Patent Publication Number: US-6987921-B2

Title: Ferrule polishing fixture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of application Ser. No. 10/061,732, filed Feb. 1, 2002, now U.S. Pat. No. 6,718,111 which application is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates generally to the field of polishing fixtures for holding fiber optic cables during the polishing process. 
   BACKGROUND OF THE INVENTION 
   Fiber optic connectors generally include a cylindrical ferrule containing an optical fiber. A tip of the fiber is exposed at an end face of the ferrule. To enhance signal quality, it is desirable to polish the end face of ferrule. During the polishing process, the ferrule is commonly held in a fixture, and the end face is pressed against a rotating polishing wheel or disk. An example of a fixture for use in polishing fiber optic connectors is described in co-pending U.S. patent application Ser. No. 09/400,334, filed Sep. 21, 1999, which application is incorporated herein by reference. 
   SUMMARY OF THE INVENTION 
   One aspect of the present invention relates to a device for holding fiber optic connectors having ferrules containing optical fibers, the device including a clamp having a nest sized to hold a ferrule. The nest includes a moveable portion moveable between a first position where the nest is sized to receive the ferrule and a second position where the nest is sized to clamp the ferrule. The moveable portion is biased toward the second, clamped position. 
   A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrates several aspects of the invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows: 
       FIG. 1  is a top plan view of an embodiment of a fixture constructed in accordance with the principles of the present invention, the fixture is shown with nests of the fixture in the biased closed orientation; 
       FIG. 2A  is a top plan view of the fixture of  FIG. 1  in place on an actuating device with the nests in the biased closed orientation; 
       FIG. 2B  is a top plan view of the fixture of  FIG. 1  in place on an actuating device, with the nests in an open orientation; 
       FIG. 3  is a cross-sectional view taken along section line  3 — 3  of  FIG. 1 ; 
       FIG. 4  is a top plan view of an embodiment of an actuating device constructed in accordance with the principles of the present invention; 
       FIG. 5  is a top plan view of an alternative set plate; 
       FIG. 6  is a cross-sectional view taken along section line  6 — 6  of  FIG. 5 ; and 
       FIG. 7  is a top plan view of an alternative embodiment of an actuating device. 
   

   DETAILED DESCRIPTION 
   Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
   The present invention relates to a system for holding fiber optic connectors to facilitate polishing ferrules of the connectors. One representative embodiment of the invention includes a fixture  30  having a plurality of clamps for holding ferrules. The clamps are normally closed. The system also includes an actuation device  123  for opening the clamps to allow the ferrules to be inserted into or removed from the clamps. 
   In use of the system, the fixture  30  is mounted on the actuation device  123 , and the actuation device  123  is used to simultaneously open the clamps. The ferrules of the connectors desired to be polished are then inserted into the clamps. After insertion of the ferrules, the actuation device  123  releases the clamps thereby allowing the clamps to return to their normally closed orientation. In the normally closed orientation, the clamps securely hold the ferrules within the fixture. Thereafter, the fixture can be removed from the actuating device and mounted on a polishing device (e.g., a polishing wheel including a polishing film mounted on a polishing pad, as is conventionally known in the art). After the ferrules have been polished, the fixture  30  is returned to the actuation device  123 , and the clamps are opened to allow removal of the polished ferrules. 
   I. Fixture 
     FIGS. 1 ,  2 A and  2 B show an embodiment of a fixture  30  constructed in accordance with the principles of the present invention. The fixture  30  includes a holding plate  32  defining a central opening  40  and having a plurality of nests  34 . An advantage of the fixture  30  is that it is an integral structure, cut from a single piece of material, and does not involve removable parts. Each nest  34  defines an opening  36  sized for receiving a ferrule of a fiber optic connector. The openings  36  extend completely through the plate  32  between upper and lower surfaces/sides  142  and  144  (shown in  FIG. 3 ) of the holding plate  32 . The nests  34  are circumferentially spaced about a reference axis  38  positioned at the center of the holding plate  32  (i.e., the nests  34  are arranged in a circular array). 
   Each nest  34  includes a moveable portion  42  moveable between a first, open position where the nest is sized to receive the ferrule (shown in  FIG. 2B ) and a second, closed position where the nest is sized to clamp the ferrule (shown in FIG.  2 A). The moveable portion  42  is biased towards the second, closed position. The moveable portion  42  can be in the form of a flexible, cantilevered portion moveable between a rest position in which the nest is clamped, and a flexed position in which the nest is open. 
