Note: Descriptions are shown in the official language in which they were submitted.
2137397
1
CYLINDER SURFACE FINISH PATTERN AND AN APPARATUS AND
METHOD FOR FINISHING THE SURFACE OF A CYLINDRICAL
WORKlPIECE
Introdulction
The invention relates to a surface fini~hing al~paldlu~ and process for
fini~hing and removing imperfections from the surface of a cylindrical workpiece,
and to the finish pattern achieved by the process and a~aldlus. More particularly,
the surfaLce fini~hin~ apparatus and process of the invention relate to preparing the
surface of a machined metal cylinder, such as a gravure cylinder, by finishing the
surface using an abrasive material.
Related Art
In the art of gravure cylinders of the type used on engraving al~pa,dluses
used for printing on paper or other media, and having a printing surface with ink
carrying depressions therein, it is well known that the metal surface, such as acopper surface, of a precision m~ehined cut gravure cylinder has imperfections that
would impede the process of engraving. It is therefore necessary to finish the
cylinder surface from time to time to a smooth level surface, to remove
irregularities that may affect print quality and clarity. Conventional means andmethods for doing this involve grinding and finichin~ the cylinder w~th fine
polishing stones. The process may take hours to complete to obtain the required
finish.
1'he standard process for fini~hin~ gravure cylinders involves polishing a
m~hined copper plated gravure cylinder with polishing stones, using stones of
about 3()0 grit. The stones are mounted to a stone plate by means of contact
cement a~d the composite plate and stones are mounted to a stone driving head.
The head is brought into contact with the rotating cylinder and travels back andfor~l across the cylinder until a finish is achieved. The finish provides finishing
cuts in substantially one direction along the face of the cylinder. The standard
I 1 ~1373~7
F
process suffers from a well known problem in the art, namely that imperfections
remain lon the cylinder surface such that surface streaking results.
One prior art device for polishing gravure cylinders is the PolishmasterTM
apparatus which is a computerized precision machine that cuts a copper plated
5 gravure cylinder to an exacting size. The cylinder turns slowly and the diamond
head of the Poli~hm~tc-rTM device is moved across the face of the cylinder cutting
a 300 rnm swath around the cylinder. The PolishmasterTM has two cutting modes,
rough cut and fine cut. The finish pattern provided on the face of the cylinder
using the Poli~hm~terTM device is a longitudinal cut pattern, and the surface is not
10 repeatable from cylinder to cylinder. Due to the pattern of surface cuts in the
finish provided by the Poli~hm~t~rTM device, the cylinder must be polished by
hand with abrasives or by polishing stones onee the eutting with the deviee is
complete.
US Patent No. 5,224,300 to Pineau, titled "Machine for the Abrasive
Machining of Cylindrical Parts", issued July 6, 1993, describes an apparatus
comprising a number of bands of adhesive cloth having grains of increasing
fineness in the lonpit~ in~1 direction of motion of the parts to be machined. Inuse, bands of eloth are advanced into eontact with the maehine parts and then
rewouncl onto a reel of worn cloth. The cloth is pressed onto the m~chine parts
20 with a predeterrnined pressure to apply a maehined finish to the surface of the
parts. The part may be oscillated so that the entire part is abraded without
oscillating the cloth. Pineau discloses an alternative fini~hin~ method and
~udlus, but it has been found that maehining in substantially one direction
provides a finish with longitudinal cuts in the direction of m~hining, and the finish
25 pattern produeed on the part's surfaee will not be satisfaetory for printing.
It is apparent from the foregoing that an improved surface fini~hing
apparatus and a process for fini~hing gravure cylinders, and other cylinders would
be advantageous. In particular, it is well known that for machines on which the
cylinders are refinished and cleaned in plaee, long periods of down time are
373~7
.~
required for finishin~ and cleaning, and the residue created by certain finishin~r
methods is disruptive and disadvantageous to efficient gravure printing m~chine
operatio:ns. Further, it is a~a~ t that there is a need for a finish pattern with
fini.shin~r cuts laid down during finishing that do not follow a single machine
S direction, i.e. cross-wise or lon~it~ltlin~l, and which results in a minimum of
streaking and with a minimum of imperfections on the gravure cylinder surface.
