Patent Publication Number: US-6669613-B1

Title: Printing roller having printing sleeve mounted thereon roller

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to printing presses, and more particularly, is directed to a printing roller having a printing sleeve mounted thereon, and a method for mounting and dismounting printing sleeves from the printing roller. 
     In the printing press art, printing sleeves are fit onto rigid, incompressible printing cylinders. The sleeves are relatively expensive to manufacture. 
     U.S. Pat. No. 4,903,597 to Honge et al discloses a method of mounting a sleeve on a printing cylinder by supplying pressurized air between the printing cylinder and the sleeve in order to enable the sleeve to slide onto the printing cylinder. As with conventional printing cylinders, the printing cylinder of Honge et al is made of a rigid material that is not compressible. However, the sleeve is made of an elastic or resilient material, and specifically, a polymeric laminate material which has a constant thickness and cross-sectional diameter. Initially, a portion of the sleeve is force fit onto the cylinder, and thereafter, pressurized air is supplied through the interior of the cylinder and then through radial oriented holes in the cylinder. As a result, the sleeve expands by the force of the air pressure, providing a cushion of air between the sleeve and the rigid printing cylinder. This permits the sleeve to easily slide over the printing cylinder. However, as with conventional methods, the sleeve is relatively expensive. Related inventions which disclose expanding the outer sleeve by means of air pressure are disclosed in U.S. Pat. No. 5,324,248 to Quigley and U.S. Pat. No. 5,497,549 to Rademacher. However, again, specialized and expensive sleeves must be used. 
     U.S. Pat. No. 4,378,622 to Pinkston et al discloses a method of making a compressible printing roller. The roller includes a rigid shaft having a microporous inner layer made of a rubber material thereon. The inner layer is made of a cured and leached rubber material with interconnected cavities defined therein such that the voids represent between 30% to 70% of the total volume of the microporous inner layer. A thin tubular outer layer made of any suitable polymeric material which is non-porous and of solid cross-section throughout and free of voids, is mounted on the inner layer. In order to do so, the inner layer is compressed, whereupon the tubular outer layer is inserted thereover. Then, the inner layer is released, whereupon it expands and grabs the outer layer. The means for compressing the inner layer is a metal sleeve tool placed around the tubular inner layer, which is removed after the tubular outer layer is placed over the inner layer. It is clear from this patent that the outer layer is not intended to be easily replaced once the outer layer is inserted over the inner layer. Further, because of the porous nature of the inner layer, pressurized air could not be used for compressing the same. 
     Other patents are interest are U.S. Pat. Nos. 4,178,664; 4,391,898; 5,216,954; 5,256,459; 5,351,616; 5,352,507; 5,415,612; 5,520,600; 5,544,584; and 5,577,443. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a printing roller having a printing sleeve mounted thereon, and a method for mounting and dismounting sleeves from the printing roller, that overcomes the problems with the aforementioned prior art. 
     It is another object of the present invention to provide a non-expandable printing sleeve mounted on a compressible printing roller. 
     It is still another object of the present invention to mount the sleeve on the printing roller by providing pressurized air between the sleeve and printing roller in order to compress a covering layer of the printing roller. 
     It is yet another object of the present invention to provide a printing roller having a sleeve mounted thereon, and a method for mounting and dismounting sleeves from the printing roller that is easy and economical to use and manufacture. 
     In accordance with an aspect of the present invention, a roller system includes a cylindrical member; a covering layer fixedly mounted on the mandrel, the covering layer being resilient and compressible; a sleeve made of a non-expandable material and removably mounted on the covering layer; and an arrangement for supplying a pressurized gas between the covering layer and the sleeve in order to compress the covering layer and permit mounting of the sleeve on the covering layer and dismounting of the sleeve from the covering layer. 
     Preferably, the cylindrical member is comprised of a cylindrical mandrel with a cylindrical surface having at least one bore extending therethrough; the covering layer includes at least one opening in fluid communication with the at least one bore; and the arrangement for supplying a pressurized gas includes a supply of pressurized gas connected with the at least one bore for supplying the pressurized gas through the at least one bore and out through the at least one opening to a position between at least a portion of the sleeve and the covering layer. 
     The at least one bore is located close to one end of the mandrel. In one embodiment, the at least one opening is formed by a substantially annular cut-away groove in the covering layer. In another embodiment, the at least one opening includes a plurality of interconnected openings in the covering layer. Further, the at least one opening is provided at an angle relative to a direction perpendicular to an axial direction of the mandrel, with the angle being in a range of approximately 30° to 45°. 
