U.S. patent application number 13/308990 was filed with the patent office on 2012-05-17 for pre-honed doctor blade with a curved profile lamella and method for producing said doctor blade.
This patent application is currently assigned to C.B.G. Acciai S.r.l.. Invention is credited to Alberto Filippini Fantoni, Sveva Filippini Fantoni, Uberto Filippini Fantoni.
Application Number | 20120122376 13/308990 |
Document ID | / |
Family ID | 38006959 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120122376 |
Kind Code |
A1 |
Filippini Fantoni; Alberto ;
et al. |
May 17, 2012 |
PRE-HONED DOCTOR BLADE WITH A CURVED PROFILE LAMELLA AND METHOD FOR
PRODUCING SAID DOCTOR BLADE
Abstract
A method of producing a doctor blade from a band. A grinding
wheel is positioned above the band with its axis of rotation not at
right angles to the edge of the doctor blade. The grinding wheel
then is rotated and the band is moved beneath the grinding wheel
parallel to its edge.
Inventors: |
Filippini Fantoni; Alberto;
(Milano, IT) ; Filippini Fantoni; Sveva; (Milano,
IT) ; Filippini Fantoni; Uberto; (Milano,
IT) |
Assignee: |
C.B.G. Acciai S.r.l.
Caronno Pertusella (VA)
IT
|
Family ID: |
38006959 |
Appl. No.: |
13/308990 |
Filed: |
December 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11812302 |
Jun 18, 2007 |
|
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13308990 |
|
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Current U.S.
Class: |
451/45 |
Current CPC
Class: |
B41F 9/1072 20130101;
D21G 3/005 20130101; Y10T 29/49995 20150115; B41F 9/1054 20130101;
B05C 11/045 20130101 |
Class at
Publication: |
451/45 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2006 |
EP |
06 425 818.9 |
Claims
1.-9. (canceled)
10. A method for producing, starting from a band, a doctor blade,
characterised in that it comprises at least the steps of:
positioning above the band a grinding wheel with its axis of
rotation not at right angles to the edge of the doctor blade;
setting the grinding wheel in rotation; moving the band beneath the
grinding wheel parallel to its edge.
11. A method as in claim 10, characterised in that the grinding
wheel is a disk grinding wheel.
12. A method as in claim 10, characterised in that the grinding
wheel is a conical grinding wheel with its axis of rotation having
an inclination equal to the taper of the grinding wheel.
13. A method as in claim 10, characterised in that, during the
manufacturing, the axis of the grinding wheel is parallel to the
edge of the doctor blade.
14. A method as in claim 10, characterized in that, during the
manufacturing, the axis of the grinding wheel is inclined with
respect to the edge of the doctor blade by an angle (.alpha.)
comprised between 0.degree. and 85.degree..
15. A method as in claim 14, characterised in that, during the
manufacturing, the axis of the grinding wheel is inclined with
respect to the edge of the doctor blade by an angle (.alpha.)
comprised between 0.degree. and 45.degree..
16. A method as in claim 10, characterised in that, during the
manufacturing, the edge of the doctor blade is maintained on the
vertical drawn from the centre of the grinding wheel.
17. A method as in claim 10, characterised in that, during
manufacturing, the edge of the doctor blade is offset with respect
to the vertical drawn from the centre of the grinding wheel.
18. A method as in claim 17, wherein the grinding wheel is a disk
grinding wheel with a radius (r) and axis of rotation parallel to
the edge of the doctor blade, characterised in that the offset (d)
of the edge of the doctor blade with respect to the vertical drawn
from the centre of the grinding wheel is comprised between 0 and
0.05*r.
19. A method as in claim 18, characterised in that the offset (d)
of the edge of the doctor blade with respect to the vertical drawn
from the centre of the grinding wheel is d=0.03*r.
20. A method as in the claim 14 for producing a doctor blade as in
claim 9 by means of a disk grinding wheel having a thickness,
characterised in that the width (p) of the flat portion of the
lamella is: p=0.5*l*sen a if d=0; p=l*sen .alpha. if d=0.5*l.
