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Патент USA US3078577

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Feb. 26, 1963
H. A. FROMSON
3,078,567
METHOD OF FORMING THIN-WALLED METAL TUBING
Filed March 5, 1958
2 Sheets-Sheet 1
TE‘
ATTORNEYS
Feb. 26, 1963
H. A. FRoMsoN
3,078,567
METHOD OF FORMING THIN-WALLED METAL TUBING
Filed March 5, 1958
2 Sheets-Sheet 2
4 III
BY
tinned States Patent
ice
g?wggb'l
Patented Feb. 26, 1953'
1
2
3,078,567
site points of reduced wall thickness. The collapsing of
the tube may be accomplished by passing the tube between
METHQED 3F FQRMENG THltN~WALLED
METAL TUBING
Howard A. Frornson, Rogues Ridge Road, Weston, Conn.
Filed Mar. 5, 1958, Ser. No. 719,236
5 Claims. (ill. Z9--5/t4)
a. set of conventional compression rolls.
The collapsing
of the tube in this manner brings the opposing interior
surfaces of the tube into contact with each other along
a line or ?ssure 3, the ends of which are located at the
points of reduced wall thickness.
The present invention relates to a method of forming
After the tube has been collapsed, as shown in FIG. 2,
thin-walled tubing and relates, more particularly, to a
it is then rolled in lengthwise direction parallel to its
method of forming thin~walled metal tubing in one piece 10 axis. The rolling elongates the collapsed tube to a
and long lengths.
ribbonlike strip, as shown in. FIG. 3, and is continued
Au obiect of the invention is the formation of such
until the thickness of the ribbonlike strip has been re
tubes by a cheap and efficient method with maximum
duced to twice the desired wall thickness of the ?nal
efficiency in the use of the metal.
thin-walled tube or article. Such rolling will not cause
A further object of the invention is the production 15 appreciable increase in the width of the collapsed tube
of thin-walled tubing by combining extrusion techniques
which enable hollow shapes to be formed easily, with
rolling techniques which provide a maximum of e?iciency
in reducing the thickness of the extruded shapes.
or in the transverse dimension of the ?ssure. Thus, when
the ribbonlilce strip is erected to tubular shape, the in
ternal diameter thereof will be substantially the same as
the internal diameter of the preformed tube.
,
Further objects will become apparent from the follow 20
The ribbonlike strip may be readily erected as one
ing description and by reference to the accompanying
piece thin~walled tubing, as shown in FIG. 4, by inserting
drawings. The ?gures are schematic in the sense that
a needle into the ?ssure between the opposing interior
they are not to scale, it being deemed of more importance
surfaces of the ribbonlike strip and forcing fluid under
to illustrate the principles involved than dimensional
pressure into the ?ssure and ‘between the opposing inte—
details. in the accompanying drawings:
25 rior surfaces while the ends of the strip are held closed.
FIG. 1 is a perspective view of an extruded tubular
If the thickness of the strip after reduction is equal
member;
to twice the thickness of the preformed tube at the points
‘P16. 2 is a perspective View of the tubular member
of reduced wall thickness, the ?nal thin-walled tube will
shown in ‘PEG. 1 after it has been collapsed;
have substantially smooth sides. However, where the
FIG. 3 is a perspective view of the tubular member
thickness of the strip is less than the thickness of the
shown in FIG. 1 after it has been collapsed and rolled
preformed tube at the points of reduced wall thickness,
into a flat ribboniike form;
radially extending ?ns 4 will extend along opposite sides
FIG. 4 is a perspective view of a thin-walled tube
of the thin-walled tubing.
formed from the flat ribbonlike form shown in FIG. 3;
It will be understood that the tubing may be shipped
FIG. 5 is an end view showing a collapsed tubular 35 or stored while it is in the form of a ribbonlike strip for
erection as desired at the point of use. .The ribbonlike
FIG. 6 is a perspective View of an extruded tubular
strip may be readily coiled in any desired lengths and
member shaped to provide a ?at member of a substan—
it is much easier to handle in this form and less subject
member such as illustrated in FIG. 2 being rolled;
tially rectangular cross-section when collapsed;
to damage than coils of thin-walled tubing.
7FIG. 7 is an end View showing the tubular member of 40
In order to avoid cracking or tearing of the collapsed
FIG. 6 collapsed between two rolls.
tube at its edges as it is rolled to the ribbonlike strip,
FIG. 8 is an end view of another form of collapsed
certain conditions must be observed. One of these condi
tubular member suitable for use in accordance with the
tions is that the opposing interior surfaces of the collapsed
present invention.
tube de?ning the ?ssure must be brought into contact
FIG. 9 is an end View of another form of extruded
with each other and be under compression as indicated by
tubular member suitable for the production of thin-walled
the arrows A in FIG. 5 before the metal at the edges of
seamless tubing in accordance with the present invention;
the tube; i.e., beyond the ends of the ?ssure, has been
HQ. 10 is an end view of the tubular member shown
elongated beyond the percentage of elongation for the
in FIG. 9 after being collapsed and partially elongated
metal from which the preformed tube is made as de?ned
and reduced in thickness;
50 by the standard handbooks. For example, the nominal
FIG. 11 is an end view of the collapsed tubular mem
percentage of elongation for soft temper aluminum in
ber of FIG. 10 after elongation and reduction to a desired
alloy 3003 is 25%.
