Abstract:
This invention improves a rolling bearing fitted to a shaft supporting section of a roller to realize an oscillation roller. A rolling bearing to be fitted to one of the shaft supporting sections of a roller comprises a collared inner ring and a collared outer ring and a plurality of cylindrical rolls arranged between the inner ring and the outer ring as rolling members and the transversal distance of the surface of the inner ring and/or that of the surface of the outer ring facing the raceway surfaces of the cylindrical rolls is made greater than the axial length of the cylindrical rolls to make the inner ring and/or the outer ring, whichever appropriate, of the rolling bearing axially movable so as to allow the roller to oscillate. As the roller moves axially, the inner ring, the outer ring or the cylindrical rolls moves axially.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2006-117032, filed Apr. 20, 2006; and No. 2006-226902, filed Aug. 23, 2006, the entire contents of both of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to a rolling bearing of an oscillation roller and an oscillation method of a roller. More particularly, the present invention relates to a rolling bearing to be mounted in a oscillation roller that can be used as form rubber roller and dampening rubber roller used in a printing machine.  
         [0004]     2. Description of the Related Art  
         [0005]     Rollers are being widely used as rotary members in various fields of industry. In certain occasions, rollers that are used as rotary members are required to axially oscillate as they revolve. Rollers having such a functional feature are generally referred to as oscillation rollers.  
         [0006]     While oscillation rollers are being widely used in various fields of industry, typical applications of oscillation rollers include form rubber rollers and dampening rollers of printing machines.  
         [0007]      FIG. 18  of the accompanying drawings schematically illustrates the part of a form rubber roller, which is the most downstream roller of the forming part of a printing machine, for applying ink to printing plates. In  FIG. 18 , reference numeral  1  denotes a plate cylinder. A total of four printing plates  2  are mounted on a plate cylinder  1  to surround the latter and arranged at predetermined intervals. In  FIG. 18 , reference numerals  3 ,  3  respectively denote the most downstream form rubber rollers. In  FIG. 18 , reference numeral  4  is an ink distributing roller. A transfer roller that is linked to an ink supply unit and other appropriate rollers are arranged upstream relative to the form rubber rollers  3 ,  3  and held in contact.  
         [0008]     In the above-described printing machine, the form rubber rollers  3 ,  3  are held in contact with the printing plates  2 ,  2 , . . . mounted around the plate cylinder  1  so as to be driven to rotate. Then, as a result, the ink supplied from the ink supply unit is made to transfer to the printing plates  2 ,  2 , . . . around the plate cylinder.  
         [0009]     A form rubber roller  3  that is being used in a printing machine is held in contact with the ink distributing roller  4  that transversally (axially) reciprocates and axially reciprocates along with the ink distributing roller  4 . Such a roller is referred to as oscillation roller. By using an oscillation roller as a form roller, it is possible to cause the form roller to oscillate, following the ink distributing roller that transversally reciprocates. Then, as a result, the ink on the peripheral surface of the form roller is dispersed and transfer uniformly to the printing plates  2  mounted to the plate cylinder  1  to surround the latter.  
         [0010]     Since the form rollers  3 ,  3  are liable to be damaged by the edges of the plate cylinder  1 , the form rubber rollers  3 ,  3  are driven to transversally oscillate in order to avoid such damages. Additionally, the form rollers  3 ,  3  can give rise to frictional areas that are annular in the direction of revolutions at positions corresponding to the edges of the printing plates  2  and consequently deficiency of ink transferability and unevenness of ink density can arise at the corresponding positions in the subsequent printing process. It is necessary for the form rubber rollers to transversally oscillate in order to avoid such problems.  
         [0011]     Ghosts may appear when printing an image where color densities can abruptly change in the transversal direction. As a general practice, the metal made rollers that are held in contact with the form rubber rollers are driven to axially reciprocate in order to avoid such ghosts.  
         [0012]     Known oscillation rollers include the one disclosed in Jpn. Pat. Appln. Publication No. 60-101049. The disclosed oscillation roller has a roller shaft arranged at the inside of a roller coat member and held in position so as not to be able to revolve. The roller coat member of the form rubber roller that oscillates transversally is borne on the roller shaft so as to be able to revolve and axially movable. Additionally the axial stroke of the roller coat member is limited by two bushes  22 ,  24  at the opposite sides and pressure springs  26  are arranged at the respective lateral sides of the roller between the two bushes. However, known oscillation rollers are complex in terms of configuration and are accompanied by the problem of a high manufacturing cost. Thus, there is a strong demand for oscillation rollers that are structurally simple and can be provided at a low manufacturing cost.  
