Note: Descriptions are shown in the official language in which they were submitted.
84111903
TUBULAR CORE AND METHOD
BACKGROUND OF THE INVENTION
The words "pipe" and "tube" are used interchangeably here.
This invention relates to relatively small diameter pipes or tubes and in
particular to tubular
cores on which sheets of metal or other material can be wound for shipment,
handling and
dispersal. As used here, the word dispersal includes mounting a core and a
sheet wound
thereon on an uncoiler, then rotating the core to unwind the sheet and feed
the sheet to
apparatus for forming the sheet into other goods (beverage cans, automotive
body parts, etc.).
Cores comprising paper or cardboard and glue are widely used for the above
purposes. For
example, beverage can stock material can be manufactured using cores which are
formed to
various diameters, for example, inside diameters of 16", 20" or 24", from
paper fiber about
0.5" to 1" thick. These cores are non-recyclable and must be disposed of in
dumps or landfills,
with the attendant cost and detrimental impact on the environment. These cores
can be
crushed to facilitate storage and disposal, but this can be a problem because
of their bulk and
the difficulty in crushing them.
Tubes or pipes formed from metal strips are known in the art. See, for
example, commonly
assigned US patent nos. 3,940,962 and 3,247,692 in the name of Paul K. Davis,
which disclose
the so-called three-roll free forming method and apparatus for forming pipes.
According to
these patents, an elongated strip of metal is advanced in a generally planar
path along its
longitudinal axis and into forming stands which form the strip into a profile,
then the profiled
strip is fed into a tube forming machine at which the strip is curled or
wrapped between three
sets of rollers (lead, mandrel and buttress rollers) into helical tubes. The
sets of rollers extend
in rows at an angle relative to the longitudinal axis of the incoming strip,
the helix angle, which
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is so related to the radius of the helical convolutions and the width of the
incoming
strip that the trailing edge of a preceding portion of the strip converges
into contact
with the leading edge of the following portion of the strip. The '962 patent
also
teaches diameter control. The tubes formed in accordance with the '692 and
'962
patents are used in a variety of applications. US patent nos. 3,940,962 and
3,247,692.
Metal tubes or pipes have the potential for use as small diameter recyclable
cores,
but to date their use has been limited because of the difficulty of forming
metal into
small diameter tubes. For a given sheet thickness, smaller diameter tubes
require
greater force to deform the sheet and form the pipe. Also, decreasing the
thickness of
the tube wall (the thickness of the tube-forming sheet or strip) increases the
tendency
to buckle. In addition, it is more difficult to control the diameter and to
maintain a
consistent lockseam as the tube is formed.
Commonly assigned US patent no. 5,074,138 in the name of Robert F. Miller
describes an improvement of the invention disclosed in US patent no.
3,247,692. The
improvement involves the design and manufacture of a lockseam pipe which has a
corrugated, sinusoidal profile comprising arcuate/semi-circular ridges and
grooves,
and which is adapted for improving the physical characteristics of the pipe
and the
strength of the lockseam. US patent no. 5,074,138.
SUMMARY OF THE INVENTION
The present invention is embodied in the structure and manufacture of a thin
wail
bellows tube or pipe which is formed from a metal strip having a rectangular
ribbed
profile. In one aspect the tube is used as a core onto which a sheet of
material can be
wound or coiled for shipment, handling and dispersal. In a particular aspect
this
invention relates to the structure and manufacture of such a core from strips
of metal
and, more particularly, from a thin strip of metal such as aluminum.
