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(11) | EP 2 368 719 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | HIGH-STRENGTH, ULTRA-LIGHT INTERCHANGEABLE SLEEVE FOR SUPPORTING PRINTING OR ROLLING ELEMENTS SUBJECT TO HIGH WORKING PRESSURES |
| (57) The sleeve comprises a central tubular core (1) suitable for being coupled onto a
shaft, and a stratified structure (2) arranged on an outer surface of said tubular
core (1). The stratified structure (2) comprises a plurality of strata of a high-density
component overlaid radially and separated axially, forming helical or discoidal high-density
ribs (3b), a low-density component filling in separating spaces between the aforementioned
high-density ribs (3b) forming a low-density filling (4), and a plurality of strata
of a high-density component overlaid radially, forming a continuous high-density outer
layer (3c) supported on said high-density ribs (3b) and on said low-density filling
(4). |
Technical Field
[0001] The present invention relates to a high-strength, ultra-light interchangeable sleeve for supporting printing or rolling elements subjected to high working pressures which can be used, for example, in offset printers or rolling bodies.
Background of the Invention
[0002] Sleeves for printing or rolling cylinders formed by a central tubular core on which there is arranged a stratified structure of a polymeric material, such as polyurethane, are known. For the sleeves to be operative, i.e., for them to withstand high pressure loads on their outer surface, the polymer used is a high-density polymer. However, when the thickness of a sleeve is considerable, for example because it has to cover a large outer diameter with respect to the diameter of the tubular core, a continuous stratified structure of high-density polymer imposes a significantly high weight which makes it necessary for more than one operator or a controllable manipulator to manipulate the sleeve, making it difficult to use.
[0003] Sleeves for printing or rolling cylinders are also known in which, to lighten the weight the stratified structure comprises an optional continuous inner layer of high-density polymer in contact with the central tubular core, then a continuous intermediate layer of low-density polymer, and finally a continuous outer layer of high-density polymer. A drawback of this sleeve is that when it is subjected to the high working pressures that are common in the offset printing and in other types of printing or rolling, the intermediate layer of low-density polymer has the risk of giving way and due to considerable pressure stresses, the low-density intermediate layer is crushed and therefore loses the cylindrical shape of the sleeve. The low-density intermediate layer is furthermore exposed at the ends of the sleeve and tends to expand at said ends due to contact with atmospheric agents, which may end up affecting the cylindrical surface regularity and dimensional stability of the outer diameter of the sleeve.
[0004] Patent US-A-6688226 describes an apparatus for manufacturing sleeves for offset printing cylinders. The apparatus shown in Figure 2 of the publication of this patent comprises means for supporting and rotating a tubular core about an axis and an injection nozzle installed on a movable carriage which moves along a track parallel to the axis of the tubular core. Multiple radially overlaid strata of a solidifiable fluid polymer are deposited on an outer surface of the tubular core while the latter is rotating by means of the nozzle.
Description of the Invention
[0005] According to a first aspect, the present invention provides a high-strength, ultra-light interchangeable sleeve for supporting printing or rolling elements subjected to high working pressures. The sleeve is of the type comprising a central tubular core suitable for being coupled onto a shaft and a stratified structure arranged on an outer surface of said tubular core. The aforementioned stratified structure comprises a plurality of strata of one or more components with different densities overlaid radially with a continuous high-density outer layer. The sleeve of the present invention is characterized in that said stratified structure comprises a plurality of strata of a high-density component overlaid radially and separated axially, forming high-density ribs which can be helical or discoidal, a low-density component filling in separating spaces between the aforementioned high-density ribs forming a low-density filling, and a plurality of strata of a high-density component overlaid radially, forming the aforementioned continuous high-density outer layer which is supported on said high-density ribs and on said low-density filling.
[0006] Preferably, the sleeve of the present invention further comprises a plurality of strata of a high-density component overlaid radially, forming a continuous high-density inner layer in contact with said outer surface of the tubular core and on which the high-density ribs and the low-density filling are arranged. It is also preferable for the sleeve to have discoidal high-density enclosure walls formed by multiple strata at the ends of the sleeve and connected with the high-density inner and outer layers. A polymer such as polyurethane, for example, which can have different densities, is a suitable component for the stratified structure of the sleeves of the present invention. A suitable polyurethane for making the continuous inner layer, the continuous outer layer and the high-density ribs has, for example, a density comprised between 1.0 g/cm3 and 1.6 g/cm3. The density of the polyurethane for the low-density filling can be significantly low because in some cases the main function of the filling is to simply support the strata of the continuous high-density outer layer while they are being deposited.
