ITMI20010091A1 - MULTI-LAYER PRINT SLEEVE - Google Patents

Description

Description of an invention patent in the name

Printing sleeves are commonly used in a plurality of applications, including flexographic and intaglio printing. In particular, a printing sleeve which generally has a cylindrical shape can be mounted on a rotating printing cylinder for printing images on a substrate.

A plurality of mechanisms can be used to mount the printing sleeve on the printing cylinder. For example, "air mounting" is a common way of mounting a printing sleeve. Air mounting generally refers to placing a printing sleeve on a printing cylinder by supplying pressurized air between the sleeve and the cylinder. Typically, the printing sleeve has an inner surface diameter which is slightly smaller than that of the outer surface of the printing cylinder. The difference in these diameters is a dimension known as an "interference fit". Therefore, by applying pressurized air the diameter of the printing sleeve can be slightly expanded so that the sleeve can be mounted on and / or removed from a printing cylinder.

In some cases, an air-mountable print sleeve can be made with multiple concentric layers. In particular, most print jobs involve "image repetition" which is the circumferential length of the image that needs to be printed one or more times on a substrate. The circumference of a printing can be large enough to accommodate one or more repetitions of images. Also, different print jobs may involve image repetitions that differ in size, and consequently, different print jobs may require print sleeves which also differ in size. For example, a one-repeat size of a larger sleeve requires a printing sleeve with a larger circumference or outer diameter for the same diameter as the printing cylinder.

To perform a job that requires a larger sleeve repeat size, the diameter of the outer surface of that sleeve must be large enough to achieve the desired larger repeat size. Thus, printing sleeves obtained with multiple layers are generally employed to provide the necessary radial thickness. Specifically, multilayer printing sleeves have the effect of increasing the diameter of the sleeve to provide a larger repeat size so that the sleeve can be mounted on a smaller diameter printing cylinder that is already available in inventory. .

For example, one type of multilayer sleeve which is currently employed in the prior art comprises an inner core layer which is made from wound glass fibers coated with epoxy resin. One version of this sleeve contains a bridge layer made of polyurethane (for example, ISA-PUR 2340 placed on the outer surface of the core layer). However this sleeve is generally not capable of being air mounted on a cylinder at standard operating pressures (e.g. 80 to 90 psi - i.e. about 5.52 to 6.21 bar -) unless the thickness of the printing sleeve is less than 0.250 inches (about 0.63cm). In particular, it was believed that a compressible layer was required to form such air-mountable multilayer printing sleeves with thicknesses greater than 0.250 inches (about 0.63 cm).

For example, sleeves having a thickness greater than 0.250 inches (approximately 0.63 cm) contain a compressible layer with elastic properties to absorb the radial expansion of the core. The compressible layer is disposed on the outer surface of the core layer and is typically made of open cell urethanes (e.g. a polyether / polyester polyurethane foam sold as Scotch-Mount ™ 4032 by the Minnesota Mining and Manufacturing Company) or a material made of rubber. In general, the compressible layer usually has a thickness of between 0.0030 and 0.250 inches (about 0.0076-0.63 cm).

In addition to the aforementioned layers, the state of the art multilayer sleeve also contains one or more layers which add thickness to the sleeve. For example materials such as rigid polyurethane foam or other forms of polyurethane (e.g. ISA-PUR 2330 and ISA-PUR 2340 which are sold by H.B. Fuller Austria, NOMEX® which is sold by DuPont, and honeycomb structures) , are used by the sleeves of the state of the art. The thickness of these layers varies according to the particular image repetition used, but is typically less than 3 inches (about 0.7 cm). In addition, other outer layers are sometimes arranged on the outer surface of these layers.

However, a problem associated with such multilayer printing sleeves is that the compressible layer of the hands tends to disintegrate after a certain period of time. More specifically, when the sleeve is used to impart an image onto a substrate for a period of about 1 to 2 years, the open cell structure of the polyether polyurethane foam layer, for example, gradually breaks down. As a result, the tolerance (or smoothness) of the outermost surface of the sleeve decreases. In particular, "TOTAL INDICATED RUNOUT" often decreases to values greater than 0.001 inches (0.0025 cm), which causes the sleeve to be unsuitable for most printing applications. Therefore, when the compressible layer is destroyed, users of the current sleeves or "converters" must replace these damaged sleeves with new and expensive sleeves.