According to one aspect of the present invention, there is provided a method
for
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forming a metal strip into a cylindrical core, comprising: a corrugation
forming process
for forming a corrugated metal strip, the corrugation forming process
comprising
passing an elongated metal strip having width and length and opposite
longitudinal
edges through a multiplicity of forming stands which form rectangular
components
and generally straight segments thereof in said strip and change the size and
shape
of the segments and components previously formed at said forming stands,
wherein,
upon completion of the corrugation forming process, the strip comprises
longitudinally extending, alternating ridges and grooves having generally
vertical
spaced-apart sidewalls with the ridges further comprising longitudinally
extending,
flat, spaced-apart top surfaces extending between adjacent ridge sidewalls of
the
generally vertical spaced apart sidewalls and the grooves further comprising
longitudinally extending, flat, spaced-apart bottom surfaces extending between
adjacent groove sidewalls of the generally vertical spaced apart sidewalls,
the ridges
and grooves together forming a rectangular, flat ribbed cross sectional
profile
extending along the width of the strip transverse to the length thereof;
forming the
opposite longitudinal edges of the formed corrugated metal strip into flanges
adapted
for forming an interlocking seam; helically coiling the corrugated strip
formed with
said flanges into a cylinder having a longitudinal axis and an outer surface
defined by
flat, spaced-apart surfaces selected from the top surfaces and the bottom
surfaces;
and compressing the opposite edge flanges together thereby forming the
interlocking
seam extending in a spiral around the cylinder along the longitudinal axis
thereof.
According to another aspect of the present invention, there is provided a
cylindrical
core, comprising: an elongated metal strip having width and length and being
helically
coiled into a cylinder, the cross-sectional profile of the strip along the
width thereof
transverse to the length thereof comprising a rectangular ribbed configuration
formed
by longitudinally extending, alternating ridges and grooves, the ridges having
longitudinally extending, flat, spaced-apart top surfaces, the grooves having
longitudinally extending, flat, spaced-apart bottom surfaces, and the ridges
and the
grooves together forming a flat ribbed transverse cross section; said cylinder
having
an outer surface formed by flat spaced-apart surfaces selected from the top
surfaces
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of the ridges and the bottom surfaces of the grooves; and a lockseam of joined
opposite edges of the metal strip, the lockseam extending in a spiral around
the
cylinder along the longitudinal axis thereof.
BRIEF DESCRIPTION OF THE DRAWING
.. Fig. 1 is a transverse cross-section of a metal strip having a rectangular
corrugated
transverse profile formed therein in accordance with an embodiment of the
present
invention, and preparatory to the strip being helically wound into a tubular
core.
Fig. 2 depicts a strip such as that of Fig. 1 being wound into a helical
tubular core.
Fig. 3 is a transverse cross-section of two adjacent windings of a strip such
as that of
.. Fig. 1 where the strip is helically wound to form a core such as that of
Fig. 2, and the
leading edge of one winding of the strip is joined by a lockseam to the
trailing edge of
the adjacent winding.
Figs. 4-13 depict the changes in the profile of a strip or sheet at sequential
stages of
the profile-forming process.
DETAILED DESCRIPTION
The pipe forming in accordance with embodiments of the present invention can
be
achieved via fixed forming using a forming shoe with a predetermined inside
diameter
to provide the desired pipe diameter, or by free forming using several sets of
roller
dies of different sizes to achieve pipes of different diameters, by adjusting
the helix
.. angle or by a combination thereof.
The illustrative equipment and process described here use, and are
improvements of,
the multi-pass roll former, three roll, free forming system disclosed in
commonly
assigned and US patent nos. 3,940,962 and 3,247,692 as specifically adapted to
bellows pipe (relatively small diameter corrugated pipe) in commonly assigned
and
US patent
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.84111903
no. 5,074,138.
According to an embodiment of the present invention and referring to Figure 1,
initially
a flat metal strip or sheet is roll-formed to a desired profile.
Referring to Figures 4-13, according to an embodiment of the present
invention, a flat metal strip or
sheet is passed through multiple stands of forming rolls to initially form
rectangular features and/or
straight line segments of rectangular features and to progressively add to and
refine these
segments and features to form the desired rectangular ribbed profile. More
specifically, Figures
4-13 depict the sequence of changes in the strip profile starting with the
initial fiat strip profile
and progressing through the finished rectangular ribbed profile. The ten
Figures 4-13 depict
the associated profiles 40-49 after the strip is driven through each of the
ten stands of forming
rollers. Illustratively, ten passes through roll-forming stands are used to
form the profile.
