Heat insulating protective shields for two-roll calender with heated rolls

The calender rolls of a calender are provided with heat insulating protective shields which can be laterally pivoted open and with heat insulating end covers or closures at the ends of the rolls. At least one of the rolls is provided with a blower device for generating air flows or jets which can be regulated over the length of such roll to equalize the temperature over the length of this roll.

CROSS-REFERENCE TO RELATED APPLICATION 
This application is related to the commonly assigned, copending U.S. 
application Ser. No. 06/575,010 filed Jan. 30, 1984, entitled "Calender 
for Pressure and Thermal Treatment of Material Webs". 
BACKGROUND OF THE INVENTION 
The present invention broadly relates to roll or calendering devices and, 
more specifically, pertains to a new and improved construction of a 
two-roll calender with heated calender rolls. 
In its more specific aspects the roll or calendering device of the present 
invention relates to a two-roll calender having heated rolls for the 
pressure and thermal treatment of webs or sheet materials of plastic or 
textile or both, such as fiber webs. 
In heretofore known two-roll calenders of this type the heated rolls are 
exposed to room or ambient temperature without heat or thermal insulation 
which leads to significant energy losses. These energy losses have the 
advantage, as far as they are uniform, that they have an equalizing effect 
on the temperature profile of the rolls and therefore guarantee a uniform 
quality of the sheet materials or webs produced, particularly with respect 
to their width. If the above-mentioned heat losses are prevented the 
required uniformity of the temperature profile over the length of the roll 
is no longer guaranteed. 
SUMMARY OF THE INVENTION 
Therefore, with the foregoing in mind it is a primary object of the present 
invention to provide a new and improved construction of a two-roll 
calender with heated rolls which does not have associated with it the 
aforementioned drawbacks and shortcomings of the prior art constructions. 
Another and more specific object of the present invention aims at providing 
a new and improved construction of a two-roll calender with heated rolls 
of the previously mentioned type by means of which a substantial reduction 
in the thermal energy supplied to the rolls can be obtained without 
affecting the required uniformity of the temperature profile over the 
length of the rolls. 
A further object of the invention is to provide a roll or calendering 
device wherein a cooling means acts in a gap or space formed between a 
roll member and a heat insulating protective shield to produce a cooling 
effect on the roll member which is adapted to equalize the temperature 
over the length of such roll member. 
Yet a further significant object of the present invention aims at providing 
a new and improved construction of a two-roll calender with heated rolls 
which is relatively simple in construction and design, extremely 
economical to manufacture, highly reliable in operation, not readily 
subject to breakdown or malfunction and requires a minimum of maintenance 
and servicing. 
Now in order to implement these and still further objects of the invention, 
which will become more readily apparent as the description proceeds, the 
two-roll calender with heated rolls of the present invention is manifested 
by the features that both heated rolls are provided with heat insulating 
protective shields capable of being pivoted away from the related roll and 
with heat insulative end covers at the ends of the related roll. Moreover, 
at least one of the rolls is provided with a cooling device acting in a 
gap or space between such at least one roll and at least one of the heat 
insulating protective shields thereof to produce a cooling effect which 
can be regulated over the length of the roll for substantially equalizing 
the temperature. 
Since the cooling device provided according to the invention only has to 
equalize minimal temperature differences, the use of the heat insulating 
protective shields results in a significant saving of heat or thermal 
energy. 
The cooling device is preferably a blower device for generating air flows 
or jets which can be regulated over the length of the roll. The blower 
device is supplied with air at room or ambient temperature or air which 
has been heated by a suitable heating device. A very simple cooling device 
which is adequate for most cases is obtained by this measure. 
The heat insulating protective shields are preferably pivotably mounted on 
the side of the roll which is located opposite to the contact pressure gap 
or nip. This arrangement provides optimal accessibility to the rolls by 
very simple means when the heat insulating protective shields are pivoted 
away from the rolls. 
The blower device can also be disposed on the side of the roll located 
opposite to the contact pressure gap or nip in a space between two 
pivotable heat insulating protective shields. This arrangement provides a 
long region or path over which the air flows or jets can act on the 
surface of the roll in the gap or space between the roll and the related 
heat insulating protective shield. The blower device is also optimally 
accessible in this arrangement. The heat insulating protective shields can 
be provided with a layer of insulative material as well as a heat 
reflecting foil on the side facing the related roll. This foil is 
preferably easily replaced. 