As such, there is a present need for an improved multilayer printing sleeve which is capable of being air-mounted on a printing cylinder. In particular, there is a need for a printing sleeve having a thickness greater than about 0.250 inches (0.63 cm) and which can be sufficiently expanded without deteriorating to the point of being unsuitable for most printing applications.

The purpose of the present invention is to offer a printing sleeve which solves the problems of known machines and which offers an answer to the aforementioned needs.

These and other objects which will be evident to the skilled in the art are achieved by a printing sleeve according to the attached claims.

The present invention is generally directed to a printing sleeve for use in flexographic or intaglio printing applications. In particular, a printing sleeve of the present invention contains a bridge layer which is For example, at air pressures between about 80 and 90 psi (i.e. about 5.52 and 6.21 bar), the printing sleeves of the present invention typically expand in a radial direction between approximately 0.0015 and 0.0045 inches (i.e. approximately 0.0038 cm and 0.0011 cm), and more particularly between approximately 0.0025 and approximately 0.0035 inches (i.e. approximately 0.0063 and 0.0088 cm). For example, in one embodiment, a printing sleeve having a diameter of less than 7 inches (about 17.78 cm) expands in a radial direction by about 0.0025 inches (i.e., about 0.0063 cm). Also, in another embodiment, a printing sleeve having an inner diameter greater than 7 inches (i.e. 17.78 cm) expands, in a radial direction, by about 0.0035 inches (i.e., about 0.0088 cm).

In general, the bridge layer can also have a plurality of thicknesses. In most embodiments, for example, the thickness of the bridge layer is between about 0.125 and 1.50 inches (i.e., about 0.31 cm and 3.81 cm), and more particularly between about 0.125 inches to about 1 inch (i.e. 0.31cm and 2.54cm).

Furthermore, a sleeve of the present invention can also comprise one or more outer layers

bridge. The outer layer or layers can be used to add additional thickness to the sleeve or as a cover layer for the sleeve. In general, any number, size, shape, and / or type of outer layers can be employed in the present invention as long as the resulting printing sleeve can be air-mounted on a printing cylinder. For example, some suitable materials which may be employed in forming an outer layer include, but are not limited to, epoxy resin bonded aramid fiber or polyester resin; reinforced polymeric material such as reinforced glass fiber bonded with the epoxy resin or polyester resin, the latter two being also known as glass fiber reinforced epoxy resin or glass fiber reinforced polyester; MYLAR® DUPONT® or KEVLAR® trilaminar; a polyurethane material (for example ISA-PUR 2330 or ISA-PUR 2340 produced by H.B. Fuller, Austria under the trade name of ISA-PUR 2330); rubber elastomeric materials; polyurethane elastomeric materials; expanded polyurethane foam; open cell polyurethane foam; nickel; carbon-reinforced epoxy resin; and similar. In another embodiment, an outer metal layer, such as an extruded aluminum layer, can also be pressed onto the bridge layer.

Furthermore, the outer layer or layers can also be made of rigid material or non-rigid material. For example, in one embodiment an outer layer can be made of polyurethane material having a Shore D hardness of between about 75 to about 85. In addition, the outer layer or layers can also have any desired thickness, so that the total thickness of the printing sleeve is greater than approximately 0.250 inches (i.e. approximately 0.63 citi). For example, in one embodiment, an outer layer has a thickness greater than 0.050 inches (about 0.12 cm) particularly between about 0.065 and 0.250 inches (i.e., between about 0.16 and 0.-63 cm) and more particularly between about 0.075 and 0.200 inches (i.e. between about 0.19 and 0.5 cm).

As a result of the present invention, the printing sleeves can be made without a compressible layer disposed adjacent to the outer surface of the core layer. By eliminating such a compressible layer, the printing sleeves of the present invention are believed to be more durable and better maintain TIR tolerances than the prior art printing sleeves. In particular, a generally rigid bridge layer that can expand during assembly and disassembly can provide the printing sleeve with durability properties.

