U.S. patent application number 16/076949 was filed with the patent office on 2019-02-14 for arrangement for supporting a rotary drum.
The applicant listed for this patent is HOLCIM TECHNOLOGY LTD. Invention is credited to Thomas STUTZ.
Application Number | 20190049182 16/076949 |
Document ID | / |
Family ID | 58185557 |
Filed Date | 2019-02-14 |
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United States Patent
Application |
20190049182 |
Kind Code |
A1 |
STUTZ; Thomas |
February 14, 2019 |
ARRANGEMENT FOR SUPPORTING A ROTARY DRUM
Abstract
An arrangement for supporting a rotary drum, the rotary drum
having at least three riding rings distributedly arranged along the
axial direction of the rotary drum, the arrangement including a
pair of relatively spaced rollers for supporting a riding ring, at
least one bearing for each roller, a support for each bearing
mounted for movement of the roller toward and away from the shell
of the rotary drum and a spring system exerting a spring force
acting on the support to counteract the weight of the rotary drum
resting on the rollers, wherein the spring system includes a
pressure vessel charged with a compressed gas that exerts the
spring force and the rotary drum includes at least three riding
rings and only at least one middle ring arranged between two outer
rings is supported by a pair of relatively spaced rollers that are
equipped with the spring system.
Inventors: |
STUTZ; Thomas; (Holderbank,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HOLCIM TECHNOLOGY LTD |
Jona |
|
CH |
|
|
Family ID: |
58185557 |
Appl. No.: |
16/076949 |
Filed: |
February 10, 2017 |
PCT Filed: |
February 10, 2017 |
PCT NO: |
PCT/IB2017/000102 |
371 Date: |
August 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F27B 2007/261 20130101;
F27B 7/42 20130101; F16C 13/04 20130101; F27B 2007/2253 20130101;
F16C 19/507 20130101; F27B 7/2206 20130101; F27B 2007/228 20130101;
F27B 7/22 20130101 |
International
Class: |
F27B 7/22 20060101
F27B007/22; F16C 13/04 20060101 F16C013/04; F16C 19/50 20060101
F16C019/50; F27B 7/42 20060101 F27B007/42 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2016 |
AT |
A 72/2016 |
Claims
1. An arrangement for supporting a rotary drum, said rotary drum
having at least three riding rings distributedly arranged along the
axial direction of the rotary drum, the arrangement comprising a
pair of relatively spaced rollers for supporting a riding ring, at
least one bearing for each roller, a support for each bearing
mounted for movement of the roller toward and away from the shell
of the rotary drum and spring means exerting a spring force acting
on the support so as to counteract the weight of the rotary drum
resting on the rollers, wherein the spring means comprise a
pressure vessel charged with a compressed gas that exerts the
spring force and wherein the rotary drum comprises at least three
riding rings and only at least one middle ring arranged between two
outer rings is supported by a pair of relatively spaced rollers
that are equipped with said spring means comprising the pressure
vessel charged with the compressed gas.
2. The arrangement according to claim 1, wherein the support is
mounted for pivotal movement about a pivot axis and the spring
means are arranged to act on the support at a distance from the
pivot axis of the support that is larger than the distance of the
roller from the pivot axis.
3. The arrangement according to claim 1, wherein the spring means
comprise a fluid chamber configured to change its volume upon
movement of the roller under the weight of the rotary drum resting
on the rollers, wherein said chamber is fluidly connected to the
pressure vessel by means of a fluid line.
4. The arrangement according to claim 3, wherein two bearings are
provided for each roller and wherein each of the two bearings has a
support, wherein a fluid chamber is assigned to each of the two
supports, wherein the two chambers are fluidly connected to the
pressure vessel by means of a fluid line each.
5. The arrangement according to claim 3, wherein the fluid chamber
comprises an elastically deformable shell.
6. The arrangement according to claim 1, wherein the spring means
are designed as a pneumatic spring.
7. The arrangement according to claim 3, wherein the fluid chamber
and the pressure vessel are filled with compressed gas.
8. The arrangement according to claim 3, wherein the fluid chamber,
the fluid line and a lower part of the pressure vessel are filled
with a liquid, the remaining, upper vessel volume being filled with
compressed gas.
