Stock material or miscellaneous articles – Hollow or container type article – Paper containing
Patent
1998-09-10
2000-12-12
Crispino, Richard
Stock material or miscellaneous articles
Hollow or container type article
Paper containing
156192, 156195, B32B 108, B65D 304, D21J 304, B31C 500
Patent
active
061595640
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of manufacturing a core, especially a spirally wound core, from superimposed plies of board by winding, glueing, and then drying such.
Webs produced in the paper, plastic and textile industries are usually reeled on cores for rolls. Cores made from board, especially spiral cores, are manufactured by glueing plies of board one on top of the other and by winding them spirally in a special spiral machine. The width, thickness, and number of plies of board needed to form a core vary depending on the dimensions and strength requirements of the core to be manufactured, the ply width being typically 50 to 250 mm, thickness 0.2 to 1.2 mm and the number of plies 3 to 30. The strength of the board ply varies to comply with the strength requirement of the core.
The wall thicknesses of cores will vary within a wide range, being typically 0.50 to 18 mm. The thicker the core wall, the more plies it is composed of. Irrespective of the ply, moisture of the board entering the spiral machine is typically the same, homogeneous, e.g. 8%, which often corresponds to the demand for moisture of the finished core.
As a great number of thin plies are glued together by spreading glue onto large surfaces thereof to make them into a thick core wall, and as the dry matter content of the glue is generally low, about 20 to 60%, the moisture of the board clearly increases at the spiral machine, usually up to 11-18%. Therefore, the produced core has to be dried until it is ready to be delivered to the user.
Drying is effected by blowing mildly heated air through a stack of cores. Drying is laborious and time consuming because the core wall to be dried is thick. A moisture gradient is inevitably formed inside the thick material during drying. In other words, the surface has to dry before the inner parts of the wall can begin to dry. Such a moisture gradient may be several percentage units of moisture per a few millimeters. This is shown, by way of example, in the accompanying graph which indicates a typical moisture profile within a core wall. It is typical of a moisture gradient of known cores that it does not readily become level once it has been formed.
When a ply of board is glued, its fibres swell. During drying of the core, the fibres shrink again as their moisture decreases. For drying, the cores are usually stacked tightly in an overlapping arrangement. Because of the mode of stacking, each core dries mainly internally when air is blown thereto. In the tight stacking, the moisture gradient is formed in one direction, i.e., z-direction, so that the moisture decreases from near the outer periphery of the core towards the inner surface the core wall (cf. FIG.).
Hence, as the core wall has differences in its moisture content and as shrinking occurs at different times during drying, and the latter has an opening effect on the core structure, relatively strong internal stresses are developed in the core wall. Stresses also result from differences in angles of board strips of various plies, according to the geometry of a spiral core. In the worst case, these stresses may even cause material defects. In any case, they weaken the strength of the core when it is under strain, the most typical of such strain being so-called chuck loading (i.e., the roll is supported by a core through relatively short chucks).
The internal stresses of the core may be detected by splitting a thin annulus cut off of the core or by testing cores that have been dried and treated in different manners with a special chuck strength testing device.
It is an object of the present invention to provide a method of decreasing, eliminating or even changing the direction of these stresses, in order to thereby increase the strength and load resistance of a core, especially in case of chuck loading.
In the method of the present invention, the core is manufactured of superimposed plies of board by winding, glueing and drying them, and it is a characteristic feature of the invention that the moisture contents of at least some of the plie
REFERENCES:
patent: 5586963 (1996-12-01), Lennon et al.
patent: 5707328 (1998-01-01), Sato et al.
patent: 6036139 (2000-03-01), Ogg
Andritz-Ahlstrom Oy
Crispino Richard
Koch, III George R.
LandOfFree
Core and a method of manufacturing such does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Core and a method of manufacturing such, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Core and a method of manufacturing such will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-214322