Knurled roller film transport and realted method

An apparatus is provided for scanning a photographic film or the like with a laser beam. The apparatus includes a roll source or cassette of film to be supplied and used and a take-up cassette to receive the exposed film in the form of a roll. Between the source of the film and the take-up cassette there is provided an arrangement consisting of one or two knurled segments or rollers which peripherally engage the film along the lateral edges thereof in order to transport the film past a laser beam generator and scanner adjacent which the knurled roller or rollers are positioned in order to draw the film at a closely controlled rate past a slot through which the laser beam exits in order to photographically process the film. Between the knurled roller or rollers and the take-up cassette are provided exit rollers which engage the film at a slightly faster speed than the speed at which the film is travelling. The exit rollers are arranged to engage the film with a force of about 21/2-4 pounds. The take-up cassette is provided with a slip clutch in order to compensate for the buildup of film on the roll as the process progresses. The source cassette is provided with lips which engage the film and which serve as a light seal. These lips also provide a drag on the film to prevent the film's being freely spooled out without control.

FIELD OF THE INVENTION 
This invention relates to laser imager arrangements and methods and more 
particularly to apparatus for the transportation of photographic film and 
the like including the supply, transportation and take-up of the same. 
BACKGROUNDS OF INVENTION 
In, for example, the scanning of photographic film or the like by laser 
beams to deposit pixels on the film, there is sometimes a very serious 
need for exceptional registration. This registration refers to the ability 
to establish on the photographic film pixel positions which are repeated 
with respect to a sequence of sheets which may subsequently be used 
cooperatively to form a composite image. Thus, for example, in the 
formation of a composite image with a plurality of colors these colors 
must be accurately placed on respective of a sequence of sheets in order 
that they can become properly combined to produce cooperatively a 
composite arrangement of colors. Such colors may also have to be aligned 
with a black and white arrangement which constitutes a text thus providing 
a further need for exceptional registration. Registration has to be 
effected between the pixel positions themselves which in turn may be 
registered relative to targets positioned on the respective sheets. These 
targets may take the form of cross lines arranged in the form of a plus 
sign or an X. 
The achieving of registration has always been elusive and erratic in roll 
fed images. This has been due to the fact that using rollers to grab film 
requires high pressures and usually a large wrap around relative to the 
drive roller thus causing dimensional deformation of the photographic 
media or film (actually the medium can be film, photographic paper, or 
paper or plastic plate material). The reason that good registration is 
desired for roll fed images is that roll fed devices are inherently much 
faster than the other devices now used to obtain good registration. These 
other devices include sheet fed devices using drums or flat beds with 
various clamping means such as vacuums or pins, or quasi-sheet fed devices 
wherein sheets are pre-cut from a roll and then clamped by various means 
such as mentioned above. 
Another reason for the desire to obtain good registration with roll (or 
web) fed devices is that good registration is required for the production 
of color separations in color printing. The use of known drum or flat bed 
devices to produce color separations is slow, therefore encouraging the 
use of roll fed images to produce black and white images and types on 
pages. This requires that the color picture and the type be then merged by 
cutting and pasting (a process known as stripping), and then photographing 
the merged page to create the separation plates for printing. This is 
labor intensive, consumes time, and consumes material (i.e., film) all of 
which is costly. 
By using a roll fed imager capable of good registration, it is possible not 
only to produce type and color separations with the same imager, but also 
to produce them merged on the same page, thereby totally eliminating the 
stripping process. In addition, since roll fed devices are fast (that is 
why they are usually used to produce black and white and type), this 
registration capability makes it possible to produce color as well as 
black and white very quickly. This is particularly important in high 
production environments such as newspapers (which are steadily progressing 
to the use of color pages). 
Photographic film and paper used for phototypesetting and other image 
recording applications as discussed herein include various typical 
commercial brands such as Kodak "Pagi Set" or Kodak Helium Neon Laser Film 
2692, DuPont "Cronatype", or DuPont Helium-Neon CRT Film(CHC-4), 
Paper(CHE-P), Chemco "Powermatic", and Amitec "Reprotype". 
