Plate sleeve-holder cylinder made of carbon-fibre composite material for flexographic printing and including compressed air channels

Abstract

A plate sleeve-holder cylinder provided with a carbon-fibre central tube (T) comprising compressed air channels (6, 7, 8) arranged between one of the end flanges (Fb, Fm) of said plate sleeve-holder cylinder and a plurality of holes (H) formed in the outer surface of said central tube (T) made of carbon-fibre composite material. Said air channels (6, 7, 8) are partly embedded within said end flanges (Fb, Fm), partly within a thickness of a side wall (P) of said central tube (T) made of carbon-fibre composite material. Additionally, a process of manufacturing said central tube (t) is disclosed by inserting air pipes (6) into grooves (1) which are formed by mechanical milling of a surface of the supporting structure (P) of said central tube (T) obtained through a first lamination and polymerization, said grooves being coated with a surface finishing structure (S) obtained through a second lamination and polymerization.

Claims

1. A plate sleeve-holder cylinder for flexographic printing comprising: a carbon-fibre central tube (T) and first and second flanges (Fb, Fm) respectively provided on each end of said carbon-fibre central tube (T); compressed air channels (6, 7, 8) arranged between one of the first and second flanges (Fb, Fm); and a plurality of vent holes (H) formed in the outer surface of said central tube (T) made of carbon-fibre composite material, in order to ease an insertion of sleeves onto said plate sleeve-holder cylinder; wherein said air channels (6, 7, 8) are partly embedded within said first and second flanges (Fb, Fm), and partly embedded within a thickness of a side wall of said central tube (T) made of carbon-fibre composite material.

2. The plate sleeve-holder cylinder of claim 1, wherein the portion of said air channels (6, 7, 8) embedded within the thickness of the side wall of said central tube (T) of carbon-fibre composite material comprises one or more air pipes (6) housed in grooves (1) formed in a supporting structure (P) of the side wall of said central tube (T).

3. The plate sleeve-holder cylinder of claim 2, wherein a filling material (5) takes up a residual space of said grooves (1) housing an air pipe (6).

4. The plate sleeve-holder cylinder of claim 3, wherein said filling material (5) comprises monodirectional resin-impregnated carbon fibres.

5. The plate sleeve-holder cylinder of claim 2, wherein said one or more air pipes (6) comprises a thin layer (2) of carbon fibre, previously wrapped on a metal mandrel (3) and removed therefrom or wrapped on an embedded tubular insert (4) made of plastic or metal material.

6. The plate sleeve-holder cylinder of claim 2, wherein said plate sleeve-holder cylinder further comprises a coating layer (S) of resin-impregnated carbon-fibre fabric which covers the entire outer surface of said plate sleeve-holder cylinder and said grooves (1) housing the air pipes (6).

7. The plate sleeve-holder cylinder of claim 2, wherein said grooves (1) are straight and parallel to the axis of said central tube (T) made of carbon-fibre composite material.

8. The plate sleeve-holder cylinder of claim 2, wherein said one or more air pipes (6) are connected to each other and to an external valve (V) supplying compressed air, by means of air channels (7) formed within said first flange (Fb) which forms the base end of said plate sleeve-holder cylinder.

9. The plate sleeve-holder cylinder of claim 8, wherein an air channel (8) having a circular shape, which puts the air pipes (6) in communication with each other, is formed in said second flange (Fm) which closes the opposite end of the plate sleeve-holder cylinder, where the sleeves are inserted, said air channel (8) being provided with a plurality of radial vent holes (K) opening onto the external lateral surface of the second flange (Fm).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the plate sleeve-holder cylinder according to the present invention will in any case become more evident from the following detailed description of a preferred embodiment thereof, provided only by way of non-limiting example and illustrated in the attached drawings, wherein:

(2) FIG. 1 is a schematic perspective view of one end of a central tube of a plate sleeve-holder cylinder of the known art, embodying a compressed air circuit formed by pipes fixed to the side wall of said central tube;

(3) FIG. 2 is a perspective view of one end of a central tube of the plate sleeve-holder cylinder of the present invention, in a first manufacturing step;

(4) FIGS. 3, 4 and 5 are perspective views of the detail highlighted with a circle in FIG. 2, in successive steps of the central tube manufacturing;

(5) FIG. 6A is a partly broken away perspective view which illustrates channels formed in one of the end flanges of the plate sleeve-holder cylinder of the present invention for delivering compressed air;

(6) FIG. 6B is an enlarged view of a detail of FIG. 6A;

(7) FIG. 7A is a partly broken away perspective view which illustrates the channels formed in the other end flange of the plate sleeve-holder cylinder of the present invention for delivering compressed air;

(8) FIG. 7B is a view like FIG. 7A, without the outer sealing cover;

(9) FIG. 8A is a perspective view of the plate sleeve-holder cylinder of the present invention in the whole, seen from the end flange into which compressed air is supplied; and

(10) FIG. 8B is a perspective view of the plate sleeve-holder cylinder of FIG. 8A, seen from the opposite flange onto which sleeve insertion takes place.

