Note: Descriptions are shown in the official language in which they were submitted.
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MANDREL ASS~MBLIES FOR DEMOUNTABLE
PRINTING CYLINDERS
This invention relates generally to demountable
printing cylinders, and more particularly to a mandrel assembly
for supporting a demountable cyl.inder and including a pair of
hydraulically-actua-ted sleeves which are expansihle to engage
the end heads of the cylinder to lock the cylinder to the
mandrel asse~ly.
In gravure printing, use is made of a printing cyl-
inder whose surface is etched with cup-like cells which, as
the cylinder passes through an ink fountain, pick up and carry
the ink. When the cylinder engages an impression roller, the
ink is ~ransferred to the surface of the paper running there-
between. Flexographic printing uses similar inks, but the
ink is picked up by rubber printing plates attached to a
cylinder.
Since in the course of such printing operations, it
is frequently necessary to replace one cylinder by another,
various expedients have heretofore been proposed to provide
demountable cylinder structures whereby the same mandrel may
be coupled to different cylinders for use in the printing
machine.
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One known approach makes use of hydraulically-
actuated collet locks for demountable cylinders. However,
known devices of this type require grease yuns to pump fluid
into the lock each time a locking action is to he e~fected, the
grease being bled of~ each time the mandrel is to be released.
The use of grease in the environment of printing operations
is obviously undesirable. Moreover, it is not possible with
such known devices to determine, without the use of additional
expedients, the amount of hydraulic pressure that is being
imposed on the mandrel, and whether it is sufficient to afford
adequate torque resistance. As a consequence, cylinder creep
or slippage may be encountered in the course of printing,
with deleterious effect.
The Hoexter pa-tent 3,378,902 discloses a printing
cylinder having a pair of hydraulically-actuated collets
mounted at opposing ends thereof, the mandrel for supporting
the cylinder being slidably receivable within the collets and
securely locked thereto when hydraulic pressure is applied.
Each collet includes a cylindrical sleeve having a thick-walled
hub section and a relatively long, thin-walled pressure
section. A broad circumferential channel is cut in the pres-
sure section to form a bendable pressure wall, the pressure
section being surrounded by a collar of high tensile strength
whose edges are welded to the pressure section ko define an
annular fluid chamber bounded by the collar and the pressure
wall.
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A pressure cartridge i5 fit-ted into a cavity in the
hub section, the cartridye co~nunicating with the fluid
chamber in the pressure section and includiny a piston which
is advanced inwardly by an adjusting screw. When the annular
chamber is filled with hydraulic fluid and the piston is
advanced inwardly, the resultant hydraulic pressure causes
flexure of the pressure wall, thereby subjecting the mandrel
to radially-directed stresses which are uniformly distributed
and serve to lock the mandrel to the collet and at the same
time to maintain proper concentricity.
In the Hoex~er arrangement, the mandrel is a standard
shaft, but the demountable cylinder is not of standard design.
It is a special cylinder which includes a pair of hydraulically-
actuated end collets, as described above. Hence the special
cylinder is substantially more expensive to manufacture than
a standa~d cylinder. Since each machine in the printing
facility is provided with several special cylinders each oper-
able with a common mandrel, the overall cost of this arrange-
ment is high.
SUMMARY OF INVENTION
In view of the foregoing, the main object of this
invention is to provide a mandrel assembly for use with
standard demountable printing cylinders, the assembly being
hydraulically-actuated to engage the end heads of the cyl-
inder and lock it to the mandrel assembly.
