Improvements in Metallic Tubes, and in Manufacturing the same.
Year: 1893

page_text: Date of Application, 15th Nov., 1893
Complete Specification Left, 12th Sept., 1894-Accepted, 13th Oct., 1894
PROVISIONAL SPECIFICATION.
Improvements in Metallic Tubes, and in Manufacturing the same.
I CHARLES LESLIE STIFF of No. 127 Hagley Road Birmingham in the County
of Warwick Assistant Manager of Works do hereby declare the nature of this
invention to be as follows: :-
Metallic tubes as ordinarily made have the same external diameter and the same
internal diameter throughout their whole length and have also the same thickness of
metal throughout their whole length.
For some of the purposes to which metallic tubes are applied it is desirable that
the tube while having the same external diameter throughout should have greater
strength that is greater thickness of metal at its ends than at the intermediate parts
and in some cases to have greater thickness of metal not only at the ends but at
some other parts.
My invention has for its object to manufacture tubes of the kinds referred to and
consists of the improvements hereinafter described in conducting the tube drawing
process whereby tubes having the same external diameter throughout but of
diminished internal diameter at the ends or at other parts as required are produced.
I will describe my invention as applied to the manufacture of a tube of the same
external diameter throughout and a diminished internal diameter at its ends.
In
I take a tube of larger external diameter than the tube to be eventually produced
and of a thickness of metal equal to that required at the ends of the finished tube.
I employ a draw plate of the ordinary kind. In the interior of the tube I introduce
a bulb mandril the diameter of the bulb of the mandril being equal to the diameter
of the middle part of the tube or the part having the least thickness.
commencing the drawing process the bulb of the mandril is not advanced so far
into the tube as to enter the eye of the draw plate. The drawing process being
commenced with the mandril in this position both the external and internal
diameters of the tube are reduced the thickness of metal remaining unaltered or
but little altered. When the drawing has taken place on the length of the
front end of the tube which is required to have a greater thickness of metal
than the middle portion of the tube the bulb of the mandril is advanced into the
eye of the draw plate. The drawing process being continued the external diameter
of the tube remains the same as that of the portion already drawn but the tube
being now drawn over the bulb of the mandril and through the hole in the draw
plate the thickness of metal is reduced the said thickness being equal to the annular
space between the bulb of the mandril and the hole in the draw plate. The
drawing process is continued until the required length of tubing of diminished
thickness of metal has been produced when the mandril is drawn back and the
drawing of the remainder or rear end of the tube is effected in the same way as
that of the first end, that is only the hole in the draw plate operates on the tube
its external diameter being reduced but the thickness of metal remaining the same.
From the foregoing description it will be understood that whenever the bulb of
the mandril is advanced into the eye of the draw plate the internal diameter of the
tube will be maintained and the thickness of metal of the tube diminished the
external diameter under all circumstances remaining the same.
Where short tubes having thick ends are required a long tube having thick
portions at the required intervals may be made. By then cutting the said long
tube through the thick parts a series of short tubes thick at their ends but thin at
their middle is produced.

page_text: In some cases it is necessary to reduce the length of tube between its thick ends
to a greater extent than can be conveniently done by one drawing. In this case I
manufacture the tube by two drawing processes, annealing the tube after the first
drawing process.
In the case in question I conduct the manufacture of the tube in the following
manner. Taking an ordinary tube I introduce a mandril having the diameter of
the interior of the tube. The bulb of this mandril is pushed up nearly to the draw
plate that is to a distance from the draw plate equal to the length which it is
intended the thick front end of the tube shall have. I draw the tube through the
draw plate until the front thick end has passed the draw plate. I then push the
mandril further into the tube until its bulb is situated in the eye of the draw plate.
The drawing of the tube is then continued until the rear end of the tube has nearly
reached the draw plate the portion of the tube to constitute the thick rear end
being unoperated upon. There is thus produced a tube less in external diameter
except at its rear end than the original tube, that is, there is produced a tube
thick at its front end and of diminished internal diameter at that end and having
throughout the remainder of its length the same original internal diameter, the rear
end having the original diameter and thickness of metal. After annealing the tube
is passed through a smaller plate with the same mandril in it the said mandril being
pushed up to the front internal shoulder. The tube is then drawn until the rear
external shoulder is reached; the mandril is then drawn out of the tube and the
drawing continued. This last stage of the drawing process forces the thick rear
end inwards and makes the tube of the same external diameter throughout.
