the fact that each of the concentric parts is formed by at least one torus, the cross-section of each of said parts being so shaped that it enables contact to be made with the bottom of a deformed receptacle, along a circular line located as near as possible to the zone where the density of heating of said part is at a maximum.
In a first embodiment, each part is formed by a single torus of circular or oval cross-section which may or may not be flattened, that is to say which has a more or less pronounced flattened portion at the upper part thereof.
In a second embodiment, the cross-section of the single torus forming each part is shaped like an elongated bean, the convexity of which is turned upwards.
In a third embodiment, each part is formed by a group of tori, three for example, the tori forming each part occupying an invariable position relatively to each other, said tori being contiguous or not and of circular or oval cross-section, it being possible for the upper envelope curve of the tori of the same part to be independent or to belong to the same tubular spiral.
Preferably, abutments may be provided for the inner parts of smaller diameter, so that under the weight of a receptacle of small diameter, which does not rest on the outer part of the plate, the inner part of the plate is not pushed right in.
The accompanying drawing shows diagrammatically and by way of example, cross-sections of a number of embodiments of the plate according to the invention, Figs. 1, 2 and 6 being elevational views in cross-section of three embodiments of the hot plate and Figs. 3, 4 and 5 being cross-sectional views showing the various shapes each heating element torus can assume.
Fig. 1 relates to a first embodiment comprising two concentric parts I and 2 each formed by a single torus of circular cross-section. The inner part 2, in the inoperative position, is urged by springs 3 in such a manner as to be higher than the part I. The latter is supported by supports 4. Abutments l1 limit the inward movement of the part 2 under the weight of a receptacle of small diameter. The top of said abutments l1 is located at such a height that it is a small amount d lower than the lower part of I, so as to allow of an efllcient contact with a deformed receptacle having a convex bottom. The relative positions of the parts I and 2 will therefore be automatically determined by the shape of the bottom of the receptacle that is placed on the plate, the inner part being higher if the bottom of the receptacle is concave, or on the contrary being lower if the bottom of the receptacle is convex, the parts being on the same level if the bottom of the receptacle is flat.
It will be observed on the other hand that the cross-section of the torus forming each of the parts is of such a shape that it enables contact to be obtained with the bottom of a deformed receptacle along a circular line which is as near as possible to the zone where the density of heating of said part is at a maximum.
Fig. 2 shows an embodiment of the same type but having three parts 5, G and I which are successively higher relatively to -each other when there is no receptacle on the plate, each part being likewise formed by a single torus. The part I is supported by springs 9; the part 6 is supported by springs 8, whereas the part 5 rests on fixed supports I0. This embodiment has the same properties as the embodiment of Fig. 1.
Instead of having a circular cross-section, the tori forming the various parts of the various embodiments could have a cross-section shaped like a circle which is slightly flattened at the top and at the bottom, as the cross-section H of Fig. 3, or an oval cross-section such as the cross-section I2 of Fig. 4, or finally an elongated bean-shaped cross-section, the concavity of which is turned downwards, such as the crosssection l3 of Fig. 5.
Fig. 6 relates to another embodiment in which each part l4 and I5 is formed by three tori that occupy invariable positions relatively to each other, the central torus of each part being higher than the two adjacent tori, that is to say that the envelope curve at the upper portion in each part is of convex shape. The central torus of the part I5 is a small amount, d, higher than the central torus of the part I 4. The part It rests on fixed supports I 8, whereas the part l5 rests on springs l6.
Of course, the number of parts is not limited to two and the number of tori in each part is not limited to three. part may be contiguous or not, and may be independent of each other or belong to the same tubular spiral. .It will furthermore be observed Finally, the tori of the same I that the plate shown in Fig. 6 also has the properties attributed to the plate of. Fig. l.
The supporting springs could be replaced by equalizing arrangements, as is the case for certain of the plates described in the aforesaid Swiss patent.
I claim: l
1. An electric heating plate comprising a plurality of concentric parts, means permitting said Parts to move relative to one another to insure a shape-conforming engagement with the bottom 01' a vessel placed on said plate and each or said concentric parts constituting a plurality of tori forming a set of tori having a cross section defining a convex upper envelope curve.
2. An electric heating plate comprising a plurality oi concentric parts, means permitting said parts to move relative to one another to insure a shape-conforming engagement with the bottom of a vessel placed on said plate, each of said concentric parts constituting a plurality oi tori forming a set of tori having a cross section defining a convex upper envelope curve, and each set or tori containing only one continuous resistance coil.
3. An electric heating plate comprising a plurality or concentric parts. means permitting said parts to move relative to one another to insure a shape-conforming engagement with the bottom of a vessel placed on said plate, each of said concentric parts constituting a torus with a convex upper surface so that contact may be made along a circular line with a deformed bottom of a vessel placed on said plate, and abutments for limiting said relative movement of said parts.