       BRIEF SUMMARY OF THE INVENTION  
       [0013]     In view of the above-identified circumstances, it is therefore an object of the present invention to provide a rolling bearing that has a simple structure and allows a roller to oscillate axially.  
         [0014]     According to the present invention, the above object is achieved by providing a rolling bearing comprising a plurality of cylindrical rolls as rolling members between an inner ring and an outer ring thereof. The transversal distance of the surface of either or the surfaces of both of the inner ring and the outer ring vis-à-vis the raceway surfaces of the cylindrical rolls vis-à-vis is made longer than the axial length of the cylindrical rolls. With this arrangement, either or both of the inner ring and the outer ring of the rolling bearing can axially move.  
         [0015]     The roller can oscillate axially once a rolling bearing according to the invention is fitted to either or both of a pair of shaft supporting sections of the roller. Another rolling bearing can be fitted to the other shaft supporting section of the roller located at the opposite side relative to the former shaft supporting section. When the inner ring or the outer ring of the former rolling bearing is moved axially and the roller is driven to move axially, the inner ring or the outer ring, whichever appropriate, of the latter rolling bearing follows the axial movement of the roller.  
         [0016]     In another aspect of the present invention, there is provided an oscillation method of a roller according to which a rolling bearing is fitted to one of a pair of shaft supporting sections of a roller. Then, as a result, the inner ring or the outer ring of the rolling bearing becomes axially movable. Another similar rolling bearing is fitted to the other shaft supporting section of the roller located at the opposite side relative to the former shaft supporting section that that the roller may axially oscillate.  
         [0017]     Thus, according to the present invention, it is possible to turn a conventional fixed roller that does not oscillate into an oscillation roller simply by remodeling the rolling bearings fitted to the respective shaft supporting sections. The remodeling of the rolling bearings consists in reforming the rolling bearings, in each of which a plurality of cylindrical rolls are arranged as rolling members between the inner ring and outer ring thereof. The reforming by turn consists in making either or both of the inner ring or the outer ring of each of the rolling bearings axially movable. Thus, the bearings can be reformed in a simple manner to turn the roller into an oscillation roller at low cost.  
         [0018]     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0019]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0020]      FIG. 1  is a schematic lateral view of an oscillation roller mounted with an embodiment of rolling bearings of the present invention at the bearing supporting section thereof;  
         [0021]      FIG. 2  is a partly cut out schematic perspective view of an embodiment of rolling bearing of the present invention;  
         [0022]      FIG. 3  is a partly cut out schematic perspective view of another embodiment of rolling bearing of the present invention;  
         [0023]      FIG. 4  is a schematic exemplary illustration of the relationship between the raceway rings (inner ring and outer ring) and the rolling members of an embodiment of rolling bearing of the present invention;  
         [0024]      FIG. 5  is a schematic exemplary illustration of the relationship between the raceway rings (inner ring and outer ring) and the rolling bearings of a conventional rolling bearing;  
         [0025]      FIG. 6  is a schematic perspective view of the inner ring of still another embodiment of rolling bearing of the present invention;  
         [0026]      FIG. 7  is a schematic illustration of an oscillation roller mounted with rolling bearings according to the present invention and adapted to be oscillated by a reciprocal movement of a swing roller held in contact with the oscillation roller;  
         [0027]      FIG. 8  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0028]      FIG. 9  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0029]      FIG. 10  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0030]      FIG. 11  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0031]      FIG. 12  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0032]      FIG. 13  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0033]      FIG. 14  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0034]      FIG. 15  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0035]      FIG. 16  is a partly cut out schematic perspective view of still another embodiment of rolling bearing of the present invention;  
         [0036]     FIGS.  17 A 1  through  17 C 1  are schematic illustrations of the relationship between the oscillation of an oscillation roller formed by using still another embodiment of rolling bearing of the present invention and the sliding motion of the inner ring of the rolling bearing;  
         [0037]      FIG. 18  is a schematic illustration of the relationship between the form rubber roller for applying ink to the plate cylinder and the swing roller of a known printing machine;  
         [0038]      FIG. 19  is a photograph of the form rubber roller that is an oscillation roller of an embodiment of the present invention, showing the surface condition thereof after six month of use; and  
         [0039]      FIG. 20  is a photograph of a form rubber roller that does not oscillate, showing the surface condition thereof after a week of use. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]      FIG. 1  is a schematic lateral view of an oscillation roller mounted with rolling bearings according to an embodiment of the present invention. Referring to  FIG. 1 , reference numeral  10  denotes a roller main body and reference numeral  11  denotes a rolling bearing fitted to a shaft supporting section of the roller main body.  FIG. 2  is a partly cut out schematic perspective view of one of the rolling bearings  11 . In  FIG. 2 , reference numeral  11  denotes a rolling bearing, reference numeral  12  denotes an outer ring, while reference numeral  13  denotes an inner ring and reference numeral  14  denotes a cylindrical roll that is a rolling member. In  FIG. 2 , reference numeral  15  denotes a cage of cylindrical rolls  14 .  
