U.S. patent application number 11/789847 was filed with the patent office on 2007-10-25 for roll mill.
Invention is credited to Walter Almer, Heinz Resch.
Application Number | 20070245793 11/789847 |
Document ID | / |
Family ID | 35079468 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070245793 |
Kind Code |
A1 |
Resch; Heinz ; et
al. |
October 25, 2007 |
Roll mill
Abstract
A roll mill for comminuting and homogenizing viscous masses, in
particular for dispersing and uniformly distributing solid
particles suspended in a binding agent. The roll mill has at least
two rolls pivoted around their longitudinal axes, wherein the
rotational axis of the first roll is fixed in place, and the
rotational axis of a second roll is movably mounted, as well as at
least one pressing device for pressing at least one roll against
the other roll. Roll pressing takes place by way of a
mechanical-pneumatic pressing device, which has a force transducer
and a pneumatic drive. The roll surfaces or process surfaces are
made out of a metal-free ceramic material.
Inventors: |
Resch; Heinz; (Flawil,
CH) ; Almer; Walter; (Oberuzwil, CH) |
Correspondence
Address: |
Klaus P. Stoffel;Wolff & Samson
One Boland Drive
West Orange
NJ
07052
US
|
Family ID: |
35079468 |
Appl. No.: |
11/789847 |
Filed: |
April 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CH05/00539 |
Sep 12, 2005 |
|
|
|
11789847 |
Apr 26, 2007 |
|
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Current U.S.
Class: |
72/241.6 |
Current CPC
Class: |
B02C 4/44 20130101; B02C
4/40 20130101; B02C 4/32 20130101; B02C 4/04 20130101 |
Class at
Publication: |
072/241.6 |
International
Class: |
B21B 29/00 20060101
B21B029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2004 |
DE |
102004052084.4 |
Claims
1. A roll mill for comminuting and homogenizing viscous masses,
comprising: at least two pivoted around their longitudinal axes,
wherein the rotational axis of a first roll is fixed in place, and
the rotational axis of a second roll is movable; and at least one
pressing device for pressing at least one roll against the other
roll, wherein the pressing device is a mechanical-pneumatic
pressing device, the rolls having surfaces made out of a metal-free
ceramic material.
2. The roll mill according to claim 1, wherein the pressing device
has a force transducer that acts on a moving journal bearing of the
movable roll, and a pneumatic drive that acts on the force
transducer.
3. The roll mill according to claim 2, wherein the pressing device
acting on the movable roll has a first force transducer that acts
on a first movable journal bearing of the movable roll, and a first
pneumatic drive that acts on the first force transducer, as well as
a second force transducer that acts on a second movable journal
bearing of the movable roll, and a second pneumatic drive that acts
on the second force transducer.
4. The roll mill according to claim 2, wherein the force transducer
acts on a forked device with two forked ends, wherein a first of
the forked ends acts on a first movable journal bearing of the
movable roll, and a second forked ends acts on a second movable
journal bearing of the movable roll.
5. The roll mill according to claims 2, wherein the force
transducer is a lever arrangement.
6. The roll mill according to claim 5, wherein the lever
arrangement is a toggle mechanism or a cam plate.
7. The roll mill according to claim 1, wherein the mill is a
three-roll mill with three parallel, adjacent rolls including a
front roll, a back roll and a middle roll, wherein a rotational
axis of the middle roll is fixed in place, while a rotational axis
of the front roll used to supply a product and a rotational axis of
the back roll used for product removal are movable, and further
comprising a front mechanical-pneumatic pressing device for
pressing the front roll against the middle roll, and a rear
mechanical-pneumatic pressing device for pressing the back roll
against the middle roll.
8. The roll mill according to claim 7, wherein the front roll has
two journal bearings the front roll being pressed against the
middle roll by the two journal bearings, and the back roll has two
journal bearings, the back roll being pressed against the middle
roll by the two journal bearings.