wall thickness;
To insure that the above condition is satis?ed, the
R6. 12 is an end view of the member shown in
points of reduced wall thickness 2 for the preformed
PEG. 11 after expansion.
tube 1 may be calculated as follows:
Accordinc to the present invention, use is made of a
If e, the percentage of elongation of the metal used is
preformed metal tube 1, as shown in FIG. 1, which
efined by the equation
may beformed by extrusion or other suitable procedure
such as a conventional seamless tube rolling mill.
The tube 1 is formed so that it has a reduced Wall 60
thickness at two diametrically opposite points 2 on its
periphery. Preliminarily, the interior of the tube may
_
Lil-LI)
e-100<
LI
where L1 is the initial length of a tensile test specimen
and LF is the ?nal length of the same tensile test specimen
be treated with a stop-off or resist such as graphite or a
just before fracture, if Tmx_ is the maximum wall thick
heavy lubricating oil to prevent bonding of the opposed
ness at any point on the preformed tube 1, and if Tmm
interior wall portions of the tube when it is compressed 65 is the wall thickness at the points 2 of reduced wall thick
or rolled flat. However, when the tube is formed from
ness, then cracking will not occur as long as
metals such as aluminum which have an oxide formed
on the surface thereof, it may not be necessary to treat
the interior of the tube to prevent bonding of the opposed
interior surfaces.
The above equation will apply to a great many shapes.
70
As indicated in FIG. 2, the tube 1 is collapsed in a
As shown in FIG. 1, the preformed tube has a circular
plane which passes through the two diametrically oppo
outer surface and an elliptical inner surface. However, it
amass?
a
will be understood that other shapes having diametrically
opposed points of reduced thickness wiil comply with the
above equation, since the distortion incidental to rolling
makes the choice of the initial cross-section somewhat
arbitrary. As further examples, the inner surface of the
preformed tube may be circular and the outer surface may
be elliptical. Also, both inner and outer surfaces may
be elliptical, and the variations in wall thickness obtained
A
well as those composed of curved segments or segments
of circles.
It will be understood that various changes and modi?ca
tions in the procedure for making thin-walled tubing de
scribed above may be made by those skilled in the art
without departing from the scope of the invention as de
?ned by the following claims.
I claim:
1. The method of making hollow thin~walled articles
which
comprises: forming a hollow metal member hav
10
outer surfaces may be in the shape of polygons.
ing points of reduced wall thickness at two opposed points
In order to minhnize the width of the ?ns 4'.- and still
in its periphery, the wall at said points of reduced thick—
by varying their eccentricity. In addition, the inner and
observe the above conditions, a preformed tube 1’, as
shown in FIG. 6, which is shaped to present a substan
tially rectangular cross-section when collapsed and before
reduction in thickness has taken place, may be employed.
FIG. 7 illustrates the preformed tube 1' of PEG. 6 col
lapsed between rolls, and as can be seen, virtually the
whole cross'section of the tube 3.’ will be under com
pression, as indicated by the arrows B, from the beginning
ness being not less than the maximum wall thickness at
any point multiplied by the expression
where e is the percentage of elongation of the material
from which the hollow member is formed; compressing
said hollow member and collapsing it on a plane passing
of elongation. This prevents cracks developing at the 20 through the said opposed points; and rolling said com
edges during elongation and the wall thickness at points
pressed member to a ribbon-like form with unbonded in
2’ of the preformed tube 1’ may approximate the desired
ternal opposed surfaces, said rolling elongating and re
ducing the thickness of said compressed member to twice
?nal wall thickness quite closely.
From actual experience, it has been found that a tubular
the desired wall thickness of the ?nal article.
member of the shape illustrated in FIG. 9 can be formed 25
2. The method of making thin-walled tubes which com
into thin-walled seamless tubing in accordance with the
prises: forming a hollow metal member having a central
present invention with a minimum width of ?n extending
cavity and substantially constant Wall thickness; com
along the sides thereof. In fact, there will only be a
pressing the hollow mernbcr and thus collapsing its cen
small insigni?cant protuberance 4”’ extending along each
tral cavity into a ?ssure; trimming the edges of the col~
side of the thin-walled tubing which means that maximum 30 lapsed hollow member to leave a thickness of metal
el‘?ciency has been achieved in use of the metal in the
between the edge of the ?ssure and the trimmed surface
preformed tubular member.
at least as great as the desired ?nal wall thickness; and
The preformed tubular member 1”’ shown in FIG. 9 is
rolling the compressed hollow member to a ribbon-like
extruded from aluminum. The outer transverse surfaces
form wtih unbonded internal opposed surfaces, said roll
5 of the tubular member which are substantially ?at join 35 ing elongated and reducing the thickness of the ?nal.
sloping surfaces 6 at their ends which join concave sur
article.
faces 7 at the ends of the tubular member.
