Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1
Hudrostatic Aide bearing for a roll or equivalent
The invention relates to a glide bearing for a roll, which glide bearing
comprises
several hydrostatic bearing elements which are provided with bearing shoes
fitted to
be positioned around the neck of a roll axle in order to support said axle
and, thus.
the roll revolvingly with respect to a frame member, such as a bearing block.
Until now, rolls in paper machines and in paper finishing devices. except for
rolls
in which the mantle of the roll is able to move with respect to the axle of
the roll.
have ordinarily been journalled by means of roller bearings on frame
structures of
the machine. In particular, in connection with rolls forming a nip, such as
calender
rolls and soft calender rolls, such roller bearings have caused certain
problems.
whose solution has required special arrangements. In some cases, it would be
desirable to operate soft calenders in particular at linear loads that produce
a very
small load, even the so-called zero load on roller bearings. This is very
problematic
in the case of roller bearings because, in the zero load situation, the
rolling members
of the roller bearing are able to glide considerably with respect to bearing
races
instead of rolling, with the result that the bearing breaks rather quickly.
Heatable
rolls, calender rolls in particular, also involve the problem that succeeding
in
lubrication is a fairly critical factor. In connection with roller bearings,
it has been
necessary also for this reason to employ special arrangements. Roller bearings
additionally involve a vibration problem. The roller bearings in themselves do
not
have any property that in itself could attenuate such vibration. The structure
of the
bearing alone sets a certain limit for the speed of rotation, which limit is
not
permitted by the bearing manufacturer to be exceeded. As already previously
mentioned, the rolling accuracy of the bearing is limited. Although all the
compo-
nents in a conventional roll were manufactured as precisely as possible, the
defects
caused by inaccuracies are summed up in an assembled roll.
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Presses also make special demands on journalling of rolls. From the point of
view
of journalling, extended-nip presses in particular are troublesome because the
radial
forces acting on bearings in this kind of construction are very high. Special
problems
of their own are also caused by centre rolls of a press section for the reason
that the
centre roll generally forms two nips with backup rolls such that the
directions of nip
planes differ substantially from each other. In that case, it is difficult to
determine
any actual principal loading direction.
With regard to prior art relating to the journalling with glide bearings,
reference is
made, for instance, to EP Patent 158 OSl which relates to the .journalling of
a
washing drum. The journalling in this arran~cment has heen provided with elide
bearings by means of hydrostatic bearing segments. The mode ~f journallin; in
accordance with this publication cannot. however. be used. for instance, in
calender
rolls that are in nip contact, because the mode of journalling described in
this EP
publication does not comprise any possibility of radial movement in the
hearing
itself. Also> the loading of the bearing cannot be chanced in any way, and
separate
spring elements are needed for attenuating vibrations. With respect to prior
art.
reference is made further to FI Patent Application No. 942756 which discloses
a
bearing for a heated roll. This mode of journalling also involves the drawback
that
there exists no possibility of radial displacement, because at least one
hydrostatic
bearing segment of the glide bearing arrangement is, in the radial direction,
com-
pletely fixed and stationary with respect to a frame structure, and, thus, it
is not
possible to displace the roll carried by means of said bearing, for instance,
in the
direction of the nip plane.
The present invention is concerned with the provision of a novel arrangement
for a
roll or equivalent for journalling it with glide bearings, by means of which
the
drawbacks involved in the journalling with roller bearings are avoided, and
which
additionally provides a significant improvement over the already existing
arrangements for journalling by means of glide bearings.
In accordance with one aspect of the present invention, there is provided a
roll in a
paper machine or in a paper finishing device the roll being mounted
revolvingly in a
frame member and having a roll axle which roll forms a roll nip and a nip
plane with
at least one backup roll whereby the roll is provided with glide bearings
comprising a
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plurality of hydrostatic bearing elements provided with bearing shoes
positioned
around a neck of the roll axle for supporting the axle and thus the roll
revolvingly
with respect to the frame member whereby the bearing elements are
hydraulically
operating piston-cylinder devices loadable by means of a pressure medium so
that
each of the bearing shoes of the bearing elements is able to be positioned
freely
around the neck of the axle, wherein the bearing elements constituting a main
bearing
of the roll comprise a plurality of bearing elements placed around a periphery
of the
axle, the resultant of the forces produced by the bearing elements being
opposite in
direction to the resultant of the force directed to the bearings from the roll
nip in the
10 direction of the nip plane and of the force directed to the bearings from
the weight of
the roll.
The invention provides a significant advantage over prior art arrangements,
and of
these advantages, among other things, the following may be mentioned. The
journalling system is not directly in contact with a frame in the principal
loading
15 direction, in the direction of the nip plane in particular, but it can be
loaded hydrau-
lically by means of the device of the piston-cylinder type towards the axle.
