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Claims  |
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Having described the invention, what is claimed is the following:
1. An intaglio printing press comprising:
frame means;
two slide members slidably mounted upon said frame means;
first and second shafts mounted on said frame means in approximately
parallel spaced relationship with each other, each of said shafts having a
cantilevered free end projecting from the same side of said frame means,
said first shaft being fixedly mounted to said frame means and said second
shaft being mounted to each of said slide members;
a pair of rollers, including a print roller and an impression roller, each
being rotatably mounted to the free end of a different one of said shafts
and each positioned to make rolling contact with a web of printing
substrate moving therebetween; and
means for shifting said slide members relative to said frame means for
deflecting said second shaft toward said first shaft to drive said rollers
together to exert printing pressure upon said web.
2. The intaglio press of claim 1 wherein said slide member shifting means
includes a pair of hydraulic rams mounted upon said frame means each
connected between said frame means and a different one of said slide
members.
3. The intaglio press of claim 1 further comprising:
mounting means, including a pair of spherical bearings, one mounted around
each of said cantilevered free ends of said shafts within the roller
mounted thereon, for supporting said rollers on said shafts so as to allow
said rollers to rotate thereon and to tilt thereon to allow the angle
between the axis of the roller and of the shaft to vary and thereby to
maintain a parallel relationship of one roller with the other at the
printing nip.
4. The intaglio press of claim 1 further comprising:
a pair of adjustable wedges mounted on said frame means between the slide
and said frame means, each of said wedges being movable in a direction
transverse the direction of movement of the slide members and operable to
regulate the spacing of each slide member with respect to the frame means
on which it is mounted, and thereby the deflection of said second shaft
with respect to said first shaft, to regulate the amount of printing
squeeze on the paper web.
5. An intaglio printing press comprising:
a frame including a pair of stationary frame members, each having a slide
member slidably mounted thereon;
a pair of cylinder support shafts mounted on said frame in approximately
parallel spaced relationship with each other, each extending between said
frame members and having a cantilevered free end projecting from said
frame, one of said pair of shafts being rigidly mounted to each of said
frame members, the other of said shafts being rigidly mounted to each of
said slide members;
a pair of rollers, including a print roller and an impression roller, each
being rotatably mounted to the free end of a different one of said shafts
and each positioned to make rolling contact with a web of printing
substrate moving therebetween;
means in engagement with said slide members for urging said shafts toward
each other thereby causing said rollers to apply printing pressure to said
web; and
mounting means for each of said rollers, said mounting means including
spherical bearings mounted around one of said cantilevered free ends of
said shafts within the roller mounted thereon, for supporting said rollers
on said shafts so as to allow said rollers to rotate thereon and to tilt
thereon to allow the angle between the axis of the roller and of the shaft
to vary.
6. An intaglio printing press comprising:
a frame including a pair of stationary frame members, each having a slide
member slidably mounted thereon;
a pair of cylinder support shafts mounted on said frame in approximately
parallel spaced relationship with each other, each extending between said
frame members and having a cantilevered free end projecting from said
frame, said pair of shafts including a fixed shaft rigidly mounted to each
of said frame members and a movable shaft rigidly mounted to each of said
slide members;
a pair of rollers, including a print roller and an impression roller, each
being rotatably mounted to the free end of a different one of said shafts
and each positioned to make rolling contact with each other and with a web
of printing substrate moving therebetween;
means connected between said slide members and said frame for urging said
shafts toward each other thereby pressing said rollers together to apply
printing pressure to said web; and
a pair of adjustable wedges, one mounted on each of said frame members
between the slide and the frame, and each movable thereon in a direction
transverse the direction of movement of the slide members on the frame,
and operable to regulate the spacing of each slide member with respect to
the frame member on which it is mounted and thereby the deflection of one
shaft with respect to the other at the respective members, so as to
control the tilting of one shaft with respect to the other and thereby
limit the printing pressure exerted upon said web by said rollers.