Description
[0001] The present invention refers to a pre-honed doctor blade
with a curved profile lamella and to a method for producing said
doctor blade
[0002] Doctor blades are well-known devices normally used to detach
from a cylindrical surface with a finite (cylinder) or infinite
radius (flat surface) a product (in liquid, paste or powder form)
previously adhering to said surface. Doctor blades can therefore be
used in many sectors to clean the surface of cylinders used (for
example) for printing, to distribute and to spread glues, for
grinding, etc
[0003] In many printing methods doctor blades are used to
distribute the printing ink on a frame (as, for example, in screen
printing) or to remove the excess ink from a printing cylinder
(rotary printing, flexographic printing, etc.) or from a flat
cliche (letterpress printing, tampography).
[0004] With particular reference to the printing presses, a doctor
blade operates in direct contact with the surface of the print
cylinder to eliminate the printing ink from the unengraved parts of
said surface and the excess printing ink from the engraved parts of
said surface; both the surface of the printing cylinder and the
doctor blade are therefore subject to wear since the speed of
rotation is high. Consequently, the printing cylinders are often
coated with a layer of hard material (for example ceramic material
or hard chromium), which can differ according to specific
applications.
[0005] The doctor blades for printing presses currently in use
consist mainly of a metal support consisting in a precision steel
band, cold rolled and tempered.
[0006] In the presence of corrosion phenomena or, in general, for
applications where a high resistance to the abrasion and to the
wear is required, the metal support can consist of a stainless
martensitic steel band or of a band of low-alloy steel with various
additives.
[0007] In order to improve the resistance to wear of the doctor
blade-cylinder assembly, the metal support is often totally or
partially coated along the edge(s) with coating layers of various
types: thin metal layers (for example chrome or nickel plating),
layers of ceramic material, of polymer material, etc., deposited by
known processes.
[0008] Doctor blades consisting entirely of synthetic materials to
improve their adhesion to the surface of the cylinder and to reduce
the wear on said cylinder are also known to the art.
[0009] In all the cases described above, one or both of the
straight edges destined to come into contact with the surface of
the print cylinder has the profile considered most advantageous on
a case-by-case basis to meet specific needs.
[0010] The doctor blade-cylinder contact edge of the doctor blades
currently known to the art has one of the following profiles:
[0011] rectangular profile: full thickness doctor blade, doctor
blade-cylinder contact edge not pre-honed with 90.degree. sharp
edges sheared, de-burred or ground (FIG. 1a);
[0012] rounded profile: full thickness doctor blade, doctor
blade-cylinder contact edge not pre-honed and with radial edges
(FIG. 1b);
[0013] bevel profile: doctor blade-cylinder contact edge pre-honed
at an angle, with the thickness of the bevel increasing linearly
from the tip of said bevel to where it joins the doctor blade body;
the tip of the bevel may or may not be rounded (FIG. 1e).
[0014] lamella profile: doctor blade-cylinder contact edge
pre-honed, with a minimum change in thickness along the lamella
from the tip of said lamella to where it joins the doctor blade
body; the tip of the lamella may or may not be rounded (FIGS. 1c
and 1d).
[0015] With reference to the lamella profile, in order to obtain
the thin lamella with a constant or semi-constant thickness, the
edge thereof is thinned longitudinally with a tangential grinding
method or with the use of cup grinding wheels; since--in the known
manufacturing methods for producing a lamella profile--the axis of
rotation of the grinding wheel is substantially at right angles to
the edge of the doctor blade, the manufacturing grooves are
substantially longitudinal, that is substantially parallel to the
edge of the doctor blade.
[0016] If the grinding wheel is tangential, its axis of rotation is
at right angles to the edge of the doctor blade and parallel to the
plane of the doctor blade and the manufacturing grooves are
parallel to the edge of the doctor blade (FIG. 1c); if the grinding
wheel is a cup grinding wheel, its axis of rotation is
substantially at right angles to the edge of the doctor blade and
to the plane of the doctor blade and the processing grooves are
almost parallel to the edge of the doctor blade (FIG. 1d).
[0017] The geometry of each profile is chosen on a case-by-case
basis, in per se known manner, according to the type of process
(rotary printing, flexographic printing, tampographic printing,
spreading, etc.) and, within the same process, on the basis of the
parameters that govern said process, amongst which are: type and
hardness of the cylinder, type of engraving, speed of rotation of
the cylinder, type and density of the ink, pressure applied,
etc.
[0018] The object is to ensure the best doctoring the possible,
that is, with particular reference to the printing processes, the
best regulation possible of the amount of ink that fills the cells
of the cylinder engravings. This turns off into the search for the
best compromise between length of print run, evenness of tone for
the whole duration of the print run and absence of printing faults
such as streaks, smears etc.
