U.S. patent number 3,918,283 [Application Number 05/464,556] was granted by the patent office on 1975-11-11 for tubular articles and method of making same.
This patent grant is currently assigned to Interstate Products, Inc.. Invention is credited to Paul Kosch, Paul James Kosch.
United States Patent |
3,918,283 |
Kosch , et al. |
November 11, 1975 |
Tubular articles and method of making same
Abstract
A perforate, thin-walled, tube structure of surprisingly high
strength, having a tightly-clenched lock seam and generally helical
wall corrugations, manufactured by a generally continuous rolling
process in which the stock is first put through a piercing and
corrugating stage and is then fed through a number of
complementary-shaped pairs of rollers which progressively change
the shape of the stock from basically flat to generally circular in
cross-section and with a progressively-formed lock seam joining the
edges of the stock in a tightly clenched manner, by use of an arbor
extending inside the tubular stock and having a roller which bears
against the inside of the lock seam to provide for tight clenching
of the latter by an external roller and, at the same time, helping
pull the stock through the various roller stages, through all of
which the initially-formed wall corrugations are maintained intact
in an unflattened condition.
Inventors: |
Kosch; Paul (Grand Haven,
MI), Kosch; Paul James (Spring Lake, MI) |
Assignee: |
Interstate Products, Inc.
(Spring Lake, MI)
|
Family
ID: |
23844401 |
Appl.
No.: |
05/464,556 |
Filed: |
April 26, 1974 |
Current U.S.
Class: |
72/52; 72/177;
72/368 |
Current CPC
Class: |
B21C
37/101 (20130101); B21C 37/104 (20130101) |
Current International
Class: |
B21C
37/10 (20060101); B21C 37/06 (20060101); B21D
039/02 () |
Field of
Search: |
;72/52,177,368,370,51
;113/116UT ;29/477.7,2B |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; C. W.
Assistant Examiner: Rogers; Robert M.
Attorney, Agent or Firm: Price, Heneveld, Huizenga &
Cooper
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are described as follows:
1. A method of manufacturing thin-walled, lock-seam tubing,
comprising the steps: shaping a generally flat sheet of stock by
forming generally longitudinally-extending groove-like depressions
therein; then moving said stock as so formed lengthwise through
successive pairs of mating rollers, having cooperative shapes which
progressively change the cross-sectional shape of said stock from
generally flat to generally circular; forming oppositely-disposed
flange portions along the edges of said stock, and inter-engaging
the same to form a loose lock seam closing the circumference of
said generally circular cross section and forming a tube thereof;
clenching said loose lock seam tight by passing said tube through
at least one pair of rollers while extending an arbor means inside
the tube and between such pair of rollers, by using an arbor means
having an anvil element disposed in contact with the interior part
of said lock seam and using a clenching portion on at least one of
such rollers to tightly flatten the lock seam between itself and
said anvil element; rotatably driving at least certain of said
pairs of rollers to exert a pulling force on said stock; and
maintaining said groove-like depressions in generally unflattened
condition throughout said mating roller steps following formation
thereof, so that such depressions are still present in the
completed lock seam tube.
2. The method of claim 1, wherein said shaping step comprises
embossing said stock to form corrugation-like depressions and
ridges therein.
3. The method of claim 1, wherein said shaping step is carried out
to form said groove-like depressions at an acute angle with respect
to the longitudinal axis of said stock, such that when the stock is
rolled into a tube said depressions extend generally helically
thereof.
4. The method of claim 3, including the step of forming a plurality
of apertures in said stock prior to said clenching step.
5. The method of claim 4 wherein said apertures are formed to lie
in lines extending along said groove-like depressions.
6. The method of claim 5, wherein said shaping step comprises
embossing said stock to form corrugation-like depressions and
ridges therein, said apertures lying within said depressions.
7. The method of claim 1, wherein a plurality of said pairs of
mating rollers are driven and used to grip said formed stock
between such rollers and exert a pulling force on the stock, to
help move the latter through the said roll-forming operation, while
maintaining the nature and force of such grip such that the same
does not substantially flatten said depressions.
