Manufacturing container or tube from paper; or other manufacturi – Container making – Rigid container
Reexamination Certificate
1998-12-10
2001-03-20
Johnson, Brian L. (Department: 3618)
Manufacturing container or tube from paper; or other manufacturi
Container making
Rigid container
C063S033000, C063S033000, C063S033000
Reexamination Certificate
active
06203482
ABSTRACT:
BACKGROUND OF THE INVENTION RELATES
(a) Field of the Invention
This invention relates to dies for, and a method of, forming folded cardboard cartons, which also include package-opening features in the nature of tear strips.
(b) Description of the Prior Art
Methods and apparatus are now known for die cutting cardboard. In addition, tear strips have been produced in such cardboard cartons by die cutting the cardboard from opposite sides thereof to provide removable areas which are defined by relatively widely spaced-apart creases extending into one surface of the cardboard and more closely spaced-apart creases extending in parallel side-by-side relation to the first creases and extending into the opposite side of the cardboard. When the intermediate area was grasped, the cardboard split from one cut crease to the other to permit removal of the defined area. Under normal circumstances, this die-cutting operation was done by first die cutting one side of the cardboard and then die cutting the opposite side of the cardboard in a separate operation. This method had been carried out using cutting presses which were normally provided with a die which was engageable with one side only of the cardboard.
Steel rule dies for cutting and scoring as well as embossing sheets of cardboard have been fabricated from wood, laminated wood, resinated and impregnated woods, in which the steel rule cutting knives and scoring rules had been fitted into slots which were cut into the die body of the wood or metal and which were held in position by various means, including the introduction of plastic materials, e.g., epoxy resins, into slots or cavernous openings in the die base to anchor securely the cutting rules and scoring rules from displacement. The rule-retaining means had been time consuming to fabricate and costly to build. The life of steel rule dies that had been encavitated for supporting the steel rules by introducing plastic materials to support the rules in a solid base material have not been commercially successful.
Reusable counterplates for cutting and scoring boxboard or paperboard to form carton blanks must be accurately constructed for reuse on hundreds of thousands or millions of impressions and cuttings, thereby necessitating precision fabrication and highly durable materials for providing cutting and scoring dies for retaining the cutting and scoring plates or rules in position in their slots within the base or supporting die member. Such cutting and scoring dies included cutting knives defining the outline of the blank as well as the location of other cuts through the cardboard, and scoring rules which weakened the cardboard in preparation of subsequent folding operations.
Cutting knives and scoring rules are flat or bent strips of sheet steel, which were provided either with a sharp cutting edge or with a rounded scoring edge, depending on their respective use, and were manufactured by several alternative procedures. According to one conventional manufacturing procedure, the cutting knives and the scoring rules of a die were assembled in upright position, with the cutting edge or the scoring edge pointing upward, the spaces between the various knives and rules being filled by blocks. A conventional cutting and scoring die was laid out by selecting available such assembled dies having the desired dimensions, placing the knives and rules thereon and then tightening the entire assembly by wedges, or otherwise, within a surrounding frame or chase. The above outlined procedure made the accuracy of the box blanks dependent on the skill and the care of the diemaker.
According to another conventional manufacturing procedure, slots were cut into a large block or panel of wood and the knives and rules were placed in these slots. This construction made it necessary to discard the entire die when a major dimension of the box, e.g., length, width or height, was changed.
According to yet another conventional manufacturing procedure, a rule die set had a base on which a male die was rigidly mounted. A female die was provided on a ram and was cooperative with the male die on each working stroke of the ram to blank a piece from cardboard. The female die was in the form of a rule which was embedded in plywood which engaged and held the rule along its side walls. The upper end of the rule abutted against the bottom of the ram directly to receive the working force, the wood blocks being used for a die supporting function. The lower or cutting edge of the rule projected downwardly and beyond the bottom surface of the wood. Within the rule and in the space between the inside wall of the rule and between the surface of the wood and the cutting edge of the rule, was a stripping element, usually a resilient elastomer material, e.g., hard rubber. With each working stroke of the ram, the rubber was compressed between the metal work piece and the surface of the wood as the rule passed through the cardboard. When the ram extracted, the rubber expanded and such expansion served to strip the blanked cardboard piece from the rule.
With such construction, providing sufficient stripping force involved problems. If a large piece of stripping rubber was employed which completely filled the space inside the rule, the compression forces of the confined rubber were directed not only to the surface of the wood but also against the inside wall of the rule. The lateral forces against the rule were transmitted to the wood and tended to rupture it. Further, each time the rubber expanded to strip the blanked piece, there were forces directed against the rule tending to pull it outwardly of the ram and the supporting blocks. If the wood was ruptured and the rule became loose, the die structure was rendered inoperable and had to be reconstructed.
According to a still further manufacturing procedure, the outline of the carton was laid out upon a board, e.g., plywood. The outlines were then cut with a jig saw, the width of the saw cut being equal to the thickness of the steel cutting band, whereupon the cutting bands,which were shaped to conform with the outlines of the carton, were forced into the saw kerfs provided therefor. Thus, each cutting band or individual die member was permanently fixed in the base board or supporting member in accordance with the position of the carton. Any slight error of the diemaker in positioning one of the die members with relation to the others was difficult to correct.
Several expedients have heretofore been used to correct lack of positioning. One of such expedients comprised cutting out an entire die member from the integral block and then providing shims in the saw cuts to move the defectively registered die into proper registration. This method entailed a great deal of labour and increased the cost of the die.
Another expedient formerly employed was to bend the extended portion of the cutting bank slightly into conformity with the outline of the carton. This latter expedient required the die steel to be untempered to enable the cutting bands to be bent. The life of the die was relatively short.
In other words, such die sets have been made by setting steel rules for cutting the cardboard in a predetermined pattern between individually cut wood blocks, which were held in a steel frame by wooden wedges with the edges of the rules extending above the blocks. Small blocks of sponge rubber, or synthetic cork, were generally placed on each side of the cutting rule to push the board free of the knives on completion of the cutting stroke. The scoring rules, in most systems, were glued to the wooden blocks. Other systems of dies were known in which the steel rules were inserted into grooves cut by jig saw into a slab of plywood of, e.g., ¾ inch thickness in a predetermined pattern so that when the plywood die was brought to bear against the cardboard, a blank of the desired configuration was stamped out.
In the formation of tear strips of the type employing a peripheral pair of die cut grooves in opposite sides of the cardboard, it was usual practice to have the die cuts or grooves extend
Birch & Stewart Kolasch & Birch, LLP
Johnson Brian L.
Luby Matthew
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