Cutting – With means to clean work or tool
Reexamination Certificate
1999-12-16
2004-03-02
Goodman, Charles (Department: 3724)
Cutting
With means to clean work or tool
C083S871000, C083S174100
Reexamination Certificate
active
06698325
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a machine for skiving or splitting nonmetallic planar workpieces, in particular plastic-coated paper-like workpieces, having a motor-driven moving knife, in particular a bell knife or hoop knife, whose cutting edge has a specific contour and moves continuously around a closed loop; and having a grinding device for grinding the knife.
A skiving machine of the aforesaid kind is known, for example, from DE 41 01 377.
Skiving machines are used, for example, in the shoe industry or pursemaking industry, to create a specific profile on the edges of cut sheets of leather, leather replacement materials, rubber, or plastic. A bell knife made of metallic material, which is cup-shaped and is equipped on its front circumferential edge with a cutting edge, is used for this purpose. The bell knife generally sits directly on the shaft of a high-speed, high-output electric motor, or on a spindle and is driven by a motor via a belt. Because the cutting edge of the bell knife made of metallic material is susceptible to wear, it is necessary to grind the cutting edge, from time to time or continuously, so as to sharpen it. Grinding devices that have corresponding deburring devices, as well as dressing devices for a grinding wheel of the grinding device, are known for this purpose.
A splitting machine is known, for example, from DE 38 15 130 A1.
This splitting machine is a hoop knife splitting machine that is equipped with a knife, in the form of an endless steel hoop, that runs over two belt pulleys, one of which is motor-driven. Since the circulating steel knife is subject to wear, a grinding device is provided with which the hoop knife is intermittently or continuously ground to sharpen it.
A feature common to both machines, i.e. skiving and splitting machines, is therefore the fact that they have a moving knife with a specific cutting edge contour that must be reground from time to time.
Since the contour of the cutting edge and the exact position of the cutting edge or cutting line is critical in terms of the skiving or splitting quality, the designs must be such that a flawless cutting edge contour is guaranteed despite the continuous or intermittent regrinding, and such that the position of the cutting edge or cutting line is exact and predetermined.
The field of application of such machines is gradually expanding, since skiving or splitting operations that earlier were performed principally on planar workpieces made of leather are now also being performed on other types of material.
Such workpieces include, for example, paper-like or board-like materials coated with plastic and/or aluminum foil.
Materials of this kind are used, for example, in the beverage industry. Beverage packages such as, for example, milk cartons or juice cartons are manufactured from plastic-coated board stocks of this kind.
Cut sheets of this kind can easily be coated on both sides with a plastic material that is approved for food contact, for example polyethylene. On the cut edges, however, the paper core material is exposed. In order to process these board materials into sealed beverage cartons, it has become known to equip the edges with, for example, a stepped cut by way of a skiving operation. This involves applying a corresponding stepped cut in the region of one edge of the cut sheet, on one side, using a bell knife of a skiving machine, so that a thinner portion of the board material remains on the rim which is then coated with plastic on only one side. This rim is then folded over itself, specifically over the uncoated side, thus resulting in an edge that is coated with plastic on its continuous peripheral edge as well. By heat-sealing several such folded-over edges to one another, it is then possible to construct a three-dimensional object, for example a parallelepiped or tetrahedron.
In processing such materials with a bell knife, it has been found that a deposit of contaminants, which is highly adherent and is made up predominantly of plastic coating material from the workpieces being processed, gradually accumulates in the region of the cutting edge. In the case of a skiving operation, for example, 560 meters per minute of edge material can be cut or skived.
Since the cutting edge contour of the knife is reground periodically or continuously, the grinding device encounters the adhering contaminants in the region of the contour and removes them as well.
Since these contaminants are made of sticky, viscous materials, they clog up the grinding wheel, so that it quickly becomes unusable. As a result, only relatively short service lives of one to two hours can be achieved, since the grinding device is completely clogged with the plastic materials after only a few grinding cycles.
Since the cutting edge of a bell knife is usually ground only on one side, only the contaminants adhering to that one side can be removed at all by the grinding wheel.
Similar impurity problems can also occur in splitting machines on hoop knives, since they have a similar cutting edge contour and similar problematic deposits can thus occur.
SUMMARY OF THE INVENTION
It is thus the object of the invention to provide a remedy here, and to improve a skiving or splitting machine of the kind cited initially in such a way that long service lives can be obtained for the knife and grinding device.
According to the present invention, the object is achieved in that a cleaning device which can be placed against the contour of the cutting edge, and with which the contaminants adhering to the cutting edge can be removed, is provided, the cleaning device being adaptable to the contour of the cutting edge.
The provision of a separate cleaning device has the considerable advantage that contaminants adhering to the cutting edge can be removed before the grinding device comes into engagement with the knife. This thus prevents the grinding device from quickly becoming clogged with the contaminants and requiring replacement.
The grinding device can then exclusively perform its grinding function, since it encounters a cleaned cutting edge; as a result, long service lives can be obtained for the grinding device, which then also results in long service lives for the knife.
Because the cleaning device is adaptable to the contour of the cutting edge, this contour is not adversely affected, i.e. its geometry is not changed and the cutting edge is cleaned exactly along its contour. This means that there are no remaining residues of contaminants that then are removed by the grinding device and would gradually clog it, which in turn would be detrimental to its service life.
Because the cleaning device is adaptable to the contour of the cutting edge, the grinding device is only just in engagement with the impurities on the cutting edge, and does not adversely affect the contour as such.
It has already been mentioned previously that the contour of the cutting edge is quite critical for the skiving or splitting quality. If residual contaminants were to remain behind, the grinding quality could be negatively influenced thereby, which is undesirable. In the case of thin knives, the geometry of the contour could be changed if the deposit were removed using large forces. The adaptability feature prevents this.
Very long service lives, and thus availabilities of up to 99.85%, can be achieved.
The object is thereby completely achieved.
In a further embodiment of the invention, the cleaning device is displaceable along the contour, transversely to the movement direction of the knife.
The advantage of this feature is that the cleaning device can be arranged and can work, in space-saving fashion, away from the actual working point of the knife on its edge and transversely to its movement direction.
In a further embodiment of the invention, the cleaning device cleans the cutting edge on both sides of its cutting portion.
The advantage of this feature is that the cutting edge is cleaned on both sides, thus continuously ensuring outstanding cutting quality.
If, for example, a knife is always reground only on one side, which
Fortuna Spezialmaschinen GmbH
Goodman Charles
Renner , Otto, Boisselle & Sklar, LLP
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