GB2137140A - Printing Cylinders - Google Patents

Abstract

A mandrel assembly for demountably supporting a printing cylinder comprises a metal tube (15) having fitted to the ends thereof respective journals (11, 12) each provided with an expansible sleeve (16, 17) sized so as when expanded to engage with respective end collets (13, 14) of a printing cylinder (10) for mounting the cylinder (10) on the mandrel. The journals (11, 12) each comprise an annular hydraulic chamber (18, 19) underlying the respective expansible sleeve (16, 17) and coupled via ducts (D, Ca, Cb) with a piston and cylinder actuating arrangement comprising respective bores (B) formed in end portions of the journals (11, 12), a piston (28, 29) in each bore (B) and a driving screw (30, 31) enabling the piston to be adjusted within its bore so as to determine the hydraulic pressure in the respective chamber (18, 19) and thereby determine whether the expansible sleeves (16, 17) are in expanded, printing cylinder mounting condition or in retracted, printing cylinder demounting condition. Alternative arrangements are described for determining the hydraulic pressure settings of the expansible sleeves, and, in one embodiment, a mandrel is provided which can accept different lengths of printing cylinders. <IMAGE>

Description

SPECIFICATION Mandrel Assemblies for Demountable Printing Cylinders This invention relates generally to demountable printing cylinders, and more particularly to a mandrel assembly for supporting a demountable cylinder and including a pair of hydraulically-actuated sleeves which are expansible to engage the end heads of the cylinder to lock the cylinder to the mandrel assembly.

In gravure printing, use is made of a printing cylinder 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 transferred to the surface of the paper running therebetween. 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.

One known approach makes use of hydraulically-actuated collet locks for demountable cylinders. However, known devices of this type require grease guns to pump fluid into the lock each time a locking action is to be effected, the grease being bled off 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 deletenous effect.

The Hoexter US patent 3,378,902 discloses a printing cylinder having a pair of hydraulicallyactuated 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-wailed hub section and a relatively long, thin-walled pressure section. A broad circumferential channel is cut in the pressure 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 to define an annular fluid chamber bounded by the collar and the pressure wall.

A pressure cartridge is fitted into a cavity in the hub section, the cartridge communicating with the fluid chamber in the pressure section and including 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 radiallydirected 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 Hoexter 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 standard cylinder. Since each machine in the printing facility is provided with several special cylinders each operable with a common mandrel, the overall cost of this arrangement 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 cylinder and lock it to the mandrel assembly.

More specifically, an object of this invention is to provide a mandrel assembly of the above type having a pair of quick-acting hydraulicallyactuated expansible sleeves adapted to produce a uniform outward pressure throughout its circumference to engage the end heads of a printing cylinder, whereby distortion of the cylinder is avoided and proper concentricity is maintained.

A significant feature of the invention resides in a self-sufficient and sealed hydraulic system mandrel assembly which produces a cylinder locking action by turning a piston screw, a release action being obtained simply by reversing the direction of turn, no external source of hydraulic fluid being required.

Also an object of the invention is to provide a hydraulically-actuated mandrel assembly for demountable printing cylinders which makes it possible to use low cost cylinders of conventional design.

Yet another object of this invention is to provide a mandrel assembly of the above type wherein 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 formed axially in the journals, thereby simplifying manufacturing procedures, this straight line arrangement avoiding air pockets in the hydraulic system.

Still another object of the invention is to provide a mandrel assembly 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 operate without mutual interference; one system serving to lock the shorter printing cylinder on the assembly and the other system locking the longer printing cylinder.

Outline of Drawings 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 conjunction with the accompanying drawings, wherein: Fig. 1 is a perspective view of a standard printing cylinder mountable on a mandrel assembly in accordance with a first embodiment of the invention; Fig. 2 is a longitudinal section of the assembly; Fig. 3 is a transverse section taken in the plane indicated by lines 3-3 in Fig. 2; Fig. 4 is a transverse section taken in the plane indicated by lines 4 4 in Fig. 2; Fig. 5 is an enlargement of the head of the piston shown in Fig. 3; Fig. 6 is an enlarged detail showing the annular hydraulic chamber defined in a journal of the mandrel assembly.

