Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 The present invention relates to printiny and in
particular to an apparatus for improving pre~press registration
between films and plates during the production of those plates.
The need for consistent registration is most marked
where full colour printing is required as each of four plates
must have their printing surfaces i.n precise register with
each other to avoid colour overprinting at the edges of colour
boundaries and so provide poor boundary definition on the
resultant colour ~rinted sheet.
Difficult problems of registration are discussed in
Australian Patents 404,967 and 462,212.
In the process of producing offset printing plates,
several complex steps have to be undertaken to arrive at a
single sheet of film, per colour to be printed, which is then
exposed direct to the printing plate.
Tn general the steps are as follows
1. A line negative is photographed from base artwork
to the desired size,
2. Four colour separations are produced by either
camera, enlarger or electronic scanning techniques and are
supplied in single sheet form per colour to the relevant size of
reproduction required, either from colour transparency, colour
prints or hard copy.
- 3. Using a predetermined layout as a guide, a sheet
of c~ear film is placed on a graph and a rule up is done.
Register marks, centre marks, trim, fold and perforation marks
are added, this step is done due to the need to have the job
exactly to correct size and square,
4. The line negatives are positioned on another sheet
of clear film which has been punched to the same configuration
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1 as the rule uP! -this allows register pins to hold each shee-t
in perfect register with each other t
5. I~ the job requires reverses, a sheet of light
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restraining paper is punched, relevant reverses cut out of
paper and this line negative with paper mask registered by
the pin register system is then contacted in a vacuum contact
frame onto a sheet of film (unexposed) that has also been
punched and is held in position by register pins during
exposure. Tbis exposed film is then developed either
manually or through an automatic film processor.
6. Where colour shots butt up to other colour shots or
where tints of colour meet, chokes and spreads have to be
produced to allow a degree of fit when making up final film.
In normal work screens with a line ruling of 150 lines to the
inch are used, sometimes 200 lines to the inch and fit is
only one line of dots.
7. Masks are cut manually using a material that when
the eumulsion is cut with a sharp blade, it can be peeled of~
from its clear film base.
8. Final film is produced manually by making multiple
exposures onto photographic film to produce a final sheet of
film that contains all the required elements, including four
colour pics, tints, reverses, chokes, spreads, line copy and
centre, trim, fold and perforation marks.
9. Final film (in the case of four colour process) are
then proofed, either by chemical proofing methods or plates
are made and ink proofs done.
In the multitude of sub straights or "flats", it may
require many exposures to produce one final negative or
positive, depending on the complexity oE the particular job.
It is, therefore, vitally important that the registration of
these various components be absolute. This is why a punch
register system is used. Punch register systems can take
many forms and have various punch hole configurations.
Most punch register systems available for use in the
dark room, or pre plate area, work on the principle of using
a round hole (or a series of round holes) on one side and a
slotted hole on the other side of a central position. These
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systems are not ideal, because when a register pin is placed
in the round hole, optimum registration takes place on and
from that round pin and any variation occurs towards the
slotted pin as the flat is pulled down in contact under
vacuum. This fault is amplified by the variety of
substraight ("flats") materials used in the process. ~ach
material, either paper, clear film, photographic film,
rubylith etc. all have their own dimensional stability
problems, each being effected by temperature and humidity in
various ways. Therefore the present invention provides a
punch that works from a round hole in the centre, with
slotted holes to both left and right to allow any shift in
registration to move equally from centre.
An additional problem is that while registration is
obtained along 'che punching side of the film/materials
(normally the longest side) there is no control over
registration on the shorter side. Therefore the present
invention provides a floating pin/punch. This additional
punch may be slid down a track, which is at 90 to the
front punching function, and is independant of the main punch
action. The action in total is as follows. The material to
be punched is placed in the punch knocking up to a back stop,
the main punch is operated, say, by depressing a handle, a
locking or pressure bar precedes the cutters to hold the film
flat across the punching head, the material is punched and
the cutters lock the punched material into the dies, the
portable or floating pin unit is then moved to the desired
position to accommodate the film size being used, a single
hole is then punched, preferably a slot hole. The punched
film is then placed into a vacuum contact frame and
registration pins are placed through the holes, the flat is
placed over the film and located by the pins, a cover sheet
is placed over and a vacuum applied so that when perfect
contact is achieved, an exposure is made. This exposure
process is repeated as many times as required depending on
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the number of flats to achieve the final result, all of these
flats are located by the register pins protruding through the
film. The completed, exposed film is ~hen processed. These
procedures are repeated for as many colours as are to be
printed.
