Electric band heaters

Claim 1

In an electric band heater, an open band of flexible metal for disposition around a peripheral surface to be heated with opposite end portions of said band adjacent each other, an open strap of flexible metal outside said band and having opposite end portions spaced from each other and adjacent said opposite end portions of said band, electric heater means sandwiched between said band and said strap, said heater means comprising first and second thin strips of insulating material respectively engaged with the inside surface of said strap and the outside surface of said band, a third thin strip of insulating material, resistance wire wound on said third strip, said resistance wire together with said third strip being sandwiched between said first and second strips, electrical terminal means connected to opposite ends of said wire, tensioning means for pulling said opposite ends of said strap toward each other to effect tensioning movement fo said strap and to apply pressure from the inner surface of said strap to the outer surface of said first strip, from the inner surface of said first strip to said wire and the outer surface of said third strip, from said wire and the inner surface of said third strip to the outer surface of said second strip, from the inner surface of said second strip to the outer surface of said band and from the inner surface of said band to said peripheral surface, and connecting means connecting said strap to said band for installation together as a unit, said connecting means being arranged to allow substantially free movement of said end portions of said strap toward each other independently of said end portions of said band and substantially free tensioning movement of said strap independently of said band, said connecting means comprising side edge portions of said band extending outwardly and thence toward each other outside and against said edge portions of said strap, said side edge portions of said strap being slidable relative to said side edge portions of said band during tensioning movement of said strap, Said tensioning means comprising a pair of sheet metal loop means on said opposite end portions of said strap, each of said loop means including an intermediate C-shaped portion defining a transverse opening and end portions converging from ends of said C-shaped portion into flush engagement with each other, weld means securing said end portions together, a pair of rods in said transverse openings, and screw means interconnecting said rods for drawing said rods together and tensioning said strap.