Die cut roll

Details Die cut roll Die cut roll

1999-09-23

2001-08-28

Rada, Rinaldi I. (Department: 3724)

Cutting

Tool or tool with support

Rotatable type

C083S346000

Reexamination Certificate

active

06279443

ABSTRACT:

TECHNICAL FIELD
This invention relates to a die cut roll used to cut sheet type products, such as paper diapers and sanitary napkins.
BACKGROUND OF THE INVENTION
This die cut roll comprises a combination of a die cutter formed by providing projecting pressure cutting blades, which are formed in accordance with the shape of a sheet type product to be cut, on a surface of a rotary driving roll, and an anvil roll. A sheet type work to be cut is made to run between the two rolls, and the die cutter is rotated in an anvil roll-pressing manner so as to cut the sheet type work to a predetermined shape with the projecting pressure cutting blades.
Many attempts have heretofore been made to improve the cutting quality of the cutting blades and prolong the lifetime thereof. For example, Japanese Patent Registration No. 2593570 discloses that the relation between the hardness of pressing ends of cutting blades and that of a surface of an anvil roll has influence upon the lifetime of the cutting blades, and that, when a hardness difference therebetween is set to more than 0.1, the lifetime of the cutting blades increases more than ten times. Japanese Patent Laid-Open No. 227798/1995 discloses the selection of specific materials for creating a proper hardness difference.
Japanese Patent Laid-Open No. 71999/1996 discloses the prolonging of the lifetime of cutting blades with respect to the shape thereof, i.e., it discloses the possibility of increasing the lifetime of cutting blades by setting the cutting blade width of an axial portion thereof smaller than that of a circumferential portion thereof. Japanese Patent Laid-Open No. 72000/1996 discloses crowned die cutters provided in both a die cut roll of a two-shaft driving system in which an anvil roll is driven by two synchronously rotated shafts, and a die cut roll of a single-shaft driving system in which a die cutter alone is driven with an anvil roll driven thereby.
Japanese Patent Laid-Open No. 267299/1997 discloses the techniques for improving the cutting quality of cutting blades without spoiling the strength thereof, by setting the angles &agr;, &bgr; (apex angle becomes &agr;+&bgr;) of two inclined surfaces of each edge of the cutting blades with respect to a radius vector to &agr;≠&bgr;, 0≦&agr;≦60°, 25≦&bgr;≦80° and 5≦&bgr;−&agr;≦80°.
The mode of abrasion of a die cut roll is complicated, and various things cause imperfect cutting of a work, chipping of projecting pressure cutting blades, early deterioration of the cutting performance of edges of the projecting pressure cutting blades and a decrease in the lifetime thereof to occur. Moreover, die cut rolls of different driving systems have greatly different modes of abrasion of a die cutter and an anvil roll, i.e., in a certain driving system, non-uniform abrasion of the rolls occurs, or a decrease occurs in the lifetime of the edge of the cutting blades ascribed to the chipping thereof. When the projecting pressure cutting blades on the surface of the die cutter are formed discontinuously in the rotational direction thereof, an extreme repeated stress is exerted on the pressure cutting blades, and a rate of abrasion thereof increases, so that the imperfect cutting of a work and the chipping of the pressure cutting blades occur. Even when the projecting pressure cutting blades are provided over the entire circumferentially continuous portion of the die cutter with the axial cutting length thereof decreasing due to the shape of the same, the concentration of stress on the blades causes an increase in the rate of abrasion thereof and the chipping thereof.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a die cut roll having an improved cutting performance of the edges of projecting pressure cutting blades and a prolonged lifetime.
Another object of the present invention is to provide a die cut roll capable of resisting the stress occurring when an edge of a projecting pressure cutting blade and an anvil roll are brought into contact with each other adjacent to a top smooth portion of the edge.
Still another object of the present invention is to provide a die cut roll which has attained a long lifetime thereof with respect to greatly different modes of abrasion of a die cutter and an anvil roll occurring due to different die cut roll driving systems in use.
A further object of the present invention is to provide a die cut roll which has attained the reduction of stress concentration on projecting pressure cutting blades used for cutting a work to a final shape.
A first embodiment of this invention is directed to a die cut roll having inclined finishing surfaces of less than 0.1 &mgr;m in a surface roughness Ra on ridge surfaces adjacent to a top smooth portion of each projecting pressure cutting blade, or inclined finish surfaces having grinding muscles extending at 50°-90° and preferably 80°-90° with respect to ridge lines defining the top smooth portion, a surface roughness Ra being set to preferably less than 0.3 &mgr;m when the grinding muscle-carrying inclined finishing surfaces are formed.
Another embodiment is directed to a die cut roll, wherein one or both of a width and an apex angle of each projecting pressure cutting blade formed so as to extend in the axial direction of a die cutter is set smaller than those of each projecting pressure cutting blade formed so as to extend in the circumferential direction of the die cutter, preferably a width da and an apex angle &thgr; a of an edge of the axially formed projecting pressure cutting blade, and a width dc and an apex angle &thgr; c of an edge of the circumferentially formed one being set to 5≦da≦10 &mgr;m, 60≦&thgr; a≦120°, 10≦dc≦30 &mgr;m, 80≦&thgr; c≦140°, and &thgr; a≦&thgr; c.
For driving the die cut roll consisting of a die cutter and an anvil roll, two types of driving system can be adopted. One is the two-shaft driving type in which the driving force of a motor is transmitted to both shafts of the die cutter and the anvil roll by means of a gear to rotate the die cutter and the anvil roller synchronously. The other is the single-shaft driving type in which the driving force is transmitted to the shaft of the die cutter and the anvil roller which is in contact with the die cutter and is aligned in parallel with the axis of the shaft of the die cutter and is rotated by the friction with the die cutter.
Another embodiment of this invention is directed to a die cut roll having a difference between the hardness of a die cutter and that of an anvil roll with respect to above cut roll driving type, concretely speaking, H
1
representative of a hardness (H
R
A) of at least an edge side portion of a cutting blade of a die cutter and H
2
representative of a hardness (H
R
A) of at least an outer surface of an anvil roll satisfying the conditions 82≦(H
1
, H
2
)≦96(H
R
A) respectively, and 0<H
2
−H
1
<5 when a two-shaft driving type die cutter is employed, and −5<H
2
−H
1
<1 when a single-shaft driving type die cutter is employed.
A further embodiment of this invention is directed to a die cut roll provided with projecting pressure cutting blades not directly working to cut a product, i.e. so-called supporting blades in addition to proper projecting pressure cutting blades, which are formed in accordance with the shape of products to be cut, so as to compensate for at least circumferentially non-continuous portions or axially cutting length-decreasing portions of the proper projecting pressure cutting blades.
The projecting pressure cutting blades for products of a die cutter may be provided so that the blades extend continuously in the circumferential direction of the die cutter, or so that end portions of the blades overlap in the circumferential direction thereof.
The materials out of which the die cutter and anvil roll can be formed include hard materials, such as a sintered hard alloy inclusive of a WC based alloy, a cermet inclusive of a Ti based alloy, high speed steel, and a ceramic mater

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