3. In a method of producing thin-Walled metal tubing,
Transverse surfaces 8 on the inside of the tubular mem
the steps which comprise: extending a hollow metal
ber are also ?at and join sloping surfaces 9 at their ends
member having sides de?ning a central cavity, the sides
which intersect at points spaced from the concave outer 40 of said member having a cross-sectional shape compris~
surfaces at the ends of the member by a distance approxi
ing two arcuately shaped segments enclosing said central
mately equal to the ?nal desired wall thickness of the
cavity, said segments being of substantially constant thick
thin-walled tubing.
The tubular member 1”’ as initially formed has a wall
thickness between the surfaces 5 and 8 of about 0.1875
of an inch and a wall thickness of about 0.040 at the
points 2'”.
On one pass through the rolls, the tubular member is
collapsed and is partially elongated with its thickness be
ing reduced accordingly as shown in FIG. 10. At this
time, the overall thickness of the collapsed tubular member
is about 0.140 of an inch, with the distance at points 2”’
remaining substantially the same.
A second pass through the rolls further elongates the
tubular member and reduces its thickness to twice the ?nal
desired wall thickness. On this instance its thickness is
about 0.080 of an inch as shown in FIG. 11. In this con
dition the‘ tubular member is in the ?at ribbonlike form
described above.
Thereafter the tubular member can be in?ated or ex
panded by internal pressure as and when desired, to give
the expanded tube of FIG. 12.
thickness of 0.040 inch.
This tube has a wall
A‘ similar result is possible if a'preformed tube 1” of
ness and each having concave and convex side portions
with the outer ends of the concave side portions of the
two segments being joined together at opposite side edges
of said member, said concave side portions having a thick
ness at the point where they are joined less than the thick
ness of the arcuate segments but not less than the ?nal
wall thickness of the thin-walled tubing, applying a weld
resisting material to internal surfaces of the hollow mem
ber; compressing said hollow member and collapsing it
to a flattened condition on a plane passing through the
points at which concave side portions are joined, said col
lapsed hollow member having in cross-section ?at upper
and lower surfaces and substantially straight end surfaces
extending therebetween; and rolling said collapsed mem
her in a lengthwise direction between opposing pressure
rolls and simultaneously elongating and reducing the
thickness of the collapsed member to twice the ?nal wall
thickness of the thin-wall tubing.
4. In a method of producing thin-Walled metal tubing
as de?ned in claim 3 wherein the sides de?ning the cen
tral cavity in the hollow member are hexagonal in shape.
5. In a method of producing thin-walled metal tubing,
the steps which comprise: extruding a hollow metal mcm~
her having a central cavity, said hollow member being
symmetrical in cross-section about a given plane and in
uniform wall thickness is collapsed as shown in FIG. 8 and
is then trimmed along the lines C-—C by means of slitting
rolls to leave a thickness of metal, at points 2", between
cluding two substantially rectangular portions extending
the cut edges of the collapsed tube and the outer ends
parallel to said plane on opposite sides thereof and four
of the ?ssure 3’ which is at least equal to the desired ?nal 70 substantially rectangular end portions of the same thick
ness as the central portions, each of said end portions
wall thickness of the thin-walled tubing. The remainder
being joined at one end to one of the central portions
of the tube is then processed as described above, while the
and sloping downwardly therefrom toward and joining
pieces cut therefrom can be reused.
with another of said end portions at said given plane
It will be understood that the word “arcuately” as used
with the wall thickness where said end portions join being
herein applies to arched forms such as i’” of FIG. 9' as
3,078,567
5
6
less than the thickness of the central portions but at
least equal to the wall thickness of the ?nal thin-walled
tubing; the outer edge surfaces -at the points where the
end portions join being concave in cross-section; com
pressing said hollow member and collapsing it in the
given plane to a ?attened condition; and then rolling the
collapsed hollow member in a lengthwise direction and
377,317
938,646
1,392,658
1,819,254
1,951,394
2,270,988
2,363,635
simultaneously elongating and reducing the thickness of
UNITED STATES PATENTS
185,378
Whitehouse __________ _- Dec. 12, 1876
1888
1909
1921
1931
1934
Woods ______________ __ Jan. 27, 1942
Blair _______________ _.. Nov. 28, 1944
FOREIGN PATENTS
the collapsed hollow member to a thickness equal to
twice the thickness of the ?nal thin-walled tubing.
References Cited in the ?le of this patent
Marshall ____________ __ Jan. 31,
Davis _______________ __ Nov. 2,
Roesch ______________ __ Oct. 4,
Mantle ______________ __ Aug. 18,
Chase et a1 ___________ __ Mar. 20,
10
1,467
4,794
190,585
778,422
Great Britain ___________ .._ AD. 1888
Great Britain ___________ __ AD. 1893
Great Britain _________ _._ Dec. 28, 1922
Great Britain _________ _._ July 10, 1957
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