8. The method of claim 1, wherein said flange portions are formed
while said stock is still generally flat or semicircular in
cross-sectional shape and prior to the time the same closely
approaches circularity.
9. The method of claim 1, wherein said depressions are formed prior
to any of said roll-forming of said stock into tube form.
10. The method of claim 9, wherein said depressions are formed
prior to formation of said flange portions.
11. The method of claim 10, including the step of forming a
plurality of apertures in said stock at substantially the same time
as when said depressions are formed.
12. The method of claim 1, including the step of using a rollable
member as said anvil element of said arbor means.
13. The method of claim 1, including the step of using a sizing
member as a part of said arbor means, with the outside diameter of
such member being substantially the same as the desired inner
diameter of the completed lock seam tube.
14. The method of claim 1, including the steps of using a pair of
different arbor elements as said arbor means, by passing the tube
over a diameter-sizing element prior to clenching, and clenching by
using an inner arbor having a rollable member bearing against the
inside of said seam.
15. The method of claim 14, including the step of providing
tooth-like serration elements on said clenching roller, on the
opposite side of said lock seam from said rollable member of said
inner arbor.
16. The method of claim 15, including the step of providing
tooth-like serration elements on said rollable member of said inner
arbor.
17. The method of claim 1, including the step of using a pair of
lateral squeezing elements to interengage said flange portions
after said stock has been brought to a substantially full-circle,
tubular cross-sectional shape, by pressing the sides of the tubular
stock inwardly to in effect reduce the diameter thereof and bring
the flange portions over and beyond one another.
18. The method of claim 17, including the step of applying a
radially inwardly-directed diameter-maintaining force to said
substantially full-circle tubular stock at least slightly prior to
said interengaging step.
19. The method of claim 18, wherein said diameter-maintaining force
is applied by using undriven, "floating-axis" roller elements at
least one of which is resiliently biased toward the other and
movable toward and away from the latter.
20. The method of claim 19, including the step of using a
diameter-enlarging arbor element inside said tubular stock at a
point downstream from that where interengagement of said flange
portions takes place.
21. A method of manufacturing thin-walled, longitudinally fluted
tubing, comprising the steps: shaping a generally flat sheet of
stock by forming generally longitudinally-extending fluted
deformations therein; rolling said stock through a plurality of
successive pairs of mating rollers to thereby incrementally and
progressively change the overall cross-sectional shape of said
stock from generally flat to generaly circular; closing the
circumference of said generally circular cross section and securing
the longitudinal edges thereof together to form a tube; rotatably
driving selected ones of said rollers during said rolling process
including at least certain thereof located where said stock has
become generally circular to exert a pulling force on said stock,
while leaving other selected rollers undriven including certain
thereof located near the beginning of said rolling process where
said stock is still generally flat to act as a drag on said stock;
and maintaining said fluted deformations in generally unflattened
condition throughout the steps following formation thereof, such
that the same are still present in the completed tube.
22. The method of claim 21, wherein said undriven rollers comprise
a minor proportion of said plurality thereof in said rolling
process.
23. A method of manufacturing thin-walled, seamed tubing comprising
the steps: shaping a generally flat sheet of stock by forming
depression formations therein between the edges thereof, while
providing generally flat axially-extending portions along the edge
margins of said stock; then moving said stock as so formed
lengthwise through successive pairs of mating rollers having
cooperative shapes which progressively change the cross-sectional
shape of said stock from generally flat to generally circular;
using closely-spaced complementary mating side edge portions on at
least certain of said mating rollers to grip said generally flat
portions along the edge margins of said stock to help pull the
stock through said successive pairs of rollers while its
cross-sectional shape is so changed; forming oppositely-disposed
flange portions along the edges of said stock, and interengaging
the same to form a seam closing the circumference of said generally
circular cross section and forming a tube thereof; rotatably
driving at least certain of said pairs of rollers to exert a
pulling force on said stock; and maintaining said depression
formations generally unflattened and intact throughout said mating
roller steps following formation thereof, so that such depressions
are still present in the completed lock seam tube.