         [0041]     In the rolling bearing  11 , either the outer ring  12  or the inner ring  13  is made longer than the axial length of the cylindrical rolls  14 . In  FIG. 2 , the transversal distance of the surface of the inner ring  13  that is faced the raceway surfaces of the cylindrical roll  14  as viewed in the axial direction is made longer than the axial length of the cylindrical rolls  14 .  
         [0042]     In the instance of  FIG. 2 , the inner ring  13  shows a U-shaped cross section (to form an angular groove or channel) to produce a dent  16 . The transversal distance of the dent  16 , or the width of the surface facing the raceway surfaces of the cylindrical rolls, is made greater than the axial length of the cylindrical rolls  14 .  FIG. 3  shows an arrangement where cylindrical rolls are arranged in two rows.  
         [0043]      FIG. 4  is an enlarged schematic cross-sectional view of the bearing of  FIG. 2  taken along line A-A and viewed in the direction of the arrows. The outer width of the inner ring  13  is same as the outer width of the outer ring  12  in  FIG. 4 . However, the outer width of the inner ring may be made greater to increase the width of the dent  16  and also the thickness and hence the strength of the lateral walls of the U-shaped part of the inner ring.  
         [0044]      FIG. 5  is a view of a known rolling bearing shown for the purpose of comparison. In both  FIGS. 4 and 5 , reference numeral  12  denotes an outer ring and reference numeral  13  denotes an inner ring, while reference numeral  14  denotes a cylindrical roll.  
         [0045]     It will be clear from  FIGS. 2 and 4  that, since the transversal distance of the wide dent  16  is greater than the axial length of the cylindrical rolls  14 , the inner ring  13  can move transversally by the difference between the transversal distance of the dent  16  and the axial length of the cylindrical rolls  14 .  
         [0046]     It will be appreciated that, if the transversal length of the dent of inner ring and that of the outer ring are the same as the axial length of the cylindrical rolls in the strict sense of the word, there is no clearance between the inner and outer rings and the cylindrical rolls so that the rolling bearing cannot revolve at all. Therefore, the transversal length of the dent of the inner ring and that of the outer ring are made slightly greater than the axial length of the cylindrical rolls in ordinary rolling bearings in order to provide an appropriate clearance.  
         [0047]     However, the transversal length of the dent of the inner ring  13  is made greater than the axial length of the cylindrical rolls  14  beyond the ordinary range of clearance according to the present invention. With this arrangement, the inner ring or the outer ring can move and hence the roller equipped with this bearing can move axially.  
         [0048]     According to the present invention, the difference between the transversal distance of the dent of the inner or outer ring and the axial length of the cylindrical rolls  14  is between 2 mm and 20 mm, preferably between 3 mm and 5 mm. In terms of ratio, the axial length of the cylindrical rolls is preferably between 50% and 85% of the transversal distance of the dent of the inner or outer ring. While the inner ring  13  is integrally formed with one or two collars in  FIGS. 2 and 3 , the collar  18  is preferably separable from the inner ring  13  as shown in  FIG. 5 .  
         [0049]     The transversal length of the surface of the inner ring  13  that faces the raceway surfaces of the cylindrical rolls  14  is greater than the axial length of the cylindrical rolls  14  in the description given above by referring to  FIG. 4 . However, the above description relating to the inner ring  13  may be switched to the outer ring  12 . More specifically, although not shown, the transversal length of the surface of the dent  17  arranged at the inside of the outer ring  12 , or the transversal length of the surface of the outer ring  12  that faces the raceway surfaces of the cylindrical rolls  14  is made greater than the axial length of the cylindrical rolls  14 . With this alternative arrangement, the outer ring  12  can move transversally by the difference between the transversal distance of the broadened dent and the axial length of the cylindrical rolls  14 .  