7. An intaglio printing press comprising:
a stationary frame;
a pair of shafts mounted in approximately parallel spaced relationship to
each other on said frame, each of said shafts having a cantilevered free
end projecting from said frame;
a pair of rollers, including a print roller and an impression roller, each
being rotatably mounted to the free end of a different one of said shafts
and each positioned to make rolling contact with a printing substrate
moving therebetween; and
means on said frame for shifting at least one of said shafts with respect
to said frame so as to urge the free cantilevered ends of said shafts and
the roller mounted thereon toward the other of said rollers to thereby
exert high printing pressure on the substrate between said rollers.
8. The intaglio press of claim 7 wherein each of said shafts and each of
said rollers has an axis, and said press further comprises:
bearing means, carried on the free cantilevered ends of each of said shafts
and rotatably supporting said rollers near their centers on said
cantilevered ends, said bearing means permitting the axes of said rollers
to freely tilt toward parallel relationship with each other in response to
the distribution of printing pressure across the width of said rollers and
said substrate.
9. The intaglio press of claim 8 wherein said bearing means include a pair
of spherical bearings, one mounted around each of said cantilevered free
ends of said shafts within the rollers mounted thereon, and each operable
to support the roller and allow the roller to rotate about the axis of the
shaft and to allow the angle between the axis of the roller and of the
shaft to change in response to unbalanced pressure distribution between
said rollers across the width of the substrate.
10. The intaglio press of claim 7 further comprising adjustable stop means
for limiting the deflection of one of said shafts and to thereby control
the orientation of the shafts with respect to each other.
11. The intaglio press of claim 10 wherein each of said shafts is
interengaged with said frame at at least two spaced points along said
shafts, one of said shafts being deflectably mounted with respect to said
frame at at least one of said points, said press further comprising a
movable mechanical stop for limiting the deflection.
12. The intaglio press of claim 10 wherein at least one of said shafts is
movably mounted to said frame so as to move toward and away from the other
of said shafts, said press further comprising a movable wedge positionable
between the movable shaft and said frame to limit the relative movement of
the shafts to thereby limit the force exerted between said rollers and
upon said substrate.
13. The intaglio press of claim 9 wherein each of said shafts is supported
at at least two spaced points along said shafts, one of said shafts being
movably mounted to said frame at at least one of said points so as to move
toward and away from the other of said shafts, said press further
comprising a movable wedge positionable between the movable shaft and said
frame to control the tilt of the movable shaft with respect the other to
regulate the printing pressure exerted on the substrate by said rollers.
14. In a method of intaglio printing, the steps of:
supporting a pair of shafts cantilevered from a stationary frame whereby
each of said shafts has a free end in approximately parallel spaced
relationship to each other;
supporting a print roller and an impression roller, each to the free end of
a different one of said shafts and positioned to make rolling contact
across their widths with a substrate web moving therebetween; and
applying a force to one of said shafts remote from the free end to
angularly displace said shaft with respect to the other of said shafts and
to urge its free end toward the free end of the other of said shafts to
force said rollers together against said web to exert high printing
pressure therebetween.
15. In a method of intaglio printing, the steps of:
supporting a pair of shafts cantilevered from a stationary frame whereby
each of said shafts has a free end in approximately parallel spaced
relationship to each other;
supporting a print roller and an impression roller, each to the free end of
a different one of said shafts and positioned to make rolling contact
across their widths with a substrate web moving therebetween;
applying a force to one of said shafts to urge its free end toward the free
end of the other of said shafts to force said rollers together against
said web to exert high printing pressure therebetween; and
said rollers being supported near their centers on said cantilevered ends,
and freely tilt toward parallel relationship with each other in response
to the distribution of printing pressure across the width of said rollers
and said substrate. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The present invention relates to the art of printing and more particularly
to the support of interchangeable printing cylinders on intaglio printing
presses used in high pressure printing processes.