Summary of the Invention
Accordingly, the present invention overcomes the major disadvantages of
the prior art, particularly in that it provides for fini.shing of the cylinder off or in
10 place on. the printing a~aL~Lus by driving a polishing pad with abrasive material
over the surface of the cylinder in a substantially circular motion providing a
surface capable of producing clarity of printing that surpasses known finishin~
techniqu.es. The finish pattern created gives the cylinder surface a roughness that is
substantially the same in the direction of the axis and the radius of the cylinder.
l he present invention also provides for finishing of the cylinder surface in
the direction of the web, which is discouraged in other known methods of gravurecylinder finishin~r. The abrasive material used for finishin~ the cylinder surface
may be easily changed and allows for selection of custom fini.~h~s By ch~n~rin~rabrasive grades, cylinder rotation, and/or carriage speed, the degree of surface20 roughness provided by the surface finishing app~lus may be increased or
decreased, as desired. Since the finish of the cylinder controls the movement of the
web over the cylinder, the consistency of the finish achieved by the invention
allows for improved control of the web over known finish~s.
In one aspect of the invention, a gravure cylinder has a metal printing
25 surface with a finish pattern of substantially continuous arcs over substantially the
entire surface to be used for printing. The series of arcs define lines or cuts on the
surface with defined spaces therebetween, and the line and space configuration is
substantially consistent over the printing surface.
73~7
In another aspect of the invention, a fini~hing apparatus for fini~hin~ the
surface of a cylindrical workpiece comprises a polishing pad having a polishing
side Wit]l an abrasive material applied thereto, and having flexibility to conform to
the curvature of the surface of the workpiece. Gripping means are provided for
5 holding the polishing pad under tension when the polishing side of the pad is in
fini~hing engagement with the surface of the workpiece. Drive means drive the
polishing pad in substantially circular motion when the pad is in finishing
engagement with the surface of the workpiece.
In a further aspect of the invention, a process for fini~hing a surface of a
10 cylindrical workpiece comprises the steps of (1) providing a flexible polishing pad
having an abrasive side for fini~hing engagement with the surface of the workpiece;
(2) bringling the abrasive side of the polishing pad into contact with the surface of
the wor~piece to be finished; and (3) driving the abrasive material in substantially
circular motion on the surface of the workpiece to remove irregularities from the
1 5 surface.
It should be understood that the invention is equally applicable to fini~hing
cylindrical or similar surfaces on devices other than gravure cylinders, and although
the surface material described is metal, other surface materials, such as wood, or
harder surfaces, may also be finished employing the al)pal~lus and process
20 described and claimed herein.
1 he terms "substantially circular", "circular motion", "substantially circular
path" or "circular" have been used to describe the cuts or lines in the gravure
cylinder that are laid out in a repeated, crisscrossed, crossed over or overlapping
fashion on the cylinder surface by the abrasive material used to fmish the cylinder
25 surface ~md provide the desired finish pattern. It is not intended to restrict the line
or cut pattern to a series of circles, and it is intended that ellipses, arcs, circles, or
other lines be included. The term "subst~nti~lly circular" is used here as it isparticula!rly suited to a description of the invention wherein the drive means for a
373~7
polishing pad is a motor that drives the polishing pad in an orbit about a mounting
post for supporting the drive means.
The invention will be further described in the following detailed description
with reference to the drawings in which:
S Brief Dcse.;~lion of the Drawings
Figure lA-lC are photographs of a surface of a gravure cylinder,
finished using the surface fi ni~hing al)paldlus of the invention (Fig. lA), a standard
stone process (Fig. lB), and a Polish m ~tçrTM device (Fig. lC);
Figure 2 is a side elevation view of the surface fini~hing a~paLdLu~ of the
10 invention, partially cut away, shown in position for fi ni~hing a cylinder mounted on
a lathe cross slide;
Figure 3 is a top plan view of the a~aldlus of Figure 2;
Figure 4 is a side elevation view of the surface fi ni~hing d~ UdlUS of Figure
2 shown in an untensioned position mounted on a lathe cross slide; and
lS Figure SA-SB are photographs taken at 20 X .S times actual size of thefinish pattern of the copper surface of a gravure cylinder finished using the device
of Figure 2, taken after completion (Fig. SA) and during the fi ni~hin~?; process (Fig.