Dated this 15th day of November 1893.
W. T. WHITEMAN,
Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Metallic Tubes, and in Manufacturing the same.
I, CHARLES LESLIE STIFF, of No. 127 Hagley Road, Birmingham in the
County of Warwick, Assistant Manager of Works, do hereby declare the nature
of my invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
Metallic tubes as ordinarily made have the same external diameter and the same
internal diameter throughout their whole length and have also the same thickness
of metal throughout their whole length.
For some of the purposes to which metallic tubes are applied it is desirable that
the tube while having the same external diameter throughout should have greater
strength; that is, greater thickness of metal at its ends than at the intermediate
part and in some cases to have greater thickness of metal not only at the ends but
at some other parts.
My invention has for its object to manufacture tubes of the kinds referred to and
consists of the improvements hereinafter described in conducting the tube drawing
process whereby tubes having the same external diameter throughout, but of
diminished internal diameter at the ends, or at other parts, as required, are
produced.
I will describe my invention as applied to the manufacture of a tube of the same
external diameter throughout and a diminished internal diameter at its ends.
I take a tube of larger external diameter than the tube to be eventually produced
and of a thickness of metal equal to that required at the ends of the finished tube. I
employ a draw plate of the ordinary kind. In the interior of the tube 1 introduce
a bulb mandril, the diameter of the bulb of the mandril being equal to the diameter
of the middle part of the tube or the part having the least thickness of metal. In
commencing the drawing process the bulb of the mandril is not advanced so far into

page_text: the tube as to enter the eye of the draw plate. The drawing process being
commenced with the mandril in this position both the external and internal
diameters of the tube are reduced, the thickness of metal remaining unaltered.or
but little altered.
When the drawing has taken place on the length of the front end of the tube
which is required to have a greater thickness of metal than the middle portion of
the tube, the bulb of the mandril is advanced into the eye of the draw plate. The
drawing process being continued the external diameter of the tube remains the same
as that of the portion already drawn but the tube being now drawn over the bulb of
the mandril, and through the hole in the draw plate, the thickness of metal is
reduced, the said thickness being equal to the annular space between the bulb of the
mandril and the hole in the draw plate. The drawing process is continued until
the required length of tubing of diminished thickness of metal has been produced,
when the mandril is withdrawn and the drawing of the remainder or rear end of
the tube is effected in the same way as that of the first end, that is, only the hole
in the draw plate operates on the tube, its external diameter and internal diameter
being reduced but the thickness of metal remaining the same.
Where short tubes having thick ends are required a long tube having thick
portions at the required intervals may be made. By then cutting the said long tube
through the thick parts, a series of short tubes thick at their ends but thin at their
middle is produced.
In some cases it is necessary to reduce the strength of tube between its thick
ends to a greater extent than can be conveniently done by one drawing.
In this case I manufacture the tube by two or more drawing processes, annealing
the tube after the first drawing process.
In the case in question I conduct the manufacture of the tube in the following
manner. Taking an ordinary tube I introduce a mandril having the diameter of
the interior of the tube. The bulb of this mandril is pushed up nearly to the draw
plate, that is, to a distance from the draw plate equal to the length which it is
intended the thick front end of the tube shall have. I draw the tube through the
draw plate until the front thick end has passed sufficiently through the draw plate.
I then push the mandril further into the tube until its bulb is situated in the eye of
the draw plate. The drawing of the tube is then continued until the rear end of
the tube has nearly reached the draw plate, the portion of the tube to constitute the
thick rear end being unoperated upon. There is thus produced a tube less in
external diameter except at its rear end than the original tube; that is, there is
produced a tube thick at its front end and of diminished internal diameter at that end
and having throughout the remainder of its length the same original internal
diameter, the rear end having the original diameter and thickness of metal.
