Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVE~TION
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The present invention relates to rollers and, more
particularly, to a hard surface fluid roller of the type having
a random crack configuration formed in the surface thereof.
Fluid transfer with cylindrical rollers has for years
been an integral element in various industrial fluid systems.
The precise roller design most often depends on the specific
application, fluid viscosity, speed and related aspects. For
example, fluid rollers are used in the printing industry in
several distinct areas, ink is transferred over rollers in inking
systems; fountain solutions are transferred over rollers in
dampening systems; coatings, pigments and dyes are transferred
directly to webs of paper, cloth and the like. This is but one
example ofa class of fluid roller applications and, for purpose of
example only, reference will be made herein to printing systems.
Still, said reference is for example only and is not meant to
limit the scope of the present invention which finds application
in the transfer of fluids of varying viscosities to a wide assort-
ment of mediums.
Referring now to large lithographic printing presses in
particular, a system of fluid dampening is generally utilized
in conjunction with an inking system. The use of a dampening
system requires controlled transfer of the dampening fluid
through a plurality of rollers within the press. The transfer
of the fluid must be in both controlled speed, thickness, and
uniformity for printing quality and the elimination of streaks,
runs, smudges, and other problems associated with lithographic
printing.
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The problem of fluid transfer control is not, however, limited
to lithographic printing and is a specific requirement and need
for many industries having various forms of roller applications.
One of the greatest problems of lithographic offset
printing methods has been the application of moistening fluids
to the surface of the lithographic printing plate in uniform
and evenly distributed quantities and in regulated amounts so
as the insure uniformly good quality reproduction o~ the printed
image on the paper. A lithographic printing plate is a chemi-
cally treated sheet of metal wherein the printing area is pro-
vided to be ink receptive and the nonprinting area to be
hydrophilic, or moisture receptive. It is therein necessary to
apply a film of moistening fluid to the surface of the plate which
is retained by the hydrophilic area, but is repelled by the
printing area so that the printing area receives ink and the
nonprinting area is separated and isolated from the ink by the
film of moistening fluid.
The prior art has provided numerous forms of roller
configurations and surface characteristics for the printing
industry, included among these, a polished, chrome plated dam-
pener transfer roller for use in lithographic dampening. Such
a roller is disclosed and claimed in U. S. Patent No. 3,259,062
to Dahlgren. The following patents also disclose such roller
designs: 3,647,525 to Dahlgren, 3,508,489 to Norton, 3,168,037
to Dahlgren, and 3,433, 155 to Norton.
The chrome plated roller generally described in the
prior art incorporates a smooth, polished chrome plated surface
being very hard in surface characteristic and very smooth f~
facilitating dispersion of a film of fluid thereupon.
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The utilization of the chrome plated hydrophilic transfer has
thus found widespread acceptance in the printing industry,
although certain requirements in the lithographic press are
necessarily associated therewith. One such requirement is the
utilization of a surfactant or wetting agent such as alcohol,
in the dampening solution transferred by the transfer roller.
The use of alcohol reduces the surface tension of the dampening
fluid permitting it to uniformly disperse itself across the
polished, homogeneous surface of the subject roller. Alcohol
has become however, very expensive and more scarce with contem-
porary oil shortages.
The prior art of roller construction has also included
rough surface rollers of the type shown and described in U. S.
Patent No. 3,285, 169 to Hartwig. Various rough surface rollers
have also been disclosed with soft surface characteristics,
although not as successful. The teachings of the Hartwig
patent illustrate the advantages of certain aspects of hard,
rough surface rollers such as an "Anilox" roll. One such
advantage is the ability to carry greater fluid thicknesses due
to the characteristic of the surface to fluid interface. The
use of such prior art rough rollers produced real problems in
operation. For example, such rollers are generally copper
clad and surface plated which results in a surface which is
easily damaged. Moreover, ink from the inking system often
becomes embedded in the deep cracks on Anilox rollers. Other
problems such as surface friction, emulsification, fluid tur-
bulence and the resulting uniformity of flow has thus prompted
the industry to utilize other transfer roller designs. The
advent of the smooth, polished hard surface hydrophilic roller
was thus a major development in that the critical disadvantages
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associated with rough rollers both hard and soft, were overcome.