9. The arrangement according to claim 3, wherein the fluid chamber
is realized in a cylinder of a hydraulic cylinder-piston unit,
wherein the cylinder or the piston is mechanically coupled to the
support, and wherein the fluid chamber of the cylinder is fluidly
connected to the pressure vessel.
10. The arrangement according to claim 9, wherein the fluid
chamber, the fluid line and a lower part of the pressure vessel are
filled with hydraulic oil, the remaining, upper vessel volume being
filled with compressed gas.
11. The arrangement according to claim 1, wherein a compressor is
connected to the pressure vessel for compressing gas contained in
the vessel.
12. (canceled)
13. The arrangement according to claim 1, further comprising at
least one sensor for measuring the vertical position of the riding
ring relative to a stationary reference point and/or for measuring
the vertical position of the rotary drum adjacent the rollers
relative to a stationary reference point.
14. The arrangement according to claim 1, wherein the rotary drum
is a rotary kiln of a cement manufacturing installation.
15. The arrangement according to claim 5, wherein the fluid chamber
is designed as an air-suspension bellow.
16. The arrangement according to claim 7, wherein the fluid chamber
and the pressure vessel are filled with compressed air.
17. The arrangement according to claim 8, wherein the fluid
chamber, the fluid line and the lower part of the pressure vessel
are filled with a water, and the remaining, upper vessel volume is
filled with compressed air.
18. The arrangement according to claim 10, wherein the remaining,
upper vessel volume is filled with compressed nitrogen.
Description
[0001] The invention refers to an arrangement for supporting a
rotary drum, in particular a rotary kiln of a cement manufacturing
installation, said rotary drum having at least three riding rings
distributedly arranged along the axial direction of the rotary
drum, the arrangement comprising a pair of relatively spaced
rollers for supporting a riding ring, at least one bearing for each
roller, a support for each bearing mounted for movement of the
roller toward and away from the shell of the rotary drum and spring
means exerting a spring force acting on the support so as to
counteract the weight of the rotary drum resting on the
rollers.
[0002] An arrangement of this kind is disclosed in U.S. Pat. No.
2,551,774 and U.S. Pat. No. 4,171,949.
[0003] As mentioned in U.S. Pat. No. 4,171,949 rotary drums, such
as rotary dryers, tube mills, drum sieves and particularly rotary
kilns are commonly supported by roller supports. The rotary drums
usually are provided with two or more ring-like members known as
track rings or riding rings, which are secured to the outer
circumference of the drum body. Each riding ring rests upon a pair
of the rollers. These rollers are each rotatably supported in at
least one bearing, which is mounted on solid foundations.
[0004] Ideally, the outer surface of the riding ring bears
correctly against the outer surface of the rollers along a common
generatrix. The drum with its riding rings then is correctly
aligned with the rollers in a vertical plane and along the axis of
the drum. However, under certain operation conditions cranks may be
observed. Cranks are straightness deviations of the drum that can
be so strong, that the riding ring of the drum lifts from the
support rollers once per revolution. Further, cranks lead to a
cyclic overload of the support rollers and the riding ring. The
cranks are typically caused by uneven temperature or overheating of
the drum shell. Uneven temperatures in the drum shell can occur
regularly, depending on the uniformity of kiln operation.
[0005] Under unfavourable conditions, the load on the rollers may
increase to a multiple of the normal load for which the rollers are
designed. Such loads result in localized contact pressures between
the riding ring and the rollers, which cause severe damage to the
riding rings and the rollers. Because of the unequal distribution
of the load on the rollers, a total breakdown or collapse of the
rollers may result.
[0006] To compensate for such cyclic overloads, it is possible to
provide the drums with rollers that are designed to take these
conditions into account. For example, the rollers may be supported
pivotally in bearings to compensate for axial misalignment, and the
bearings may be resiliently supported to compensate for
misalignment in the vertical and/or horizontal plane. In
particular, a housing for each bearing of the rollers may be
supported directly or indirectly by a hydraulic cylinder or a
flexible cushion. More particularly, the housing may be supported
on a rocker pivoting about an axis substantially parallel to the
axis of the drum. As a result of the prior art arrangements, the
rollers tend to follow the riding ring track on the drum, but
inadvantageously, localized pressure still exists. This is
especially true with relatively large compensating movements of the
rollers. The reason is that the forces exerted by the spring means
acting on the support of the roller bearings increase with
increasing compensating movement path, because of linear or
progressive spring characteristics.
