Abstract:
A ferrule end-surface polishing apparatus for polishing an end-surface of a ferrule for an optical fiber is provided. The apparatus includes a ferrule holder having a holder block capable of sandwiching a cylindrical portion of a ferrule, and a guide block for guiding the ferrule to the holder block; a polisher having a rotatable polishing board for polishing an axial end-surface of the ferrule held by the ferrule holder; and a ferrule transfer device for transferring and loading the ferrule into the ferrule holder, and for removing the ferrule therefrom after polishing. With this configuration, the ferrule polishing operation is automated.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a ferrule end-surface polishing apparatus for polishing an end-surface of a ferrule for an optical fiber, and more particularly, to a ferrule end-surface polishing apparatus suitable for automated polishing of a ferrule end-surface. 
     In a conventional apparatus for polishing an end-surface of a ferrule for an optical fiber, for example, as described in JP-A-6-179161, an end portion of a ferrule is securely held by a holding means, and an end-surface of the ferrule is pressed onto an eccentrically rotating polishing platform at a constant pressure to polish the end-surface of the ferrule. 
     In the foregoing conventional apparatus, however, no consideration has been given to automatization which is essential to accommodate a significant increase in demand for optical fiber products in the future. The aforementioned known example discloses automation of polishing alone through the rotation of a polishing machine, and discloses that mounting and holding of ferrules, replacement of polishing paper, and so on are manually performed. For this reason, there has been a problem that the automatization is difficult. Specifically explaining, in the aforementioned conventional apparatus, a ferrule is mounted by inserting the ferrule into a hole slightly larger than the outer diameter of the ferrule (for example, approximately 0.005 mm), made in a ferrule holder, and holding the ferrule with fixing nuts at a fixed height and a fixed angle. 
     The replacement of polishing paper involves operations such as removing a ferrule holder with a ferrule mounted therein, and replacing polishing paper attached on a rotating disk. The insertion of a ferrule into a hole in the ferrule holder is difficult even with human&#39;s hands since even slight inclination would result in a chape. Its automatization would require a highly accurate positioning machine and a highly accurate sensor, but is practically not feasible. In addition, for the replacement of polishing paper, it is difficult, even with human&#39;s hands, to remove a metal-made holder, which is made thick for ensuring a rigidity, with a ferrule mounted therein, leading to a likelihood of breaking an optical fiber. 
     It is an object of the present invention to provide an apparatus for polishing an end-surface of a ferrule, which facilitates the automatization. 
     SUMMARY OF THE INVENTION 
     To achieve the above object, the present invention provides a ferrule end-surface polishing apparatus having holding means for holding a ferrule, and a turntable for rotating and holding polishing paper for polishing an end-surface of the ferrule held by the holding means, wherein the holding means comprises two holder blocks which are movable to each other and have holders formed at opposing portions thereof, and a guide block disposed above the holder blocks for guiding the ferrule moved down from above between the two block holders. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating the general configuration of the present invention; 
     FIG. 2 is a side view illustrating the detailed configuration of a ferrule holder of the present invention; 
     FIG. 3 is a perspective view of a guide holding mechanism of the present invention; 
     FIG. 4 is a plan view of the guide holding mechanism  150  of the present invention; 
     FIG. 5 is a side view for explaining the operation of the guide holding mechanism  150  of the present invention; 
     FIG. 6 is a side view for explaining the operation of the guide holding mechanism  150  of the present invention; 
     FIG. 7 is a side view illustrating a mechanism for holding polishing paper of the present invention; 
     FIG. 8A is a bottom view of a metal plate for holding the polishing paper of the present invention; and 
     FIG. 8B is a plan view of a turntable of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view illustrating the general configuration of an apparatus for polishing an end-surface of a ferrule according to one embodiment of the present invention. 
