Composite roll shell

A controlled deflection roll for forming a press with an opposed roll including an elongate tubular roll shell, an elongate support shaft extending longitudinally through the roll shell, and a fluid operated controllable load support means between the shaft and the shell, such as a piston with an open pressure hydrostatic oil interface facing the shell. The roll shell is constructed of a fabricated fiber reinforced matrix, and is comprised of a plurality of annular layers of fiber and matrix composite, so that the shell is of relatively light weight and has a reduced cross-machine bending stiffness.

BACKGROUND OF THE INVENTION 
The invention relates to controlled deflection rolls of the type used in a 
papermaking machine press for forming a press nip with an opposed roll. 
In a conventional press of the type used in a papermaking machine for 
dewatering a traveling web, two or more press rolls are pressed together 
with the requirement that they produce a substantially uniform line of nip 
load across the length of their contact. 
The line load, also referred to as nip pressure, is generally measured in 
pounds per inch of width and will not be entirely uniform with plain rolls 
due to differences in the deflection of the rolls under different applied 
loads. Plain press rolls can be contoured or crowned to compensate for the 
deflection at a specific load, but the resulting nip pressure will not be 
uniform along the nip for other loadings. 
A solution to this problem for obtaining uniform nip pressure at varying 
nip loads is the use of controlled deflection rolls. Sometimes, this type 
of roll is referred to as a controlled crown, or CC, roll. In these rolls, 
the nip pressure profile can be adjusted by increasing or decreasing the 
pressure applied to the shell from inside the roll. The structure of such 
a roll involves a roll shell supported on a central shaft extending 
co-axially therethrough with a fluid-controllable, load-supporting means 
between the shaft and the roll shell opposite the nip line. Various 
nip-loading devices have been employed for loading the nip by transferring 
the forces to the inner surface of the roll shell from the shaft. These 
arrangements provide for loading the nip and, in certain circumstances, 
for controlling the load along the length of the nip so that an adjustable 
crown can be obtained, that is, either a uniform nip or a controlled nip. 
In one form, the support pressure applied to the nip is accomplished by an 
oil lubricated shoe wherein the pressure of the oil and the force on the 
shoe opposite the nip can be controlled or adjusted. With this type of 
construction, the shell is typically formed of heavy cast metal and 
machined to the required dimensions and surface smoothness inside and out. 
The amount of mass which makes up the complete controlled deflection roll, 
including the cast roll shell, shoe and shaft plus the loading arms, 
influences nip vibration. In some constructions, the roll shell is covered 
with a synthetic cover, and these vibrations will cause corrugations in 
the roll cover, as well as in the felt which is passed through the nip 
with the web. Most corrugation and roll bouncing problems are related to 
the recovery time of the roll cover elastomer. 
One partial solution to the problem is to mount anti-friction bearings, 
which support the roll shell, to a carrier ring which is slidably or 
pivotally mounted to the center shaft. The nip loading shoe is then used 
to raise the roll shell into contact with the mating roll. Such a 
construction reduces the total vibrating weight, but it also lowers the 
natural frequency of the roll, which is undesirable. 
The nip-loading shoe has been used to raise the shell into contact with the 
mating roll and, in this arrangement, the center shaft and mounting do not 
participate in nip vibrations because they are not mechanically linked 
with the roll shell when the roll shell is moved radially in the direction 
of the nip. This reduces the inertial mass load on the press nip. Because 
the bearings are mounted on a movable carrier, or bearing ring, and are, 
therefore, not directly supported on the center shaft, opposing end shoes 
must be added to reduce the bending moment needed to change the contour of 
the nip profile. These counter-shoes add additional rotational resistance 
to the shell. Because the shoes are located closer to the roll center than 
the rotational bearings in a conventional controlled crown roll, the 
bending moment is reduced, thus limiting the crown control. Further, the 
massive shell is still able to cause some damage to the felts and to roll 
covers due to its own mass, which affects nip loads during nip vibrations. 
It is accordingly an object of the invention to provide an improved 
controlled crown roll structure which avoids disadvantages of structures 
heretofore available. 