[0007] A further disadvantage of prior art supporting arrangements
is that the spring means, such as hydraulic cylinders, are
difficult to arrange in the region below the rollers because of the
limited space available. This problem is particularly relevant when
spring means are to be retrofitted in existing installations.
[0008] Therefore, it is an object of the invention to provide an
improved support for a rotary drum that allows further reducing or
even completely preventing cyclic overloads of the supporting
rollers. Further, it is an object of the invention to reduce the
vertical space needed for arranging the spring means below the
rollers.
[0009] To solve this object the invention in an arrangement of the
initially defined kind essentially consists in that the spring
means comprise a pressure vessel charged with a compressed gas that
exerts the spring force. Thus, the spring force counteracting the
weight of the rotary drum resting on the rollers is not provided
exclusively by a pressurized liquid fluid, such as a hydraulic oil
of a cylinder-piston unit, but comprises the effects of a
compressed gas cushion. In this way, an optimization of the spring
characteristics may be achieved, resulting in that the spring force
does not considerably increase as a function of the displacement
path of the rollers. Further, an additional advantage of the
embodiment according to the invention is that the pressure of the
compressed gas contained in the pressure vessel can easily be
adjusted to the optimal level, in which the rollers are taking up
the nominal design load of the rotary drum, without substantially
changing the spring characteristics of the spring means.
[0010] Further, the pressure vessel must not necessarily be
arranged in the region below the rollers, but may be arranged
beside the supporting structure so that retrofitting of existing
installations is easily feasible without substantially increasing
the vertical space needed below the rollers.
[0011] In order to minimize frictional losses of the compensation
mechanism, a preferred embodiment of the invention provides that
the support is mounted for pivotal movement about a pivot axis like
a hinge. The spring means are preferably arranged to act on the
support at a distance from the pivot axis of the support that is
larger than the distance of the roller from the pivot axis. In this
way, a larger lever arm is effective for the spring means than for
the supporting rollers so that the spring means may be operated at
a lower pressure level in the pressure vessel.
[0012] Pivotal mounting of the support has considerable advantages
over a sliding mounting of the support in a lateral direction. A
sliding arrangement of the support results in higher frictional
forces and the forth-and-back motion of the support does not behave
in direct proportionality to the forces acting on the rollers, but
a hysteresis is to be observed. The combination of a pivotal
mounting of the support with an air cushion as the spring means
results that the rollers follow the riding ring track in a very
precise, direct and frictionless manner.
[0013] In order to reduce the vertical space needed for installing
the spring means below the rollers, the fluid system comprising the
compressed medium is preferably divided into two separate fluid
volumes, one fluid volume being arranged below the support of the
roller bearings and the other fluid volume being arranged in the
pressure vessel. In this way, only part of the total compressed
fluid volume is arranged below the support of the roller bearings
so that account is taken of the limited vertical space there. In
this connection, a preferred embodiment is devised such that the
spring means comprise a fluid chamber designed so as to change its
volume upon movement of the roller under the weight of the rotary
drum resting on the rollers, wherein said chamber is fluidly
connected to the pressure vessel by means of a fluid line.
[0014] A pressure vessel may be used for exerting a spring force on
only one bearing support or on two or more bearing supports. In
case of two or more roller bearings being supported by spring
means, the spring means of each bearing support may comprise its
own pressure vessel.
[0015] Alternatively, the spring means associated to two bearings
belonging to the same roller may share a common pressure vessel. In
this connection, a preferred embodiment of the invention is devised
such that two bearings are provided for each roller and that each
of the two bearings has a support, wherein a fluid chamber is
assigned to each of the two supports, wherein the two chambers are
fluidly connected to the common pressure vessel by means of a fluid
line each. Preferably, no fluid chambers of other supports than the
supports of said two bearings are fluidly connected to said common
pressure vessel.
[0016] In a further alternative, the spring means associated to all
bearings of the pair of rollers supporting a riding ring may share
a common pressure vessel.
