Patent Abstract:
Multi-fiber ferrules may be produced with tapered bodies and guide pin holes that have fluted internal surfaces with projections for engaging the guide pins, and channels for capturing any foreign material that may accumulate on or around the guide pins, thereby providing improved consistency in fiber connections during mating of the ferrules.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/276,999 filed May 13, 2014, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Optical ferrules which are standardized according to JIS C 5981, IEC 61754-5 and the like, are called MT (Mechanically Transferable) ferrules, and are used for connecting optical fibers. MT ferrules generally use at least two guide pins for high-accuracy positioning of each optical fiber in the ferrule. An MT ferrule body may include two guide pin holes on the end surface of the ferrule for receiving the guide pins therein, and may have a plurality of optical fiber holes for receiving the optical fibers. The respective optical fibers may be inserted into the optical fiber insertion holes from a rear end of the MT ferrule, and may be fixed in place with adhesive. 
     An adapter may be used for face-to face joining of two MT ferrules. MT ferrules generally have a rectangular cross-sectional shape, and likewise, the adapter may be in the shape of a rectangular cylinder for insertion of one ferrule into each end. Two MT ferrules, one with guide pins installed (male connector) and one without guide pins (female connector) are inserted into opposite ends of the adapter whereby the ferrules are aligned together with one another as the male guide pins enter the female guide pin holes. One type of connector that uses MT ferrules is an MPO (multi-fiber push-on) connector 
     The MT ferrules get pushed together within the adapter to optically connect the ferrules by means of a so-called PC (Physical Contact) connection, wherein the optical fibers in one ferrule contact the optical fibers in the other ferrule and get compressed together to provide an optical connection. Optical transmission performance between the optical fibers is strongly dependent on connecting conditions such as axis alignment and inclination of the optical fibers, and gaps between the opposing optical fibers. 
     To prevent gaps during connection, it is necessary to remove foreign materials that may be adhered to the connection end face of the MT ferrule. Any foreign materials are commonly wiped off by use of a cleaner. However, connection loss at the PC connection may be increased during wiping off, because some of the foreign materials may be gathered and deposited around base portions of the guide pins. In general, any foreign materials that may be present on the end face or components of the end face may interfere with the connection by causing the faces to be spaced apart from one another, resulting in gaps between the optical fibers. 
     In addition, in installations wherein the adapter is fixedly mounted in a panel, for example, the angular orientation of the ferrule as it is retrieved, aligned, and inserted may stress the optical fibers, and possibly result in breakage of a fiber or fibers if considerable care is not taken when the ferrule is inserted into the adapter. 
     Therefore, during the mating of MT ferrules, there remains a need for minimization of issues that may result in poor fiber mating connections, such as contamination on the end faces of the MT/MPO ferrules, and the possibility of fibers breaking when the MPO connector is inserted into an MPO adapter in a rough or incorrect manner. 
     SUMMARY 
     Modifications of the MT ferrules may provide for better fiber connections during mating of the ferrules. To reduce the accumulation of contaminants on or between faces of mating ferrules, channels may be provided within the guide pin holes for debris accumulation. In addition, to reduce the possibility of breaking fibers while inserting a ferrule into an adapter, the ferrule body may be provided with a tapered design to allow for some initial play and leeway during the initial stage of the insertion into the adapter. 
     In an embodiment an optical fiber connector is disclosed. The connector is configured for being coupled with an adapter to mate with another optical fiber connector, and the connector includes a housing having a first end for being coupled with the adapter, and a ferrule floatably mounted in the housing. The housing defines a first longitudinal passage therethrough, with the first longitudinal passage defining a first longitudinal axis. The ferrule is floatably mounted at the first housing end within the first longitudinal passage for relative movement between the ferrule and the housing, and the ferrule includes a first end protruding forward of the first housing end, and a second end spaced from the first end and disposed within the first longitudinal passage, the ferrule defining a second longitudinal axis extending from the first end to the second end, and the first end includes an end face for mating with an end face of an additional ferrule. The ferrule includes at least first and second alignment pin holes in the end face configured for receiving an alignment pin therein, wherein each of the first and second alignment pin holes have a longitudinal direction parallel with the second longitudinal axis, and each pin hole defines an interior surface comprising a plurality of spaced apart longitudinal grooves extending from the end face and into the ferrule. The ferrule also includes at least one side wall having a first wall end at the end face and extending from the end face to a second wall end adjacent the second end of the ferrule, with the at least one side wall tapering outwardly away from the second longitudinal axis in a direction from the end face towards the second end so that the ferrule is tiltable within the housing passage to offset the second longitudinal axis with respect to the first longitudinal axis. 
     In an embodiment, an optical ferrule includes a housing that includes a first end, a second end spaced from the first end, and a longitudinal axis extending from the first end to the second end, wherein the first end comprises an end face for mating with an end face of an additional optical ferrule. The housing also includes at least one passage extending through the housing and configured for receiving at least one optical fiber therein for termination of the at least one optical fiber at the end face, and at least one side wall extending from the end face towards the second end, the at least one side wall tapering outwardly away from the longitudinal axis in a direction from the second end to the first end. 
