Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With bending – folding – winding – or wrapping means
Patent
1998-01-23
2000-03-21
Jones, Deborah
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With bending, folding, winding, or wrapping means
83128, 101 24, 156250, 156510, 493 59, 493 79, 493356, 493405, B26F 144
Patent
active
060391014
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus for the cutting and creasing of plastics sheet materials, in particular such materials having voids therein sometimes referred to as corrugated sheets.
Cutting and creasing of such sheet materials is carried out mostly to produce blanks, e.g. for the production of cartons or boxes. Traditionally, box blanks of paper board and many plastics sheets have been cut and creased cold using pressure only. While this is satisfactory for some materials, plastic sheet material and blanks often retain a "memory" and tend to revert to their original configuration after creasing. This memory is particularly pronounced in polypropylene and other polyolefin-based materials and increases with the buckling resistance of the sheet. Furthermore, as the weight of corrugated sheet per unit area decreases in relation to thickness, thus giving rise to thinner sections, it becomes more difficult to convert into a useful blank free from cracking and able satisfactorily to resist shearing and other forces to which it is likely to be subject in use.
Another approach is to use a heated cutting and creasing tool which, provided sufficient heat is introduced into the sheet, overcomes both the general `memory` problems of plastics sheet and the cracking, as well as the problems due to unsatisfactory resistance to shearing and other forces, but introduces problems of its own. In order that the strength and appearance of the sheet material is not impaired to too great an extent, it is necessary to protect the greater area of the sheet from the hot tooling during the cutting and creasing process so that the heat is applied principally in the areas to be cut and creased. This militates against the use of a flat metal bottom plate or platen. The use of a bottom plate or platen having raised "anvils" is successful but is relatively expensive and inflexible. That is, should the outline of the blank be changed in any degree it is necessary to produce a new bottom plate, often milled out of a solid block, and this is expensive. Moreover, it has been found that the repeated action, particularly of the cutting blades, can score the metal surface. In view of the heated environment, plastic material from the sheet can get trapped in these score lines thus rendering the tooling ineffective in that the products are not properly formed or are unsightly. Furthermore, the action of the cutting blades being arrested by a metal bottom tool blunts then and leads to the requirement for frequent refurbishment of them.
The invention seeks to provide a tooling apparatus improved in the above respects.
According to the present invention there is provided an apparatus for the cutting and creasing of plastics material sheet which comprises a cutting and creasing tool and a corresponding plate arranged for mutual contact characterised in that the plate is free of raised surfaces and is covered with a resilient material.
We have surprisingly found that excellent results can be obtained using a flat platen or bottom plate provided that its surface is, or is covered by, a layer of resilient material, especially a plastics material. The plastics material must be sufficiently tough and heat resistant to cope with the heat and the mechanical action of the cutting and creasing process and, while other materials may be used, we have found that a sheet of nylon 66 provides excellent results. In a preferred embodiment, two such sheets are employed, one thicker than the other, with the thinner sheet outermost. It has been found that when wear finally takes place on the outer sheet it can firstly be turned over and then be replaced without needing to replace the inner sheet for a further period of time.
It has been further found that the use of a continuously or intermittently indexed thin sheet of a cheap material, far less robust than nylon, for example brown paper, fed across the surface of the resilient material sheet to present a fresh portion, wholly or partly, each cycle further increase flexibility, reduces changeover time, reduces
REFERENCES:
patent: 2263626 (1941-11-01), Halbig et al.
patent: 3584572 (1971-06-01), Apicella
patent: 4462288 (1984-07-01), Boyce
Jones Deborah
Koehler Robert R.
Korpak Limited
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