Description
BACKGROUND OF THE INVENTION
This invention relates to the roll-forming of sheet stock,
typically metal, into tubular form and, in particular, to the
formation in such manner of perforated thin-wall tubing having a
tightly clenched lock seam and wall corrugations for added
strength.
Perforated tubes, usable for example as filter cores, as well as in
many other ways, have been manufactured in the past and sold on a
commercial basis but the kinds of such tubing heretofore available
have been typically characterized by rather low wall strength (in
compression and bending), as well as by loose seams or joints. This
has particularly been true in the case of thin-walled tubing, which
has not even been manufactured on an extensive basis by many
manufacturers, and when manufactured has heretofore been done
primarily on special machines, in short lengths, where it was still
characterized by the aforementioned problems of wall strength and
loose seams. Primarily, this is because the thin-walled stock (for
example, stainless steel on the order of 0.010 inch - 0.015 inch
wall thickness) is clearly of a highly flexible nature, and this is
particularly true when, to be used as filter core, the stock must
be highly perforate in nature, having a great number of holes
punched or otherwise formed in it.
Consequently, it has sometimes heretofore been attempted to form
annular corrugations in the walls of the stock in an effort to
strengthen it; however, such corrugations are basically inimical to
roll-forming techniques and, therefore, tubing of this type is
generally limited to manufacture on special-purpose machines, on
which only short lengths can be made; furthermore, such
corrugations do not really provide as much strength as is desired,
particularly in thin-walled stock of the type mentioned above.
SUMMARY OF THE INVENTION
The present invention provides a new process for the manufacture of
lock-seam tubing, particularly advantageous for manufacturing such
tubing from extremely thin-walled stock, and for the manufacture of
such tubing in long lengths and, in fact, practically unlimited
lengths. Furthermore, the process of the invention is basically of
a continuous nature, and is extremely rapid when compared to other
specialized manufacturing processes for thin-walled tubing, which
are also limited in length, with manufacturing speeds as much as
ten to twenty times the speed of the special processes just
mentioned.
Additionally, the invention provides, as an article of manufacture,
new and superior thin-walled tubing products, in particular,
thin-walled tubing having highly perforate walls, and yet of
exceeding strength, particularly in lateral loading situations
(i.e., crushing). Still further, the tubing provided by the
invention has an extremely tightly-clenched lock seam which, with a
novel wall configuration also provided, contributes to the
structural strength of the tubing and, at the same time, adds great
reliability to the product.
The foregoing major objectives and advantages of the invention, as
well as numerous other objects and advantages thereof, will become
more apparent upon consideration of the attached drawings and the
following specification.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary, side elevational view showing the overall
apparatus used in the invention;
FIG. 2 is an enlarged, fragmentary, side perspective view showing
certain details of the apparatus of FIG. 1;
FIG. 3 is an enlarged, fragmentary, side perspective view showing
certain other details of the apparatus used;
FIG. 4 is an enlarged, fragmentary, side perspective view showing
further details of the apparatus used;
FIGS. 5-17 inclusive constitute a series of enlarged, fragmentary,
sectional end elevations, each taken through a succeeding one of
the roller stages illustrated generally in FIG. 1, showing the
progression in cross-sectional shape of the stock from
substantially flat to substantially circular;
FIG. 14a is a fragmentary side elevational view on a reduced scale,
showing details of the apparatus used between the roller stages of
FIGS. 14 and 15, respectively;
FIG. 18 is a fragmentary, sectional side elevational view showing
further details of the apparatus of FIGS. 16 and 17, shown on a
reduced scale;
FIG. 19 is an enlarged, fragmentary, top plan view showing the
nature of the stock after piercing and corrugating but prior to the
roll-forming operations;
FIG. 19a is an enlarged, fragmentary cross-sectional view of the
stock shown in FIG. 19; and
FIG. 20 is an enlarged, fragmentary, overhead plan view showing the
nature of the tubular product made by using the method and
apparatus of the invention.