         [0050]      FIG. 7  is a schematic illustration of an oscillation roller mounted with rolling bearings at the shaft supporting sections at the opposite ends of the roller and adapted to be oscillated by a swing roller held in contact with the oscillation roller. In  FIG. 7 , reference numeral  20  denotes an oscillation roller and reference numeral  21  denotes a rolling bearing, while reference numeral  22  denotes a swing roller. The swing roller  22  is driven to revolve by a mechanism not shown and adapted to axially swing by means of a cam mechanism  23 . The oscillation roller  20  is held in contact with the swing roller  22  so that it swings transversally as it revolves due to the friction with the swing roller  22 .  
         [0051]     The oscillation roller  20  of  FIG. 7  is mounted with rolling bearings  21  that are the same and identical respectively at the shaft supporting sections at the opposite ends of the roller. However, the present invention is by no means limited thereto and, alternatively, the oscillation roller  20  may be mounted with a rolling bearing at one of the shaft supporting sections at the opposite ends of the roller and with a different rolling bearing at the other shaft supporting section as shown in  FIGS. 8 through 16 . In  FIGS. 8 through 16 , the components same as those illustrated in  FIG. 2  are denoted respectively by the same reference numerals.  
         [0052]     The rolling bearing shown in  FIG. 8  is substantially same as the one illustrated in  FIG. 2  and the inner ring  13  is not provided with any collar. With this arrangement, the inner ring  13  moves axially. The rolling bearing shown in  FIG. 9  is substantially same as the one illustrated in  FIG. 8  but the inner ring  13  is provided with a collar at one of the opposite edges thereof. With this arrangement, the inner ring  13  moves axially in one of the opposite directions (in the direction of the collar).  
         [0053]     The rolling bearing shown in  FIG. 10  is provided at the inner ring  13  thereof with a collar and a collar ring  30  is fitted to the opposite edge by way of a spacer  13 S having a diameter substantially same as that of the inner ring. With this arrangement, the inner ring  13  can move axially in one of the opposite directions (in the direction of the collar) with the spacer  13 S.  
         [0054]     The rolling bearing shown in  FIG. 11  substantially same as that of  FIG. 9  and is provided at the inner ring  13  thereof with a collar and an L-shaped collar ring  30  is fitted to the opposite edge by way of a spacer  13 S having a diameter substantially same as that of the inner ring. With this arrangement, the inner ring  13  can move axially in one of the opposite directions (in the direction of the collar) with the spacer  13 S.  
         [0055]     The rolling bearing shown in  FIG. 12  is substantially same as that of  FIG. 8  and the outer ring  12  thereof is not provided with any collar and can move axially. The rolling bearing shown in  FIG. 13  is substantially same as that of  FIG. 9  but the inner ring  13  is provided with a pair of collars and the outer ring  12  is provided with a collar so that the outer ring  12  can move axially in one of the opposite directions.  
         [0056]     The rolling bearing shown in  FIG. 14  is provided with cylindrical rolls  33 ,  34  that are arranged in two rows and outer ring  40  is the provided with a pair of collars, while the inner ring  41  is not provided with any collar so that it can move axially.  
         [0057]     The rolling bearing shown in  FIG. 15  is substantially same as that of  FIG. 14  where cylindrical rolls  33 ,  34  are arranged in two rows and the outer ring  40  is not provided with any collar but the inner ring  41  is provided with a pair of collars at the opposite edges respectively. With this arrangement, the outer ring  12  can move axially. The rolling bearing shown in  FIG. 16  is a solid type needle-shaped roll bearing and does not have any inner ring but the outer ring  12  thereof is provided with a pair of collars. With this arrangement, the shaft supporting sections of the roller is directly received by cylindrical rolls of this type.  
         [0058]      FIGS. 17A through 17C  are schematic illustrations of the relationship between the oscillation of a roller and the sliding motion of the inner ring of the rolling bearing.  FIG. 17A   1  shows the oscillation roller  20  located at the center and hence it is revolving without swinging transversally. In this situation, the inner ring  13  of the rolling bearing fitted to a shaft supporting section of the oscillation roller  20  is located at the center relative to the cylindrical rolls  14  thereof as shown in  FIG. 17A   1 . Equal transversal gaps  17   a ,  17   b  are formed between the lateral walls of the dent  16  of the inner ring  13  and the cylindrical rolls  
         [0059]     As the swing roller  22  of  FIG. 7  swings transversally, the oscillation roller  20  that is held in contact with the swing roller  22  and revolving swings in the direction of the arrow (leftward) as shown in  FIG. 17B   1 . Under this condition, the inner ring  13  of the rolling bearing moves in the direction of the arrow (leftward) with respect to the cylindrical rolls  14  as shown in  FIG. 17B   1 . Then, as a result, the oscillation roller smoothly moves transversally.  