[0007] As mentioned above, the high-density ribs can be of a helical or discoidal configuration. If the helical configuration is used, the stratified structure can comprise a single high-density rib of a helical configuration, two or more formations of high-density ribs of a helical configuration which may or may not be parallel with one and the same rotational direction, or two or more cross-linked formations of high-density ribs of a helical configuration with opposite rotational directions. When two or more formations of high-density ribs of a helical configuration are used, either with the same rotational direction or opposite rotational directions, they can all have one and the same helix pitch or different helix pitches. Likewise, each of the formations of helical ribs can optionally have a variable pitch.
[0008] In any case, the high-density ribs will be relatively thin in comparison with the spaces between them filled with the low-density filling, such that the sleeve can be very lightweight in comparison with the sleeves of the prior art, whereas the ribs and high-density enclosure walls support the continuous high-density outer layer substantially preventing the low-density filling from being crushed and assuring the cylindrical shape of the sleeve even under high working pressures. The discoidal enclosure walls further prevent the low-density filling from contacting with atmospheric agents at the ends of the sleeve and prevent the expansion thereof.
[0009] According to a second aspect, the present invention provides a method for manufacturing a high-strength, ultra-light interchangeable sleeve for supporting printing or rolling elements subjected to high working pressures. The method is of the type which comprises depositing multiple radially overlaid layers of a solidifiable fluid component of different densities on an outer surface of a tubular core while the latter is rotating by means of one or more injection nozzles installed on a movable carriage which moves on a track parallel to the axis of said tubular core. The method of the present invention is characterized in that it comprises depositing layers of a high-density component overlaid radially and separated axially to form helical or discoidal high-density rids, depositing a low-density component in separating spaces between the aforementioned high-density ribs to form a low-density filling therein, and depositing strata of a high-density component to form a continuous high-density outer layer supported on said high-density ribs and on said low-density filling.
[0010] Preferably, the method further comprises depositing strata of a high-density component to form a continuous high-density inner layer on said outer surface of the tubular core before depositing the high-density ribs and the low-density filling, such that the high-density ribs and the low-density filling are deposited on this continuous high-density inner layer. The method also contemplates forming enclosure walls made up of multiple strata of a high-density component at the ends of the sleeve to prevent the exposure of the low-density filling to atmospheric agents at the ends of the sleeve.
[0011] The method of the present invention can be carried out to practice using any one of the various apparatus well known in the state of the art of the type described in the aforementioned patent US-A-6688226. Different polymer deposition patterns can be obtained by selecting different combinations of rotational speeds and directions of the tubular core and movement speeds and directions of the injection nozzle. By simultaneously using one or more nozzles for the high-density component and one or more nozzles for the low-density component it is possible to deposit the high-density ribs and the low-density filling in one and the same operation when there are discoidal ribs or a single helical rib, or several parallel helical ribs with one and the same rotational direction. When there are cross-linked helical ribs with opposite rotational directions forming a grid, the ribs must first be formed by depositing the high-density component and curing, and the spaces between the ribs can then be filled in by means of the low-density component.
Brief Description of the Drawings
[0012] The foregoing and other features and advantages will be more fully understood from the following detailed description of several embodiments in reference to the attached drawings, in which:
Figures 1A and 1B are cross-section views of an ultra-light interchangeable sleeve according to a first embodiment of the present invention taken along a transverse plane perpendicular to the axis of the sleeve and along a longitudinal plane comprising the axis of the sleeve, respectively;
Figure 2 is a cross-section view of an ultra-light interchangeable sleeve according to a second embodiment of the present invention taken along a longitudinal plane comprising the axis of the sleeve;
Figure 3 is a cross-section view of an ultra-light interchangeable sleeve according to a third embodiment of the present invention taken along a longitudinal plane comprising the axis of the sleeve; and
Figure 4 is a cross-section view of an ultra-light interchangeable sleeve according to a fourth embodiment of the present invention taken along a longitudinal plane comprising the axis of the sleeve.
Detailed Description of several Embodiments
[0013] Referring first to the figures in general, the high-strength, ultra-light interchangeable sleeve for supporting printing or rolling elements subjected to high working pressures comprises according to any one of the embodiments shown a central tubular core 1 suitable for being coupled onto a shaft or rotating support (not shown) and a stratified structure 2 arranged on an outer surface of said tubular core 1. The aforementioned stratified structure 2 comprises a continuous high-density inner layer 3a in contact with said outer surface of the tubular core 1, helical or discoidal high-density ribs 3b arranged on said continuous high-density inner layer 3a, a low-density filling 4 also arranged on the continuous high-density inner layer 3a filling in separating spaces between said high-density ribs 3b, a continuous high-density outer layer 3c supported on said high-density ribs 3b and on said low-density filling 4, and discoidal high-density enclosure walls 3d closing the stratified structure 2 at the ends of the sleeve. The aforementioned high-density enclosure walls 3d are connected to the continuous high-density inner layer 3a and to the continuous high-density outer layer 3c.
