Printing – Intaglio – Wipers
Reexamination Certificate
2000-06-06
2001-09-11
Hilten, John S. (Department: 2854)
Printing
Intaglio
Wipers
C015S256510
Reexamination Certificate
active
06286426
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to doctor blades, more particularly but not exclusively for stripping excess ink from a rotating printing roll in the surface of which there are arranged depressions for filling with printing ink. The doctor blade is attached to a holder carried by an adjustable apparatus, which determines the force with which the doctoring edge of the blade lies against the printing roll. Such blades are exposed to wear and must be changed after a period of use.
A conventional doctor blade consists of a strip, which is formed along its length with a thinner forward portion and a thicker rear portion. The free edge of the thinner portion is intended for use as stripping edge, while the thicker portion is intended for clamping in a standard type of blade holder for the printing machinery in question. The advantage of the thin portion of more or less even thickness is that the wear on it can take place without the wear causing any unacceptable alteration of the profile of the scraping or doctoring edge engaging the printing roll.
PRIOR ART
U.S. Pat. No. 4,359,799 discloses the use of a replaceable thin and narrow strip as a doctor blade. The strip is clamped in a doctor blade holder which is relatively flexible transversely and longitudinally.
The longitudinal flexibility is however reduced when insoluble dried or solidified ink accumulates in the interior of the holder, for instance with water-based inks.
This solidified ink sometimes makes changing of the strip extremely difficult and can even prevent a proper installation of a new strip. Further, such a doctor blade will be wavy and make doctoring unsatisfactorily, resulting in poor print quality. A certain amount of waviness of the doctor blade can be accepted, but a higher blade pressure against the printing roll must be applied. As a result the doctor blade life will be short.
In certain types of printing machines, the design requires a kind of sealing-blade to prevent the ink flow underneath the doctor blade from running too far into the mechanism of the doctor blade holder system. This stationary seal or sealing blade is supposed to be ink-tight against the transversely oscillating doctor blade. Too often this seal leaks and allows ink to flow out onto the floor in the printing works. As a result, the printing press must be stopped and the seal repaired. Even minor leakage, which does not require immediate attention will still result in loss of printing ink and a poor work environment.
SUMMARY OF THE INVENTION
A doctor blade assembly has a flexible doctor blade holder consisting of a wider flexible carrier plate by means of which the assembly is mounted, a narrower flexible presser plate and a flexible wedge member held together with a plurality of ties. A replaceable doctor blade is formed by a strip of uniform thickness and is clamped together with a narrower back-up strip securely but releasably between the forward edges of the carrier plate and the presser plate, the wedge member being inserted between the rear edge of the presser plate and the carrier plate. The wedge member has a rear portion including a flange projecting away from the carrier plate both to permit manual manipulation of the wedge member and to divert liquid, such as ink, away from the carrier plate.
REFERENCES:
patent: 2007418 (1935-07-01), Akre
patent: 3986453 (1976-10-01), Boose
patent: 4359799 (1982-11-01), B{umlaut over (oo)}se
patent: 1 507 825 (1978-04-01), None
Flynn ,Thiel, Boutell & Tanis, P.C.
Hilten John S.
Williams Kevin D.
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