         [0060]     As the swing roller  22  swings transversally in the opposite direction (rightward), the oscillation roller  20  that is held in contact with the swing roller  22  and revolving swings in the direction opposite to the direction of the arrow (rightward) as shown in  FIG. 17C   1 . Under this condition, the inner ring  13  of the rolling bearing moves in the direction opposite to the direction of the arrow (rightward) with respect to the cylindrical rolls  14  as shown in  FIG. 17C   1 . Then, as a result, the oscillation roller  20  smoothly moves in the direction of the arrow, following the transversal swinging movement of the swing roller  22 .  
         [0061]     While the outer ring is fixed and the inner ring is moved in the above description, conversely the inner ring may be fixed and the outer ring may be moved. Then, the oscillation roller can be made to oscillate, following the transversal swinging motion of the swing roller.  
         [0062]     A rolling bearing  21  as described above is fitted to each or either one of the shaft supporting sections of an oscillation roller  20 . When a rolling bearing  21  is fitted to either one of the shaft supporting sections of an oscillation roller  20 , a different rolling bearing having an outer ring or an inner ring that moves over a long range as shown in any of  FIGS. 8 through 16  is fitted to the other shaft supporting section. With this arrangement, the roller oscillates within the range of the dent  16  of the bearing  21 .  
         [0063]     An oscillation roller according to the present invention can suitably be used as the form roller of a printing machine. An oscillation roller according to the present invention can also find other applications and the scope of application of an oscillation roller is not particularly limited. An oscillation roller according to the present invention has a structure that is remarkably simple if compared with conventional oscillation rollers using a compression spring.  
       EXAMPLE 1  
       [0064]     A pair of JIS B1513 NUP type rolling bearings having cylindrical rolls arranged in a single row, an outer ring that is provided with a pair of collars and an inner ring that is provided with a collar and a collar ring was brought in. The rolling bearings had the following dimensions—the outer diameter: 72 mm, the inner diameter: 30 mm and the width: 19 mm. Each of the rolling bearings was worked in such a way that the transversal distance of the surface of the inner ring facing cylindrical rolls became longer than the axial length of the cylindrical rolls by 4 mm. As a result, a pair of rolling bearings whose inner rings can move axially were prepared.  
         [0065]     The rolling bearings were then respectively fitted to the supporting sections at the opposite sides of a form rubber roller  3  for transferring ink of a printing machine as shown in  FIG. 18 . As a result, the form roller was made capable of oscillating axially. The form roller was made to transfer ink to the printing plates mounted on a plate cylinder and arranged at regular intervals.  
         [0066]     The form roller is adapted to oscillate axially by way of a swing roller  22  (metal roller) as shown in  FIG. 7 . The swing roller  22  is driven to make 90 round trips/min to 130 round trips/min (maximum) with a swinging width of 30 mm.  
         [0067]     The oscillation roller had a core diameter of 110 mm×an outer diameter of 130 and a surface length of 1,620 mm. It was driven to revolve at a rate of 2,600 revolutions/min. The nip width was made to be equal to 7 mm. The rubber was nitrile rubber (NBR) with a hardness of 30.  
         [0068]     The printing machine was operated for printing continuously for six months, 10 hours/day. No abrasion was observed on the surface of the form rubber roller at the position corresponding to the edges of the printing plate.  FIG. 19  is a photograph of the surface of the form rubber roller where the edges of the printing plate hit.  
       Comparative Example  
       [0069]     A pair of non-separable type JIS deep groove ball bearings having cylindrical rolls arranged in a single row was brought in as rolling bearings. The rolling bearings had the following dimensions—the outer diameter: 72 mm, the inner diameter: 30 mm and the width: 19 mm. The rolling bearings were then respectively fitted to the supporting sections at the opposite sides of a form rubber roller  3  for transferring ink of a printing machine as shown in  FIG. 18 . The deep groove ball bearings were of the standard type where neither the inner ring nor the outer ring oscillates for its structure. The form rubber roller was used to transfer ink as in Example. The dimensions, the number of revolutions per minute, the nip width, the rubber and the hardness of the rubber were same as those of Example 1 mentioned above.  
         [0070]     The printing machine was operated for printing continuously for a week (seven days), 10 hours/day and the surface of the form rubber roller was observed. Abrasion was clearly observed on the surface of the form rubber roller at the position corresponding to the edges of the printing plate.  FIG. 20  is a photograph of the surface of the form rubber roller where the edges of the printing plate hit. As seen from  FIG. 20 , a belt shaped abraded area was observed at upper and lower parts of the central area.  
         [0071]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.