Apparatus and method of making a paper end with a pressed chuck wall
A novel method and apparatus is provided for forming a pressed paper end which minimizes or eliminates deformations in the chuck wall. The method involves using a novel die press apparatus in which, at the very end of the compression stroke, the paper is held tightly by the opposing dies on either side of the chuck wall forming area, and the chuck wall forming area is held in substantial confinement between the dies.
1. A method of forming a pressed paper end which mitigates wrinkling or tearing of the paper end, the paper end having a circular covering portion having a peripheral area, an annular chuck wall area extending from the covering portion to an annular rim, and a flange area extending from the annular rim, the method comprising the steps of:
(a) providing a die press having an upper tool section moveable relative to a lower tool section, an upper draw ring surrounding the upper die center, and an upper cutting edge, the upper tool section comprising a male upper die center having an outer facing wall shaped like an inverted truncated cone and forming an angle α with the vertical, the lower tool section comprising a lower cutting punch having an inner facing wall shaped like a right-side up truncated cone and forming the same angle α with the vertical;
(b) feeding a paper based web to the die press;
(c) advancing the upper tool section toward the lower tool section until the upper draw ring cooperates with the lower cutting punch to clamp the flange area of the paper disk while allowing the flange area to slip a little between the upper draw ring and the lower cutting punch;
(d) shearing the paper end from the feed web by the upper cutting edge;
(e) forcing the paper end disk toward the lower die center while the upper draw ring and the lower cutting punch maintain tension on the flange area;
(f) bringing the upper die center and the lower cutting punch together so that the chuck wall is squeezed between the outer facing wall and the inner facing wall; and
(g) forming the pre-pressed paper end.
2. The method of claim 1 wherein during step f the peripheral area is compressed between the upper and lower die centers while tension is maintained on the flange area.
3. The method of claim 2 wherein during step f the entire chuck wall area is held in substantial lateral confinement between the upper and lower tool sections.
4. A method of forming a pressed paper end having a circular covering portion having a peripheral area, an annular chuck wall area extending from the covering portion to an annular rim, and a flange area extending from the annular rim, the method comprising the steps of:
(a) providing a die press comprising an upper tool section moveable relative to a lower tool section, the upper tool section comprising a male upper die center having a first forming surface and an outer facing wall shaped like an inverted truncated cone and forming an angle α with the vertical, an upper draw ring surrounding the upper die center, and an upper cutting edge for cutting a paper disk from a feed web, the lower tool section comprising a female lower die center having a second forming surface in confronting relationship with the first forming surface and a lower cutting punch surrounding the lower die center and having an inner facing wall shaped like a right-side up truncated cone and forming the same angle α with the vertical,
(b) feeding a paper based web to the die press;
(c) advancing the upper tool section toward the lower tool section until the upper draw ring cooperates with the lower cutting punch to clamp the flange area of the paper disk while allowing the flange area to slip a little between the upper draw ring and the lower cutting punch;
(d) shearing the paper end from the feed web by the upper cutting edge;
(e) forcing the paper end disk toward the lower die center while the upper draw ring and the lower cutting punch maintain tension on the flange area; and
(f) holding the chuck wall area at an angle to the vertical and in substantial lateral confinement between the outer facing wall and the inner facing wall while compressing a portion of the paper end between the upper die center and the lower die center to form the pressed paper end.