DESCRIPTION

The present invention relates to a lateral protective element of a flexographic sleeve of a machine per flexographic printing.

As is known, flexography is a direct rotary relief printing method and is alike to typography inasmuch as it uses resilient printing plates made of rubber or photopolymeric materials.

The printing plate is fixed on the sleeve which in turn is keyed on a rotating mandrel and is inked by means of a batching roller known as an "anilox" which is cell-structured, with the cells transferring the quick-drying printable liquid ink onto virtually any support, either absorbent or non-absorbent.

As is known, the sleeve is formed by a multilayer cylinder having a cylindrical axial cavity for insertion on the mandrel and two protective elements applied on the base of the cylinder.

One of the two protective elements is provided with a register slot engageable by an abutment provided on the mandrel for guaranteeing the correct angular position of the cylinder on the mandrel.

At present the register slot is realised on an L-shaped aluminium block which is fixed by a screw to a flat ring made of a different material acting as a protective element.

The internal edge of the base of the cylinder has a notch having a shape complementary to a wing of the L-shaped block in which the block is housed when the flat ring is glued to the base of the cylinder.

This assembly procedure of the sleeve is rather elaborate and complex and the lengthening of the assembly times inevitably leads to an increase in production costs.

The task proposed by the present invention is to make available an adapter sleeve which does not have the drawbacks of the prior art.

In the scope of this task, the object of the invention is to realise a construction for a sleeve per flexographic printing which enables a simplification of the assembly procedure and, in the end, a saving in production costs.

This task, as well as these and other aims, are attained by a sleeve for flexographic printing, comprising a cylinder and a protective element applied on a base of said cylinder and equipped with a register slot that can be engaged by an abutment provided on a mandrel on which said sleeve is mounted, said sleeve being characterised in that said lateral protective element and said register slot are made as a single piece with the same type of material.

Preferably said piece is made using a 3D printer. Said lateral protective element is preferably a ring having an internal base and an external base in the form of a circular crown.

Said ring is a primary portion of said piece.

Said register slot preferably extends in a secondary portion of said piece that surmounts said internal base of said ring.

In the direction of the axial generatrices of said ring, said secondary portion of said piece is preferably greater in size than said ring.

A lateral wall of said secondary portion of said piece preferably extends on the extension of internal axial generatrices of said ring.

Said register slot preferably extends until it opens at said external base of said ring.

Said register slot preferably has a cylindrical zone for engaging said abutment and a tapered zone for guided access of said abutment into said engagement zone.

Said internal base of said ring has weight-relief openings also functioning as reservoirs for an adhesive for joining said piece to said base of said cylinder.

Said piece preferably has graphic elements on said external base of said ring for customizing said sleeve.

Said secondary portion of said piece is preferably housed in a complementarily-shaped notch present at an internal edge of said base of said cylinder.

Said piece is preferably joined with an adhesive to said cylinder.

The present invention also discloses a protective element that is applicable on a base of a cylinder of a sleeve for flexographic printing, characterized in that it is made as a single piece, of the same type of material, with a register slot that can be engaged by an abutment provided on a mandrel on which said sleeve is mounted, said lateral protective element being a ring having an internal base and an external base in the form of a circular crown, said register slot extending in a secondary portion of said piece surmounting said internal base of said ring, said secondary portion of said piece extending on the extension of internal axial generatrices of said ring, said register slot extending until it opens at said external base of said ring.

Advantageously, said piece is suited to construction for additive manufacturing with various technologies such as FFF, DIW, SLA, DPL, 3DP, EBM, SLM, SHS, SLS, DMLS, LOM, EBF, etc.

Further characteristics and advantages of the invention will more fully emerge from the description of a preferred but not exclusive embodiment of a sleeve for flexographic printing, illustrated by way of non-limiting example in the accompanying drawings, in which:

figure 1 is an axonometric view of the piece incorporating the protective element and the register slot; figure 2 is a lateral elevation view of the piece of figure 1 in cross-section;

figure 3 is an axonometric view of the sleeve from which an angular sector has been removed for ease of illustration; and

figure 4 is a front view of the sleeve of figure 3, keyed on the mandrel of the flexographic printing machine.

With particular reference to the figures described above, the sleeve for flexographic printing is denoted in its entirety by reference number 1.

The sleeve 1 comprises a cylinder 2 and lateral protective elements 3, 4 applied to the bases of the cylinder 2.

The cylinder 2 has an axial cylindrical cavity 5 adapted to receive a rotary support mandrel 6.

The cylinder 2 has at least three different layers, from inside to outside: a base layer, at least an intermediate layer for damping the vibrations and an external layer on which a printing plate (not shown) is applied which comes into contact with a printing support (not shown).