However, elimination of the disadvantages also obviated many
of the advantages of the rough surface roller in the system
itself. The same holds true for related industrial roller uses
and the need for an improved fluid transfer roller is critically
felt.
In any fluid transfer system where fluid rollers rotate a~
different surface speeds, as is often the case for controlled
operation, the surface configuration of the rollers has a direct
bearing on the amount of energy consumed to impart rotation.
For example, a rough surface rolle~ rotating at a different
speed than a contiguous roller in surface indented relationship
therewith will obviously ~ave high frictional consid~raiions.
For this reason, hard polished rollers often require less dri-
ving energy to operate against a pressure indented roller rotating
at a different speed. Where viscous fluids, such as polymer
coatings are being transferred, the surface friction is even
greater and the need for quantity transfer more evident.
It would be an advantage therefore to provide the advan-
tages of a rough surface roller in a roller construction having
many of the advantages of the smooth polished roller. The
roller construction of the present invention overcomes many
of the problems of the prior art and provides a roller having
a surface configuration facilitating fluid transfer having the
advantageous features of many rough surface ~ollers and features
of smooth polished hard surfaced rollers. The functional combi-
nation is facilitated through the creation of precisely etched
surface crack configurations in a very hard surface material
uniformly disposed and polished about the roller. The nonuniform
polished surface and interconnected cracks of the roller of the
present invention provides vastly improved fluid transfer cha-
racteristics with few of the conventionally associated problems.
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SUMMARY OF THE INVENTION
The present invention relates to fluid transfermethods using cylindrical rollers, more particularly, one
aspect of the invention includes an improved method of trans-
ferring the fluid between hard and soft surfaced, cylindrical
rollers in a fluid transfer system of the type wherein the
hard surfaced roller is rotated relative to the soft surfaced
roller in pressure indented relationship and fluid is passed
therebetween. The improvement comprises the steps of
providing a cylindrical core plated to a predetermined
thickness with a hard surface material and adapted for rotat-
able mounting as a hard surfaced roller in the fluid transfer
systems. The core is etched to a predetermined depth to
remove substantial portions of the plated material and impart
a relatively dense, random pattern of relatively deep inter-
connected cracks in the remaining surface. The surface of
the etched core is polished to reduce the depth of the
interconnected cracks to between .001 and .002 inches and the
density of the interconnected cracks to between 9 and 26
percent of the surface area of the roller for producing a
random pattern of isolated, smoothly finished lands between
the cracks. The surface is cleaned to render it fluid
receptive upon the polished surfaces of the lands in the
interconnected cracks therebetween. The hard surfaced roller
is then mounted in pressure indented rotational engagement
with a soft surfaced roller and provided with a fluid to be
transferred to the surface of one of the rollers for transfer
thereupon. The hard and soft surfaced rollers are rotated
to transfer fluid upon the surfaces thereof and pass the
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fluid between the rollers while imparting lateral fluid flow
within the interconnected cracks of the hard surfaced roller
to the fluid passing between the rollers for providing
dynamic surface action and reducing laminar flow during the
fluid transfer.
In another aspect, the above fluid transfer method
includes the step of imparting lateral fluid flow between
the hard and soft surfaced rollers while imparting turbulence
to the fluid and mechanically reducing the surface tension
of the fluid through fluid flow within the interconnected
cracks. The hard surfaced material plated upon the core
may be chromium wherein the step of etching includes
emersing the core into hydrocloric acid ~o produce the
random pattern of relatively deep interconnect~d cracks.
In yet another aspect of the invention, the density of the
interconnected cracks comprise between 14 and 17 percent
of the surface area of the roller and the density of the
interconnected cracks comprise on the order of 15% of the
surface area of the roller. The step of providing a
cylindrical core plated to a predetermined thickness may
also include providing a core plated to a thickness of
chromium on the order of .020 inches and the step of
etching the core may include electroetching the core to
form the interconnected cracks at a depth on the order of
.010 inches.