BACKGROUND OF THE INVENTION
Intaglio printing is a process by which a printed image is formed upon
paper or other printing substrate material by passing the material,
frequently in web form, between a pair of press rolls. In the process, the
rolls are thrust together under high pressure to compress the substrate
therebetween to transfer ink from an inked image on an engraved or etched
plate cylinder or sleeve carried by one of the rolls to the substrate
surface. High pressure processes of this type include rotogravure printing
processes in which a high resolution plate is made to carry an inked image
in recesses engraved into the plate surface from which the ink to be
pressed from the grooves when the plate is brought into high pressure
contact with the paper. The use of the extreme pressure facilitates the
transfer of ultra high resolution line images to the paper. Such processes
are useful in printing money and other certificates where the printing
must be of extremely high quality.
Intaglio presses employ a pair of rollers or printing cylinders, including
a plate cylinder which carries the image to be transformed to a paper
substrate, and an impression cylinder which underlies substrate and forms
a supporting surface against which the plate cylinder presses the paper
during printing. In the printing process, high pressure is exerted upon
the paper by the pair of cylinders compressing it from opposite sides.
In fine quality, high resolution intaglio printing processes such as those
employed for the printing of currency, bank notes and the like, these
pressures may be exceptionally high, even up to 10,000 pounds per linear
inch across the width of the print rolls. The maintenance of a uniform
high pressure across the width of the rolls is important to the production
of high resolution, high quality printed images. This requires that the
roller supporting structure be such that the contact between the
impression and plate cylinders be maintained uniformly across the width of
the rollers as they contact the substrate.
The response of the prior art to the need to provide high uniform pressure
across the width of print rolls has been to apply, and control the
application of, force at least at both ends of the printing cylinders or
press rolls, and often to exert force on the rollers at multiple points
across the width of the printing surface. The direction of the prior art
has been to subject the rollers to a distributed or multipoint force,
acting upon the rollers, which produces a certain amount of undesirable
roll deformation, and to further distribute or modify the force to correct
for the deformation of the rolls. Such deformation, if produced and
uncorrected, results in the unwanted non-uniformity of printing pressure
across the width of the rolls. The structures employed to correct the
deformation have been complex and less then totally effective.
Another problem with prior art intaglio presses has been the time required
to service the printing rolls. These rolls must be removed for periodic
maintenance and to permit replacement of the impression sleeve carried by
the impression cylinder. The sleeves are subject to heavy wear and in some
installations must be replaced as often as every two days. Prior art roll
constructions have required an excessive amount of time to change rolls.
For example, in a typical press, a half a day is required.
For small article low pressure printing and embossing processes, printing
presses have been provided with a printing roller rotatably mounted to a
shaft which are supported to a frame at one end. Such presses for example
are shown in Hale U.S. Pat. No. 573,407, Sherwood U.S. Pat. No. 720,629,
Barton et al U.S. Pat. No. 1,599,868, Price, Jr. et al U.S. Pat. No.
3,405,633, Heuss U.S. Pat. No. 4,188,874, and German U.S. Pat. No.
687,191. Such methods of supporting rollers in a printing press upon a
cantilevered shaft provides for easier means interchanging of the plate
cylinders than where rollers are mounted to shafts supported at both ends.
However, the mounting of cylinders in cantilevered fashion has never been
successful to support rolls for high pressure engagement as is required
for intaglio printing.
One proposed intaglio press construction using cantilevered rolls is
disclosed in Heuss U.S. Pat. No. 4,188,874. In the press disclosed in that
patent, one or both of the press rolls are cantilevered. However, no means
is provided for applying forces to the roller shafts to shift the shafts
relative to one another to create a high printing pressure. Rather, a
special roll referred to as a pressure equalization roll is employed as
one of the rollers. The pressure equalization roller uses internal
hydraulically actuated supporting elements in order to distribute the
pressure across the width of the roller to compensate for roller
distortion. This construction is not a practical approach to providing a
high pressure intaglio press with a uniform pressure across the rollers.
