Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to expander rollers ~also
called rotary stretcher~) for webs of paper, textile
material, foil or the like.
- Expander rollers are used to treat webs of
flexible material which are being paid out by supply
rolls and/or during winding of webs onto takeup rolls.
v As a rule, an expander rolle:r has a core of metallic or
other suitable material and an outer layer which has an
external web~engaging surface designed to stretch the
10 adjacent portion of the running web in response to
rotation of the core. The purpose of the expander roller
is to preferably stretch the running web in a
direction from the center toward both marginal portions
in order to eliminate folds, creases and/or other
irregularities or to prevent the development of such
irregularities. Many types of webs, such as paper webs,
webs of textile material, webs of metallic or plastic
foil, webs of interlaced ~ibers (e.g., fleece) and the
like cannot be processed at all if they develop
20 longitudinally extending and/or otherwise oriented fold
lines, creases and/or other unevennesses. An expander
roller applies to the adjacent portion of the running web
forces acting in the axial direction of the core, or
having components extending in such direction, to ensure
that the width of the running web increases or tends to
increase in order to eliminate creases, fold lines or
similar irregularities (hereinafter called creases for
short) or to prevent the development of creases while the
web is being advanced from a preceding station to the
- 30 next-following station.
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As a rule, the external sL~rface of the ou-ter
layer of a conventional expander roller has one or more
helical profiles, preferably two profiles which are
mirror images of each other with reference to a plane
extending between the two pro-files at right angles to the
axis of the core. Thus, the lead or pitch of one of the
profiles is that of a right-hand thread and the lead oE
the other profile is that oE a leEt-hand t.hread. Each
profile tends to expand the ma-terial of a running web
from the center toward the respective marginal portion.
It is also known to provide the outer layer of a standard
expander roller with a single helical profile, such
configuration of the external surface oE the outer layer
also furnishes a desirable stretching or expanding action
at right angles to the direction of advancement of the
web.
In accordance with a heretofore known proposal,
the helical profile or profiles are obtained by grinding
or otherwise machining one or more helical grooves into
the external surface of a one-piece outer layer which
surrounds the core of the expander roller. The outer
layer of-ten consists of rubber. Such expander rollers
exhibit -the advantage that the outer layer produces a
highly satisfactory expandinc3 or stretching action and
that the core can be driven in a rather simple and
inexpensive way in contrast to the cores of certain other
; conventional expander rollers which employ arcuate cores
; and arcuate outer layers, i.e., wherein transverse
stretching of the running web is achieved as a result of
training the web over a roller having a curved axis.
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A drawback o conventional straight expander
rollers with outer layers of rubber or the likc is that
the machining of proEiles into the external surfaces of
the outer layers is a time-consuming and costly
procedure. Moreover, the ~ersatility of such rollers is
not entirely satisEactory, i.e., a particu:Lar roller is
capable of stretching only a single web or a series of
webs having a certain width, a certain thickness, a
certain flexibility or being in contact with a
predetermined percentage of the external surface of the
outer layer. Therefore, it is necessary to store a
substantial supply of discrete expander rollers in order
to ensure that a proper roller will be availa~le when the
treatment of webs of one type is completed and the
machine or apparatus employing one or more expander
rollers is to be set up for the processing of different
types of webs.
It was further proposed to replace the
one-piece outer layer of rubber or the like with an outer
layer which consists of or contains a helically
~ convoluted strip or band. The exposed side of the
convoluted band has a longitudinally extending
protuberance which constitutes a helix and engages the
running web of textile or other material in the course of
a stretching operation. I'he protuberance further serves
a~ a reinEorcing rib for the major portion of the strip
or band which is convolutad onto the core of such
expander roller. A drawback oE this proposal is that the
making of a band or strip with a protuberance involves
considerable expenses. Furthermore, the outwardly
-- 4 ~
Z~J~3~ 0
projecting helical protuberance of -the convoluted strip
or band is likely to damage or cleface a relatively thin
and sensitive running web of paper, foil or the like.
Therefore, such expander ro:LIers failed to gain
widespread acceptance in textile, paper making, paper
processing and other industries where webs o~ paper or
other flexible material must be convoluted onto or
unwound from rolls or reels without the development of
creases or for the express purpose of eliminating
existing creases.