It might be thought that the foregoing procedure
provides precise registration however further difficulties
arise. Printing machines are in use having di~ferent punch
registration systems fitted to their plate cylinder or plate
clamp bar, in the case of Web presses their plate bender, to
locate the plate in the correct position while the
positioning of the plate is of paramount importance if the
image or plate is not correctly in its position much time and
materials are wasted
To tie the final film into the same punching system that
appeL~s ~on ~ particular printing press requires a carrier.
(Me~nc.~ or similar material) is punched using the
particular machine punch system. A line is drawn on the
carrier to indicate grip edge folds and double cuts. The
negatives are taped to this carrier reading wrong emulsion
up. The carrier is turned over and a piece is cut out of the
carrier to expose the holes in the punched film and a
portable hole or tab is either taped to the back o~ the
carrier or is affixed by double sided tape.
Once this has been done the negatives or positives can
be removed and all negatives or positives that have been
produced using a constant punching configuration can be taped
to the carrier and plates can be made changing each negative
after exposure to plate and replacing the next negative on
the carrier using register pins to locate each negative in
the same position on the carrier. The latter process not
only involves a great deal of time but also creates another
process or step that could adversely ef~ect the register of
the ~inal image or plate; involves an extra surface for dust
and scratches to form and if the job comes back at any time
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1 in the future for a rema~e or alteration to any less than the
complete set o~ plates, no real conEidence could be afforded to
the carrier system due to temperature/humidity variations that
could have effected the positioning of the -tabs or holes on
the carrier sheet~
According to the invention there is provided apparatus
for punching materials used in the production of printing plates
and having a symmetrical punching configuration, the apparatus
comprising a central round hole punch positioned to punch one
edge of a material to be punched, and at least two slotted
hole punches provided one on each side of said central punch
and equally spaced from said central punch to punch said material
along said one edge, a position-adjustable punch adjustable in
a direction perpendicular to said one edge and disposed symmetri-
cally relative to said central punch and said slotted punches,
and plate configuration punching means operable in unison with
the operation of said central and slotted punches.
By this means final film can be produced which-is
punched to the same register configuration as on the printing
press. The application of common punching configurations so
as to produce punched film, punched proofs and punched plates
greatly facilitates the checking of the relative position of
the image before it goes to press; the edge of a proof is the
same as the edge of its respective plate,
Further, symmetrical punching allows double sided
proofs to be positioned with great accuracy,
The present invention will now be described by way of
example with reference to the accompanying drawing which shows
an exemplary punch con~iguration in accordance with -the
present invention.
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1 A preferred form of punch for producing the depicted
configuration is a hand operated deviee that punches or cuts
holes and slots of speciflc configuration oE the drawing figure
in all materials used in the pre~plate/sereen or eylinder area
of the printing industry. By the use of a handle or lever,
pressure is applied via an off--eentered cam
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to the various cutting or punch heads which are forced down
through the material being punched or cut and into a female
plate.
In the same action of the lever or handle, a flat bar or
pressure plate moves down ahead of the cutting or punch heads
and rests on top and in pressure contact with the material
being punched or cut. After the cutting or punching action
has been effected the spring loaded punching heads or cutting
heads become locked and can be released by additional
pressure on the handle or lever. The punching o~ cutting
function is mounted onto a flat base, in the center of which
is a track or slot that permits a single hand operated punch
or cutter to slide down the base board at ~0 to the
aforementioned punching function.
The punching configuration shown in the drawing is the
left hand side of the punch, the mirror ~everse of it
represents the right hand side. There~ore the punch is
completely symmetrical in its operation.
As shown in the drawing the cenral round hole 10 in
association with the slotted holes 11 provided each side of
the centre hole 10 provide for even expansion and contraction
either side of the central position. In addition adjustable
back slot 12 allows for film expansion and contraction in a
direction transverse to that of the front edge slots 11. The
remaining punch holes 13 coincide with varying punch systems
which are formed simultaneously with holes 10, 11.
A preferred punch of this invention would include a
vacuum drawn down system to ensure improved contact between
films which greatly assists in registration.