[0017] In a preferred embodiment of the invention the fluid chamber
comprises an elastically deformable shell, and is preferably
designed as an air-suspension bellow or a flexible cushion. Such a
fluid chamber that is preferably arranged below the roller bearing
support does not only allow a vertical compensational movement of
the roller, but may also a allow a horizontal flexibility so as to
absorb thermal expansion of the support.
[0018] The invention may work with pressurized fluid systems.
According to a first embodiment, the spring means are designed as a
pneumatic spring. Thus, the spring force acting on the support is
directly exerted by the pressurized gas. In particular, the fluid
chamber and the pressure vessel are filled with compressed gas, in
particular compressed air.
[0019] According to a second embodiment, the fluid chamber, the
fluid line and a lower part of the pressure vessel are filled with
a liquid, in particular water or hydraulic oil, the remaining,
upper vessel volume being filled with compressed gas, in particular
compressed air or compressed nitrogen. Thus, the compressed gas is
only indirectly exerting the spring force on the roller bearings
support, namely via the pressurized liquid, in particular water or
hydraulic oil, that is arranged between the compressed gas being
present in the pressure vessel and the support. The advantage of
this embodiment is the possibility of introducing a leak-stop
valve, which can block water exit in case of a leakage of the
spring means.
[0020] According to a third embodiment, the fluid chamber is
realized in a cylinder of a hydraulic cylinder-piston unit, wherein
the cylinder or the piston is mechanically coupled to the support,
and that the fluid chamber of the cylinder is fluidly connected to
the pressure vessel, a so-called accumulator. Preferably, the fluid
chamber, the fluid line and a lower part of the accumulator are
filled with a liquid, in particular hydraulic oil, the remaining,
upper vessel volume being filled with compressed gas, in particular
compressed nitrogen. Common types of accumulators may be used, such
as a bladder accumulator and a piston accumulator.
[0021] In said third embodiment the hydraulic cylinder-piston unit
may preferably be coupled to the support by means of a rolling
contact, wherein at least one contacting surface at the contact
between the hydraulic cylinder-piston unit and the support has a
curved configuration. Further, a rolling contact may also be
provided between the hydraulic cylinder-piston unit and its
foundation, wherein at least one contacting surface at the contact
between the hydraulic cylinder-piston unit and its foundation has a
curved configuration. In this way, it is possible to absorb any
angular movement of the movable bearing support and to adjust to
the given geometry of the foundation so as to have uniform contact.
The rolling contact preferably takes place via curved swivel
plates, which are mounted to the side of the hydraulic
cylinder-piston unit contacting the foundation and/or to the side
of the hydraulic cylinder-piston unit contacting the bearing
support. The swivel plate preferably has a monoaxially, in
particular cylindrically, curved contacting surface. Preferably,
two swivel plates are arranged on top of each other, wherein the
axis of curvature of the monoaxially curved surface of the first
swivel plate and the axis of curvature of the monoaxially curved
surface of the second swivel plate are arranged at an angle of
90.degree.. The swivel plates are thus preferably based on the
principle of a rocking chair with convex curved surfaces and are
able to absorb angular deviations in all directions.
[0022] The advantage of the above mentioned embodiment is that the
cylinder-piston unit is rolling on the surface of the counterpart,
i.e. on the bearing support of the rollers and/or on the
foundation, instead of sliding for example in a spherical
bearing.
[0023] In all three embodiments of the spring means, the required
spring characteristics, namely the softness of the spring means
comes from the compressed gas that is arranged in the pressure
vessel.
[0024] In order to enable an adjustment of the pressure of the
fluid medium in the spring means, a compressor is preferably
connected to the pressure vessel for compressing gas contained in
the pressure vessel. In case of a liquid fluid, such as a hydraulic
oil, being contained in the system, the pressure of the fluid
medium can also be adjusted by adding or removing a certain amount
of the liquid fluid in the system. In particular, the filing of the
oil level may be adjusted by means of a hydraulic unit.
[0025] Further, the behaviour of the spring means may be adjusted
by increasing or reducing the volume of the pressure vessel.