The invention is embodied in an expander roller
which comprises a substantially cylindrical and
preferably straight core having a peripheral surface, and
an outer layer which surrounds the peripheral surface of
the core and includes at least one helically convoluted
strip (e.g., a strip of rubber or elastic plastic
material). The outer layer has a substantially
cylindrical external surface, and the external surface
has a profile which is composed of at least one groove,
particularly a helical groove. The outer layer can
comprise two helically convoluted strips which are
substantial mirror images of each other with reference to
a plane extending between the two strips and is normal to
the axis of the core.
Each strip has two lateral surfaces which
extend from the external surface of the outer layer to
the peripheral surface o~ the core and which preEerably
converge toward each other in a direction toward the
peripheral surface so that each strip has a substantially
trapezoidal cross-sectional outline. Each groove
-- 5 --
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preferably extends Erom the external surface of the outer
layer toward but short o-E the peripheral surface oE the
core, and each strip preferably comprises at least one
lip which is adjacent the respective groove and
constitutes that portion of t:he respective strip which is
disposed between the groove and the external surf'ace of
the outer layer. Eacil strip has two internal surfaces
which flank the respective groove. One in-ternal surface
is adjacent the respective lip and makes an acute anyle
with the external surface of the outer layer. Suc'h angle
is preferably between 30 and 50 degrees. ~ach lip is
deformable in response to enCJagement with a running web
of paper, textile or other material which is to be
expandecl or stretched as a re.sult of engagement with the
external surface of the outer layer w'hile the core is
being driven to rotate about its axis. Each lip is
preferably spaced apart from the coxe, and each lip can
include a rather pronounced edge adjacent the external
surface of the outer layer.
Each groove can have a substantially triangular
cross-sectional outline, and its width preferably
decreases in a direction from t'he external surface of the
outer layer toward the peripheral surface of the core.
The width of each groove at the external surface (as
measured in the axial direction of the core) is or can be
between 0.8 and 1.5 mm. The other internal surEace of
each strip in the respective groove is preferably
straight (as seen in a direction from the ex-ternal
surface of the outer layer toward the peripheral surface
of the core~. That portion of each lip which is adjacent
317(~
the external surface of t'he outer layer and includes the
aEorementioned edge is or can be readil~ deformable, and
t'he external surface can have a concave portion adjacent
; each lip. The concave portion oE the external surface
extends radially outwardly beyond the main portion of
such external surface (i.e., away from the axis of the
core) through a distance of approximately 0.2 to 0.7 mm.
Such concave portion preferably slopes gradua]ly from the
main portion of the external surface toward the edge of
the respective lip.
I'he readily deformable portion of each lip is
preferably movable toward and away from t'he ot'her
internal surface of the respective strip when the lip
oscillates while the expander roller is in actual use.
The two internal surfaces in each groove preferably make
a small acute angle. The width or thickness of the outer
layer in the radial direction of the core can be less,
for example, much less, than -the diameter of the core.
For example, such width or thickness can be in the range
of approximately 6 and 12 mm. Each groove can be
machined into the respective strip, e.g., by partially
slitting the strip with a knife or the like.
The profile of the external surface of the
outer layer can be composed of a plurality oE parallel
; grooves. For example, each strip can be formed with two
parallel helical grooves. The grooves of each strip are
or can be at least substantially identical. If each
; strip has two grooves, the open side of one groove can be
provided in one lateral surface of the respective strip
~' 30 adjacent the external surface of the outer layer, and the
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ot'her groove extends from the extcrna:L surEace toward but
short of the other lateral surface of the respective
strip. The minimum distance between neighboring grooves
of a strip can equal or appro~imate the distance of the
second groove from the other lateral sur-face of the
respective strip. The spacing between the open sides of
the grooves of a strip at the external surface of the
outer layer is preferably selected in dependency upon t'hc
characteristlcs o-f t'he web or she~t whic'h is to be
expandad by the improved roller. E'or example, the
spacing between the open sides of the grooves in a .strip
can be selected as a function of the thickness and/or
flexibility of the web. Furthermore, the lead of each
helically convoluted strip and of its groove or grooves
as well as of its lip or lips can be selected as a
function of characteristics of the material of the web
which is to be stretched or expanded by the roller.