Other features and aspects of the present invention are discussed in greater detail below. For a better understanding of the invention, the following drawing is attached, purely by way of non-limiting example, in which:

fig. 1 is a top perspective view of a printing cylinder on which a can be air-mounted. printing sleeve according to the present invention;

fig. 2A is a top perspective view of an embodiment of a printing sleeve made according to the present invention;

fig. 2B is a cross-sectional view taken along the line indicated by the references 2B-2B in fig. 2A;

fig. 2C is an enlarged sectional view of the part of the printing sleeve indicated with A in fig. 2B;

fig. 3A is a top perspective view of an alternative embodiment of a printing sleeve made according to the present invention;

fig. 3B is a cross-sectional view taken along the line indicated by the references 3B-3B in fig. 3A;

fig. 3C is an enlarged sectional view of a portion of the printing sleeve illustrated in FIG.

3B and indicated with B;

fig. 4A is a top perspective view of an alternative embodiment of a printing sleeve made according to the present invention;

fig. 4B is a cross-sectional view taken along the line indicated by the references 4B-4B in fig. 4A; And

fig. 4C is an enlarged sectional view of a part of the printing sleeve indicated by C in fig. 4B.

The repeated use of reference characters in the present disclosure and in the drawings is intended to represent identical or similar features or identical or similar elements of the invention.

Reference will now be made in detail to embodiments of the invention, one or more examples of which are indicated below. Each example is provided by way of explanation of the invention, not of limitation thereof. In fact, it will be clear to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention itself. For example, features illustrated or described as parts of one embodiment may be employed in another embodiment to achieve a further embodiment. Therefore, the present invention is intended to cover such modifications and variations and their equivalents.

In general, the present invention is directed to an improved printing sleeve for use in flexographic or intaglio printing. In particular, the present invention is directed to a durable, multilayer printing sleeve which is capable of expanding, for example, between about 0.0025 and about 0.0035 inches (i.e., between about 0.0063 cm and about 0.0088 cm) without the use of a compressible layer. For example, in one embodiment of the present invention, the printing sleeve is greater than about 0.250 inches (0.63 cm) thick and comprises a generally rigid, relatively expandable bridge layer disposed adjacent the core layer.

With reference to Figures 1, 2A-2C, 3A-3C, and 4A-4C, an embodiment of a printing sleeve of the present invention is illustrated therein. Printing sleeves are generally cylindrical and can have parallel or tapered cores according to the different types of printing cylinders available (parallel or tapered).

As shown in Figures 1 and 2A, for example, a generally cylindrical printing sleeve 10 is provided which can be mounted on the outer surface 12 of a printing cylinder 13. As is typical, the printing sleeve 10 has a smaller inner diameter. relative to the outside diameter of the printing cylinder 13. Further, in this embodiment, the printing cylinder 13 has holes 15 arranged around the circumference of one end of the printing cylinder which are capable of supplying pressurized air through a valve 16 from an air source (not shown). Although any pressure can be given pressures in excess of about 65 pounds per square inch (psi), i.e. equal to about 4.48 bar, and more particularly between about 80 and about 90 psi (corresponding to about 5.52 and 6.21 bar), are typically used.

By supplying pressurized air, the diameter of the printing sleeve 10 can be slightly increased so that the latter can fit onto the outer surface 12 of the printing cylinder 13. Specifically, to mount the printing sleeve 10 on the cylinder 13, a user can simply position it on the cylinder 13 when the pressurized air is simultaneously supplied to the latter. Once positioned on the cylinder 13, the pressurized air can be suspended, with the consequence that the sleeve 10 contracts on the cylinder remaining tightly retained on the printing cylinder 13. To use the printing sleeve 10 a printing plate (not shown), which defines the image to be printed on the. substrate (not shown), can then be attached to the outer surface 14 of the printing sleeve 10.

Illustrative embodiments of a printing sleeve of the present invention are shown in greater detail in Figures 2A-2C, 3A-3C, and 4A-4C. For example, as shown in Figures 2A-2C, the printing sleeve 10 comprises a core layer 20 having a generally cylindrical shape which constitutes the innermost portion of the printing sleeve. As shown, the core layer 20 has a cylindrical inner surface 21 and a cylindrical outer surface 22 which is generally concentric with the inner surface 21. The cylindrical inner surface 21 of the core layer 20 thus defines a hollow inner region 24 of the printing sleeve 10, which allows the inner surface 21 of the core layer 20 to be positioned on the outer surface 12 of the printing cylinder 13.

