Paper roll header

Abstract: A header (28) having a first waterproof polymeric coating (30) over its inner face, the coating being a thermoplastic which is heat softenable at a predetermined elevated temperature for bonding to the crimped end (14′) of a wrapper (14) around the paper roll (10), and a second coating (28a) on the first coating on the inner face of the header, the second coating being in the central zone of the inner face and being non-softenable at the noted predetermined elevated temperature, so that the header sealingly bonds to the wrapper but not to the end of the roll itself.

Description: This invention relates to paper roll headers. In the paper manufacturing industry, the ends of large wound rolls of paper stock are typically protected by an outer wrapping around the periphery crimped over the annular edges, plus end plates known as headers. These headers may be formed of various materials, but typically include an inner header which is not waterproof and abuts an end of the roll with the wrapper crimped thereover, and an outer header which is waterproof and is sealed to the inner header and to the crimped wrapper ends. Each outer header is coated with a thermoplastic polymer, enabling it to be heat sealed to the peripheral wrapper and inner header to prevent moisture from penetrating the ends of the rolled paper. The assembly of these components is preferably largely accomplished by machinery. Thus, the headers can be picked off a stack by a vacuum, i.e., suction, unit. Since the inner header is porous, the vacuum head unfortunately tends to pick up more than one at a time. If no inner header is employed, the outer header tends to bond to the paper as well as the crimped wrapper. This damages the paper. One solution to this problem is described in US-A-2 803 935 in which a paper header has applied only to the margin of the header a coating having a thermoplastic character to be heat-softenable for bonding at a predetermined elevated temperature. By applying the coating only to the margin, adhesion of the header to the paper is avoided but the central region is not coated and so is not waterproof. To provide another solution, a dual temperature platen, described in US-A-4 820 374 was developed for controlling the area of the header to be heated. This apparatus is effective. However, the cost of the apparatus is not insignificant. As described in US-A-4 820 374, which corresponds to the preamble of claims 1 and 5, this apparatus is used with a paper roll header having a waterproof coating over its inner face, the central part of the header being prevented from adhering to the ends of the roll by the fact that the central region of the platen is not heated sufficiently for the coating to be sufficiently softened in its central region for this to occur. An object of this invention is to provide a header which enables substantial savings for paper manufacturers. According to one aspect of the present invention, there is provided a paper roll header having a waterproof polymeric coating over its inner face, the coating having a thermoplastic character to be heat-softenable for bonding at a predetermined elevated temperature; characterised by a second coating covering the first waterproof polymeric coating only in the central zone of the inner face thereby leaving the first coating exposed only in an outer annular zone of the inner face, the second coating being non-softenable at the said predetermined elevated temperature, whereby the header is sealingly attachable to a paper roll wrapper only in the annular zone by a heated platen pressed against the header. According to a second aspect of the invention, a paper roll, wrapper and header assembly comprises a cylindrical roll of wound paper having around its periphery a wrapper having portions crimped over the outer annular portions of its ends while leaving the central portions uncovered by the wrapper, and a header on each end of the roll, externally of the wrapper, the header having an inner face in abutment with the crimped portions of the wrapper and having inner face central portions adjacent the central roll portions, the inner face of the header having a coating of a waterproof polymer having a predetermined softening temperature, the outer radial portion of the said inner face being sealingly bonded by the said polymer to the crimped portions of the wrapper, characterised by a second coating on the central portions of the inner face, the second coating being nonsoftenable at the said predetermined softening temperature, and the central portions of the inner face being adjacent the said central portions of the roll uncovered by the wrapper, but not bonded thereto. Headers according to the invention do not require a dual temperature heat platen for sealing the header to the crimped wrapper edge. Such headers are coated with a thermoplastic polymer that renders them waterproof, yet the central portion of the header does not become bonded to the rolled paper when the heated platen is pressed against the header. The invention may be carried into practice in various ways but one form of header in accordance with the invention will now be described by way of example together with, by contrast a description of a previously know header. The description will be with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a cylindrical roll of paper; Fig. 2 is a perspective view of a prior art paper roll, wrapper and double header assembly; Fig. 3 is a perspective view of a roll, wrapper and the example of header assembly in accordance with this invention; Fig. 4 is an elevational view of the inner face of the header in Fig. 3; and Fig. 5 is a cross sectional view of the header plate and coatings. Referring now to the drawings, there is depicted in Fig. 1 a conventional roll of paper stock 10, such constituting a cylindrical structure, typically a couple of metres or more long and at least a metre in diameter. The roll has a cylindrical periphery and a pair of ends. It is typically wound on a core 12 as depicted. Fig. 2 shows a conventional paper roll wrapper and double header assembly wherein the roll 10 of Fig. 1 is wrapped by a peripheral enclosing wrapper 14 which is wider than the length of the roll so that the ends of the wrapper can be crimped over the end peripheral edges to form crimped wrapper portions 14' extending over outer annular portions of the ends of the roll. Abutting each of the two ends of the roll directly in this prior art structure is an inner header 16. This inner header is typically formed of a porous stock such as paperboard or the like, and has its outer radial portions covered by the crimped portions 14' of the wrapper. The dotted line in Fig. 2 shows a typical periphery of this inner header. The assembly also includes an outer header 18 which normally is coated on at least its inner face with a waterproof polymer having a predetermined softening temperature. By pressing a heated platen against the outer face, the inner face is pressed against the crimped wrapper and heated so as to sealingly bond it to wrapper portion 14'. Often it is desired to forego the use of an inner header. One reason is cost of added material and more assembly operations. Another reason is that, with use of a vacuum head to pick up the inner header and apply it to the roll, e.g., by robotics, the porous nature of the header causes two or more headers to be inadvertently picked up by the vacuum head to thereby cause difficulty in the operation. It would be desirable at times to be able to apply the outer header directly to the roll, without the use of an inner header, but the outer header still needs to be waterproof, i.e., polymer coated, and the outer header should not be bonded to the paper roll itself. This invention accomplishes these results without the necessity of using the special dual temperature platen described in US-A-4820374. More specifically, referring to Figs. 3 and 4, the paper roll 10 is there shown encompassed by its peripheral wrapper 14 which has portions 14' extending over and crimped against the outer radial portions of the paper roll, leaving uncovered the central portion as depicted. Outer header 28 is sealingly bonded directly to the crimped wrapper portions 14', but not bonded to the paper of roll 10. This outer header has inner and outer faces. At least the inner face is covered by a coating 30 of waterproof polymer, e.g., a polyolefin such as polyethylene, polypropylene, polyvinyl or other such thermoplastic polymer which has a softening point at a predetermined temperature, e.g., 138°C (280°F) for polyethylene. The polymer provides a waterproof coating and also is bondable to crimped portion 14' of wrapper 14. On the central portions of the inner face is a second coating 28a (Fig. 4) applied over the first coating, the first coating still being exposed around the outer annular portion 28b of the inner face. This central second coating extends radially out from the centre of the circular header to a radius greater than the uncovered central portion of roll 10, i.e., so as to be in engagement with only the crimped portions 14' of the wrapper. The central coating is of a material which will not soften at the predetermined temperature at which the first coating softens. This coating is preferably visually discernible from the outer portion, as by employing an ink compound such as a conventional nitro cellulose ink. On a typical roll that has a diameter of, e.g., about 1040 mm (41 inches), approximately 51 to 102 mm (two to four inches) of the radially outer annular portion 28b will be exposed, while the second coating at central zone 28a will cover the remainder of the inner face of the header. With this construction, a simple heat platen may be employed, pressing a header 28 against each end of the roll, softening the outer radial portions at 28b to sealingly bond them to the crimped wrapper portions 14', and seal off the paper from ambient atmosphere. Yet, no bonding occurs to the paper itself so as to lower its quality or usefulness.