[0014] The continuous high-density inner layer 3a, the high-density ribs 3b and the high-density enclosure walls 3d are made from a plurality of overlaid strata of a high-density component, such as polyurethane with a density comprised between 1.0 g/cm3 and 1.6 g/cm3 deposited on an outer surface of the tubular core 1. This high-density component is deposited when it is in a solidifiable fluid state by means of one or more injection nozzles (not shown) installed on a movable carriage which moves on a track parallel to the axis of said tubular core 1 while the tubular core 1 is rotating. The strata are overlaid radially and separated axially in the high-density ribs 3b and in the high-density enclosure walls 3d. The helical or discoidal configuration of the high-density ribs 3b is obtained by selecting different combinations of rotational speeds and directions of the tubular core 1 and movement speeds and directions of the injection nozzle or nozzles along the tubular core 1.
[0015] The low-density filling 4 is generally made from a plurality of strata of a low-density component, such as low-density polyurethane, deposited when the component is in a solidifiable fluid state similarly to that described above. The low-density component for the filling 4 can be deposited at the same time as the high-density component for the continuous high-density inner layer, ribs and enclosure walls 3a, 3b, 3d using independent nozzles. The continuous high-density outer layer 3c is made from a plurality of overlaid strata of a high-density component, such as polyurethane with a density comprised between 1.0 g/cm3 and 1.6 g/cm3 deposited on outer surfaces of the high-density ribs 3b, high-density enclosure walls 3d and low-density filling 4 using the component in a solidifiable fluid state by means of a technique similar to that described above. When the deposition of both high- and low-density components has finished, they are subjected to a curing process and finally the outer surface of the continuous high-density outer layer 3c can be rectified by means of a machining process.
[0016] Alternatively, in some cases, for example when a configuration of cross-linked high-density ribs forming a grid with multiple cells is used, the high-density component forming the high-density continuous inner layer, ribs and enclosure walls 3a, 3b, 3d can be deposited first, next this high-density component can be cured, then the low-density component forming the filling 4 can be deposited directly inside each cell and the high-density component forming the continuous high-density outer layer 3c can be deposited on the high-density ribs and enclosure walls 3b, 3d and low-density filling 4 and the high- and low-density components not previously cured can finally be cured.
Figures 1A and 1B show a first embodiment of the ultra-light interchangeable sleeve of the present invention where the stratified structure 2 includes a single high-density rib 3b of a helical configuration with a predetermined rotational direction. This single high-density rib 3b is connected to the continuous high-density inner and outer layers 3a, 3c and to the high-density enclosure walls 3d. Therefore, the low-density filling 4 has the shape of a helical block with the same rotational direction. The high-density rib 3b and the low-density filling 4 are illustrated with a constant helix pitch, although they could alternatively have a variable helix pitch along the length of the sleeve.
Figure 2 shows a second embodiment of the ultra-light interchangeable sleeve of the present invention where the stratified structure 2 includes two formations of high-density ribs 3b of a helical configuration with one and the same rotational direction. Both high-density ribs 3b are connected to the continuous high-density inner and outer layers 3a, 3c and to the high-density enclosure walls 3d, and the low-density filling 4 also has the shape of two helical blocks with the same rotational direction. It will be understood that this second embodiment can be extended to any other number of high-density ribs 3b greater than two.
Figure 3 shows a third embodiment of the ultra-light interchangeable sleeve of the present invention where the stratified structure 2 includes two formations of high-density ribs 3b of a helical configuration with opposite rotational directions, such that high-density ribs 3b are cross-linked forming a grid which defines multiple cells of an approximately rhombic configuration. In this case, both high-density ribs 3b are connected to the continuous high-density inner and outer layers 3a, 3c and to the high-density enclosure walls 3d, and the low-density filling 4 is configured as a plurality of approximately rhombus-shaped curved blocks. It will be understood that this second embodiment can be extended to any other number of high-density ribs 3b greater than two.
Figure 4 shows a fourth embodiment of the ultra-light interchangeable sleeve of the present invention where the stratified structure 2 includes a plurality of high-density ribs 3b of discoidal configuration parallel to the high-density enclosure walls 3d located at the ends of the sleeve. Said plurality of high-density ribs 3b are connected to the continuous high-density inner and outer layers 3a, 3c, and the low-density filling 4 is configured as a plurality of annular-shaped blocks.
depositing multiple axially separated strata of a high-density component to form helical or discoidal high-density rids (3b);
filling in separating spaces between the aforementioned high-density ribs (3b) with the low-density component to form a low-density filling (4) therein; and
depositing multiple strata of a high-density component to form a continuous high-density outer layer (3c) supported on said high-density ribs (3b) and on said low-density filling (4).
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description