Therefore, according to a preferred embodiment, the pressure vessel
is fluidly connected to at least one additional pressure vessel by
means of a fluid line that is equipped with a shut-off valve. In
this way, it is possible to selectively connect or disconnect the
volume of the additional pressure vessel to or from the volume of
the pressure vessel so as to increase or reduce the total volume
that can be filled with compressed gas. For example, enlarging the
total volume that can be filled with compressed gas while
maintaining the gas pressure allowing for an increased travel path
of the rollers without changing the stiffness of the spring
means.
[0026] In case of a rotary drum that is equipped with three or more
riding rings, the inventive roller support is preferably only
required for the middle ring(s). In this connection, a preferred
embodiment of the invention is devised such that the rotary drum
comprises at least three riding rings and only at least one middle
ring arranged between two outer rings is supported by a pair of
relatively spaced rollers that are equipped with said spring means
comprising a pressure vessel charged with a compressed gas, wherein
the pressure in the pressure vessel is adjusted so that the
resulting force counteracting the weight of the rotary drum resting
on the rollers corresponds to the nominal design load taken up by
the rollers supporting the middle ring. In case of a rotary drum
that is equipped with three riding rings, only the middle ring
arranged between the two outer rings is supported by a pair of
relatively spaced rollers that are equipped with the inventive
spring means. In case of a rotary drum that is equipped with four
riding rings, only the two middle rings arranged between the two
outer rings are supported by a pair of relatively spaced rollers
that are equipped with the inventive spring means.
[0027] Supporting only the middle ring(s) by means of the spring
means ensure for less eccentricity of the rotary drum. Further, the
installation and operating investment and efforts are greatly
reduced without negatively affecting the compensating movement of
the rollers. Further, it has been observed that especially the
middle region of a rotary kiln is usually exposed to high weight
loads, because the material deposits on the inner wall of the kiln
mostly accumulate in the middle of the rotary kiln, which leads to
the highest eccentric loads.
[0028] The invention provides for the effect that the rollers
assigned to the middle ring(s) are substantially constantly
contacted by the riding ring. In a preferred embodiment, this
enables the rollers assigned to the middle ring(s) of the drum to
function as the rotary drive for imparting rotational movement to
the rotary drum. Thus, said middle rollers may be coupled to a
drive arrangement, such as a motor, for rotating the rollers,
wherein the rotation of the rollers is transferred to the riding
ring by the friction occurring between the surface of the rollers
and the riding ring.
[0029] In order to minimize the bending stresses and to avoid
fatigue cracks in the drum shell, it is important to keep the drum
aligned. The drum is aligned when the centres of the three or more
riding rings are arranged in one straight line. Keeping the centres
of all riding rings in one straight line is more easily achieved in
an arrangement, where only the middle riding ring(s) of the drum
is/are supported by the inventive spring means and the outer riding
rings are supported on rigidly supported rollers. According to a
preferred embodiment of the invention, a alignment of the centres
of the riding rings is achieved by adjusting the height of the
rollers that support the middle ring(s) so as to align the centre
of the middle ring(s) with the centre of the outer rings. The
height adjustment is preferably realized by adjusting the fluid
pressure prevailing in the fluid chamber.
[0030] In a situation where a crank is present in the drum, the
centre of the riding ring(s) that is/are supported by the inventive
spring means rotates eccentric on an orbit. In this case, the
centre of said orbit is aligned with the centres of the other
riding rings.
[0031] In order to determine, whether the centre of the riding ring
or its orbit is misaligned, the arrangement preferably comprises at
least one sensor for measuring the vertical position of the riding
ring relative to a stationary reference point, such as a
foundation. Instead of measuring the vertical position of the
riding ring, the sensor can also be arranged to measure the
vertical position of the drum adjacent the support rollers relative
to a stationary reference point, such as a foundation.
[0032] The sensor can be mounted to the foundation or any other
stationary structure around the drum and may be configured as a
distance sensor to measure its distance to the outer surface of the
riding ring or to the drum near the supports for the rollers.
Preferably, the distance sensor is configured as an ultrasound
distance sensor. Preferably, the sensor is arranged below the
riding ring between the rollers of the pair of rollers supporting
said riding ring. Preferably the sensor is configured to
continuously measure the vertical position. Alternatively also the
height position of the rollers, or any other part that follows the
eccentric movement of the drum, can be measured by a suitable
sensor.
