1. Field of the invention
The present invention relates to paper-making machines, and, more particularly, to rolls for use in paper-making machines.
2. Description of the related Art
A paper-making machine is used to form a fiber web, such as a paper web, from a prepared fiber suspension. Typically, the fiber suspension is discharged from a head box onto an endless belt such as a forming fabric with a known cross-sectional profile. A plurality of rolls carry the fiber web from one end of the paper-making machine to the other. The rolls may either directly carry the fiber web, or may indirectly carry the fiber web on an endless belt.
It is known to form a roll in a paper-making machine with a shell which is formed from a composite material. For example, U.S. patent application Ser. No. 09/512,940, entitled "ROLL FOR PAPER-MAKING MACHINE", assigned to the assignee of the present of the invention, discloses a shell for a roll which is formed from a carbon fiber composite material. Such a roll has the advantages of being light weight and having a relatively low rotational inertia.
With a roll having a composite fiber shell as described above, the shell is typically mounted to a metal head, which in turn is mounted to or integral with a journal carried by bearing assemblies at opposite ends of the roll. Although such a composite fiber roll is a step forward in the art, the metal head is relatively heavy and causes the roll to have a high rotational inertia, which may be undesirable for certain applications. More particularly, a roll may rotate during operation within a paper-making machine at a tangential velocity of approximately 7000 feet per minute. Although the composite fiber shell is relatively light weight, the metal head and. metal journal at each end of the roll cause the roll to have a relatively high rotational inertia.
Moreover, the composite fiber shell has a coefficient of thermal expansion which is typically much less than the coefficient of thermal expansion of the metal head which interconnects the shell with the journal. This results in an expansion differential between the shell and head in the longitudinal direction, which may affect the attachment therebetween. Moreover, thermal stresses may be induced within the shell and/or head, depending upon the temperature expansion differential and the particular attachment technique used therebetween.
What is needed in the art is a roll for a paper-making machine which is light weight, has a low rotational inertia, and is relatively stable when subject to thermal expansions and contractions.