   The nests  34  are opened by applying a displacement force on the moveable portion  42  in the direction indicated by the arrows in FIG.  1 . The displacement force can be provided by any actuating device. One embodiment of an actuator is described in detail below. In one embodiment, the moveable portions  42  have free end portions  54  that extend into the central opening  40  for receiving the displacement force. While  FIGS. 1 ,  2 A and  2 B show twelve nests  34  in a fixture  30 , the fixture  30  can contain a single nest  34  or any number of nests  34 . 
   In the embodiment shown in  FIGS. 1 ,  2 A and  2 B, the holding plate  32  includes a plurality of fixed portions  44  and a plurality of moveable portions  42  forming a plurality of nests  34 . The fixed portions  44  oppose the moveable portions  42 . In one embodiment, free end portions  54  of the moveable portions  42  extend beyond the fixed portions  44 . First half-portions  60  of the nests  34  are formed by the fixed portions  44  and second half-portions  62  of the nests  34  are formed by the moveable portions  42  of the holding plate  32 . Moveable portions  42  are formed by first and second slots  46 ,  48  cut from the central opening  40  and extending radially outwardly. The first slot  46  extends through the opening  36  of the nest  34 . The second slot  48  is offset from the first slot  46  to form the cantilevered moveable portion  42 . The cantilevered moveable portion  42  joins the fixed portion  44  at a flexing point  45 . The moveable portions  42  are moveable relative to the fixed portions  44 . For example, each of the moveable portions  42  is moveable between an at rest position (shown in  FIG. 2A ) and a circumferentially displaced, or flexed, position (shown in FIG.  2 B). 
   When the nests  34  are in the at rest, or clamped position, the first and second half-portions ( 60 ,  62 ) of the nest  34  are sufficiently close together to clamp a ferrule. When a displacement force moves the moveable portion  42  away from the fixed portion  44 , the second slot  48  narrows and the first slot  46  widens, thus opening the nest  34 . 
   The moveable portions  42  are biased toward the at rest positions of  FIG. 2A  by inherent spring-like characteristics (i.e., elasticity or resiliency) of the material forming the moveable portions  42 . In one embodiment, the fixture  30  including the moveable portions  42  are made of stainless steel. Preferably, the moveable portions  42  are displaced circumferentially in a flexing motion. When the displacement force is removed, internal spring-like characteristics bias the moveable portions  42  toward the at rest positions. 
   By way of non-limiting example, the holding plate  32  can be made of heat treated steel. Also by way of non-limiting example, the plate  32  can have a thickness of about 0.21 inches, a height of about 4.725 inches and a width of 4.725 inches; the first and second slots  46 ,  48  can have thicknesses of about 0.0025 inches and 0.014 inches, respectively; and the nest openings  36  can have an open position diameter of about 0.099 inches. 
   To enhance gripping when the nests  34  are in the clamped positions, the nests  34  can each include one or more bumps, projections, or irregularities (not shown) that extend radially into the openings  36 . Also, to accommodate various connector configurations, depressions  50  are provided about the nests  34  in the upper side  142  of the holding plate  32 . The depressions  50  are sized to receive portions of certain styles of connector housings (e.g., SC type connectors). 
   II. Actuator 
     FIG. 4  shows one embodiment of an actuator device  123  constructed in accordance with the principles of the present invention. The actuator device  123  has an integral set plate  121 . The set plate  121  includes seating surfaces  124 , an inset ring  125  with at least one alignment surface  127 , and a circular array of openings  126 . The inset ring  125  can be a separate piece, or it can be a region of the set plate  121 . The set plate  121  also includes a plurality of fixture pins  128  that align with corresponding alignment apertures  56  in the holding plate  32 . 
     FIGS. 5 and 6  show an alternative embodiment of a set plate  121 ′ with the alignment surface  127 ′ of the inset ring  125 ′ divided into regions of differing elevations to provide a variety of offset distances from the seating surfaces  124 ′ to accommodate various protrusion requirements for different ferrule sizes. Regions  180  of the alignment surface  127 ′ without openings  126 ′ accommodate ferrules without fibers. 
