Patent ID: 7306684

Claim:
A method for heat treating a track bushing in a form of a hollow cylinder and having a cylindrical passageway with an inside diameter extending longitudinally and centrally along a longitudinal axis, the track bushing having an inner circumferential surface surrounding the longitudinal axis to define the passageway and an outer circumferential surface surrounding the longitudinal axis to define an outer cylindrical surface, the track bushing having a disk-shaped first end portion defining a first opening into the passageway and a disk-shaped second end portion defining a second opening into the passageway, the method comprising the steps of: inserting a tube into the first opening until an end of the tube is disposed at or adjacent to the second opening, the tube positioned within the passageway to define an annular opening between the inner circumferential surface of the track bushing and an outer surface of the tube, the tube having an outside diameter; covering the second opening of the passageway with a diverting member, the diverting member being in contact with the second end portion of the track bushing in a sealed manner; providing a heater for heating the track bushing, the heater positioned to surround the outer circumferential surface of the track bushing; heating the track bushing to a quenching temperature; and cooling the heated track bushing by causing a cooling fluid medium to flow along the tube in a first anti-gravitational direction being parallel to the longitudinal axis and then into the annular opening such that the cooling fluid medium contacts the inner circumferential surface of the track bushing, flows thereafter in a second gravitational direction being opposite the first direction and then exits from the first opening.