DESCRIPTION OF A PREFERRED EMBODIDMENT
Although the concepts of the invention are undoubtedly susceptible
to implementation in at least several somewhat varying embodiments,
one preferred embodiment is illustrated in the drawings, from FIG.
1 of which it can be seen that apparatus for the practice of the
invention may include a first stage 10 which may be described as a
stock-conditioning stage, and a multi-part, composite second stage
20, constituting a progressive series of different shaping steps.
Basically, the first stage 10 illustrated in the drawings makes use
of a punch-press apparatus 12, which may be basically of a
conventional nature, to which flat stock 14 from an appropriate
supply, as for example a long length of sheet metal wound on a roll
and having the requisite width, is fed through a guiding pair of
rollers seen at 16, over a platen 17, which carries half of a
mating die set which is complementary to another half die 18
carried on the ram 19 of the punch press, such that the stock 14 is
advanced in step-by-step fashion, indexing beneath the ram 19 so as
to be struck between the die parts 17 and 18. As will be
understood, such step-by-step operation is generally of a type long
known in the art, in which controlled apparatus such as the roller
set 16 (which is typically duplicated at the outlet of the punch
press by another similar set of rollers located there) operates to
advance the stock in synchronism with the cycling operation of the
punch press ram.
The first stage 10 of the apparatus functions to condition, or
pre-form the stock 14, from a basically flat ribbon-like sheet in
which it is supplied from its roll or other such source to the form
illustrated in FIGS. 18 and 18a; that is, the stock is deformed
into an undulating or corrugated shaped 14a, in which the stock
remains basically flat at the edge extremities but has alternating
peaks and valleys 22, 24 disposed angularly across its width, and
with a great plurality of holes 26 extending through the stock. The
peaks and valleys 22, 24 actually comprise elongated
groove-deformations, the axes of which are oriented at an acute
angle with respect to the longitudinal axis of the stock 14, most
preferably, an angle of 45.degree.. In the context used in this
specification, the term "groove-like" is intended to mean a single
such deformation, for example an elongate peak 22, while
"corrugation-like" is intended to connote the undulating, reversely
complimentary nature of adjacent peaks and valleys. The term
"longitudinally-extending" used relative to the deformations just
mentioned is, in its broadest implications, intended to mean that
the undulations or corrugations are at least somewhat longitudinal
and not perpendicular to the longitudinal axis of the stock, i.e.,
that they are either angled acutely across the latter or, in an
extreme, parallel to such axis, but do not extend perpendicularly
across the same.
It may be noted that the holes 26 are all disposed within aligned
columns or ranks located in the valleys 22, and this is the
preferred form, although in certain instances the apertures can
also appear in the peaks. If, in the practice of the invention, a
first stage 10 is used such as the punch press herein illustrated
and described, the intermittent step-by-step operation thereof will
make advisable the presence of a loop or bight 28 of preformed
stock between the first and second stages, to ensure a continuous
supply of the preformed stock for the second stage, which is
basically of a continuous nature. In this regard, however, other
types of apparatus may readily be used as the first stage, e.g.,
complementary rollers or a mangle or the like incorporating the
required groove-forming configurations, with the piercing or other
such forming of the apertures 26 occurring either as a part of such
operation, or at some other time. In any event, the pre-forming of
the first stage may occur either as a generally continuous process,
or in the step-by-step manner illustrated in the preferred
embodiment.
As illustrated in FIG. 1, the preformed stock 14a moves as a
generally continuous ribbon from the loop 28 at the inlet of the
second stage to the opposite end of the latter, at which the stock
has been transformed into the tubular shape 30 indicated in FIG. 1.