This
enables the roll to he displaced and moved in said principal loading
direction.
Further, in the case of nip rolls, it enables the nip load to hr regulated
accurately
and the nip load to be measured without special arrangements. The hvdroscatic
20 bearing shoes included in the journalling system arc posittc,nrd t~tallv
freely around
the neeh of the roll axle, so that e... increase in the diameter of the arlr
caused by
heating up of the axle does not create any prohlem, nee dons the inclination
rcsultine
from bending of the axle nor do other faults in position. The j~urnalline
system may
be used intentionally, for instance, for closing and opening a roll nip
because all
25 hydrostatic bearing shoes are movable. The nip load can be calculated
directly from
the oil pressures of the bearing shoes because said shoes provide loading of
the roll
nip. The journalling arrangement is in itself receiving and attenuating
vibrations. The
further advantages and characteristic features of the invention will become
apparent
from the following detailed description of the invention.
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3a
In the following, the invention will be described by way of example with
reference
to the figures in the accompanying drawing.
Figure 1 is a schematic and partly sectional side view of a glide bearing on
one side
of a roll.
Figure 2 schematically shows the application of the glide bearing shown in
Fig. 1 to
journalling of a centre roll of a press.
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Figure 3 shows, in a way corresponding to that of Fig. 2, a glide bearing
modified
from the illustration of Fig. 1 as a bearing of a centre roll of a press.
Figure 4 shows the application of a glide bearing to journalling of a centre
roll of a .
press in which one backup roll of the centxe roll is an extended-nip roll.
Fig. 1 of the drawing thus shows fully schematically one embodiment of the
glide
bearing in accordance with the invention as applied to supporting of a roll,
which
roll forms a nip with a backup roll. The roll itself has been illustrated with
a line of
dots and dashes and denoted with the reference numeral 1. and the axle of the
roll
is denoted with the reference numeral 3. The reference numeral 2 denotes the
backup roll which forms a nip N with the roll 1, which nip is, for instance, a
calendering nip. The nip plane is denoted by the reference sign A-A. Although
it
is not separately shown in Fig. 1, it shall be understood that, in the
journalling of
the roll 1, the journalling of at least one end of the roll must comprise an
axial
bearing receiving axial loads because the glide bearing arrangement in
accordance
with the invention is intended to serve mainly merely as a radial bearing of
the roll.
The glide bearing arrangement in accordance with the invention shown in Fig. 1
comprises bearing elements 10,20,30,40 which are mounted in a bearing block 4
and
which rest against the axle 3 of the roll. The journalling arrangement
comprises a
main bearing 10,30 which acts in the main loading direction, i.e. in the
direction of
the nip plane A-A, and which is loaded towards the nip N, a counter-bearing 20
acting in an opposite direction, and side bearings 40 acting in opposite
directions in
a direction transverse to the nip plane A-A. In the embodiment shown in Fig.
1,
the main bearing is divided into three parts such that it comprises a first
bearing
element 10 acting in the nip plane and, in addition to this, second bearing
elements
arranged at an angle and situated symmetrically with respect to the nip plane.
The arrangement of the bearing elements on the axle of the roll and, for
instance,
30 the "symmetricalness" of the elements may, however, even substantially
differ from
the illustration of Fig. 1 according to each particular application, as shown,
for
instance, hereafter in connection with Figs. 2-4. The arrangement of the
bearing
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elements shown in Fig. 1 is only one embodiment which is primarily intended
for a
construction in which the roll 1 provided with said bearings each time forms
only
one nip with the backup roll. This is the case, for instance, in a soft
calender
comprising two rolls. However, it is not desired to exclude the possibility
that this
5 kind of journalling is also employed in another connection, as is attempted
to be
illustrated, for instance, by means of Fig. 2.
In the illustration of Fig. 1, the first bearing element 10 and the second
bearing
elements 30 may be in structure similar to one another such that they comprise
a
cylinder 11,31 fitted in the bearing block 4, a loading piston 13,33 being
movably
disposed in said cylinder. A pressure space 12,32 is formed in the cylinder
11,31
under the loading piston 13,33, and by passing a pressure medium into said
pressure
space, the loading piston 13.33 is caused to be loaded towards the axle 3. A
bearing
shoe 16,36 is attached to that end of the loading piston 13.33 which is on the
side of
the axle 3, and lubricating oil pockets 15,35 opening cowards the axle 3 are
formed
in said bearing shoe. The loading piston 13,33 is provided with capillary
through
bores 14,34, which thus connect the pressure space 12,32 of the cylinder with
the
lubricating oil pockets 15,35 of the bearing shoe. The pressure medium is thus
able
to enter the lubricating oil pockets 15,35 through the capillary bores 14,34
so that an
oil film is formed between the bearing shoe 16,36 and the axle 3, the bearing
shoe
16,36 being supported against the axle 3 through said oil film.