SUMMARY OF THE INVENTION 
It is an objective of the invention to provide an improved laser beam 
imager. 
It is yet another object of the invention to provide an improved method of 
laser beam imaging. 
Still another object of the invention is to provide improved apparatus for 
the improved transportation of photographic film or the like in 
association with laser beam imaging and other similar types of operations. 
It is yet another object of the invention to provide improved methods 
relating to laser beam imaging processes and the like. 
Yet another object of the invention is to provide for improve registration 
during laser beam imaging and the like. 
It is still another object of the invention to provide for improved supply 
and take-up procedures relative to a laser beam imaging procedure having 
exceptional registration. 
In achieving the above and other objectives of the invention there is 
contemplated in accordance therewith the provision of an apparatus which 
comprises a source of film, said film including a base and a laser 
sensitive material on the base with a film take-up means being provided 
for collecting the film preferably in the form of a roll. Further provided 
is a laser arrangement for scanning the film with a laser beam during 
movement of the film from the source to the take-up means. This movement 
may be continuous or intermittent and adjustment may be made in the supply 
of information by means of the laser beam to account for either continuous 
or intermittent movement of the film. The movement is controlled by at 
least one knurled roller or the equivalent thereof for engaging the film 
and drawing the same from the source. The roller is in accordance with the 
invention positioned to engage the film along at least one lateral edge of 
the same. Preferably the engagement is made by a pair of knurled rollers 
positioned to engage the film along the spaced lateral edges thereof. In 
further accordance with a feature of the invention an idler roller 
including a resilient surface is provided which sandwiches the film 
against the knurled roller. An arrangement is provided to positively drive 
the knurled roller to transport the film past the laser arrangement. In 
understanding the scope of the invention, it should be noted that 
reference is made herein to a photographic film. Other materials can 
similarly be transported in accordance with the invention such as 
photographic paper or paper or plastic plate material. It will thus be 
understood that when film is referred to in this text that the equivalent 
materials are also intended to be covered. 
According to further features of the invention the knurled roller is 
prepared in order to provide a multiplicity of "pins". Thus, when 
reference is made to a knurled roller it is intended that equivalent 
structures also be included within this expression. The knurled roller of 
the invention will preferably have a knurl pitch in the order of magnitude 
of 40 per inch. This may include for example a magnitude of from 15 to 60 
per inch. Under certain circumstances this magnitude may be greater or 
lesser than the indicated amount provided that an appropriate registration 
ensues from the structure which is employed. The knurl pitch mentioned 
above is defined by intersecting grooves forming angles arranged at for 
example a range of 30 to 60 degrees to the axis defined by the associated 
roller. The grooves will preferably form knurls of a diamond-shaped cross 
section. 
According to a further feature of the invention opposed exit rollers on 
opposite sides of the film are arranged between the knurled roller or 
rollers and the take-up arrangement. A drive arrangement is provided to 
drive one of the exit rollers and a weight or the equivalent is provided 
to apply a force of about 2 1/2 to 4 pounds against the other of the exit 
rollers to press the other of the exit rollers towards the first mentioned 
exit roller. 
According to a further feature of the invention the laser arrangement may 
include a casing provided with a slot through which the laser beam exits 
to traverse and process the film photographically. This slot is preferably 
arranged at a distance of no more than about one to three inches from 
where the film is engaged by the knurled roller or rollers. According to 
yet another feature a pressure plate having a flat surface resting on the 
film over the aforementioned slot may be provided to flatten the film over 
the sam and to contribute to the exceptional registration. 
In accordance with the invention the aforementioned source of film or the 
like may include a roller on which the film is wound, a casing within 
which the roller is mounted and which is provided with a slot for the 
exiting of the film, and pressure lips adjacent the slot to create a drag 
on the film exiting from the casing while providing furthermore for a 
light seal to prevent premature photographic modification of the film. The 
source may moreover include a roller to support the film preferably in the 
form of a roll although other forms of supply such as pleated webs may 
also be employed. In accordance with the invention a friction brake is 
also provided to prevent uncontrolled spooling off of the film from the 
aforementioned roll. 
