Abstract:
An object of the present invention is to provide a sealed rolling bearing, where sealing plate fitting spaces are reduced to virtually zero, thereby allowing parts compatibility with non-sealed rolling bearings due to its bearing size and also enabling the color of lubricant to be visually observed from the outside. The sealed rolling bearing includes a rolling bearing main body; and sealing members each provided between outside edges of an inner ring track and an outer ring track in the rolling bearing main body. The sealing members are provided by transparent plastic sealing plates and attached to a retainer.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a sealed rolling bearing capable of preventing entry of foreign matters. 
       BACKGROUND ART 
       [0002]    Sealed rolling bearings typically have the following structure: An inner ring and an outer ring are opposed to each other in an in-out relationship, with rolling elements placed therebetween; sealing plates are press-fitted on both sides of a track in one of these track rings; and the other track ring has both sides of its track contacted or nearly contacted by free ends of the sealing plates (Patent Literature 1). The sealing plates prevent foreign matters from making entry into the bearing while also preventing lubricant from leaking out of the bearing. 
         [0003]    Sealing plates having their free ends designed to make contact with the faced track ring are provided by rubber seals which have a backing metal therein. Non-contact sealing plates are provided by metal plates. 
         [0004]    In whichever of the types, fitting spaces must be provided on both sides of the tracks in the inner and outer rings, and therefore the inner and the outer rings must have increased widths accordingly. Consequently the size of the bearing is greater than normal non-sealing type rolling bearings (Patent Literature 2). This poses such problems that sealed rolling bearing parts are not compatible with those in non-sealed rolling bearings, and that sealed rolling bearing are heavier. 
         [0005]    In order to reduce the sealing plate fitting spaces, the sealing plates are screwed to the retainer in some rolling bearings (Patent Literature 3). The invention which relates to these rolling bearings was made under an object to eliminate deformation risks of the sealing plates or the inner/outer ring(s) when the sealing plate are fitted onto the inner-diameter surface of the outer ring or the outer-diameter surface of the inner ring. To accomplish this, the sealing plates are screwed to the bearing retainer so that the sealing plates have their inner and outer circumferential edges contacting or nearly contacting the outer ring&#39;s inner-diameter surface and the inner ring&#39;s outer diameter surface. 
         [0006]    Sealed rolling bearings require periodical inspection and lubricant replacement since the lubricant which is sealed inside the bearing is subject to deterioration with time. A simple method of determining the extent of lubricant deterioration is to make visual observation of the color of lubricant and compare the color with reference colors. 
         [0007]    However, this is not possible in the sealed rolling bearing disclosed in Patent Literature 3 and other conventional sealed rolling bearings since their sealing plates are made of non-transparent material such as metal or rubber and it is impossible to visually observe the color of lubricant from outside the bearing. Therefore, these bearings have a problem that they must be removed and then disassembled each time a visual observation is to be made to the color of lubricant in order to determine the extent of lubricant deterioration. 
       Citation List 
     Patent Literature 
       [0008]    Patent Literature 1: JP-Y-H7-12736 
         [0009]    Patent Literature 2: JP-A-H9-317760 
         [0010]    Patent Literature 3: JP-A 2007-198540 (see  FIG. 1  and  FIG. 5 ) 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0011]    It is therefore an object of the present invention to provide a sealed rolling bearing, where sealing plate fitting spaces are reduced to virtually zero, thereby allowing parts compatibility with non-sealed rolling bearings due to its bearing size and also enabling the color of lubricant to be visually observed from the outside. 
       Solution to Problem 
       [0012]    In order to achieve the object mentioned above, the present invention provides a sealed rolling bearing which includes a rolling bearing main body comprised of an inner ring, an outer ring, a large number of rolling elements placed between a track in the inner ring and a track in the outer ring, and a retainer for the rolling elements; and sealing members each provided between outside edges of the inner ring track and the outer ring track in the rolling bearing main body. With this arrangement, the sealing members are provided by transparent plastic sealing plates and are attached to the retainer. 