[0033] Due to the eccentric movement of the drum and the riding
ring, the height sensors measure a constant change in height.
Therefore, in order to obtain the height position of the centre of
the orbit, the measured values are preferably sampled and the
average is calculated over each full turn of the rotary drum. Said
average value is representing the center of the orbit.
[0034] A control system is preferably provided for maintaining the
center height of the orbit at a fixed set point, where the rotary
kiln axis is straight.
[0035] An adjustment of the height may also be required in order to
compensate for weight variations of the rotary drum. When the
weight changes, the drum applies more load to the rollers,
whereupon the rotary drum deflects and the center of the roller
orbit goes down. The deviation on height is detected by the control
system, which is counteracting by increasing the pressure to bring
the center height back to the set point.
[0036] To increase the height, the pressure in the system is
preferably increased. To decrease the height, the pressure in the
system is preferably decreased. The pressure adjustments are
preferably done by adding or releasing gas or hydraulic oil,
depending on the system.
[0037] The invention will now be described in more detail with
reference to exemplary embodiments illustrated in the drawings.
[0038] FIG. 1 shows a rotary kiln with a straightness deviation of
the kiln tube in a first angular position,
[0039] FIG. 2 shows the rotary kiln of FIG. 1 in a second angular
position,
[0040] FIG. 3 is a schematic axial view of the rotary kiln with
support rollers,
[0041] FIG. 4 is a perspective view of the rotary kiln of FIG.
3,
[0042] FIG. 5 is a schematic illustration of a first embodiment of
spring means for supporting the rollers,
[0043] FIG. 6 is a schematic illustration of a second embodiment of
spring means for supporting the rollers,
[0044] FIG. 7 is a schematic illustration of a third embodiment of
spring means for supporting the rollers,
[0045] FIG. 8 is a detailed view of the piston of the third
embodiment of the spring means for supporting the rollers as shown
in FIG. 7 and
[0046] FIG. 9 corresponds to the schematic axial view of the rotary
kiln with support rollers depicted in FIG. 3, but equipped with
height sensors and the piston of FIG. 8.
[0047] In FIG. 1 the shell of a rotary kiln 1 is denoted by 2. The
rotary kiln 1 has three riding rings 3, 4 and 5 distributedly
arranged along the axial direction of the rotary kiln 1. Each ring
3,4,5 is supported by a pair of rollers 6. The shell 2 of the
rotary kiln has a crank 7, which has the shape of a straightness
deviation in the middle region of the kiln 1. As shown in FIG. 1
the crank 7, during the rotation of the kiln 1 about its axis 8,
gets in an upper position, in which the middle riding ring 4 of the
kiln 1 can in extreme cases lift from the associated support
rollers 6. This results in that the rollers 6 supporting the middle
ring 4 are taking up a considerably lower load than the
corresponding nominal design load or even no load at all, while the
rollers 6 associated to the outer rings 3 and 5 have to take up an
accordingly higher load. In FIG. 2 the crank 7, half a revolution
later, is shown in a lower position, in which the middle ring 4
exerts an very high overload on the associated rollers, while the
rollers 6 associated to the outer rings 3 and 5 take up a lower
load than the nominal load. Thus, a crank as shown leads to a
cyclic overload of all supporting rollers once per revolution. As a
consequence, the lifetime of the riding rings and the support
rollers gets drastically reduced.
[0048] As shown in FIG. 3, the rollers 6 have roller shafts 9 that
are rotatably held in bearings 10. Each bearing 10 is mounted to a
support 11. The supports 11 in their end regions facing to each
other are pivotably mounted to a fixed mount 12 so as to be
pivotable about the pivot axis 13, which enables movement of the
rollers 6 toward and away from the shell 2 of the rotary kiln 1.
Such movement allows the rollers 6 to compensate for or follow the
eccentric movements of the riding ring 4 due to straightness
deviations of the shell 2. In the opposite end region the supports
11 are supported on a foundation 14 via spring means generally
denoted by 15. The spring means are exerting a spring force acting
on the associated support 11 so as to counteract the weight of the
rotary kiln 1 resting on the rollers 6. The spring force is
adjusted such that the rollers 6 are in their neutral position when
the nominal load is acting on the rollers 6. The spring means 15
are preferably configured with a spring characteristics such that
the spring force acting on the support 11 remains substantially
constant also during the compensation movements of the rollers 6
mentioned above.
