An Drawing OD.
Year: 1886

page_text: Date of Application, 8th Nov., 1886.
Complete Left, 6th Aug., 1887.
Complete Accepted, 6th Sept., 1887.
An improvement Drawing OD.
I, BENJAMIN CHEW TILGHMAN, of Altrincham, in the County of Cheshire, Engineer,
do hereby declare the nature of this invention to be as follows:-
My invention relates to the process of drawing metal tubes, particularly those
having thick walls or sides, which are difficult to draw by the ordinary process
because the compressive action of the dies is mostly confined to the surface layers of
metal and has comparatively little direct effect upon the interior. The surface layers
are first elongated by the compression and in elongating they partly slide over the
central portion and partly draw it with them, and this causes an unfavourable state of
strain in the metal, the surface layers pulling and the central part resisting. The
thicker the walls of the tube the more does this difficulty occur.
My invention consists in applying a powerful longitudinal tension to the whole
length of the tube during the drawing process so as to keep the metal continuously in
a state of elastic elongation.
When the dies, (either exterior dies or interior mandrils, or both together) are then
passed over the tube their compressive action is greatly assisted by the pre-existent
independent elastic elongation of the metal. The surface layers of metal in contact
with the dies become permanently elongated by the compression, and the longitudinal
tension is thus concentrated upon the central portion at that point, which then becomes
permanently elongated conformably to the surface layers. The whole area of the
metal being kept in a state of elastic elongation, which may be nearly up to the
point of permanent elongation, the addition of the compressive action of the dies
at each successive point causes the permanent elongation to take place at that
point, with less expenditure of force, less pressure and wear of dies, and less
unequal strain on the metal than is the case in the ordinary process of drawing.

page_text: It is to be understood that the tension which gives the elastic elongation to the
tube is independent of the force which pulls it through the dies; the latter acts
only on that part of the tube which has passed through the dies, the former acts on
its whole length. The tension should be continuous so as to immediately take up
the elongation produced. I generally work at common atmospheric temperatures but
heat not exceeding 300 or 400 Fah. may be applied.

page_text: An Improvement in Drawing Metal Tubes.
I, BENJAMIN CHEW TILGHMAN, of Altrincham, Cheshire, Engineer, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
My invention relates to the process of drawing metal tubes, particularly those
having thick walls or sides, which are difficult to draw by the ordinary process,
because the compressive action of the dies is mostly confined to the surface layers of
metal and has comparatively little direct effect upon the interior. The surface layers
are first elongated by the compression and in elongating they partly slide over the
central portion and partly draw it with them, and this causes an unfavorable state of
strain in the metal, the outer layers pulling and the central part resisting. The
thicker the walls of the tube the more does this difficulty occur.
My invention consists in applying a powerful longitudinal tension to the whole
length of the tube during the drawing process so as to keep the metal continuously
in a state of elastic elongation. When the dies, either an exterior die or an interior
die or mandril, or both together, are then passed over the tube, their compressive
action is greatly assisted by the pre-existent and independent elastic elongation of the
metal. The surface layers of the metal become permanently elongated by the
compressive action of the dies, and the longitudinal tension is thus concentrated upon
the central portion at that point, which then becomes permanently elongated
conformably to the surface layers. The whole area of the metal being kept in a state
of elastic elongation which may be nearly up to the limit of permanent elongation,
the addition of the compressive action of the dies at each successive point causes the
permanent elongation and other change of shape to take place at that point with less
expenditure of force, less pressure and wear of dies, and less unequal strain on the
metal than is the case in the ordinary process of drawing.
It is to be understood that the tension which gives the elastic elongation to the
tube is independent of the force which pulls it through the dies; the latter acts only
on that part of the tube which has passed through the dies, the former acts on its
whole length. The tension should be continuous so as to immediately take up the
elongation produced.
The following is a method of carrying my invention into effect. The ends of the
tube having been sufficiently reduced in size to admit the dies to be slipped on, are
to be gripped in a hydraulic or other suitable pulling press and a longitudinal tension
is to be applied which may be nearly or about up to the elastic limit of the metal.
The dies, either exterior or interior or both together, are then to be drawn over or
through the tube, so that the metal is subjected at the same time to the surface
compression of the dies and the longitudinal tension of the press.

page_text: The machine described and drawn in the Patent granted to me July 20th 1886,
No. 9382, may be conveniently used for this purpose, but I do not confine myself
thereto.
Any form of machine may be used which will give the requisite longitudinal tension
to the tube, and the motion to the dies. I prefer to give the motion to the dies, while
the tube is held fast, but if desired the dies may be held and the tube be drawn through
or over them.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I declare that what I claim is,
The process of drawing metal tubes by the application of independent longitudinal
tension simultaneously with and in addition to the force which draws the dies over or
through the tubes, substantially as described.