A further object of the invention is to provide an improved roll shell for 
a controlled crown roll construction wherein the mass is greatly reduced 
to reduce the problems of nip vibrations and other consequent 
disadvantages of operation. 
A still further object of the invention is to provide an improved 
controlled crown roll with a unique shell construction wherein the shell 
weight will be substantially less than with conventional cast metal shells 
and wherein the shell thickness is reduced and cross-machine stiffness 
reduced. 
FEATURES OF THE INVENTION 
In accordance with the principles of the invention, a controlled crown roll 
is provided with a center shaft and supporting liquid pressure crown 
control supports, such as hydraulically actuated shoes. The roll shell is 
formed of a fiber-reinforced resin. The shell, in the construction 
provided, will have about 20% of the weight of a conventional cast metal 
shell of the same dimensions and can be less than about 10% of the weight 
of a conventional cast metal roll shell if the shell thickness is reduced. 
The reduced thickness is possible because the shell stresses are 
predominantly compressive stresses. The reduced mass will greatly reduce 
the potential for the press nip to damage felts and roll covers. 
The roll shell is comprised of inner, intermediate and outer layers. Each 
layer is formed of a composite of a matrix and fibers. The matrix is a 
chemically inert, glue-like structure which holds the fibers together in a 
desired location and orientation, and transfers the load from fiber to 
fiber. The matrix also protects the fibers from damage due to elevated 
temperatures and humidity. 
Regarding the three layers, the inner layer is comprised of high abrasion 
resistant fiber, preferably randomly orientated, and a high temperature 
resistant, fluid impermeable matrix. The inner surface of the inner layer 
is comprised mostly, or entirely, of matrix so as to better protect and 
support the fibers from loss of lubrication, liquids, such as oil 
contaminants, stress and shear. 
The intermediate layer has its fibers oriented to be aligned substantially 
circumferentially to provide maximum hoop strength. 
The outer layer is a composite comprised of a matrix in which fibers are 
randomly oriented. Examples of the preferred matrix, particularly for the 
outer layer, are epoxy, polyester, phenolics, polyamids, and 
bisnalaimides. Preferred fibers for the outer layer include aramids, 
ceramic, glass, graphite, para-aramids and meta-aramids. 
The matrix is selected for high impact strength and fracture resistance. 
This guards against the potential of the roll's surface being either 
dented or shattered, both of which would be deleterious to the roll's 
operation in a papermaking machine. 
Examples of preferred, high strength and modulus, high abrasion resistance 
fiber include aramids, ceramic, glass, graphite, para- and meta-aramids. 
Examples of preferred impermeable, high temperature matrices include 
toughened epoxies, urethane, thermoplastic, PEEK (Poly Ether Ether 
Ketone), PPS (Poly Phenylene Sulfide) and nylon, for example. Such high 
strength and abrasion resistant fibers and high temperature, impermeable 
matrices are preferred for use in the inner layer where sliding friction 
with the hydraulically actuated shoes, and exposure to hydraulic oil 
contaminants, would be expected to be encountered during operation. 
Other objects, advantages and features will become more apparent, as will 
equivalent structures which are intended to be covered herein, with the 
teaching of the principles of the invention in connection with the 
disclosure of the preferred embodiments thereof in the specification, 
claims and drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As illustrated in FIGS. 1 and 2, a controlled deflection roll press 
assembly includes an upper, mating press roll 11 which is rotatably 
mounted on a shaft supported in bearings 12 and 13. 
A lower, controlled deflection roll 10 forms a nip with the upper press 
roll. The position of the rolls may in some instances be reversed with the 
controlled deflection roll 10 being above the mating roll 11. 
The controlled deflection roll includes a rotatable shell 14 with a 
supporting shaft 15 extending axially therethrough. The supporting shaft 
is non-rotatable but is supported in framework 19,20 by spherical bushings 
17,18 to permit bending of the roll 10, and deflection of the support 
shaft, as it carries the load of applying forces to the nip N between 
press rolls 10,11. 
