Note: Descriptions are shown in the official language in which they were submitted.
CA 02290291 1999-11-24
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to a calender roll heatable with a heating
medium, in particular, to a calender roll for glazing, and including a hollow
roll
body provided with a displacement body and supported at its opposite ends by
flanged journals.
2. Description of the Prior Art
Calender rolls of the type discussed above are used for finishing or
glazing of paper in a calender. An effective uniform heating of the roll body
surface is achieved by providing in the roll body a plurality of peripheral
bores
through which a heating medium passes. Also, the inner surface of the roll
body is heated, and by appropriate shaping of the displacement body, the
clearance between the inner surface of the roll body and the displacement body
has been so reduced that the obtained velocities of the heating medium
permitted to insure a good heat transfer. The roll body, which is provided
with
the peripheral bores, is also provided with a central bore for purposes of
reducing weight of the roll body. While the loss of the central, neutral phase
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reduces the weight, the load capacity is reduced only to a small degree. The
hollow space of the roll body can be either filled or be prevented from being
filled with the heating medium.
Usually, with this design of the calender roll, the displacement body in
particular is formed of sheet steel within narrow tolerances, is inserted into
the
roll body, and is connected therewith. It means that with a rapid change of
the
speed of the calender roll and, in particular, at a sharp breaking of the
calender
roll, the elements connecting the displacement body with the roll body are
subjected to high loads which can lead to their distraction and to a damage of
the displacement body because of overload. Usually, when the metal sheet has
a high specific weight, balancing of the calender roll is necessary. It is
also
critical to be able to sense the thermal deformation of the elements of the
displacement body, which affect the roll body, in particular, at its end and
in
connection region.
Accordingly, an object of the present invention is to provide a
displacement body insertable in the central bore of the roll body and devoid
of
drawbacks of conventional displacement bodies.
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SU1~ARY OF THE INVENTION
This and other objects of the present invention,
which will become apparent hereinafter, are achieved by
providing a displacement body formed of a material having a
specific weight smaller than the specific weight of a
material the roll body is formed of. The formation of the
displacement body of a plastic material or another light
material, permits to connect the displacement body with the
roll body by press fit or by other connection means, without
a need the resilience of the plastic material, the
displacement body is made of, matched the required fit
accuracy which was necessary with the displacement bodies
formed of sheet steel. Also, with the materials having a
reduced specific weight, the balancing problems are reduced,
and a damaging heat transfer, at the end and suspension
regions, is eliminated due to a small thermal capacity of
plastic materials. An easy workability of the plastic
materials permits to provide a construction which insures
good steam-condensate separation and an easy discharge of
the heating medium. With supercalender and calender formed
in accordance with the new concept, such as Janus*, Prosoft*
and Optiload*, with surface temperatures between 70 and about
135°, the displacement body can be formed of conventional
plastic materials. Only with the rolls for soft calenders
with surface temperatures up to 200°, the selection of
particular heat-resistant plastic materials becomes
necessary.
Thus, according to the present invention there is
provided a calender roll heatable with a heating medium,
comprising a roll body having a central bore; flanged
* Trade-mark
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journals provided at opposite sides of the roll body for
supporting same; and a displacement body arranged in the
central bore of the roll body and formed of a material
having a specific weight smaller than a material of the roll
body.
The novel features of the present invention, which
are considered as characteristic for the invention, are set
forth in particular in the appended claims. The invention
itself, however, both as to its construction and its mode of
operation, together with additional advantages and objects
thereof, will be best understood from the following detailed
description of preferred embodiment, when read with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 shows a longitudinal cross-sectional view
of a calender roll with bores formed in its periphery;
Fig. 2 shows a cross-sectional view along line 2-2
in Fig. 1;
Fig. 3 shows a longitudinal cross-sectional view
of a calender roll the displacement body of which, formed of
a plastic material, is formed as a plastic tube closed
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CA 02290291 1999-11-24
from both side with flanges and the wall of which is
provided with grooves through which a heating
medium can flow;
Fig. 4 shows a view of an involuate section of a jacket of a
displacement body of a calender roll provided with
grooves for a heating medium which, to simplify
representation, are shown as extending parallel to the
axis;
Fig. 5 shows a cross-sectional view of a calender roll formed
as one-piece with a displacement body made of plastic
material for a two-way connection head;
Fig. 6 shows a schematic view of a displacement body with
a groove for the heating medium being formed as a
double helix, with the two grooves passing into each
other at their leftside ends and with their rightside
ends being connected with a two-way connection
head;
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Fig. 7a shows a cross-sectional view of a first cut-out of a
vertical section of the displacement body shown in
Fig. 6;
Fig. 7b shows a cross-sectional view of a second cut-out of a
vertical section of the displacement body shown in
Fig. 6;
Fig. 8 shows a cross-sectional view of a calender roll
somewhat similar to that of Fig. 5 and including a
displacement body formed of a jacket and cover plates
and through which a pipe extends;
Fig. 9-11 show a view similar to that of Fig. 4 with different
flow pattern of the heating medium; and
Fig. 12 shows a cross-sectional view of another embodiment
of a calender roll according to the present invention
with peripheral bores and with return conduit for the
heating medium being formed by a clearance between
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the wall of the roll and the displacement body or by
groove-forming channels.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A heatable calender roll according to the present invention, which is
shown in Fig. 1, has a hollow cylindrical body 1 which is supported by flanged
journals 2 provided on opposite sides of the cylindrical body 1. The hollow
cylindrical body 1 of the inventive calender roll has a plurality of
peripheral
bores 3, through which a heating medium can flow, and a central bore 4 having
a larger diameter. For feeding and return of the heating medium, at an end of
one of the flanged journals 2, there is provided a two-part connection head 5.