         [0013]    The sealing plate may have a region provided with a reference-color decal as a guide for determining the extent of lubricant deterioration. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0014]    According to the present invention, the sealing plates are attached to the retainer. This reduces sealing plate fitting spaces to virtually zero on both sides of the inner and outer ring track grooves, enabling to make the size of bearing identical with the size of non-sealed rolling bearings, and therefore to make the bearings parts-compatible with each other. At the same time, it is now possible to visually observe the color of lubricant from outside since lubricant on the inner side of the sealing plate is visible. This provides an advantage that the extent of lubricant deterioration can be determined quickly. 
         [0015]    Further, the sealing plate is provided by a transparent plate of a synthetic resin. This provides an advantage that it is lighter in weight and lower in cost than those made of rubber or metal. 
         [0016]    It should be noted here that a reference-color decal may be bonded to a part of the sealing plate. This allows the above-mentioned determination process to be performed more quickly. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a sectional view showing part of an embodiment. 
           [0018]      FIG. 2A  is a sectional view showing part of a sealing plate in the embodiment whereas  FIG. 2B  is a front view showing part of the sealing plate. 
           [0019]      FIG. 3  is a perspective view showing part of the embodiment. 
           [0020]      FIG. 4  is a sectional view showing part of an uncased state in the embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]    Hereinafter, an embodiment of the present invention will be described based on the attached drawings.  FIG. 1  shows a self-aligning roller bearing. This bearing includes a bearing main body comprised of an inner ring  11  and an outer ring  12  disposed coaxially in an in-out relationship; a large number of rollers  13  disposed in two rows between the inner and the outer track rings; and a retainer  14  which holds/guides the rollers  13  equidistantly in a circumferential direction. 
         [0022]    The bearing main body and a pair of transparent sealing plates  15  attached to a left side and a right side of the inner and the outer rings  11 ,  12  constitute a sealed self-aligning roller bearing. 
         [0023]    Without the sealing plates  15 , the bearing main body has the same size as a non-sealed self-aligning roller bearing, i.e., a type of self-aligning roller bearing that does not make use of sealing plates. 
         [0024]    The outer ring  12  has its inner-diameter surface formed with an outer ring track  16  provided by a concave sphere which has its center at the center of the bearing. The inner ring  11  has its outer diameter surface formed with inner ring tracks  17 ,  17 , provided by two rows of concave spheres opposed to the outer ring track  16 . Between the two inner ring tracks  17 ,  17  and being sandwiched by two inner circumferential edges of the tracks, a flat region  18  is formed as a narrow ridge following the curves of the spherical surfaces of the inner ring tracks  17 ,  17 . 
         [0025]    The rollers  13  are barrel-shaped, each having a spherical surface and being placed between the inner ring track  17  and the outer ring track  16 . 
         [0026]    The retainer  14  is a cage type retainer made by punching a steel plate, formed with two rows of retainers which are symmetrical to each other in the left-right direction as shown in  FIG. 1  and  FIG. 3 , i.e., a left-side retainer  14   a  disposed on an outside surface of the left-side inner ring track  17  and a right-side retainer  14   b  disposed on an outside surface of the right-side inner ring track  17 . Each of the retainers  14   a ,  14   b  includes an inside ring  21  and an outside ring  22  opposed axially to each other, and beams  23  connecting these rings axially with each other. A large number of the beams  23  are provided at a predetermined circumferential interval. Spaces between two adjacent beams  23  are rectangular pockets  24 . Each pocket  24  holds and supports one of the rollers  13 . 
         [0027]    The outside ring  22  has its inner circumferential surface contacted by the inner ring track  17  (see  FIG. 1 ). Due to this contact, the retainer  14  is guided by the inner ring  11  and is classified as an inner-ring-guided type. 
         [0028]    As the outside ring  22  makes contact with the inner ring track  17 , the outside ring  22  closes approximately a half of a gap space between the inner and the outer rings  11 ,  12 . Therefore, the bearing will be completely sealed if the remaining uncovered half, or slightly less, is closed by the sealing plates  15 . 