In a particularly simple embodiment, the blower device can be a housing 
having nozzle apertures or orifices disposed in at least one row and 
closable, individually or in groups, by means of sliding dampers, baffles 
or shutters or the like. It is to be understood that this blower device 
can also contain a longitudinal slot extending in the direction of the 
length of the related roll and whose width at different positions can be 
varied, as required, by any suitable means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Describing now the drawings it is to be understood that to simplify the 
showing of the drawings only enough of the structure of the two-roll 
calender or calendering device has been illustrated therein as is needed 
to enable one skilled in the art to readily understand the underlying 
principles and concepts of this invention. The illustrated exemplary 
embodiment of the two-roll calender will be seen to comprise an upper 
calender roll 1 and a lower calender roll 2. In FIG. 1, the supporting 
framework or roll stand of the rolls has been omitted for reasons of 
clarity. Both calender rolls 1 and 2 are provided with conventional 
heating devices known per se and thus not particularly shown in the 
drawings. With these standard heating devices, the heating rolls 1 and 2 
can be heated to a temperature of approximately 160.degree. C. to 
250.degree. C. In operation, a sheet of material or web 3 of, for example, 
plastic or of textile, for instance a fiber web, that is to be subjected 
to pressure and thermal treatment is entrained and guided between the two 
coacting calender rolls 1 and 2 and fed into or through the contact 
pressure gap or roll nip 5 between these calendar rolls 1 and 2 by 
conventional web feed means, generally indicated in FIG. 1 by reference 
character 40. Both of these calender rolls 1 and 2 are provided with heat 
insulating protective shields 4, each of which contain a layer of 
insulative material as well as a heat reflective foil facing the surface 
of the related roll, for instance aluminum foil, as generally indicated by 
reference character 30. 
As can further be seen from FIG. 1, the heat insulating protective shields 
4 are pivotably mounted in hinges or pivot means 6 on those sides of the 
calender rolls 1, 2 located opposite to the contact pressure gap or nip 5. 
This arrangement permits the heat insulating protective shields 4 to be 
pivoted out of their service or operating position in the direction of the 
arrows 7. 
The lower roll 2 in the calender of FIG. 1 is provided with cooling means 
comprising a blower device 8 which is shown on an enlarged scale in FIG. 
3. As can be also seen in FIG. 1, the blower device 8 can be supplied with 
air by a fan or blower 10 or equivalent structure. The air can be 
conducted through a suitable heating device 11 which can be operated as 
required and through a regulating or control valve 12. 
FIG. 2 shows a partial section of the end zone or region of the upper 
calender roll 1 of FIG. 1. As can be seen from FIG. 2, the calender roll 1 
has, in addition to the heat insulating protective shields 4 acting on its 
circumference, a heat insulating protective end cover 13 at each roll end. 
This end cover 13 is disposed as close as possible to the related lateral 
end face or surface of the calender roll 1 and is provided with the same 
insulative treatment and structure 20 as the heat insulating protective 
shields 4. It is to be understood that both ends of both rolls 1 and 2 are 
provided with such end covers 13. 
According to the showing of FIG. 3 the blower device 8 comprises a housing 
or plenum chamber 14 whose length is relatively great in comparison to its 
other dimensions and whose upper side or wall is provided with nozzle 
apertures or orifices 15 disposed in two rows. These nozzle apertures or 
orifices 15 are adapted to form air flows or jets 15' directed against the 
surface of the corresponding roll, i.e. here the calender roll 2. The 
housing 14 is provided with sliding dampers or shutters 16 or equivalent 
structure for selectively closing and opening the nozzle apertures 15. 
These sliding dampers 16 or the like can, for instance, be adjusted by 
hand according to requirements in service. The nozzle apertures 15 of both 
exemplary depicted rows can be closed or the nozzle apertures 15 of one 
row can be open or the nozzle apertures of both rows can be open. Three 
sliding dampers 16 are represented in FIG. 3 illustrating each of the 
three positions mentioned above. 
When the inventive calender or calendering device is in operation the heat 
insulating protective shields 4 are in the position shown in the drawings. 
This position greatly reduces heat losses for the rolls 1 and 2 to the 
ambient environment except at the processing or operating point in the 
region of the sheet of material or web 4 being processed. Unavoidable 
irregularities of the surface temperature of the calender rolls can be 
compensated by adjustment of the sliding dampers 16 of the blower device 
8. The regulating or control valve 12 regulates the quantity of cooling 
air and the heating device 11 regulates its temperature. The greatest 
cooling effect is obtained when the regulating valve 12 is open and the 
heating device 11 is turned off. Throttling the regulating valve 12 or 
heating the air supply reduces the cooling effect. 
The air flowing into the gap or space 17 between the insulative heat 
shields 4 and the calender roll 2 is directed towards the sheet of 
material or web 3 in whose proximity the gaps or spaces 17 terminate. 
Since the cooling effect is primarily required on that side of the 
calender roll 2 which is turning towards or inbound with respect to the 
contact pressure gap or nip 5, it is advantageous to close the gap or 
space 17 off between the heat insulating protective shield 4 and the 
calender roll 2 on the side of such roll downstream of the contact 
pressure gap or nip 5 by means of a closure strip or fixed baffle 18. The 
air current or flow is then concentrated mainly in the left-hand gap or 
space 17 of FIG. 1, whereby a further advantageous effect of this 
arrangement is achieved. The air warmed in the gap or space 17 and 
directed in the direction of the arrow 20 towards the sheet of material or 
web 3 can be employed to preheat such sheet of material or web 3 
immediately before entering the contact pressure gap or nip 5. This has 
the effect that under otherwise identical conditions a reduced supply of 
heat to the contact pressure gap or nip 5 is required. Thus, for instance, 
the temperature of the calender roll 2 can then be lower which results in 
a further saving of energy. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims. Accordingly,