Note: Descriptions are shown in the official language in which they were submitted.
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Description
Roll
This invention relates to a roll, particularly a roll for crushing or de-
agglomerating different
materials, such as granular bulk material, pigments and the like, for example,
and also for
treating sheet-like products, according to the precharacterising clause of
claim 1.
It can be used in all situations where deformations of the roll ends, in
association with a
constant roll gap, constitute a problem in an operating situation.
Depending on their function, rolls disposed in roll mills, calenders and the
like are either
arranged parallel to each other with a defined spacing (roll gap or crushing
gap) or they are
pressed against each other practically without a gap. In this respect they
undergo both wear
and a certain deflection in operation, which results in departures from
defined operating
prerequisites. If a roll which is mounted at its ends is pressed against a
second, similarly
mounted roll, the rolls deflect. The deflection is greater in the middle than
at the mounted
ends.
A deflection such as this gives rise, in printing machinery for example, to an
unequal contact
pressure on the line of contact, which has an adverse effect on the print
result. Solutions have
been sought in order to compensate for a deflection of this type, particularly
in the
construction of printing machinery, where long, slender rolls are employed.
Apart from
comparatively simple solutions, such as the provision of elastic shell layers
(rubber), the
controlled-deflection roll is primarily employed, where roll deflections are
compensated for
in a controlled manner by means of costly constructional and control
technology
arrangements. This is primarily accomplished by hydraulic systems, wherein the
roll is a
rotating hollow roll with a stationary crosshead (see European patent
application number
91102665.6 published on October 16, 1991, under publication number 0 451 470
A2 or
European patent application number 91114596.9 published on April 29, 1992,
under
publication number 0 482 318 Al).
According to 0 451 470 A2, supporting elements arranged in rows against the
internal
periphery of the hollow roll are pressurised by means of a fluid in order thus
to maintain a
specific bending line.
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In the known NIPCO rolls a hydrostatic bearing arrangement enables deflection
to be
compensated for. The production of a hydrostatic plain bearing such as this is
very costly,
however.
In contrast, the use of electromagnets instead of hydraulic systems is
proposed in European
patent application number 80103334.1 published on January 7, 1981, under
publication
number 0 021 297. A multiplicity of electromagnets is disposed in the roll
shell, with each of
which a rotor and a sensor is associated, wherein the energisation of the
individual
electromagnets can be controlled via the associated sensors.
As another possibility, European patent application number 86309081.7
published on July 1,
1987, under publication number 0 227 302 proposes the construction of calendar
rolls as
hollow rolls, in the interiors of which an axial support is again mounted.
This axial support is
mounted both at its ends and supported against the internal periphery of the
hollow roll. In
addition, the hollow shaft is also mounted at its external periphery at its
ends.
The use of cambered rolls is also generally known, although by this means
compensation for
deflection is only possible for an adjusting force (specific pressure) which
has to be
determined beforehand by calculation. During changes which are necessary
during operation,
cambering such as this becomes inappropriate. However, for previously
calculated operating
situations it enables a uniform work of comminution to be achieved over the
entire roll width
for crushing rolls (smooth rolls).
Moreover, wear of the roll shell can be compensated for within limits by
cambering or
camber grinding. The underlying object of the present invention is now to
further develop
a roll of this type, particularly a crushing roll (smooth roll), so that on
overcoming the
disadvantages of the known prior art a non-controlled, passive compensation
for deflection
is provided in order to achieve a constant crushing gap. The aim is to achieve
a high level
of operational reliability at a cost which is technically and economically
justifiable.
This object is achieved by means of the characterising features of claim 1.
According to the invention, the roll contains a core with two-point mounting
at its ends.
Elastic elements are disposed between the core and a wear-resistant shell. The
shell is
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supported by these elastic elements. The elastic elements may either consist
of individual
spring elements known in the art (e.g. elastomeric spring elements, metal
springs and the
like) or may be constructed in the form of a continuous or discontinuous
elastic intermediate
layer. An intermediate layer such as this is softer than the material used for
the core and
shell.