SB), respectively.
- . . ~137397
Detailed~ Dev~ ,lion
~ plerell~ed embodiment of the surface finish pattern of the invention on a
cylindric:al workpiece that is a gravure cylinder having a metal surface is shown in
Figures lA and 5A. The surface fini~hinp; appa,~lus and process described herein5 provide greater detail of the surface finish pattern. However, the finish pattern
comprises lines or cuts 200,201 in a pattern subst~nti~lly as shown in Figures lA
and 5A, and the lines or cuts 200,201 are laid down in the same direction as thegravure cylinder rotates. The application or contact of abrasive material over the
cylinder surface leads to a finish pattern which appears as a spiralling or otherwise
10 substantially continuous series of a substantially circular pattern of lines or a
pattern of arcs over the entire printing surface of the finished cylinder surface. The
crisscrossing or overlapping lines or cuts 200,201 create spaces 210 therebetween
and the lines and spaces configuration is subst~nti~lly consistent over the entire
finished surface, in the axial or radial direction, creating a finish pattern which is
15 constant and repeatable. The "geometry" or repeatable aspect of the finish pattern
provides for good print performance, clarity and consistency.
l'he finish pattern achieved is characterized by a pattern of linear cuts on
the cylinder surface, which pattern of cuts runs in the same direction as the
cylinder rotates in use, yet the cuts are created by a repeating pattern of
20 overlapping arcs applied by an abrasive material. The abrasive material is on a
polishing pad used in the fini~hing process and is brought into contact with thecylinder surface. The polishing pad is driven in a repeating, subst~nti~lly circular
path, or a Lc;~lhlg series of continuous arcs, over the rotating cylinder surface,
and the cuts in the cylinder surface left by the abrasive material provides the finish
25 pattern.
E~igures lA-lC are offered as comparisons of the surface characteristics of a
cylinder finished using the process and apparatus of the invention (Figure lA), of
the standard stone process (Figure lB), and the Poli~hm:~ter fini~hing device
21~7397
-
- (Figure IC). It has been found that the linear pattern of the surface shown in
Figure lA, and shown in Figure SA, which is applied in the same direction as thecylinder rotates, with repeating cut lines or arcs 200,201 that crisscross or overlap
each other and create intermediate spaces, enhances the print quality of the finished
5 product. The pattern of the finish allows even lubrication of the cylinder face,
reduces surface tension between the cylinder and the doctor blade, and extends
doctor blade and cylinder life. The substantially circular motion results in a
precision finish pattern that is repeatable and consistent. As shown in co~ )ald~ e
photographs SA and SB, the surface roughness changes on fini~hing so that the
10 surface il~lnish will have a maximum peak-to-valley roughness height (R max),reading of under Rt.S in both the radial and axial direction of the cylinder surface.
The R max is the distance between two lines parallel to the mean line which
contact the extreme outer and inner points on the profile within the rol1ghnes~
samplinp length. Figure SA is a photograph showing the finished cylinder surface15 using the fini~hing apparatus herein. Figure 5B is a photograph taken under the
same conditions but of a cylinder surface showing an intermediate finish patternwhen the fini~hing a~pa~dlus was inL~l,~Led during the fini~hin~ process. Figures
5A and 5B illustrate the substantially circular pattern of the lines or cuts from the
abrasive material over the cylinder surface that leads to the desired surface finish
20 pattern. The finish pattern appears as a spiralling or repeating series of lines or
arcs and~ is repeating or consistent in coverage over the entire printing surface of
the fmished cylinder. The line and space configuration, intermediate spaces being
shown as 210 on Figures lA, 5A and 5B, is approximately the same over the
finished area. The geometry of the finished surface is responsible for the improved
25 performance and print quality achieved, including reduced streaking and consistent
engraving of tones and tints through repeats.
To produce a desired finish pattern on a metal cylinder surface, a preferred
embodiment of the surface fini~hing apparatus of the invention, shown in Figure 2,
may be used. The surface fini~hing ~paldl~ls 1 is shown in fini~hinp; engagement30 with a surface 3 of cylinder 2 mounted for rotation on a lathe cross slide 4. The
polishing pad 6 of the apparatus 1 is held under tension by gripping means 8, and
.
is driven in a substantially circular path by drive means, such as motor 12. Thetension on the polishing pad 6 is adjustable using tension adjust assembly 14.
