The present invention relates to a method and apparatus for the precision cutting of corrugated paperboard panels into specimens having square, or other rectangular, shapes of predetermined size, e.g., four inches on a side, etc. The precision, cut to size specimens are subsequently used as test specimens for various measurements, e.g., bending tests, column strength tests, edge compression tests, flat crush tests, and adhesion tests.
Apparatus has previously been developed for cutting corrugated paperboard panels into square or rectangular configurations for subsequent use as test specimens in standardized testing of the paperboard material. The conventional cutting apparatus can take various forms. One known cutting apparatus comprises a horizontal table or platform having a flat upper surface adapted to receive the corrugated paperboard panel flatwise thereon, and an elongated knife blade swingably connected to the table for downward motion along one edge of the table. A handle extending from the elongated knife is pulled downwardly so that the knife blade slices through the paperboard panel in a downward arc, to thereby form a straight edge on the panel. The panel is then repositioned on the table, and the cutting process is repeated to form four straight edges on the paperboard panel.
The above table is equipped with an upstanding linear abutment, or backstop, oriented at right angles to the cutting plane of the knife blade, whereby the paperboard panel can be positioned with a cut straight edge engaged against the abutment, while the various cuts are being made in the panel. The abutment, or backstop, permits successive cuts to be made at right angles to one another, so that the final test specimen has a rectangular, usually square, or other rectangular, configuration.
The cutting table, or platform, may have a slidably adjustable T-square, that includes a horizontal upstanding straight edge extending parallel to the cutting plane of the vertically-oriented knife blade. The horizontal spacing between the upstanding straight edge and the blade cutting plane, can be varied or changed to permit variation in the size of the cut specimen, or test specimen panel. As previously noted, the cut test specimen will usually have a square, or other rectangular, shape. Typically, the cut square or rectangular specimen, will vary in size from an upper limit of about six inches along each edge, to a lower limit of about one inch along each edge. The size of the cut test specimen is determined by tests to be performed, and effectuated by the settings of the slidable T-square, or, more properly, an L-square.
The cutting blade can be arranged for vertical motion along an edge of the panel support table, as previously described. However, a vertically moving cutter blade does not achieve an optimum cutting action, since it exerts a downward pressure on the upper surface of the paperboard panel. The cut edge may thus be slightly depressed, or squashed, especially if the cutter blade is slightly worn, in which case, there is a greater cutter blade edge area in contact with the paperboard surface.
As an alternative, and as practiced in the present invention, the cutter blade can be made to move horizontally through the paperboard panel parallel to the panel faces, i.e., the cutting blade can be arranged to move horizontally along the table surface so as to produce essentially no deformation of the panel face. In such a case, the lower end of the cutter blade extends into a slot in the table surface, while the cutting edge of the cutter blade extends generally vertically, so that the cutter blade attacks the edge of the paperboard panel along a horizontal action line.
The cutter mechanism can be operated manually, or with a power actuated mechanism, e.g., a fluid cylinder. In one known apparatus, an air-operated fluid cylinder is supported for horizontal motion across the table surface. A cutter blade is carried by the movable portion of the cylinder, such that pressurization of the cylinder sends the cutter blade across the table to form a cut straight edge on the corrugated paperboard panel. Reverse motion of the cylinder returns the cutter blade to its original position ready for the next cutting cycle, after repositionment of the paperboard panel.
One major and serious disadvantage of all existing prior art cutting apparatus, is the fact that there is no mechanism for precisely determining, and effecting, the precise orientations of the test specimen panel cut edges, relative to the internal flutes in the corrugated paperboard panels, prior to making the cuts. The term, "flutes," is herein used to mean the linear passages, or `tunnels,` formed within the corrugated paperboard panel, by the corrugated internal liner sheet.
Typically, the corrugated paperboard panels have two flat spaced-apart outer sheets, and an internal corrugated liner sheet. The corrugations, or undulations, defining the flutes, space the two outer sheets apart, and determine the overall thickness of the panel. Typically the paperboard panel will have a thickness of about one-eighth of an inch, such that each undulation has a transverse dimension slightly less than about one-eighth of an inch.
The square or rectangular test panels are designed to be subjected to several different tests, including an extremely important edgewise compression test, which should be performed `perfectly`, or precisely, parallel, to the direction of the internal flutes, or, alternately, `perfectly` normal to the flute direction. In order to produce reproducible, or duplicate, test results on similarly constructed paperboard panels, it is necessary that the square or rectangular test specimen panels be uniformly and precisely cut, or formed, so that two of the test specimen panel edges are always precisely parallel to the flutes, and the other two specimen panel edges are always precisely normal to the flutes.
The hollow, internal flutes are located within the corrugated paperboard panels, so that the flute direction is not always readily determined by a visual inspection of the uncut corrugated paperboard panel. However, it is possible to form a panel edge running "approximately" parallel to the flute direction, by a trial-and-error process, wherein the edge of the test specimen, or sample, is inspected after the first cut, to determine the approximate extent of the deviation from parallelism.
However, such visual trial-and-error inspection, involves an inspection of the corrugated panel sheet edges that are in semi-concealed locations between the outer facing sheets of the corrugated paperboard panel. Therefore, the observer is never quite certain, from a visual inspection, whether or not, the first cut is, in fact, exactly, or precisely, parallel to the internal flute direction. In any event, such visual inspections, as flawed as they are, also require a lengthy amount of time, and a certain degree of skill, on the part of the operator.
It is possible to pry apart the edges of the outer facing sheets of the paperboard panel, in order to better see the directions of the flutes. However, such an operation destroys the integrity of the panel edge, and thus renders the panel essentially useless for edge compression strength testing, and other test measuring purposes.
There is a clear and strong need for a corrugated paperboard panel cutting method and apparatus, wherein the first cut of the panel test specimen, is made either precisely parallel, or precisely normal, to the flute direction, such that the final square, or other rectangular, test speimen panel, has two edges running precisely normal to the flute direction and two edges running precisely parallel to the flute direction. If the test specimen's first cut edge can have the desired precise orientation relative to the flute direction, the remaining three test specimen edges can automatically be made to have the necessary orientations, e.g., by using T-square cutting guide surfaces properly oriented to the cutter blade plane. The present invention is directed to a method and apparatus for achieving either the desired parallelism, or normalcy, between the test specimen's first cut edge and the flute direction, as well as subsequent cut edges.
An additional problem inherent in conventional cutter blade constructions, which has been elegantly solved by the present invention, is the premature dulling of the cutter blade. With conventional arrangements, the same zone of the cutter blade's cutting edge is used continually for each cutting cycle. The cutting pressure is repetitively applied to a relatively small localized area of the cutter blade edge, so that the cutter blade becomes dull after only a relatively few cutting cycles, necessitating frequency replacement of the cutter blade.
Cutter blade replacement requires time, and also involves potential danger to the operator, because the cutter blade edge is extremely sharp, especially the new replacement cutter blade. Manual handling of the cutter blade during blade removal or installation can, therefore, cause serious injury to the operator.
The present invention also seeks, in part, to provide a cutter blade construction, wherein, different zones of the cutter blade's cutting edge are used for cutting purposes during successive cutting cycles. Wear on the cutter blade is, therefore, distributed over a longer cutting edge area, such that cutter blade replacement is less frequent, compared to prior art arrangements.