Low thermal mass solid plate surface heating unit

• US 3,895,216 A
• Filed: 09/30/1974
• Issued: 07/15/1975
• Est. Priority Date: 09/30/1974
• Status: Expired due to Term

• Current Assignee: Bohdan Hurko
• Original Assignee: Bohdan Hurko
• Inventors: Hurko, Bohdan
• Primary Examiner(s): Mayewsky, Volodymyr Y.
• Application Number:
  US05/510,211
• Time in Patent Office: 288 Days
• Field of Search: 219/434,456,459,461,462,463,464,530,543 338/61,62,63,292,293,297,316
• US Class Current: 219/458.1
• CPC Class Codes: F24C 15/104 Arrangements of connectors, grounding, supply wires
• CPC Class Codes: H05B 3/72 Plates of sheet metal

Abstract

A lightweight solid plate surface heating unit of low thermal mass with a top plate of thin composite material with a center core of high thermal conductivity and outer reinforcing layers. A coating of high electrical resistivity covers the bottom layer of the composite plate. A film heater of spiral pattern that terminates near the center of the plate is bonded to the electrical resistivity coating. A terminal block is mounted to the underside of the plate for making electrical connection with the terminal sections of the film heater.

Claims

1. A LOW THERMAL MASS SOLID PLATE SURFACE HEATING UNIT COMPRISING A TIN PLATE OF COMPOSITE SHEET MATERIAL WITH A CORE OF HIGH THERMAL CONDUCTIVITY SELECTED FROM A GROUP COMPRISING COPPER SILVER AND ALUMINUM, AND TOP AND BOTTOM LAYERS SELECTED FROM A GROUP COMPRISING STAINLESS STEEL, NICKLE AND CHROMIUM, AND LOW CARBON STEEL, SAID TOP AND BOTTOM LAYERS SERVING TO REINFORCE THE CORE AND RESTRICT ITS OXIDATION AND CORROSION, AN INSULATION LAYER OF HIGH ELECTRICAL RESISTIVITY SUBSTANTIALLY COVERING THE BOTTOM LAYER OF THE COMPOSITION PLATE, AND A FILM HEATER OF DOUBLE SPIRAL FORM BONDED TO THE INSULATING LAYER AND SERVING AS AN ELECTRICAL RESISTANCE HEATING ELEMENT, AND ELECTRICAL TERMINAL MEANS COPERATING WITH THE COMPOSITE PLATE AND ELECTRICALLY CONNECTED TO THE FILM HEATER AND ADAPTED TO CONNECT THE SURFACE HEATING UNIT IN A POWDER CIRCUIT TO PROVIDE A LOW ENERGY UNIT OF HIGHEST THEMAL EFFICIENCY, SAID ELECTRICAL TERMINAL MEANS BEING LOCATED ADJACENT THE CENTER OF THE DOUBLE SPIRAL FILM HEATER PATTERN TO CREATE A GENERALLY UNIFORM CIRCULAR HEATING PATTERN BENEATH THE COMPOSITE PLATE.

2. A low thermal mass solid plate surface heating unit as recited in claim 1, a heat reflector pan receiving the composite plate across the top thereof, fastening means for joining the reflector pan to the composite plate and capturing the said terminal means therebetween.

3. A low thermal mass solid plate surface heating unit as recited in claim 2 wherein the said electrical terminal means includes resiliently biased contact pads in electrical engagement with the film heater.

4. A low thermal mass solid plate surface heating unit as recited in claim 1 wherein the double spiral film heater is doubled back on itself adjacent the periphery of the composite plate, the film heater strip terminating adjacent the center of the composite plate in a separated pair of elongated terminal sections of relatively low resistance for unit area compared to the main heated portion of the film heater pattern so that the electrical terminations are made adjacent the center of the composite plate remote from the heated portion of the film heater.

5. A low thermal mass solid plate surface heating unit as recited in claim 2 wherein the said fastening means comprises a stud means fastened to the bottom layer of the composite plate and engaging the reflector pan for holding these parts together, an insulating terminal block including at least two fastening bolt means where each fastening bolt is supplied at its inner end with a resiliently biased contact pad in engagement with at least one of the elongated terminal sections of the film heater, while the outer end of each fastening bolt extends outwardly of the reflector pan and has a termination for receiving an electrical power supply lead.

6. A low thermal mass solid plate surface heating unit as recited in claim 4 wherein the said electrical terminal means comprises an insulating terminal block and mounting means joined to the composite plate for holding the terminal block in place, terminal post means carried by the terminal block and adapted to make electrical connection between the film heater and electrical power supply means.

7. A low thermal mass solid plate surface heating unit as recited in claim 6 wherein the composite plate is generally circular in plan view and is provided with a slight crown.

8. A low thermal mass solid plate surface heating unit as recited in claim 7 wherein each terminal post means includes a resiliently biased contact pad in electrical contact with a terminal section of the film heater strip.

9. A low thermal mass solid plate surface heating unit as recited in claim 1 wherein there is a temperature limiting means for the composite plate that is set for a maximum temperature between about 425*F and 575*F.

10. A low thermal mass solid plate surface heating unit as recited in claim 8 wherein there is a temperature limiting means for the composite plate that is set for a maximum temperature between about 425*F and 575*F.