Abstract:
Disclosed is a guide roller wherein bearings are held in a housing, and liquid mixed with abrasive grains is prevented from entering the interior of the housing through a small hole, thereby improving service life. The guide roller is configured to comprise a housing wherein the bearings are held in the housing, and the housing has a shaft hole wherein a support shaft is inserted that is installed upon the bearings. The shaft hole is formed to have a tapered wall, and the diameter of the hole decreases continuously toward the interior of the housing.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a guide roller including a bearing received within a housing, and in particular to a guide roller suitable for applying a tension to a wire of a wire saw. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventionally, the wire saw is known as a means for cutting a work made of hard and brittle material (such as a silicon ingot and a glass article). See patent document 1. A work can be cut or grooved by applying a running wire passed around a pulley unit under an appropriate tension to the work while feeding cutting fluid containing an abrasive to the part to be cut. The cutting fluid may not contain an abrasive if the wire saw is embedded with an abrasive. 
       PRIOR ART DOCUMENT(S) 
       [0003]    Patent document 1: JP 2008-068332A 
       BRIEF SUMMARY OF THE INVENTION 
     Task to be Accomplished by the Invention 
       [0004]    In a conventional wire saw, the cutting fluid mixed with an abrasive (which is intentionally added to the cutting fluid or dislodged from the wire) may seep or otherwise intrude into the housing of the guide roller containing a bearing, and the resulting reduction in the life of the bearing causes an increase in the running cost of the wire saw. 
         [0005]    The present invention was made in view of such a problem of the prior art, and has a primary object to provide a guide roller that can prevent the intrusion of cutting fluid mixed with an abrasive into the housing thereof containing a bearing, and thereby improve the service life of the bearing. 
       Means to Achieve the Task 
       [0006]    To achieve such an object, according to a first aspect of the present invention, the present invention provides a guide roller, comprising: a bearing ( 2 ,  3 ), and a housing ( 4 ) containing the bearing therein and provided with a shaft hole ( 50 ) for receiving a support shaft ( 6 ) to be supported by the bearing; wherein the shaft hole is defined by a tapered wall surface that progressively decreases in diameter toward inside the housing. 
         [0007]    According to a second aspect of the present invention, the support shaft is provided with an annular projection ( 65 ,  66 ) extending circumferentially along an outer surface thereof and projecting toward the tapered wall. 
         [0008]    According to a third aspect of the present invention, the guide roller further comprises a cover member ( 71 ) attached to the support shaft and overlies the shaft hole as seen in an axial direction. 
         [0009]    According to a fourth aspect of the present invention, the housing is provided with an annular stepped portion ( 17 ,  18 ) along an outer circumference thereof, and the annular stepped portion is provided with a tapered outer circumferential surface ( 17   b,    18   b ) that progressively increases in diameter axially toward outside the housing. 
         [0010]    According to a fifth aspect of the present invention, the housing is provided with an annular protrusion ( 91 ) surrounding an opening of the shaft hole and protruding in a direction opposite to that for introducing the support shaft into the housing. 
         [0011]    According to a sixth aspect of the present invention, the annular protrusion is provided with a tapered inner circumferential surface ( 91   b ) that progressively increases in diameter axially toward outside the housing. 
       Effect of the Invention 
       [0012]    According to the first aspect of the present invention, the fluid mixed with an abrasive that is about to intrude into the housing from the shaft hole is guide to the exterior of the housing along the tapered wall surface of the shaft hole by the centrifugal force created by the rotation of the housing. Therefore, the intrusion of fluid mixed with an abrasive into the housing from the shaft hole can be prevented, and the service life of the bearing is maximized. 
         [0013]    According to the second aspect of the present invention, the fluid mixed with an abrasive that is about to intrude into the housing along the outer circumferential surface of the support shaft is initially guided onto the tapered wall surface of the shaft hole by the annular projection and thence to the exterior of the housing via the tapered wall surface. Therefore, the intrusion of fluid mixed with an abrasive into the housing can be effectively prevented. 
         [0014]    According to the third aspect of the present invention, by covering the shaft hole with the cover member, the intrusion of fluid mixed with an abrasive into the shaft hole can be prevented so that the intrusion of fluid mixed with an abrasive into the housing can be effectively prevented. 
         [0015]    According to the fourth and fifth aspects of the present invention, the fluid mixed with an abrasive is prevented from intruding into the shaft hole via the outer circumferential surface of the housing and the side end surface of the housing in an effective manner. 
         [0016]    According to the sixth aspect of the present invention, the fluid mixed with an abrasive that is about to intrude into the inside of the annular protrusion is guided out of the housing along the tapered inner circumferential surface of the annular protrusion so that the intrusion of the fluid mixed with an abrasive into the shaft hole can be effectively prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a longitudinal section view of a guide roller given as a first embodiment of the present invention; 
           [0018]      FIG. 2  is a side end view of the guide roller of the first embodiment; 
           [0019]      FIG. 3  is a front end view of a pulley main body configured to the attached to the guide roller of the first embodiment; 
           [0020]      FIG. 4  is a side end view of an end cap of the guide roller of the first embodiment; 
           [0021]      FIG. 5  is a longitudinal section view of a guide roller given as a second embodiment of the present invention; and 
           [0022]      FIG. 6  is a longitudinal section view of a guide roller given as a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0023]    Referring to  FIGS. 1 to 4 , a guide roller given as a first embodiment of the present invention is described in the following. In the following description, the “left hand side” and the “right hand side” as used in the following description are based on the orientation of the guide roller as illustrated in  FIG. 1 , and the left to right direction is referred to as the axial direction. 
         [0024]    The guide roller  1  is designed to apply a tension to a cutting wire used for cutting a work by using a wire saw not shown in the drawing, and comprises a housing  4  receiving a pair of bearings  2  and  3  therein, a pulley main body  5  (see  FIG. 3 ) secured to the outer periphery of the housing  4  and a support shaft  6  rotatably supporting the housing  4 . A pair of wires not shown in the drawing are passed around the two wire grooves  7  formed circumferentially in the outer circumferential surface of the pulley main body  5 . 
         [0025]    The housing  4  comprises a substantially cylindrical housing main body  11  and an end cap  13  connected to an end of the housing main body  11  by using threaded bolts  12 . The pulley main body  5  is attached to the housing  4  by fitting a barrel part  14  of the housing main body  11  into a mounting hole  5   a  of the pulley main body  5  and attaching the end cap  13  to the right end of the barrel part  14 . At this time, the pulley main body  5  is fixedly clamped at two side surfaces  5   b  and  5   c  thereof by a flange part  15  formed on the left end of the barrel part  14  and an annular support part  16  formed in the end cap  13 . 
         [0026]    The part of the housing  4  to the left of the flange part  15  on the outer circumference of the flange part  15  is formed with a first annular stepped portion  17  and a second annular stepped portion  18  each shaped like a base end of a cone in a terraced arrangement. The second annular stepped portion  18  is reduced in diameter as compared with the flange part  15  (or relatively closer to the center of the housing  4 ), and the first annular stepped portion  17  is provided as a part having a reduced diameter as compared with the second annular stepped portion  18 . Each of the first and second annular stepped portions  17  and  18  is provided with an annular axial end surface  17   a,    18   a  extending perpendicularly to the axial line, and a tapered outer circumferential surface  17   b,    18   b  progressively increasing in diameter in the axially outer direction. Therefore, in the vertical sectional view shown in  FIG. 1 , each annular stepped portion  17 ,  18  is provided with a pair of radially outwardly directed tip defined by the annular axial end surface  17   a,    18   a  and the tapered outer circumferential surface  17   b,    18   b  intersecting at an acute angle. 
         [0027]    A contact surface  16   a  of the annular support part  16  of the end cap  13  configured to engage the opposing side surface  5   c  of the pulley main body  5  is formed with a spiral groove  21  as shown in  FIG. 4  so that the pulley main body  5  may be fixedly secured in a reliable manner. More specifically, the pulley main body  5  made of relatively soft material such as urethane to minimize the possibility of breaking the wire may decrease in thickness when turned at high speed owing to the centrifugal force, but the presence of the spiral groove  21  prevents the slipping of the pulley main body  5  relative to the housing  4  even in such a case. A plurality of concentric grooves may also be formed instead of the spiral groove  21  to achieve the same goal. 
         [0028]    Each of the bearings  2  and  3  consists of an identical double shield deep-groove ball bearing, and is press fitted into a bearing retaining chamber  31  defined by the inner circumferential surface of the housing main body  11 . An inner collar  32  is interposed between the inner race  2   a  of the bearing  2  and the inner race  3   a  of the bearing  3  in a rotationally fast manner with respect to the both inner races  2   a  and  3   a.  An outer collar  33  is interposed between the outer race  2   b  of the bearing  2  and the outer race  3   b  of the bearing  3  so as to surround the inner collar  32 . The bearings  2  and  3  are thereby axially spaced apart by a prescribed distance by the two collars  32  and  33  in a stable manner. The radial thickness of each of the inner collar  32  and the outer collar  33  is selected so as to minimize the gap between the outer circumferential surface of the inner collar  32  and the inner circumferential surface of the outer collar  33 . Thereby, even when the internal pressure of the guide roller  1  is caused to drop owing to the drop in the temperature of the air inside the guide roller  1  following the cessation of the rotation of the guide roller  1 , the drawing of the cutting fluid mixed with an abrasive into the guide roller  1  from outside can be minimized. 
         [0029]    The right end of the bearing retaining chamber  31  defined inside the housing main body  11  is closed by a plug member  41  which comprises a circular disk part  41   a  and an annular projection  41   b  projecting leftward from the disk part  41   a  so as to define a retaining space for an O-ring  43  jointly with the inner circumferential surface of the housing main body  11  and an annular support plate  42 . The plug member  41  and the O-ring  43  jointly prevent intrusion of cutting fluid mixed with an abrasive from intruding into the bearing retaining chamber  31  from the side of the end cap  13 . The rightward displacement of the plug member  41  is prevented by a stop ring  45  received in an circumferential groove  44  formed in the housing main body  11 . 
         [0030]    The housing main body  11  is provided with a shaft hole  50  that opens at the left side end wall of the housing main body  11  and communicates with the interior of the bearing retaining chamber  31  to permit the introduction of the support shaft  6  into the bearing retaining chamber  31  to be supported by the bearings  2  and  3 . The shaft hole  50  is defined by the tapered inner circumferential wall surface of the housing main body  11  that progressively diminishes in diameter toward inside the housing main body  11 . 
         [0031]    The support shaft  6  is provided with a journal portion  61  at a free end thereof which is fitted into the inner races  2   a  and  3   a  of the bearings  2  and  3 . The axial end of the journal portion  61  is fixedly attached to a fixing ring  63  by using a fixing screw  62  so that the bearings  2  and  3  are clamped between the fixing ring  63  and the front end surface of the tapered enlarged diameter portion  64  located to the rear of the journal portion  61 . The tapered enlarged diameter portion  64  is given with a tapered shape that progressively decreases in diameter toward the journal portion  61 , and is provided with a first annular projection  65  and a second annular projection  66  in an axially spaced apart relationship. The outer circumferential surface  65   a,    66   a  of each annular projection  65 ,  66  is tapered at a same angle as the wall surface of the shaft hole  50 . The head  67  of the support shaft  6  is provided with a threaded connecting part  68  projecting therefrom for connection with a guide roller support mechanism not shown in the drawings. 
         [0032]    The left end of the tapered enlarged diameter portion  64  of the support shaft  6  is fitted with a cover member  71  overlying the shaft hole  50 . The cover member  71  covers the entire shaft hole  50  in cooperation with the support shaft  6 . The cover member  71  is centrally provided with a mounting hole  72  which receives the tapered enlarged diameter portion  64  therein. The cover member  71  is provided with a larger diameter than the first annular stepped portion  17 , and is curved toward the housing main body  11  along the outer periphery  73  thereof so as to cover the first annular stepped portion  17 . The outer peripheral edge  73   a  of the outer periphery part  73  is located adjacent to the axial end surface  18   a  of the second annular stepped portion  18 . 
         [0033]    The guide roller  1  discussed above may be used in an environment exposed to cutting fluid mixed with an abrasive used in association with a wire saw. The fluid that may intrude into the shaft hole  50  from the outer periphery of the housing  4  is thrown radially outward (or radially away from the shaft hole  50 ) by the centrifugal force that is created by the rotation of the housing  4  and acts upon the fluid as it passes along the first and second annular stepped portions  17  and  18 . The fluid that is directed into the shaft hole  50  from the side end (or the left end part) of the housing  4  is blocked by the cover member  71 . If the fluid is introduced into the shaft hole  50  via the gap between the housing main body  11  and the cover member  71 , the fluid is thrown out of the housing  4  (or leftward) along the slanted wall surface of the shaft hole  50 . 
         [0034]    The fluid that may pass through the gap between the housing main body  11  and the cover member  71 , and then intrude into the shaft hole  50  via the outer circumferential surface of the support shaft  6  is also guided by the first and second annular projections  65  and  66  provided on the support shaft  6  onto the wall surface of the shaft hole  50 , and thence to outside the housing  4 . 
         [0035]    An air pressure supply passage  81  is formed within the support shaft  6  for supplying air to the bearings  2  and  3 . The air pressure supply passage  81  extends from an opening  81   a  formed in the threaded connecting part  68  to a pair of openings  81   b  formed on a part of the tapered enlarged diameter portion  64  located between the first and second annular projections  65  and  66 . 
         [0036]    The outer circumferential surface  65   a  of the first annular projection  65  is located adjacent to the wall surface of the shaft hole  50  while the outer circumferential surface  66   a  of the second annular projection  66  is located more spaced from the wall surface of the shaft hole  50 . Therefore, the air is allowed to be supplied from the openings  81   b  without being obstructed so that the intrusion of the fluid into the bearing retaining chamber  31  via the outer circumferential surface of the support shaft  6  can be avoided. By supplying air in this fashion, not only the centrifugal force but also the air pressure promotes the reversing of the intruding flow of the fluid out of the housing  4 , and prevents the intrusion of the fluid into the bearing retaining chamber  31 . 
         [0037]    In this case, it is also possible to supply oil mist (air mixed with a lubricant) into the housing  4  via the air pressure supply passage  81 . If oil mist is used for lubrication, the supply of lubricating oil into the housing  4  is enabled even when the housing  4  is in rotation without being hindered by the centrifugal force. Also, the space between the wall surface of the shaft hole  50  and the outer circumferential surface of the tapered enlarged diameter portion  64  of the support shaft  6  is filled with the oil mist, and this is also effective in preventing the intrusion of the fluid into this space. Also, when oil mist is used, the temperature drop following the cessation of the rotation of the guide roller  1  causes a relatively small drop in the internal air pressure so that the drawing of the fluid into the housing  4  from outside owing to the drop in the internal pressure can be effectively avoided. The use of oil mist provides the further advantage of preventing the rusting of the bearings  2  and  3 . 
       Second Embodiment 
       [0038]    A guide roller given as a second embodiment of the present invention is described in the following with reference to  FIG. 5 . In the second embodiment, the parts corresponding to those of the first embodiment are denoted with like numerals without repeating the description of such parts. 
         [0039]    The guide roller  1  of the second embodiment is similar to the guide roller of the first embodiment except for the structure of the cover member  71 . Referring to  FIG. 5 , the cover member  71  of the second embodiment is provided with a larger diameter than the flange part  15 . More specifically, an outer periphery part  73  of the cover member  71  covers not only the first and second annular stepped portions  17  and  18  but also the flange part  15 , and curves toward the housing main body  11 . The outer peripheral edge  73   a  of the outer periphery part  73  is positioned in an axially middle part of the flange part  15 . By increasing the area of the housing main body  11  covered by the cover member  71 , the intrusion of fluid mixed with an abrasive into the bearing retaining chamber  31  can be prevented even more effectively. 
       Third Embodiment 
       [0040]    A guide roller given as a third embodiment of the present invention is described in the following with reference to  FIG. 6 . In the third embodiment, the parts corresponding to those of the first embodiment are denoted with like numerals without repeating the description of such parts. 
         [0041]    The guide roller  1  of the third embodiment is similar to the guide roller of the first embodiment except for the changes made to the first and second annular stepped portions  17  and  18  of the first embodiment (See  FIG. 1 ) to prevent the intrusion of fluid mixed with an abrasive. More specifically, as illustrated in  FIG. 6 , an annular protrusion  91  is formed on the left side end of the housing  4  so as to surround the opening of the shaft hole  50 , and projects away from the housing  4  (leftward). The outer circumferential surface  91   a  of the annular protrusion  91  is continuously connected to the barrel part  14  of the housing main body  11  via the flange part  15 . The inner circumferential surface  91   b  of the annular protrusion  91  is tapered so as to progressively increase in diameter toward the outside of the housing main body  11 . The cover member  71  is provided opposite to the inner circumferential surface of the annular protrusion  91 , and the free end  91   c  of the annular protrusion  91  extends leftward beyond the cover member  71 . The outer peripheral edge  73   a  of the outer periphery  73  of the cover member  71  is loosely received in an annular groove  92  formed inside the annular protrusion  91 . 
         [0042]    In the guide roller  1  of the third embodiment, the fluid mixed with an abrasive intruding into shaft hole  50  from the outer periphery of the housing  4  is guided radially outward (or away from the shaft hole  50 ) as the fluid advances across the annular protrusion  91  provided at the opening end of the shaft hole  50  under the centrifugal force caused by the rotation of the housing  4 . In particular, the fluid that has reached inside the annular protrusion  91  (or the gap between the annular protrusion  91  and the cover member  71 ) is guided along the tapered inner circumferential surface  91   b  to the free end  91   c  of the annular protrusion  91  (outward from the housing  4 ) so that the intrusion of the fluid into the shaft hole  50  can be effectively prevented. 
         [0043]    The air pressure supply passage  81  (See  FIG. 1 ) was omitted in the guide roller  1  of the third embodiment illustrated in  FIG. 6 . According to this arrangement, the intrusion of cutting fluid mixed with an abrasive can be effectively prevented as compared to the conventional guide roller even when the air pressure supply passage  81  is omitted. By omitting the air pressure supply passage  81 , the need for the arrangement for supplying air can be eliminated, and the running cost such as the cost of electric power and the impact on the environment can be reduced. The air pressure supply passage  81  may be omitted also in the first and/or second embodiments similarly as in the third embodiment. 
         [0044]    Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims. For instance, the guide roller of the present invention is effective in preventing the intrusion of not only cutting fluid mixed with an abrasive but also water and other fluids into the bearing retaining chamber  31 . The layout and number of the annular stepped portions in the housing main body  11 , and the layout and number of the annular projections of the support shaft can be freely modified without departing from the spirit of the present invention. 
         [0045]    It should also be noted that the various components of the guide rollers of the different embodiments are not necessarily essential for the implementation of the present invention, but may be modified or omitted without departing from the spirit of the present invention. For instance, the annular projections formed on the support shaft, the cover member mounted on the support shaft and other components of the embodiment may be omitted when desired. 
       GLOSSARY 
       [0000]    
       
           1  guide roller 
           2 ,  3  bearing 
           4  housing 
           5  pulley main body 
           6  support shaft 
           11  housing main body 
           13  end cap 
           14  barrel part 
           15  flange part 
           16  annular support part 
           17  first annular stepped portion 
           18  second annular stepped portion 
           31  bearing retaining chamber 
           50  shaft hole 
           61  journal portion 
           64  tapered enlarged diameter portion 
           65  first annular projection 
           66  second annular projection 
           71  cover member 
           91  annular protrusion 
           91   b  inner circumferential surface