Furthermore, the lead of each helically convoluted strip
can be selectec~ as a function of the diameter of the
core.
The distance between the innermost portion of
each groove and the peripheral surface of the core is or
can be in the range of 2 to 6 mm. The distance between
the lateral surfaces of each strip can be selected in
dependency upon the number of grooves in the strip. For
example, the distance will be 5 to 30 mm (preferably 5 to
10 mm) if the strip has a single groove and is preferably
between 12 and 30 mm if the strip has several (for
example, two) grooves.
As mentioned above, if the outer layer i5
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2~ J~7~)
composed of two strips, such strips can be mirror images
of each other. ~owever, it is equally possible to
convolute two or more strips in the same direction and
with the same lead 50 that t:he stri~s are disposed end to
end. It is normall~ preferred to convolute the strips in
such a way that the lead of one of the strips deviates
from the lead of the other strip; for example, one of the
leads is a right-hand lead and -the other lead is a left-
hand lead.
- 10 ~ach strip can contain or can consist of rubber
or other (e.g., plastic) elastomeric material. Means can
be provided for bonding the strip or strips to the
peripheral surface of the core.
The novel features which are considered as
characteristic of the invention are set forth in
particular in the appended claims. The improved expander
roller itself, however, both as to its construction and
-the mode of making and using the same, together with
additional features and advantages thereof, will be best
understood upon perusal of the ~ollowing detailed
description of certain presently preferred specific
embodiments with reference to the accompanying drawing.
FIG. 1 is an elevational view of a core and of
two discrete strips which are partially convolu-ted onto
the core;
E'IG. 2 is a transverse sectional view of the
assembled expander roller and a fragmentary longitudinal
sectional view of a running web, substantially as seen in
the direction of arrows from the line II-II in FIG. 4;
FIG. 3 is an elevational view of the assembled
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expander roller and a transverse sectional view of a web;
~ 'IG. ~ is an enlarged fragmentary axial
sectional view of the expancler roller and of a web which
is in contact with the external surface o~ the outer
layer of the roller;
- FIG. 5 is an enlarged fraymentary axial
sectional view of the core and of one of a strip which is
convoluted onto the peripheral surface of thc? core and
- has a single groove; and
E'IG. 6 is an elevational view of an expander
roller in front of a web which 3.S being stretched by the
profiled outer layer of the roller.
The improved expander roller comprises an
. elongated rotary core 1 having a cylindrical peripheral
.- surface 9, and an outer layer 2 composed of two helica:Lly
convoluted strips 3. The lateral surfaces 10, 11 of each
strip 3 are immediately adjacent each other or abut at 4
to form two helices which are mirror symmetrical to each
other with reference to a plane extending at right angles
to the axis of the core 1 and being disposed between the
two strips. The ends 5, 6 of the core 1 are provided
with smaller~diameter stubs 7, 8 which can be installed
in bearings (not shown) forming part of the frame of a
machine in which the improved expander roller is put to
i~ use.
As can be seen in E'IG. 5, the lateral surfaces
10, 11 of each of the illustrated strip 3 converge
slightly toward each other in a direction from the at
least substantially cylindrical external surface 16 of
the outer layer 2 toward the peripheral surface g oE the
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core 1, and the inner side 12 of each strip 3 is honded
to the adjacent portion of the externa] surface 9 by a
suitable adhesive indicated by a legend. ~:ach of the
strips 3 has a substan-tially trapezoidal outline ~6.
In accordance with a feature of the invention,
each strip 3 is provided with at least one groove 15
which has a triangular cross-sectional outline (in
undeEormed condition of the outer layer 2~ and extends
from t'he external surface 16 toward but short of the
peripheral surface 9, i.e., toward but short of the inner
side 12 oE the respective strip. The c~rooves 15 impart
to the external surface 16 oE the outer layer 3 a profile
14 whic'h induces a web 17 of textile, paper, foil or
other material to expand, i.e., -to increase (or to tend
to increase) its width and to thereby eliminate or at
least render less pronounced any fold lines, creases
and/or other irregularities which could affect the
appearance and/or fuxt'her treatment of the web. ~ach
groove 15 is adjacent a lip 45 which extends between an
inner surface 57 of the respective strip 3 and the
external surface 16 and has a rather pronounced helical
edge 53 at the external surface 1~. Those portions of
each lip 45 which are immediately adjacent the respective
edge 53 are readily deformable and can be flexed toward
and away from the second internal surface 55 in the
respective groove 15. The angle 52 (FIG. 4) between the
external surface 16 and the adjacent internal surface 57
(in undefor~ed condition of the outer layer 2) is a
relatively small acute angle, e.g., an angle between 30
and 50 degrees. The magnitude of the angle 52 depends
.~ i . . . .. . . ... .