Prior art press construction has also employed a variety of roll mounting
devices used in such a way as to affect the roll positions. Several
printing presses, for example, have employed pressure roller sleeves
supported by a multiplicity of bearings disposed adjacent to the
longitudinal axis of the roller to support the cylinders on the shafts.
Such presses are shown in Hornbostel U.S. Pat. No. 3,161,125, McDermott
U.S. Pat. No. 3,561,658, Pflaum U.S. Pat. No. 4,372,205, Maier U.S. Pat.
No. 4,438,695, George et al U.S. Pat. No. 4,487,122, and German
Offenlegungsschrift No. 2,849,202. In the presses described in such
patents, however, any uniformity of pressure between the mating rollers is
achieved by using roller supporting shafts mounted at both ends to a
frame.
Notwithstanding the state of the printing art, the high pressure presses
which have been developed to date have failed to provide for rapid and
easy interchange of printing rolls and plates. The problems of providing
uniform high pressure contact between the plate and the paper have
resulted in conditions which have aggravated the problem of roll
interchangeability. Accordingly, there exists a need for providing a
cylinder support for intaglio presses which will provide a uniform high
pressure across the rolls and which will provide rapid removal and
replacement of the rolls.
SUMMARY OF THE INVENTION
It is a primary objective of the present invention to provide an intaglio
printing press which is capable of performing high pressure printing
processes where the high pressure is applied to the print substrate
between a pair of printing rolls with a uniform distribution across the
width of the roll surface. It is a further objective of the present
invention to provide such an intaglio press in which the rolls are easily
accessible and can be removed and replaced with ease in a relatively short
time. It is an additional objective of the present invention to provide an
intaglio printing press which will economically and efficiently produce
high quality high resolution printed documents such as currency, bank
notes, and the like.
According to principles of the present invention, there is provided an
intaglio printing press having a pair of cylinders or rollers rotatably
mounted to a pair of approximately parallel shafts which are supported to
a rigid frame at only one side of the rollers. The rollers are mounted to
the free ends of the shafts in cantilevered fashion for easy
exchangeability. The high pressure contact between the rollers is achieved
by forces exerted on one shaft at the frame entirely to one side of the
rollers. These forces displace the shaft angularly with respect to the
stationary shaft. The rollers are supported to the shafts in such a way as
to allow them to tilt to accommodate any change in the relative angulation
of the shafts and thereby maintain a uniform contact pressure between the
rollers across their widths.
In a preferred embodiment of the present invention, the forces between the
opposed rollers are exerted in part by providing hydraulic rams or
cylinders which displace two movable slides. These slides carry the
journals in which the shaft of one of the rollers of the pair is mounted.
The hydraulic cylinders displace the movable shaft with respect to the
fixed shaft on which the other roller is mounted and which is rigidly
mounted to the press frame.
More particularly, in the preferred embodiment of the invention, the shaft
carrying the upper roller, is supported between front and back slides
which are carried by a fixed frame. The frame also supports the lower
shaft upon which the lower roller is mounted. The slides are
interconnected to the hydraulic cylinders which operate to shift the upper
shaft with respect to the lower shaft to apply squeezing pressure between
the rollers.
Also in the preferred embodiment, the rollers are supported on their
respective shafts so that they can undergo limited pivotal movement
relative to their mounting shaft. More particularly, the rollers are
mounted on spherical bearings interposed between the shafts and the
rollers to permit the rollers to not only rotate on the shafts but to
pivot to accommodate for any non-parallel orientation of the shafts. The
spherical bearings are preferably disposed on the shaft adjacent to the
axial center of the assembled rollers.
Further according to the preferred embodiment of the present invention,
wedges are provided between the slide and the frame in the front and rear
yokes to control the tilting of at least one of the shafts so as to adjust
the pressure distribution between the mating rolls.