The counter-bearing 20 is in structure similar to the bearing elements 10, 30
of the
main bearing such that the counter-bearing element 20 comprises a cylinder 21
fitted
in the bearing block 4 and a loading piston 23 movably disposed in the
cylinder. The
loading piston 23 further comprises a bearing shoe 26 which is provided with
lubricating oil pockets 25. The bearing shoe 26 is provided with capillary
bores 24,
along which oil from a pressure space 22 situated under the loading piston 23
can
enter lubricating oil pockets 25 to form an oil film between the bearing shoe
26 and
the neck of the axle 3. As shown in Fig. 1, the counter-bearing element 20 is
mounted in the nip plane A-A such that its direction of action is parallel to
the nip
plane but opposite to the direction of action of the main bearing.
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Fig. 1 further shows that the axle 3 is supported by means of bearings acting
in a
direction transverse to the nip plane A-A, i. e. by means of side bearings 40.
In the
illustration of the figure, the side bearings 40 comprise a frame part 42
fitted in the
bearing block 4 and a bearing shoe 41 disposed on support of the frame part.
The
bearing shoes 41 are loaded by means of hydraulic fluid against the axle 3 of
the
roll. The actual purpose of the side bearings 40 is only to maintain the axle
3 in its
proper position and to attenuate vibrations in a transverse direction.
In the arrangement shown in Fig. I in accordance with the invention, the
loading of
the roll nip N is produced by means of the bearing elements 10,30 of the main
bearing. Owing to this, the nip load can be calculated directly from the oil
pressures
of the bearing elements 10.30. Thus, precise regulation of the nip load can be
accomplished by fairly simple steps in the arrangement in accordance with the
invention. In the arrangement shown in Fig. 1, the main bearing is divided
into three
separate bearing elements 10,30, because of which the bearing can provide,
when
needed, fairly high loading forces. In present-day soft calenders, in many
cases, it
must be possible to apply in linear load a range that corresponds to the zero
load of
the bearing. It is rather difficult to accomplish this by means of
conventional
journalling arrangements so that the bearings would not break. In the
arrangement
in accordance with the invention and shown in Fig. 1, the zero load situation
does
not pose any problem, since the adjustment of loading to the zero loading
situation
is easy to accomplish and to provide by means of the main bearing 10,30 and
the
counter-bearing element 20. As already previously stated, in the principal
loading
direction, i.e. in the direction of the nip plane A-A, the bearing elements
10,20,30
are not fixedly secured with respect to the bearing block 4, but each of the
bearing
elements is movable. Because of this, vibrations can be effectively
attenuated.
Further, because of this characteristic feature and especially as the play of
the
hearing elements is dimensioned to be sufficiently large, opening and closing
of the
nip N may be taken care of by means of the bearing elements. For example, in
connection with soft calenders, the bearing element may then also be used for
quick-
opening of the set of rolls.
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The glide bearing arrangement shown in Fig. 1 is also suitable for use in
rolls that
are loaded from outside by two nips which have a common nip plane, i.e. in
which
the nips are in the same plane. Such applications are in certain types of
calenders
and presses. In that case there may be several rolls in a common nip plane
(e.g.
supercalenders, and machine and soft calenders comprising many nips). If such
an
arrangement were desired to be illustrated by means of Fig. 1, it might be
done most
simply by adding a second nip roll underneath the roll 1, the nip formed by
said nip
roll with the roll 1 being in the same nip plane with the nip N between the
backup
roll 2 and the roll 1.
Fig. 2 schematically shows the application of a glide bearing arrangement to a
centre
roll of a press, which roll is denoted with the reference numeral 1 in Fig. '.
The
centre roll 1 forms press nips N 1,N2 (two nips) with backup rolls 2 and 5
such that
said nips Nl.N2 are not situated in a common nip plane, but nip planes B-B and
C-C form an angle with each other. Consequently, the centre roll 1 and thus
its
bearings are subjected to substantial loads in two different directions, with
the result
that there exists no actual principal loading direction for the roll. If it
were desirable
to determine the principal loading direction of the centre roll 1 and of its
bearings in
particular, as the principal loading direction could be regarded the direction
which
consists of the direction of a resultant force of the forces acting in the
direction of
the nip planes B-B and C-C and of the load caused by the weight of the centre
roll
1 itself. In that case, the bearing elements 10,20,30,40 have to be grouped so
that
they receive the applied loads in the best possible way. In the arrangement of
Fig.
