A calender and method of operating the same, where the calender has a vertical stack of a plurality of rotary rolls, each of the rolls having bearing structure at each opposite end provided with a thrust shoulder cooperative with a stop shoulder on a respective suspension spindle at each end of the rolls. There are guideways for the bearing structures, and there is an arrangement for vertically shifting the rolls between a lowered mode for spaced apart independent suspension by stop shoulders and a raised nipping mode relation with one another. The weight of the bearing structures of the rolls in the raised nipping mode relation is relieved as by cooperating pawl and rack structure.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to supercalenders of the type wherein the 
rolls are adapted for limited separation from one another in one mode and 
are in calendering nipping engagement with one another in another mode. 
2. Description of the Prior Art 
Supercalenders with which the present invention is concerned are well known 
in the art and comprise a substantial stack of calender rolls wherein 
separation of the rolls may be controlled either from the top or the 
bottom of the stack. Where control is from the bottom of the stack, a king 
roll at the bottom of the stack is moveable between a lowered position and 
a raised position. In the lowered position of the king roll, a substantial 
number of calender rolls thereabove separate from one another to provide 
gaps therebetween to facilitate threading a new web of material through 
the stack or to relieve any damaging effect of broke or creased web 
passing through the roll nips. As thus gapped, the opposite ends of the 
rolls are supported by their bearing structures on shoulders along upright 
suspension spindles at the opposite sides of the stack. In the calendering 
mode of the stack, the king roll acting through the next adjacent 
calendering roll pushes all of the rolls thereabove into nipping relation, 
wherein the bearing structures for the rolls are lifted from the spindle 
shoulders. For uniform nip loading, the topmost roll in the stack may be 
hydraulically biased downwardly. Calenders of the type just described are 
represented in U.S. Pat. Nos. 3,364,848, 3,369,483, 4,290,351 and 
4,311,091. 
Inasmuch as the calender rolls are quite heavy, such, for instance as about 
42,000 pounds each in a supercalender, their bearing structures must be 
fairly massive to afford adequate support when the rolls are individually 
supported on the spindles. Typically each bearing structure at each end of 
each of the rolls may weigh from 4,000 to 5,000 pounds. Therefore, when 
the rolls are lifted to the nipping, calendering mode, and the bearing 
structures are in deadweight relation at each end of each roll, the 
deadweight end loads on the rolls tend to distort the rolls and thus 
distort nips between rolls from the ideal straight line. This distortion 
or warping condition is aggravated where, as is often desirable, fly rolls 
(i.e. guide rolls) are supported on the housings of the bearing 
structures. 
SUMMARY OF THE INVENTION 
It is to the alleviation of the distortion of the roll nips due to 
deadweight of the bearing structures that the present invention is 
directed. 
To this end, the present invention provides a method of operating a 
calender having a vertical stack of a plurality of rotary rolls, each of 
the rolls having bearing structure at each opposite end, means for guiding 
the bearing structures for vertical movement, and means for vertically 
shifting the rolls between a spaced apart independent suspension mode and 
a nipping mode relation with one another and comprising relieving the 
weight of the bearing structures of the rolls in the nipping mode relation 
of the rolls by operating lifting pawls in cooperation with associated 
racks. 
For practicing the method, the present invention provides a calender having 
a vertical stack of a plurality of rotary rolls, each of the rolls having 
bearing structure at each opposite end means for guiding the bearing 
structures for vertical movement, and means for vertically shifting the 
rolls between a spaced apart independent suspension mode and a nipping 
mode relation with one another, and comprising means including lifting 
pawls which cooperate with associated racks for relieving the weight of 
the bearing structures from the rolls in the nipping mode relation, and 
means for operating the relieving means.

DETAILED DESCRIPTION 
Referring to FIGS. 1 and 2, one side of a supercalender is depicted wherein 
a vertical stack of calender rolls 10 is supported in respect to a 
supporting frame 11. Only one side of the calender is depicted, and it 
will be understood that the opposite side will be substantially mirror 
image of the illustrated side, and the description will assume such 
substantial similarity of both sides, and thus the substantial similarity 
of the structures involved at each opposite end of each of the calender 
rolls in the stack 10. 
The calender stack 10 comprises a lowermost king roll 12 and thereabove a 
series of filled (i.e. composed of a core supporting a concentric pack of 
cotton, paper or fibrous disks) rolls 13, and cast iron rolls 14 which, in 
general are alternated in the stack, except near the center of the stack 
where a pair of the filled rolls 13 have nipping relation with one another 
so that a web W being calendered will be exposed to the smoothing action 
of these filled rolls on both sides. At the top of the stack a head roll 
15 (FIG. 1) bears downwardly on the stack of rolls in the calendering mode 
for attaining substantially uniform nipping pressure between all of the 
rolls in the stack. 
