Corrosion resistant heat exchanger element and method of manufacture

Claim 1

A heat exchanger element for use in a corrosive environment comprising a metal tube jacketed at least over a substantial portion of its length including at least one end with an extruded layer of a given fluorocarbon resin having a thickness within the limits affording efficient heat transfer combined with resistance to corrosion of said tube, said given resin being of the type which has a high viscosity in the melt stage, a nipple of corrosion resistant metal, said nipple having a first end with a circumferential shoulder thereat and an axial region adjacent said shoulder which region has a lesser diameter than said shoulder providing an undercut annular groove therebehind, said first end of said nipple being telescopingly engaged within said one end of said metal tube, and said nipple having an opposite end which projects from said one end of said metal tube, a sleeve of fluorocarbon resin surrounding said one end of said metal tube and at least a portion of said opposite end of said nipple, said sleeve extending over said metal tube and its jacket layer of resin to a point beyond the location of said nipple shoulder, and a corrosion resistant metal ferrule surrounding said sleeve of resin and being substantially coextensive therewith, said ferrule being contracted radially squeezing said metal tube within said axial region behind said nipple shoulder thereby effecting interlocking engagement between said metal tube and said nipple and establishing a fluid-tight seal between said ferrule, said nipple, said metal tube and the intervening resin material.

Claim 13

A method of fabricating a heat exchanger element which comprises the steps in combination of selecting a metal tube which has been jacketed with an extruded layer of a given fluorocarbon resin having a thickness within the limits affording efficient heat transfer combined with resistance to corrosion of said tube, said given resin being of the type which has a high viscosity in the melt stage, selecting a nipple of corrosion resistant metal with a first end with a circumferential shoulder at said end and an axial region adjacent said shoulder which region has a lesser diameter than said shoulder providing an undercut annular groove therebehind, disposing on said tube a corrosion resistant metal ferrule and a sleeve of fluorocarbon resin, telescopingly engaging said first end of said nipple within an end of said metal tube with the opposite end of said nipple projecting from said metal tube, positioning said sleeve of fluorocarbon resin along with said metal ferrule concentrically disposed thereabout at the junction between said nipple and said metal tube so as to extend over at least a portion of said opposite end of said nipple and over said metal tube to a point beyond the location of said shoulder, and contracting said metal ferrule at least in the vicinity of said axial region to compress said metal tube and contract the same behind said shoulder to interlock said tube and said nipple and squeeze said sleeve of resin to establish a fluid-tight seal between said ferrule, said nipple and said metal tube.

Claim 14

A method of fabricating a heat exchanger element which comprises the steps in combination of selecting a metal tube which has been jacketed with an extruded layer of a given fluorocarbon resin having a thickness within the limits affording efficient heat transfer combined with resistance to corrosion of said tube, said given resin being of the type which has a high viscosity in the melt stage, selecting a nipple of corrosion resistant metal with a first end with a circumferential shoulder at said end and an axial region adjacent said shoulder which region has a lesser diameter than said shoulder providing an undercut annular groove therebehind, disposing on said tube a corrosion resistant metal ferrule and a sleeve of fluorocarbon resin, telescopingly engaging said first end of said nipple within an end of said metal tube with the opposite end of said nipple projecting from said metal tube, positioning said sleeve of fluorocarbon resin along with said metal ferrule concentrically disposed thereabout at the junction between said nipple and said metal tube so as to extend over at least a portion of said opposite end of said nipple and over said metal tube to a point beyond the location of said shoulder, and contracting said metal ferrule at least in the vicinity of said axial region to compress said metal tube and contract the same behind said shoulder to interlock said tube and said nipple and squeeze said sleeve of resin to establish a fluid-tight seal between said ferrule, said nipple and said metal tube.