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BRIEF DESCRIPTION OF THE DRAWINGS
.
For a more complete understanding of the present invention,
and for further objects and advantages thereof, reference may
be now had to the following description taken in conjunction
with the accompanying drawings in which:
FIG. 1 is a perspective view of one embodiment of a fluid
transfer roller of the present invention in a specific fluid
transfer application;
FIG. 2 is an enlarged cross~sectional view of the surface
of the transfer roller of FIG.l, illustrating one embodiment of
a crack pattern therein;
FIG. 3 is an enlarged, top plan view of the surface of the
transfer roller of FIG.l illustratinq in more detail one crack
pattern embodiment in accordance with the principles of the
present invention;
FIG.4 is an alternative embodiment of the crack pattern
illustrated in FIG. 3; and
FIG. 5 is an enlarged, side elevational cross sectional
view of the roller assembly of FIG. 1 illustrating the prin-
ciple of fluid transfer therebetween.DETAILED DESCRIPTION OF THE DRAWINGS
Referring first to FIG. 1, there is shown one embodiment
of a fluid roller 10 constructed in accordance with the prin-
ciples of the present invention. The roller 10 is illustrated
in pressure indented relationship with a second roller 12 for
facilitating fluid transfer therebetween and to material web 13,
in accordance with one illustrative application of the present
invention.
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A surface crack pattern 14 may be seen upon the roller 10. The
pattern 14 of the present invention is formed in a hard cylin-
drical outer surface 16 of the roller 10 in a manner described
below for imparting a select, non~continuous, non-homogeneous
surface thereto. In a dynamic operation mode, the pattern 14
of the roller 10 then provides all the advantages of both a con-
tinuous, smoothly polished roller and a rough, knurled, or
"Anilox" roller, without the associated disadvantages of either.
For example, the surface 16 is hard and impervious to "dings"
while exhibiting surface indentations in the form of the pattern
14.
Referring now to FIG. 2 there is shown an enlarged side
elevational cross sectional view of the surface 16 and pattern
14 of the roller 10 of FIG. 1. It may be seen that the pattern
14 is comprised of a vast, interconnected array of channels, or
cracks 18 formed in the surface 16 and extending therein a gene-
rally predefined depth and width. Between adjacent cracks 18
polished lands 20 form the surface of the roller 10. Each land
20 is segregated by the random patterns of cracks 18 isolating
one land 20 from another and permitting fluid flow therebetween.
In this manner the surface 16 of the roller 10 exhibits a non-
continuous, non-homogeneous surface to fluids dispersed thereon.
Fluids deposited on the surface in either a static or dynamic
mode will exhibit certain phenomena of rheology not characte-
ristic or either smooth or rough surfaces. For example, a dropof water placed upon stationary prior art rollers will generally
"bead up" unless treated with a wetting agent to reduce surface
tension.
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That same drop of water has been well dispersed across the sur-
face 16 of the roller 10 of the present invention as though a
wetting agent were present because of the interconnected cracks
18 which mechanically break down said surface tension. This
phenomena has equally startling results when incorporated in a
dynamic mode as described in more detail below.
Referring now to FIG. 3, there is shown an enlarged top
plan view of a section of the surface 16 of the roller 10 of
FIG. 1 in accordance with the principles of the present invention.
The cracks 18 may be seen to be in a random pattern of generally
uniform width and isolation relative to the lands 20. As used
herein, the term "random pattern" refers to the interconnected,
crack configuration providing the non-continuous, non-homogeneous
surface shown and described herein. The cracks are random in
configuration because of the formation process. However they
form a pattern of isolated lands 20 in a carefully controlled
ratio of crack size and quantity to land area. This aspect has
been found to be of critical im~ort in the construction of the
present invention. Another critical aspect shown in this figure
is the density of cracks 18 relative to the smooth lands 20.