     An optical fiber supporting unit  10  comprises a bobbin holder  12 . In the bobbin holder  12 , an optical cable  20  wound around a bobbin  22  is set by an optical fiber transfer robot or human&#39;s hands. Also, the optical cable supporting unit  10  comprises cable holders  14 A,  14 B. When the bobbin  22  is set in the bobbin holder  12  by an optical cable transfer robot or human&#39;s hands, both ends of the optical fiber  20  are set to the cable holders  14 A,  14 B, respectively. Here, the optical fiber  20 , is of a double core type, in which two optical cables are included. Ferrules are attached to both leading ends of the optical cable, wherein the number of ferrules is four since this embodiment employs the double core type optical cable. 
     The optical cable supporting unit  10  comprises four ferrule positioning/holding units  100 A,  100 B,  100 C,  100 D. The ferrule positioning/holding units  100 A,  100 B,  100 C,  100 D are all identical in configuration, so that the detailed configuration thereof will be described below as a ferrule positioning/holding unit  100  using FIG.  2 . The ferrule positioning/holding units  100  position and hold four ferrules at both ends of the optical cable  20  at respective predetermined positions. Also, the optical cable supporting unit  10  is movable in the vertical direction (Z direction) by a unit elevating mechanism  16 . 
     A polishing paper setting unit  30  holds a plurality of sheets of polishing paper  32 A, . . . ,  32 L. In this example, assume that the sheets of polishing paper  32 A,  32 L include six sheets of coarse polishing paper  32 A, . . . ,  32 F and six sheets of fine polishing paper  32 G, . . . ,  32 L. Above the polishing paper setting unit  30 , a polishing paper transfer robot  34  is disposed. The polishing paper transfer robot  34  is movable in the X-direction. Also, the polishing paper transfer robot  34  holds a polishing paper chuck mechanism  36 . The polishing paper chuck mechanism  36  is movable in the Y-direction on an arm of the polishing paper transfer robot  34 , and a chuck portion at a leading end thereof is movable in the Z-direction. 
     On the other hand, below the optical cable supporting unit  10 , two rotation/swing mechanisms  40 A,  40 B are disposed. The polishing paper transfer robot  34  and the polishing paper chuck mechanism  36  are adapted to enable automatic replacement of the polishing paper  32  by chucking an arbitrary polishing paper  32  from the polishing paper setting unit  30 , and transferring it to the rotation/swing mechanism  40 A,  40 B for setting therein. 
     Next, using FIG. 2, the ferrule positioning/holding unit  100  for use in the apparatus for polishing an end-surface of a ferrule according to this embodiment will be described for its detailed configuration. 
     FIG. 2 is a side view illustrating the detailed configuration of the ferrule positioning/holding unit for use in the apparatus for polishing an end-surface of a ferrule according to one embodiment of the present invention. As explained in FIG. 1, the apparatus for polishing an end-surface of a ferrule according to this embodiment comprises the four ferrule positioning/holding units  100 A,  100 B,  100 C,  100 D which are all identical in configuration, so that their detailed configuration will be explained herein as the ferrule positioning/holding unit  100 . The same reference numerals as those in FIG. 1 designate the same parts. 
     The optical cable supporting unit  10  is movable in the vertical direction (Z-direction) along a slider  16 S of the unit elevating mechanism  16 . A frame  110  is fixed on the optical cable supporting unit  10 . On the frame  110 , a releasing cylinder  120  is attached through a supporting base  112 , and a block extruding cylinder  130  is attached through a supporting base  114 . Also, a slider  140 S of a Z-moving mechanism  140  is in engagement with a rail  110 R of the frame  110 . The Z-moving mechanism  140  is reciprocally movable in the Z-direction with respect to the frame  110 . A spring  140 SP is attached between the supporting base  112  of the frame  110  and the Z-moving mechanism  140 , and the Z-moving mechanism  140  is suspended by the spring  140 SP. 