I`he a~ dLus will be described according to the elements involved in
preparing for fini~hing a cylinder surface. The polishing pad 6 with a suitable
S abrasive material 22 is selected and clamped in gripping means 8. Using tension
adjust assembly 14, the tension on the pad is adjusted to suit the cylinder to be
finished, and the motor 12 is then activated to drive the pad 6, alnd the abrasive
material 22, in a substantially circular path in fini.~hing engagement with a portion
of the cylinder surface 3, as the cylinder rotates in the direction of arrow A.
The polishing pad 6 is a flexible, elongated pad, preferably of a nitrile
rubber construction, and has an underside 20. The underside 20 may have an
abrasive material 22 applied thereto for abrading the surface of the cylinder during
finishing, or the abrasive may be a separate element adjacent underside 20.
Preferab~ly, the abrasive material is an abrasive paper and it has been found that a
15 600 grit paper provides a suitable finish to a copper cylinder surface, although
other m~terials and roughness factors may be used. The abrasive material is
selected according to the finish to be applied to the cylinder surface and will be
selected from available materials. The fini~hin~ ~paldlus fini~hes m~hined
copper plated cylinders and other cylinders with all grades of finishin~ or polishing
20 abrasives, including paper backed or film-backed abrasives. The finish pattern
performs well on all printing substrates, including board, film, poly materials, and
cello materials, for example. The 600 grit paper was found to be particularly well-
suited for use on copper surfaces, and provides excellent engraving and printingquality, as well as excellent surface characteristics for doctor blade lubrication and
25 cylinder control of the press register. The finish pattern created on the copper
plated cylinder surface by the surface fini~hing al)~aLdLus using the paper abrasive
gives the cylinder surface a roughness that is substantially the same in the direction
of the a~xis and radius of the cylinder. The achieved finished pattern and surface
roughness gives greater register control of the cylinder and print substrates in the
30 press. Although 600 grit paper is exemplified here, other grade abrasive paper
- 21~73~7
-- . ,
would be suitable, and the particular grade applicable under existing circumstances
would be obvious to one skilled in the art without undue experimentation. The
abrasive material selected will depend upon the surface to be finished and on the
finish pattern desired. As an example, 400 grit paper may be suitable for a coarse
finish, and 2000 grit paper may be suitable for a very fine finish. Similarly,
lapping paper or a fini~hing compound may be used if the finish desired is a
polished. surface.
Referring also to Figure 3, the gripping means 8 are provided by a first
(leading edge) pair of gripping plates 30a,30b and a second (trailing edge) pair of
gripping plates 32a, 32b. The gripping plates 30a,30b and 32a,32b are spaced
apart, opposed pairs of plates having surfaces with fasteners such as bolts 58 for
releasably holding the polishing pad when the polishing pad 6 is aligned. Acting as
jaws, the pairs of opposed gripping plates are brought together and fastened to
securely hold the ends of the pad 6 and abrasive material 22. Each of the pairs of
gripping plates 30a,30b and 32a,32b is also secured to fixed elements of the
apparatus. Top leading edge gripping plate 30a has a flange 33 having spring
receiving openings 34 therein. Each spring 35 has one end 36 engaged in opening
34 on fl~ange 33 and a second end 37 engaged in an opening 39 on post 38 on
lower housing 16. The top trailing edge gripping plate 32a is longer than the
bottom plate 32b, and provides a surface for openings 48 for connecting end 43 of
spring 42 to plate 32a. A second end 44 of spring 42 is connected to plate 46,
such as by being received in openings 49 in plate 46. The plate 46 may be
secured against movement and is connected to housing 72, which is part of the
tension adjust assembly 14, described in greater detail herein.
Referring to Figures 2 and 3, the a~ hment of the polishing pad 6 to plate
46 and post 38 via spring 35 by ends 36,37 engaged in openings 34,39 and spring
42 by ends 43,44 engaged in openings 48,49 is appalellt. From the plan view
shown in Figure 3 it is also seen that multiple biasing elements, such as springs 35
and springs 42, may be used for controlled movement of the polishing pad 6 to
achieve balanced tension across the polishing pad 6.