[0049] FIG. 4 shows that each roller 6 has two bearings 6 and two
associated supports 11. Further, each support 11 is supported by
its own spring means 15.
[0050] In order to achieve the required spring characteristics, the
spring means comprise a pressure vessel charged with a compressed
gas that exerts the spring force. In a first embodiment shown in
FIG. 5 the spring means 15 are designed as a pneumatic spring and
comprise a fluid chamber 16 designed so as to change its volume
upon movement of the roller 6 under the weight 17 of the rotary
kiln 1 resting on the rollers 6. The chamber may be realized as an
air-suspension bellow 16. The bellow 16 is fluidly connected to the
pressure vessel 18 by means of the fluid line 19. The entire system
consisting of the bellow 16, the fluid line 19 and the pressure
vessel or air tank 18 is filled with compressed air, wherein a
compressor (not shown) is used to pressurize the system.
[0051] In the second embodiment shown in FIG. 6 the flexible
chamber 16, the connection line 19 and the lower part of the
pressure vessel 18 are filled with water 21, whereas the softness
of the spring system is achieved by the compressed air 20 that is
present in the upper part of the vessel 18. The advantage of this
combined air-water system is the possibility of introducing a
leak-stop valve 22, which can block water exit in case of a leakage
in the spring system.
[0052] In the third embodiment shown in FIG. 7 the fluid chamber 16
is realized in a cylinder 23 of a hydraulic cylinder-piston unit,
wherein the piston 24 is mechanically coupled to the support 11.
The fluid chamber 16 of the cylinder 23 is fluidly connected to the
accumulator 18 via the fluid line 19. The fluid chamber 16, the
fluid line 19 and a lower part of the accumulator 18 are filled
with hydraulic oil 25, the remaining, upper vessel volume being
filled with compressed gas, in particular compressed nitrogen 26.
Thus, a hydraulic cylinder is used instead of a pneumatic spring,
wherein the required spring characteristics is achieved by the
vessel 18 functioning as nitrogen accumulator. In order to adjust
the fluid pressure in the fluid system, a pump unit 30 is
preferably provided that is connected to the fluid line 19. The
pump unit 30 serves to pump an additional amount of hydraulic oil
into the fluid system.
[0053] The advantage of the air spring systems according to FIGS. 5
and 6 when compared to a hydraulic cylinder according to FIG. 7 is
that air springs are simpler in construction and cheaper and that
no sealings are required that are subject to wear. Further, air
springs require considerably less vertical space.
[0054] FIG. 8 shows a detailed view of the hydraulic
cylinder-piston unit of the third embodiment of the spring means
for supporting the rollers as shown in FIG. 7, whereby in said
embodiment the hydraulic cylinder-piston unit is contacting the
support 11 by means of swivel plates 27a and 27b.
[0055] Further, the hydraulic cylinder-piston unit is contacting
the foundation 14 by means of a swivel plate 27c. The swivel plates
27a, 27b and 27c each comprise a curved surface, so as to absorb
any angular movement of the support 11 and to adjust to the given
geometry of the foundation. The swivel plates 27a and 27b are
arranged on top of each other and each have a monoaxially curved
surface, wherein the axis of curvature of the swivel plate 27a is
at an angle of 90.degree. relative to the axis of curvature of the
swivel plate 27b.
[0056] FIG. 9 shows a schematic axial view of the rotary kiln 2
with support rollers 6 as in FIG. 3, but equipped with height
sensors 28 and 29 and with the hydraulic cylinder-piston unit as
described with regard to FIG. 8. Sensor 28 is mounted to the fixed
mount 12 and continuously measures its distance to the outer
surface of the riding ring 4. Furthermore two height sensors 29 are
mounted near the supports 11 for the rollers 6 on each side of the
arrangement, whereby the sensors 29 continuously measure the height
of the support 11 of the rollers 6. The sensor 28 and the sensors
29 can be used as an alternative.
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