In undergoing this change, the stock is first passed through a
first series of rollers which, in the preferred embodiment
illustrated, may include 10 different and distinct individual sets
of rollers 32-50, inclusive, which basically serve to bend the
stock into designated requisite circular cross-sectional shape. The
formed stock then passes through some intermediate roller stages 60
(illustrated in more detail in FIGS. 2-4) serving to interengage
the formed edges of the tube constituting the lock seam portions,
and then passes through forming and clenching rollers 70 and 80,
and finally, through straightening apparatus 90 illustrated in more
detail in FIG. 4. Each of the roller sets 32-50 and 80-90 may be
rotatably driven by a direct mechanical connection (for example, a
geared connection which is selectively engageable) to a drive train
99 (FIG. 1), typically embodying a long splined or other such drive
shaft, which is rotatably driven by a motor 100. As noted below,
however, not all of the roller sets are in fact so driven, in
particular modes of operation.
Although the basic nature of the roller mill machine constituting
the entire second forming stage 20 is of a known commercial nature,
the particular roller sets and other apparatus used, as well as the
manner in which the same are used, constitute a decided departure
which enables the manufacture of structurally superior thin-walled
perforated lock seam tubing and accomplishes the same at a great
increase in speed.
More particularly, as may be seen by reference to FIGS. 5-17, the
incoming stock 14a first passes between a pair of rollers 32a, 32b
(FIG. 5) which, while primarily contacting the stock along flat
opposite edges nonetheless have edge extremities which angularly
configure (i.e., bend) the uncorrugated edges of the stock in the
manner illustrated. This bending, or configuring, of the edge
extremities of the stock continues through mating rollers 34, 36,
38 and 40, (FIGS. 6-9) through all of which the stock remains in
basically flat condition although progressively becoming somewhat
broadly U-shaped, but with the edge extremities 114, 214 of the
stock progressively being shaped so that edge 114 is reversely bent
into a hooking flange oriented toward the interior of the troughed
stock and edge 214 being oppositely-configured into a hooking
flange oriented toward the exterior of the curved or troughed
stock. Throughout this entire time, the complementary rollers in
all or a selected lesser number of each set thereof can exert a
reasonable pulling force on the stock, since the latter stays
basically flat, although the clearance between the two rollers in
each set always carefully maintained such that the corrugations in
the stock are never flattened. As will be understood, the two
rollers in each set are both basically cylindrical elements with a
unfiorm cross section around their entire periphery, and with axial
pins or journals (note FIGS. 2, 3 and 4) extending laterally from
each opposite side on the axis of rotation thereof, the fragmentary
showing of FIGS. 5-17 being limited in most cases to the area of
complementary contact betwen rollers and stock for purposes of
simplicity, inasmuch as this area is the one of chief
importance.
Following formation of the hooking flanges 114 and 214 as mentioned
above, the succeeding roller sets 42, 44, 46, 48 and 50 (see FIGS.
10-14 inclusive) gradually bring the stock 14a from a primarily
flat (i.e., less than semi-circular) shape to essentially a fully
circular shape, although still slightly open at the top, as
illustrated in FIG. 14. The change in complementary shapes of the
rollers in each of these sets is fully illustrated in the figures,
from which the progression in shape may be readily seen. As will be
observed, a radially-extending central part of each roller (for
instance, part 48c of roller set 48 in FIG. 13) protrudes inside
the increasingly-circular trough shape of the stock, so as to keep
a diminishing-width part of the stock in lightly pinched contact
between parts of the upper and lower roller in each set, which are
disposed directly opposite one another with the stock between. This
pinched contact helps pull the stock through the roller mill, along
with other forces to be described subsequently. At the stage 50,
however, this aspect of the complementary rollers ceases, and the
stock is brought very nearly into circularly closed condition by
rollers 50a, 50b which each basically comprise a
semi-circularly-grooved pulley-like roller wheel (FIG. 14).
Although the progression and shape of the roller sets 32-50 just
noted is certainly important to the process of the invention, the
intermediate rollers 60 and the first and second forming and
clenching rollers 70 and 80 have considerable importance to the
successful practice of the invention. That is, these elements
together with other structure now to be described, act to form the
lock seam and give the completed tube its final circular shaping,
in order to successfully complete the formation of the tube.
