Patent ID: 7147458

Claim:
A heater assembly for mounting around a fluid flow channel in an injection molding apparatus, the heater assembly comprising: an inner tube comprising a first heat conductive material having a first coefficient of thermal expansion, the inner tube having a selected longitudinal length, an inner surface, and an outer surface, said inner tube also having a slot extending through the length of the inner tube; a first ring having an inner surface engaged around the outer surface of the inner tube along a first selected length which is less than about 10 percent of the longitudinal length of the inner tube, the first ring comprising a second material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion; a second ring having an inner surface engaged with the outer surface of the inner tube along a second selected length which is less than about 10 percent of the longitudinal length of the inner tube, the second ring also comprising the second material having the second coefficient of thermal expansion; and a heater mechanism mounted around the outer surface of the inner tube and capable of heating the inner tube to a selected elevated temperature.