In addition, in the preferred embodiment of the present invention, the
printing rollers are sufficiently narrow with respect to their diameters,
and sufficiently rigid, to resist local deformation of portions of the
rollers, and are mounted so as to move with respect to each other to self
align under the influence of the forces provided by their supports. The
two rollers are forced together under relatively high pressures of, for
example, up to 10,000 pounds per linear inch. This pressure is uniform
across the entire width of the rolls.
The principal advantage of the present invention is that the rolls so
supported are more accessible and can be replaced in as little as fifteen
minutes. This is a small fraction of the time in which the rollers of high
pressure intaglio presses could be replaced in the prior art. Further
advantages of the present invention are that high pressure printing is
achieved with pressures distributed uniformly across the rollers so that
high quality high resolution printing is accomplished. Furthermore, the
printing process can be carried out at high speed on a narrow continuous
web requiring only limited cutting to separate the finished product. The
invention is particularly advantageous for production of bank notes,
currency, and such high resolution items in multiple denominations and
large quantities.
The advantages of the present invention are in part achieved by providing a
mounting structure on one side of the rollers, including front and back
yokes, both of which are massive. The lower drive shaft which extends
horizontally outwardly from bearings carried by the pair of yokes. The
upper drive shaft extends outwardly from bearings carried by slides which
are slidably mounted to the yokes. These rollers bearings are subjected to
pressures exerted by hydraulic cylinders which shift the free end of the
upper shaft to press the upper roller against the lower roller. Spherical
bearings on which the rollers are mounted to the shafts allow the rollers
to shift to accommodate for any non-parallelism of the shafts. This
freedom of the roller axes to cant a limited degree ensures uniform
contact between the sleeves of the rollers across their width irrespective
of nonparallelism of the shafts. In addition, the cylinders are
proportioned so as to accommodate relatively large diameter shafts in
relation to the extended width of the printing cylinders. This, coupled
with the rigid construction of the cylinders on which the printing sleeves
are mounted prevents distortion of the printing surfaces and allows the
shaft canting ability to more fully adjust the pressure uniformly across
the printing width of the rollers. In addition, the relative inclination
of the shafts with respect to each other may be controlled by wedges which
can be shifted in and out under manual control to limit the printing
squeeze between the cylinders of the pair. This positioning of the wedges
limits the deflection of the shafts by the hydraulic cylinders and
provides ultimate limiting control of the printing pressure and relative
shaft orientation.
These and other objectives and advantages of the present invention will be
more readily apparent from the following detailed description of the
drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a preferred embodiment of an intaglio
printing press embodying principles of the present invention.
FIG. 2 is a cross-sectional view through the press roll cylinders of the
preferred embodiment of the press along line 2--2 of FIG. 1.
FIG. 3 is a cross-sectional view perpendicular to the axes of the cylinders
of the press along line 3--3 of FIG. 2 (viewed in the same direction as
FIG. 1).
FIG. 4 is a view, partially in cross-section and partially broken away as
seen generally along line 4--4 of FIG. 3.
FIG. 5 is a view along line 5--5 of FIG. 4.
FIG. 6 is a cross-sectional view along line 6--6 of FIG. 3.
DETAILED DESCRIPTION OF THE DRAWINGS
An intaglio printing press 10 constructed in accordance with the present
invention is illustrated in FIG. 1. The press 10 is particularly suited to
the performance of a high pressure intaglio printing process for the
printing of fine, high quality, high resolution images for currency and
the like. The press 10 includes a printing section 12 having a rigid
stationary frame 13, only the front portion 13a of which is visible in
FIG. 1, and a spool support section 14 having a rigid stationary frame 15
rigidly connected to the frame portion 13. Both of the frame sections 13
and 15 are supported on a plurality of adjustable feet 16. A vacuum
operated drying loop 17 is mounted to the end of the frame 15 of the spool
support section 14 to receive the printed web for drying. From the dryer
17, the web proceeds downstream to a wind up reel section (not shown).
