Rolls are widely employed in manufacturing and in materials handling to process and/or convey stock material or goods. For example, carrier rolls may be arranged to convey stock material or goods directly, as in a typical roll conveyor or may be arranged to drive a flexible support, such as a belt, web, or screen, which transports the stock material or goods, as in a typical belt conveyor. Nip, press and calendar rolls may be used to squeeze or to control the thickness or movement of a stock material.
In the paper making and non-woven fabric making industries, for example, carrier rolls are employed to transport webs of fibrous stock through the various stages of production and processing. The carrier rolls may be referred to as drive rolls, idler rolls, wire rolls, felt rolls, paper rolls, table rolls, blow rolls, head rolls, tail rolls, etc. In a known Fourdrinier paper making machine, a wire roll is utilized to drive a wire screen. The wire screen transports a fibrous web from a head box to a web transfer station. At the web transfer station, the fibrous web is transferred from the wire screen to a felt carrier. The felt carrier is driven by a felt roll and transports the fibrous web to a web drying station, where one or more dryer felt rolls is typically employed to transport the fibrous web through the drying station.
It is apparent to those skilled in the art that wear of the bearing surfaces on the journals becomes a significant concern. Excessive wear of the bearing surfaces may lead to wear-induced failure of the carrier roll. If failure occurs, then the entire manufacturing or conveying line must be stopped while the roll is removed for service or replacement.
It is essential that most industrial rolls be balanced to within a predetermined residual imbalance value for service. Balancing requires equipment that typically only roll manufacturers would have. Most conventional industrial rolls require rebalancing when a journal is repaired or replaced. This has typically necessitated returning a failed roll to the manufacturer for service. If a spare roll is not immediately available, the line can be incapacitated for days or even weeks awaiting a roll replacement.
Numerous assembly methods have been employed to fabricate the carrier rolls described above and other industrial rolls. One common method has been to fixedly install an axially elongated piece of cylindrical metal stock in each open axial end of a cylindrical metal body and machine an end of the stock which protrudes from the cylindrical metal body into a journal. Another method has been to install a machined journal shaft through an annular metal end head, and mount the end head, with the journal shaft, in an open axial end of the cylindrical metal body. Yet another method has been to assemble a tubular body and a pair of end heads into a roll body and thereafter mount a machined journal to each of the respective end heads. One version of this last method is described in U.S. Pat. No. 4,920,627, assigned to the assignee of the present invention and incorporated by reference herein.
Prior to the above referenced U.S. Pat. No. 4,920,627, rolls were balanced together with their journals as a single assembly without regard to the degree of imbalance of the roll body or the journal components. According to such prior methods, an assembled carrier roll would be supported on its journals and rotated in a dynamic balancing machine to determine the state of imbalance of the roll. Thereafter, conventional steps, such as the removal of metal from or the addition of metal to the roll would be performed to bring roll to within the desired predetermined residual imbalance value.
According to the method of the above referenced U.S. Pat. No. 4,920,627, a carrier roll was constructed by assembling individual, precision pre-balanced journals with a separate, pre-balanced roll body. Damaged journals could thereafter be removed and replaced with other, at least equally prebalanced journals. No further dynamic balancing of the assembled carrier roll was required to bring the roll back to within its prescribed residual imbalance value.
The use of individually prebalanced components as taught by U.S. Pat. No. 4,920,627 permits replacement of the journals without the necessity of rebalancing the entire roll. However, the rolls and methods used to make the rolls disclosed in U.S. Pat. No. 4,920,627 suffer from certain drawbacks. The rolls are more expensive to initially manufacture than conventional rolls by a significant fraction. The disclosed journal members have relatively large head flanges requiring that the journals be machined from constant diameter billets. A great deal of machining was required and a great deal of scrap metal was generated in their manufacture. Also, the flange end faces had to be machined square to the axis of rotation, which is a more difficult and time consuming process than simply symmetrically machining the axially extending circumferential surface of the billet. Also, the various roll components had to be prebalanced individually. The large transverse flanges of the journal members were a potential source of imbalance. Also, the roll bodies had to be prebalanced without their journal members, a more difficult operation than simply balancing a roll body on its journal members.
The rolls of U.S. Pat. No. 4,920,627 also have certain structural limitations. The large head flange tended to act as a stress concentrator in the journal, limiting the loads which the journal could support and thus the types of tube rolls and applications which could beneficially use the design. Also, the large head flange precluded use of the design in small diameter rolls. While the journal members were removable, the use of removal screws could result in damage to the facing surface of the roll body. This could cause a misalignment of the next mounted journal member resulting in a greater than expected or possibly allowed residual imbalance.
The predetermined residual imbalance value to which a carrier roll is balanced during or after assembly may be specified by a user when ordering the carrier roll from a manufacturer. That is, the user may specify permissible residual imbalance of the carrier roll in accordance with his specific needs and/or the conditions under which the carrier roll is to operate. Alternately, if the permissible residual imbalances are not specified, it has been the practice of the industry to balance carrier rolls to within a particular Balance Quality Grade. For example, the practice of the industry has been to prebalance carrier rolls for paper making lines to a G-6.3 residual imbalance value, as defined in Acoustical Society of America Standard 2-75 for "Balance Quality of Rotating Rigid Bodies", incorporated by reference herein. This Standard has been approved by the American National Standards Institute as standard ANSI S2.19-1975, the entirety of which is also incorporated by reference herein.
It would be extremely desirable to provide a design for a method of constructing industrial rolls of the type which require prebalancing and which include removable, replaceable journals in which it is only necessary to assemble the roll and balance the roll once as a single assembly.
It would further be desirable to provide a design and method of industrial roll construction which permit the removal and/or replacement of journal without rebalancing of the roll and which do not suffer from some or all of the drawbacks of the roll design and methods disclosed in U.S. Pat. No. 4,920,627.
It would further be very desirable to provide a design and method of roll construction which enjoy at least the benefits of the roll constructed in accordance with U.S. Pat. No. 4,920,627 and which are less expensive to manufacture than are the rolls of the design of that patent.
It would further be extremely desirable to provide a design and method of constructing rolls with at least the benefits enjoyed by the rolls of U.S. Pat. No. 4,920,627 but having journals of greater strength and smaller overall size for greater applicability and use.
It would further be very desirable to provide a design and method of industrial roll construction which enjoy at least the benefits of the roll design and method of U.S. Pat. No. 4,920,627 but which avoid the necessity of a relatively large head flange and its consequent disadvantages.