     There is further a device connected with the cylindrical member for rotatably holding the cylindrical member. 
     The covering layer is made of a material selected from the group consisting of rubber, urethane and polymers. The material can be a a closed cell foam material or an open cell foam material with a non-porous layer thereover. The sleeve is made of a metal material or a plastic material. 
     In accordance with another aspect of the present invention, a method of mounting a non-compressible sleeve on a resilient and compressible covering layer of a roller and dismounting the sleeve from the covering layer of the roller, includes the steps of supplying a pressurized gas to a position between at least a portion of the sleeve and the covering layer; compressing the resilient and compressible covering layer with the pressurized gas to an outer diameter slightly smaller than an inner diameter of the sleeve; axially moving the sleeve over the compressed covering layer when mounting the sleeve on the covering layer; stopping the supply of the pressurized gas from the position between at least a portion of the sleeve and the covering layer such that the covering layer expands to form an interference fit between the sleeve and the covering layer; and axially moving the sleeve from the compressed covering layer when removing the sleeve from the covering layer after the covering layer has been compressed. 
     The step of supplying pressurized gas to the position between at least a portion of the sleeve and the covering layer, includes the step of supplying the pressurized gas from an interior of the covering layer through at least one opening to a position between at least a portion of the sleeve and the covering layer in order to compress the covering layer and permit mounting of the sleeve on the covering layer and dismounting of the sleeve from the covering layer. 
     Preferably, the covering layer is mounted on a mandrel having at least one bore therein in fluid communication with the at least one opening in the covering layer; and the step of supplying pressurized gas to the position between at least a portion of the sleeve and the covering layer, includes the step of supplying the pressurized gas from an interior of the mandrel through the at least one bore and the at least one opening to a position between at least a portion of the sleeve and the covering layer in order to compress the covering layer and permit mounting of the sleeve on the covering layer and dismounting of the sleeve from the covering layer. 
     In another embodiment, the step of supplying pressurized gas to the position between at least a portion of the sleeve and the covering layer, includes the step of supplying the pressurized gas through an end of the mandrel to the interior of the mandrel from a supply of pressurized gas. 
     The above and other objects, features and advantages of the invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a printing roller according to a first embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of a printing roller according to a second embodiment of the present invention; 
     FIG. 3 is a cross-sectional view, similar to FIG. 1, showing the start of an operation for mounting a sleeve on the printing roller; 
     FIG. 4 is a cross-sectional view, similar to FIG. 1, showing the middle of an operation for mounting a sleeve on the printing roller; and 
     FIG. 5 is a cross-sectional view, similar to FIG. 1, showing the end of an operation for mounting a sleeve on the printing roller. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings in detail, and initially to FIG. 1 thereof, there is shown a printing roller  10  according to a first embodiment of the present invention. Printing roller  10  includes a cylindrical member which is preferably a hollow, cylindrical printing mandrel  12  which is closed at both ends by circular end walls  14  and  16 . Printing roller  10  is rotatably journaled by journal members  18  and  20  secured to end walls  14  and  16 . Alternatively, journal members  18  and  20  can be replaced by a center shaft passing through and secured to end walls  14  and  16 . Mandrel  12  is made of a rigid metal material. 
     End wall  16  is provided with a threaded opening  22  which can threadedly receive an end of a hose (not shown) connected to an air supply  24  (FIGS.  3 - 5 ). 
     A covering layer  26  is fixedly mounted on mandrel  12 , and is made of a resilient, compressible and deformable material, such as rubber, urethane or the like. The material must also having an elastic limit that is higher than the stress induced thereon so as to prevent permanent deformation. Some rubbers are not compressible. In this regard, a preferred material is a compressible foam/hard urethane material having a thickness in the range of 0.1875 inch to 0.25 inch. Preferably, the material of covering layer  26  will compress at least 0.025 inch under a pressure of 60 psi, while also being as hard as possible, having a high wear resistance and a high coefficient of friction. More preferably, the material should compress from a nominal outer diameter of 3 inches ±0.001 inch to an outer diameter of 2.995 inch ±0.001 inch under a pressure of 75 psi or 5 bar. For example, if the outside diameter of rubber covering layer  26  is 2.92 inches, it is desirable that rubber covering layer  26  be capable of compression to about 2.87 inches. As another example, if the outside diameter of rubber covering layer  26  is 3.07 inches, it is desirable that rubber covering layer  26  be capable of compression to about 3.02 inches. 