9. The roll mill according to claim 1, wherein the mill is a
three-roll mill, and the rolls are arranged in the form of an L
viewed from the side.
10. The roll mill according to claim 1, wherein the rolls have a
ceramic cylinder fit onto a hollow metal cylinder.
11. The roll mill according to claim 1, wherein the rolls are
internally cooled.
12. The roll mill according to claim 1, wherein the
mechanical-pneumatic pressing device has a controller for setting
the nip.
Description
[0001] This application is a continuation of International
Application No. PCT/CH2005/000539, filed Sep. 12, 2005, which
claims priority from German application 10 2004 052 084.4 filed
Oct. 26, 2004, the entire disclosures of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a roll mill, in particular to a
three-roll mill, for comminuting and homogenizing viscous masses,
in particular for dispersing and uniformly distributing solid
particles suspended in a binding agent. Such a roll mill has at
least two rolls pivoted around their longitudinal axes, wherein the
rotational axis of the first roll is fixed in place, and the
rotational axis of a second roll is movably mounted. At least one
roll is pressed against the other by means of at least one pressing
device.
[0003] Known devices for roll pressing include spindle drives or
hydraulic pressing devices. A roll mill with a hydraulic roll
pressing device is known from EP 0 151 997 B1.
[0004] Spindle drives represent a costly and voluminous type of
roll pressing device, in particular those intended to be automatic,
and not manual.
[0005] While hydraulic drives to constitute a relatively compact
type of roll pressing device, operation is repeatedly accompanied
by hygiene problems caused by exiting hydraulic fluid. This poses a
problem in particular during the processing of pastes for cosmetic,
pharmaceutical or nutraceutical applications, or the processing of
pasty materials under clean room conditions.
SUMMARY OF THE INVENTION
[0006] The object of the invention is to provide a roll mill of the
basic design mentioned at the outset that enables improved product
quality, while averting the disadvantages of roll pressing via
spindle drives or hydraulic drives on the one hand, and avoiding
any metallic contamination of the product during its comminution on
the other.
[0007] This object is achieved in the roll mill of the present
invention by using a mechanical-pneumatic pressing device as the
pressing device, which represents a cost-effective solution that
satisfies hygiene requirements, and by forming the roll surfaces or
processing surfaces out of a metal-free ceramic material.
[0008] According to the invention, the roll surfaces or processing
surfaces are made out of a metal-free ceramic material, wherein the
rolls preferably have a ceramic cylinder fit onto a hollow metal
cylinder. This prevents the product from becoming metallically
contaminated by roll abrasion in the comminuting process. This is
particularly important while processing pastes for applications in
electronics, and for the manufacture of insulating bodies based on
fine ceramics.
[0009] The mechanical-pneumatic pressing device preferably has a
force transducer that acts on a moving journal bearing of the
movable roll(s), and a pneumatic drive that acts on the force
transducer. This combination of pneumatic drive and force
transducer is particularly cost-effective. The force transducer
intensifies the actuating power generated by the pneumatic drive.
In this way, the high pressures necessary for roll pressing can be
applied by the pneumatic drive without any problem. At the same
time, the force transducer reduces the path traversed by the
pneumatic drive, so that a much small distance is covered during
roll pressing than for the pneumatic drive. This makes it possible
to achieve a level of accuracy during nip adjustment that is far
greater than a level of accuracy prescribed for the pneumatic
drive. Obtained as a result is a high positioning accuracy of the
movable roll(s) using relatively cost-effective means.
[0010] The pressing device acting on the movable roll best has a
first force transducer that acts on a first movable journal bearing
of the moving roll, and a first pneumatic drive that acts on the
first force transducer, as well as a second force transducer that
acts on a second movable journal bearing of the moving roll, and a
second pneumatic drive that acts on the second force transducer. As
a result, the at least one moving roll can be pressed at both of
its end points. This makes it easier to correct roll pressing given
an unsymmetrical roll wear.