- . ` 2137397
Im Figures 2, 3 and 4, additional restraint means, such as rubber strips
54a,54b,55 (shown in Figure 4),56, are shown. These strips are fastened to one of
the gripping plates 30a,30b,32a,32b and a fixed element, such as post 38 on
housing 16, or plate 46, such as by fastener 59. The rubber strips 54a,54b,55,56 are
5 positioned under or over springs 35,42.
F~eferring to Figure 2, tension adjust assembly 14 is supported by lathe post
60, and is made up of a T-bar 62 having rod 64 connected thereto, such as by a
close fit in a rod receiving opening (shown in outline as 66). At an upper end, the
rod has threaded opening 68 to receive screw 70. Screw 70 connects the rod 64 to10housing 72 when screw 70 is received in threaded bore 74 in the housing 72. Toadjust t~le tension, tension adjust knob 76 has threaded bore 78 for receiving the
screw 70, and a handle 79 is attached to the tension adjust knob 76 for ease of
adj~lstment Screw handle 80 is also provided for turning of the screw 70 in the
threaded bores. Lock nut 75 is provided to hold the screw 70 in housing 72.
15Referring to Figure 2, also attached to the lathe post 60 is cylinder wiping
bar 82 ~;vhich lubricates and cleans the cylinder surface 3 as it is finished. Wiping
bar 82 has head 83 and post 84 slidably mounted in channel 85b in arm 85. A
spring 85a is mounted in arm 85 for spring loading of the wiping bar, to allow
adjustment of the position of head 83 so desired pressure is applied to the cylinder
20 surface 3. The spring position can be adjusted using pins 85c which are slidably
mounted in openings (not shown) in arm 62 into channel 85a. On the head 83 is
provided a pad 83a which may comprise a felt pad for holding lubricant or a softnon-abrasive wiper. Particularly suitable is the wiper product known in the trade
and solcl under the trade mark WERIL WIPES, but other soft non-abrasive
25 materials may also be used.
The above describes the assembly of the apparatus for holding the polishing
pad in I`inishing engagement on the cylinder. The drive means, such as motor 12 is
the elen1ent of the apparatus that imparts the substantially circular motion to the
polishing pad to achieve the desired finishing and finish pattern of the cylinder
- ~137~
surface. As best shown in Figure 4, motor 12 is mounted to mounting plate 86
which is driven by the motor 12 in a substantially circular path, and is directly
attached to polishing pad 6 and abrasive material 22 via suction cups 88 fastened to
mounting plate 86 by fasteners 87. The preferred placement of the suction cups 88
S for engagement with the pad 6 and abrasive material 22 is shown in Figure 3, but
will be selected according to the materials used and the desired contact with the
cylinder surface. To achieve circular motion of the suction cups 88 which
translates into circular motion of the pad 6 and abrasive material 22 over the
cylinder surface, the motor 12 is controlled by a palm ring 90 and expansion finger
springs '~2 link the palm ring to the mounting plate. Each spring finger 92 has one
end com~ected to the palm ring 90 and another fastened to the mounting plate, and
the springs are equally and suitably spaced apart one from another at each
connection to provide stable translation of the forces provided by the motor. The
ends of the springs 92 are fastened such as by f~.~tening ends 93 eng~ging openings
94 in palm ring 90 and f~tening ends 95 eng~p~ing openings 96 in post 97 on
mounting plate 86.
For additional support of mounting plate 86, as shown in Figures 2 and 3,
springs g8 are provided, and have one end attached to post 99 on mounting plate
86, and another end attached to holding bar 100. Holding bar 100 is pivotally
connected to lower housing 16 by connection 101, and the connection may be used
to adjusl: the position of the mounting plate 86 to a prefelled angle with respect to
the lathc cross slide 4 which supports the lathe post 60 and the lower housing 16,
and elements supported thereon.