According to yet another feature of the invention a roller is also provided 
within the take-up means to collect the film in the form of a roll with a 
drive being provided to drive the further roll and a slip clutch 
arrangement being provided coupling the latter said drive to the roll in 
the take-up arrangement without stretching or breaking the film and to 
provide for compensating the accumulation of film on the roller at greater 
and greater radii. 
According to yet another feature of the invention the driven exit roller is 
driven with a peripheral speed which is slightly faster than the available 
speed of the film and such that the driven exit roller slips on the film. 
It will be noted that the drive for the further roller in the take-up 
arrangement and for the driven exit roller may include a common gear 
train. 
According to features of the invention relating to the knurle roller or 
rollers it will be noted that the roller will preferably have an outer 
diameter in the order of magnitude of about 1.440 inches and that the 
roller or rollers are knurled to cover an axial extent in the order of 
magnitude of about 0.500 inches. It will also be noted that the film is 
transported past the laser arrangement with the emulsion side down and 
that the knurled roller or rollers engage into the emulsion side of the 
film. It will also be noted that the slip clutch arrangement in the 
take-up cassette includes an approximately 5 oz. - inch slip clutch 
arrangement. 
In the description of a detailed embodiment which follows hereinafter it 
will be noted that the film is divisible into sheets each of which is 
provided with at least one target. Preferably three targets are provided 
which are preferably in the form of a cross hair arrangement or an X. The 
film is preferably such as to have a mylar or polyester base and the film 
is preferably of a thickness in the order of magnitude of about 4 mils. 
In accordance with still another feature of the invention the grooves which 
are employed to provide the knurled roller with a plurality of pins will 
have a substantially uniform depth of about 0.005 to 0.003 inches. Such 
grooves will define knurls preferably having a pyramidal shape with a 
diamond-shaped cross section. The knurled roller or rollers are preferably 
driven at a constant angular velocity which may preferably be derived from 
the common gear train mentioned hereinabove. 
As has been noted hereinabove the invention also provides to be a method. 
This method may be considered a method of exposing a film to a 
transversely scanning laser beam to secure a plurality of exposures in 
close registration with one another (or with the targets mentioned 
hereinabove), the method comprising driving the film past the laser beam 
at a constant speed by engaging the film with at least one knurled roller 
or the equivalent thereof driven at a constant angular velocity. The film 
is preferably supplied from a supply roller although a pleated web or the 
equivalent may also be employed and taking the film up on a take-up 
roller. The knurled roller engages the film edgewise between the supply 
and take-up rollers o the equivalents thereof. 
In accordance with further features of the method of the invention the film 
is preferably engaged with knurled rollers along opposite lateral edges of 
the film to an extent of about 0.100 to 0.350 inches at each of the 
aforementioned edges. The film is preferably forced against the knurled 
roller with a force that forces the knurls or pins into the film. 
Other features of the invention comprise further driving the film between 
the knurled roller and the take-up roller by engaging the film with a 
driven roller the peripheral speed of which exceeds the speed of the film 
so that the driven roller slips on the film. The peripheral speed of the 
driven exit roller may exceed the speed of the film preferably by a 
magnitude of approximately 5-20%. 
In yet another feature of the invention a drag is applied to the film 
supplied by the supply roller to prevent a free spooling off of the film. 
According to yet another feature the take-up roller is driven through a 
slip clutch to compensate for the building up of the film on the take-up 
roller. 
Other features include urging the film against the driven exit roller with 
a force of about 21/2 -4 pounds and knurling the knurled roller with two 
groups of intersecting parallel lines forming diamond-shaped pyramidal 
pins. 
The above and other objects, features and advantages of the invention will 
be found in the detailed description which follows as illustrated by the 
accompanying drawing.