     A guide holding mechanism  150  is attached to the Z-moving mechanism  140 . The guide holding mechanism  150  is comprised of two holder blocks  152 ,  154  and a guide block  156 . The detailed configuration of the holder blocks  152 ,  154  will be described later using FIGS. 3 and 4. The holder block  152  is attached to the rail  140 R of the Z-moving mechanism  140  through a slider  150 S, and reciprocally movable in the X-direction. The holder block  152  and the guide block  156  are fixed to the Z-moving mechanism  140 . At a left-hand end of the holder block  152 , a cam surface  152 C is formed. A cam follower  142  is in engagement with the cam surface  152 C. A spring  140 S is tied between the Z-moving mechanism  140  and the guide block  152  for urging the guide block  150  in a direction of an arrow X 1  to hold the engagement of the cam surface  152 C with the cam follower  142 . As the cam follower  142  moves in the Z-direction, the cam follower  142  moves along the cam surface  152 C, and the guide block  152  moves in the X-direction. The cam follower  142  is attached at a leading end of a cam follower shaft  144 . The cam follower shaft  144  is held slidable on a supporting base  146  of the Z-moving mechanism  140 . A stopper  144 ST is disposed in the middle of the com follower shaft  144 . A spring  144 SP is inserted between the supporting base  146  of the Z-moving mechanism  140  and the stopper  144 ST of the cam follower shaft  144  to urge the cam follower shaft  144  in a direction of an arrow Z 1 . The cam follower shaft  144  is in engagement with a shaft  122  of the releasing cylinder  120 . As the releasing cylinder  120  operates, the shaft  122  moves in a direction of an arrow Z 2 . Together with this, the com follower shaft  144  also moves in the same direction. As a result, the cam follower  142  is in engagement with the cam surface  152 C, so that the guide block  152  moves in the direction of the arrow X 1 . 
     A provisionally retaining block  160  is supported on the rail  154 R of the guide block  154  through a slider  160 S and a spring  160 SP. At a leading end of the provisionally retaining block  160 , a retainer  162  is supported for retaining a flange of a ferrule  20 F. Also, a spring  152 SP is suspended between the provisionally retaining block  160  and a holder block  152 . On the other hand, a shaft  132  of the block extruding cylinder  130  is in engagement with a frame  136  for holding a block retaining cylinder  170 . The shaft  172  of the block retaining cylinder  170  is in engagement with the provisionally retaining block  160 . The shaft  172  of the block retaining cylinder  170  is reciprocally movable in the Z-direction. As the shaft  172  of the block retaining cylinder  170  moves in a direction of an arrow Z 3 , the leading end of the shaft  172  presses the provisionally retaining block  160  in a direction of an arrow Z 4  against a spring force of the spring  160 SP. Also, the shaft  132  of the block extruding cylinder  130  is reciprocally movable in the X-direction. As the shaft  132  of the block extruding cylinder  130  moves in the direction of the arrow X 2 , the frame  136  moves in a direction of an arrow X 3 , and further extrudes the provisionally retaining block  160  in a direction of an arrow X 4  against a spring force of the spring  152 SP. 
     Below the guide holder mechanism  150  of the ferrule positioning/holding unit  100 , a rotation/swing mechanism  40  is disposed. The rotation/swing mechanism  40  is comprised of a driving source  42 , a swing arm  44 , a rotating shaft  46 , and a turntable  48 . The driving source  42  swings the swing arm  44  in a direction of an arrow R 1 , and rotates the rotating shaft attached to an end of the swing arm  42  in a direction of an arrow R 2 . A sheet of polishing paper  32  is held on the turntable  48  which is rotated by the rotating shaft  46 . 
     Also, above the guide block  156  of the guide holding mechanism  150  of the ferrule positioning/holding unit  100 , a cable chuck robot  50  is disposed. The cable chuck robot  50  holds an optical fiber having a ferrule  20 F attached at a leading end thereof, and moves the ferrule  20 F to the guide block  156 . 
     Next, the detailed configuration of the guide holding member  150  for use in the apparatus for polishing an end-surface of a ferrule according to this embodiment, will be described using FIGS. 3 and 4. 