The spring travel of the elastic elements must be greater than the deflection
of the roll core
When individual spring elements are used, the size of the gap between the core
and the shell
likewise depends on the extent of the deflection, wherein the gap size must be
greater than
the latter. The fixed mounting of spring elements such as this must also be
included in the
determination of the gap size, if necessary.
It is possible to use spring elements of different stiffness, which enables
deflection to be
almost eliminated.
The solution according to the invention also enables longer rolls exhibiting
low deflection to
be produced, or enables cylinder mills having longer operative rolls to be
manufactured more
economically as regards compensation for deformation/deflection. Moreover, if
the roll shell
becomes damaged it can easily be replaced.
The gap can also be used for cooling in very different forms and in the form
known in the
art. For example, if a cooling coil is employed, with introduction of the
coolant on one end
face (with the "smaller" radius) and discharge of the coolant on the other end
face, even
thermal expansions which give rise to a tapered deformation of the roll are
not deleterious
for the purpose of achieving a constant crushing gap, provided that the
departure from the
cylinder is significantly less than the deflection of the roll shell. The roll
shell merely has
to be linear.
The lower heat capacity of the roll shell proves to be favourable as regards
control
technology.
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Using the roll according to the invention, it is possible to achieve a
constant crushing gap at
different operating stages, e.g. during start-up.
Cambering, which was hitherto customary for crushing rolls (smooth rolls), can
be dispensed
with.
A roll construction such as this makes variable adjustments possible when the
loading is not
constant and also at constant, higher loading.
In fact it is also known that elastic intermediate or outer layers can be used
for the rolls of
printing machinery, but these can only be used for considerably lower forces
and pressures.
It is not possible simply to transfer solutions of this type to the smooth
rolls of the grinding
compartments of a cylinder mill, or to a pigment roll mill, for example.
The invention is described in more detail below by way of an example of an
embodiment and
with reference to a drawing. The drawing illustrates the principle of a roll
according to the
mvent~on.
A smooth roll I, of length one metre, for a cylinder mill (grinding
compartment) consists of
a core 2 in the form of a thick-walled tube made of normal cast steel. The
wall thickness
is sufficient for the machining of the bearing stubs 3. The surface is merely
turned.
Commercially available spring elements 4 made of elastomer and of identical
spring stiffness
are disposed on the surface at intervals of about 100 mm, and are seated in
guides 5 in
accordance with their material properties. The outside diameter of the spring
elements 4 is
selected so that a gap 8 of about 10 mm is produced between the core 2 and a
roll shell 6
made of chilled cast iron. This roll shell 6 is cylindrically ground on its
outside diameter
and is again merely turned inside.
Because at a limiting loading of 50 N/mm roll length the eccentricity of the
roll 1 is less than
1 mm, the gap 8 can also be reduced to just this size. The gap is sealed at
the sides, i.e. at
the end faces of the roll, with customary sealing elements 7.
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In a modified form the spring elements 4 may also be arranged in the manner of
ribs,
preferably in the form of discontinuous, prestressed longitudinal ribs which
consist of
polyurethane, for example, and which are adhesively bonded to or cast on the
core 2.
Sealing elements 7 are again disposed at the ends of the roll 1. In addition
to the
transmission of torque and its ease of manufacture, the arrangement of
discontinuous
longitudinal ribs also facilitates the optimum circulation of coolant, if
necessary.
The roll I according to the invention, which is not restricted to the
embodiment illustrated,
enables a high level of functionality to be achieved at comparatively low
manufacturing and
operating costs, and in particular enables a crushing gap which is constant
over many hours
of operation to be achieved in association with the possibility of cooling.
Its functional
advantages during the uniform comminution or size reduction of material to be
crushed are
manifested in a longer service life and/or greater variability of the
operating parameters.
Moreover, it is thus possible, in pigment roll mills for example, to employ
only one type of
roll for different coloured pigments.
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Reference Numerals
1 roll
2 core
3 bearing stub
4 spring element
guide
6 roll shell
7 sealing element
8 gap