DETAILED DESCRIPTION 
The primary method of a present invention is the method of firmly holding 
and moving film. In this method a knurled segment of steel or the like on 
a drive roller grabs the film and holds it against a pressure roller or 
idler. The pressure roller is preferably coated with a hard rubber or a 
rubber-like material but a metal roller would also work. The knurl presses 
into the film and actually pins it against the pressure roller, producing 
what may be called "microsprockets" (many tiny points of very firm 
contact). The knurled segments are preferably located at both edges of the 
drive roller in order to hold firmly both edges of the film width, but 
experimental results have shown that, with the use of narrow film which 
can only be grabbed by one knurled segment or roller, the results are also 
good. When two knurls or knurl segments or rollers are used, the rollers 
must be made precisely so that they are round and have the same diameter. 
There are two supplemental features that are required in order for this 
invention to give optimum results. 
1). Supply Roll Drag 
There must be sufficient drag in the associated supply cassette to prevent 
the film roll from spooling out. The percent change in drag must be 
minimized between an almost full and almost empty supply roll of film. The 
tension on the film speed to the drive roller from the supply cassette is 
accomplished by the following: 
(a) The friction of the felt lips at the exit slit of the supply cassette 
casing (which is primarily used for a light seal). 
(b) The friction or slip clutch mechanism sides of the supply cassette 
which prevents the film roll from spooling out. In particular a plastic 
cup rubbing against the inside wall of the supply cassette acts as a 
friction load. 
2). The take-up side 
(a) Take-up cassette 
The takeup cassette has a driven roller. The roller is driven at constant 
angular velocity. The value of angular velocity must be high enough at the 
start of take-up so that the film is pulled tautly around the take-up 
cassette spool because, if it isn't, it will back up and cause film jams. 
On the other hand, as more of the film is wound onto the take-up cassette 
spool, the surface speed of the film increases. In order to avoid this 
causing of excessive pull on the film which would exert excessive force on 
the drive roller (which in turn would disturb good registration), a 5 
oz.-in. slip clutch limits this force as the roll gets larger while at the 
same time winding the film tautly at constant tension on the take-up 
spool. 
(b) Exit Rollers 
In order to isolate the engagement of and disengagement of the slip clutch 
in the take-up up cassette from affecting the accuracy of the knurled 
drive roller and its grabbing of the film, friction rollers with a force 
of between 2 1/2 and 4 pounds pressing on the film surface are employed. 
They are located between the drive roller and the take-up cassette and are 
driven slightly faster than the film so that they slip on the film 
surface. 
FIG. 1 of the drawing is an overall schematic diagram of a laser scanner 
apparatus 20 (such as shown, for example, in U.S. Pat. No. 4,786,919, H. 
Bidner et al; Nov. 22, 1988) including laser scanner optics 22 and a film 
transport 24 provided in accordance with the invention. The laser scanner 
includes a casing 26 provided with a slot 28 through which exits a laser 
beam which traverses the film 30 being processed and deposits in cells 
thereon pixels which are closely registered in accordance with the 
invention as will be further discussed hereinbelow. 
The film transport 24 includes a supply cassette or source 32 and a film 
takeup cassette or arrangement 34. Intermediate the source 32 and the 
takeup arrangement 34 is a knurled roller or roller pair 36. This roller 
or pair of rollers includes a surface arrangement of pins 38 which press 
into the film 30 thereby engaging the same for driving the same in the 
direction of arrow 40. Urging the film downwardly against the knurled 
roller or pair of rollers 36 is a idler roller 42. This idler roller 42 is 
spring-loaded against or towards the knurled roller or pair of rollers 36 
by a spring (not shown) the force of which is indicated by arrow 44. 
Roller 42 is preferably formed with a metal core (not shown) and is 
provided with a rubberized or butadiene surface. This rubberized surface 
preferably has a Shore A durometer of 85 plus or minus 5. The surface is 
preferably of a non-marking type which does not deform and which resumes 
its normal shape when not opposed directly against the knurled roller 36. 
