Stove pipe elbow

Claim 1

The method of making a swivel type stove elbow comprises the steps of forming a generally rectangular piece of sheet metal with opposite end edges having notches opposite each other, rolling the rectangular piece to a tubular shape with said end edges extending axially and with one end edge overlapping the other end edge, said notches registering and the bottoms of the notches in each end edge being overlapped by a portion of the sheet of the other edge, and forming the material outside the notches in rigid lock seams of the type which prevents displacement or unlocking of said end edges, the end edges in the space between said adjacent lock seams having only two thicknesses of metal in overlapping relation and the adjacent lock seams being axially spaced from each other a distance sufficient to provide material on opposite sides of a cut between the lock seams in a plane oblique to the axis of the tube for forming interlocking slip joint means between the sections formed by the cut, cutting the tubular shape in planes oblique to the axis of the tube and between adjacent lock seams, forming the material on one side of each cut into a first external annular hollow bead terminating in an inwardly extending flange, forming the material on the other side of each cut into a second external annular hollow bead joined to an internal annular hollow bead terminating in an outwardly extending flange, and assembling the sections on opposite sides of each cut with said inwardly extending flange in said internal bead and said outwardly extending flange in said first bead.

Claim 2

The method of making a swivel type stove elbow comprises the steps of forming a generally rectangular piece of sheet metal with opposite end edges having notches opposite each other, rolling the rectangular piece to a tubular shape with said end edges extending axially and with one end edge overlapping the other end edge, said notches registering and the bottoms of the notches in each end edge being overlapped by a portion of the sheet of the other edge, and forming the material outside the notches in rigid lock seams of the type which prevents displacement or unlocking of said end edges, the end edges in the space between said adjacent lock seams having only two thicknesses of metal in overlapping relation and the adjacent lock seams being axially spaced from each other a distance sufficient to provide material on opposite sides of a cut between the lock seams in a plane oblique to the axis of the tube for forming interlocking slip joint means between the sections formed by the cut, cutting the tubular shape in planes oblique to the axis of the tube and between adjacent lock seams, forming the material on one side of each cut into a first external annular hollow bead terminating in an inwardly extending flange, forming the material on the other side of each cut into a second external annular hollow bead joined to an internal annular hollow bead terminating in an outwardly extending flange, and assembling the sections on opposite sides of each cut with said inwardly extending flange in said internal bead and said outwardly extending flange in said first bead.