The nip load is controlled by fluid pressure control means, such as pistons 
16 between the roll shell and the shaft 15, which exert an upward force to 
control the forces in the nip. To an extent, the contour of the nip can 
also be controlled by this means. At the ends of the roll shell are 
bearings, shown at 21 at one end with a similar bearing at the opposite 
end. These bearings maintain the ends of the roll shell in alignment with 
the shaft and with the nip N. 
To ensure that the ends of the roll are maintained in alignment with both 
the nip and the support center shaft, the bearings at each end of the roll 
are mounted to a bearing ring 24 which, in turn, is pivotally attached to 
the center shaft 15 with a pivot pin 9 which is mounted in a pillow block 
25. In FIG. 2, the bearing ring is shown broken away for clarity. Each 
side of the center shaft 15 has a flat surface 22,23, which surfaces are 
parallel, to facilitate mounting the pillow block 25 at each end of the 
shaft. On the side of the shaft at each end of the shaft opposite the 
pillow blocks is a U-shaped guide 25' which engages the bearing ring 24 to 
guide it in its pivoting path of travel and to provide axial thrust 
support. 
While various forms of nip loading support means may be provided for 
loading the nip, that is applying a nip loading force to the inner surface 
of the roll shell 14, one form is shown by a series of hydraulically 
actuated, hydrostatic shoes 32 arranged at spaced intervals longitudinally 
on the support shaft in a cross-machine direction and supported on the 
shaft 15. The shoes may be uniformly loaded or differentially loaded, 
depending upon the nip contour loading desired. 
Nip loading hydraulic pressure is provided by a hydraulic pump, not shown, 
which supplies hydraulic fluid, such as oil, through a single center core 
passage 26, FIG. 3, in the shaft 15, or alternatively, through a series of 
hydraulic passages, not shown. The center passage 26 has vertically 
extending individual riser passages 27 which lead to a cylinder chamber 28 
beneath the base of each of the pistons 32. These pistons 32 are sometimes 
referred to as shoes in the papermaking industry. The hydraulic fluid 
pressure in the chamber 28 urges the shoe 32 upwardly to support the load 
and, to ensure constant lubrication and hydrostatic fluid support, the 
hydraulic fluid, under pressure, is channeled upwardly through passages 
29, sometimes called capillary tubes, in the piston into pockets 30,31 in 
the shoe 32 surface facing the inner surface of the roll shell 14. 
In some instances, counter-load shoes 34 may be provided. One of the 
functions of these shoes is to raise the roll shell when the shell is 
mounted in an inverted position, that is, when the controlled deflection 
roll is above the plain roll. Other passages 33 lead from the center core 
passages 26 to a chamber 28a beneath the piston 34a and passages 35 
through the piston open into lubrication pockets 36,37 in the face of the 
shoe 34 facing the inner surface of the roll shell. The fluid transmitted 
to the pistons 34a is controllable so that it can be used to raise the 
roll shell and, if used during operation, the pressure is controllable so 
that the nip loading shoes 32 can perform their function of loading the 
nip and provide an appropriate nip pressure profile. 
The controlled deflection roll shell 14, as shown in FIGS. 3 and 4, is 
constructed of a lightweight matrix and fiber composite, preferably 
multi-layered with concentric annular layers. The roll shell is comprised 
of a fiber-reinforced matrix, such as epoxy, for example, which will have 
a total weight of only 20% of the weight of a conventional controlled 
deflection roll shell of the same thickness, but made of steel. Actually, 
the weight can be less than 10% of the weight of a normal steel shell if 
the shell thickness is reduced to a minimum required for mechanical 
stability. The reduced shell thickness is possible because the shell 
stresses are predominantly compressive stresses and the composite shell 
can readily tolerate compressive stresses. The reduced mass will greatly 
reduce the potential for press nip damage to the felts and roll cover. 
The shell is manufactured with reinforcing fibers 40 in an intermediate 
layer, and these reinforcing embedded fibers are oriented in the 
circumferential direction, as shown in FIG. 4. This does not add to the 
cross-machine direction bending stiffness of the shell, but it still 
increases the hoop stiffness of the shell. This allows the shell to bend 
more easily and might eliminate the need for counter-acting shoe loadings 
near the ends of the roll shell. The high hoop stiffness maintains an 
essentially cylindrical roll shell shape. 
