Small round air stream heating unit

Claim 1

A small electric resistance air stream heater which operates directly on 120 volts with a wattage output of less than 500 watts comprising (1) an electrically insulating housing; (2) a rolled heating assembly positioned within the housing, said heating assembly having a diameter of about 6" and comprising in combination, (A) an electrically insulating core; (B) an electrically conductive crimped metallic foil heating element comprising at least two electrically connected strips thereof, each having crimps in which the distance between peaks is about 0.085 inch, said crimps having a depth of about two times the pitch between successive crimps and being substantially evenly distributed along the lengths of said strips, said foil heating element having electrical volume resistivity falling in the range of from about 75×10 -6 ohm-cm to 125×10 -6 ohm-cm, a thickness in the range of about 0.001 to 0.005 inch (0.025 to 0.127 mm), each of said crimped foil strips having a width in the range of about 0.25 inch to 0.75 inch (6.35 to 19.05 mm), the combined uncrimped length of the foil strips being in the range of about 55 to 65 feet (16.77 to 19.82 meters), said foil heating element having electrical power connections thereon, the crimps in said foil heating element forming alternate grooves and ridges which define a multitude of continuous passageways for air passing through the heater; (C) an electrical insulating backing sheet, said electrically connected crimped foil heating elements being secured to one plane surface of said backing sheet in spaced parallel relation to each other; (D) support means for said heating assembly extending radially outwardly from the core to the outer surface of the assembly, said support means comprising at least two pins of non-electrical conducting material positioned to extend through the backing for the foil heating element of the rolled heating assembly between the spaced strips thereof; and (E) thermostatic means extending radially outwardly from the core through the backing for the foil heating element at a point located between the spaced strips thereof to the outer surface of the assembly to enable a heat build-up to be detected over a large cross-sectional area of the heating assembly.