[0011] As an alternative, the pressing device can have a force
transducer and a pneumatic drive that acts on the transducer,
wherein the force transducer acts on a forked device with two
forked ends, wherein the first forked end acts on a first movable
journal bearing of the moving roll, and the second forked end acts
no a second movable journal bearing of the moving roll.
[0012] This makes it possible to press the at least one moving roll
using only a single pressing device for this roll.
[0013] Possible force transducers include a lever arrangement, in
particular a toggle mechanism or cam plate, as well as combinations
of levers and cam plates. As an alternative, use can also be made
of purely pneumatic force transducers, e.g., having a large piston
and a small piston, which interact, or a gearbox can be used as the
force transducer.
[0014] In a particularly advantageous embodiment of this invention,
the roll mill according to the invention is a so-called "three-roll
mill" with three parallel rolls. The rotational axis of the middle
roll is here fixed in place, while the rotational axis of the front
roll or feeder roll and the rotational axis of the back roll or
transfer roll are movable. To this end, it has a front
mechanical-pneumatic pressing device for pressing the front roll
against the middle roll, as well as a rear mechanical-pneumatic
pressing device for pressing the back roll against the middle roll.
This provides for two roll nips. In this way, the operating
conditions for both roll nips can be independently adjusted by
setting the nip distance, the differential velocity and the
pressure in the respective nip.
[0015] The rolls are best cooled from the inside. For example, this
is important while processing organic pigments, in particular with
respect to certain yellow pigments.
[0016] Both the front roll and the back roll are pressed against
the middle roll by means of a mechanical-pneumatic pressing device.
This makes it possible to adjust the front and back roll nip. The
mechanical-pneumatic pressing device preferably has a control means
for setting the nip. Since the force transducer, as explained
above, enables a "force transmission" and "path reduction", the
relatively weak force of a pneumatic device can be multiplied for
purposes of roll pressing, while at the same time greatly
increasing the accuracy of nip adjustment prescribed by the
pneumatic device.
[0017] The transfer roll is best abutted by a stripper that strips
away the comminuted, homogenized mass, wherein the stripper also
preferably consists of a metal-free material, in particular of a
ceramic material or polymer material. This also prevents the
product from becoming metallically contaminated in any way as the
result of stripper abrasion while being stripped from the transfer
roll.
[0018] A tarpaulin preferably covers at least the feed area of the
roll mill. This prevents undesired contaminants from the factory
building from getting into the product and vice versa, i.e.,
undesired volatile product constituents form getting into the air
of the factory building. This improves "product hygiene" on the one
hand, and "workplace hygiene" on the other.
[0019] The space under the tarpaulin is preferably connected with a
gas vent. This makes it possible to keep volatile substances
contained in the product solvent from getting into the air of a
factory building.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Additional advantages, features and possible applications of
the invention may be gleaned from the following description of
exemplary embodiments of the invention, which are not to be
regarded as limiting in any way, wherein:
[0021] FIG. 1 shows a diagrammatic side view of a first exemplary
embodiment of the roll mill according to the invention;
[0022] FIG. 2 shows a top view of the rolls in the first exemplary
embodiment on FIG. 1;
[0023] FIG. 3 shows a diagrammatic side view of a second exemplary
embodiment corresponding to FIG. 1, and
[0024] FIG. 4 shows a top view of the rolls of the second exemplary
embodiment on FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0025] In both the first and second exemplary embodiment, the roll
surfaces or roll processing surfaces S1, S2, S3 or S1', S2', S3'
are made out of ceramic material. The stripper 9 shown on FIG. 3
can also consist of ceramic material or polymer material. These or
other metal-free materials for the roll processing surfaces and the
stripper knife are of particular interest for processing pastes in
the electronics industry.
[0026] The ceramic rolls are rounded at the end of the roll
processing length.