In general, any one of a plurality of materials used in the production of printing sleeves can be used to make the core layer. In some embodiments, the core layer of the printing sleeve is made of an expandable, high-rigidity material. The aforesaid materials are expandable in such a way that the core layer 20 can be repeatedly expanded and contracted without negative consequences in order to form an interference fit with the outer surface of a printing cylinder. The permitted degrees of expansion and contraction should not be so large as to be detectable with the naked eye.

Some examples of compositions which are suitable for obtaining the core layer 20 include, but are not limited to, an aramid fiber bonded with epoxy or polyester resin; a reinforced polymeric material such as hardened glass fiber bonded with epoxy resin or polyester resin, the latter being also known as glass fiber reinforced epoxy or glass fiber reinforced polyester; MYLAR® DUPONT® KEVLAR® or trilaminate which can optionally be reinforced with a resin, such as an epoxy resin; nickel; carbon-reinforced epoxy resin; and similar. Further, the core layer 20 can also be made in a manner similar to the printing sleeves described in U.S. Pat. 4,144,812 to name. Julian or in U.S. Pat. 4,903,597 in the name of Hoege et al., Modalities which are incorporated in this text in their entirety by reference to these patents. The radial thickness of the core layer 20 can also vary, depending on the desired application. For example in some embodiments, the core layer 20 may have a thickness between about 0.020 and about 0.100 inches (corresponding to about 0.05 cm and about 0.25 cm), the wider thicknesses being used for sleeves with larger diameters and / or or higher axial length. For example, in a particular embodiment, the core layer 20 is made of wound glass fiber which is coated with epoxy resin having a thickness of 0.040 inches (corresponding to about 0.10 cm).

The printing sleeve of the present invention comprises a bridge layer having a generally cylindrical shape. In the past, layers have been used to obtain a print sleeve with increased thickness for large image repeats. It was thought, however, that a non-rigid compressible layer (e.g., polyurethane foam or polyester / polyether foam) was required for sleeves having thicknesses greater than about 0.250 inches (0.63 cm). In particular, a compressible layer having a Shore A hardness of about 25-30,

For example, it has been placed between the soul organ and one or more layers to allow the soul organ to expand.

The inventors of the present invention, however, have discovered that a generally rigid, relatively expandable bridge layer can be employed to increase the thickness of a printing sleeve, as well as to allow the core member to expand adequately for mounting and loosening. dismounting of the sleeve on a printing cylinder. Furthermore, it has also been unexpectedly discovered that such expansion can be achieved without the use of a non-rigid compressible layer.

For this purpose, as shown in Figures 2A-2C, a cylindrical inner surface 31 of a bridge layer 30 can be arranged on an outer surface 22 of the core layer 20. The bridge layer 30 further comprises a cylindrical outer surface 33 which it is generally concentric with the inner surface 31. In most embodiments, the bridge layer 30 is made of any material which is generally rigid. As used herein, the term rigid refers to a material having a certain Shore hardness. In some embodiments, for example, the bridge layer may be made from a material having a Shore D hardness of between about 20 and about 85, and particularly between about 45 and about 50. However, it should be understood that the hardness values given above are only examples of materials with suitable stiffness. In particular, the required hardness can be lower or higher than the values indicated above, depending on a plurality of factors, such as the thickness of the sleeve and / or the thickness of the bridge layer, the diameter of the sleeve and / or the bridge layer. , the axial length of the sleeve and / or bridge layer, the amount of air pressure applied to mount or dismount the sleeve, the interference fit used, etc. For example, a stiffer material may be used for the bridge layer when higher air pressures are applied during assembly or disassembly.