The printing section 12 of the press 10 includes the print station 20 which
includes a plate cylinder roller assembly 21 and an impression cylinder
roller assembly 22 between which passes, at the juncture or printing nip
23 of the rollers 21 and 22, a continuous web 24 of print substrate or
printing paper. The web 24, during the printing process, continuously
moves downstream in the direction of the arrow 25 around a series of idler
rollers 26 each rotatably mounted on one of a plurality of cantilevered
shafts 27 each extending from the front side of the front portion 13a of
the frame 13 of the print section 12. The continuous web of printing paper
24 is supplied from a supply spool 28 rotatably mounted on a cantilevered
shaft 29 extending from the front side of the front portion of frame 15 of
the spool section 14 of the press 10. The spool section 14 also carries a
supply spool 30a and a take-up spool 30b for supplying and taking up a
continuous web 30c of wiping paper similarly supported on transverse
shafts on the frame 15. The spool section 14 also includes a plurality of
guide rollers 31 rotatably mounted on cantilevered shafts 32 projecting
also from the front of the frame section 15 of the roller section 14 for
guiding the print paper web 24 and the wipe paper 30c. The shafts 27, 29
and 32 are all generally horizontal and oriented transverse the machine 10
and generally parallel to each other. Web tension is maintained by a
dancer roller 33 and the rollers 34 of a web guide and tensioning device
35. The rollers 33, 34 are supported on horizontal transverse shafts which
are movable transverse to the path of the web 24 for controlling the
tension of the moving web.
The print station 12 is provided with an ink mill assembly 37 having an
inking roller 38 positioned to make rolling contact with the plate roller
21 to transfer ink thereto. A wiper roller 39 applies the wiping paper web
30a against the plate cylinder roller 21, moving it in the opposite
direction as that of the surface of the plate roller 21, making wiping
contact therewith.
Referring to FIG. 2, a cross section through the print station 20
illustrates the front portion or front housing 13a of the frame 13 and the
back portion or back housing 13b of the frame 13. The housings 13a, 13b
are part of the rigid fixed frame 13 of the printer section 12.
The frame 13 has formed therein front and rear recesses or shaft support
yokes 40a formed in the front housing 13a and 40b formed in the rear
housing 13b (see FIGS. 3, 4 and 5). Extending horizontally transversely of
the front and rear frame housings 13a, 13b of the press 10 is a lower
rigid hollow cylindrical plate support shaft 41 and an upper rigid hollow
cylindrical impression support shaft 42. The shaft 41 is rigidly secured
at its back end 43 to the back housing 13b in a rear yoke 40b of the rear
housing 13b by rear clamp 44 and a cover plate or retainer ring 45 bolted
to the back housing 13b at the lower end of the rear recess or yoke 40b.
The lower shaft 41 has a front section 46 rigidly secured through the
lower end of the front yoke 40a in the front housing 13a. An insert
housing or collar 48 is rigidly secured by bolts 49 to the front housing
13a. A front clamp 50 is bolted to the collar 48 to firmly clamp the
forward section 46 of the shaft 41 in the front yoke 40a of the front
housing 13a. A forward keeper ring 51 is secured to the forward portion 46
of the shaft 41 to retain the shaft against transverse movement on the
machine by clamping the collar 48 and clamp 50 between the ring 51 and a
shoulder 52 formed at the forward portion 46 of the shaft 41. So
supported, the lower shaft 41 has its extreme forward end 47 supported in
cantilevered fashion extending forward of the front frame member 13a. This
forward end portion 47 carries roller 21 as is explained in detail below.