Z~ 70
upon the extent of stretc'hiny oE the respective strip 3
durin~ winding onto the peripheral surface ~ of the
core 1.
The reference character 54 denotes the length
of the internal surface 57 in a direction ~rom the
external surface 16 toward -the peripheral surface 9. 'I'he
distance 30 between the deepmost point 63 of a groove 15
and t`he peripheral surface 12 depends on a number of
factors but is yenerally between 2 and 6 mm. 'rhose
portions (one shown at 59 in FIG. 5) of the external
surface 16 of the outer layer 2 which are immediately
adjacent the edges 53 oE the deformable lip5 45'have a
concave outline and slope gently in a direction outwardly
and away Erom the main or major portion of the externa]
surface 16 through a distance of preferably 0.2 to
;'' 0.7 mm. The portions 59 of t'he external surface 16 are
moved toward the axis of the core 1 when the improved
roller is in actual use, i.e., when the external surface
16 i5 en~aged by a running web 17. This can be seen in
FIG. 4, as at 58, i~e., the concave portions 5~ of the
external surface 16 become cylindrical and are coplanar
with the adjacent portions of the major part of the
surface 16.
The width of the open end of each groove 15 at
the external sur-face 16 of the outer layer 2 in
undeformed condition of this outer layer is preferably
between 0.8 and 1.5 mm. The angle 62 (FIG. 4) between
the internal surfaces 55 and 57 in each groove 15 is
preferably a small or very small acute angle, e.g., an
angle of less than 15 degrees. The internal surface 57
.:
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, and/or 55 are or can be straight (as seen in the
direction from the external surface 16 toward the
peripheral surface 9) in undeformed condition o~ the
outer layer 2.
The e]asticity of the readily ~e~ormable
portion of each lip ~5 in the region of the respective
edge 53 is preferably suf~iciently pronounced to enable
such readily deforlTIable portion to move back and ~orth
toward and away from the respective internal surface 55
in actual use of the expander roller, i.e., when the
external surface 16 is engaged by a running w~b 17 and
the latter alternately deforms and releases successive
increments of each lip ~5.
The aforediscussed distance 30 between the
deepmost portion 63 of a groove 15 and the peripheral
surface 9 of the core 1 is selected with a view to ensure
that the respective strip 3 is not likely to break or
crack between the deepmost portion 63 and its inner side
12 as a result of repeated flexing of the adjacent lip ~5
by the running web 17 in actual use oE the improved
~- expander roller.
The thickness 60 of the outer layer 2 (i.e.,
the distance between the peripheral surface 9 and the
external surface 16) depends upon the elasticity of the
material of the outer layer 2 and is preferably between
approximately 6 and 12 mm.
The lead of convolutions 18 and 19 (FIG. 3) of
the strips 3 depends upon the width oE such strips (i.e.,
on the distance 31 between the respective lateral
surfaces 10 and 11). The lead of the convolutions 18 and
- 13 -
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.
170
]9 is less pronounced if each of the strips 3 is provided
with a single groove 15. ~i'IG. 4 shows that each of the
strips 3 can be provided with a plurality of grooves
including the aforediscussed groove 15, a second groove
64 adjacent a lip 4~, and a third or median groove 115
adjacent a lip 145. The lead of a convoluted strip 3
which has several grooves is or can be more pronounced
than that of a strip having a lesser number of grooves.