[0027] FIG. 1 and FIG. 2 show a first exemplary embodiment of the
roll mill according to the invention. The three-roll mill shown
here contains three rolls 1, 2, 3, which are aligned parallel to
each other, and all arranged in a single plane E. In other words,
the rotational axis A1 of the front roll 1, the rotational axis A2
of the middle roll 2, and the rotational axis A3 of the back roll 3
are parallel to each other (see FIG. 2), and all lie in one and the
same plane E. In the operating mode, the front roll 1 and the back
roll 3 are each pressed by a front pressing device 4 or a back
pressing device 5 against the middle roll 2, the rotational axis A2
of which is fixed in place. The front roll 1 and back roll 3 are
movable, i.e., their rotational axes A1 and A3 can be pivoted
around a swiveling axis D3. The jacket surfaces of rolls 1, 2, 3
each comprise the roll processing surface S1, S2, S3, with which
the product to be processed comes into contact. During operation,
the product passing between the rolls 1 and 2 pressed against each
other creates a roll nip between the processing surface S1 of the
front roll 1 and the processing surface S2 of the middle roll 2. In
like manner, the product passing between the rollers 2 and 3
pressed against each other creates a roll nip during operation
between the processing surface S3 of the back roll 3 and the
processing surface S2 of the middle roll.
[0028] The front pressing device 4 and back pressing device 5 each
have a force transducer 6 and a pneumatic drive 7. In the first
exemplary embodiment shown on FIG. 1, the force transducer is a
toggle mechanism 6, which consists of a first lever 6A and a second
lever 6B, while the pneumatic drive 7 consists of a pneumatic
cylinder 7A and a pneumatic piston. The force exerted by the
pressing devices 4 and 5 flows from the pneumatic piston 7B, which
is accommodated in the pneumatic cylinder 7A, and linked with the
first lever 6A on an articulated axis D1 by means of a piston rod
7B. The first lever 6A is hinged to a second articulated axis D2 on
the second lever 6B, which in turn is hinged to a pivoting axis D3,
and forms a respective suspension and mounting arrangement for the
front roll 1 and back roll 3.
[0029] Depending on how the levers 6A and 6B are dimensioned and
oriented, the toggle mechanism 6A, 6B used as the force transducer
6 and roll suspension unit increase the pneumatic force of the
pneumatic drive 7 by a factor of about 20 to 50, wherein this
increased force is used for purposes of roll pressing. This enables
a sufficiently strong roll pressing, even with a pneumatic drive 7.
On the other hand, this force transducer 6 decreases the stroke
traversed by the pneumatic drive 7 by a factor of about 1/50 to
1/20, wherein this reduced stroke is used to set the nip.
[0030] Rolls 1, 2 and 3 are driven by overdrives or gearboxes by
engine M. The roll block 1, 2, 3 and engine block M are enveloped
by a casing G.
[0031] FIG. 2 shows a top view of the rolls 1, 2, 3 of the first
exemplary embodiment of the roll mill according to the invention
shown on FIG. 1. As evident, the front roll or feeder roll 1 and
the middle roll 2 both have the same processing length L1=L2, while
the back roll or transfer roll 3 has a distinctly shorter
processing length L3<L2 to avoid undefined edge effects. The
back roll 3 is axially arranged relative to the middle roll 2 in
such a way that the ends of the processing length L2 of the middle
roll 2 extend axially over the ends of the process length L3 of the
back roll 3 on both sides. This ensures that unabraded or only
inadequately abraded product does not pass from the middle roll 2
to the back roll 3 during roll mill operation, making it possible
to achieve a distinctly improved product quality.
[0032] FIG. 3 and FIG. 4 show a second exemplary embodiment of the
roll mill according to the invention.
[0033] All elements of the second exemplary embodiment shown on
FIG. 3 and FIG. 4 that are identical to the elements of the first
exemplary embodiment shown on FIG. 1 and FIG. 2 or correspond
thereto bear the reference numbers of the corresponding element
from FIG. 1 or FIG. 2 with a quote mark added. How these elements
of the second exemplary embodiment work will not be explained again
here. In addition the front pressing device 4' and the back
pressing device 5' with their respective force transducer 6' and
pneumatic drive 7' are shown only diagrammatically.