Referring to Figures 2 and 4, in use, the al)pal~lus 1 is fixed to the lathe by
mounting the lower housing 16 on lathe cross slide 4. Polishing pad 6 with
abrasive material 22 is clamped in position and held by pairs of by plates 30a, 30b
and 32a, 32b. Tension adjust assembly 14 is connected to plates 32a,32b. The rod64 is connected to T-bar 62, and lathe cross slide 4 on the lathe carriage is adjusted
from a frst position (shown in Figure 4) to a finishing position (shown in Figure
2). The tension on the polishing pad 6 and abrasive material 22 is adjusted by
7 3 g 7
- turrfing spindle 79, and thus tension adjust knob 76 so that screw 70 is brought into
or out of bore 74 in housing 72 and bore 68 in rod 64, and locked in position using
lock nut 75. The position of cylinder wiping bar 82 is also adjusted as desired,using spring loaded mounting arm 85, for contact with the cylinder surface 3 to
S provide a wiping operation.
For fini~hin~ the cylinder surface 3 the position of the mounting plate 86 is
selected by adjusting the longitudinal position of the cross slide S, and the tension
on the pad 6. The preferred position of the mounting pad 86 for fini.~hin~
engagement with the cylinder is substantially or approaching a vertical position so
10 that an arc on the cylinder surface from about the midline to the top centre is
finished by the abrasive material 22, although any position where the ~pLol,liate
fini~hinp~ engagement is achieved may be used. To lower the polishing pad from
an untensioned position into fini~hin~ engagement with the cylinder surface, the~p~alus is adjusted while in the position shown in Figure 4 by releasing
connection 101 and, as necessary, housing 16, and shifting holding bar 100 so the
lus, including the mounting plate, the polishing pad, and the drive means
and associated support elements, including the springs, gripping means and finger
springs, are adjusted and lowered to the position shown in Figure 2. The polishing
pad is then in fini.~hing engagement with the cylinder surface. The particular
20 contact point changes as the cylinder rotates in the direction of arrow A, and as the
a~)~h~Lus iS moved along the length of the cylinder as the lathe cross slide 4 is
adjusted for longitudinal movement of the appaldlus. The necessary adjllstment~ of
the cross slide 4, and the mounting of the lower housing 16 and the tension adjust
assembly 14 will be determined by the size of the cylinder to be finished. As an25 example, in the case of a 6" to 24" cylinder, generally it will be suitable to mount
the lower housing 16 on the lathe cross slide 5 at 23 inches from the lonprih~ n~l
axis of the cylinder 2. Further adjustments will be within the skill of a person in
the art, and will be made to suit the cylinder and the materials used in fini.~hing the
cylinder surface.
;- . . 21373g7
R.eferring to the Figures 2 and 4 in which the apparatus 1 is shown, the
method of the invention is related to the apparatus described herein. The process
for polishing or providing a finish pattern to the cylinder surface 3 involves
providing a flexible polishing pad 6 which has an abrasive material 22 and
5 bringing the abrasive material 22 into contact, in fini.~hing engagement, with the
cylinder surface 3 to be finished. The polishing pad 6 and the abrasive material22 is then driven in a substantially circular path to impart a pattern of repeating
lines or cuts 200,201 (shown in figure SA) and intermediate spaces 210 (shown infigure 51~) to the cylinder surface 3 to remove irregularities from the cylinder10 surface a~nd to prepare the cylinder surface for printing.
Through testing it has been found that a preferred finish with the finish
pattern described and shown in Figures lA and SA, is obtained using 600 grit
abrasive with the motor orbital speed at 15,000 rpm, the cylinder rotating speed at
360 rpm, and a carriage speed (the movement of the surface fini~hing apparatus on
lS the lathe along the length of the cylinder) of 40 mm per rotation of the cylinder.