The intermediate or interengaging rollers 60 (FIGS. 2, 3 and 15)
actually constitute two different roller sets or component groups.
A first set 62 constitutes a pair of rollers similar in general
nature to rollers 50 of FIG. 14, described above, but with their
rotational axis rotated 90.degree., so that the two rollers lie in
a horizontal plane as opposed to a vertical one. However, roller
62a has a somewhat smaller groove than roller 62b (FIG. 15) and is
somewhat asymmetrically disposed with respect thereto, so that this
roller causes the formed hooking flange 214 to be resiliently
flexed relative to hooking flange 114 (compare FIGS. 14 and 15) and
shifted laterally with respect thereto, so as to overshift the two
hooking flanges, by, in effect, squeezing one side of the tube.
As will be understood, upon leaving roller set 62, the resiliency
of the tube stock would by itself tend to cause the tube to expand
diametrically so that hooking flange portions 114 and 214 move back
toward one another, and become hooked. This step of the process is
facilitated and insured, however, by the use of an elongated,
cantilevered mandrel 55 (FIGS. 14, 15 and 18) fixedly mounted on
the bed of the roller mill upstream of roller set 50 relative to
the direction of motion of the tube stock, and projecting
downstream, inside the tube being formed, through the long, narrow,
V-shaped opening formed by the hooking flanges 114 and 214 which,
at a point upstream from roller set 50, are still moderately spaced
apart. While the use of such a mandrel, in its broadest sense, it
known heretofore in rolling mill technology, this is not true of
the application of this concept to the present process, and such
use is an important part of the process.
That is, the aforementioned mandrel 55 projects downstream through
the tube being formed at stations 50, 60, 70 and 80 (see FIGS. 14,
15, 16, 17 and 18). At the first two such stages, the mandrel 55 is
considerably smaller in diameter than the encircling tubular stock
14a, and merely projects centrally thereof and out of contact
therewith. At stage 70, however, (FIG. 16) the mandrel 55 has a
first enlargement 75, which may be a concentrically mounted
sleeve-like arbor which is fixedly secured on the mandrel as by set
screws or the like. Arbor 75 closely approaches in size, but is
preferably somewhat smaller in diameter than, the desired inside
diameter of the finished tubing; thus, arbor 75 is larger in
diameter than the constricted size of the tubular stock at station
60, (shown in FIG. 15). Accordingly, the hooking flanges 114 and
214 are forced together into interengagement downstream of stage 60
not only by the resiliency of the tube stock, but also by being
passed over the larger-diameter arbor 75. At the same time, mating
rollers 70a and 70b of stage 70 (FIG. 16) are embracing the tubular
stock from both opposite sides and, furthermore, a rotatable
clenching wheel 77 disposed within a slot in arbor 75 and mounted
on an axle 79 fitted into a transverse bore 78 bears against the
underside of the hooking flanges as they are brought together. This
cooperative action first brings the hooking flanges into tightly
hooking engagement with one another, and then substantially closes
them upon one another so that they form a somewhat loose lock seam
as the stock is brought into closed tubular form.
Immediately downstream from stage 70, at stage 80, a second arbor
or other such enlargement 85 is mounted near the end extremity of
mandrel 55 (FIGS. 17 and 18). Arbor 85 is preferably slightly
larger in diameter than arbor 75, having exactly (or substantially
so) the required inside diameter for the finished tubing.
Furthermore, arbor 85 is centrally bifurcated or slotted to form a
slot 86 in which a second clenching wheel 87 is disposed, sometimes
referred to herein as an anvil, or clenching anvil. That is, arbor
85 has a transverse hole 88 bored therein, in which a pin 89 is
press-fitted, such pin constituting the axle for wheel 87 and
mounting the same in freely rotatable manner within the slot. As
illustrated, the clenching wheel 87 has a series of transverse
serrations or tooth-like formations 87a formed thereon for positive
engagement with the underside of lock seam 314. Directly above and
in the same vertical plane with clenching wheel 87 is a central
clenching band 82 which is preferably formed as one piece with
roller 80b, extending circumferentially around the latter at the
center of its grooved periphery, and constituting a slightly raised
annular formation having tooth-like projections 84 thereon like the
projections 87a on clenching wheel 87.
