Printing blanket including a non-extensible backing layer and a relief area which may be mounted in a variety of lockup mechanisms

Abstract

A printing blanket is provided which may include a printable surface ply, a compressible ply, one or more reinforcing fabric plies, and a non-extensible backing layer comprising a polymeric material. The printing blanket has first and seconds ends which are adapted to be inserted into the gap of a printing blanket cylinder, where each of the first and second ends may include a relief area formed by removing or molding a portion of the blanket or by removing or molding a portion of the non-extensible backing layer such that the blanket may be mounted in a wide variety of printing presses using a number of different lock-up mechanisms.

Claims

1. A printing blanket mounted on a blanket cylinder, said blanket cylinder including a gap and a lockup mechanism within said gap; said printing blanket comprising at least a printable surface ply and a non-extensible backing layer comprising a polymeric material or a reinforcing material which has been impregnated with a polymeric material, said printing blanket having first and second ends inserted into said gap; wherein at least a portion of said blanket overlying said non-extensible backing layer and spaced inwardly from at least one end of said blanket has been removed or molded to form at least one relief area which extends across substantially the width of the blanket and which is defined by blanket walls on each side; wherein said at least one relief area is positioned in said gap immediately above said lock-up mechanism; and wherein said at least one relief area is adapted to permit the blanket to be fitted into said lockup mechanism without a reduction in gauge.

2. The printing blanket of claim 1 including a compressible ply positioned beneath said surface ply.

3. The printing blanket of claim 2 including at least one reinforcing fabric ply positioned beneath said compressible ply.

4. The printing blanket of claim 1 including at least one reinforcing fabric ply positioned beneath said surface ply and a compressible ply positioned beneath said reinforcing fabric ply.

5. The printing blanket of claim 3 wherein said portion of blanket which has been removed or molded comprises said printable surface layer, said compressible layer, and said at least one reinforcing fabric ply.

6. The printing blanket of claim 4 wherein said portion of blanket which has been removed or molded comprises said printable surface layer, said compressible layer, and said at least one reinforcing fabric ply.

7. The printing blanket of claim 1 wherein said non-extensible backing layer comprises an oriented polymeric material.

8. The printing blanket of claim 1 wherein said non-extensible backing layer comprises a polymeric material selected from thermoplastic and thermosetting polymers.

9. The printing blanket of claim 1 wherein said non-extensible backing layer comprises a reinforcing material selected from fibers, cord, woven or non-woven fabric, mesh, scrim, screen, film, and sheets.

10. The printing blanket of claim 1 wherein said non-extensible backing layer is oriented in at least one direction.

11. The printing blanket of claim 1 wherein said non-extensible backing layer has a thickness of from about 0.008 inches to about 0.025 inches (about 0.2 mm to about 0.6 mm).

12. The printing blanket of claim 1 including a sealant on at least a portion of the surface of said at least one relief area.

13. The printing blanket of claim 1 having an elongation of less than about 0.2% at loads of about 50 to 150 lbf/inch (about 8.9 to 26.8 kg-f/cm) of width.

14. The printing blanket of claim 1 wherein said at least one relief area has a triangular, rectangular, or curved cross-section.

15. The printing blanket of claim 1 wherein said at least one relief area has a trapezoidal cross-section.

16. The printing blanket of claim 14 including a beveled edge portion on said relief area.

17. The printing blanket of claim 15 including a beveled edge portion on said relief area.

18. The printing blanket of claim 16 wherein said beveled edge forms an angle of from about 10 to 30 with the surface of said blanket.

19. The printing blanket of claim 1 having a relief area spaced inwardly from each of said first and second ends of said blanket.

20. The printing blanket of claim 1 wherein said blanket has been formed at each end by cold forming, thermoforming, or solvent forming.