The tools having been removed and the tube annealed, the said tube is passed
through a smaller plate with the same mandril in it, the said mandril being pushed
up to the front internal shoulder. The tube is then drawn until the rear external
shoulder is reached; the mandril is then withdrawn from the tube and the drawing
continued. This last stage of the drawing process forces the thick rear end inwards
and makes the tube of the same external diameter throughout.
I will first describe with reference to the accompanying drawings the manufacture
of a steel tube of the same external diameter throughout and having greater
thickness of metal at its ends, but of diminished internal diameter at the said ends,
tubes of the said manufacture being suitable for steam boilers, condensers
refrigerators and the like.
In carrying my invention into effect I take a tube of the kind represented in
longitudinal section in Figure 1 made by the ordinary drawing processes and
provided with the ordinary nozzle end a. This tube has a larger external diameter
than is required in the finished tube to be made, and has a thickness of metal equal
to that required at the ends of the finished tube.
Figure 2 represents in longitudinal section the partly made tube after the front
,end 6 has been reduced in external diameter. To effect this, I use a draw plate c

page_text: of the ordinary kind, the hole in the said plate having the same diameter as the
external diameter of the tube to be made and I also use a bulb mandril d of the
ordinary kind, the diameter of the bulb of the mandril being equal to the diameter
of the thin middle part or body of the tube.
In producing the front end b, the bulb of the mandril d has the position in the
tube represented in Figure 2, that is does not enter the eye of the draw plate and the
draw plate c is situated at the front shoulder 63 of the tube. On the tube Figure 2
being drawn through the draw plate e in the direction indicated by the arrow, with
the mandril d in the position represented, both the external and internal diameters
of the tube at the front end bare reduced by the action of the draw plate c alone,
the thickness of metal of the said front end being practically unaltered.
C
The required length of the front end of the tube to form the front thick end of
the tube having been produced as represented in Figure 2 and marked b, the bulb
of the mandril d is advanced into the eye of the draw plate c at the back
shoulder and the drawing process is continued to produce the thinner middle
part or body of the tube. By the drawing of the tube over the bulb of the
mandril d and through the hole in the draw plate c the thickness of metal at the
drawn part is reduced as represented in longitudinal section in Figure 3 where
the thinning of the middle part of the tube is being performed, the thickness of the
portion of the tube marked e now being drawn being equal to the annular space
between the bulb d and the hole in the draw plate c as will be understood by
an examination of Figure 3, the external diameter of the tube remaining the same
as that of the portion already drawn.
Figure 4 represents in longitudinal section, the tube after the middle part e of
reduced thickness of metal has been produced by the action of the combined draw
plate and bulb mandril. After the required length of tubing of reduced thickness
of metal ate has been produced, the mandril d is withdrawn from out the eye of
the draw plate e and the drawing of the rear end of the tube is now continued
through the draw plate only, for producing the thick rear end of the tube as
represented in Figure 4, the said thick rear end being produced in the same way
as that of the front thick end b; that is, by the action of the draw plate alone;
the external diameter and internal diameter of the tube is reduced, but the
thickness of metal at the said rear end remains practically the same.
From the foregoing description it will be understood that whenever the bulb
of the mandril d is advanced into the eye of the draw plate c the internal diameter
of the tube will be maintained and the thickness of metal of the tube diminished,
the external diameter of the tube under all circumstances remaining the same.
By the process described and illustrated a tube is produced having the same
diameter throughout and having greater thickness of metal at its ends b, d².
Should the tube require an intermediate thick part or parts, the drawing operation
by the combined draw plate and mandril is arrested at the required part and the
draw plate only is used, the mandril being again advanced when sufficient of the
thick part has been drawn.
Figure 5 represents in longitudinal section a tube produced by the drawing
process hereinbefore described to be used for the manufacture of a series of short
tubes having thick ends. In the said Figure 5, a thick part badjacent to a thin
part e is followed by a thick part d' which is followed by another thin part f, which
part is represented in the act of being produced by the draw plate c and bulb
mandril d. Any number of these alternating thick and thin parts may be produced
in the tube. By cutting a long tube of this kind through the middles of the thick
parts b, and the other parts, a series of short tubes thick at their ends but thin
at their middles is produced.