Each groove has an open side at the external surface 16,
and the shortest distance between two neighboring grooves
(15, 115 or 115, 64) in a strip 3 preferably equals or
approximates the distance of the deepmost portion of the
groove 64 from the adjacent lateral surface 10. Each
groove lS of FIG. 4 is provided in the lateral surface 11
of the respective strip 3 adjacent the external surface
16 of the outer layer. The grooves of each strip 3 are
parallel to each other and can have identical cross-
sectional outlines in undeformed condition of the
respective strip. The provision of two or more grooves
enhances the elasticity of tha respective strip 3 in the
region of the external surface 16 of the outer layer 2
which is composed of one, two or more helically
convoluted strips. The mutual spacing 65 (E`IG. 4) of
open sides of neighboring grooves in a strip 3 (and hence
the distance of each groove 64 from the lateral surface
10 of the respective strip) depends upon certain
parameters of the web 17, particularly on the flexibility
and thickness of the web. The spacing 65 is less if the
web 17 to be treated is thin and/or readily flexible.
The thickness and/or flexibility of the web 17 further
- 14 -
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cletermines the lead of the convolutions 18, 19 which form
the ou-ter layer 2.
The distance 31 between t`he lateral surfaces 10
and 11 of a strip 3 can be between 5 and 30 mm. If a
strip 3 has two grooves, the distance 31 between its
lateral surfaces 10 and 11 can be between 12 and 30 mm;
on the other hand, the width of a strip havin~ a sincJle
groove (see E'IG. 5) need not exceed :L0 mm and preferably
should not be less than 5 mm.
FIG. 3 shows that the convolutions 18 and 19 of
one of the two strips 3 Eorm one half 35 and the
convolutions of the other strip 3 together form the other
half 36 o-f the outer layer 2. The symmetry plane between
the two hales 35, 36 is normal to the axis of the core 1
and is or can be located midway between the two ends 5, 6
of the core. The lead of convolutions 18/ 19 in one of
the halves 35, 36 is a left-hand lead and the other lead
is a right-hand lead. This enhances the ability of the
external surface 16 of the outer layer 2 to spread the
- 20 runnin~ web 17 in the axial direction of the roller,
namely from the center (where the two halves 35~ 36 abut)
toward the respective ends 5, 6 of the core 1. The
abutting ends of the two halves 35, 36 of the outer layer
2 are shown in FIG. 3, as at 37 and 38.
It is equally within the purview of the
invention to employ an outer layer which consists of a
single strip or of three or more strips. The lead of
convolutions of two or more strips can be identical or
different.
The material of each strip 3 i5 preferably
- 15 -
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elastic. Such strips can be made of rubber or an
elastomeric plastic material. As mentioned above, the
inner sides 12 of the strips 3 are or can be bonded to
the peripheral surface 9 of the core by resorting to a
suitable adhesive. It is preferred to subject the
peripheral surfaces 9 to a sllitable treatment which
ensures reliable re-tention of one or more convoluted
strips 3 on the core 1. For example, the peripheral
surface 9 can be roughened by sand blasting or in any
other suitable way preparatory to the application of one
or more films of adhesive which i9 to bond the strip or
strips 3 to the core 1. E~lowever, it is also possible to
provide the core 1 with a very smooth (e.g., highly
polished) peripheral surface 9 if the nature of the bond
between the core and the outer layer 2 is such that the
convolutions of the strip or strips 3 will properly
adhere to a smooth surface.
The stretching or expanding action of the outer
layer 2 depends on the hardness of its material. As a
rule, the hardness of the material of the outer layer 2
is between 35 and 45 Shore.
The core 1 can be made of steel or another
metallic material (e.g., aluminum or an aluminum alloy).
It is also possible to make the core 1 of a non-metallic
material, e.g., hard rubber.
The method of making the improved roller is as
follows: The number of grooves in each strip 3 is
selected in dependency on the desired lead of the
pro~iles 14 in the respective half of the external
surface 16. The stubs 7, 8 of the core 1 are then
- 16 -
2~ 70
mounted in a machine (e.g., a lathe) which can rotate the
core about its axis. The peripheral surface 9 is treated
in the aforedescribed manner to ensure the establishment
of a reliable bond between t'he core 1 and the inner side
12 of each s-trip 3. E'or example, the surface 9 can be
sand blacted prior to the application oE one or more
films of adhesive (e.g., by sprayiny or by means of one
or more brushes). The exact composition of the adhesive
will depend upon the finish of the surface 9 and on the
nature of the material of the strip or strips 3 as well
as on the desired quality of the 'bond between the core
and the outer layer.
