Printing – Intaglio – Rotary
Reexamination Certificate
2000-10-11
2003-06-24
Nguyen, Anthony H. (Department: 2854)
Printing
Intaglio
Rotary
C101S153000
Reexamination Certificate
active
06581516
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a doctor device, in particular a chamber-type doctor device, in an inking unit of a rotary printing machine, having a base member and a working doctor adjustable with respect to the base member.
In rotary printing machines, inking units have become known heretofore which have a doctor device with a working doctor associated therewith, the working doctor resting on the surface of an engraved or screen roller formed with dimple-like or groove-like depressions, or on the engraved surface of a gravure printing roller. As a result, for example when using the engraved or screen roller, the ink or other coating material is doctored or squeezed off the webs located between the depressions on the rotating engraved or screen roller, while the ink in the depressions in the engraved or screen roller passes by the working doctor. Because the working doctor lies under a given prestress on the rotating engraved or screen roller, the working doctor is subjected to continual wear. The working doctor is thereby shortened, resulting in a reduction of the prestress below a minimum value, which requires the working doctor to be reset or, if there is no resetting option, to be renewed.
The working doctor can be reset by resilient elements, which press the doctor blade, which is resettable in a guide, against the ink-carrying roller, and thereby automatically compensate for the wear of the doctor blade. However, in this regard, the difficulty arises of adapting the setting force provided by the resilient elements to the changing operating conditions of the printing machine. When the printing machine is stopped, the working doctor must initially be set against the roller, it being necessary for the doctor blade to be pushed back in the guide counter to the setting force of the resilient elements, and to prevent the doctor blade from bending. In order to doctor or squeeze off the surface of the ink-carrying roller cleanly, the working doctor must lie on this roller at a given angle. If this angle is chosen too small, i.e., the doctor blade lies too flat on the roller, the doctor blade can then slip on the surface of the roller and be reset to too great an extent by the maximally outsprung resilient elements, so that the surface is doctored or squeezed off rather poorly. If, by contrast therewith, the angle between the doctor blade and the surface is chosen too large, the doctor blade is then pushed back in the guide, due to the higher dynamic pressure of the ink resulting therefrom, and the doctoring result is likewise impaired. The permissible angle between the doctor blade and the roller therefore lies in a narrowly limited angular range, and the setting force provided by the resilient elements must correspondingly lie in a likewise narrowly limited range. When the printing speed is increased, however, the dynamic pressure of the ink increases, and the doctor blade is pushed back in the guide counter to the setting force of the resilient elements, due to which the doctoring result is impaired.
As a result of the penetration of the ink into the doctor guide and the drying of the ink therein, the frictional force of the doctor blade in the guide is increased, causing the setting force to be reduced and the doctoring result to be impaired likewise. It is therefore not possible to set the doctor blade at the correct angle against the ink-carrying roller in all the operating conditions of the printing machine, by using the resilient elements.
The published German Petty Patent Document DE 92 16 754 U1 describes a doctor bar in a short-form inking unit, which has a device comprising a base member and a working doctor, which permits the working doctor to be pressed controllingly against an engraved or screen roller at a negative setting angle. In the described device, the working doctor is set manually against the engraved or screen roller on a straight line extending parallel to the setting angle of the doctor blade.
With the aid of springs or hydraulic or pneumatic operating cylinders, continuous resetting is achieved during the operation of the printing machine, the service life of the doctor blade being thereby increased. In this case, the problems mentioned hereinabove regarding the force-controlled setting of the doctor blade against the engraved roller occur.
In the published German Patent Document DE 44 25 478 A1, a chamber-type doctor device is shown wherein a working doctor is fixed to a holder that is mounted so that it is pivotable on a chamber-type doctor member, the working doctor being pressed against a cylinder due to the exertion of a force upon the pivotable holder by a spring.
Because no guide slot is required for the doctor blade in this construction of the chamber-type doctor device, it is not possible for the doctor blade to stick in a guide slot and, consequently, for a reduction in the setting force to occur. However, the aforementioned problems occurring during the setting of the working doctor and at variable printing speeds exist, nevertheless, as before.
One solution of the problem would be to press the working doctor against the roller by resetting or adjusting screws, so that the doctor blade is prevented from being sprung out or pushed back uncontrollingly, because the doctor blade is held in the guide thereof in a position permanently defined by the resetting screws. However, the pressman must then be given the possibility of monitoring or controlling the attrition of the doctor blade caused by the wear, in order to reset the doctor blade manually, as required.
Hereinafter, reference to an inking unit with an engraved or screen roller should always be considered to be by way of example. The invention, however, is not restricted to inking units with an engraved or screen roller, but is also installable, for example, in inking units with a gravure printing roller.
SUMMARY OF THE INVENTION
Thus, there is provided, in accordance with the invention, a doctor device in an inking unit of a rotary printing machine, which has a simple construction and with which it is possible for a pressman to determine the then-occurring wear of the working doctor in a reproducible manner, and to facilitate the tracking of the working doctor into an optimal operating position.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a doctor device in an inking unit of a rotary printing machine, having a base member, and a working doctor adjustable with respect to the base member, comprising a sensor for determining a position of the working doctor relative to the base member.
In accordance with another feature of the invention, the sensor includes a first electric circuit, the position of the working doctor relative to the base member being determinable by respective opening and closing of the first circuit.
In accordance with a further feature of the invention, a contact is included in the first circuit for closing the first circuit when the working doctor is in a first nominal or desired position.
In accordance with an added feature of the invention, the contact is located on a side wall of the base member.
In accordance with an additional feature of the invention, the first circuit includes a first indicating device, which is activated when the first circuit is closed.
In accordance with yet another feature of the invention, the first indicating device is a control lamp.
In accordance with yet a further feature of the invention, the sensor includes a second electric circuit, the first circuit being closed and the second circuit being open when the working doctor is in a first nominal position, and the first circuit being open and the second circuit being closed when the working doctor is in a second position.
In accordance with yet an added feature of the invention, the first circuit has assigned thereto a first measuring finger with a first contact, and the second circuit has assigned thereto a second measuring finger with a second contact, the first measuring fin
Greenberg Laurence A.
Heidelberger Drückmaschinen AG
Locher Ralph E.
Nguyen Anthony H.
Stemer Werner H.
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