In producing tubes having thinner middle parts than can be conveniently done
by one drawing process I proceed in the following manner. 1 first produce a
partly made tube of the kind represented in Figure 6 having a thick front end and
a thinner part adjacent thereto in the manner hereinbefore described with respect
to Figure 3. Both draw plate and mandril having been withdrawn aud having

page_text: annealed the partly made tube Figure 6, I take the mandril d, the bulb of which
has the same diameter as the internal diameter of the thinnest part e of the tube,
and I push the said bulb up to the internal shoulder 6 of the tube as indicated in
dotted lines in Figure 6 and I use a smaller draw plate h in conjunction with the
said bulb mandril d as represented in Figure 7.
The tube Figure 6 is first drawn through the smaller draw plate until the
internal shoulder is reached when the bulb of the mandril d is introduced into
the eye of the draw plate h at the shoulder 3. By now drawing the tube through
the combined draw plate and bulb mandril d as represented in Figure 7, the
thickness of metal at the parte of the tube is reduced as will be understood by an
examination of Figure 7, where the middle part of the tube having reduced
thickness is marked i. This thinning operation inay be repeated one or more times
by the use of smaller draw plates. As soon as the rear external shoulder say at k
has been reached the mandril d is withdrawn from the tube and the drawing
continued from the shoulder k by the draw plate 4 only, as represented in Figure 8.
This stage of the drawing process forces the thick rear end inwards and makes
the tube of the same external diameter throughout as seen in that part of the tube
which has been operated upon by the draw plate h in Figure 8.
When the reduction of the metal of the middle part of the tube has been effected
by the use of several drawings effected by draw plates of different diameters in
conjunction with a mandril of the same diameter, the back end Figure 8 of the
tube, which still retains its original diameter, is of too great a diameter to be finally
reduced by one drawing operation.
In this case, it is necessary to gradually reduce the thick back end 7 by drawing
it in succession through two or more draw plates having eyes of progressively
diminishing diameters, the tube being annealed after each drawing operation if
desirable.
Having now particularly described and ascertained the nature of my invention
and in what manner the same is to be performed, I declare that I claim as my
invention of "Improvements in metallic tubes and in manufacturing the same,'
"
First. Manufacturing metallic tubes, having the same external diameter
throughout and of diminished internal diameter, or of greater thickness of metal,
at their ends, or at other parts, by conducting the drawing process in the manner
substantially as herein before described and illustrated in Figures 1, 2, 3 and 4 of
the accompanying drawings; that is to say, taking a tube of larger external
diameter than the tube to be made, and of the thickness of metal equal to that
required at the ends (or other thick parts) of the finished tube; drawing the tube
at its front part through a draw plate in conjunction with a bulb mandril, having
the respective positions represented in Figure 2 so as to reduce the external and
internal diameters at the front end of the tube and produce the front thick end of
the tube; next advancing the bulb of the mandril into the eye of the draw plate as
illustrated in Figure 3, and continuing the drawing process over the bulb of the
maudril and through the hole in the draw plate so as to reduce the thickness of
metal of the tube at the middle or body part thereof and finally producing the
thick rear end of the tube by the process described with respect to the front end
substantially as described and represented.
Secondly. The method herein before described and illustrated in Figures 6 and 7
of the accompanying drawings of reducing the strength or thickness of metal
between the thick ends of the tubes or at the reduced middle part; that is to say
subjecting the partly made tube after the stage represented in Figure 3, to one or
more further drawing operations with the bulb of the mandril within the eye of
the draw plate, the diameter of the bulb of the mandril being the same as that
employed in the early stage of the manufacture the draw plates used in the several
additional drawing stages having holes of progressively diminishing diameters
substantially as described.
Thirdly. Reducing the diameter of the back end of the tube after the treatment

page_text: of the tube by the process referred to in Claim 2 by the use of a smaller draw
plate or a series of draw plates of progressively diminishing diameters as herein-
before described and illustrated with reference to Figure 8 of the accompanying
drawings.
Lastly. Manufacturing short tubes having thick ends by the process described
and represented with respect to Figure 5, and cutting the long tube through at the
thick parts to produce short tubes of the kind described.
Dated the Seventh day of September 1894.
CHARLES LESLIE STIFF.