If the outer layer 2 is to be composed of a
single strip 3, such strip i5 convoluted onto -the
rotating core 1 starting at one of the ends 5, 6 and
proceeding toward the other end. If the outer layer 2 is
to be assembled of two convoluted strips 3, the ends 37,
38 of the respective strips are affixed to the median
portion of the peripheral surface 9 (FIG. 3) and the two
strips are then convoluted in a manner as shown in FIG.
1, i.e., in directions toward the respective ends oE the
core. The two strips 3 can be convoluted onto the core 9
simultaneously or one after t'he other. The tensioning of
strips 3 during winding onto the core 1 will determine
the extent to which the edges 53 of the lips 45, 48, 145
project beyond the major por-tion of the external surface
16 when the making of the outer layer 2 is completed and
prior to deformation of such lips by a running web 17.
The exact configuration of the external surface 16 in
undeformed condition of the outer layer 2 will depend
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3~70
upon the characteristics of the web 17 which is to be
treated by the respective expander roller. The selected
tensioning of a strip 3 during winding onto the core 1
determines the elasticity of its lip or lips, i.e., the
elasticity of the lip or lips is less pronounced lf -the
strip which is being convoluted onto the core 1 is
subjected to a pronounced tensional stress.
The end 37 of the left-hand hale 35 of the
outer layer 2 oE FIG. 3 can be trimmed prior to
attachment of t'he end 38 of t'he other strip 3 if the two
strips are convoluted onto the core one a-Eter the other.
The tensioning of the second strip 3 (during winding onto
the core 1) is preferably identical -to the tensioning of
the first strip. The strips 3 are severed (at 5 and ~)
when t'he ma]cing oE the respective 'halves 35, 36 of t'he
outer layer 2 is completed.
If a machine is used Eor the treatment of
different types of webs 17, i-t can be furnished with two
or more identical cores 9 each of which carries a
different outer layer Z. This renders it possible to
simply replace a first expander roller with a different
second expander roller if the machine is to be set up for
the unwinding, conveying, winding and/or other -treatment
of different webs each of which is to be stretched or
expanded by a different outer layer 2.
If a machine is to employ a very long and heavy
expander roller, the core 1 o-E such roller can be
installed in the machine at the locus of use of the
assembled roller, and the strip or strips 3 are
convoluted onto the thus installed core. An advantage of
- 18 -
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such procedure is that it is not necessary to employ
specially designed lathes or other machines for temporary
installation and rotation of a very long and heavy core;
instead, such core is rotated by the drive which is used
to rotate the Eully assembled expander roller in a paper
making plant, in a textile factory or in another
establishment wherein webs of paper, tex-tile, foil or
other material are to be convoluted on rol].s, paid out by
rolls and/or otherwise treated or manipulated and the
treatment or manipulation involves elimination of crea.ses
or analogous irregularities and/or prevention of
development oE such irregularities in the webs.
FIG. 6 shows the effect of the improved
expander roller upon a running web 17. The latter is
assumed to run upwardly, as seen in FIG. 6, so that the
irregularities 68, 69 :in the web portion 66 ahead of the
stretching station disappear or become less pronounced as
a result of engagement by the external surface of the
roller, and the web portion 67 downstream of the expander
roller is devoid of creases or the creases are less
pronounced and are uniformly or nearly uniformly
distributed across the width of the treated web. The
elimination or flattening and distribution of
irregularities 68, 69 is attributable to the provision of
grooves (the grooves 15 are shown in E`IG. 6) as well as
to the provision of the adjacent lips 45. The grooves 15
and the lips 45 further eliminate or uniformly distribute
internal stresses (if any) in t`he running web 17
Internal stresses in the web portion which is about to
contact the external surface of the outer layer 2 (a-t 70
- 19 -
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in FIG. 6) are uniformly distributed at the open 5 ides of
the grooves 15, and -the irregularities 6~, 69 are
eliminated or weakened and distributed across the width
of the web under the action of the lips ~S. The lips
undergo deformation to vary the width of open sides of
the adjacent grooves 15, and such deformation of the lips
45 ensures predictable elimination or desirable uniform
distribution of internal stresses in the oncoming
por-tions of the running web. ~t the same time, the lips
45 stretch or expand the running web in directions from
the center of the roller toward both ends of the core 1
with attendant elimination or weakening and d~stribution
of irregularities 6~ and 69. Extensive flexing of the
lips 45 will influence the running web 17 in a number of
ways, such as by bringing about the aforediscussed
~; stretching with attendant at least subs-tantial
elimination of irregularities as well as by eliminating
or homogeneously distributing internal stresses in the
material of the running web.
