Bus bar interfaces for flexible heating elements
A flexible heating subassembly, which may be incorporated in an electric warming blanket or any other type of flexible heater, includes a single heater, which is preferably formed from an electrically conductive polymeric fabric. The subassembly further includes first and second conductive bus bars, each extending alongside a respective first and second edge of the heater, each being coupled to the heater by at least one row of stitching that extends along the respective bus bar. The edges of the heater may be folded over respective bus bars for coupling and each of the bus bars may terminate just beyond opposing ends of the heater. A ribbon of conductive material may be interposed between each of the bus bars and the heater.
1. An electric warming blanket, comprising:
a flexible heater comprising a non-conductive layer coated with a conductive material, the heater including a first end, a second end, a first edge extending between the first and second ends, and a second edge, opposite the first edge, extending between the first and second ends;
a first conductive bus bar disposed alongside the first edge of the heater and extending beyond the first and second ends of the heater to be terminated just beyond either end;
a second conductive bus bar disposed alongside the second edge of the heater and extending beyond the first and second ends of the heater to be terminated just beyond either end;
at least one first row of stitching coupling the first bus bar to the heater, the at least one first row of stitching extending along the first bar;
at least one second row of stitching coupling the second bus bar to the heater, the at least one second row of stitching extending along the second bus bar;
the first and second bus bars adapted for coupling to a power source for powering the heater;
a first lead for coupling of the first bus bar to the power source and a second lead for coupling of the second bus bar to the power source, the first lead and the second lead being coupled to the first bus bar and to the second bus bar, respectively, between the first and second ends of the heater; and
a first layer of water resistant material coupled to a second layer of water resistant material about a perimeter of the heater to form a sealed space for the heater and the first and second bus bars, without being adhered to either of the heater and the first and second bus bars; and
wherein the first and second layers of water resistant material enclose an entirety of the first and second bus bars and the first and second leads.
2. The blanket of claim 1 , wherein each of the at least one first row and the at least one second row of stitching extend beyond either end of the heater.
3. The blanket of claim 1 , wherein the first and second bus bars each extend approximately ½ centimeter beyond either end of the heater.
4. The blanket of claim 1 , wherein the nonconductive layer comprises a non-woven polymer and the conductive material comprises one of: polypyrrole, carbonized ink and metalized ink.
5. The blanket of claim 1 , wherein the nonconductive layer comprises a woven polymer and the conductive material comprises one of: polypyrrole, carbonized ink and metalized ink.
6. The blanket of claim 1 , wherein the non-conductive layer comprises a cellulose material and the conductive material comprises one of: polypyrrole, carbonized ink and metalized ink.
7. The blanket of claim 1 , wherein each of the first and second conductive bus bars comprise a metal wire.
8. The blanket of claim 7 , wherein the metal wire is one of a plurality of braided metal wires.
9. The blanket of claim 7 , wherein the metal wire includes a coating of silver.
10. The blanket of claim 1 , wherein each of the first and second conductive bus bars comprise a metal foil.
11. The blanket of claim 1 , wherein each of the at least one first row and the at least one second row of stitching comprises an electrically conductive thread.
12. The blanket of claim 11 , wherein the conductive thread comprises a non-conductive thread coated with a metal.
13. The blanket of claim 11 , wherein the conductive thread comprises a metal thread.
14. The blanket of claim 1 , wherein each of the at least one first row and the at least one second row of stitching comprises an electrically non-conductive thread.
15. The blanket of claim 1 , wherein each of the at least one first row and the at least one second row of stitching comprises a plurality of rows of stitching.
16. The blanket of claim 15 , wherein each of the plurality of rows of stitching comprises a pair of rows of stitching oriented in a zigzag pattern.
17. The blanket of claim 1 , wherein:
the first edge of the heater is wrapped over the first conductive bus bar; and
the second edge of the heater is wrapped over the second conductive bus bar.
18. The blanket of claim 1 , further comprising:
a first conductive ribbon disposed between the first conductive bus bar and the heater; and
a second conductive ribbon disposed between the second conductive bus bar and the heater.