Alternatively, a one-part connection head 5 can be provided at an end of each
of
the two flanged journals 2.
A displacement body 6 is provided in the central bore 4 of the calender
roll body 1. The displacement body 6 is formed of a plastic material as a
solid
body. The displacement body 6 can be fixedly connected with the calender roll
body 1 simply by being pressed into the central bore 4. Care should be taken
not to form the displacement body 6 with the same outer diameter exceeding the
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inner diameter along its entire length. Rather, only separate sections 7 of
the
displacement body 6 should be formed with an outer diameter exceeding the
inner diameter of the calender roll body 1 which insures an adequate press
fit.
The sections of the displacement body 6 located between the sections 7 have a
reduced outer diameter. Alternatively, the displacement body 6 can, e.g., be
formed of a plurality of separate sections which are pressed into the roll
body 1
one after another.
The outer surface of the calender roll body 1 can be provided with a
coating 8.
The return flow of the heating medium to the connection head 5 can be
effected in a simple way through the central bore 9. Should it be necessary,
the
central bore 9 can be formed by expanding the pipe, if necessary, only
partially.
It is also possible to provide one or several grooves 10, which can extend
parallel to the calender roll axis, be formed as a helix and the like, for
returning
the heating flow to the connection head 5. The groove or grooves 10 can be
drawn along the outer surface of the displacement body 6. With a
corresponding layout of the grooves, they can be used for heating the inner
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surface of the calender roll body. By reducing their cross-section in the flow
direction of the heating medium, the action of an increased cooling in the
heating medium flow direction can be compensated. If necessary, in
association with peripheral bores or only for the later, arbitrary flow
patterns
can be developed, e.g., two parallel conduit branches arranged in series with
a
further branch.
A further reduction in weight of a calender roll can be achieved when
instead of a solid pressed-in block formed of a plastic material, a block,
which
is formed of a foamed plastic material, preferably with closed pores, is used
as a
displacement body.
The easy processability of the plastic material permits to economically
form special features of a calender roll. Thus, in particular in steam-heated
rolls, axial steam feeding bores or steam feeding bores extending parallel to
the
roll axis in the surface of the plastic displacement body, which is opposite
to the
calender roll body, can be so arranged in the same way as axial condensate
discharging bores or condensate discharging bores extending parallel to the
roll
axis. For collecting the condensate, the displacement body 6 can be provided
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with corresponding, preferably deepened grooves, radial circularly extending
grooves at the ends of the displacement body 6. Further, turned grooves in the
end portions of the central bore 4 proved themselves. Also, the supply of the
peripheral bores 3 with the heating medium can be effected, with the given
pattern, by additional shaping of the displacement body or at least its end
portion. Advantageously, the easy processability, just as the small specific
weight of the plastic material, facilitate or makes unnecessary the balancing
work. The displacement body and the built-in elements can be formed of a
plurality of parts and be connected by press fitting, by being screwed with
each
other, by being glued and welded to each other, and so forth.
Fig. 3 shows a calender roll the hollow cylindrical body 11 of which is
formed without peripheral bores. The calender roll body 11 is provided with a
displacement body 12 which is formed as a hollow body in a form of plastic
tube 13 which is closed at its opposite ends with plastic flanges 14. The
inner
surface of the roll body 11 and/or the vsrall of the displacement body 12 is
(are)
provided with grooves 15. The grooves 15 insure a direct contact of the
heating
medium with the inner surface of the roll body l, providing for the
transmission
of heat to the roll body 1. In principal, several grooves can be arranged
parallel
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30735-3 vv .:~ . .,~ w w y .. . . .
to each other as shown in the developed view shown in Fig. 4. However,
generally, there is provided a plurality of helix-shaped grooves entwined with
each other in a manner of a multiple thread. Already here, there exists a
possibility, during flow of the heating medium, to accelerate the velocity of
the
heating medium, which is cooled as a result of a heat exchange with the roll
body, by tapering the grooves, reducing their diameter. The increased velocity
of the cooled heating medium compensates the reduced temperature of the
heating medium, by changing the heat transfer coefficient in a way which
maintains the heat transfer substantially unchanged. .