21. The printing blanket of claim 1 including blanket bars attached to said first and second ends.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view of a printing blanket including a non-extensible backing layer according to one embodiment of the present invention;

(2) FIG. 2A is an enlarged elongated view of the blanket of FIG. 1 illustrating relief areas formed at each end of the blanket;

(3) FIG. 2B is an enlarged view of one end of the printing blanket illustrating a preferred shape of the relief areas;

(4) FIG. 3 is a view of the blanket of FIG. 2A further illustrating a sealant in the relief area of the blanket;

(5) FIG. 4A is an enlarged view of a printing blanket including a relief area formed in the non-extensible backing layer at each end;

(6) FIG. 4B is an enlarged view of the blanket of FIG. 4A including a blanket bar attached to the relief area;

(7) FIG. 5 is a schematic view of the printing blanket of FIG. 2B mounted on a blanket cylinder;

(8) FIG. 5A is an enlarged view of a portion of the printing blanket of FIG. 5 showing detail of the gap into which the ends of the printing blanket are mounted; and

(9) FIG. 6 is an enlarged view of a portion of the printing blanket of FIG. 4B mounted in the gap of a blanket cylinder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) The printing blanket of the present invention including a non-extensible backing layer provides a number of advantages over prior metal or fabric backed blankets. Because the backing is comprised of a non-extensible material, it provides better print quality and printing efficiency over its operating life as it eliminates stretching and/or retensioning of the printing blanket during mounting and operation. And, by utilizing a polymeric material as a backing material, the printing blanket is less expensive to manufacture than blankets utilizing metal backings.

(11) In addition, the blanket of the present invention is significantly easier to mount in standard press lockups than blankets utilizing metal backings. By providing the printing blanket of the present invention with relief areas at each end, the blanket may be used in substantially all conventional types of lockup mechanisms without requiring any modifications to the mechanisms or the use of any special lockup procedures. The blanket may also be mounted in presses using plate-type lockup mechanisms. This provides advantages over conventional fabric backed tensioned blankets and prior art metal-backed blankets which are suitable for use in only a few types of lockup mechanisms.

(12) FIG. 1 illustrates a cross-sectional view of one embodiment of the printing blanket construction 10 of the present invention. The printing blanket 10 preferably includes at least an outer printing surface ply 12 which acts to transfer an inked image from a printing plate to a substrate, a compressible ply 14, one or more reinforcing fabric plies such as fabric plies 13 and 16, and a non-extensible backing ply 18. As shown, the plies 12, 14 and 16 are adhered to non-extensible backing layer 18 with an adhesive 20. The adhesive used to adhere the plies to the non-extensible backing layer may comprise any of a number of conventional adhesives including hot melt adhesives, pressure sensitive adhesives, and curable polymers including rubber, urethane, epoxies, and the like. Alternatively, the plies may be formed directly onto the non-extensible backing layer.

(13) The non-extensible backing layer 18 preferably comprises a polymeric layer including a reinforcing material therein. The polymeric material may comprise a thermoplastic or thermoset polymer. Suitable thermoplastic polymers include polyamides, polyesters, polypropylene, polyethylene, polyurethane, ethylene vinyl acetate copolymers and ionomers, polyvinyl chloride, ethylene-acrylic acid or ethylene-methacrylic acid copolymers, acid or anhydride modified polymers, and any other flexible or semi-rigid thermoplastic polymers, i.e., those polymers having a modulus which allow easy mounting on a press cylinder.

(14) Suitable thermosetting polymers include rubber, curable urethane, epoxy, polyester, polyamide, and any other flexible or semi-rigid crosslinked polymers.

(15) Alternatively, an oriented polymer film or sheet may be used as the non-extensible backing layer, either with or without the inclusion of a reinforcing material. One suitable oriented polyester film or sheet for use in the present invention is Mylar, available from DuPont. Other suitable oriented polymeric materials include nylon, polyethylene, polystyrene, polycarbonate, or polypropylene. It should be appreciated that where such oriented polymeric materials are used, it may not be necessary to include a reinforcing material, i.e., such materials are sufficiently non-extensible when used in a thickness of at least about 0.010 to 0.020 inches (0.25 mm to 0.51 mm) such that a reinforcing material is not needed.

(16) It should be appreciated that any suitable polymer may be used as long as it can be impregnated into the reinforcing material in a manner which provides sufficient rigidity to lock the fibers or fiber bundles of the reinforcing material to substantially restrict their relative movement such that the force required to elongate the non-extensible base layer is increased substantially. The polymer should also allow the non-extensible layer to remain flexible enough to permit mounting onto a printing cylinder.