     FIG. 3 is a perspective view of the guide holding member  150  for use in the apparatus for polishing an end-surface of a ferrule according to one embodiment of the present invention. The guide block  156  is shown by broken lines for clarifying the shapes of the underlying holder blocks  152 ,  154 . Also, FIG. 4 is a plan view of the guide holding member  150  for use in the apparatus for polishing an end-surface of a ferrule according to one embodiment of the present invention. 
     As illustrated in FIGS. 3 and 4, the guide holding mechanism  150  is comprised of two holder blocks  152 ,  154  and a guide block  156 . The guide block  156  comprises a cone-shaped guiding portion  156 G. A diverging end of the guide portion  156 G is open to the upper side of the guide block  156 . A tapered end of the guiding portion  156 G is open to the lower side of the guide block  156 . The diameter of the opening at the tapered end is larger than the outer diameter of a cylinder portion at a lower end of the ferrule  20 F by approximately 0.5 mm. The holder blocks  152 ,  154  have semi-cylindrical holders  152 H,  154 H at their opposing portions, respectively. The holders  152 H,  154 H have dimensions and shapes suitable for holding the cylinder portion at the lower end of the ferrule  20 F when they are joined together. 
     As explained in FIG. 2, the holder block  152  and the guide block  156  are fixed on the Z-moving mechanism. The holder block  152  is reciprocally movable in the X-direction. The X-direction, herein referred to, is the same direction as the X-direction in FIG.  2 . 
     As illustrated in FIGS. 3 and 4, the holder block  152  and the holder block  154  are separated from each other before they hold the ferrule  20 F. In this state, the ferrule  20 F held by the cable chuck robot  50  is transferred. As the ferrule  20 F is brought downward vertically by the cable chuck robot  50 , the lower end of the ferrule comes in contact with the guiding portion  156 G of the guide block  156 , and positioned between the holders  152 H,  154 H of the guide blocks  152 ,  154 , guided by the cone-shaped guiding portion  156 G. Subsequently, as the holder block  152  moves in the direction of the arrow X 4 , the ferrule  20 F can be held. 
     Next, the operation of the ferrule positioning/holding unit  100  for use in the apparatus for polishing an end-surface of a ferrule according to this embodiment will be explained using FIGS. 2,  5  and  6 . 
     FIGS. 5 and 6 are side views for explaining the operation of the guide holding mechanism  150  for use in the apparatus for polishing an end-surface of a ferrule according to one embodiment of the present invention. 
     In the following explanation, as illustrated in FIG. 2, explanation will be given of steps of removing the ferrule  20 F held by the holder blocks  152 ,  154 , and holding a new ferrule by the holder blocks  152 ,  154 . 
     As the block extruding cylinder  130  operates from the state illustrated in FIG. 2 to move the shaft  132  in a direction of an arrow X 6 , the block retaining cylinder  170  and the shaft  172  move in the direction of the arrow X 2 . Since the spring  152 SP is suspended between the holder block  152  and the provisionally retaining block  160 , the provisionally retaining block  160  is moved in a direction of an arrow X 8  by a spring force of the spring  152 SP. Next, as the block retaining cylinder  170  operates to move the shaft  172  in the direction of the arrow Z 4 , the compressed spring  160 SP interposed between the provisionally retaining block  160  and the slider  160 S causes the provisionally retaining block  160  to move in the direction of the arrow Z 4  with a spring force of the spring  160 SP. In other words, the provisionally retaining block  160  transitions from the state illustrated in FIG. 6 to the state illustrated in FIG.  5 . 
     In this state, the ferrule  20 F is held between the holder block  152  and the holder block  154 , i.e., in a state in which the ferrule  20 F is polished by the polishing paper  32 . As described above, the Z-moving mechanism  140  is suspended down by the spring  140 SP with respect to the supporting base  112 , and the leading end of the ferrule  20 F is pressed onto the polishing paper  32  at a constant pressure expressed by ((Spring Force of Spring  140 SP)—(Own weights of Z-Moving Mechanism  140  and Guide Holding Mechanism  150 )). 
