Printing – Printing members – Rolling contact
Reexamination Certificate
1997-12-29
2001-09-11
Colilla, Daniel J. (Department: 2854)
Printing
Printing members
Rolling contact
C101S415100, C101S483000
Reexamination Certificate
active
06286427
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to printing press cylinders, particularly to the adaptation of cylinders originally designed for employment with a printing blanket lock-up device to make them suitable for use with adhesively-securable printing blankets.
2. Discussion of the Prior Art
A common means for securing an offset printing blanket onto a press cylinder employs a tensioning ‘lock-up’ device located within the cylinder body. The device is located in an axially elongate cavity extending into the cylinder body from the cylinder surface. The presence of this device causes a corresponding gap in the usable printing area of the cylinder and furthermore tends to promote undesirable vibration during operation of the printing press, especially at high-speed printing.
Recent developments in printing blankets promote the feasibility of employing a blanket secured to a printing cylinder by adhesive means. New cylinders for such blankets accordingly have a continuous unbroken surface, thereby increasing the usable printing area of the blanket and minimising potential vibration during running of the press.
However, printing cylinders, especially large cylinders of web-feed offset printing presses such as those used in the newspaper and magazine printing industry, are expensive and consequently substitution of a lock-up type of cylinder by a new continuous-surface cylinder is hampered by the entailed cost.
Also, the dismantling and reassembly of a press required for substitution of a printing cylinder is of high concern in the newspaper and magazine printing industry where a long down-time of the press could be highly detrimental to meeting distribution deadlines.
SUMMARY OF THE INVENTION
An object of the present invention is the provision of means for enabling an existing lock-up type printing cylinder to be used with a printing blanket secured by non-lock-up means.
A further object of the invention is the provision of means enabling an existing lock-up type printing cylinder to be adapted for non-lock-up securement of a printing blanket without removal of the cylinder from the press.
A further object of the invention is the provision of means for applying an adhesive-securable printing blanket to a printing cylinder originally designed for lock-up blanket securement.
According to one aspect of the present invention, for use in a printing press cylinder of the type having in its surface an axial cavity produced for location of a lock-up device for a printing blanket on the cylinder, there is provided means to adapt the cylinder for accommodation of a printing blanket without a lock-up device, said means comprising a fillet of shape for insertion into the cavity so as to bridge the cavity flushly with the cylinder surface periphery, said fillet having an arcuately curved bridge surface of the same radius of curvatures as that of the cylinder and having in its bridge surface a longitudinal slit for guidance of a knife edge.
According to the present invention also there is provided a printing press cylinder of the type referred to in the immediately preceding paragraph having, in its surface axial cavity, adapting means as defined in that paragraph.
The fillet should be secured in the cavity rigidly so that it does not loosen under the conditions of operation of the press. Securement may be attained by, for instance, adhesive bonding and/or mechanical securing means. Conveniently, at least some of the bolt-holes originally provided for securement of the lock-up device may be utilised for securement of the fillet.
In a preferred embodiment of the invention, the fillet is in two-part form, consisting of a lower part securable in the cavity by screw-threaded means entering the cavity base, and an upper part securable to the lower part and providing the arcuately curved bridge surface.
A preferred means for securing the upper and lower fillet parts together comprises mechanically interlocking complementary shape formations on the abutting surfaces of the parts. For instance, the top surface of the lower part and the bottom surface of the upper part may have mortise and tenon shape formations to form a dovetail joint.
The shape formation on the top surface of the lower fillet part may be discontinuous, such that there are shape formations for securing to the upper part and holes for accommodating screw-thread attachment to the cavity base positioned alternately along the length of the part. The top ends of the holes may be chamfered or rebated to accommodate the heads of the screw-thread means if desired. The shape formation on the bottom surface of the upper fillet part also may be discontinuous along the length of the part.
Securement of the two-part fillet in the cavity may be achieved by firstly inserting the lower fillet part down into the cavity and securing it therein such as by screw-thread attachment to the cavity base, then locating the upper fillet part on the lower fillet part such that there are alternate upper and lower part shape formations, and then sliding the upper part along the lower part to interlock the shape formations and form a rigid joint between the parts.
In one preferred embodiment, the interlocking shape formations may be longitudinally tapered so that they tighten together when the upper part is slid along the lower part.
A space left in the gap at the end of the upper fillet part may be filled with a correspondingly shaped block which may be secured therein such as by stud means.
A narrow slit is provided longitudinally in the top, bridge, surface of the fillet, for use as a guide channel for a knife edge. Preferably the slit is substantially parallel to the cylinder axis, but optionally it may be at a small angle to that axis. Typically the slit may have a width of the order of 0.5 to 1 mm and a depth of the order of 2 to 5 mm.
A printing blanket may be applied to a cylinder adapted in accordance with the invention from a blanket sheet of length greater than the cylinder circumference by steps comprising: (i) locating the leading end of the blanket sheet along the near edge of the slit or overlapping it; (ii) if necessary, trimming the located leading end of the sheet by running a knife edge along the slit (and removing the trimmed-off portion); (iii) wrapping the blanket sheet around the cylinder by rotating the cylinder as the blanket sheet is fed onto it until the sheet overlaps the slit; (iv) running a knife edge along the slit to produce a blanket trailing end which abuts accurately the leading end with negligible gap between them.
Thus, it is not essential to locate the leading end of a blanket sheet with high precision on the cylinder and it is not necessary to perform a blanket of length equal to the circumference of the cylinder. Moreover, a blanket may be applied to a cylinder without removing the cylinder from the press.
The invention is especially suitable for printing blankets to be secured on the cylinder by means of adhesive.
The adhesive employed for attaching a blanket to the press cylinder must be stable at the temperatures created during high speed running of the printing press and should be resistant to solvents employed for cleaning the blanket.
Preferably the adhesive should be such as to enable removal of a worn or damaged blanket by peeling off the cylinder with no or minimal adhesive residue left on the cylinder surface.
The adhesive layer should be of low thickness and of uniform consistency in order to avoid conferring even small aberrations on the total blanket thickness.
Accordingly, a contact adhesive usually is employed and typically such adhesives have a high initial bond strength which resists adjustment of the position of the blanket after contact with the cylinder. However, other types of adhesive, for instance a settable adhesive (e g heat- or radiation- settable) or a reaction adhesive (e g comprising a pressure-rupturable microencapsulated reactant), may be employed provided that they satisfy the requirements for a printing operations.
The adhesive typically is employed as a pr
Colilla Daniel J.
Duco International Limited
Grohusky Lelsie J.
Nixon & Vanderhye P.C.
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