The crack density illustrated in FIG. 3 is between 14 and 17
percent, and more particularly, on the order of 15% which has
been found to be preferable relative to dynamic operation modes
transferring relatively non-viscous fluids such as water. A
crack depth of .001 to .002 inches and similar width has likewise
been found to produce optimal results.
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Referring now to FIG. 4, there is shown an alternative
crack pattern density on the order of 20 percent. It may be seen
that the density figure is an average which denotes the surface
discontinuity relative to the smooth lands 20. The size of the
cracks 18 is preferably not effected. It has been found, however,
that as the crack density increases the tendency for pitted,
shallow, crack areas in the lands 20. This condition, when not
controlled to produce the smooth lands 20 shown in FIG. 3, is a
deviation from the crack pattern 14 of the present invention and
may result in a pitted roller surface much like earlier prior art
roller designs not affording the fluid transfer characteristic of
the present invention. Pitted surfaces of certain prior art
rollers do not exhibit lateral fluid flow in the cracks because
they are not interconnected. In the dynamic mode, this aspect
facilitates fluid transfer from fluid supply means provided under
pressure, such as pressure indented rollers. The term "pressure
indented" as used herein refers to that loading condition between
rollers wherein the surface profile of one or both is effected,
or indented, by the overlapping roller positions. In like manner,
~0 the crack pattern 14 facilitates deposit of the fluid to the
particular medium to which it is transferred because said fluid
is always flowing within the crack pattern 14.
Referring now to FIG. 5 there is shown an enlarged,dia-
grammatic view of one embodiment of the operation of the roller
10 of the present invention. Fluid is brought to the roller 10
by a second roller 22.
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This operation configuration is for purposes of example only;
any suitable means for providing fluid to the roller 10 would
be sufficient. It has been found optional to supply said fluid
under pressure and other means (not shown) may be provided for
said pressure arrangement. The second roller 22 conventionally
has a soft outer surface 24 for engaging the hard roller 10 in
pressure indented relationships, as shown a~ interface 26. A
supply nip 28 of fluid 30 is formed at the juncture of the two
rollers. Fluid 30 is then squeezed through the roller interface
26 and transferred along the roller 10. It is at this point in
the fluid transfer process that the advantages or problems of
the particular hard surfaced`roller are conventionally mani-
fested. The thickness of the resulting fluid film 32 on the
roller of the present invention has been shown in tests to be
both more uniform and greater in size than many other prior art
hard surfaced rollers. This is not to say, however, that certain
individual fluid transfer characteristics, such as film thickness
could not be matched by select prior art roller designs, but
such prior art designs also effect other transfer characteristics
previously discussed. For example, an "Anilox" roller will
transfer thicker film or fluid but often at lesser quality and
efficiency than polished hydrophylic rollers. Aside from the
fragility of copper clad plated rollers, when the surface tex-
ture of such a "rough" roller exceeds a critical value,
differential drive forces between rollers become a problem and
residue can build up in the cracks or pitted areas.
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MANUFACTURE: The manufacture of the roller 10 of the present
invention incorporates various techniques of plating and etching
some of which have been found successful in fabrieating the oppo-
site configuration to the roller 10 of the present invention:
hollow piston cylinders for engines. The cracks in such instances
are formed on the inside cylinder walls and are usually very
deep to carry oil for purposes of lubrication. Such methods
have been used and taught by various industrial plating companies
wherein chrome and iron plating is formed with crack patterns
of varying configurations and degrees. The crack pattern des-
cribed for piston cylinders enables the piston walls to exhibit
"pockets" for holding oil and reducing friction and wear. The
"pores", as they are often referred to, are electrically etched
into the hard metal surface. The plateaus, or lands 20, between
15 the pores are honed or polished to provide a true bearing sur- ,
face. Various electroplating-etching processes have been incor-
porated to provide the necessary surface smoothness porosity
characteristics. Since the surface characteristics of this pro-
cess have not been directed to date toward fluid transfer rollers
as described herein, the design parameters,or crack pattern 14,
have not been heretofore established and the prior art has not
recognized the viability of such an approach to a fluid transfer
roller.