DETAILED DESCRIPTION OF THE SEVERAL EMBODIMENTS

(11) According to the present invention, in order to solve the problem highlighted above by means of a constructively simple and immediately applicable solution, the inventors conceived to embed low-volume air pipes for compressed air delivery within the thickness of the side wall of the central tube made of carbon-fibre composite material of a plate sleeve-holder cylinder for flexographic printing. This innovative technical solution, in addition to radically and effectively solving the safety problems exhibited by known plate sleeve-holder cylinders having an inner high-pressure chamber, also allows to considerably simplify the air pipe construction, meanwhile offering significantly higher reliability over time, with respect to the previously discussed prior art solution which discloses pipes positioned in the inner chamber of the plate sleeve-holder cylinder and attached to the side wall thereof.

(12) In general, the compressed air pipes according to the present invention are formed in the central tube made of composite material during the same lamination step thereof—carried out with “wrapping” or “filament winding” technologies or with a combination of the same—by embedding appropriate inserts or mandrels, which may be withdrawable after the resin polymerization, within the thickness of the side wall of said central tube, in order to create one or more straight longitudinal pipes having a desired section.

(13) In particular, a preferred manufacturing process of a central tube made of carbon-fibre composite material according to the present invention wherein air pipes for compressed air delivery are embedded, comprises the steps of: a) a main lamination, preferably carried out with “filament winding” technology by means of resin-impregnated carbon fibres, for manufacturing the supporting structure (P) of the central tube made of composite material; b) a polymerization of the resin of the supporting structure P obtained in step a); c) a mechanical milling (FIG. 2) of the outer surface of the hardened supporting structure P of the central tube obtained in step b), for forming straight longitudinal grooves 1 in such outer surface of the supporting structure P, wide enough to house air pipes 6 of a desired size; d) a formation of air pipes 6 for compressed air delivery (FIGS. 3 and 4) by inserting into the grooves 1 a thin cylindrical layer 2 of carbon fibres pre-impregnated with resin, radially wrapped around a metal mandrel 3 intended to be successively removed or around a hollow insert 4 made of plastic or metal intended to remain embedded within said cylindrical layer 2 of carbon fibres; e) a filling of the residual space of grooves 1 with a polymerizable filling material 5, preferably with monodirectional carbon fibres pre-impregnated with resin; f) a secondary lamination (FIGS. 4 and 5), preferably carried out with “wrapping” technology, by means of a resin-impregnated carbon-fibre fabric, for manufacturing a surface finishing structure S of the tube T made of composite material; g) a polymerization of the resin contained in the cylindric layer 2, in the filling material 5 and in the surface finishing structure S; h) a removal of mandrel 3 (FIG. 3), where present; i) a mechanical drilling of the outer surface of the tube T made of composite material, in correspondence of air pipes 6, for forming vent holes H (FIG. 8) along said air pipes 6 at regular intervals.

(14) As mentioned above, in step d) of formation of the air pipes 6 it is possible to use both removable metal mandrels 3 and disposable hollow inserts 4, intended to remain embedded in the structure of the central tube T made of carbon-fibres composite material during the lamination step. The choice between these two solutions can be dictated by geometric constraints, needs of the technological process or requirements of the air flow requested in the air pipes 6, based on the specific model of plate sleeve-holder cylinder.

(15) Thanks to the manufacturing process described above it is generally possible to manufacture circular air pipes 6, housed into grooves 1 having a semi-circular bottom, as well as rectangular/squared air pipes 6 housed in grooves 1 having a flat bottom. In the drawings (FIGS. 6 and 7), two pipes 6 are illustrated arranged at 180° from each other on the surface of the central tube T made of composite material; such an arrangement, however, is not limitative and the number and arrangement of pipes 6 can be varied as will, based on the type, size and use of each single model of plate sleeve-holder cylinder.

