Sheets for household use are well known in the art. It is often desirable to decorate such sheets, such as by printing. Printing can impart an aesthetically pleasing pattern to the sheet. Alternatively, the sheet may be embossed to impart an aesthetically pleasing pattern which is also tactually discernible.
Such sheets are typically made in continuous form and then later cut to discrete lengths as desired. Such cutting to discrete lengths may occur at the point of use, such as is caused by the consumer detaching one sheet from the balance thereof at a line of termination. For this purpose, the line of termination typically comprises a line of weakness, such as a perforation. Alternatively, the continuous sheet may be cut into discrete portions prior to the point of use. Such arrangement often occurs in individual napkins or facial tissues that are cut during manufacture and purchased by the consumer as discrete units.
It has been relatively facile in the prior art to register indicia with a cross-machine direction of such sheets while such sheets are transported in a continuous fashion during manufacturing. However, it is difficult to register the indicia in the machine direction and particularly difficult to register the indicia with lines of termination of such sheet materials.
One manner in which the foregoing difficulties have been addressed is to keep the length of the sheet material disposed between application of the indicia and the deposition of lines of weakness therein relatively short. However, this approach does not provide for feasibility in manufacturing processes, can require smaller sized equipment, and is infeasible where any modules necessary to impart such lines of weakness, or for the application of the indicia, provide a web path that is large enough to cause improper spacing between the indicia and the lines of weakness.
Other processes may provide acceptable results with regard to processing of a single type of web material, such as short sheets, but not work acceptably where longer sheet lengths are required. For example, one approach provides for a relatively short path length between the point at which the latter of the indicia and/or lines of termination are applied or imparted to the sheet and the point at which the continuous sheet is cut into separate discrete units at the point of manufacture. However, where relatively longer sheet lengths are required (i.e., rolled products, such as toilet tissue or paper toweling), difficulties are introduced by the cumulative error that occurs over the length of the continuous sheet. For example, a misregistration of 0.001 inches at the first repeat unit will provide a misregistration of 1 inch after the manufacture of 1,000 inches of sheet material.
The processes of the prior art provide for even larger problems when a parent roll being processed is exhausted and a new parent roll is started. A parent roll is a large roll of product that is later converted to multiple individual sheets by the apparatus and process disclosed herein. It should be known to those of skill in the art that different parent rolls have different properties which can affect the transport of the sheet through a manufacturing apparatus. By way of example, the amount of stretch in the sheet material as it travels through the apparatus frequently varies greatly between different parent rolls. As these properties vary, so does the registration of the indicia with the lines of termination. Such variations in registration must be accounted for in the manufacturing process.
Accordingly, it should be apparent to those of skill in the art that the approaches that may be feasible when dealing with longer sheet lengths are not sufficient for dealing with registration difficulties that occur in shorter sheet lengths and vice versa. Thus, it would be useful to provide a mechanism for overcoming these problems associated with misregistration between indicia and lines of termination in products having longer unit lengths and, in particular, core wound paper products and yet be flexible enough to deal with discrete articles of relatively short unit length. Additionally, it would be useful to provide for adjustments to the spacing between indicia and lines of termination while the sheet is being processed into consumer goods.