The particular crack pattern 14 described herein for the
25 roller 10 has been shown by testing to be of synergistic genesis.
The rheology characteristics are neither like those of the smooth
or rough surface rollers of the prior art variety.
11;~9~47
Likewise, alterations of crack density, dimension and
configuration as defined herein, have shown to exhibit few
of the advantageous characteristics without the creation of
critical disadvantages. Therefore, while the process of
fabricating the roller 10 in accordance with the principles
of the present invention is only generally set forth as to
process steps, these steps will enable a man skilled in the
art to produce the roller of the present invention when
directing the process specifically to the pattern 14 specif-
ications herein defined. For purposes of example only,
Electro-Plating, Inc. of Houston, Texas has been able to
produce the specific roller configuration herein defined
when incorporating the below enumerated steps. It should
be noted however, that the fabrication of pattern 14 of the
roller 10 is achieved in part, at least, through artisan
skills in producing the intended and defined crack pattern
and surface condition described. The following process steps
are thus enabling to one so skilled in the art:
First, a cylindrical core is prepared for plating
with chromium or the like. The core is precisely aligned
relative to the plating anode for uniform plating there-
around. When the plated metal reaches a pre-determined
thickness on the order of up to .020 inches it is then
electroetched, as that term is known in the industry,
wherein the plating current is reversed to remove, portions
of the plated material. The interconnected cracks 18 must
be formed at this time and generally extend into the surface
14 a distance on the order of .010 inches, depending on the
thickness thereof.
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The etched roller is then honed or polished on a lathe or the
like to reduce the plating thickness, critically define the
surface dimension and configuration and produce the smooth uni-
form lands 20 and uniform crack depth in the configuration illus-
trated in FIGS. 1-4 and heretofore defined. The etching and
polishing step must be coordinated to produce a crack pattern 14
as defined herein rather than conventional etched porosity and/
or random crack depth density configurations. A crack depth
between .001 and .003 inches, has been found satisfactory. For
this reason the initial thickness of the plated metal upon the
cylinder core is often greater than usual for conventional plated
surfaces, the etching more controlled and the polishing critically
coordinated to the aforesaid pattern.
OPERATION: In operation the roller 10 is prepared for its
particular application by again etching the roller 20 with a
suitable agent such as hydrochloric acid for chrome surfaces, in
order to render all surfaces, lands 20 and cracks 18 fluid re-
ceptive. The roller ]0 is then mounted for rotation in the
particular systerl adjacent a fluid supply and deposit area for
transfer therebetween. As shown in FIG. 1 roller 10 may be
disposed against a soft surface roller, and each driven inde-
pendently of the other, or in unison. It has been found that
a degree of turbulence is imparted to the fluid film through
the rotational interface 26. The turbulence due in part to
lateral fluid flow in the cracks 18 substantially reduces the
laminar flow problems generally associated with smoothly fini-
shed rollers. For example, fluid rings or ridges can build
up in laminar fluid transfer on smooth, continuous hydrophilic
surfaces.
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The crack pattern 14 of the present invention alleviates such
rings through dynamic surface action. This aspect is particu-
larly useful in lithographic dampening systems where alcohol i~
often utilized in the dampening fluid or fountain solution to
reduce surface tension. The use of the crack pattern 14 of
the roller 10 reduces the need for alcohol, and such wetting
agents thus improving cost effectiveness in the system of appli-
cation.
In summary, the method and apparatus of the present inven-
tion provides a means for improving the transferability of fluid
with fluid rollers. For a given fluid viscosity, roller speed
and drive horsepower the roller 10 of the present invention will
provide a more uniform transfer of fluid with substantially fewer
transfer problems than with prior art apparatus. Additionally,
more viscous fluids can be transferred with the rollers of the
present invention than deemed operable by most prior art methods
and apparatus. It is thus believed that the operation and con-
struction of the present invention will be apparent from the
foregoing description. While the apparatus as shown and des-
cribed has been characterized as being preferred it will be
obvious that various changes and modifications may be made
- therein without departing from the spirit and scope of the
invention as defined in the following claims.
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