         [0029]    The sealing plates  15  according to the embodiment are provided by annular, transparent plates made of a synthetic resin such as PET. Each plate has a closing zone “a” (see  FIG. 2 ) formed along its outer circumferential edge for closing the above-described opening; an adhering zone “b” formed on the radially inner side thereof to oppose to the outside ring  22 ; and a reinforcing zone “c” formed on the radially inner side of the adhering zone b. The reinforcing zone “c” increases strength of the sealing plate  15  by its width, while increasing ease of handling as well. 
         [0030]    The sealing plate  15  is attached by bonding the adhering zone “b” onto an outer side surface of the outside ring  22 . The closing zone “a” is positioned so that its outer circumferential edge is non-contacting with the outer ring track  16 , with a very slight gap which is narrow enough not to cause loss of sealing. 
         [0031]    It should be noted here that although the closing zone “a” is principally, non-contact (gapped) as described above, a contact type configuration may be used in cases where increased level of dust-proofing and sealing performances are required. 
         [0032]    Self-aligning roller bearings are sometimes “uncased” as shown in  FIG. 4 , by dislocating the outer ring  12  from the inner assembly which is composed of the inner ring  11 , the rollers  13  and the retainer  14 , in mutually opposite directions so as to expose the rollers  13  for a purpose of inspecting the interior of the bearing for example. 
         [0033]    It is impossible to uncase if the bearing is in a state as shown in  FIG. 1  where the sealing plates  15  have their outer circumferential edges located on an imaginary arc line (see alternate long and short dash lines in  FIG. 1 ) extended from an arc defined by the outer ring track  16 , or located on the outer side which is closer to the outer ring  12 , in a sectional plane that contains the axis of the outer ring  12 . In these states, the sealing plates  15  will interfere with the outer ring  12  if uncasing is attempted. 
         [0034]    The interference is avoided, however, and it becomes possible to uncase if there is provided a predetermined gap “a” as shown in  FIG. 4 , on the inner, axis side of the extended arc line (see alternate long and short dash lines in  FIG. 4 ) from the arc defined by the outer ring track  16  in the sectional plane that contains the axis of the outer ring  12 . By setting the gap “a” to a minimum value at which the sealing is not yet lost, it is possible to maintain the sealing intact. 
         [0035]    As shown in  FIG. 2B , the sealing plate  15  has its outer surface provided with reference-color decals  25  along the closing zone “a”, over an area corresponding to the adhering zone “b” or an area corresponding to both the adhering zone “b” and the reinforcing zone “c”. Each reference-color decal  25  has a symbol such as A, B, C to indicate the extent of lubricant deterioration determined from the color of the lubricant. For reference,  FIG. 1  also shows a lubricant application hole  26 . 
         [0036]    The above is a sealed self-aligning roller bearing as an embodiment. This bearing can be used exactly in conventional manners, allowing relative alignment between the axis on the side of the inner ring  11  and a housing on the side of the outer ring  12  with respect to the bearing center. Foreign matter entry from outside is prevented by the sealing plate  15  and the outside ring  22  of the retainer  14 . They also prevent lubricant leakage. 
         [0037]    During operation, lubricant fills the entire space inside the bearing, and therefore part of the lubricant makes contact with an inner surface of the closing zone “a” of the sealing plate  15 . When determining the extent of lubricant deterioration, the lubricant inside the bearing is visually observable from outside, through the closing zone “a”. Then, observed color of the lubricant can be compared to colors in the reference-color decals  25  for difference in color, to determine the extent of lubricant deterioration. 
         [0038]    It should be noted here that although the above embodiment covers only a self-aligning roller bearing, the present invention is applicable to rolling bearings in general, including non-self-aligning roller bearings, ball bearings, and other bearings. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           11  inner ring 
           12  outer ring 
           13  roller 
           14  retainer 
           14   a  left retainer 
           14   b  right retainer 
           15  sealing plate 
           16  outer ring track 
           17  inner ring track 
           18  flat region 
           21  inside ring 
           22  outside ring 
           23  beam 
           24  pocket 
           25  reference-color decal 
           26  application hole