Severing by tearing or breaking – Methods – With preliminary weakening
Reexamination Certificate
2001-12-21
2004-11-23
Peterson, Kenneth E. (Department: 3724)
Severing by tearing or breaking
Methods
With preliminary weakening
C083S500000, C083S675000, C225S094000
Reexamination Certificate
active
06820784
ABSTRACT:
FIELD OF THE INVENTION
This present invention relates generally to apparatus and methods for cutting webs, and, more particularly, to methods for cutting a laminated web structure and, most particularly, laminated or multilayered imaging elements that include at least one upper or protective layer, an image-forming layer, and an imaging support.
BACKGROUND OF THE INVENTION
Laminated webs are utilized widely for various applications. In imaging applications, for example, a protective layer is often used over the image-forming layer to protect it from being harmed by contact friction with apparatus parts and between the front and back surfaces of the element. It may also be used to control moisture, curl, stiffness, and other physical properties.
The laminated web and laminated imaging element are typically formed in long, wide sheets and then spooled into large rolls. These large wide rolls must then be converted into predetermined smaller sizes by slitting, chopping, and/or perforating the large wide rolls. It is important that the various conversion operations, also referred to as cutting processes, be performed without damaging the web. It is also important that the conversion be performed without creating substantial amounts of dust or hair-like debris that might lead to undesirable contamination of imaging surfaces for imaging applications.
The generation of this hair-like debris is generally attributed to an adverse combination of stiffness and toughness of the various layers of the laminated web. A poor combination of stiffness and toughness properties of various layers results in uncontrolled crack propagation during cutting and the subsequent formation of hair-like debris. For example, there is a problem with the element described in U.S. Pat. No. 5,866,282 in that the cutting of this imaging element results in the creation of substantial amounts of hair-like debris which are highly undesirable. The poor cutting performance may be traced at least in part to the material selection and ordering in the laminate, resulting in an adverse combination of stiffness and toughness of the various layers of the imaging element and uncontrolled crack propagation during cutting.
The process of cutting sheet materials is similar to driving a crack through a material using a wedge. Accordingly, fracture mechanics theory (“
Fracture Mechanics, Fundamentals and Applications
”, T. L. Anderson, 1991) may be used to guide the selection of layer materials that produce the desired cutting performance. Fundamentally, cutting processes are fracture processes. One needs to initiate and propagate a crack through the thickness of the substrate. A clean cut usually requires good control over crack initiation and propagation throughout the cutting process.
Many methods and apparatus for cutting laminated imaging elements are known in the art. These prior art cutting methods and apparatus include cutting wheels, ultrasonic cutters, scissor type cutters and guillotine knives.
FIG. 1
is a partial sectional view illustrating the cutting edge portions of typical, opposing prior art cutters including an upper knife
10
and a lower knife
12
for cutting and slitting an imaging element
14
. The first and second cutters are separated by a clearance
15
. Imaging element
14
typically includes a support web
16
with an imaging layer or multilayer composite layer
26
coated thereon. It is common for the lower knife
12
to have a square edge or low rake angle
22
and low relief angle
20
, and the upper knife
10
to be ground at some rake angle
18
. The upper knife
10
may also have a low relief angle
24
. The upper knife
10
generally has been applied to the upper or photosensitive side of the imaging element
14
during slitting with the lower knife
12
in contact with the opposite side thereof. However, in some instances, the reverse has been practiced. Typically, the upper knife blade previously used has had a low rake angle, 10-15 degrees, ground on the edge. The low rake angle was used because it was an improvement over a square edge with no rake, and a mid range angle, such as 30 to 45 degrees. More recently, U.S. Pat. No. 5,974,922—Camp, et al. discloses a high rake knife for slitting photographic papers.
A significant disadvantage in these prior art methods was the inability to cut the web without cutting or damaging one or more of the weaker layers and interfaces. Another major disadvantage was the inherent difficulty experienced when trying to control the material fall-off, which produces dust from the cut process. Therefore, there is a continuing problem with dirt and debris generated during cutting that will contaminate images during development. This is especially true for laminated imaging elements that have thick, tough polymer protective layers, and the image-forming layer is very stress sensitive.
It has been a technical challenge to cut laminated imaging elements without damaging the finished edges and generating debris. This problem is more significant nowadays since tough polymer layers are often used as protective layers for a laminated imaging element. The addition of this tough layer may change the cutting characteristics of the imaging element. Therefore, when using the existing method and tool in the art, the cutting operation causes significant defect and debris that is not acceptable.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved method for cutting laminated webs such as imaging/photographic elements.
It is a further object of the present invention to provide a method for cutting laminated webs, especially laminated imaging elements, that generates less cutting defects during the cutting process.
A further object of the present invention is to provide a method for cutting laminated webs, such as imaging/photographic elements, which reduces damage to the interface between layers or laminates.
Yet another object of the present invention is to provide a method for cutting laminated webs, such as imaging/photographic elements, that reduces the amount of dust and debris produced by the cutting operation.
Briefly stated, the foregoing and numerous other features, objects and advantages of the present invention will become readily apparent upon a reading of the detailed description, claims and drawings set forth herein. These features, objects and advantages are accomplished by providing a method for cutting a laminated web, comprising the steps of engaging a first side of the laminated web with a crack initiator having a high rake angle, the crack initiator extending from a first cutter base having a low rake angle, the laminated web including at least a support web and an upper layer that may, at least for imaging elements, be considered a protective layer, the upper layer being thinner than the support web, the upper layer being located at the first side of the laminated web structure; simultaneously engaging a second side of the laminated web with a second cutter; generating a first crack in the first side of the laminated web with the crack initiator completely through the upper layer; engaging the web with the cutter base of the first cutter and further propagating the first crack using the cutter base while disengaging the crack initiator of the first cutter. With the crack initiator disengaged, the method may include the step of propagating the crack through to the second side of the laminated web. Alternatively, the method may include the step of generating a second crack in the second side of the web with the second cutter and propagating the first cut to intersect with the second crack.
The laminated web may further include one or more intermediate layers. When the laminated web is an imaging element, the intermediate layer would be an imaging/photographic layer or composite layer such as, for example, a silver halide layer.
As described above, the first or upper side of the laminated web is the side with the protective layer. The protective layer is thinner than the support web. In the case of the laminated i
Bhave Aparna Vasant
Gao Zhanjun
Lai Yeh-hung
Nair Mridula
Bocchetti Mark G.
Eastman Kodak Company
Hamilton Isaac
Leipold Paul A.
Peterson Kenneth E.
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