In addition to being generally rigid, the bridge layer 30 is also relatively expandable. As used herein, the term "expandable" refers to a material that can expand to a certain radial distance following the application of air at a certain pressure. For example, at pressures between about 80 and 90 psi (corresponding to about 5.52 bar and 6.21 bar), the printing sleeves of the present invention can typically expand in a radial direction between about 0.0015 and about 0.0045 inches ( i.e. about 0.0038 cm and about 0.0011 cm) and more particularly between about 0.0025 and about 0.0035 inches (corresponding * to about 0.0063 and 0.0088 cm). However, the required amount of expansion for the sleeve can generally vary as a function of a plurality of factors, such as the diameter of the sleeve, the interference fit used, the axial length of the sleeve, etc. For example, in one embodiment, a printing sleeve having a diameter of less than 7 inches (corresponding to about 17.78 cm) expands about 0.0025 inches (corresponding to about 0.0063 cm) in a radial direction. Also, another embodiment, a printing sleeve, having a diameter greater than 7 inches (corresponding to about 17.78 cm) expands about 0.0035 inches (corresponding to about 0.0088 cm) in a radial direction. In general, the bridge layer 30 can also have a plurality of thicknesses. In particular, the thickness used can vary according to a plurality of factors, such as the hardness of the material, the diameter of the sleeve and / or the bridge layer, the axial length of the sleeve and / or the bridge layer, the amount of pressure d air applied to assemble or disassemble the sleeve, the interference fit used, etc. In most embodiments, however, the thickness of the bridge layer 30 is between about 0.125 and about 1.50 inches (corresponding to about 0.31 cm and about 3.81 cm) and particularly between about 0.125 and about 1 inch (corresponding to about 0.31 and 2.54 cm, respectively). For example, in a particular embodiment, as shown in Figures 2A-2C, a polyurethane material having a Shore D hardness between about 45 and about 50 can be used to obtain the bridge layer 30. Such a polyurethane material can be obtained by H.B. Fuller, Austria, under the trademark ISA-PUR 2330. If desired, other materials can also be used bonding with polyurethane material to obtain the bridge layer 30. For example a hardener and / or a thixotropic material can be combined with the polyurethane material to assist in forming the layer on the outer surface of the core layer. Such materials can also be obtained from the company H.B. Fuller, Austria. With reference to Figures 3A-3C and 4A-4C, a sleeve of the present invention can also contain one or more outer layers in addition to the core layer and the bridge layer. The outer layer (s) can be used to achieve a further thickness to the sleeve or as a cover layer for the sleeve. For example, as shown in Figures 3-3C, a sleeve 110 may contain, a core layer 120, a bridge layer 130, and a generally cylindrical outer layer 140. The inner surface 141 of the outer layer 140 may be disposed on the surface. 133 of the bridge layer 130. In another embodiment, as shown in Figures 4A-4C, a sleeve 210 contains a core layer 220, a bridge layer 230, a first outer layer 240 and a second outer layer generally cylindrical 250. As illustrated, the inner surface 233 of the outer layer 250 is disposed on the outer surface 241 of the outer layer 240. In general, the outer layer or layers can be made from any plurality of materials. For example, some materials which may be employed in forming an outer layer include, but are not limited to, an aramid fiber bonded with epoxy or polyester resin; reinforced polymeric material such as hardened glass fiber bonded with epoxy resin or polyester resin, these two being also known as glass fiber reinforced epoxy resin or glass fiber reinforced polyester; MYLAR® DUPONT® or KEVLAR® trilaminate; a polyurethane material (for example, ISA-PUR 2330 or ISA-PUR 2340 obtainable from H.B. Fuller, Austria, under the trade name ISA-PUR 2330); rubber elastomeric materials; polyurethane elastomeric materials; polyurethane foam expands; open cell polyurethane foam; nickel; epoxy resin reinforced with carbon and similar. In another embodiment, an outer metal layer, such as an extruded aluminum layer, can also be pressed onto the bridge layer. Furthermore, the outer layer or layers can also be made of a rigid material or a non-rigid material. For example, as shown in Figures 3A-3C, the outer layer 140 may generally be a rigid material having a hardness greater than the hardness of the bridge layer 130. For example, in one embodiment, an outer layer 140 is made of a polyurethane material having a Shore D hardness of about 75 to about 85. An example of such a polyurethane material is the material sold by H.B. Fuller, Austria under the trade name of ISA-PUR 2340.; In general, the outer layer (s) can also have any desired thickness, as long as the total thickness of the resulting printing sleeve is greater than approximately 0.250 inches (corresponding to approximately 0.63 cm). For example, in one embodiment as shown in Figures 3A-3C, the outer layer 140 is made of ISA-PUR 2340, a hardener and a thixotropic material so that the resulting layer 140 has a thickness greater than about 0.050 inches (corresponding to about 0.127 cm) particularly between about 0.065 and about 0.250 inches (corresponding to about 0.16 and 0.63 cm) and more particularly between about 0.075 and 0.200 inches (corresponding to about 0.19 and 0.5 cm). The outermost surface of the printing sleeve, for example, an outer surface 255 of the outer layer 250, can also be provided with a smooth finish up to a tolerance capable of supporting a printing sleeve thereon. In fact, the outer surface 250 is normally sufficiently smooth so that the indicated combined total runout (TIR) of the printing sleeve mounted with the printing plates is less than 0.001 inches (corresponding to about 0.0025 cm). Furthermore, if desired, the outer surfaces of the other layers, such as the bridge layers 30, 130, 230 or the outer layers 140 or 240, can also be provided with a smooth finish. Furthermore, the printing sleeve can also be made with additional features, such as gas passages from the inner core to the outer surface, internal gas passages, spacer rings, etc., at least some of which are indicated in U.S. Pat. . 5819657 in the name of Rossini, which is incorporated into this text in its entirety by reference to it. Printing sleeves of the present invention may also be provided with other common features which are well known in the state of the art. For example, printing cylinders are commonly provided with a register pin to facilitate the repetitive orientation of the printing sleeve on them by means of a key or slot made in the sleeve. For such printing cylinders, the printing sleeve of the present invention can be provided with a key or similar slot to adapt to such printing cylinders and / or a pin or the like to adapt to such printing sleeves.