   The openings  126 ,  126 ′ are positioned to align with the nests  34  of the holding plate  32  when the fixture  30  is mounted over the set plate  121 ,  121 ′. The openings  126 ,  126 ′ are preferably smaller that the end faces of the ferrules desired to be polished, but larger than the fibers positioned within the ferrules. The openings  126  can all be the same size as shown in  FIG. 4 , or a plurality of different size openings  126 ′,  170  can be present on a single inset ring  125 ′, as shown in FIG.  5 . The larger openings can be used for larger ferrules to receive the larger amount of epoxy residue that sometimes surrounds the fiber at the end faces of such ferrules. A set plate  121 ′ with an inset ring  125 ′ containing both different elevation regions and different sizes of openings  126 ′,  170  reduces the number of set plates required to provide different ferrule offset lengths as may be required by different polishing processes. Typically, only surfaces of the same elevation are used to set the elevation of a given batch of ferrules. 
   The actuator device  123  includes a disk-shaped rotatable drive  132  that projects upward through a central opening  134  defined by the set plate  121 . The rotatable drive  132  includes a plurality of posts  52  around the outer circumference. When a fixture  30  is placed on the set plate  121 , as shown in  FIG. 2A , the posts  52  are positioned between free end portions  54  of moveable portions  42  of nests  34 . 
   A lever arm  140  including an L-shaped handle  150  is mechanically coupled to the rotatable drive  132 . By pivoting the lever arm  140  outward and inward, the rotatable drive  132  with posts  52  is rotated in clockwise and counterclockwise directions, respectively. In one embodiment, the posts  52  are rotated about 5-15 degrees in each direction. 
   As show in  FIG. 4 , the lever arm  140  is coupled to the rotatable drive  132  by a linkage. The lever arm  140  is linked to the frame of the actuator device  123  at a first pivot point  154 , and to an intermediate link  152  at a second pivot point  156 . The intermediate link  152  is linked to a drive link  160  at a third pivot point  158 . The drive link  160  is fixedly connected to the rotatable drive  132 . 
   When the lever arm  140  is pivoted outward, as shown in dotted lines in  FIG. 4 , the rotation drive  132  and posts  52  are positioned away from the moveable portions  42  of a fixture  30  present on the actuator device  123 . Pivoting the lever arm  140  inwards, as shown in solid lines in  FIG. 4 , rotates the rotatable drive  132  counterclockwise, forcing the posts  52  against the moveable portions  42 , which opens the nests  34 . 
   III. Methods of Use 
   In use, the fixture  30  is positioned over the set plate  121  of the actuator device  123  with the lever arm  140  pivoted outward. The fixture pins  128  of the set plate  121  are aligned with the alignment apertures  56  of the fixture  30 . The nests  34  are in the biased clamped position as shown in FIG.  2 A. The lever arm  140  is pivoted inward causing the rotatable drive  132  to rotate. As the rotatable drive  132  rotates, torque from the rotatable drive  132  is transferred to the moveable portions  42  of the fixture  30  through the posts  52 . The torque from the rotatable drive  132  causes the moveable portions  42  to move, or flex, from the biased closed position of  FIG. 2A  to the open position of FIG.  2 B. This movement of the moveable portions  42  causes the nests to move to the open positions. The fixture pins  128  prevent the holding plate  32  from rotating along with the moveable portion  42 . 
   Ferrules of fiber optic connectors are individually inserted downwardly from the upper side  142  of the holding plate  32  into the openings  36  of the nests  34 . The ferrules are pushed downwardly through the openings  36  until end faces of the ferrules protrude beyond the lower side  144  of the holding plate  32  and are seated upon the alignment surface  127  of the inset ring  125 , and the optical fibers and epoxy residue extend into openings  126  in the inset ring  125 . This ensures that all of the ferrule end faces are aligned along a common plane. 
   With all the ferrule end faces seated on the alignment surface  127  of the inset ring  125 , the lever arm  140  is pivoted outward causing the posts  52  to move away from the moveable portions  42 . This allows the moveable portions  42  return to the rest, biased closed, position of  FIG. 2A  such that the ferrules are firmly clamped within the nests  34  to inhibit relative movement thereinbetween. 
   With the ferrules clamped in the fixture  30 , the fixture  30  is removed from the set plate  121  and transferred to a polishing wheel (not shown) where the end faces of the ferrules are polished. The one-piece fixture  30  provides the advantage of having the nests  34  in the clamped position without requiring any external force or added locking mechanisms. With no additional moving parts or locking mechanisms, the one-piece fixture is easy to manipulate and clean. 
   After polishing, the fixture  30  is once again placed on the set plate  121 , the lever arm  140  is pivoted inward causing the posts  52  to move the moveable portions  42  to the open, flexed position of  FIG. 2B , opening the nests  34  so the polished ferrules can be removed from the fixture  30 . Thereafter, the process can be repeated on a subsequent batch of fiber optic connectors. 
