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US 4,841,760 AGranted
Process and apparatus for manufacturing tube bends
OwnerJames M. Fergusoninventor
Life of this patent
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OwnerJames M. Fergusoninventor
Estimating the term…
A process for making a tube bend of a predetermined wall thickness from a length of straight tube comprises forming the straight tube to have a quasi-elliptical cross section and irregular wall thickness which has a maximum value on one side of the major axis of the quasi ellipse, expanding the quasi-elliptical tube to cause the wall thickness on the other side of the major axis to be reduced and bending the tube about an axis located on said other side of said major axis. Apparatus suitable for performing the process comprises a die (2) formed with an oblique inclined converging passage (3) of circular cross section at one end changing progressively to quasi-elliptical cross section at the other end and a curved mandrel (6) having a portion (8) which changes from quasi-elliptical cross section at the shank (7) to circular cross section at the curved portion (9).
A process for making a tube bend by forcing a straight tube over a curved expanding mandrel is characterized by forming a straight tube of quasi-elliptical cross section with the portion of the tube wall on one side of the major axis of the quasi-elliptical cross section of non-constant thickness which is a maximum at the point where the minor axis of the quasi ellipse meets the tube wall on one side of the major axis of the quasi ellipse and which reduces progressively on each side of said point to a reduced thickness in the vicinity of the two points where said major axis meets the tube wall, applying against the portion of the inner surface of the tube wall on the other side of said major axis a radially directed expansion force of a magnitude sufficient to displace that portion of the tube wall away from said major axis to a position in which the tube has the required internal dimensions and shape of cross section of the bend to be formed and bending the tube about an axis parallel with and spaced from said major axis and lying on said other side of said major axis.
Apparatus for forming a tube bend from a tube of quasi-elliptical cross section and non-constant wall thickness by means of a curved expanding mandrel is characterized in that the curved expanding mandrel (6) is formed with an oblique tube stretching portion (8) which changes gradually from one end to the other from a quasi-elliptical cross section of dimensions to fit within the interior contour of the tube of quasi-elliptical cross section to a circular cross section the centre of which lies on one side of the major axis of the quasi-elliptical end and the diameter of which is substantially equal to the nominal bore of the bend to be formed, and a tube bending portion (9) curved to substantially the same mean radius as that of the bend to be formed.
Dependencies are inferred from the claim text.