Photocopying – Contact printing – With scanning
Patent
1998-01-14
2000-08-15
Metjahic, Safet
Photocopying
Contact printing
With scanning
358494, G03B 2710, H04N 104
Patent
active
06104475&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to apparatus for scanning a modulated light-beam across a photosensitive surface, and especially apparatus commonly known as platesetters, in which an image is scanned directly onto the photosensitive surface of a printing plate.
2. Description of the Background
The plates used in platesetters are generally made of aluminium sheet and are supplied in different sizes to suit different size printing jobs. In use, each plate is mounted on a scanning bed of the platesetter, which is typically a fixed concave bed to suit the curved focal plane of a particular rotary mirror, light-beam scanning system. The aluminium plates are thin enough to be flexible so as to conform to the concave shape of the bed, and are held in position by mechanical fastenings and/or pneumatic suction means.
The quality of the print image produced is principally dependent upon the accuracy of the light-beam scanning system, and this is why curved bed platesetters have been preferred. The productivity of a platesetter is dependent upon the speed of operation of the scanning system. However, the time taken in loading and removing plates from the bed also has a major effect on productivity and also effects quality adversely if the plates are not secured adequately, especially at the edges where their natural resilience can cause them to lift away from the bed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved platesetter, in particular, a platesetter with an improved plate handling system. Another object is to provide a platesetter which is adapted to serve the alternative function of scanning a modulated light-beam across a photosensitive film which is used in a separate process to produce a printing plate.
According to a first aspect, the invention consists in a platesetter having a flat bed, a light-beam scanning system mounted above the bed so as to scan a photosensitive plate on the bed, a store for photosensitive plates located beneath the bed, and feed means for feeding photosensitive plates from the store to the bed for scanning.
Preferably, the plates are stored upright in one or more cassettes beneath the bed, and the feed means selects plates as required from the cassettes and feeds each to a feed station along one side of the bed, from where the plate is fed horizontally onto the bed, preferably edge first with the leading edge generally normal to the feed direction.
It will be appreciated that by locating the plate store beneath the bed, a compact and convenient arrangement is achieved which readily facilitates loading of plates into the store from one side of the apparatus extending generally parallel to the feed direction.
According to a second aspect, the invention consists in a printsetter having a flat bed, a light-beam scanning system mounted to scan a photosensitive plate on the bed, a plate feed station located along a first side of the bed to feed photosensitive plates one at a time onto the bed in a first feed direction, and a film feed station located along a second side of the bed adjacent said first side to feed photosensitive film sheet onto the bed in a second feed direction transversely of sad first feed direction.
Preferably, the plates are stored upright in cassettes beneath the bed, and feed means selects plates and feeds them to the feed station. The cassettes are loaded beneath the bed along the same side as the film feed station so that the handling of the photosensitive media conveniently takes place in a common work area which may be incorporated in a "darkroom".
Preferably, the plates and film sheet are removed from the bed in said second feed direction so that they can be further handled or processed in the same work area.
According to a third aspect, the invention consists in apparatus for scanning a modulated light-beam across a photosensitive sheet, such as a photosensitive printing plate, comprising a flat bed to support said sheet, a light-beam scanning system to scan a photosensiti
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patent: 5038208 (1991-08-01), Ichikawa et al.
patent: 5049999 (1991-09-01), Stemmle
patent: 5291464 (1994-03-01), Osada
patent: 5905581 (1999-05-01), Suzuki et al.
Cook Paul Christopher
Dresch Alan
Neilson Peter John
Smith Stephen Clifford
ICG Limited
Metjahic Safet
Nguyen Hung Henry
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