Although in some calenders the topmost roll serves not only as a pressure 
roll but also as a lifting roll by which all of the rolls except the 
lowermost roll are lifted into nip separating relation, the preferred 
arrangement shown in FIGS. 1 and 2, has the lower or king roll 12 in 
control of both the calendering mode as shown in FIG. 1 and the open roll 
mode shown in FIG. 2. For this purpose supporting bearing means 17 at each 
end of the king roll 12 have associated therewith upwardly thrusting 
hydraulic plungers 18 of hydraulic cylinders 19 adapted to thrust the king 
roll 12 upwardly as shown by directional arrow FIG. 1 for the calendering 
mode, and to drop the king roll 12 rapidly for the open roll mode as shown 
in FIG. 2. On the other hand, the top roll 15 has its bearing structures 
20 at each opposite end adapted to be thrust downwardly by means a 
respective hydraulic actuator piston plunger 21 having its hydraulic 
cylinder 22 mounted on the frame 11 in each instance. The actuators 22 are 
adapted to be activated after the hydraulic actuators 19 have raised the 
king roll 12 into the calendering mode for attaining the desired 
substantial uniformity of calendering load on the stack. As shown in FIG. 
2, in the open roll mode the actuators 22 are inactivated. 
For guiding all of the rolls in the stack 10 for vertical movement along 
the supporting structure frame 11 a vertical rail 23 is provided which 
extends the full length from top to bottom of the stack and is adapted for 
slidable tracking engagement with the housings of the bearings of the 
several rolls. Each of the rolls 13 and 14 has a similar bearing structure 
24. All of the bearing housings for all of the bearing structures 24 and 
the bearing structures 17 and 20 may be slidably engaged with the rail 23 
as typically illustrated in FIG. 3. The rail 23 is secured to the frame 11 
as by means of bolts 25 at suitable intervals therealong. Bearing housing 
27 has vertical bearing surfaces 27a in tracking engagement with the rail 
23 in cooperation with retainer plates 28 secured to the housing 27 by 
means of bolts 29. Roller bearings 30 support the associated journal 31 of 
the calender roll on the bearing housing 27 which is of a mass and 
durability suitable for the purpose. 
Each of the bearing housings 27 for each of the bearing structures 20 and 
24 has an integral yoke 32 within which the shank of a threaded screw 
spindle 33 is received, the yoke providing a thrust shoulder facing toward 
and engageable with an underlying supporting stop shoulder 34 in the form 
of a stop nut threadedly engaged on the spindle 33 and readily adjustable 
therealong. Each of the stop nuts 34 is adapted to be adjusted to attain 
the desired spacing between its associated roll and the contiguous rolls. 
In a preferred relationship, such spacing may be progressively greater 
from the uppermost roll nip to the lowermost roll nip. For example, at the 
uppermost nip the spacing may be about one-half inch, and the spacing of 
each successive nip downwardly in the stack may increase by about 0.2 inch 
increment so that in a stack having the number of rolls shown the 
lowermost nip spacing in the open condition of the rolls may be about 2.1 
inch. This facilitate threading or any other web condition or event, where 
the web travels upwardly through the calender. Each of the spindles 33 is 
thoroughly anchored at the top of the frame 11. 
Even though the bearing structures 20 and 24 may be heavy enough in and of 
themselves to cause a nip distortion by reason of their deadweight in the 
closed nipping roll mode as depicted in FIG. 1, the problem is aggravated 
where it may be preferred to mount fly roller assemblies 35 on the 
housings 27 of the bearing structures for each of the rolls above the king 
roll 12. Such mounting of the fly rollers 35 (also sometimes referred to 
as guide rollers) is desirable because thereby the fly rollers remain in 
the most desirable alignment with respect to the associated calender roll 
in each instance, and when the rolls in the stack are rapidly dropped to 
open the nips, there is minimum, if any, distorting tension of the web W. 
According to the present invention, the weight of the bearing structures 20 
and 24 is relieved from the rolls 13, 14 and 15 in the raised nipping mode 
relation of the calender rolls, that is, the mode illustrated in FIG. 1. 
This is effected, for example, by means illustrated in FIGS. 3-7, 
including rack means 37 conveniently in the form of an elongate rack bar 
associated with each of the track members 23 and selectively engageable by 
a pawl 38 carried by the bearing housing 27. As indicated hereinabove, 
this arrangement prevails with equal effect at each side of the calender 
stack, and more particularly at each of the ends of the calender rolls. 
The arrangement is such that when the king roll 12 raises the calender 
rolls thereabove into their nipping, calendering relation, the rack bar 37 
is engaged by the pawl 38 as shown in dot dash outline in FIG. 5. By the 
coupling thus provided the deadweight load of the associated bearing 
structure is relieved from the associated end of the calender roll. When 
the calender rolls are dropped to provide gaps at their nips, in the mode 
illustrated in FIG. 2, and the weight of the calender rolls is supported 
through their bearing structures on the shoulders 34, the pawls 38 are 
adapted to freely disengage from the rack bars 37. 
