Note: Descriptions are shown in the official language in which they were submitted.
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"Method and Apparatus for Producing Seamless Tubes"
This invention relates to a method of making
thin-walled seamless tubes and to an apparatus ~or
carrying out the method.
There has not, here~ofore, been any possibili~y
of forming bends in one-piece thin-walled seamless
sheet-metal tubes. Thick-walled drawn elbows and other
curved tube pieces have the disadvantage that in the
bent area the tube diameter changes from the normal
lO diameter, due to the upse~ting which occurs on the
outer side o the bend, so that exac~t maintenance of
the dimensions and precision in the shaping are im-
possible. Such elbows as are used, for example, as
part of downspouts on houses, are therefore mostly
still made of two parts which are connected by welding
or otherwise. If made of one piece and then bent, they
develop large, unsightly ribs which are the result o~
upsetting at the inner side of the bend.
The present invention seeks to overcome the
~0 disadvantage of the p~ior art, and to provide a me~hod
of, and an apparatus for, forming bends in thin-walled
tubes while main~aining the exact desired shape and
dimensions. Further, the surface of the bent tube is
to remain smooth. The tube bends may be made with
or without cylindrical extensions and o~ a variety ~`
of metals such as iron, copper, brass,
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aluminum, zinc and othersO They may have a wall thick-
ness of about 105 mm or mored down to about 0.2 mm.
Pursuant to the invention, a thick-walled short
tubular blank is placed onto a core or mandrel which
determines the shape of the desired bend, and is then
moved between pressure rollers which rotate and also
orbit about the blank; these cause the material of the
blank to flow ànd thereby convert the blank into a
thin-walled bent tube section having the desired shape
Io and being provided with a smooth surfaceO While the
blank is moved between the rollers, these are adjusted
so as to move radially towards one anotherO
The invention permits the conversion of a thick-
walled blank into a bend having a wall thickness of
about 0O2 to 1O5mmO The radius of curvature of the
bend may be selected as desired, and the same is true
of the base angle and tube diameterO The surface of
the finished bend will be completely smooth and without
any seam, the desired shape will be achieved with
~O complete accuracy, and the selected diameter will be
fully maintainedO
If it is desired to produce the already formed
bend with cylindrical extensions, a cylindrical
mandrel is secured to one or both ends of the curved
mandrel, and a support of the apparatus is then
shifted parallel to the axis of the swaging head
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carrying the pressure rollers, so as to form the desired
extensions. It follows from this, incidentally, that the
present invention also makes it possible to convert
thick-walled tubes (serving as blanks) into thin-walled
cylindrical tubes without bends. In no event do the
blanks themselves rotate; they are only subjected to
pressure causing their material to flow, by the radiall~
adjustable pressure rolls which orbit the blanks.
In accordance with one aspect of the invention there
is provided a method of making thin-walled seamless tubes,
comprising the steps of placing a short, thick-walled
tubular blank onto an arcuately curved mandrel; moving the
blank and mandrel between driven pressure rollers of a
swaging head; and orbiting the head and rollers about the
blank and deforming its material to cause the same to flow
and accomodate itself to the shape of the mandrel; and
placing a cylindrical mandrel against one end of the
cur-ved mandrel; and shifting the blank and mandrels
lengthwise of the orbiting axis of the swaging head 50 as
to form over the cylindrical mandrel a cylindrical
extension on the bent tube.
In accordance with another aspect of the invention
there is provided an apparatus for making thin-walled
seamless tubes, comprising mandrel means for supparting a
short, thick-walled tubular blank; a swaging head including
a plurality of driven pressure rollers movable radially
towards and away from one another; means for moving the
! mandrel means and supported blank between the rollers;
means for orbiting the rollers about the mandrel means in
pressure-exerting contact with the blank so as to cause
the material thereof to flow and become converted into
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a thin-walled tube corresponding in shape and diameter to
the mandrel means; and a base on which said means and
swaging head are mounted, said mandrel means including a
support pivotable on said base about a vertical axis, and
an arcuately curved mandrel on said support.
The invention will now be explained with reference to
an exemplary embodiment whlch is illustrated in the
appended drawings, but which is not to be considered
limiting in any sense.
