Jan. 4, 1949. E, CHALLET SOLID ELEGTRIC_HEATING PLATE Filed Oct. 28, 1957‘ . ' 2,458,251 Patented Jan. 4, 1949 UNITED 2,458,251 STATES i PATENT " OFFICE 2,458,251 SOLID vELECTRIC HEATING PLATE Etienne Challet, Paris, France, assignor to Entre prises Electriques Fribourgeoises, Fribourg, " ' Switzerland, a company of Switzerland Application October 28, 1937, Serial No. 171,576 In Switzerland January 13, 1937 Section 3, Public Law 690, August 8, 1946 Patent expires January 13, 1957 3 Claims. 1 The present invention relates to electrically heated plates. (Cl. 219-37) 2 may be of round, annular, or of any other desired shape. If a solid plate of the same thickness through Referring to the drawings wherein similar ref out is heated uniformly it will ?rst become red erence characters denote like parts in the vari in a zone which is concentric to the periphery of ous views Fig. 1 illustrates a partial sectional the plate and which divides the plate surface into view of a solid round plate. The plate is indi two zones of substantially equal area. Then as cated at I and the heating element 2 therefore the heating is continued the red zone will spread is located as shown in a conventional insulating towards the periphery and towards the center unit. As is clearly shown upon Fig. 1 the dis of the plate. However the ?rst mentioned zone 10 tance between the top of each insulating unit and is generally the hottest. It is an object of the the upper surface of the plate varies for each in invention to provide means whereby the heating sulating unit. In the zone wherein there is the is uniform throughout the entire plate. maximum concentration of heat this length is On the other hand if the heating of the plate indicated by the distance line between the ar is discontinued the plate will ?rst cool at the 15 rows 3. This length gradually decreases towards periphery and at the center and the concentric the periphery and towards the center where it central zone remains red even after the other reaches the length shown by the distance lines parts of the plate have regained their normal 4 and 5. appearance. It is an object of the invention to By constructing the thickness of the metal of provide a plate wherein cooling will take place the plate proportional to the quantity of heat uniformly from the peripheries toward the central transmitted by the resistance to the plate at each zone. point a uniform heating of the entire plate may An object of the invention therefore is to pro be obtained. vide an electrically heated plate wherein the In Fig. 2 a modi?cation is shown wherein 6 stresses and strains due to heating are eliminat 25 indicates the plate, 1 the heating element and ed thereby considerably increasing the life of the distances of the heating elements from the the plate. surface of the plate is shown by the distance lines A still further object of the invention is to pro 8, 9 and I 0. vide an electrically heated plate wherein the In this form of construction the central por thickness of the plate along the zone of great 30 tion of the plate is provided with an undulating est heat concentration is increased and such in section integral with the plate. This construc creased thickness takes place gradually from the tion at the central portion will yield to any con periphery and the center of the plate to the above tractions or expansions of the plate itself. mentioned Zone of greatest heat concentration. I claim: A further object of the invention is to provide 1. An integral electrically heated plate com 35 a solid electrically heated plate in which the prising heating units and an integral metallic thickness of the metal is proportioned to the plate supporting said units, said plate having a quantity of heat transmitted by the heating thickness gradually increasing from the pe unit at each point of the plate. In this way the riphery inwardly and from the center outwardly surface portion of the plate subject to the great est concentration of heat will be heated uni formly with the periphery and the center of the plate thereby eliminating any strain at the pe ripheral and central portions and also prevent towards a concentric zone intermediate said pe riphery and center so that a uniform heating throughout said plate may take place. 2. An integral electrically heated plate com prising heating units and an integral annular ing warping. With the above and other objects in view which 45 metallic plate supporting said units, said plate having a thickness gradually increasing from the will become apparent from the detailed descrip periphery inwardly and from the center out tion below the invention is shown in the draw wardly towards a concentric zone intermediate Fig. l is a partial cross-sectional view through , said periphery and center so that a uniform heat ’ ing throughout said plate may take place. one form of an electrically heated plate con ings in which: structed in accordance with the invention. Fig 2 is a similar View of another type of elec trically heated plate. In the invention the electrically heated plate 3. An integral electrically heated plate com prising heating units and an integral metallic plate of disc shape supporting said units, said units being arranged annularly between a cen tral portion of said plate and the periphery 2,458,251 3 4 thereof, said plate having a thickness gradually REFERENCES CITED increasing from the periphery thereof inwardly and from said central portion outwardly towards n a concentric zone intermediate said periphery n - ' and central portion so that a uniform heating 5 throughout said plate adjacent said heating units - ?ghgf ffhigwggferll‘sere ces are of record ‘m the UNITED STATES PATENTS Number Name Date may take place and said plate having at said central portion an undulating con?guration whereby any contraction or expansion of said plate may be compensated for without any stress 10 1,435,153 1,492,540 1579332 1,729,673 Wolcott __________ __ 15131126, 1924 Kercher et a1 ______ __ Apr_29,1924 Owen _____________ __ Apr_ 6, 1926 Kercher et a1 _______ __ Oct 1, 1929 01‘ 8min- 1,998,764 2,015,856 Jordan ___________ __ Apr. 23, 1935 Lang ______________ __ Oct. 1,1935 ETIENNE CHALLET'