Another advantage of this shell construction is the ease of balancing. The 
shell can be manufactured on a precision smooth mandrel. This eliminates 
the need to bore the shell. Further, a lower mass results in lower 
potential imbalance forces. 
The composite shell has a naturally higher vibration dampening coefficient. 
Proper selection of matrices and fibers will provide a chemically inert, 
wear-resistant, impact-resistant, impermeable shell. Due to inherent 
structural properties of the matrices (e.g. the ability to transfer 
stresses between fibers and to provide abrasion resistance), and the 
fibers (e.g. the ability to provide tensile strength, and to distribute 
load) in the composites, fatigue failures would not be catastrophic. 
Fatigue failures will manifest themselves in typically slowly progressive 
failures. 
The composite roll shell has an inner layer 39 of a high abrasion-resistant 
fiber and a high-temperature, impermeable composite matrix. This inner 
layer construction is used to minimize shell damage due to oil 
contaminants or temporary loss of lubrication. Preferred matrix materials 
for construction of the inner layer are toughened epoxies, urethane, 
thermoplastic, PEEK, PPS and nylon. Preferred fibers for the inner layer 
are aramids, ceramic, glass, graphite, para- and meta-aramids. It is 
preferred to have the inner surface of the inner layer comprised of a 
matrix material with no fiber material, or very little fiber material 
exposed. 
The center core layer 40 (i.e. the intermediate layer) of the composite 
shell is comprised of a high strength fiber. This fiber is wound on the 
inner surface layer with the fibers predominantly oriented in a 
circumferential direction. This construction develops a high shell 
stiffness to prevent the shell from distorting out of the circular shape 
while providing low resistance to roll bending so that the crown or 
deflection of the roll shell can be easily controlled. Preferred fibers 
for the center core, or intermediate, layer include aramids, ceramic, 
glass, graphite, para-aramids and meta-aramids. Preferred matrices for the 
center core, or intermediate, layer include toughened epoxies, urethane, 
thermoplastic, PEEK (Poly Ether Ether Ketone), PPS (Poly Phenylene 
Sulfide) and nylon. 
The outer layer 38 of the composite shell comprises a composite of fibers 
and matrix which provide impact resistance, wear resistance, and a surface 
which can be routinely ground to maintain the outer surface crown profile. 
Preferred matrices for the outer layer include toughened epoxies, 
urethane, thermoplastic, PEEK (Poly Ether Ether Ketone), PPS (Poly 
Phenylene Sulfide) and nylon. Other matrix materials which are useful and 
preferred for use in the outer layer are epoxies, polyesters, phenolics, 
polyamids and bisnalaimides. Preferred fibers for the outer layer include 
aramids, ceramic, glass, graphite, para-aramids and meta-aramids. 
In operation, the nip is closed and a web to be pressed is threaded through 
the nip N. The shoes are loaded with oil pressure to maintain the desired 
nip load. The nip loading shoes can be divided or further segmented or 
controlled as to hydraulic fluid pressure supplied thereto in the 
cross-machine direction to allow adjustability to the nip pressure 
profile. The roll shell is rotated at a relatively high speed to 
accommodate present high speed papermaking machines when the nip is 
utilized in a dewatering section of a paper machine. The relatively 
lightweight roll shell is capable of a long operating life and has a 
relatively low bending stiffness in the cross-machine direction. Because 
the layers of the shell are chosen to provide a high abrasion resistant 
composite on the inner surface which also has high temperature resistance, 
the shell damage due to oil contaminants or temporary loss of lubrication 
is minimized. With the high hoop strength of the shell, the shell is 
capable of a long operating life providing an improved function, as well 
as obtaining a shell which is manufactured without the necessity of 
providing huge molding facilities and huge machining facilities, such as 
are necessary with a cast steel shell. Where the steel shell must have an 
exterior coating of rubber or high release material, the resin which is 
chosen for the outer surface of the shell can have these features without 
an additional coating layer, or alternatively, be selected for improved 
bonding to said coating or material. 
Thus, it will be seen there has been provided an improved controlled 
deflection roll which meets the objectives and advantages above set forth.