(17) If desired, the polymeric material may optionally be oriented in one or more directions to provide a higher tensile modulus. Optionally, the reinforced non-extensible base layer may be oriented to provide greater strength and greater resistance to stretching when subjected to normal forces encountered in the printing process. The desired orientation may be achieved using machine direction orientation, stentoring, calendaring, roll orientation, pultrusion, and the like.

(18) Suitable reinforcing materials for use in the present invention include natural or synthetic materials including, but not limited to, nylon, cotton, rayon, wool, polyester, polypropylene, polyethylene, metals, carbon/graphite, and fiberglass. The reinforcing material may be in the form of fibers, cord, wire, woven or non-woven fabric or mesh, scrim, screen, film, and sheets. Any suitable reinforcing materials may be used as long as they provide the proper tension resistance while also being flexible enough to bend around a blanket cylinder for mounting.

(19) The polymeric material is preferably incorporated into the reinforcing layer by coating, extrusion, pultrusion, laminating, molding, or any other suitable method which allows the polymer to flow substantially into the free space within the reinforcing material. The polymeric material is substantially impregnated into the reinforcing layer such that elongation of the reinforcing layer is restricted by the polymer matrix.

(20) We have found that by impregnating the reinforcing layer with a polymeric material, the movement between the warp yarns, fibers, or fiber bundles, and fill yarns, fibers or fiber bundles is greatly restricted or locked. Typical printing blankets are characterized by elongations of 1 to 3% with a load of 50 lbf/inch of width. Embodiments of the blanket of the present invention have elongations of less than about 0.2% at loads of 50 to 150 lbf/inch (about 8.9 to 26.8 kg-f/cm) of width.

(21) As further illustrated in FIG. 2A, in one embodiment of the invention, a portion 22 of the printing blanket above the non-tensioned backing layer 18 is preferably removed at each end of the blanket so as to form relief areas 24. The portion 22 of the blanket which is removed may include the surface printing layer, compressible layer, reinforcing layer(s), etc. As shown in FIG. 2A, the portion of the layers which has been removed forms a trapezoidal-shaped relief area.

(22) The portions of the blanket are preferably removed by grinding, routing, skiving, cutting, ablating, or tearing. However, it should also be appreciated that the relief areas may be formed without removing a portion of the printing blanket. For example, the plies of the blanket may be molded or cast to form the desired relief configuration.

(23) It should be appreciated that while trapezoidal-shaped relief areas are shown in FIG. 2A, different shaped relief areas may be provided as long as the areas allow the blanket to be fitted into the lock-up mechanism with the desired tensioning. For example, the relief area may also be triangular or rectangular in shape.

(24) The most preferred relief shape is illustrated in FIG. 2B, which includes a beveled or contoured area 24 on the printing surface positioned at the start of the relief for at least the leading edge of the blanket as it rotates into the plate and printing nips. This beveled or contoured surface provides a reduced impact force as the blanket enters into the nip between the blanket and the printing plate and into the nip between the blanket and the printed substrate (paper) during normal press operation, thus providing reduced wear of the blanket surface, printing plate, and press equipment.

(25) As shown, the bevel/contour starts at point A and slopes away from the printing surface at a slight angle (10 to 30 degrees measured from the surface) and extends to a depth below the printing surface equal to approximately 0.005 to 0.010 inches (0.12 to 0.25 mm) at point B. The remaining portion of the relief may be any convenient shape. Optionally, the beveled or contoured surface may be achieved by positioning the start of the relief so that the blanket and blanket printing surface extends a short distance beyond the point at which the non-extensible base must be bent to fit into the press lockup. Preferably, the relief is positioned on the circumference of the blanket cylinder so that it closely aligns to the point at which the lockup gap begins and at the point where the blanket/non-extensible base must be bent sharply to fit into the lockup. This optimum positioning results in maximum printing length by placing the non-tensioned portion of the printing layer of the blanket closest to the edge of the lockup gap without extending substantially down into the gap. Also as shown in FIG. 2B, the ends of the blanket may include a blanket lockup bar 52. In addition to or as an alternative to the use of blanket bars, the ends of the blanket may be formed into a desired shape for fitting into a lockup mechanism. For example, the blanket ends may be formed by cold forming (bending), thermoforming, or solvent forming (softening with a solvent so that shaping can be achieved). The blanket ends may be formed as desired during blanket manufacture, when the relief area is formed, or just prior to mounting on a press.