An important advantage of the improved expander
; roller is its simplicity. Thus, the strip or strips 3
can be pretreated (formed with one or more grooves of
desired inclination, depth and width) prior to winding
onto the core 1. This is simpler and less expensive than
the grinding or other machining of grooves into the
external surface of a one-piece hollow cylindrical outer
layer which already surrounds the core. The adhesive
which is used to bond the strip or strips 3 to the core 1
can be selected with a view to permit removal of the
outer layer preparatory to treatment of the peripheral
`:
- 20 -
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surface 9 for reception of a different outer layer.
This, too, contributes to versatility of the improved
roller and reduces the overall cost of the machine in
which the roller is put to use. The strip or strips 3
can be mass-produced in an available extruding machine
which can turn out considerable lengths of strip material
per unit of time. All this contributes to lower cost of
the improved roller. Replacement oE a first ~uter layer
2 with a fresh outer layer wherein the exterrlal surface
16 has a different profile which i5 best suited for the
treatment of a particular w~b can be completed at a small
Eraction of the cost of a new expander roller,
particularly a conventional roller wherein the core must
be provided with a homogeneous one-piece outer layer of
rubber or the like and the external surface of such outer
layer must be treated in a grinding or other material
removing machine to provide a proEile which is capable of
stretching a running web.
The diameter of the external surface 16 of the
improved roller can be selected in dependency upon the
characteristics of the web 17 by the simple expedient of
utilizing one or more thicker or thinner strips 3 and/or
by properly selecting the tensional stress upon tha strip
or strips during winding onto the core 1.
It has been found that the improved expander
roller can be used for highly satisfactory treatment of
all kinds of running webs including webs made of any one
of a variety of different materials as well as wide or
narrow webs and readily flexible or relatively stiff and
relatively thin and relatively thic1c webs. The running
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0
web can be maintained in large-area contact with the
outer layer 2 because the lips of the ou-ter layer are or
can be readily deformable. This is particularly
desirable when the improved roller is to treat a
relatively thin and readily ~lexible web which would be
likely to develop pronounced creases, fold lines and/or
other irregularities as a result of engagement with rigid
radially outwardly projecting portions of the outer
layer. The open sides o-f the grooves 15 and/or
additional grooves permit entry of irregularities (such
as those shown at 6g and 69 in E'IG. 6) to thereupon
dis-tribute the irregularities all the way between the two
marginal portions of the web and to thus contribute to
the development of less pronounced irregularities or to
render the treated portion of the web devoid of any
creases or the li`ke. E'urthermore, uniform distribution
of internal stresses across the width of the running web
reduces or terminates the tendency of the web to develop
creases or other irregularities on its way beyond the
improved expander roller, e.g., toward and onto the core
of a takeup reel.
The convolutions of each strip 3 on the
peripheral surface 9 of the core 1 are preferably
- immediately or very closely adjacent each other so that
the external surface 16 of the thus obtained outer layer
16 is a cylindrical surface which is interrupted only at
the locations of intentional profiling, i.e., in the
regions of open sides of the grooves in the strips 3~
rhe outwardly extending portions 59 of the lips (at the
respective edges 53) are first to be contacted by the
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adjacent side of a running web 17. Tllus, such lips can
eliminate or distribute internal stresses even before the
web reaches and engages the major portion of the external
surface 16. The distribution of internal stresses is
completed not later than when an increment of the running
web advances beyond the external surface 16. As
mentioned above, this greatly reduces or terminates the
tendency oE the web to develop fresh wrinkles, creases,
'! fold lines and/or other irre!gularities.