Fig. 5 shows another embodiment of a heatable calender roll 16. The
calender roll 16 is provided with a solid plastic displacement body 17 vrhich
is
preferably formed of a foamed plastic material with closed pores. Here,
likewise, the grooves 15, which forms the channels for the heating medium, are
preferably formed as a helices. The heating medium that flows through the
grooves 15 accumulates in the chamber 18 and is discharged through a central
bore 9 of the displacement body 27 . Ai the end of the central bore 9, there
is
provided a pipe socket 19 which, on the other hand, can extend along an entire
length of the bore 9.
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However, a special bore, which serves for return of the heating medium,
can be dispensed with when the displacement body 17 has a shape shown in
Fig. 6 and has grooves 20, 21 which are formed in a manner of a double thread
and end, at the left end of the displacement body 17, either in a cage ring or
are
connected with each other in any other manner. Thereby, e.g., the groove 20
forms a first channel through which the heating medium flows along a helical
line to the opposite end of the displacement body and heats the calender roll
body, and returns from this end through the channel formed by the groove 21.
Because the delivery and discharge channels extend adjacent to each other, a
certain equalizing of the delivery and discharge temperature takes place. This
equalization further increases when, as shown in Figs. 7a and 7b, the groove
cross-sections in the flow direction are so reduced that the resulting
different
velocities produce the necessary changes in the heat transfer coefficient.
Fig. 8 shows yet another embodiment of a calender roll according to the
present invention the system of channels for heat medium corresponds to that
of
Fig. 5 but the displacement body of which is similar to that shown in Fig. 3.
The displacement body is made hollow in order to reduce weight. In this
embodiment, when it is desired that the return of the heating medium be
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effected through the chamber 18, it is necessary form the pipe socket as a
pipe
22 which should extend through the entire displacement body, including the
flanges. Further patterns of heat medium channels are shown in Figs. 9-11. In
Fig. 9, the channel-forming grooves extend parallel to each other as channel
15
in the tube 13 as it was discussed with reference to Fig. 4. In the embodiment
shown in Fig. 9, the displacement body, which is similar to the displacement
body 17 of Fig. 5, has two parallel grooves 23, 24 for delivery of the heating
medium, with the discharge or return channel being formed by a single groove
25. The three grooves 23, 24, 25 form a set which is repeated along the
circumference of the displacement body. Helical grooves can likewise be used.
In this embodiment, it can be conveniently provided for the flow of the
heating
medium through the delivery grooves 24 and 25 with a velocity reduced in
comparison with the velocity of the heating mechanism through the return
groove 25. Further changes in the flow pattern will now be discussed with
reference to Fig. 10.
In the embodiment of Fig. 10, the delivery and return grooves are formed
with different cross-sections. During manufacturing, the different cross-
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sections of the grooves can be achieved with different milling depths or by
using mill cutters having different widths.
In Fig. 10, the return groove 35 has a larger width than the delivery
grooves 33,34. In the pattern of Fig. 1 l, there are provided three grooves
26, 27
through which the heating medium consecutively flows and which provide a
double helix channel in which the different flow velocity are again obtained
by
forming the grooves with different widths and/or depths.
Finally, a yet another embodiment of a heatable calender roll will be
discussed with reference to Fig. 12. The calender roll body 1 corresponds to
that shown in Figs. 1-2 and, as in the embodiment of Figs. 1-2, it is provided
with peripheral bores 3. However, in the embodiment of Fig. 12, additional
heating is contemplated. The heating medium is supplied to the peripheral
bores through ascending bores 28 and is discharged from the peripheral bores 3
through discharge bores 29 and into a chamber 30. Then, the return heating
medium flows through channel-forming grooves 31 formed in the displacement
body 6. The channels, which are formed by grooves 31, are closed from outside
by the inner surface of the calender roll body 1. The heating of the calender
roll
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1 is effected in accordance with the patterns discussed with reference to
Figs. 4,
6 or 9 through 11.
Though the present invention was shown and described with references
to the preferred embodiments, such are merely illustrative of the present
invention and are not to be construed as a limitation thereof and various
modifications of the present invention will be apparent to those skilled in
the
art. It is therefore not intended that the present invention be limited to the
disclosed embodiments or details thereof, and the present invention includes
all
variations and/or alternative embodiments within the spirit and scope of the
present invention as defined by the appended claims.
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