   IV. Alternative Actuator 
     FIG. 7  shows an alternative embodiment of actuator device  223 . This embodiment includes features for insuring uniform protrusion of ferrules from a polishing fixture. The actuator device  223  includes a set plate  221 , swing clamps  310 , a rotatable drive  232  and a lever arm  240 . The set plate  221  has seating surfaces  224  and an alignment surface  227 . A plurality of spring plungers  320  are embedded in the seating surfaces  224 . The set plate also includes a plurality of fixture pins  228  that match alignment apertures  56  in a fixture  30  to prevent rotation of the fixture  30  during the clamping and setting process. 
   The spring plungers  320  are moveable between a first, at rest, position in which they extend above the seating surfaces  224 , and a second, retracted, position in which they are substantially flush with the seating surfaces  224 . Swing clamps  310  extend above the seating surfaces  224  and include clamp arms  315 . The clamp arms  315  are rotatable toward the set plate  221  to clamp a fixture  30  placed onto the set plate  221 . The clamp arms  315  are also moveable in a downward direction, toward the seating surfaces  224 . The clamp arms  315  may be activated in any manner, such as pneumatically. 
   The alignment surface  227  has a plurality of openings  226  positioned to align with nests  34  of a holding plate  32  when the fixture  30  is mounted over the set plate  221 . The actuator device  223  includes a disk-shaped rotatable drive  232  that projects upward through a central opening  234  defined by the set plate  221 . The rotatable drive  232  includes a plurality of posts  252  around the outer circumference. 
   A lever arm  240  including an L-shaped handle  250  is mechanically coupled to the rotatable drive  232 . By pivoting the lever arm  240  outward and inward, the rotatable drive  232  with posts  252  is rotated in clockwise and counterclockwise directions, respectively. The lever arm  240  is coupled to the rotatable drive  232  by a linkage. The lever arm  240  is linked to the frame of the actuator device  223  at a first pivot point  254 , and to an intermediate link  252  at a second pivot point  256 . The intermediate link  252  is linked to a drive link  260  at a third pivot point  258 . The drive link  260  is fixedly connected to the rotatable drive  232 . 
   In use, an empty fixture  30  is positioned on set plate  221  with fixture pins  228  aligned with the alignment apertures  56  of the fixture  30 . The fixture  30  rests on spring plungers  320  above seating surfaces  224 . The lever arm  240  is pivoted to rotate the rotatable drive  232  and posts  252 , causing the nests  34  to move to the open positions. Ferrules of fiber optic connectors are individually inserted into the openings  36  of the nests  34 . The ferrules are pushed downwardly through the openings  36  until end faces of the ferrules are seated upon the alignment surface  227  and the optical fibers extend into openings  226  in the set plate  221 . With all the ferrule end faces seated on the alignment surface  227 , the lever arm  240  is pivoted outward, causing the nests  34  to close. 
   Once the ferrules are clamped in the nests  34 , the swing clamps are activated. The clamp arms  315  rotate over and above the fixture  30 , and then descend toward the seating surfaces  224 . As the clamp arms  315  exert a downward force, the spring plungers  320  retract and the fixture  30  is made to contact the seating surfaces  224 . The combined force of the swing clamps  310  must be sufficient to overcome the combined resistance of the spring plungers  320  and the clamped ferrules. The fixture is pre-staged by inserting and clamping the ferrules while the fixture  30  is above the seating surface  224  on the spring plungers  320 . This assures that once the fixture is drawn snugly against the seating surface  224 , any ferrules not fully inserted will still end up with identical protrusion dimensions as those fully inserted. 
   The fixture  30  is then removed from the set plate  221  and transferred to a polishing wheel (not shown) where the end faces of the ferrules are polished. After polishing, the fixture  30  is once again placed on the set plate  221 , the lever arm  240  is pivoted inward, opening the nests  34  so the polished ferrules can be removed from the fixture  30 . Thereafter, the process can be repeated on a subsequent batch of fiber optic connectors. 
   Having described preferred aspects and embodiments of the present invention, modifications and equivalents of the disclosed concepts may readily occur to one skilled in the art. For example, while the nests illustrated herein are configured to hold ferrules in a vertically upright orientation, it will be appreciated that the nests could also be oriented so as to each hold a ferrule at an oblique angle relative to a polishing surface. However, it is intended that such modifications and equivalents be included within the scope of the claims that are appended hereto.