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The inventlon prov.icles t:he combinat:i.on o:E a mandrel
assembly and a s-tandard prlnt:ing cy.Llnder supported thereby in
a printing machine havlng bearlngs, said cylinder having annular
heads fitted therein at each end said heads projecting radially
inward from the inner surface o:E the cylinder, each head being
provided with a circular bore, said cylinder, being demountable
on said assembly, said assembly com~rising:
A. a tube receivable within said cylinder;
B. respec-tive journals joined to opposing ends of
the tube and extending axially therefrom for insertion in said
machine bearings, a respective journal having an expansible
metal sleeve pinned thereon whose normal dimensions are such
that the respective said sleeve fits into the bore of a respec-
tive end head of the cylinder, each said sleeve surrounding an
annular hydraulic chamber formed on each of said journal, said
chamber communicating through an internal duct filled with
hydraulic fluid to a lateral bore in each said journal adjacent
one end of said tube, each journal having a leading section
which is shrunk fit into an end of said tube and an intermediate
section which is surrounded by said sleeve and is relieved to
define said annular hydraulic chamber; and
C. a piston received in each said lateral bore whose
foot is engaged by a piston screw and whose face subjects said
fluid to pressure, whereby when said screw is turned in, the
resultant pressure is transmitted by the fluid to the respec-
tive said sleeve to effect expansion thereof, causing the
respective said sleeve to grip said end head.
The pair of quick-acting hydraulically-actuated
expansible sleeves produce a uniform outward pressure throughout
its circumference to engage the end heads of a printing cylin-
der, whereby distortion of the cylinder is avoided and proper
concentricity is maintained.
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A significant Eeature oE the lnvention resides in a
self-sufficient and sealed hydraulic sys-tem mandrel assembly
which produces a cylinder locking action by turniny a piston
screw, a release action beiny obtained simply by reversing -the
direction oE turn, no ex-ternal source of hydraulic fluid being
required. The preferred form oE hydraulically-actuated mandrel
assembly for demountable printing cylinders makes i-t possible
to use low cost cylinders oE conventional design.
The duct containing the hydraulic fluid and the inlet
section thereto housing the piston and the piston screw to
apply pressure to the fluid are Eormed axially in the journals,
thereby simplifying manufacturing procedures, this s-traight
line arrangement avoiding air pockets in the hydraulic system.
The mandrel assembly is capable of supporting either
of two demountable printing cylinders, one being longer than
the other, thereby obviating the need for separate assemblies
for this purpose and effecting a significant cost saving. In
a mandrel assembly of the above type there is included two
hydraulic systems which are independent of each other and oper-
ate without mutual interference; one system serving to lock the
shorter printing cylinder on the assembly and the other system
locking the longer printing cylinder.
For a better understanding of the invention as well
as other objects and further features thereof, reference is
made to the following detailed description to be read in con-
junction with the accompanying drawings, wherein:
Figure 1 is a perspective view of a standard printing
cylinder mountable on a mandrel assembly in accordance with a
first embodiment of the invention;
Figure 2 is a longitudinal section oE the assembly;
Figure 3 is a transverse section -taken in the plane
indica-ted by lines 3-3 in Figure 2;
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Figure 4 is a transvexse section taken ln -the plane
indicated by lines 4-4 in Figure 2;
Figure 5 is an enlargement of the head of the piston
shown in Figure 3;
Figure 6 is an enl.arged detail showing the annular
hydraulic chamber defined in a journal of the mandrel assembly.
Figure 1' is a perspective view of a mandrel assembly
in accordance with a second embodiment of the invention adapted
to support a standard demountable printing cylinder;
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FicJ. 2' is a longltuclinal section taken through the
mandrel assemblyi
Fig. 3; is an enlar~ement o~ the left journal of
the assembly;
Fi~. ~' is an enlargement of the right journal of the
assembly;
Fig. 5; is a transverse section taken in the plane
indicated by lines 5 - 5 in Fig. 3';
Fig. 6' is a transverse section taken in the plane
indicated by lines 6 - 6 in Fig. 3';
Fig. 1" shows one of the journals of a mandrel assembly
in accordance with a third embodiment of the invention and
one of the two hydraulic systems included therein; and
Fig. 2" shows the same journal and the other o the two
hydraulic systems.
DESCRIPTION OF INVENTION
First Embodiment:
Referring now to Fig. 1, there is shown a gravure
or flexographic printing cylinder 10 releasably mounted
on a mandrel assembly in accordance with the invention
supported for rotation within a printing press, the assembly
including left and right journals 11 and 12 which are
received in suitable bearings in the printing machine
for which it is intended. Cylinder 10 is of standard
design and is of uniform circular cross section. As
best seen in Fig. 3, cylinder 10 is provided with annual
end heads 13 and 14 provided with circular bores.