The lips of the outer layer 2 react to
characteristic vibrations of the running web 17. Such
characteristic vibrations depend on the length of
unsupported portion of the web upstream and/or downstream
of the expander roller. Furthermore, characteristic and
other vibra-tions of the running web depend upon the
extent to which the web is guided and restrained against
stray movements on its way toward the roller and/or upon
the extent (if any) to which the roller is running out of
` true.
As mentioned above, it is possible to form the
entire outer layer 2 from a single strip 3 or from three
~- or more strips. The utilization of two strips 3 and the
^` winding of two strips in a manner as shown in FIG. 1, 3
and 6 is preferred at this time for three important
reasons, namely: The two mirror symmetrical halves 35,
36 of the outer layer 2 ensure a highly satisfactory and
uniform stretching of the running web 17 from the
abutting ends 37, 38 of the strips 3 at the center of the
roller toward both ends of the core 1. Furthermore, the
`~ 30 two helical grooves 15 or the two sets of helical grooves
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.~
:~ .
: . :
:
3~3~70
;
ensure a desirable distribution and homogenization of
internal stresses even before the running we~ 17 comes
into large-area contact with the external surface 16 of
the outer layer 2. Moreover, the flexible lips of the
outer layer produce a desirable damping action of the
locus (70) of initial contact with the running web 17 and
at the locus where the web advances beyond the external
surface 16.
The shape of the lips depen~s upon a variety of
factors, such as the dia~eter of the external surface 16,
the tension of the strip or strips 3 during winding onto
the core 1, and the material oE the strip or strips.
Some or all of these factors are taken into consideration
during making of the improved roller in order to ensure
optimal treatment of the webs. Moreover, it is possible
to balance various parameters in order to enhance the
versatility of the roller, i.e., a relatively small
; number of rollers will suffice to ensure adequate
treatment of any one of a variety of different webs, such
as thick or thin webs, wide or narrow webs, strongly
; creased or relatively smooth webs, webs which are
accurately guided during advancement toward contact with
the outer layer of the selected roller and/or webs having
long unsupported stretches ahead o the expanding or
stretchin~ station.
The lead of convolutions on the core 1 will
depend on the width of the strip or strips which are used
to make the outer layer 2. Another factor which
determines the lead of convolutions (and hence the
stretching action) is the hardness or elasticity of -the
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~ J~3~7(1
material of -the strip or strips. 'I'he roller i5 ready for
use as soon as the strip or stxips are applied to and
adhere to the peripheral surface ~ of the core 1, i.e.,
it is not necessary to subject the thus obtained outer
layer 2 to any additional treatment. The roller can be
inserted into and removed from the frame of the web
treating machine as often as desired without any
alterations of the roller and/or of other parts oE t'he
machine. ~ roller can be main-talned in a position of
readiness to replace the previously used roller as soon
as the treatment of a particular web or a series of
': identical or similar webs is completed.
,
It is further within the purview of the
invention to employ strips 3 which have exactly parallel
lateral surfaces 10 and 11. It is presently preferred to
employ strips with convergent lateral surfaces (i.e.,
strips wherein the width 31 at the external surface 16 of
the finished outer layer 2 is greater than the width of
the inner sides 12) because such strips render it
possible to form an external surface 16 which is
interrupted only and alone where actually desired, i.e.,
at the gaps which are intentionally provided in the
strips prior to winding of such strips onto the core 1.
This is particularly impor-tant when the strip or strips 3
are relatively narrow so that they would tend to bulge
outwardly at the external surface 16 of the finished
outer layer 2, especially if the lead of the convoluted
strips is rather pronounced. As a rule, neighboring
convolutions of a strip 3 which surrounds the core 1 will
be placed close to each other so that the lateral surface
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10 abuts the lateral surface 11, at least in the region
of the external surface 16. This reduces the tendency of
neighboring convolutions of a web 3 to shift relative to
each other upon completion of the outer layer. The
extent of frictional engagement between abutting surEaces
10, 11 on neighboring convolutions of a strip 3 can be
selected with a view to avoi.d any undesirable stray
movements of portions of the strip or strips relative to
the core. However, it is also possible to intentionally
design the outer layer 2 in such a way that the
neighboring convolutions of each strip 3 define
clearances of selected width. Such clearance3 can act
not unlike additional gaps or slots.
.~
:`
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