Year: 1897

page_text: Date of Application, 30th Apr., 1897-Accepted, 3rd, 1897

page_text: plate and tube being such that as the tube is drawn through the said die plate it will
be pressed onto this mandrel and will conform to the shape of the same, the tube
and mandrel being drawn forward as a unit.
The mandrel is of incompressible material, preferably of hardened steel.
As the mandrel travels with the tube, therefore, there is no friction such as is
caused by drawing the tube between two fixed opposing surfaces, such as a die plate
and an internal ball, or mandrel, but only the friction caused by the compression of
the tube upon the travelling mandrel, hence much greater reductions in the thickness
of the tube are possible than are possible by the ordinary method of procedure, for
instance, I have in practice produced at one draft a tube varying in thickness at
different parts of its length to the extent of five, or six, gauges.
After the tube, with its internal mandrel, has been drawn through the die plate it
becomes necessary to remove the mandrel from the tube and in order to effect this,
especially where the tube is thickened or reduced in thickness at points between its
ends, it becomes necessary to expand the tube until its portion of least internal
diameter can be drawn from the mandrel. This may be done by hammering the tube
so as to effect the desired stretching of the metal, the aim being to effect the
substantially uniform expansion of the tube from end to end. The expanded tube
after being drawn off the mandrel, is then drawn through a die plate of proper
aperture and without an internal ball, or mandrel, whereby the diameter of the tube
is reduced to the desired extent and the outer surface of the tube has the proper
finish imparted to it, this reduction in the diameter of the tube effecting no
appreciable change in the thickness of the walls of the tube, but causing simply a
slight elongation.
It will be evident that in carrying out my invention, a tube of any desired internal
conformation can be produced; for instance, the tube may be thicker, at one end than
at the other end, or it may be thicker, or thinner, at the ends than at a part, or parts,
between the ends, as many variations as desired in the thickness of the walls of the
tube being made between the opposite ends of the tube, and the change in thickness
being either gradual, or abrupt, as required. The external surface of the tube may
be either cylindrical, or tapering, as desired.
My invention is of especial value in the formation of tubes with internal ribs. One
such form of tube is shewn in Figures 7 to 10, the tube there shewn being tapering,
although it may be of uniform external diameter throughout if desired.
This tube has internal ribs a, deepest at the ends of the tube, and gradually tapering,
or lessening, in depth, until they merge into the body of the tube some distance from
each end, the purpose of these internal ribs being to stiffen and strengthen the end
portions of the tube, the increased strength being graduated to accord with the
strains to which the different parts of the tube are subjected in use. It will be evident
therefore that any desired arrangement of internal ribs may be adopted with the
object of strengthening any required part, or parts, of the tube. The ribs may in
some cases extend throughout the tube from end to end.
In this case, as in the tube shown in Figures 3 to 6, there is a material difference
in the thickness, or gauge, of the tube at different parts of its length, the increased
thickness in the tube, Figure 7, being in the form of ribs instead of in the form of
a thickening of the tube, throughout its entire cross section.
My invention has been especially devised for the manufacture of seamless drawn
tubes of steel, but it may be used in the manufacture of tubes of iron, copper, brass
or other material with like good results.
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 :-
1. The process herein described of making seamless metal tubes having walls of
varying thickness, the said process consisting in inserting in a tube, before drawing
the same, a mandrel having an external configuration similar to that of the desired
internal configuration of the drawn tube, and then drawing both tube and mandrel

page_text: through the die plate so as to cause the tube to be compressed upon the mandrel and
to conform interiorly to the external shape of said mandrel, substantially as
herein before explained.
2. The process herein described of making seamless drawn metal tubes having
walls of varying thickness, the said process consisting in inserting in a tube, before
drawing the same, a mandrel having an external configuration similar to that of the
desired internal configuration of the drawn tube, then drawing both tube and mandrel
through a die plate so as to cause the tube to be compressed upon the mandrel and
to conform interiorly to the external shape of the mandrel, and then expanding the
tube and withdrawing the mandrel therefrom, substantially as herein before explained.
3. The process herein described of making a seamless drawn metal tube with walls
of varying thickness, the said process consisting in inserting in a tube, before the
same is drawn, a mandrel having an exterior configuration similar to the desired
interior configuration of the drawn tube, then drawing both mandrel and tube through
a die plate so as to cause the tube to be compressed upon the mandrel and conform
interiorly to the external shape of the said mandrel, then expanding the drawn tube
and removing the mandrel therefrom, and then passing the expanded tube through an
open die plate whereby it is reduced in diameter and a surface finish is imparted to
it, substantially as hereinbefore explained.
4. As a new article of manufacture, a seamless drawn metal tube, having walls of
varying thickness, the difference in gauge between the thick and thin portions of the
tube exceeding two guages, substantially as hereinbefore explained.
5. The herein before described mandrel for tube drawing machines, the said mandrel
having a length equal to that of the tube to be drawn and an external configuration
conforming to that of the desired internal configuration of the drawn tube.
6. As a new article of manufacture a seamless drawn metal tube having internal
ribs as hereinbefore explained.
7. As a new article of manufacture a seamless drawn metal tube, having internal
ribs tapered or graduated in depth as hereinbefore explained.
Dated this 30th day of April 1897.