The above profile-forming method results in the profile 10 shown in Figure 1
which comprises
alternating rectangular ribs in the form of rectangular ridges 11 and
rectangular grooves 12.
The ridges 11 have flat top or upper surfaces 13 and the grooves 12 have fiat
bottom or lower
surfaces 14. A downward (or upward) opening flange or tab 16 is formed
extending along one
longitudinal edge of the strip or sheet transverse to the width of the strip
and an opposite
opening upward (or downward) extending tab 17 is formed extending along the
opposite
longitudinal edge of the strip.
To form the profiled strip into a tube or core, and referring to Figure 2, the
rectangular-ribbed
profile strip or sheet 10 is wrapped using helical foorming apparatus into a
cylindrical pipe or
core 20 of the desired diameter arid, as shown in Figure 3, the mating tabs 16
and 17 are
compressed together to form a four-ply interlocked helical seam 21 which wraps
around the
pipe lengthwise along the pipe. The strip edges are held together via a
continuous mechanical
lockseam which is pushed together to lock the lockseam.
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In the formed pipe 20, the spaced-apart adjacent flat surfaces 14 of the
rectangular
grooves/ribs 12 form the outside surface 22 of the core 20 and the spaced-
apart flat surfaces
13 of the rectangular ridges/ribs 11 form the inside surface 23 of the core.
The strip 10 Illustrated in Figure 1 is symmetrical top-to-bottom and thus can
be reversed top-
to-bottom during the pipe wrapping process depicted in Figure 2. Then the
spaced-apart flat
ridge/rib surfaces 13 form the outer surface 22 of the core and the spaced-
apart flat groove/rib
surfaces 14 form the inside surface of the core.
Referring to the Figure 3 cross-section of the core 20 depicted in Figure 2,
in the pipes made in
accordance with embodiments of the present invention, the ridges and grooves
maintain their generally
rectangular, ribbed shape and form an open structure with spacing between the
adjacent
ridges 11 as well as spacing between the adjacent grooves 12. This is unlike
prior designs whkh
use non-rectangular shapes and/or an additional deformation step to form a
continuous outer
surface in order to provide the required strength and integrity and to provide
ample flat
surface area for sheet support. The outer surface is interrupted by the
spacing of the inside
rectangles. in a present embodiment, the width of the ridges and the grooves,
and the spacing
between adjacent ridges and between adjacent grooves, are all equal.
Embossments or reinforced embossments can be formed in the ribs, e.g., in the
vertical legs of
the ribs, to provide additional strength to the core.
Examples
The above design and method have been used to form cylindrical cores of
different sizes.
Specifically, in strips or sheets 10 of aluminum which were 0.010" to 0.023"
thick and 3 5/8"
wide, ridges 11 and grooves 12 were formed which were 0.27" in height from the
top of the a
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ridge to the bottom of the adjacent groove. Both the ridges and the grooves
were 0.27" wide
and were spaced apart 0.27" from adjacent ridges and grooves, respectively.
See Figure 1. The
rectangular corrugated strips or sheets 10 were fed to three-roll apparatus
using helix angles?
60 measured from the axis of the outgoing pipe to form continuous length
pipes of 16", 20"
and 24" inside diameters. The pipes 20 were then cut into various lengths for
use as recyclable
cores onto which sheets of metal such as aluminum were to be wound for
handling and
dispersal.
Other dimensions and materials will be readily adapted to embodiments of the
invention described
here by those of usual skill in the art. For example the invention can be used
to form pipes
approximately 6" in diameter and greater. For a given sheet width, increasing
the helix angle
increases the pipe diameter. For a given pipe diameter, increasing the sheet
width reduces the
required helix angle. Increasing the strip width tends to increase the pipe
wrapping/manufacturing speed and to decrease the number of seams in a given
length of pipe.
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