     As the end-surface at the leading end of the ferrule  20 F has been polished, the releasing cylinder  120  operates to move the shaft  122  in the direction of the arrow Z 2 . Responsively, the cam follower shaft  144  and the cam follower  142  move in the direction of the arrow Z 5 . Since the cam follower  142  follows the cam surface  152 C, the holder block  152  moves in the direction of the arrow X 5 . As a result, as illustrated in FIG. 3, the holder block  152  and the holder block  154  move away from each other, so that the ferrule  20 F is released from the holding by the holder  152 H and the holder  154 H, and is movable by the cable chuck robot  50 . 
     Next, when a new ferrule is positioned above  20 F by the cable chuck robot  50 , and the new ferrule is brought downward, its leading end is positioned between the holder  152 H and the holder  154 H as guided by the guiding portion  156 G of  156 . Next, as the releasing cylinder  120  operates to move the shaft  122  in the direction of the arrow Z 1 , the come follower  142  moves in the Z 1  direction, while in contact with the cam surface  152 C, causing the holder block  152  to move in the direction of the arrow X 5  to hold the new ferrule between the holder  152 H and the holder  154 H. FIG. 5 illustrates this state. 
     Next, as the block extruding cylinder  130  operates to move the shaft  132  in the direction of the arrow X 2 , the block retaining cylinder  170  and the shaft  172  move in the direction of the arrow X 3 . While the spring  152 SP is suspended between the holder block  152  and the provisionally retaining block  160 , the provisionally retaining block  160  moves in the direction of the arrow X 4  against the spring force of the spring  152 SP. Further, as the block retaining cylinder  170  operates to move the shaft  172  in the direction of the arrow Z 3 , the provisionally retaining block  160  moves in the direction of the arrow Z 3  against the spring force of the spring  160 SP, although the compressed spring  160 SP is interposed between the provisionally retaining block  160  and the slider  160 S. In this event,  162  at the leading end of the provisionally retaining block  160  pushes a flange of the new ferrule, causing a stepped portion  20 S of the new ferrule to run into the top surfaces of the holder blocks  152 ,  154 , as illustrated in FIG. 6, thus making it possible to position the ferrule in the Z-direction. 
     As the holding of the ferrule is complete, the block extruding cylinder  130  operates to move the shaft  132  in the direction of the arrow X 6 , causing the block retaining cylinder  170  and the shaft  172  to move in a direction of an arrow X 7 . Since the spring  152 SP is suspended between the holder block  152  and the provisionally retaining block  160 , the provisionally retaining block  160  moves in a direction of an arrow X 8  with a spring force of the spring  152 SP. Next, as the block retaining cylinder  170  operates to move the shaft  172  in the direction of the arrow Z 4 , the compressed spring  160 SP interposed between the provisionally retaining block  160  and the slider  160 S forces the provisionally retaining block  160  to move in the direction of the arrow Z 4  with a spring force of the spring  160 SP. In other words, the provisionally retaining block  160  transitions from the state illustrated in FIG. 6 to the state illustrated in FIG. 5, thereby permitting a new ferrule to be polished. 
     Next, the structure for holding polishing paper for use in the ferrule end-surface polishing apparatus according to this embodiment will be described using FIGS. 7 and 8. 
     FIG. 7 is a side view illustrating the structure for holding polishing paper for use in the ferrule end-surface polishing apparatus according to one embodiment of the present invention; FIG. 8A is a bottom view of a metal plate for holding the polishing paper for use in the ferrule end-surface polishing apparatus according to one embodiment of the present invention; and FIG. 8B is a plan view of a turntable for use in the ferrule end-surface polishing apparatus according to one embodiment of the present invention. 
