CA1208974A - Mandrel assemblies for demountable printing cylinders - Google Patents

Abstract

ABSTRACT
A standard printing cylinder is supported by a mandrel assembly in a printing machine having bearings, the cylinder having end heads at either end provided with circular bores and being demountable on the mandrel assembly. The assembly comprises a tube receivable within the cylinder and journals joined to opposing ends of the tube and extending axially therefrom for insertion in the machine bearings. Each journal has an expansible metal sleeve pinned thereon whose normal diameter is such that the sleeve fits into a respective end head bore of the cylinder. The sleeve surrounds an annular hydraulic chamber formed on the journal, which chamber communicates with an axially-extending main internal duct filled with hydraulic fluid and having an inlet section in line therewith whose mouth opens into the free end of the journal.
The journal has a leading section which is shrunk fit onto an end of the tube and an intermediate section which is surrounded by the sleeve to define the annular hydraulic chamber. The intermediate section has grooves on either side of the chamber in which "o"
rings are received to effect a seal preventing leakage of fluid when the sleeve is expanded. A piston is slidable in the inlet section and has a piston screw which is accessible through the mouth. The screw when turned in advances the piston to produce hydraulic pressure which is transmitted through the chamber to the sleeve to cause expansion thereof whereby the sleeve grips the end head to lock the cylinder to the mandrel.

Description

7~a 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.

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 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.

_g_ 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 9~

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.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The combination of a mandrel assembly and a standard printing cylinder supported thereby in a printing machine hav-ing bearings, said cylinder having annular heads fitted therein at each end said heads projecting radially inward from the inner surface of the cylinder, each head being provided with a circular bore, said cylinder, being demountable on said assem-bly, said assembly comprising:
A. a tube receivable within said cylinder;
B. respective 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 respective said sleeve to effect expansion thereof, causing the respective said sleeve to grip said end head.

2. An assembly as set forth in claim 1, wherein said intermediate section has grooves formed on either side of said chamber to accommodate "O" rings to effect a seal preventing leakage of said fluid when said sleeve is expanded.

3. An assembly as set forth in claim 2, wherein said sleeve is fabricated of steel.

4. An assembly as set forth in claim 1, wherein said duct is formed longitudinally in said intermediate section and is provided with lateral branches which communicate with said chamber.

5. An assembly as set forth in claim 4, wherein said bore is provided with a fluid bleed duct leading to the exterior of the journal and sealed by a removable plug.