[0019] The non pre-honed contact edge, which makes the doctor blade
usable from both sides without distinction, finds its main
application in flexographic printing where at the relatively
greater thickness of the blade, in combination with the
characteristics of the print process, allows a good doctoring of
the anilox cylinders; the non pre-honed doctor blade is also used
as the closing doctor blade in the inking chamber.
[0020] The pre-honed contact edge with a lamella tip has the
following advantageous characteristics:
[0021] adaptability to the cylinder: it allows an excellent
doctoring even the presence of cylinders with very high line counts
and low printing pressures;
[0022] flexibility: the reduced thickness of the lamella with
respect to the more robust blade body allows limited working
pressures even at high speeds and, consequently, leads to an
increase in the life of the blade and thus of the print run;
[0023] evenness of wear on the lamella: as a result there is a good
continuity of tone throughout the print run; and the following
unfavourable characteristics:
[0024] because of the longitudinal manufacturing grooves, during
wear on the blade long threads of the material making up the doctor
blade tend to form at the deepest grooves and at the highest
ridges; these threads can cause printing flaws or damage the doctor
blade itself, the printing ink filters or other accessory equipment
such as pumps, etc.;
[0025] because of the sudden change of thickness due to be short
join between the lamella and the doctor blade body and to the
critical nature of the manufacturing at the point of joining, the
elasticity of the doctor blade changes sharply in the joining area:
this leads to the risk of breakage and/or of permanent bending of
the doctor blade at the joining area, etc.;
[0026] the actual working angle varies greatly according to even
minimal changes in pressure because of the weakness of the lamella
at the point of joining.
[0027] The pre-honed bevel contact edge, on the other hand should
ensure a more even reaction to the pressure applied. The angled
bevels obtained with a cup grinding wheel have inclined
manufacturing groves with respect to the edge of the blade but have
a linearly increasing thickness, which compromises the evenness of
the doctoring because of the wear on the edge, with a resulting
variation in tone.
[0028] In the case of a rounded tip of the lamella or of the bevel,
the running-in time of the doctor blade is reduced to a
minimum.
[0029] A combination of a plurality of profiles is also possible:
for example, doctor blades are known to the art which have an
contact edge with the cylinder of variable thickness, with the full
thickness ends and the pre-honed central part with a lamella, with
the main purpose of reducing the wear on the doctor blade at the
edges of the cylinder during the oscillation of the blade.
[0030] By reducing the risk of breakage of the blade at the edges
of the cylinder and the consequent leakage of ink, a lengthening of
the duration of the blade and thus of the print run is obtained,
other parameters being equal.
[0031] None of the doctor blades currently in use has proved able
to satisfy fully the requirements of users. In fact, it is rather
frequent to find that the following problems persist:
[0032] fragility of the lamella or of the bevel;
[0033] rapid wear of the doctor blade-cylinder assembly in the case
of high printing pressure and/or of high speeds and/or of long
print runs.
[0034] uneven wear on the doctor blade/print cylinder assembly,
which leads to a lack of continuity of tone, to hazing, to streaks
and/or to other faults;
[0035] formation of threads of the material forming the doctor
blade due to wear on said doctor blade.
[0036] Object of the present invention is to produce a doctor blade
suitable to overcome the above drawbacks presented by the doctor
blades of the prior art; this object is achieved by means of the
doctor blade which has the characterising elements illustrated in
claim 1, produced by means of the method illustrated in claim
10.
[0037] Further advantageous characteristics of the invention form
the subject matter of the dependent claims.
[0038] Exemplifying embodiments of the invention will be described
hereunder, purely by way of non-limiting illustration, with
reference to the appended figures, in which:
[0039] FIG. 1 shows diagrammatically, in a perspective view, the
terminal area of some known types of doctor blade;
[0040] FIG. 2 shows diagrammatically a perspective view and a top
view of the terminal part of a doctor blade forming the subject
matter of the present invention;
[0041] FIG. 3 shows diagrammatically the side views of some doctor
blades forming the subject matter of the present invention;
[0042] FIG. 4 shows diagrammatically a side view and a top view of
a doctor blade during manufacturing according to a first embodiment
of the method forming the subject matter of the present
invention;
[0043] FIG. 5 shows diagrammatically a side view and a top view of
a variant of the method of FIG. 4;
[0044] FIG. 6 shows diagrammatically a side view and a top view of
a doctor blade during manufacturing according to a second
embodiment of the method forming the subject matter of the present
invention;
[0045] FIGS. 7 and 8 show diagrammatically a side view and a top
view of some variants of the method of FIG. 6;
[0046] In the appended figures like elements will be designated by
the same reference numerals.