[0034] The other reference numbers on FIG. 3 and FIG. 4 that show
elements of the second exemplary embodiment that deviate from the
first exemplary embodiment do not bear the quote mark. Their
function and importance will be explained below.
[0035] The essential difference between the first exemplary
embodiment (FIG. 1 and FIG. 2) and the second exemplary embodiment
(FIG. 3 and FIG. 4) is that the three-roll mill depicted here has
three rolls 1', 2', 3' which, while aligned parallel to each other,
are not all arranged in the same plane. Rather, the rotational axis
A1' of the front roll 1' and the rotational axis A2' of the middle
roll 2' are arranged in a first plane E1, while the rotational axis
A3' of the back roll 3' and the rotational axis A2' of the middle
roll 2' are arranged in a second plane E2 that forms an angle
.gamma. of about 45.degree. relative to the first plane E1. As a
result of arranging the three rolls 1', 2', 3' in this way, the
product present as a viscous mass with the solid particles (e.g.,
pigments) distributed therein can be cooled for a longer period of
time, and hence more intensively, than in an arrangement in which
the rotational axes of the front, middle and back roll lie in a
single plane.
[0036] FIG. 4 is a top view of the rolls 1', 2', 3' of the second
embodiment of the roll mill according to the invention shown on
FIG. 3. Here as well, the front roll or feeder roll 1' and middle
roll 2' both have the same processing length L1'=L2', while the
back roll or transfer roll 3' has a distinctly shorter processing
length L3'<L2'. The back roll 3' is also axially arranged
relative to the middle roll 2' in such a way that the ends of the
processing length L2' of the middle roll 2' extend axially over the
ends of the processing length L3' of the back wall 3' on both
sides. As already explained, this ensures that no unabraded or only
inadequately abraded product gets from the middle roll 2' to the
back roll 3' during operation of the three-roll mill, thereby
improving product quality.
[0037] The path traversed by the product as it passes through the
roll mill according to the second exemplary embodiment is increased
by the two additional circular arc lengths at the surfaces S2' and
S3' of the roll 2' and 3' with radius R that arise between plane E1
and plane E2 as the result of angle .gamma., i.e., an additional
path relative to the first exemplary embodiment (FIG. 1) by
2.times..gamma..times.R.
[0038] A transfer funnel or product trough 8 with stacking wedges
extending from the introduction region on either side is arranged
over the area of the introduction nip between the front roll 1' and
the middle roll 2'. As the result of the stacking wedges provided
in addition to the conventional wedge gaskets, this product trough
increases tightness, thereby ensuring a lower lateral product
loss.
[0039] A stripper 9 with a stripping knife is used for removing the
product from the back roll 3'. The stripper 9 is equipped with an
automatic knife adjustment, which is actuated from an SPS
controller.
[0040] The pneumatic drive 7 operates at pressures of up to 4 bar,
for example, which are brought to bear via the force transducers 6
on the required line pressures in the roll nips. The force
transducer 6 make sit possible to increase the pressing force
exerted on the rolls by the roll pressing devices 4, 5 by a factor
of about 10 to about 80. Accordingly, the reduction in the stroke
prescribed by the pneumatic drive 7 via the force transducer
increase the nip setting accuracy by the same factor.
[0041] The rolls have a diameter of 300 mm, and the back roll 3, 3'
is about 4 mm to 5 mm shorter than the middle roll 2, 2'. As a
result, the stripper 9 only strips abraded product from the back
roll 3'.
[0042] Although the present invention has been described in
relation to particular embodiments thereof, many other variations
and modifications and other uses will become apparent to those
skilled in the art. It is preferred, therefore, that the present
invention be limited but by the specific disclosure herein, but
only by the appended claims.
* * * * *