Method for tension expanding tubes

Claim 1

A method of providing uniform dimensional integral belled portions in the ends of plate fin heat exchangers having a plurality of apertured plate fins parallelly spaced between two apertured tube sheets and a plurality of hairpin tubes extending through the apertures in which the open ends of the tubes are positioned for a manufacturing operation comprising the steps of: locating the plate fin heat exchanger in a belling station so that the tube sheet nearest the open ends of the hairpin tubes is adjacent to a clamping means for providing a clamping force to hold the tube at a desired distance from the open ends and clamping the tubes therewith; forming radially expanded bells in the ends of the tubes up to the desired distance from the open ends of the tubes and then releasing the clamping force; positioning the belled plate fin heat exchanger in an expanding station so that the bell is adjacent the tube sheet nearest the bell; clamping the ends of the plate fin heat exchanger in a retainer means to prevent the hairpin tubes from moving; and expanding the tube radially outward into contact with the nearest tube sheet, then the plate fins, then the other tube sheet in tension expansion.

Claim 2

A method of providing uniform dimensional integral belled portions in the ends of plate fin heat exchangers having a plurality of apertured plate fins parallelly spaced between two apertured tube sheets and a plurality of hairpin tubes extending through the apertures in which the open ends of the tubes are positioned for a manufacturing operation comprising the steps of: locating the plate fin heat exchanger in a belling station so that the tube sheet nearest the open ends of the hairpin tubes is adjacent to a clamping means for providing a clamping force to hold the tube at a desired distance from the open ends and clamping the tubes therewith; forming radially expanded bells in the ends of the tubes up to the desired distance from the open ends of the tubes and then releasing the clamping force; positioning the belled plate fin heat exchanger in an expanding station so that the bell is adjacent the tube sheet nearest the bell; clamping the ends of the plate fin heat exchanger in a retainer means to prevent the hairpin tubes from moving; and expanding the tube radially outward into contact with the nearest tube sheet, then the plate fins, then the other tube sheet in tension expansion.