The printing sleeves made according to the present invention can provide various benefits to the user (i.e., the converter). For example, by eliminating the compressible layer of the outer surface of the core layer, the printing sleeves of the present invention are believed to be more durable and better maintain TIR tolerances than the prior art printing sleeves. In particular, a generally rigid, relatively expandable bridge layer can provide a printing sleeve with durable properties for extensive use by a converter.

The present invention can be better understood with reference to the following examples.

EXAMPLE 1

The ability of a printing sleeve of the present invention to be placed on a printing cylinder has been demonstrated. Initially, the core layer was made using glass fibers. Specifically, a flat ribbon wrapped of glass fiber having a width of about 1 inch (i.e. about 2.54 cm) was passed through an epoxy resin bath. . Thereafter, the web was wound around an undersized forming roll from one end of the mandrel to the opposing second end of the roll, as described in U.S. Pat. 5819657 in the name of Rossini. Specifically, the fiberglass-soaked tapes were repeatedly wound back and forth along the barrel until enough wraps were applied to produce a resin-reinforced fiberglass core layer with a radial thickness of 0.060 inch. (corresponding to about 0.15 cm) Next, the barrel and the resin-reinforced fiberglass core still wrapped around the mandrel were placed in a hot air oven for several hours to cure the core within a fiber precursor tube. glass-reinforced polymer. Then the sleeve and cylindrical mandrel were removed from the oven and cooled to room temperature. The cooled core layer was then ground to a thickness between about 0.040 and about 0.045 inches (corresponding to about 0.10 and 0.11 cm). The surface of the core layer was cleaned with a solvent.

After the core layer was made, the bridge layer was then formed. In particular, ISA-PUR 2330 was obtained from H.B. Fuller, Austria, to apply it to the core layer. The ISA-2330 product was combined with a thixotropic agent and a hardening agent which were also obtained from H.B. Fuller, and extruded onto the core layer, which was - placed on a rotating cylinder. During the application of the bridge layer, the extruder was moved in the direction of the axial length on the core layer. Specifically, the extruder was moved twice from one end of the barrel to the other end while depositing the bridge layer material onto the core layer. The resulting bridge layer was approximately 0.375 inches thick (corresponding to approximately 0.95 cm).

