Flareless tube fitting for 37.degree. adapter

A flareless tube coupling for a cylindrical tube comprising, in combination, an adapter having external threads, an external conical nose surface extending outwardly from the end of the adapter and an interior bore concentric with said nose surface, a nut of annular configuration having an internal bore including a threaded region adjacent one end having an outer end and adapted to engage the threads of said adapter, a central ferrule receiving region, and a reduced diameter region adjacent the other end, an annular ferrule within said nut central region, said ferrule including a primary body portion having a substantially cylindrical outer wall and having a minimum inner diameter greater than the outer diameter of the tube and having first and second ends, said ferrule body portion having an annular conical adapter nose engaging surface defined at said first end of an angular orientation complimentary to the angle of said adapter nose surface and an annular axially extending hinge wall of reduced wall thickness projecting from said second end adjacent said ferrule body portion outer wall having an outer cylindrical surface constituting an extension of said body portion outer wall, an annular seal portion defined on said hinge wall axially spaced from said body second end having an inner surface and an outer surface, at least one radially inwardly projecting annular lip defined on said inner surface adapted to sealingly engage the tube, a first conical cam surface defined on said outer surface in radial alignment with said lip, and a second conial cam surface defined upon said nut at said central region axially overlapping and engaging said first cam surface upon threading of said nut upon said adapter threads to radially deform said ferrule seal portion inwardly establishing a seal between said lip and the tube and axially forcing said ferrule body nose engaging surface into a sealing engagement with said adapter nose surface, the axial length of said ferrule being greater than the axial distance between said second cam surface and adapter nose surface which permits the outer end of said nut threaded region to engage said adapter threads whereby said ferrule must be placed in said nut central region with said first and second cam surfaces overlapping and engaging to permit engagement of said adapter threads with said nut threaded region outer end and reversal of said ferrule within said nut central region prevents engagement of said adapter threads with said nut threaded region outer end.