The upper shaft 42 is adjustably mounted in the frame 13 and extends
horizontally above and approximately parallel to the lower shaft 41. The
upper shaft 42 is supported on the frame 13 at the back housing 13b and at
the front housing 13a so as to be verticallY movable therein with respect
to the frame 13. By "vertically movable" it is meant that the mounting
points of the upper shaft 42 in the yokes 40a and 40b of the housings 13a
and 13b, respectively, are capable of sufficient movement to influence the
pressure between the plate and impression press rolls 21 and 22 as
explained elsewhere herein. This movement may be only a small deflection
of the position of the shaft 42.
The adjustable mounting of the upper shaft 42 is provided by a pair of
front and rear shaft guides or slides 53a and 53b, each slidably mounted
with respect to the front and back housings 13a, 13b, respectively. The
upper shaft 42 is rigidly attached to the back housing slide 53b at its
rear end 54 (FIG. 2) by a cover plate or retainer ring 55 which secures
the back end 54 of the shaft 42 at a hole 56 in the rear slide 53b. The
forward portion 57 of the shaft 42 is rigidly secured to the front slide
53a by a keeper ring 58 attached to the shaft 42 to clamp the slide 53a
between the ring 58 and a shoulder 59 formed in the shaft 42. A stop block
or spacer 60 is bolted to the lower side of the rear slide or guide 53b to
limit the lower position of the rear slide 53b in the rear yoke 40b by
resting against the rear clamp 44.
Extending through the hollow cylindrical shafts 41 and 42 are a pair of
rotary drive shafts 61 and 62, respectively. These drive shafts rotate
within and with respect to the hollow shafts. To this end, the lower drive
shaft 61 is rotatably supported at the back end 43 of the shaft 41 by a
bearing assembly 63 mounted between the shaft 41 and the shaft 61. Shaft
61 extends beyond the shaft 41 and through the lower portion of recess or
yoke 40b where it has mounted to its rear end behind the back housing 13b
a drive gear 64. The drive gear 64 is drivably connected to an identical
driven gear 65 similarly rigidly mounted to the back end of the upper
drive shaft 62 at its extent through the hollow shaft 42 and the rear
housing 13b. This shaft 62 is likewise supported by bearing assembly 67 to
rotate within shaft 42.
As with the lower shaft 41, the upper shaft 42 has its extreme forward end
68 cantilevered forward of the front frame 13a extending approximately
parallel to the extreme forward end 47 of the lower shaft 41. The forward
end 68 carries upper cylinder 22. The lower shaft 41 is provided with
cooling or heating means 69 communicating with fluid input and return
ducts 70a, 70b in the shaft 41 for communicating fluid to maintain the
temperature of the plate cylinder and the ink thereon. Additional
passageways (not shown) are provided in the plate roller assembly 21 to
maintain the desired temperature.
The front ends 47 and 68 of the respective lower and upper shafts 41 and 42
extend through the insert housing or collar 48 and upper guide or slide
53a respectively to provide cantilevered support to the respective
printing roller assemblies 21 and 22. Extending through these forward ends
47 and 68 of the shafts 41 and 42 are the respective forward ends of the
drive shafts 61 and 62. The lower roller assembly 21 is rigidly connected
to the forward end of the shaft 61 by a cap or hub assembly 71 while the
upper impression roller assembly 22 is rigidly connected to the forward
end of the upper shaft 62 by a cap or hub assembly 72. Between the
projecting front ends 47 and 68 of the respective shafts 41 and 42, and
the respective printing roller assemblies 21 and 22, are spherical
bearings 73 and 74, which mount the respective plate and impression
sleeves 75 and 76 to the free ends 47 and 68 of the shafts 41 and 42. The
bearings 73 and 74 are respectively mounted on the shafts 41 and 42 at the
axial midpoints of the roller assemblies 21 and 22 respectively.
The lower print roller or roller assembly 21 includes a plate sleeve 75
which surrounds the projecting front end 47 of the shaft 41. Sleeve 75 is
mounted on the outer race of the bearing 73 so as to rotate about the
fixed shaft 41. The sleeve 75 is secured at its front end to the lower cap
or hub assembly 71 so as to rotate with the hub 71 as it is driven by the
rotation of the drive shaft 61, which flexes slightly so as to permit
slight tilting movement of the axis of sleeve 75 with respect to shaft 41.
