Apparatus for heating a mirror or the like

• US 5,015,824 A
• Filed: 07/05/1990
• Issued: 05/14/1991
• Est. Priority Date: 02/06/1989
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated
• Original Assignee: The Thermacon Incorporated
• Inventors: Smith, Ronald L., Monter, Robert P.
• Primary Examiner(s): Walberg, Teresa J.
• Application Number:
  US07/548,618
• Time in Patent Office: 313 Days
• Field of Search: 219/219, 219/541, 219/549, 219/528, 219/529, 219/522, 219/203, 219/504, 219/505, 338/22 R
• US Class Current: 219/219
• CPC Class Codes: H05B 3/845 specially adapted for reflecting surfaces, e.g. bathroom - or rearview mirrors

Abstract

A layer of conductive polymer having a positive temperature coefficient (PTC) of resistivity and a uniform thickness, is laminated between copper foils to form a composite sheet which is die-cut to form a planar heater assembly. A small portion of the laminated heater assembly is bent laterally outwardly to form a connector tab, and the heater assembly is adhesively bonded to the back surface of a rear view mirror having a corresponding shape and size. A plastic case supports the mirror and spring-like electrical contact terminals which engage the copper foils on the tab, and the terminals are connected to electrical conductors to provide for heating the entire mirror according to variations in temperature on the mirror surface. The tab may be lanced from the heater assembly or be formed from a projecting edge portion, and the heater assembly may be enclosed within a flexible plastic film to provide resistance to chemical corrosion. In another embodiment, the foils are connected by rivets and insulating sleeves to corresponding electrical tabs or terminals located on the inner side of the heater assembly.

Claims

1. A heater assembly adapted to be attached to a mirror having a predetermined shape and size, comprising a layer of conductive polymer having opposite parallel flat surfaces providing said layer with a substantially uniform thickness, said polymer having a positive temperature coefficient of resistivity, a set of continuous metal foils bonded to said opposite surfaces of said layer and cooperating to form a laminated heater assembly having a uniform thickness with said layer of said polymer between said foils, said metal foils and said polymer layer having the same size and shape and generally the same as the size and shape of the mirror, means for attaching one of said metal foils forming one side of said heater assembly to the mirror, a portion of said laminated heater assembly including corresponding portions of said layer and said foils projecting laterally from the plane of said one metal foil and away from the mirror, means on the other side of said heater assembly for connecting said laterally projecting portions of both of said foils to a corresponding pair of electrical conductors, and said heater assembly being effective to heat substantially the entire mirror according to variations in temperature of different areas of the mirror.

2. An assembly as defined in claim 1 wherein said laterally projecting portion of said laminated heater assembly forms a connecting tab, and said connecting means connect the electrical conductors to said portions of said foils on said tab.

3. An assembly as defined in claim 2 wherein said connecting tab is spaced inwardly from the peripheral edge of said heater assembly and forms a hole through said heater assembly.

4. An assembly as defined in claim 2 wherein said portion of said heater assembly forming said tab comprises a peripheral edge portion of said heater assembly.

5. An assembly as defined in claim 2 and including a set of electrical conductive spring terminals engaging said metal foils on said portion forming said tab.

6. An assembly as defined in claim 5 and including a case of molded plastics material, said case having means for supporting the mirror and said heater assembly, and said case supports said terminals in position to engage said metal foils on said tab.

7. An assembly as defined in claim 1 wherein said connecting means comprise a pair of tab like terminals, a pair of electrically conducting fasteners extending through said laterally projecting portion of said heater assembly, and means electrically insulating each of said fasteners from one of said metal foils.

8. An assembly as defined in claim 1 and including a thin flexible plastic film surrounding said heater assembly and providing a protective enclosure for said heater assembly.

9. A heater assembly, adapted to be attached to a mirror having a predetermined shape and size, comprising a layer of conductive polymer having opposite parallel flat surfaces providing said layer with a substantially uniform thickness, said polymer having a positive temperature coefficient of resistivity, a set of continuous metal foils bonded to said opposite surfaces of said layer and cooperating to form a planar laminated heater assembly having a uniform thickness with said layer of said polymer, between said foils, said metal foils and said polymer layer having substantially the same size and shape and generally the same as the size and shape of the mirror, means for attaching one of said metal foils forming one side of said heater assembly to the mirror, a portion of said laminated heater assembly being deformed laterally from the plane of said one metal foil and away from the mirror, means defining at least one hole within said portion, an electrically conducting connector element positioned adjacent said deformed portion, an electrically conducting fastener extending through said hole and electrically connecting said conductor element to said one metal foil, means for electrically insulating said conductor element from the other adjacent said metal foil, and said heater assembly being effective to heat substantially the entire mirror according to variations in temperature of different areas of the mirror.

10. A heater assembly as defined in claim 9 and including means defining a second said hole within said deformed portion, a second said electrically conducting connector element positioned adjacent said deformed portion and electrically connected to said other adjacent metal foil, a second fastener extending through said second hole and securing said second connector element to said other metal foil, and means for electrically insulating said second fastener from said one metal foil.

12. A heater assembly as defined in claim 10 wherein each said fastener comprises a rivet, and said means for electrically insulating each said element comprise an insulating sleeve mounted on the corresponding said rivet.

13. A heater assembly as defined in claim 9 wherein said fastener comprises a rivet, and said electrically insulating means comprise an insulating sleeve mounted on said rivet and extending into said hole.

11. A heater assembly as defined in claim wherein each said electrically conducting connector element comprises a tab projecting laterally in the same direction as said deformed portion of said laminated heater assembly.

14. A heater assembly adapted to be attached to a mirror having a predetermined shape and size, comprising a layer of conductive polymer having opposite parallel flat surfaces providing said layer with a substantially uniform thickness, said polymer having a positive temperature coefficient of resistivity, a set of continuous metal foils bonded to said opposite surfaces of said layer and cooperating to form a laminated heater assembly having a uniform thickness with said layer of said polymer between said foils, said metal foils and said polymer layer having the same size and shape, a set of thin flexible plastic film sheets on opposite sides of said laminated heater assembly and having outwardly projecting peripheral edge portions sealed together to provide a protective enclosure completely surrounding said heater assembly, means for attaching said film sheet covering one of said metal foils on one side of said heater assembly to the mirror, a pair of electrical conductors disposed on the opposite side of said laminated heater assembly, and means for connecting said conductors to both of said metal foils from said opposite side of said heater assembly.

15. Heater assembly as defined in claim 14 wherein a portion of said laminated heater assembly including corresponding portions of said layer and said metal foils proJecting laterally from the plane of said one metal foil, and said connecting means are connected to said corresponding portions of said metal foils.