Journals 11 and 12 each include a leading section
(llA and 12A, respectively) which is shrunk-fit into the
opposite ends o a metal supporting tube 15. Thus the
mandrel assembly is composed o three pieces, tube 15
and journals 11 and 12 joined to either end and extending
axially therefrom.
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Journals 11 and 12 are provided wlth an intermediate
section llB and 12B, respectively, the portion of this
section which adjoins the end of the tube heing encircled
by an expansible sleeve. Thus le~t journal 11 is providec~
with a sleeve 16, and right journal 12 with a sleeve 17,
the sleeve being preferably made of steel. The parameters
are such that the outside dlame-ter oE the sleeves in the
expanded state is substantially equal to that of the end
collet in which it is received; hence the cylinder is readily
mounted thereover, as shown in Fig. 2. The length of the
mandrel assembly measured from sleeve to sleeve is about
equal to the length of the printing cylinder. Hence when
the cylinder is mounted, sleeves 16 and 17 lie within end
collets 13 and 14, respectively, of the cylinder.
The intermediate sections llB and 12B are machined
to relieve a zone underlying sleeves 16 and 17 to define
annular hydraulic chambers 18 and 19. On either side of
these chambers, annular grooves are formed which, in the
case of journals 11 and 12, are occupied by O-rings 20 to
23, these rings providing seals preventing oil leakage
when the sleeves are expanded. In each of these grooves,
there is also a bakc-up ring, rings 24, 25, 26 and 27 being
provided for this purpose.
As best seen in Fig. 5, sleeve 17 is retained in
journal section 12B by a set of three pins 32, sleeve 16
beiny similarly pinned to journal section llB.
In IntcJ~ecl:iate sec~.ion.s llB and 12B at a position
adjacen-t sleeves 18 and 19, there is a lateral bore B to
accommodate pistons 2~ and 29, respectively. Bore B is
terminated by a plug 35. Piston 28 is advanced in its
bore by means of a socket set screw 30 which is normally
turnable by a dog or a similar tool, the screw engaging
the -foot of the piston. Piston 29 is advanced in its bore
by means of a socket screw 31. Bore B leads into an
internal duct D extending longitudinally through the
journal, the duct being filled with hydraulic fluid.
Duct D communicates through lateral branches Ca and
Cb with annual hydraulic chambers 18 and 19 in the journals.
As best seen in Figs. 4 and 6, piston 29, which operates within
lateral bore B in journal section 12B, is provided at its
front face with an o-ring 33 which lies within an annular
groove below the face, the ring serving to prevent leakage
of hydraulic fluid into the lateral bore along the slide
path of the piston. A similar arrangement is provided
for piston 28.
To permlt bleed of the hydraulic fluid, duct B,
as shown in Fig. 4, is provided with a lateral duct E which
leads to the exterior of journal section 12B and is sealed
by a removable plug 34. A similar bleed arrangement is
provided in journal section llB.
Thus when cylinder 10 is ~itted over the three-piece
mandrel assembly ~ormed by tube 15 and journals 11 and 12, the
end head 13 of the cylinder is received on sleeve 16 and the
end head 14 on sleeve 17. In order to lock -the cylinder
to the mandrel assembly, one has merely by means of a suitable
tool to turn in piston screws 30 and 31 on either side of the
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cylinder. This action forces hydraulic flui~ into chambers
18 and 19, respectively, and causes sleeves 16 and 17 -to
expand uniformly, the expansion ca-lsing the sleeves to
engage and yrip the end colle-ts of the cylinder and thereby
securely hold cylinder 10 onto the mandrel assembly.
If one wishes to replace printing cylinder 10 with
another cylinder, all that is necessary is to turn out piston
screws 30 and 31 to release the hydraulic pressure, causing
the sleeves to revert to their normal unexpanded state and
permitting the removal of cylinder 10.
Second Embodiment:
Referring now to Fig. 1', there is shown a gravur~
or flexographic printing cylinder 10 releasably mounted on
a mandrel assembly in accordance with the invention supported
for rotation within a printing press. The assembly includes
left and right journals 11 and 12 which are received in
suitable bearings in the printing machine for which it is
intended. Cylinder 10 is of standard design and is of
uniform circular cross section. As best seen in Fig. 2',
cylinder 10 is provided with end heads 13 and 14 having
circular bores.