[0047] The present invention refers to a pre-honed doctor blade
with a lamella profile, produced by means of a grinding wheel,
wherein the lamella has a curved profile and the manufacturing
grooves produced by the grinding wheel on the lamella are not
parallel to the edge of the doctor blade.
[0048] A method of producing the above-mentioned doctor
blade--starting from a band--also forms the subject matter of the
present invention and comprises at least the steps of:
[0049] positioning above the band a grinding wheel with its axis of
rotation not at right angles to the edge of the doctor blade;
[0050] setting the grinding wheel in rotation; and
[0051] causing the band to move beneath the grinding wheel parallel
to its edge.
[0052] With reference to figures from 2 to 8, the doctor
blade/print cylinder contact edge of a doctor blade 1 according to
the present invention consists of a lamella 2 with a curved profile
obtained by means of a grinding wheel 3 having its axis of rotation
not at right angles to the edge of the doctor blade 1, so that the
lamella 2 with a curved profile is obtained by removal of material
in a right-angled or in a oblique direction with respect to the
edge of the doctor blade 1.
[0053] The grinding wheel 3 can be a disk grinding wheel or a
conical grinding wheel and its axis of rotation can be parallel to
the edge of the doctor blade 1 (FIGS. 4 and 5) to produce a lamella
2 having a profile shaped as an arc of a circle, or inclined with
respect to the edge of the doctor blade 1 (FIGS. 6-8) to form a
lamella 2 having a profile shaped as an arc of an ellipse, the
initial portion of which, for the part resembling a straight line,
has a profile having an inclination between 0.degree. and
3.degree., preferably between 1.2.degree. and 2.2.degree..
[0054] If the axis of rotation of the grinding wheel 3 is parallel
to the edge of the doctor blade 1 (FIGS. 4 and 5) the doctor blade
1 has grooves 4 due to machining of the lamella 2 at right angles
with respect to the edge of the doctor blade 1 (FIGS. 2, 4 and 5)
whilst if the axis of rotation of the grinding wheel 3 is inclined
with respect to the edge of the doctor blade 1 (FIGS. 6-8) the
machining grooves 4 are inclined with respect to the edge of the
doctor blade 1 by an angle equal to the angle of inclination of the
axis of rotation of the grinding wheel 3 with respect to the edge
of said doctor blade.
[0055] The doctor blade according to the present invention, in
which the machining grooves 4 are at right angles or inclined with
respect to the edge of the doctor blade 1, advantageously has a
greater resistance to the bending and a more even wear on the
lamella: the possibility that threads of the material making up the
doctor blade, which could cause print defects, might be formed
along the doctor blade/cylinder contact edge is thus drastically
reduced (or completely eliminated).
[0056] The lamella 2 with a curved profile produced according to
the invention preferably has a width of between 1.50 and 5.00
millimetres and its honed end has a thickness between 0.055 mm and
0.120 mm.
[0057] Purely by way of example, if the doctor blade 1 has a
thickness of 0.152 mm, the lamella 2 has a width of 2.28 mm and its
honed edge has a thickness of 0.065 mm.
[0058] The above-mentioned proportions make it possible to work
with limited pressures even at high speeds and in any case with
lower pressures, other parameters being equal, compared with those
necessary with the use of a doctor blade with a pre-honed lamella
of the traditional type. Therefore, the life of the doctor blade
and consequently the duration and the continuity of the print run
are increased.
[0059] FIG. 3 shows diagrammatically the side views of four doctor
blades 1 according to the present invention, whose curved lamellas
2 are of different lengths (and therefore of different
flexibilities) to meet specific requirements of use. The different
profiles of the doctor blades 1 are obtained by choosing
appropriately the diameter, the thickness and the position of the
grinding wheel 3, as will be illustrated hereunder with reference
to FIGS. 4-8.
[0060] The thickness of the lamella 2 is advantageously almost
constant for about 1 mm starting from the honed end and then
increases quadratically along the remaining portion of the lamella
2 up to the area of joining with the body of the doctor blade
1.
[0061] Such a profile of the blade 2 has been obtained
experimentally to allow an evenness of the specific pressure
according to wear on the blade. As a result there is a good
continuity of tone throughout the print run and an almost complete
absence of hazing.