     In accordance with an important aspect of the present invention, a bore  28  extends through the cylindrical wall of mandrel  12  at one end thereof, preferably at an end thereof which is adjacent end wall  14 , that is, farther away from end wall  16  at which threaded opening  22  is provided. Preferably, bore  28  is located as close to end wall  14  as possible. Bore  28  can have any suitable dimension, which is dependent on the diameter and length of mandrel  12 , but preferably has a diameter of about ⅛ inch. In addition, a cut-away groove  30  extends through rubber covering layer  26  in fluid communication with bore  28 . In this manner, the hollow interior of mandrel  12  is in open, fluid communication with the exterior of roller  10 . Preferably, cut-away groove  30  is formed by an annular cut-away portion of rubber covering layer  26 , and preferably, the cut-away portion is angled in the range of about 30° to 45°, as shown in FIG.  1 . However, cut-away groove  30  can also be provided without the angular range, for example, in line with bore  28 , as shown in the alternative embodiment of FIG.  2 . Cut-away groove  30  can have any suitable dimension, although a preferred width is about 0.25 inches. In like manner, the depth of groove  30  can be any suitable dimension, although a preferred depth is about 0.125 inches. The radial outer portion of cut-away groove  30  must be sufficiently large to allow air to exit through cut-away groove  30 . 
     Alternatively, a plurality of interconnected bores can be provided in place of cut-away groove  30 . 
     A printing sleeve  32 , as shown in FIGS. 3-5, is removably mounted on rubber covering layer  26 . Unlike specialized and expensive printing sleeves according to the prior art, printing sleeve  32  is formed of a non-expandable material, such as an inexpensive aluminum or other metal, plastic or composite sleeve. The inner diameter of printing sleeve  32  is slightly less than the outer diameter of rubber covering layer  26 . For example, if rubber covering layer  26  has an outer-diameter of 2.92 inches, printing sleeve  32  can have an inner diameter of 2.90 inches, with a tolerance of ±0.005 inch, so that the inner diameter of printing sleeve  32  would be in the range of 2.895 inches to 2.905 inches. 
     In order to insert printing sleeve  32  onto rubber covering layer  26 , the latter must be compressed, for example, to an outer diameter of 2.88 inches. In order to accomplish this, printing sleeve  32  is initially force fit over an initial portion of rubber covering layer  26  in the axial direction until printing sleeve  32  covers cut-away groove  30 , as shown in FIG.  4 . Pressurized air from air supply  24  is then supplied to the hollow interior of printing roller  10  through threaded opening  22 . The pressurized air then travels through the hollow interior and exits through radially directed bore  28  and cut-away groove  30 . Because of the elastic nature of rubber covering layer  26  and the inelastic nature of aluminum printing sleeve  32 , rubber covering layer  26  is forced to compress. Preferably, the pressure of the pressurized air is at least 60 psi. This permits sleeve  32  to easily slide over covering layer  26 , as shown in FIGS. 4 and 5. When sleeve  32  is fully slid over covering layer  26 , as shown in FIG. 5, the pressurized air from air supply  24  is stopped, whereupon covering layer  26  expands to its original outer diameter, thereby locking printing sleeve  32  in position. 
     When printing sleeve  32  is changed, it is only necessary to perform the reverse procedure. In such case, pressurized air from air supply  32  is supplied through cut-away groove  30  so as to compress covering layer  26  and thereby permit printing sleeve  32  to be removed in the reverse order from FIG. 5 to FIG. 3, and a new printing sleeve  32  thereafter replaced on covering layer  26 . 
     Thus, with the present invention, an inexpensive aluminum, steel or plastic printing sleeve  32  can be used, thereby greatly reducing the cost of the system. Further, when printing sleeve  32  becomes worn, it is very easy and inexpensive to replace printing sleeve  32 , without any complicated arrangements. 
     It will be appreciated that the present invention can be modified in accordance with the claims herein. Specifically, end walls  14  and  16  and threaded opening  22  can be eliminated, and in such case, a pipe can extend through the open ends of the mandrel and be connected directly with bore  28 . 
     Although the present invention has been discussed in relation to printing rollers, it has wider applicability and applies to rollers in general. 
     Having described specific preferred embodiments of the invention with reference to the accompanying drawings, it will be appreciated that the present invention is not limited to those precise embodiments and that various changes and modifications can be effected therein by one of ordinary skill in the art without departing from the scope or spirit of the invention as defined by the appended claims.