Journals 11 and 12 each include a leading section
(llA and 12A) that is shrunk-fit into the opposite ends
of a metal connecting tube 15. Thus the mandrel assembly
is composed of three pieces, tube 15 and journals 11 and 12
joined to either end and extending axiall~ -therefrom.
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The interme~late portion of each journal which
adjoins the end of tube 15 is encircled by an expansible
sleeve. Thus le~t journal :Ll is provided with a slee~e 16
and right journal 12 with a sleeve 17, the sleeves being
preferably made of s-teel. It will be seen that slee~e 16
is provided with a shoulder to form a stop for its
associated cylinder end head. The parameters are such
that the outside diameter of each sleeve ln the unexpanded
state is substantially equal to that of the end head bore
in which it is received; hence the cylinder is readily
mounted thereover, as shown in Fig. 2'. The length o~ the
mandrel assembly measured from sleeve to sleeve is about
e~ual to the length of the printing cylinder. ~Ience when
the cylinder is mounted, sleeves 16 and 17 lie within end
heads 13 and 14 respectively, of the cylinder.
The journals are machined to relieve a zone underlying
sleeves 16 and 17 to define annular hydraulic chambers 18
and 19 respectively, as shown in Figs. 3' and 3'. On either
side of these chambers, annular grooves are formed which
in journal 11 are occupied by O-rings 20 and 21 and in
journal 12 by O-rings 22 and 23. These rings provide seals
preventing oil leakage when the sleeves are expanded, In
each of these grooves, there is also a back-up ring. As
best seen in Fig. 3' and 6', sleeve 16 is retained on
journal 11 by a set of three pins 24 at equi-angular positions,
sleeve 17 being similarly pinned to journal 1~.
~ ince the two journals include identical hydraulic
systems, we shall now describe in detail only that included
in left journal 11. In this journal, as best seen in Fig. 3',
there is an internal main duct 25 which extends axially
therein, the inner end of this duct communicating wi-th
hydraulic chamber 18 through a lateral branch 26 which opens
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in-to the chamber at the leEt s.ide thereof. Coaxially supported
within duct 25 is ~ plug 27 wh.ich serves to provide a
restricted annular passage therein for the h~draulic fluid
which fills duct 25, the branch 26 and chamber 18.
Main duct 25 leads into an axial inlet section 28 whose
conical mouth 29 opens into -the free end of journal 11.
Recelved within inlet section 28 is a piston 30 that is slidable
within a tubular insert 31, the head of this piston being
provided with an "O" ring 32 to provide a seal against oil
leakage through the inlet section. Piston 30 is actuated by
a piston screw 33 received within an internally-threaded
collar 34, access to the screw being had through mouth 29 of
the inlet section.
Also formed in journal 11 is a bleed duct 35 which
extends axially into the leading section llA of the journal,
this duct terminating at the inner end of the journal where it is
permanently plugged after being machined. The inner end of
bleed duct 35 is provided with a lateral branch 36 which leads
into the right side of hydraulic chamber 18, branch 36 of bleed
duct 35 extending in a direction diametrically opposed to
branch 26 of the main duct 25. Bleed duct 35 is also provided
with an auxiliary lateral branch 37 which leads to a socket 38
that lies below an.opening 39 in connectint tube 15 of the
mandrel, socket 38 being adapted to accommodate a removable
stopper or seal.
Thus the hydraulic line is balanced with respect to
hydraulic chamber 18, the fluid passage extending from main
duct 25 into the left side of the chamber and extending from
the right side of the chamber into bleed duct 35~ When this
line is first charged with fluid, the stopper in seal socket
38 is unplugged to permit -the flow of ~luid through the line
until all air is expelled from the line, after which the
sto-per ls put :In plac~.
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Thereafter ~y turning in piston screw 33, -the resultant
hydraullc pressure is transmit-ted to hydraulic chamber 18
in the left journal to cause expansions of sleeve 16 which
acts to grip cylinder head 13 to lock the cylinder to the
mandrel assembly. The structure and operation of the hydraulic
system in the right journal is exactly the same.