FIG. 1 is a side view illustrating a machine for
carrying out the method;
FIG. 2 is a top plan view thereof;
FIG. 3 is a view similar to the one in FIG. 2, but
with the swaging head omitted;
FIG. 4 is a longitudinal section through the swaging
head and support therefor;
FIG. 5 is a front elevation of the swaging head;
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FIGO 6 iS a plan view o~ a blank to be deformed;
FIGD 7 is an end perspective of the same blank; and
FIGO 8 iS a plan view o~ an article produced from
the blank in FIGSO 6 and 70
Referring~ now to the drawing in detail, it will
be seen that the machine has a base 1 and a frame 20
An electric mo~or 3 is mounted on the base I and serves
to drive the swaging head 40
The head 4 is turnably mounted on frame 2 via
l~ a hollow shaft 5 and bearings 6, 70 A push rod 8 iS
received in shaft 5 in which it can slide axially but
not turn; it is actuated by a cylinder and piston 9
which may be hydraulic or pneumatic, or in some other
suitable mannerO The free end of ~he push rod 8 extends
into the swaging head 4 (FIGO 4) where it carries a
removable cylindrical core or mandrel 10 which can be
replaced by other cores having different diametersO
Rod 8 is guided in bearings 11 and a reciprocable
cylinder 12 is mounted on the swaging head ~, which is
reciprocable mechanically or in any other suitable man-
ner, as indicated by the double-headed arrow l3D
Cylinder 12 has a conical inner part 14 which controls
three pressure rollers 15 that are arranged in a star-
shaped pattern in head 4 and can be moved radially
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towards and away from one anotherO Rollers 15 are
mounted on rods 16 which may be eOgO spring-loaded,
so that the free ends of the rods 16 abut the inner
surface of part 140 Rollers 17 may be provided, to act
upon a ~lange 18 so as to move the cylinder 12 on the
head 40
A cross-slide 19 is located beneath the head 4
and movable along rods 20 of the frame 2 lengthwise
of the frame; its upper part 21 is movable cross-wise
of the frame and carries a vertical shaft 22 which,
in turn, carries a support 23 for a replaceable curved
mandrel 240 The thick-walled tubular blank 25 is placed
onto this mandrel 240 The pivoting radius R of the
support 23 can be shortened or lengthened (by replacing
the support with another one and shifting the part 21
cross-wise via utilization of slots 26 therein) to
permit selection of different desired bending ratios
and tube diame~ersO An electric motor 27 drives the
support 23 via a transmission 28, to impart to the
ao mandrel 24 a pivoting movement R in direction of the
head 4 and the rollers 150 Cross-slide l9 is coupled
with a rod 30 which is powered by a hydraulic or
pneumatic cylinder 29 or else is movable electrically
or manuallyO -
An ejector 31 is provided which is pivotable on
the part 21 of the cross-slide 19 and serves to eject
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the finished thin-walled bend (tubular article) 33
from the mandrel 240 E~ector 31 has a free end formed
with e~gO a bifurcated part 32 which engages one end
of the finished article 33 at 360 Pivoting of ejector
31 in direction of the bend radius pushes article 33
off the mandrel 24 after the cross slide 19, 21 is
moved away from the head 4 with rod 30 and support 230
It may be desired for the bend 33 to have cylin-
drical extensions 24D If so, the mandrel 10 must be
/0 applied to one end of the mandrel 240 The m~ndrel 10
is then moved against the end of mandrel 24c The cylin-
drical extension may have the same diameter:as the
bend 33, or its diameter may be larger or smaller
(in which case a mandrel 10 of appropriate diameter
must be installed)0 To form the cylindrical extension 34
the unit 9 is operated to shift the cross slide 19
lengthwise; the unit 29 may cooperate or may simply
be taken along as the slide moves and the rollers de-
form the material of the blank to form the cylindrical
a o extensionO
The change of the radius R when an article having
a different radius of bend than before is to be produced,
could also be effected by constructing the arm 25 of
support 23 so that it can be lengthened or shortened.
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FIG D 8 shows that the Einal article produced
from the blank 25 in FIGSo 6 and 7 is formed of one
piece and has a completely smooth and seamless surfaceD
It has precisely the desired shape and exactly the
desired diameterO The tubular extensions 24 may have
the same diameter, or a smaller or larger diameter and
the wall thickness may, depending upon the intended
use, be between about 002 ànd about 105mmO
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