In such circllm~t~nce, the cylinder fini.~hin~ time is approximately six inches per
minute. In selecting a finish pattern for the cylinder surface, it has been found that
the extent of finish pattern applied to the cylinder surface is increased if the orbital
speed of the motor of the surface fini~hing app~udl~ls is decreased and the carriage
20 speed is increased. To decrease the extent of the finish pattern, the carriage speed
is decreased and the orbital speed of the motor is kept the same or increased. The
amount of increase or decrease in speed is readily determined by kials to achieve
the desired finish pattern. In a l)rerelled fini~hin~ method of the invention, the
cylinder is put into rotation, preferably at 360 rpm, the polishing pad 6 and
25 adhesive material 22 are brought into contact with cylinder surface 3, and the
motor 1~2 is actuated so that palm ring 90 orbits, and finger springs 92 impart
substantially circular motion to the mounting plate 86. The suction cups 88 holdpolishing pad 6 in relation to plate 86 and cause the polishing pad 6 and abrasive
material 22 to move in a controlled circular motion. Springs 35, 42 move with the
30 polishing pad 6 and abrasive material 22 to allow movement of the whole of pad 6
and abrasive material 22. The portion of abrasive material 22 that contacts the
13~7
cylinder surface finishes the surface with a controlled motion which creates a level
surface in both the radial and axial directions of the cylinder. The resultant
controlled surface finish pattern is achieved by the action of the abrasive material
cutting a finish pattern on the cylinder surface in the direction of web travel in the
5 press.
It has also been found that the surface finish pattern produced by the above
described process and apparatus provides an improved, con~i~tçnt surface fimish
pattern, extends cylinder life, results in minim~l loss of engraved image, and
increases stylus life by reducing chipping. The print quality improvement results
10 from the unique finish pattern that results from the circular motion and action of
the abrasive material on the cylinder surface.
1 he 600 grit abrasive used on the surface fini~hing apparatus will be
recogniz:ed by a person skilled in the art as being other than the normal sized grit
paper used in the finishing of a machined copper plated cylinder being prepared for
15 an engr~ving machine. However, it is the controlled, precise motion of the surface-
finishin~ apparatus that allows the abrasive material to precision grind and finish
the cylinder surface to a geographic consistent level with a surface roughness the
same in both directions of the cylinder. These results are achieved by fini~hin~ the
cylinder surface in the direction of the web turning in the press. The direction the
20 cylinder is finished in is important for cylinder pull, doctor blade wear, and register
control of the web. These improved conditions will provide improved press start
up time and relatively trouble free running of web runs, compared to known
methods. The finish pattern created using the surface fini~hinp apparatus is
superior to finishes previously achievable using known methods to prepare gravure
25 cylinders for engraving, and is con~i~t~nt and repeatable from cylinder to cylinder.
14
2137~97
-
E~amplle
]_xtensive testing was conducted of the surface f;ni~hing a~dlus of the
invention, and to illustrate the excellent quality of printing achievable using the
micro-finisher, a 40% overall tint was engraved on the cylinder and tested for
S printabillity on a press. It was concluded that the cylinder printed streak-free. All
substrates used, which included board, film, paper, foil, metallized paper,
poly~rolJylene, acetate, and MylarTM were tested and were found to print equallywell. It was found that the surface fini~hin~ al~paldlus, using a 600 grit paperimproves the printing quality on all tested gravure printing substrates. Water based
10 inks and solvent based inks were used for printing, with the same quality of results.
A person skilled in the art of the invention will recognize that various
alternatives to the particular embodiments described will be functional and suitable,
and will provide the benefits of the invention. In particular, the gripping means
may include clamps, a unitary element with the polishing pad and abrasive
15 material, or any other device that will hold the polishing pad and abrasive material
for connection to a tension adjust assembly or similar device. The tension adjust
assembl~ is not intended to be limited to the embodiment described, and may
comprise other devices for supporting a connection to the dripping means and
permitting adjustment of the tension on the polishing pad. It is also contemplated
20 that a single tension ~pa~ s may be useful for applications where the tensiondoes not have to be adjusted, or where, for example, the gripping means or the
polishing pad provide for tension adjustment. The drive means herein is referred to
as a motor, and it is intended that all manner of driving the pad over the cylinder
surface, whether mechanical, manual, or other, be included in the invention. These
25 alternatives are contemplated by the inventor, are believed to be equivalents to the
embodiments described, and are intended to be within the scope of the invention.
T he foregoing is considered to be illustrative only of the principles of the
invention. Further, since numerous modi~lcations and changes will occur to those30 skilled in the art, it is not desired to limit the invention to the exact construction
21373`~
and operation shown and described, and, accordingly, all suitable modifications and
equivalents may be resorted to, falling within the scope of the invention.
16