[0062] Repeated careful tests performed by the applicant have shown
that, operating conditions being equal, the consumption of a doctor
blade produced according to the invention is about 30% less than
that of the doctor blade according to the prior art having the best
performance.
[0063] The method according to the present invention to
obtain--starting from a band--a doctor blade 1 having the curved
lamella 2, will now be described with reference to FIGS. 4 to 8
which showed diagrammatically a side view and a top view of doctor
blades being produced according to some embodiments of the
aforementioned method.
[0064] In FIGS. 4 to 8 the grinding wheel 3 is a disk grinding
wheel (not described because it is per se known) having its axis of
rotation not at right angles with respect to the edge of the doctor
blade 1 but, without departing from the scope of the invention, the
grinding wheel 3 can be a conical grinding wheel whose axis of
rotation, not at right angles to the edge of the doctor blade 1,
has an inclination equal to the taper of the grinding wheel 3; a
conical grinding wheel creates a more progressive removal of
material and reduces the heating, the mechanical stresses and the
relative deformation.
[0065] The profile of the lamella 2 produced according to the
invention can be shaped as an arc of a circle or as an arc of an
ellipse, according to whether the axis of rotation of the grinding
wheel 3 is parallel to the edge of the doctor blade 1 or inclined
with respect to the edge of the doctor blade 1 by an angle between
0.degree. and 85.degree., preferably between 0.degree. and
45.degree..
[0066] In the first case the grooves are at right angles with
respect to the edge of the doctor blade 1, in the second case the
grooves are incident to the edge of the doctor blade 1 with an
angle equal to the inclination of the axis of rotation of the
grinding wheel 3 with respect to the edge of the doctor blade 1; in
both cases the advantage of avoiding the formation of threads due
to wear during use remains.
[0067] Furthermore, the profile of the blade shaped as an arc of a
circle or as an arc of an ellipse can be obtained by operating with
the edge of the band on the vertical taken from the centre of the
grinding wheel 3 (FIGS. 4 and 6) or by operating with the edge of
the band offset with respect to the vertical drawn from the centre
of the grinding wheel 3 (FIGS. 5, 7 e 8).
[0068] This offset d (FIGS. 5, 7 and 8) presents the advantage of
allowing the width of the lamella 2 and the thickness l of its edge
to be varied (the diameter of the grinding wheel 3 and, if
inclined, the thickness thereof remaining equal) without having to
replace the grinding wheel 3 or to move it vertically to bring it
nearer to or further from the doctor blade 1.
[0069] With a disk grinding wheel 3 having a thickness 1 and the
axis inclined with respect to the edge of the doctor blade 1 by an
angle .alpha. (.alpha..noteq.0), the offset d is preferably such as
to create a lamella 2 having a flat portion with the width p (not
shown in the figures for the sake of simplicity of the graphic
representation) comprised between 0 mm and 1.5 mm.
[0070] The width p of the flat portion varies from a minimum of
0.5*l*sen .alpha. (for d=0) to a maximum of l*seen .alpha. (for
d=p/2, when the whole thickness l of the grinding wheel is
exploited)
[0071] With a disk grinding wheel 3 with a radius r and axis
parallel to the edge of the doctor blade 1 (.alpha.=0), the flat
portion has a width p=0, irrespective of the offset d, which is
comprised between 0 and 0.05*r, preferably 0.03*r.
[0072] With a disk grinding wheel 3 with its axis inclined with
respect to the edge of the doctor blade 1, other conditions being
equal,
[0073] a greater offset d means that the portion of the profile of
the lamella 2 assimilable to a rectilinear portion is longer, as
can be seen by comparing the blades 2 shown in FIGS. 6 and 7;
[0074] using a grinding wheel 3 with a greater thickness it is
possible to obtain a wider lamella 2, as can be seen by comparing
the blades 2 shown in FIGS. 7 and 8.
[0075] The use of a disk grinding wheel with a larger or smaller
diameter makes it possible to obtain profiles nearer to that
theoretically desired for each specific application related to a
higher or lower printing speed, density and/or type of think,
greater or lesser density of engraving etc.
[0076] A person skilled in the art can make to the doctor blade and
to the manufacturing method previously described all the
modifications and the improvements suggested by the normal
experience and/or by the natural evolution of the art without
departing from the scope of the invention.
* * * * *