Similarly, an upper impression sleeve 76 surrounds the front end 68 of the
shaft 42 and is rigidly secured at its inner surface to the outer race of
the upper bearing 74. The front end of the sleeve 76 is similarly secured
to the upper cap or hub assembly 72 so as to rotate on the bearing 74 with
the hub 72 as it is driven by the shaft 62 and so as to permit slight
tilting movement of the axis of the sleeve 76 thereon.
Surrounding the outer surface of the plate sleeve 75 of the lower print
roller assembly 21 is the plate cylinder 77, the outer surface of which
carries the image which is transferred to the paper web 24 as it is
compressed between the plate cylinder 77 and an impression cylinder 78
which is similarly mounted around the impression sleeve 76 of the upper
print roller assembly 22. These cylinders 77, 78 are positioned on the
axial centers of the bearings 73 and 74 so that, when the pressure is
uniformly distributed across their widths against the web 24, the roller
assemblies 21 and 22 are balanced and will not change tilt on the shaft
ends 47 and 68.
The pressure for compressing the web 24 between the plate cylinder 77 and
the impression cylinder 78 of the roller assemblies 21 and 22 respectively
are exerted by a pair of hydraulic ram assemblies 81 and 82. The front ram
assembly 81 includes a cylinder housing 83 rigidly supported upon a
cylinder support 84 which bridges the mouth of yoke recess 40aof the front
housing 13a of the frame 13. A movable piston rod 85 of the ram assembly
81 has its lower end rigidly secured to the forward shaft guide or slide
53a. Similarly, the back ram assembly 82 includes a cylinder 86 secured to
a cylinder support 87 which bridges the yoke or recess 40b of the back
housing 13b. A movable piston rod 88 is secured to the back shaft guide or
slide 53b.
The ram assemblies 81 and 82 operate to exert downward pressure upon the
front and back guides or slides 53a and 53b, respectively, to thrust the
impression cylinder 78 of the upper impression roller assembly 22 against
the printing plate cylinder 77 of the lower plate roller assembly 21 so as
to squeeze the web 24 between the cylinders 77 and 78 to exert high
printing pressure thereupon.
The width of the web 24 and the cylinders 77 and 78 are generally less than
the diameter of the roller assemblies 21 and 22 and, accordingly, retain
rigidity across their widths as they are driven together at high pressure
under the influence of the hydraulic cylinders 81 and 82. Preferably, the
web 24 is as wide as a single document so as to minimize cutting and
require only transverse cutting to separate printed documents from the web
24, and to minimize distortion of the print sleeves 77 and 78. In the
printing of currency, for example, the width of the web 24 is preferably
the long dimension of the individual bills.
The control of the pressure is facilitated by the mounting of the shaft 42
which supports the upper roller 22 in the guides or slides 53a and 53b
upon the housing 13. As this pressure is being exerted, any
non-parallelism between the shafts 41 and 42 is automatically compensated
for by the spherical bearings 73 and 74 centrally positioned on the axes
of the assemblies 21 and 22, respectively so as to allow the roller
assemblies 21 and 22 to tilt and level with respect to each other so as to
maintain a relatively parallel orientation.
The leveling of the shafts 41 and 42 is in part maintained by front and
back stop assemblies 91 and 92 as shown in FIG. 4, with the front stop
assembly 91 being also illustrated in FIG. 3 and the back stop assembly 92
being also illustrated in FIG. 5. Referring to these figures, the
assemblies 91 and 92 include front and back pairs 93 and 94 which are
mounted so as to move axially transverse the machine 10 along respective
front and rear pairs of drive screws 95 and 96 to move the upper inclined
surfaces 97 and 98, respectively, of the wedge pairs 93 and 94 to raise
and lower respective camm | | |