The spacing between clenching wheel 87 and clenching band 82 is
such that these two components tightly grip the lock seam 314
therebetween, to thereby tightly clench the lock seam together in
an extremely secure manner and, at the same time, to exert a
positive pulling force on the tubular stock and thereby greatly
facilitate the passage thereof through the rolling mill. That is,
roller 80a in effect supports the tubular stock from beneath while
wrapping it around the underside of arbor 87 and, in effect,
supporting the arbor through the interposed tubular stock. At the
same time, the tubular stock is forced downwardly and around the
top part of the arbor by roller 80b, with the lock seam being
tightly clenched. Rollers 80a and 80b are driven rollers, as are
other rollers in the preceding stages, except those at the
intermediate stage 60 and as noted subsequently. Consequently, each
of the driven roller pairs will contribute somewhat to the pulling
force required to properly carry out the process and cause the
stock to pass through the entire rolling mill; however, the final
clenching stage 80 is extremely important in this process,
contributing greatly to the pulling force required.
It should be noted that the pulling force just mentioned must be
accomplished without flattening the corrugations placed in the
stock initially; that is, without substantial or major flattening,
since some slight degree (on the order of, for example, 10 or 15
percent or thereabouts) may be unavoidable under some very
stringent conditions. Consequently, it is not simply a matter of
squeezing the stock tightly between opposing rollers, as would be
true if the stock were merely uncorrugated, plain sheet. Indeed, it
is this aspect of the process which may in some ways serve to best
characterize it and distinguish it from others, i.e., particularly
when the process is used with very thin-wall stock, it will be
appreciated that the corrugations or other upset formations in the
wall section would very easily be deformed and even flattened back
out of the stock with any great amount of force applied to the
stock by the different rollers in the roller mill. At the same
time, however, the rollers must grip the stock with sufficient
force to pull it through the roller mill, otherwise a rolling
process is clearly impossible. The requisite balance of forces is
accomplished by the gradual roll-forming process, in the
progression described above, and using the driven clenching roller
arrangement just described. This allows for the use of rigid,
accurately-sized steel rollers which will produce the desired
accuracy in size and will have the desired durability in use, even
though having a relatively low coefficient of friction with the
stock, as compared for example to hard foam or other types of
rollers which might be used and which would have a higher
coefficient of friction against the stock to better pull it through
the roller mill, but which would not have the desired accuracy or
durability.
The requisite balance, or relative contribution, of pulling forces
exerted on the stock by the different roller sets, mentioned above
as necessary to move the stock continuously through the rolling
mill and accomplish each of the different formative steps, is a
very important aspect. It should be noted in this regard that, at
least with very thin stock, it is not desirable to have the first
few stages or roller sets (e.g., 32 and 34) exert large pulling
forces on the stock even though this might otherwise be thought to
be advantageous or even essential since the stock is still
basically flat at this juncture and thus affords the best
opportunity for maximum gripping or pressure by the rollers,
especially along the edges, which are as yet still basically flat.
However, for this very reason the roller sets downstream from this
point exert lesser degrees of pulling force, and if the first few
sets of rollers are used to produce large pulling forces they will
also exert large pushing forces and may well cause the stock to
buckle between them and succeeding downstream rollers. For this
reason it is often advantageous, and at times may be essential
(especially with very thin stock) to leave the first few roller
sets (for example sets 32 and 34) undriven, i.e., not connected to
the drive train 99. When this is done, such undriven rollers will
exert a drag on the stock at their position, and this may somewhat
surprisingly, help to attain the desired distribution or "balance"
of pulling and pushing forces on the stock along the progression of
rollers.