2, the grouping of the bearing elements corresponds to that described in more
detail
in Fig. 1, however, differing from it such that the main bearing elements
10,30 and
the counter-bearing elements 20 do not act in the direction of either of the
nip planes
B-B, C-C nor in the direction of the vertical plane, but, instead, the bearing
element 10,20,30,40 groups are placed' around the neck of the axle 3 in a
position
required by the "imaginary principal loading direction".
The arrangement shown in Fig. 3 corresponds to the application of the glide
bearing
arrangement shown in Fig. 2 to a centre roll of a press, which roll is denoted
with
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the reference numeral 1 in Fig. 3 too. The centre roll 1 forms press nips
N1,N2
(two nips) with backup rolls 2 and 5 so that said nips N1,N2 are not situated
in a
common nip plane, but nip planes B-B and C-C form an angle with each other.
Consequently, the centre roll 1 and thus its bearings are subjected to
substantial
loads in two different directions, with the result that there exists no actual
principal
loading direction for the roll in the arrangement of Fig. 3, either. However,
the
grouping of the glide bearing elements 10,20,30,40 differs from that of Fig.
2,
firstly, so that the so-called counter-bearing element 20 does not act in a
direction
opposite to the imaginary resultant force of the "main bearing elements"
10,30, and,
secondly, so that the groups of the bearing elements are placed around the
neck of
the axle 3 in a position different from that of Fig. 2. 1n Fig. 3, the
"counter-bearing
element" 20 is arranged almost in the nip plane B-B of the first nip N 1, and
thus
said counter-bearing element 20 substantially receives the forces directed to
the
centre roll 1 in the direction of the first nip plane B-B. The "main bearing
elements" 10,30 are in turn arranged so that they receive the load caused by
the
weight of the centre roll 1 itself as well as the load directed to the
bearings through
the second nip N2 in the direction of the second nip plane C-C. The most
appropri-
ate grouping of the bearing elements 10,20,30,40 depends, as already
previously
stated, on the forces acting on the bearings of the centre roll 1 in the
directions of
the nip planes B-B, C-C and on the effect of the weight of the centre roll 1
itself.
Finally, Fig. 4 shows, in a way corresponding to Figs. 2 and 3, the
application of
a glide bearing arrangement to journalling of a centre roll 1 of a press,
however,
differing from said figures in such a way that, in the illustration of Fig. 4,
the first
nip N1 is formed between the centre roll 1 and a first backup roll 2 in a way
corresponding to Figs. 2 and 3, but the second nip N2 of the press is an
extended
nip which is formed between the centre roll 1 and a belt mantle roll 5
provided as
a second backup roll. The directions of nip planes B-B, C-C differ
substantially
from each other in the embodiment of Fig. 4 too. As was already previously
mentioned in connection with prior art, an extended nip causes problems of its
own
in journalling of a roll especially for the reason that both of the rolls
forming such
an extended nip are subjected to very high forces from the nip. In the
arrangement
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9
of Fig. 4, this has been taken into account such that the main bearing
elements 10,30
in the journalling of the centre roll 1 are arranged to act in the nip plane C-
C of the
extended nip N2 between the centre roll 1 and the belt mantle roll 5.
Similarly, a
counter-bearing element 20 is also mounted to act in a direction opposite to
said
second nip plane C-C with respect to the main bearing elements 10,30. In
addition
to the main bearing elements 10,30 and the counter-bearing element 20, the
journalling system in the embodiment of Fig. 4 is provided further with an
additional
element 50 which is arranged to act almost in the direction of the first nip
plane B-B
so that said additional bearing element 50 substantially receives together
with the
counter-bearing element 20 the load directed to the bearings from the first
nip N 1.
A feature common to the journalling arrangements for the centre roll I of the
press
shown in Figs. 2-4 and differing from the arrangement shown in Fig. 1,
intended
for journalling a calender roll in particular, is that in the centre roll
application the
journalling arrangement is intended only for journallin~ of the roll, and the
nips are
not intended to be opened and closed by means of the bearing elements, but the
opening and the closing are intended to be taken care of by other more
conventional
means. It would indeed be difficult to accomplish the opening and the closing
of the
nips in the arrangements shown in Fig. 2-4 because the centre roll forms two
nips
while the nip planes pass substantially across each other.
Above, the invention has been described by way of example with reference to
the
figures in the accompanying drawing. The invention is, however, not confined
to
relating only to the examples illustrated in the figures, but different
embodiments of
the invention may vary within the scope of the inventive idea defined in the
accom-
panying claims.