An outer layer was then applied to the outer surface of the unfinished bridge layer. In particular, ISA-PUR 2340 was obtained from H.B. Fuller, to apply it to the bridge layer. The ISA-2340 product was also combined with a thixotropic agent and a hardening agent, which were also obtained from H.B. Fuller and extruded on a bridge layer placed on the rotating cylinder. During the application of the outer layer the extruder was moved axially above the core layer. Specifically, the extruder was moved once from one end of the barrel to the other end and during deposition of the outer layer material onto the bridge layer. The resulting outer layer was approximately 0.250 inches thick (corresponding to approximately 0.63 cm).

After the realization of the above layers the whole sleeve was dried for about 5 days at room temperature (or it could have been dried 4 days in a hot oven). Once dried, the sleeve was removed from the oven and ground to have a generally smooth outer surface with an IRR of less than 0.0005. The sleeve was then cut to a finished length of 62 inches (corresponding to approximately 167 cm). The resulting sleeve had an outer layer (i.e. ISA-PUR 2340) with a final hardness of 75 Shore D and a bridge layer (i.e. ISA-PUR 2330) with a final hardness of 46 Shore D. Furthermore, the resulting sleeve had a core layer and a thickness of 0.040 inches (corresponding to approximately 0.10 cm), a bridge layer with a thickness of 0.350 inches (approximately 0.88 cm) and an outer layer with a thickness of 0.088 inches (corresponding to about 0.22 cm). The sleeve also had a finished diameter of 8.344 inches (i.e. about 21.19 cm).

The ability of the finished sleeve to be placed on the external surface of a printing cylinder was then tested. In particular, a printing cylinder has been provided having a diameter of 7.389 inches (i.e. about 18.76 cm) and the possibility of dispensing pressurized air through its external surface. Thereafter, an air pressure of 90 psi (approximately 6.21 bar) was then fed to the holes in the printing cylinder. The entire length of the finished sleeve was placed on the outside surface of the printing cylinder with relative ease. In particular, the air pressure had the effect of sufficiently expanding the inner surface of the sleeve to allow it to slide easily over the outer surface of the printing cylinder.

Once the entire sleeve was placed on the printing cylinder, the pressurized air was cut off. Thus the inner surface of the sleeve layer contracted and said sleeve remained mounted on the outer surface of the printing cylinder. The sleeve was then removed by essentially the same process by which it was mounted on the printing cylinder.

EXAMPLE 2

The possibility of a printing sleeve according to the present invention to be placed on a printing cylinder has been proved. Initially, a core layer was made as described in Example 1. After making the core layer, the bridge layer was then made. In particular, ISA-PUR 2330 was obtained from H.B. Fuller to apply it to the core layer. ISA-2330 was combined with a thixotropic agent and a hardening agent which were also obtained from H.B. Fuller, and extruded onto the core layer, which was placed on a rotating cylinder. During the application of the bridge layer, the extruder was moved in a longitudinal direction above the core layer. Specifically, the extruder was moved three times from one end of the barrel to the other end during deposition of the bridge layer material onto the core layer. The resulting bridge layer was approximately 0.875 inches thick or approximately 2.22 cm thick.

An outer layer was then applied to the outer surface of the unfinished bridge layer. In particular, ISA-PUR 2340 was obtained from H.B. Fuller for application on the bridge layer. The product ISA-2340 was also combined with a thixotropic agent and a hardening agent also obtained from H.B. Fuller and extruded on the bridge layer placed on the rotating cylinder. During the application of the outer layer, the extruder was moved in a longitudinal direction above the core layer. Specifically, the extruder was moved once from one end of the barrel to the other end during deposition of the outer layer material onto the bridge layer. The resulting outer layer. it had a thickness of approximately 0.300 inches (i.e. about 0.76 cm).