(26) In the embodiment shown in FIG. 3, an optional sealant 26 is preferably applied to the relief areas to prevent the entry of water, inks, or chemicals into the exposed edges of the blanket. The sealant may comprise any conventional sealant that provides chemical and moisture resistance including, but not limited to, epoxies, hot melts, polyamides, polyesters, polyurethanes, moisture, UV and RF curable adhesives, fluorosilicones, fluoropolymer-based materials, and acrylic-based sealants and adhesives.

(27) Referring now to FIGS. 4A and 4B, an alternative embodiment of the blanket is shown in which relief areas 60 are provided in the non-extensible layer 18 at each end of the blanket. The relief areas are preferably formed by grinding, skiving, cutting or any other means which provides the desired relief configuration. However, it should be appreciated that the relief areas may be formed without removing a portion of the non-extensible layer. For example, a portion of the non-extensible layer of the blanket may be molded or cast to form the desired relief configuration. As shown in FIG. 4B, a blanket bar or tab 62 is preferably attached to the relief areas 60 at each end of the blanket. The blanket bar may be attached to the ends of the blanket by crimping or gluing. The blanket bar or tab 62 is preferably comprised of a material such as aluminum, stainless steel, a reinforced polymeric material, or any other material which may be bent or formed for insertion into a lockup mechanism. A preferred bar material is stainless steel having a thickness of about 0.006 to 0.012 inches (0.15 to 0.30 mm).

(28) An alternative bar material may comprise a polymer or reinforced polymer that may be bent or formed for insertion into the lockup. The blanket bar(s) are preferably designed to be bent or formed and fitted into a plate lockup mechanism of a blanket cylinder as will be described in further detail below. Suitable forming methods include cold forming (such as, for example, bending), hot forming (where the material is a polymer, this would encompass thermoforming), or solvent forming (for example, using a solvent to soften a polymer so that it can easily be bent to the desired shape).

(29) The printing blanket including the relief areas allows the blanket to be used in substantially all types of conventional lock-up mechanisms. FIG. 5 illustrates a portion of a typical offset lithographic printing apparatus 30 which includes a blanket cylinder 32 with printing blanket 10 mounted thereon, where the printing blanket includes relief areas formed from a portion of the printing blanket layers. The blanket cylinder 32 includes an axially-extending gap 34 having first and second edges 36 and 38, respectively, which form a gap having a width W (see FIG. 5A). It should be appreciated that the lockup shown in FIG. 5A has been illustrated in general form to represent most conventional lockup mechanisms.

(30) FIG. 5A is an enlarged view of the printing blanket in the area of the gap. As shown, the leading and trailing ends 42, 40 of the printing blanket including the non-extensible layer 18 are bent and inserted into the gap 34 to secure the blanket to the blanket cylinder 32. The ends 42, 40 are preferably secured to blanket bars 52. As shown, the relief areas 24 allow the ends of the blanket to be easily bent and inserted into the gap. Preferably, the relief areas are positioned on the circumference of the blanket cylinder so that they closely align to the point at which the lock-up gap begins and at the point where the blanket/non-extensible base must be bent sharply to fit into the lock-up.

(31) FIG. 6 illustrates an enlarged view of the printing blanket of FIG. 4B mounted in the area of the gap. As shown, the blanket bars 62 attached to the relief areas at the leading and trailing ends 40, 42 of the printing blanket are bent and inserted into the gap 34 to secure the blanket to the blanket cylinder 32. It should be appreciated that the lockup shown in FIG. 6 has been illustrated in general form to represent most plate lockup mechanisms.

(32) Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention.