Abstract:
An end face polishing apparatus has a support member mounted on the main body for undergoing revolving and rotational movement during a polishing operation, a tubular member mounted on the support member for rotation and revolving movement therewith, a lapping member mounted on the support member for rotation and revolving movement therewith, and a polishing fixture for supporting at least one workpiece having an end face for pressure contact with the lapping member to polish the end face of the workpiece during rotation and revolving movement of the lapping member. The polishing fixture has radially outwardly projecting guide members for contacting the tubular member to limit the amount of polishing of the end face of the workpiece in a pressing direction during rotation and revolving movement of the lapping member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a division of U.S. application Ser. No. 10/187,574, filed on Jul. 2, 2002, now U.S. Pat. No. 6,736,551, and priority thereto for common subject matter is hereby claimed. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an end face polishing apparatus for polishing an end face of a rod-shaped member such as a fiber for optical communication. 
   2. Description of the Background Art 
   Fibers for optical communication are adhesively secured in the central hole of a ferrule, a main member of a connector, and then the ferrule end face and the end face of fibers are polished together and thus finished into a smooth, mirror surface. If the polished end faces of the ferrule and the fibers are not vertical to the central axis of the ferrule or if there is a flaw on the polished faces, the precision in positioning such ferrules as they are connected facing each other in an optical connector is lowered, and the loss increases. Therefore, the face of the ferrule including the optical fibers must be polished with high precision. 
   A conventional apparatus for polishing the end faces of optical fibers is disclosed for example by Japanese Patent Laid-Open No. 26456/1991. The disclosed end face polishing apparatus includes an eccentric adapter that rotates on a circle concentric with a rotating disc, and a planetary gear that transmits the rotation of a revolving motor to the eccentric adapter. These elements are coupled in a lapping machine, so that the lapping machine is allowed to rotate and revolve, while the end faces of a plurality of ferrules held by a polishing fixture are pressed against a lapping member secured to the lapping machine for lapping. 
   As described above, in the conventional optical fiber end face polishing apparatus, the plurality of ferrules held by the polishing fixture are pressed by a spring or the like against the lapping member secured to the lapping machine that rotates and revolves. However, the ferrules are polished based on time, and the polishing length for the ferrules cannot be controlled. When the ferrules mounted on the polishing fixture have the same length, there would be no problems. However their lengths are not equal because of the precision of ferrules or adhesive used to secure optical fibers coming out from the tip ends of ferrules and cured. When therefore such ferrules having different lengths are slid into contact with the lapping machine, the polishing fixture could be inclined relative to the lapping machine, and the lapping angle, the radius of curvature and the eccentricity could be deviated. The ferrules after the polishing could have different lengths. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the disadvantages of the conventional art and it is an object of the invention to provide an end face polishing apparatus with improved polishing precision regardless of the length of ferrules when end faces of the ferrules are polished. 
   According to a first aspect of the present invention directed to a solution to the above disadvantages, an end face polishing apparatus polishing a rod-shaped member mounted at a polishing fixture by pressing the rod-shaped member against a lapping member on a lapping machine provided on a surface plate which is supported at the main body of the apparatus to rotate and rock includes a plurality of rod-shaped guide members provided at the polishing fixture and radially outwardly projecting, and a tubular member capable of supporting the polishing fixture through the guide members on the surface plate. The guide member sat the polishing fixture and the tubular member abut against each other, so that the movement of the polishing fixture in the pressing direction is restricted. 
   According to a second aspect of the invention, in the end face polishing apparatus according to the first aspect, the polishing fixture is provided with at least three such guide members. 
   According to a third aspect of the invention, in the end face polishing apparatus according to the second aspect, the polishing fixture is provided with six such guide members. 
   According to a fourth aspect of the invention, in the end face polishing apparatus according to any one of the first to third aspects, the tubular member is placed on the surface plate as its movement in the radial and circumferential directions is restricted. 
   According to a fifth aspect of the invention, in the end face polishing apparatus according to the fourth aspect, the tubular member and the surface plate are closely contacted by magnetic force. 
   According to a sixth aspect of the invention, in the end face polishing apparatus according to any one of the first to fifth aspects, the rod-shaped member is a ferrule including a ferrule tubular body for holding optical fibers and a collar member provided at a rear end of the ferrule tubular body for holding coated optical fibers. 
   According to a seventh aspect of the invention, in the end face polishing apparatus according to any one of the first to six aspects, the position to provide the lapping machine at the surface plate and the position to provide the tubular member are level and controlled in height by grinding, and the heights of the lapping machine and the tubular member are controlled by grinding. 
   According to an eighth aspect of the invention, an end face polishing apparatus polishes a rod-shaped member mounted at a polishing fixture by pressing the rod-shaped member against a lapping member on a lapping machine provided on a surface plate that is supported at the main body of the apparatus to rotate and rock, the polishing fixture has a plurality of rod-shaped guide members radially outwardly projecting, and the apparatus includes a tubular member supporting the polishing fixture through the guide members on the surface plate. 
   According to a ninth aspect of the invention, the surface of the guide member in abutment against the tubular member in the end face polishing apparatus according to the eighth aspect is a plane. 
   According to a tenth aspect of the invention, the surface of the tubular member in abutment against the guide member in the end face polishing apparatus according to the eighth aspect is a plane. 
   According to an eleventh aspect of the invention, the plane in the end face polishing apparatus according to the eighth aspect is horizontal. 
   According to a twelfth aspect of the invention, an end face polishing apparatus includes a tubular member at the outer periphery of a surface of a surface plate, and a lapping machine provided on the surface of the surface plate, and the lapping machine is parted from the tubular member in the axial direction and has a height lower than that of the tubular member. 
   According to a thirteenth aspect of the invention, an end face polishing apparatus includes a tubular member at the outer periphery of a surface of a surface plate, a lapping machine that is provided on the surface of the surface plate, parted from the tubular member in the axial direction and has a height lower than that of the tubular member, and a polishing fixture having a guide member held slidably at a surface on the side of the tubular member opposite to the side facing the surface plate. 
   According to a fourteenth aspect of the invention, an end face polishing apparatus includes a tubular member at the outer periphery of a surface of a surface plate, a lapping machine that is provided on the surface of the surface plate, parted from the tubular member in the axial direction and has a height lower than that of the tubular member, and a polishing fixture having a guide member thereon. The guide member is held slidably at a surface on the side of the tubular member opposite to the side facing the surface plate. 
   According to a fifteenth aspect of the invention, an end face polishing apparatus includes a tubular member at the outer periphery of a surface of a surface plate, and a lapping machine parted from the tubular member in the axial direction and having a height lower than that of the tubular member on the surface of the surface plate, and the polishing height is controlled based on the difference between the heights of the tubular member and the lapping machine. 
   According to a sixteenth aspect of the invention, an end face polishing jig includes a plurality of guide members radially outwardly projecting. 
   According to a seventeenth aspect of the invention, a polishing fixture holds a ferrule at an inclined surface on a outer peripheral side thereof, the ferrule includes a ferrule tubular body for holding optical fibers and a collar member provided at the rear end of the ferrule tubular body for holding coated optical fibers, the polishing fixture holds the ferrule so that the front end of the ferrule tubular body is positioned at the lower side and the lower part of the circle of the collar member in contact with the outer periphery of the ferrule is positioned at the upper surface. 
   According to an eighteenth aspect of the invention, an end face polishing jig includes a guide member radially outwardly projecting at the upper surface of the polishing fixture in the seventeenth aspect, and having a lower surface in a position on an extension of the upper surface of the polishing fixture. 
   According to the invention, a polishing fixture is provided with a guide member and a tubular member capable of supporting the polishing fixture through the guide member on a surface plate, so that the polishing fixture can be kept parallel to the surface plate, and the polishing precision for bar-shaped members can be improved. In addition, the lengths of the bar-shaped members after polishing can be equalized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic sectional view of an end face polishing apparatus according to one embodiment of the present invention; 
       FIG. 2  is a perspective view of a surface plate, a lapping machine and a polishing fixture according to the embodiment; 
       FIG. 3  is a plan view of the surface plate, the lapping machine and the polishing fixture according to the embodiment; 
       FIG. 4  is a sectional view of the surface plate, the lapping machine and the polishing fixture according to the embodiment; 
       FIG. 5A  is a perspective view of the surface plate, the lapping machine and a tubular member according to the embodiment; 
       FIG. 5B  is a plan view of the tubular member; 
       FIGS. 6A and 6B  are plan views each showing a rod-shaped member according to the embodiment; and 
       FIG. 7  is a sectional view showing how the rod-shaped member is secured according to the embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will now be described in conjunction with the accompanying drawings. 
     FIG. 1  is a schematic sectional view of an end face polishing apparatus according to one embodiment of the invention.  FIG. 2  is a perspective view of a surface plate, a polishing fixture, and a lapping machine.  FIG. 3  is a plan view of the surface plate and the polishing fixture.  FIG. 4  is a sectional view of the surface plate, the lapping machine, and the polishing fixture. 
   As shown in  FIG. 1 , the central part of a first rotation transmission plate  12  is rigidly coupled to the rotation shaft of a rotating motor  11 . A plurality of first coupling pins  13  are secured to the first rotation transmission plate  12  concentrically around the rotation center of the first rotation transmission plate  12 . The first coupling pins  13  are each rotatably coupled to an eccentric part of a corresponding one of rotation transmission plates  14 . Second coupling pins  15  are each secured at an eccentric part of a corresponding one of the rotation transmission plates  14 . The second coupling pins  15  are rotatably coupled to a second rotation transmission plate  16 . 
   Meanwhile, the central part of a driving gear  18  is rigidly coupled to the rotation shaft of a revolving motor  17  and the driving gear  18  is engaged with a driven gear  19 . The driven gear  19  is rigidly coupled to the lower periphery of a revolution transmission shaft  20 , the upper periphery of which is engaged with the bearing tube  22  of an apparatus main body  21 . A rotation shaft  23  is rotatably fitted in a position a prescribed distance deviated from the center of the revolution transmission shaft  20 , and the lower end of the rotation shaft  23  is rigidly coupled to the rotation center of the second rotation transmission plate  16 . 
   The rotation shaft  23  has its upper end coupled to a support member in the form a surface plate  25  through a coupling member  24 . At the upper surface of the surface plate  25 , a lapping machine  27  is provided. The lapping machine  27  is provided with a lapping member  28  such as a lapping sheet including a medium such as electro-forming diamond through a detachably fitted surface boss  26 . 
   On the surface plate  25 , there is a tubular member  29  whose one end face is abutted against the surface (e.g., a periphery of the surface) of the surface plate or suppport member  25  as the movement of the tubular member in the radial and circumferential directions is restricted. The surface of the support member  25  and an inner wall surface of the tubular member form a cavity C within which the lapping member  28  is disposed. 
   More specifically, as shown in  FIGS. 5A and 5B , the tubular member  29  is in a tubular shape whose inner diameter is larger than an outer diameter of a polishing fixture  40  which excludes a guide member  48  that will be described below. The end face of the tubular member abutted against the surface of the surface plate  25  is provided with at least three raised portions  30  at equal intervals projecting toward the surface plate  25 . The raised portions  30  fit with recessed portions  31  provided at the surface plate  25  corresponding to the raised portions  30 , so that the movement of the tubular member in the radial and circumferential directions is restricted. Note that  FIG. 5A  is a perspective view of the surface plate  25 , the tubular member  29  and the lapping machine  27 , and  FIG. 5B  is a plan view of the tubular member  29 . 
   The tubular member  29  as described above is formed to have a prescribed height from the surface plate  25 , so that the member must be positioned in the circumferential direction on the surface plate  25 . Therefore, according to the embodiment, an additional raised portion  30  is provided between the three raised portions  30  to restrict the radial and circumferential movement, so that the tubular member  29  is sure to be attached in the same direction. This allows the height of the tubular member  29  to be highly precise accordingly. 
   The number and shape of the raised portions  30  and the recessed portions  31  provided at the tubular member  29  and the surface plate  25  are not particularly limited. The intervals among the three raised portions  30  may be unequal and the attaching direction may always be the same, or four or more raised portions  30  may be provided. 
   The tubular member  29  is placed as it is in close contact onto the surface plate  25 . The close contacted state is provided by magnetic force. More specifically, as shown in  FIGS. 5A and 5B , a plurality of permanent magnets  29   a  are embedded in the surface of the tubular member  29  in abutment against the surface plate  25 . 
   As shown in  FIG. 4 , the position to place the lapping machine  27  at the surface plate  25  and the position to place the tubular member  29  are level with each other. The height control is highly precisely performed by grinding and the heights of the tubular member  29  and the lapping machine  27  are also highly precisely controlled by grinding. 
   More specifically, the end face of the tubular member  29  on the side of the polishing fixture  40  and the polishing surface of the lapping machine  27  have their heights controlled, so that no error is caused because of height difference among positions. 
   The tubular member  29  slides in contact with guide members  48  provided at the polishing fixture  40  which will be described, and therefore is preferably made of an oil less metal for example which has low frictional resistance when it slides in contact. 
   The tubular member  29  is ground as it is placed on the surface plate  25  so that the attaching direction is always the same, and therefore its height from the surface plate  25  can be set highly precisely. Preferably, in a similar manner, a plurality of such tubular members  29  having different heights are prepared. Thus, the height to be achieved by polishing can readily be changed with high precision. 
   Meanwhile, the polishing fixture  40  having a plurality of rod-shaped members W secured is supported by the apparatus main body  21  by a supporting mechanism  50 . 
   The supporting mechanism  50  and the polishing fixture  40  will now be detailed. 
   As shown in  FIGS. 2 to 4 , the polishing fixture  40  has a polygonal shape, and has a fitting  42  facing a recessed portion  41  formed at each side surface. The rod-shaped member W is held between the recessed portion  41  and the fitting  42  and the fitting  42  is secured with fitting securing screws  43 , so that the rod-shaped member W is detachably secured to the polishing fixture  40 . 
   According to the embodiment, the polishing fixture  40  has a dodecagon shape, to each side of which a rod-shaped member W can be secured, in other words, twelve rod-shaped members W altogether can be secured. The type of the rod-shaped member W is not limited and may be a rod-shaped member such as a ferrule, a rod-shaped member having a rectangular section such as a multi-fiber ferrule and a multi-fiber optical connector. The fitting  42  and the fitting securing screw  43  used to secure the rod-shaped member W to the polishing fixture  40  are not particularly limited. 
   In the center of the upper surface of the polishing fixture  40 , a polishing fixture boss  44  is secured by boss securing screws  45 . There is a rectangular slit  46  penetrating through the center of the polishing fixture boss  44  in the thickness-wise direction and opened at a side. There is also a plate shaped, chamfered plastic cover  47  on the polishing fixture boss  44 . 
   At the upper surface of the polishing fixture  40 , there are the rod-shaped guide members  48  that project radially outwardly from the polishing fixture  40 . 
   The guide members  48  are each secured to the upper surface of the polishing fixture  40  by two guide member securing screws  49  and slide in contact with the end face of the tubular member  29  that rotates as the surface plate  25  rotates, so that the movement of the polishing fixture  40  in the pressing direction is restricted to keep parallel the polishing fixture  40 . 
   Therefore, at least three guide members  48  are necessary for the polishing fixture  40 . Meanwhile, if the number of the guide members  48  is three, the rod-shaped members W could be ground more than necessary because part of the polishing fixture  40  might have a height lower than the tubular member  29  between two slidably contacting guide members  48  when the polishing fixture  40  slides in contact with the tubular member  29  in an oblique direction. Therefore, the number of guide members  48  is preferably at least six. If there are many guide members  48 , the weight of the polishing fixture  40  increases, which could lower the polishing precision, so that six guide members  48  are preferably provided. There is a recess in the lower part in the center of the length of the guide member  48  over the fitting  42  so that the rod-shaped member W can readily be mounted. 
   According to the embodiment, as shown in  FIG. 6A , the rod-shaped member W secured to the polishing fixture  40  is a ferrule  60  including a ferrule tubular body  61  made of zirconia for holding optical fibers inserted therein and a collar portion  62  made of a metal fit into the rear end of the tubular body for holding inserted coated optical fibers. Alternatively, as shown in  FIG. 6B , the rod-shaped member W may be a ferrule  60  including the ferrule tubular body  61  and the collar portion  62  formed in an integral form. Note that  FIGS. 6A and 6B  are plan views each showing an example of the rod-shaped member. 
   According to the embodiment, the tip end face of the collar portion  62  of the ferrule  60  as the rod-shaped member W is secured in abutment against the polishing fixture  40 . Therefore, the guide members  48  slidably contact the tubular member  29  in the level as high as that of the tip face of the collar portion  62  of the ferrule  60 , so that the length of the ferrule tubular body  61  can readily be controlled. 
     FIG. 7  is a sectional view showing how the ferrule  60  having the collar portion  62  is attached to the polishing fixture  40 . The polishing fixture  40  has a side face inclined outwardly downwardly in the outer peripheral direction. A contacting point P between the collar portion  62  of the rod-shaped member W and the outer periphery of the ferrule  60  is located at the upper surface of the polishing fixture  40 , so that the attaching position in the height-wise direction of the rod-shaped member W can therefore be always constant. There are guide members  48  projecting radially outwardly at the upper part of the polishing fixture  40 . The bottom of the guide members  48  is level with the point P. Here, the rod-shaped member W is secured with the fitting  42  as if the attachment manner example shown in  FIG. 4  is inclined. Thus, the difference between the heights of the tubular member  29  and the lapping machine  27  in  FIG. 4  allows the polishing height for the rod-shaped member W to be constant. 
   Meanwhile, the supporting mechanism  50  is held such that the supporting portion  51  provided approximately parallel to the lapping machine  27  at the main body  21  is urged downward by prescribed pressing force. 
   More specifically, at the base end of the supporting portion  51 , there is a through hole  52  penetrating in the thickness-wise direction, and an adjusting screw  53  threadably engages with the apparatus main body  21  through the through hole  52 . The adjusting screw  53  is placed through an urging spring  54  that abuts against the flange portion  53   a  of the adjusting screw  53  and the supporting portion  51  to urge the supporting portion  51  downward by prescribed pressing force. 
   The pressing force by the urging spring  54  can be adjusted based on the position of the flange portion  53   a  of the adjusting screw  53 , in other words, based on how much the adjusting screw  53  is engaged. 
   Note that the supporting portion  51  has its base end portion penetrated through a slide pin  56  provided at the apparatus main body  21 , so that the movement of the adjusting screw  53  in the rotation direction can be restricted. 
   At the tip end of the supporting portion  51 , there is a pressing portion  55  having a square pole shape that projects toward the polishing fixture  40  and fits into the slit  46  of the polishing fixture boss  44 . The pressing portion  55  is engaged with the slit  46  of the polishing fixture boss  44 , so that the polishing fixture  40  is pressed downward to the supporting portion  51  by prescribed pressing force and has its movement restricted in the rotation direction. 
   More specifically, the polishing fixture  40  is urged toward the lapping machine  27  by the supporting portion  51  as it has its movement restricted in the rotation direction by the pressing portion  55  of the supporting portion  51 , and supported on the lapping machine  27  through the tip end of the rod-shaped members W secured by the fittings  42 . Once the rod-shaped members W are polished for a prescribed amount, the guide members  48  slide in contact with the tubular member  29  on the surface plate  25 , and support the polishing fixture  40  parallel to the lapping machine  27 , so that the amount of polishing the rod-shaped members W is restricted. 
   Thus, the polishing fixture  40  is provided with the guide members  48  and the tubular member  29  capable of supporting the polishing fixture  40  through the guide members  48  is provided on the surface plate  25 , so that the lengths of the rod-shaped members W can be equal, and deviations and variations in the radius of curvature, the polishing angle, and the eccentricity can be reduced. As in the embodiment, when the rod-shaped member W is a ferrule, the removal of adhesive coming out from the tip end of the ferrule is not necessary for equalizing the lengths of the rod-shaped members W, and therefore the polishing step can be simplified. 
   In addition, the heights of the surfaces of the tubular member  29  and the lapping machine  27  provided at the surface plate  25  are controlled, so that the length of the rod-shaped member W can readily be specified and errors in the length can be prevented. 
   The tubular members  29  having different heights are prepared and switchably used, so that the length of the rod-shaped member W after polishing can readily be controlled. 
   The operation of the above end face polishing apparatus according to the embodiment will now be described. 
   As shown in  FIG. 1 , the revolution motor  17  is driven to rotate the revolution transmission shaft  20  through the gears  18  and  19 , and the lapping machine  27  revolves by a prescribed amount of eccentricity. In this case, the rotation shaft  23  is located in the revolution transmission shaft  20 , while a plurality of rotation transmission plates  14  are provided in the space between the rotation shaft  23  and the first rotation transmission plate  12 , the rotation transmission plates  14  rotate around the first coupling pins  13  in the same rotation phase as the revolution transmission shaft  20 . Therefore, regardless of whether the first rotation transmission plate  12  is stationary or rotates, the rotation of the revolution transmission shaft  20  is not restricted. 
   Meanwhile, the rotation motor  11  is driven to rotate the first rotation transmission plate  12 , while the first coupling pins  13  are located concentrically with the first rotation transmission plate  12 , and therefore move in the same trajectory as the above. The rotation shaft  23  is deviated by a prescribed distance from the center, while the shaft is coupled through the rotation transmission plates  14 , and therefore the rotation at the same number of revolutions as that of the first rotation transmission plate  12  is transmitted to the rotation shaft  23 . 
   Thus, the surface plate  25  revolves as it rotates by the rotation of the revolution transmission shaft  20  and the rotation shaft  23 , so that the lapping machine  27  and the tubular member  29  on the surface plate  25  are rotated. 
   Meanwhile, with respect to the lapping member  28  at the lapping machine  27 , the polishing fixture  40  has its movement in the rotation direction restricted by the pressing portion  55  of the supporting portion  51 , and is urged toward the lapping machine  27 . In this way, the end faces of rod-shaped members W are pressed against the lapping member  28 . 
   At the time, the difference between the lengths of the rod-shaped members W causes the polishing fixture  40  to be not parallel to the lapping machine  27 , and the end faces of the rod-shaped members W are polished into an inclined surface. However, as the polishing proceeds, the guide members  48  provided at the polishing fixture  40  slide in contact with the tubular member  29  provided on the surface plate  25 , so that the polishing fixture  40  is supported parallel to the lapping machine  27 . Therefore, the tip ends of the rod-shaped members W can be polished with reference to the lapping machine  27 . Thus, the lengths of the rod-shaped members W can be equalized, and deviations and variations in the radius of curvature, the polishing angle, and the eccentricity can be reduced. Consequently, the tip ends of the rod-shaped members W can be processed into an ideal convex sphere. 
   As in the foregoing detailed description of the embodiment, by the end face polishing apparatus according to the present invention, a plurality of rod-shaped guide members are provided at the polishing fixture and the polishing fixture is provided with a tubular member capable of supporting the polishing fixture through the guide members on the surface plate. In this way, the polishing can be performed with reference to the lapping machine, and the lengths of the rod-shaped members can be equalized, and deviations and variations in the radius of curvature, the polishing angle and the eccentricity can be reduced. The removal of adhesive attached to the rod-shaped members is not necessary for equalizing their lengths, and therefore the polishing step can be simplified.