After obtaining the aforementioned layers, the entire sleeve was dried for about 5 days at room temperature (or it could have been dried for 4 days in a hot oven). Once dried, the sleeve was removed from the oven and ground to generally have a smooth outer surface with an IRR of less than 0.0005. The sleeve was then cut to a finished length of 45 inches (approximately 114.3 cm). The resulting sleeve had an outer layer (i.e. ISA-PUR 2340) with a final hardness of 78 Shore D and a bridge layer (i.e. ISA-PUR 2330) with a final hardness of 44 Shore D. Furthermore, the resulting sleeve had a core layer with a thickness of 0.040 inches (0.10 cm) and a bridge layer with a thickness of 0.860 inches (2.18 cm) and an outer layer with a thickness of 0.95 inches (about 0.24 cm). The sleeve also had a finished diameter of 5.161 inches (approximately 13.10 cm). The ability of the finished sleeve to be placed on the outer surface of a printing cylinder has been proven. In particular, a printing cylinder has been provided having a diameter equal to 3.172 inches (i.e. about 8.05 cm) and a possibility to dispense pressurized air through its external surface. Pressurized air of 90 psi (approximately 6.21 bar) was then supplied to the holes in the printing cylinder. The entire length of the finished sleeve was placed on the outside surface of the print cylinder with relative ease. In particular, the air pressure had the effect of sufficiently expanding the inner surface of the sleeve to allow the latter to slide easily on the outer surface of the printing cylinder.

Once the entire sleeve was placed on the printing cylinder, the pressurized air was cut off. Thus, the inner surface of the sleeve core contracted and remained mounted on the outer surface of the printing cylinder. The sleeve was then removed in essentially the same process by which the sleeve was mounted on the printing cylinder.

Although various embodiments of the invention have been described using specific terms, devices, and methods, such description is given for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations can be made by those skilled in the art without departing from the spirit or scope of the present invention which is indicated in the following claims. In addition, it should be understood that aspects of the various embodiments can be exchanged both in their entirety and in part. Therefore the spirit and scope of the following claims should not be limited to the description of the preferred versions contained herein.

Claims (15)

CLAIMS 1. Printing sleeve adapted to be mounted on a printing cylinder (13) provided with means (15) to allow the inflow of pressurized air on its external surface (12) so as to allow mounting on or dismounting from said surface of the printing sleeve (10), the latter being stratiform and comprising a core layer (20, 120, 220) hollow internally and provided with an internal cylindrical surface (21), said core layer (20, 120, 220 ) having an external cylindrical surface (22) generally concentric with the internal surface (21), the core layer (20, 120, 220) being obtained in an expandable material with high rigidity, the aforesaid core layer supporting a bridge layer (30, 130, 230) fixed to this core layer, characterized in that the bridge layer (30, 130, 230) is made of generally rigid and relatively expandable material so as to allow the sleeve (10) to expand and contract radially for assembly and disassembly 10 of the same on the printing cylinder (13), said radially expandable sleeve being devoid of a compressible layer placed on the cylindrical surface Printing sleeve according to claim 1, characterized in that the bridge layer (30, 130, 230) it is made of material with Shore D hardness between 20 and 85. 3. Printing sleeve according to claim 1, characterized in that the bridge layer (30, 130, 230) is made of material having a Shore D hardness between 45 and 50. 4. Printing sleeve according to claim 2 or 3, characterized in that the bridge layer (30, 130, 230) is made of material containing polyurethane. 5. Printing sleeve according to claim 4, characterized in that the bridge layer (30, 130, 230) comprises a hardener and / or a thixotropic material combined with the polyurethane. 6. Printing sleeve according to claim 2, characterized in that the bridge layer (30, 130, 230) has a thickness comprised between about 0.25 and 4 cm and preferably between 0.31 and 2.5 cm. 7. Printing sleeve according to claim 1, characterized in that it has an overall thickness greater than about 0.63 cm. 8. Printing sleeve according to claim 1, characterized in that it comprises at least one further outer layer (140, 240, 250) arranged on the outer surface (133) of the bridge layer (30, 130, 230). 9. Printing sleeve according to claim 8, characterized in that the outer layer (140, 240, 250) is made of composite material. 10. Printing sleeve according to claim 8, characterized in that the outer layer (140, .240, 250) is made of reinforced polymeric material. 11. Printing sleeve according to claim 8, characterized in that the outer layer (140, 240, 250) is made of polyurethane material. 12. Printing sleeve according to claim 8, characterized in that the outer layer (140, 240, 250) is made of rubber. 13. Printing sleeve according to claim 8, characterized in that the outer layer (140, 240, 250) is made of metal. 14. Printing sleeve according to claim 1, characterized in that it comprises internal channels for supplying pressurized air to the outer surface of the sleeve. 15. Printing sleeve according to claim 1, characterized in that it has a recess for the cooperation of an adjustment pin associated with the printing cylinder (13).