Third Embodiment~
Referring now to Fig. l", there is shown a gravure or
flexographic printing cylinder lO releasably mounted on a
mandrel assembly in accordance with the invention. The
assembly includes left and right journals which are received
in suitable bearings in the printing machine for which it is
intended. Cylinder lO is of standard design and is uniform
circular cross section, the cylinder being provided at either
end with an end head ll. In Fig. l" and 2'l, only the left
journal 12 is shown.
In the mandrel assembly, the leading section of the
journals is shrunk fit into opposite ends of a metal connecting
tube 13. Since my copending application shows left and right
journals in conjunction with a connecting tube, for present
purposes, it is sufficient to show only the left journal 12;
for the right journal is structurally and functionally iden-ti-
cal thereto.
Journal 12 is encircled by two expansible sleeves 14
and 15, preferably fabricated of steel, the sleeves being in
side-by-side relation on the intermediate section of the
journal. The parameters are such as that the outside diameter,
each sleeve is substantially equal in the unexpanded s-tate
to the bore in the end head of the printing cylinder.
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Sleeve l~ is adjacent to tube 13, its posl~ion being
such as to fit into the bore oE the en~ head 11 of a cylinder
10 of relatively short standard lenyth such as a 36-inch lony
printing cylinder. Sleeve 15 ls spaced from sleeve 14 to
occupy a position at which it will fit into the bore of -the
end head of a longer cylinder, such as one havlng a 42-inch
length. The same mandrel assembly may therefore be used ~or
cylinders of either length.
Journal 12 is machined to relieve zones underlying
sleeves 14 and 15 to define annular hydraulic chambers 16 and
17. On either side of chamber 16 are annular grooves 16A and
16B occupied by O-rings 18A and 18~, which are compressed by
sleeve 14 to provide seals preventing oil leakage when the
sleeve is e~panded. Similarly, chamber 17 is flanked by annular
groo~es 18A and 18B occupied by O-rings l9A and l9B. Sleeves
14 and 15 are each retained on the journal by a set of three
pins (not shown) at equi-angular positions in a manner dis-
closed in my copending applications.
Chamber 16, as shown in Fiy. 2", communicates through
branch lines 20 and 21 with an internal main duct 22 in the
journal which is filled with hydraulic fluid. Main duct 22
runs toward the right to the front end of the journal where it
is closed by a plug 23. Duct 22 runs toward the left toward
a lateral bore 24 in the journal whose inlet section is occupied
by a piston screw 25 which is ac~essible to an operator.
Also formed in the journal i.s a bleed duct 26 which
runs parallel to the main duct. The right end of the bleed
duct communicates with annular chamber 16 through a branch line 27,
the other end of the bleed duct leading to a slide line 28
plugged by a stopper 29.
Thus the hydraullc system ~or chamber 16 is balance~.
When the system is first charcJed, the s-toppers are removed
to unseal the fluid lines to permit the flow of fluid until
all alr is expelled from -the lines, after which -the stopper is
put back in place.
ThereaEter, by turning screw 25, the resultant hydraulic
pressure is transmitted to hy~raulic chamber 16 to cause ex-
pansion of sleeve 14 which acts to grip cylinder head 11 to
lock the cylinder to the mandre.
Hydraulic chamber 17 associated with sleeve 15 is of
the same design as that associated with sleeve 14 and includes
a piston screw 30 operating in a lateral bore 31 leading into
a main duct 32 provided with branches 33 and 34 communicating
with chamber 17. The operation of the hydraulic system for
sleeve 15, which is used for longer printing cylinders, is
independent of the system for sleeve 14 or the shorter cylinder.
In the arrangement shown in the figures, the piston for
the two hydraulic systems both operate at right angles to the
axis of the journal. In practice, the outermost sleeve 15 may
be hydraulically actuated with a system of the type disclosed
herein in the second embodiment in which there is a straight
line arrangement for the fluidic system with the piston screw
in an inlet section on the axis o~ the Journal, Thus the
three-piece mandrel assembly in accordance with this third
embodiment has a palr o~ journals, each o~ which has first and
second expansible sleeves positioned for printing cylinders of
different length.