Fig. 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; Fig. 2' is a longitudinal section taken through the mandrel assembly; Fig. 3' is an enlargement of the left journal of the assembly; Fig. 4' 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. 6r 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 of 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 (1 A and 1 2A, respectively) which is shrunk-fit into the opposite ends of a metal supporting tube 15. Thus the mandrel assembly is composed of three pieces, tube 1 5 and journals 11 and 12 joined to either end and extending axially therefrom.

Journals 11 and 12 are provided with an intermediate section 11 B and 12B, respectively, the portion of this section which adjoins the end of the tube being encircled by an expansible sleeve. Thus left journal 11 is provided 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 diameter of the sleeves in the expanded state is susbtantially 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 1 6 and 17 lie within end collets 1 3 and 14, respectively, of the cylinder.

The intermediate sections 11 B and 1 2B are machined to relieve a zone underlying sleeves 1 6 and 17 to define annular hydraulic chambers 18 and 1 9. 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 back-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 1 2B by a set of three pins 32, sleeve 1 6 being similarly pinned to journal section 11B.

In intermediate sections 11 B and 1 2B at a position adjacent sleeves 1 8 and 19, there is a lateral bore B to accommodate pistons 28 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 C a and Cb with annular 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 siide path of the piston. A similar arrangement is provided for piston 28.

To permit 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 1 2B and is sealed by a removable plug 34. A similar bleed arrangement is provided in journal section 11 B.

Thus when cylinder 10 is fitted over the threepiece mandrel assembly formed by tube 1 5 and journals 11 and 12, the end head 13 of the cylinder is received on sleeve 1 6 and the end head 1 4 on sleeve 1 7. 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 fluid into chambers 1 8 and 19, respectively, and causes sleeves 1 6 and 1 7 to expand uniformly, the expansion causing the sleeves to engage and grip the end collets 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 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 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 (11 A and 12A) that is shrunk-fit into the opposite ends of a metal connecting tube 1 5.

Thus the mandrel assembly is composed of three pieces, tube 1 5 and journals 11 and 12 joined to either end and extending axially therefrom.

The intermediate portion of each journal which adjoins the end of tube 1 5 is encircled by an expansible sleeve. Thus left journal 11 is provided with a sleeve 16 and right journal 12 with a sleeve 17, the sleeves being preferably made of steel. It will be seen that sleeve 1 6 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 in 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 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 1 6 and 1 7 lie within end heads 1 3 and 14 respectively, of the cylinder.

The journals are machined to relieve a zone underlying sleeves 16 and 1 7 to define annular hydraulic chambers 1 8 and 1 9 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 1 7 being similarly pinned to journal 12.

Since 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 with hydraulic chamber 1 8 through a lateral branch 26 which opens into the chamber at the left side thereof.

Coaxially supported within duct 25 is a plug 27 which serves to provide a restricted annular passage therein for the hydraulic 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. Received 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 "0" ring 32 to provide a seal against oil leakage through the inlet section. Piston 30 is actuated by a piston screw 33 received within a 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 1 1A 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 connecting 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 fluid through the line until all air is expelled from the line, after which the stopper is put in place.

Thereafter by turning in piston screw 33, the resultant hydraulic pressure is transmitted to hydraulic chamber 18 in the left journal to cause expansions of sleeve 1 6 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. ", there is shown a gravure or flexographic printing cylinder 10 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 10 is of standard design and is uniform circular cross section, the cylinder being provided at either end'with an end head 11. In Fig. " and 2", 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 identical thereto.

Journal 1 2 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 state to the bore in the end head of the printing cylinder.

Sleeve 14 is adjacent to tube 13, its position being such as to fit into the bore of the end head 11 of a cylinder 10 of relatively short standard length such as a 36-inch long printing cylinder.

Sleeve 1 5 is 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 having a 42-inch length. The same mandrel assembly may therefore be used for cylinders of either length.

Journal 12 is machined to relieve zones underlying sleeves 14 and 1 5 to define annular hydraulic chambers 1 6 and -17. On either side of chamber 16 are annular grooves 1 6A and 16B occupied by O-rings 1 8A and 1 8B, which are compressed by sleeve 14 to provide seals preventing oil leakage when the sleeve is expanded. Similarly, chamber 1 7 is flanked by annular grooves 1 8A and 1 8B occupied by 0rings 1 9A and 19B. Sleeves 14 and 1 5 are each retained on the journal by a set of three pins (not shown) at equi-angular positions in a manner disclosed in my copending applications.