One of the protective elements, denoted by reference number 3, is provided with a register slot 7 that can be engaged by an abutment 8, for example a pin, provided on the mandrel 6.

The lateral protective element 3 and the register slot 7 are advantageously made as a single piece

9 with the same type of material.

The piece 9 is advantageously made of a material susceptible of being printed using a 3D printer. The protective element 3 is a ring 1 1 that has an internal base 13 and an external base 14 in the form of a circular crown.

In particular the protective element 3 is a flat ring 11 that has an internal flat base 13 adjacent in use to the base of the cylinder 2 and an external flat base 14 opposite in use to the base of the cylinder 2, the internal and external flat bases 13, 14 being in the form of a circular crowns parallel to each other, the register slot 7 projecting orthogonally and externally to the flat ring 1 1 from the internal flat base 13.

Therefore the ring 1 1 is a primary portion of the piece 9 while the register slot 7 extends in a secondary portion 12 of the piece 9.

The secondary portion 12 of the piece 9 surmounts the internal base 13 of the ring 1 1.

The secondary portion 12 of the piece 9 is, in the direction of the axial generatrices of the ring

11 , greater in size than the ring 11.

In particular, the secondary portion 12 is delimited by four lateral walls which project perpendicularly from the internal base 13 of the ring 1 1, and a rear wall parallel to the internal base 13 of the ring 11.

The non-consecutive lateral walls of the secondary portion 12 of the piece 9 are parallel to one another, while the consecutive lateral walls of the secondary portion 12 of the piece 9 are perpendicular to one another.

The register slot 7 extends until it opens at the external base 14 of the ring 1 1.

The register slot 7 has a cylindrical zone 15 for engaging the abutment 8 and a tapered zone 16 for guided access of the abutment 8 in the engagement zone 15.

The internal base 13 of the ring 1 1 has weight-relief openings 17 also functioning as reservoirs for an adhesive for joining the piece 9 to the base of the cylinder 2.

The weight-relief openings 17 are honeycomb-shaped or shaped as concentric circles or any other suitable geometry.

The weight-relief openings 37 can be obtained directly with the 3D printer.

The piece 9 has the internal base 13 of the ring 11 that matches the base of the cylinder 2 and the secondary portion 12 housed in a complemplementarily-shaped notch 18 present at the internal perimeter edge of the base of the cylinder 2.

Finally, the piece 9 can have graphic elements 19 for customising the sleeve 1 at the external base 14 of the ring 11.

The customising graphic elements 19 can identify the sleeve 1 and the measurements thereof, and can be obtained directly using the 3D printer, for example by feeding it to carry out alternated layers with the same material but in different colours.

The 3D printer for making the piece 9 can use a filament of plastic material that is deposited layer by layer up to obtaining the object in three dimensions according to the FDM (fused deposition modelling) method.

In particular, the filament is constituted by polymers (there are various diameters, with the most easily sourced on the market being 3 mm and 1.7 mm) heated by a resistance (up to temperatures of 250°C).

The filament is passed through a nozzle, which, layer after layer, gives shape to the object.

The minimum printable layer with this method is about 100 microns (0.1 mm) (depending on the model).

In a constructional variant, the 3D printer uses another printing method known as SLS - selective laser sintering.

This technology is much more refined than FDM, as it enables selective fusion of a means in a granular bed.

There is a laser which hits polymers and fuses them into very thin layers of plastic powders. The non-fused means is for supporting the projections and thin walls of the component which is produced, reducing the need for temporary auxiliary supports for the piece to be worked.

The level of precision of this printing technique is almost ten times greater than the FDM technique. The materials used for making the piece 9 in the above-mentioned 3D printers have hardnesses comprised in the whole interval of scales Sha and ShD and are typically rigid materials such as for example thermosetting polyurethane resins, or epoxy resins, or thermoplastic resins, TPU, polyamide resins, nylon, HD or LD polyethylene or other polyolefins or mixtures thereof.

Moreover, technical polymers such as ABS like, RUBBER like, PC like, DuraForm, Accura, AsA, ABSi. PPSF/PPSU, Ultem, ceramic materials, plastilines, metal, wood, glass, paper, etc. can be used.

These materials can be added-to in order to obtain several chemical-physical properties, for example flame-resistance, surface electrical resistivity, anti-shock, etc.

Metal additives can be included for increasing impact and wear resistance.

The sleeve for a flexographic printing machine as conceived herein is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept; furthermore, all the details are replaceable by technically equivalent elements.

In practice the materials used, as well as the dimensions, can be any according to the needs and the state of the art.