In bringing the stock to its final circular cross section, and in
interengaging the hooking flanges, it may be noted (FIGS. 2 and
14a) that the intermediate interengaging stage 60 includes, in
addition to rollers 62a and 62b already discussed, a floating
roller set which comprises a pair of spool-like roller elements 66
and 67 (FIG. 14a) having a generally V-shaped annular groove
centrally of each which rides upon and guides the stock 14a as it
reaches circular engagement. As illustrated, the lower roller spool
67 is journaled in appropriate fixed bearing blocks 68, while upper
roller spool 66 is mounted in a pivotal arm 65 having a spring 64
which urges the arm and spool downwardly in a yielding manner while
controlling the force with which roller 66 engages the stock.
Adjustment nuts 63, in turn, enable adjustment of the force setting
of spring 64. As stated earlier, the hooking flanges of the stock
are narrowly spaced apart at roller set 50, and are overshifted at
roller set 62, with a long, narrow V-shaped space between such
roller stages. The roller spools 66, 67 thus support and guide the
work stock between these points and have been found to facilitate
and help insure the successful joining of the hooking flanges,
particularly as a result of the floating, spring-biased engagement
of these rollers with the work stock.
Immediately downstream from the final roller stage 80 is the
straightening apparatus 90 mentioned previously (FIGS. 1 and 4).
Basically, this apparatus comprises two sets 92 and 94 of
spool-like rollers similar to rollers 65 and 66 of the intermediate
stage 60. Each of these four rollers is permanently journaled
between a pair of end plates 95 which are adjustably mounted on the
bed of the roller mill, such that by rotating pairs of adjustment
handles 96, 97 and 98, the entire apparatus, including the end
plates and the two sets of rollers, may be shifted as a unit in
these axes relative to the longitudinal axis of the formed tubing,
which issues endwise from a bronze bushing 100 or the like held in
an appropriate bearing block; that is, by adjustment of one or
another of the adjustment handles, the apparatus may be shifted
laterally, vertically, or angularly relative to the axis of the
emerging tubing. In this manner, the tubing may be slightly
cold-worked or stressed so as to straighten it longitudinally and
insure that regardless of the length of tubing issuing during any
given interval, such tubing will remain axially straight. With
respect to tubing length, the apparatus and manufacturing process
just described is basically of a continuous nature and can produce
straight, long sections of tubing whose length is determined
ultimately only by the length of the stock supplied to the
apparatus. Of course, finished lengths of tubing of particular
dimension, however long, will typically be desired and in order to
accomplish this the apparatus may be stopped periodically to cut
the emerging tubing at any desired length or, alternatively, any
other variety of traveling cutting devices may be used if it is
desired to run the apparatus continually.
The finished tubing made in accordance with the invention is
illustrated in FIG. 20, after completion of the lock seam 314. As
illustrated, in its final circularly rolled form, the angular
corrugations or groove-like deformations 22 or 24 can be made to
align with one another, so as to be generally continuous in nature
and thus define generally helical formations, although such term is
not intended to mean that such formations are truly helical in a
strict sense. In the finished form of the tube the undulating or
corrugated wall section adds very high strength to the tubing,
especially in the critical area of lateral or crush strength, which
is a demanding requirement when the tubing is used for filter
cores. As illustrated in FIG. 20, the tightly-crimped lock seam 314
actually becomes marked with a series of transverse impressions
formed by the operation of the tooth-like formations 84 and 87a of
the clenching band and roller, respectively, and thus serve to
demonstrate the high degree of clenching compression imparted to
the lock seam. The very tight lock seam construction adds to the
strength of the tubing and it helps to ensure the continuing high
degree of circularity of the latter, even after extended use,
despite the many wall perforations 26 which will permit a high rate
of fluid flow through the wall.
It is entirely conceivable that upon examining the foregoing
disclosure, those skilled in the art may devise embodiments of the
concept involved which differ somewhat from the embodiment shown
and described herein, or may make various changes in structural
details to the present embodiment. Consequently, all such changed
embodiments or variations in structure which utilize the concepts
of the invention and clearly incorporate the spirit thereof are to
be considered as within the scope of the claims appended herebelow,
unless these claims by their language specifically state
otherwise.
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