Chamber 16, as shown in Fig. 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 accessible to an operator.

Also formed in the journal is 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 hydraulic system for chamber 1 6 is balanced. When the system is first charged, the stoppers are removed to unseal the fluid lines to permit the flow of fluid until all air is expelled from the lines, after which the stopper is put back in place.

Thereafter, by turning screw 25, the resultant hydraulic pressure is transmitted to hydraulic chamber 16 to cause expansion of sleeve 14 - which acts to grip cylinder head 11 to lock the cylinder to the mandrel.

Hydraulic chamber 1 7 associated with sleeve 1 5 isof 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 1 7. -The operation of the hydraulic system for sleeve 15, which is used for longer printing cylinders, is independent of the system for sleeve 14 for 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 1 5 may by 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 of the Journal. Thus the three piece mandrel assembly in accordance with this third embodiment has a pair of journals, each of which has first and second expansible sleeves positioned for printing cylinders of different length.

Claims (8)

1. The combination of a mandrel assembly and a standard printing cylinder supported thereby in a printing machine having bearings, said cylinder having end heads at either end provided with circular bores and being demountable on said assembly, said assembly comprising: A. a tube receivable within said cylinder;; B. journals joined to opposing ends of the tube and extending axially therefrom for insertion in said machine bearings, each journal having an expansible metal sleeve pinned thereon whose normal diameter is such that the sleeve fits into a respective end head bore of the cylinder, said sleeve surrounding an annular hydraulic chamber formed on said journal, said chamber communicating 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, said journal having a leading section which is shrunk fit onto an end of said tube and an intermediate section which is surrounded by said sleeve to define said annular hydraulic chamber, said intermediate section having grooves on either side of said chamber in which "0" rings are received to effect a seal preventing leakage of said fluid when the said sleeve is expanded; C. A piston slidable in said inlet section and a piston screw therein which is accessible through said mouth, the screw when turned in advancing said piston to produce hydraulic pressure which is transmitted through said chamber to said sleeve to cause expansion thereof whereby the sleeve grips said end head to lock the cylinder to the mandrel.

2. An assembly as set forth in claim 1, wherein said sleeve is fabricated of steel.

3. An assembly as set forth in claim 1, wherein said journal further includes an axially-extending bleed duct filled with hydraulic fluid and communicating through a lateral branch with a sealable socket which registers with an opening in said connecting tube to permit bleed of fluid therefrom.

4. An assembly as set forth in claim 3, wherein said main duct communicates with one side of said chamber through a lateral main branch and said bleed duct communicates with the other side of said chamber through a lateral bleed branch.

5. An assembly as set forth in claim 1, wherein said main duct has a plug coaxially supported therein to define an annular restricted passage for said hydraulic fluid.

6. A mandrel assembly as set forth in claim 1 for supporting either a long or a short standard printing cylinder in a printing machine having bearings, said assembly having left and right journals joined to opposing ends of the tube and extending axially therefrom for insertion in said machine bearings, each journal having first and second expansible sleeves thereon in side-by-side relation, the first sleeve fitting into the bore of an end head of the short cylinder, the second sleeve fitting into the bore of an end head of the long cylinder, each sleeve surrounding an annular hydraulic chamber formed on the journal; and first and second hydraulic systems associated with the chambers for said first and second sleeves, each system including an internal longitudinal duct in the journal filled with hydraulic fluid and communicating with the related chamber, and means to subject the fluid to pressure to effect expansion of the related sleeve.

7. A mandrel assembly for demountably supporting a printing cylinder in a printing machine and comprising two axially spaced apart journals for insertion in bearings of said machine, each journal having an expansible annular sleeve whose unexpanded diameter is such that the sleeve can be fitted into a respective end head bore of the cylinder and an annular hydraulic chamber underlying said expansible sleeve, said chamber communicating with a piston and cylinder arrangement wherein the position of the piston in the cylinder is adjustable for determining the hydraulic pressure exerted on said expansible sleeve by hydraulic fluid in said annular hydraulic chamber, the arrangement being such that by adjustment of the position of the piston in the cylinder the state of expansion of said expansive sleeve can be determined.

8. A mandrel assembly substantially as herein described with reference to any of the accompanying drawings.