The function of the roller 42 is as indicated above to force the film 30 
against the pins 38 of knurled roller or segment 36 whereby the film can 
be engaged and driven in the direction of arrow 40. 
Knurled roller 36 and pressure idler roller 42 are also seen in FIGS. 2 and 
3 in somewhat enlarged scale. Therein is also seen the film 30. Although 
not illustrated the emulsion side of the film 30 is directed downwardly 
and is the side of the film which is engaged by the knurled knob 36. The 
film is for example in the order of magnitude of 4 mils. although this 
thickness can vary widely while being managed within the scope of the 
invention. It will be seen however that the film is engaged along a 
peripheral lateral edge thereof and preferably both peripheral lateral 
edges thereof at a distance E (see FIG. 3) in the order of magnitude of 
about 0.100-0.500 inches at each of the edges of the film. It will also be 
noted by reference to FIG. 1 that the points of contact of knurled roller 
36 with film 30 are located at a distance S from the center of slot 28 
through which the laser beam exits the casing 26, distance S being 
preferably in the order of magnitude of from about 1-3 inches. This 
normally leaves insufficient material between where the film is being 
photographically processed and where it is being transported by knurled 
roller or rollers 36 to affect the exceptional registration which the 
invention provides even though there may be some stretchability in the 
film material. 
In a preferred embodiment of the invention, the knurled knob has an axial 
extent E(FIG. 3) of about 0.500 inches and a diameter in the order of 
magnitude of about 1.440 inches which is preferably held to about plus, or 
minus 0.001 inches. The knurls or pins 38 themselves are formed by grooves 
which are in the order of magnitude of about 0.005 to 0.030 inches. These 
grooves are arranged in two groups of parallel alignment each of which is 
at an angle B (FIG. 4) of about 30-60 degrees. The grooves of one group 
are in intersecting to provide the pins or knurls 38 (FIG. 3) which are 
developed between the grooves and which are generally of diamond-shaped 
cross section section. The pins 38 are thus of pyramidal shape. These 
grooves are preferably pitch in an order of magnitude of 40 per inch, the 
preferred range of this pitch lying within 15-75 per inch in order to 
achieve preferred results. The material from which the knurled rollers are 
formed is steel which is preferably given a zinc dyed black finish. The 
cuts are made in the raw material to provide sharp edges. 
In association with the slot 28 in the casing 26 is a flat pressure plate 
60. This pressure plate has a lower surface 62 which is flat and planar 
and which rests on the film 30 as it passes over the portion of the casing 
26 which defines the slot 28. The function and weight of the pressure 
plate 60 is such as to flatten the film 30 over the slot 28 whereby to 
contribute to the exceptional registration provided in accordance with the 
invention. 
The supply cassette 32 illustrated in FIG. 1 of the drawing is shown 
further in FIGS. 5 and 6. Therein is seen the film 30 issuing from the 
cassette between lips 64 and 66. These lips are ordinarily intended to 
provide a light seal. However, these lips also engage the film 30 thereby 
to create a drag thereupon as the film moves in the direction of arrow 68 
towards the associated knurled roller arrangement. 
The film is supplied preferably on a roller 70 and thus is supplied in roll 
form. As has been discussed above the supply of film in roll form enables 
the process of the invention to be performed more rapidly. 
In further accordance with the invention and to further provide a drag 
preventing, uncontrolled spooling off of the film there is provided a drag 
or friction brake 72 of conventional type. This supply roll drag provides 
sufficient drag in the supply cassette to prevent the film roll from 
spooling out. The percent change in drag must be minimized between an 
almost full and an almost empty supply roll of film. The tension on the 
film feed to the slip clutch or slip brake mechanism inside of the supply 
cassette is intended to prevent a free spooling out of the film. In 
particular, a plastic cup P rubbing against the inside wall of the supply 
cassette can act as a friction member. A further feature of the invention 
mentioned hereinabove relative to FIG. 1 includes the exit rollers 80 and 
82. These exit rollers also appear in FIG. 7. The lower roller 80 is a 
driven roller. The upper roller 82 is an idler or idling roller. The 
function of the exit rollers is to isolate the engagement of and 
disengagement of the slip clutch in the take-up cassette and prevent the 
same from affecting the accuracy of the knurled drive roller or rollers. 