In a desirable arrangement, each of the rack bars 37 is slidably mounted in 
a complementary vertical recess 39 in the associated track member 23 and 
which is deep enough to receive the rack bar with rack teeth 40 thereof 
about flush with the outer face of the track member 23, as best visualized 
in FIGS. 3 and 7. Retainer strips 41 mounted in offset grooves 42 at the 
outer sides of the recess 39 and retained in overlapping retaining 
relation to lateral shoulders 42 extending longitudinally on the rack bar 
37 inwardly alongside the rack teeth 40, are secured in place by means of 
screws 44. Through this arrangement, the rack bars 37 are retained in 
thoroughly backed up relation to the associated track members 23 and are 
permitted to slide vertically in their retaining recesses 39. At their 
lower ends, the rack bars 37 are adapted to thrust at each side of the 
calender stack against a stop shoulder 45 (FIG. 1) provided by the 
uppermost of a pair of vertically spaced runner bosses 45 integral with 
the housing of the bearing structure 17 of the king roll 12. These runner 
bosses 45 are in engagement with the track member 23 in similar fashion as 
shown in FIG. 3 for the bearing structure housing 27. As a result, when 
the king roll 12 is raised, the rack bars 37 are shifted upwardly in their 
track recess 39. When the king roll 12 is dropped, the rack bars 37 
follow, at least by gravitational bias, their associated shoulder bosses 
45 and descend therewith as guided in their tracks recesses. 
Means are provided for controlling the pawls 38 individually in a manner to 
assure that the pawls will engage the rack teeth in each instance only 
when the calender roll system is ready for the deadweight relief function 
of the pawl and rack structure. To this end, each of the pawls 38 is 
carried by the lower end portion of a piston rod 47 of a rectilinear 
hydraulic actuator 48 mounted in vertical position to the bearing housing 
27 in each instance. At its upper end portion, the pawl 38 is pivotally 
attached to the piston rod or plunger 47 by means of an ear 50 (FIGS. 5-7) 
which projects upwardly into a clevis 51 carried by the piston rod 47, 
with a sturdy pivot pin 52 effecting a pivotal connection so that the pawl 
38 is adapted to swing into and out of ratcheting engagement with the 
teeth 40 of the rack 37. Such ratcheting engagement is facilitated by 
means of a finger 53 on the pawl complementary in shape to recesses 54 
between the rack teeth 40 each of which provides an upwardly facing 
shoulder as shown. In the non-operating mode of the pawl 38, the actuator 
48 draws the pawl upwardly into a raised position wherein a shoulder 55 on 
the upper end of the pawl at the side which is nearest the rack 37 engages 
a downwardly facing stop member 57 which may conveniently be carried by 
the lower face of the head of the actuator 48. Thereby the pawl 38 is 
positively swung toward the adjacent face of the housing 27 and is held in 
a position where the pawl finger 53 is clear of the rack teeth 40. In this 
retracted, inactive position of the pawl 38, an upwardly facing shoulder 
58 on the upper end of the pawl, and at the opposite side of the pivot 52 
from the shoulder 55, engages biasing means comprising a spring 59 which 
is compressed by the shoulder 58. Hydraulic fluid for operating the 
actuator 48 is delivered to opposite ends of its piston 60 through an 
upper inlet 61 and a lower inlet 62 (FIG. 5) to which respective 
alternating hydraulic pressure/relief conduits 63 and 64 are connected. 
Operation of the hydraulic actuators 48 is coordinated with operation of 
the hydraulic actuators 19 for the king roll 12 and the actuators 22 for 
the top or head roll 50. When the king roll drops to open the calender 
rolls, the pawl actuators 48 retract the pawls. When the king roll has 
raised the calender rolls into nipping calendering relation, and the upper 
pressure roll 15 is activated to place calendering load on the stack, the 
pawl actuators 48 are operated to drive the pawls 38 downwardly. As the 
pawl shoulders 55 leave the stops 57, the biasing springs 59 swing the 
pawls 38 toward the associated racks 37 so that the pawl fingers 53 will 
engage with one of the teeth 40 of the rack. Then by continuing thrust 
applied by the actuators 48 to the associated pawls 38, a corresponding 
upward lifting force is applied to the associated bearing structures for 
relieving the deadload of the bearing structures from the associated 
calender rolls. This relieves the calender rolls from the distorting 
effect of the bearing structure and associated fly roll dead weight so 
that the rolls will maintain substantially uniformly straight calendering 
nips. 
In order to avoid malfunction should any of the pawls 38 not retract 
properly when the calender roll stack is dropped, safety means comprising 
a proximity switch 65 (FIG. 5) is provided for each of the pawls 38 to 
monitor its retracting performance. If any of the pawls 38 does not 
properly retract, then this will be signalled at a control station, and 
the malfunction may be traced. This safety feature avoids the possibility 
that any pawl may remain in engagement with the rack 37 in the separated 
roll mode, whereby on lifting of the stack toward the calendering, nipping 
mode the entire weight of the associated roll might be imposed through the 
malfunctioning pawl onto the associated rack 37. Overburdening and 
possibly destructive imposition of weight on the rack 37 is thus avoided. 
It will be understood that variations and modifications may be effected 
without departing from the spirit and scope of the novel concepts of this 
invention.