Claims: A paper roll header (28) having a waterproof polymeric coating (30) over its inner face, the coating having a thermoplastic character to be heat-softenable for bonding at a predetermined elevated temperature; characterised by a second coating (28a) covering the first waterproof polymeric coating (30) only in the central zone of the inner face thereby leaving the first coating (30) exposed only in an outer annular zone (28b) of the inner face, the second coating being nonsoftenable at the said predetermined elevated temperature, whereby the header is sealingly attachable to a paper roll wrapper only in the annular zone by a heated platen pressed against the header. A paper roll header according to claim 1 wherein the waterproof polymeric coating (30) is a polyolefin. A paper roll header according to claim 1 or claim 2 wherein the second coating (28a) is a heat-resistant compound which is visually distinguishable from the waterproof coating (30). A paper roll header according to claim 3 wherein the second coating is a nitro cellulose-based ink. A paper roll, wrapper and header assembly comprising a cylindrical roll (10) of wound paper having around its periphery a wrapper (14) having portions (14') crimped over the outer annular portions of its ends while leaving the central portions uncovered by the wrapper, and a header (28) on each end of the roll, externally of the wrapper, the header having an inner face in abutment with the crimped portions of the wrapper and having inner face central portions adjacent the central roll portions, the inner face of the header (28) having a coating (30) of a waterproof polymer having a predetermined softening temperature, the outer radial portion (28b) of the said inner face being sealingly bonded by the said polymer to the crimped portions (14') of the wrapper, characterised by a second coating (28a) on the central portions of the inner face, the second coating being nonsoftenable at the said predetermined softening temperature, and the central portions of the inner face being adjacent the said central portions of the roll uncovered by the wrapper, but not bonded thereto. An assembly according to claim 5 wherein the second coating (28a) is coloured to cause a visual difference between the said central portions and the said outer radial portion (28b).

Inventors: YOUNT GEORGE STUART, YOUNT, GEORGE STUART
Applicants: FORTIFIBER CORP, FORTIFIBER CORPORATION
Application year: 1992
Main classification: B65B25
IPC codes: B65B25, B65D85