These rollers are provided with a weight 84 bearing down o the roller 82 
(and thus indirectly against roller 80) to apply force against and urge 
the same towards the film. FIG. 8 illustrates the take-up cassette 38 in 
some greater detail. Therein appears the roller 90 which takes up the film 
30 arriving in the direction of arrow 40. Thus the film is collected in 
the form of a roll to be subsequently processed in greater detail. In FIG. 
8 is illustrated the slip clutch 92 (such as, for example, appears in FIG. 
3, page 209, How Things Work, by R. Segalat, Vol. III, Simon and 
Schuster). It will be noted that the film 30 enters the cassette 38; on 
the other hand, as the film is wound in increasing amounts onto the 
take-up roller 90, the surface speed of the film increases. In order to 
avoid this accumulation of film from causing excessive pull on the film 
which would exert an excessive force on the roller 36 the clutch 92 is 
provided in the form of a slip clutch which limits the force as the roll 
gets larger while at the same time winding the film tautly in the 
preferred embodiment of the invention. 
FIG. 9 illustrates a section of the film 30 and particularly a sheet 100 
included therein. The registration is extremely important as each cell has 
to correspond with others on different sheets to provide for an 
appropriate mixture of colors. A digital control may be provided relative 
to the laser scanner 22 (FIG. 1) so that an appropriate half tone value 
will be provided for each cell or pixel. By matching up the targets a 
result within plus or minus 3 mils. can be achieved in accordance with the 
invention. In fact standards below plus or minus 2 mils. are readily 
achieved with values of 80 or 108 pica. Pressure bearing points resulting 
from the microsprocketing arrangement of the invention create a multitude 
of forces per unit area uniformly to avoid slippage in the main drive of 
the film being processed in accordance with the invention. 
The driven rollers mentioned hereinabove include the knurled roller 36, the 
exit roller 80 and the take-up roller 90 of the take-up cassette 34. These 
may all be driven through a common gear train T (see FIG. 1) which is 
illustrated merely diagrammaticaly as there is no special feature in this 
gear train other than its being provided (see, for example, the gear 
trains illustrated in FIGS. 2 and 3, page 197, How Things Work, Vol. III, 
Simon and Schuster Inc. 
From what has been stated hereinabove the method of the invention is a 
method of exposing film to a transversely scanning laser beam in 
accordance with one embodiment thereof to secure a plurality of exposures 
in close registration with one another. This method comprises driving the 
film past the laser beam at a constant speed by engaging the film with at 
least one knurled roller or the equivalent thereof driven at a constant 
angular velocity. The film is supplied from a supply roller and is in roll 
form and the film is taken up on a take-up roller preferably to form a 
roll. The knurled roller engages the film edgewise between the supply and 
take-up rollers. 
The method of the invention further includes engaging the film with knurled 
rollers along opposite lateral edges of the film to an extent of about 
0.100 to 0.350 inches at each of these edges. The film is forced against 
the knurled rollers with a resilient force that forces the knurls into the 
film. The method further comprises driving the film between the knurled 
roller and the take-up roller 80 by engaging the film with a driven exit 
roller the perpheral speed of which exceeds the speed of the film so that 
the driven roller slips on the film. The peripheral speed of the driven 
exit roller exceeds the speed of the film by about 2-20%. 
Further, the method of the invention includes applying a drag to the film 
supplied by the supply roller to prevent a free spooling off of the film 
and driving the take-up roller through a slip clutch to compensate for the 
building up of the film on the takeup roller. The film is urged against 
the driven exit roller with a force of about 21/2 -4 pounds. 
There will now be obvious to those skilled in the art many modifications 
and variations of the apparatus and method set forth hereinabove. These 
modifications and variations will not depart from the scope of the 
invention if defined by the following claims