(16) As shown in FIGS. 6A and 6B, air pipes 6 thus formed within tube T made of composite material are finally connected to each other and to an external valve V for compressed air supply by means of air channels 7 machined inside a flange Fb forming the base end of the plate sleeve-holder cylinder. As shown in FIGS. 7a and 7B a flange Fm which closes the opposite end of the plate sleeve-holder cylinder, i.e. the end onto which sleeve insertion takes place, is provided instead with a circular air channel 8 which connects the air pipes 6 between them and with a crown of radial vent holes K which allow that an uniform flow of compressed air springs from the outer edge of the flange Fm and therefore the required functionality of easing the initial insertion of the sleeves on the plate sleeve-holder cylinder is obtained.

(17) Internal air seal of the working air pressure is ensured at the junctions between the air pipes 6 and the air channels 7 and 8, formed in the end flanges Fb and Fm, by the adhesive itself used to make these flanges integral with the central tube T made of composite material. Air seals towards the outside of air channels 7 and 8 are instead obtained, in a per se known manner, by means of circular diaphragms 9 in the flange Fb (FIG. 6B) and of a ring cover 10 in the flange Fm (FIG. 7A), respectively, both conveniently equipped with O-rings, as shown in the drawings.

(18) Methods (coupling and adhesive bonding) for assembling the central tube T made of composite material and the metallic end flanges F must be therefore such as to ensure a perfect alignment between the air pipes 6 and the air channels 7 and 8 formed in the flanges Fb and Fm, and to ensure the relative air seal on frontal and cylindrical contact surfaces between these elements. To this purpose, centring dowels are preferably used, engaged with corresponding centring holes provided on the flanges F, from one side, and then with the air pipes 6 formed in the central tube T made of composite material, from the other side. Said dowels are placed in position when bonding the flanges Fb and Fm to the central tube T and are then subsequently extracted from outside the flanges when the bonding adhesive is sufficiently polymerized. Residual holes remained on the flanges are then closed with corresponding plugs.

(19) The above-described technical solution can be equally applied both to plate sleeve-holder cylinders provided with conventional flanges F, i.e., made as a single piece of steel comprising both the actual flange and the respective rotation pin, and to plate sleeve-holder cylinders provided with two-pieces flanges F, i.e., an aluminium flange portion and a steel rotation pin screwed on the aluminium flange portion. Moreover, this latter solution remains perfectly safe, given the lack of compressed air inside the central tube T made of composite material, and it furthermore makes partially accessible the inside of the tube T made of composite material by removing the rotation pin from the aluminium flange portion bonded to the central tube T.

(20) From the foregoing description it is evident that the plate sleeve-holder cylinder of the present invention has fully achieved the intended objects, as the compressed air pipes 6 are embedded within the same constituent elements of the plate sleeve-holder cylinder, without using additional or foreign elements. Said air pipe structure is therefore especially sturdy and reliable.

(21) The plate sleeve-holder cylinder of the present invention also allows to achieve several operational advantages, which can be summarized as follows: complete safety for the operators, even in the event of loss of seal and accidental air leaks in, or breakages of, the central tube T made of composite material in correspondence of the air pipes 6, because the volume of air contained in such air pipes 6 is so low that it cannot give rise to sudden expulsions or sudden fractures of the components; the plate sleeve-holder cylinder should no longer be considered as a pressure vessel and therefore do not require to be subjected to the legal regulations of pressure vessels and the related certifications; any air leaks are easily detectable and, particularly in the case of a flexographic print cylinder with screwed pins, a fast repair can be allowed which does not affect the functionality of cylinder itself, and avoids being forced to discard the same; the low volume of air of the air pipes 6 and air channels 7 and 8 makes it possible to pressurize the circuit quickly, speeding up the operation of sleeve insertion; the manufacturing of the plate sleeve-holder cylinder is simple, and the structure obtained is more reliable in use, as no additional components difficult to assemble, or other solutions highly difficult to implement, are required, such as the use of a coaxial inner cylinder; the manufacturing cost is comparable to the conventional solution with a central tube T having an inner pressurized chamber; a highly flexible design about the choice of the number, shape, size and arrangement of air pipes 6 and holes H and K for the compressed air outlet is finally allowed.

(22) It is understood, however, that the invention is not to be considered as limited to the arrangements illustrated above, which only are exemplary embodiments thereof, but that various variants are possible, all within the reach of a man of ordinary skill in the art, without departing from the scope of the invention itself, which is only defined by the following claims.