     As illustrated in FIG. 7, the polishing paper  32  is securely held on the metal plate  34  by a double-faced tape or the like. The metal plate  34  and the polishing paper  32  held by the polishing paper chuck mechanism  36  illustrated in FIG. 1 is transferred to a position above the turntable  48 . Subsequently, the metal plate  34  and the polishing paper  32  are moved down in the direction of the arrow Z 5 , and placed on the turntable  48 . 
     Here, as illustrated in FIG. 8A, a positioning convex pin  34 A is provided in a central lower portion of the metal plate  34 , and a fixing convex pin  34 B is provided in a peripheral end portion of the metal plate  34 . On the other hand, as illustrated in FIG. 8B, a positioning hole  48 A is formed in a central upper portion of the turntable  34 . Also, a groove  48 B is formed in a circumferential portion of the turntable  48 . The groove  48 B is not in a closed loop, and is provided with a stopper  48 C. 
     Thus, as the metal plate  34  and the polishing paper  32  are moved down in the direction of the arrow Z 5  and placed on the turntable  48 , the positioning pin  34 A engages with the positioning hole  48 A, so that the metal plate  34  is positioned with respect to the turntable  48 . Also, the fixing convex pin  34 B engages with the groove  48 B and stopped by the stopper  48 C, thereby fixing the metal plate  34  with respect to the turntable  48 . 
     Next, the general operation of the ferrule end-surface polishing apparatus according to this embodiment will be described using FIGS. 1 and 2. 
     First, sheets of polishing paper  32  selected in accordance with polishing conditions are placed at predetermined positions of the polishing paper setting unit  30 , the optical cable  20  wound around the bobbin  22  is set on the bobbin holder  12 , and the optical cable  20  on the optical cable holder  14  by an optical cable transfer robot or a manual operation, and the operation is started by a starting switch or the like. The ferrule positioning/holding mechanism  100  positions and holds the ferrule  20 F. Next, from sheets of the polishing paper  32  in the polishing paper setting unit  30  previously set in accordance with the polishing conditions, predetermined polishing paper  32  is chucked by a movement of the polishing paper transfer robot  34  and the polishing paper chucking mechanism  36 , and set on the turntable  48  of the rotation/swing mechanism  40  located below the ferrule positioning/holding mechanism  100 . 
     Next, the ferrule positioning/holding mechanism  100  is moved down to press the ferrule  20 F with a fixed pressure, while the rotation/swing mechanism  40  operates to rotate as well as swing the turntable  48 . Following this, the plate  34 , on which the polishing paper  32  is adhered, is rotated and swung to polish for a predetermined time period. As the polishing is completed, the ferrule positioning/holding mechanism  100  is moved up, another polishing paper  32  is substituted by the polishing paper transfer robot  34  and the polishing paper chucking mechanism  36 , and the polishing is gain performed through the foregoing steps to complete a sequence of operations. 
     When an end portion of a ferrule is polished using two types of rough and fine polishing paper, the polishing is performed, for example, for two minutes by the rough polishing paper, and next, the polishing is performed for two minutes by the fine polishing paper. Both the rough polishing paper and the fine polishing paper are replaced with new sheets of polishing paper after ferrules are polished six times. 
     As described above, in this embodiment, a ferrule is guided by the guide blocks between the holder blocks, and the ferrule is held by the holder units formed on each of the two holder blocks, so that the ferrule can be automatically held. 
     Also, a holding/guiding mechanism such as the holder blocks is suspended by a spring such that the ferrule is pressed onto the polishing paper to polish the end-surface of the ferrule by a differential pressure between a spring force of this spring and the own weight of the holding/guiding mechanism, the holding/guiding mechanism is a structure completely separated from a power source in a polishing state, thereby making it possible to set a fine pressure to be applied, stabilize polishing conditions, and achieve polishing of good quality. 
     Further, the polishing paper can be automatically replaced by means of the polishing paper transfer robot and the polishing paper chucking mechanism. 
     According to the present invention, the ferrule end-surface polishing apparatus can be readily automated.