     In an embodiment, an optical ferrule includes a housing that includes a first end, a second end spaced from the first end, and a longitudinal axis extending from the first end to the second end, wherein the first end comprises an end face for mating with an end face of an additional optical ferrule. The housing also includes at least one passage extending through the housing and configured for receiving at least one optical fiber therein for termination of the at least one optical fiber at the end face, and at least first and second alignment pin holes in the end face configured for receiving an alignment pin therein, each of the first and second alignment pin holes having a longitudinal direction parallel with the longitudinal axis, and defining an interior surface comprising a plurality of spaced apart longitudinal grooves extending from the end face and into the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS. 1A and 1B  depict a tapered ferrule body with modified guide pin holes according to an embodiment. 
         FIGS. 2A and 2B  depict a non-tapered ferrule body with modified guide pin holes according to an embodiment. 
         FIGS. 3, 3A, 3B and 3C  depict various views of the ferrule of  FIGS. 1A and 1B  according to an embodiment. 
         FIGS. 4, 4A, 4B and 4C  depict various views of the ferrule of  FIGS. 2A and 2B  according to an embodiment. 
         FIG. 5  provides a representative illustration of the mating of two ferrules having non-tapered bodies according to an embodiment. 
         FIG. 6  provides a mated depiction of two tapered body ferrules according to an embodiment. 
         FIGS. 7A and 7B  provide a top view of a mated connection of tapered-body ferrules according to an embodiment. 
         FIGS. 8A and 8B  provide a side view of a mated connection of tapered-body ferrules according to an embodiment. 
         FIG. 8C  provides a representative illustration of engagement surfaces of a flange and housing shoulder according to an embodiment. 
         FIGS. 9A and 9B  provide a top view of a representative illustration of the angular insertion variability provided by a tapered ferrule body according to an embodiment. 
         FIGS. 10A and 10B  provide a side view of a representative illustration of the angular insertion variability provided by a tapered ferrule body according to an embodiment. 
         FIGS. 11A and 11B  provide a comparative illustration of the insertion rigidity provided by a non-tapered ferrule body. 
         FIGS. 12A and 12B  provide end views along line X of  FIG. 5  of mated ferrule bodies according to an embodiment. 
         FIGS. 13A, 13B and 13C  provide a detailed cross-sectional view of the mating of two ferrule bodies and the avoidance of contaminant blockage according to an embodiment. 
         FIG. 14  depicts an alternative configuration for the guide pin holes according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     While the following description is directed towards MT optical ferrules, the embodiments described may be applicable to other ferrule types as well. As represented in the embodiments of  FIGS. 1A, 1B, 2A and 2B , a ferrule may have a main body  110  or  210  that defines a front, insertion end  112  or  212 , that may be inserted into an adaptor  9  (shown in outline in  FIG. 5 ), as well as a rear end  114  or  214 . The rear end may typically be engaged in or with a fiber optic connector housing (not shown). In an embodiment as represented in  FIGS. 1A and 1B , the ferrule body  110  may be a tapered-body, as shown in greater detail in  FIGS. 3, 3A, 3B and 3C , and may have a frusto-pyramidal shape, or define a rectangular frustum. In an alternative embodiment, as represented in  FIGS. 2A and 2B , the ferrule body  210  may be cuboid with essentially parallel opposing faces, as shown in greater detail in  FIGS. 4, 4A, 4B and 4C . 
     The rear end  114  or  214  may include an opening  11  configured for receiving an end of a multi-fiber optical cable  13 , that may be, for example, a ribbon cable of a plurality of individual optical fibers  15 . The front end  112  or  212  may have a connection end face  116  or  216  that may include a plurality of optical fiber insertion holes  17  arranged in at least one row, or as shown, two rows. Individual ones of the optical fibers  15  of the multi-fiber cable  13  may be disposed in the holes  17  to terminate at the connection end face  116 ,  216 . 
     In an embodiment, the front end  112 ,  212  of the ferrule body  110 ,  210  may be formed to have a rectangular cross-sectional shape. The rear end  114 ,  214  of the ferrule main body  110 ,  210  may be provided with a flange  19 . The optical fibers  15  may be inserted, via the opening  11 , through the flange  19 , and into the optical fiber insertion holes  17 . A top face  118 ,  218  of the insertion end  112 ,  212  may include an access opening  21  for guiding the optical fibers  15  into the holes  17 . The optical fibers  15  may be fixed in place by use of an adhesive that may be injected into the ferrule body  110 ,  210  via the access opening  21  and/or the cable opening  11 . 
     Guide pin insertion holes  25 , described in greater detail below, may be provided through the body  110 ,  210 , extending from the connection end face  116 ,  216  out through the rear end  114 ,  214 . In an alternative embodiment, guide pin insertion holes  25  may be configured only at the front ends  112 ,  212 . Guide pins, such as guide pins  27  shown in  FIG. 5 , may be inserted into the guide pin holes  25  for precise alignment of a pair of ferrules as shown in  FIGS. 5 and 6 . 
       FIG. 3  shows a top plan view of the tapered-body ferrule  110 , and  FIG. 3A  shows a side view. In an embodiment, a ferrule  110  may have at least one side wall having a first wall end at the connection face  116  and extending from the connection face to a second wall end adjacent the rear end  114  of the ferrule. The at least one side wall may taper outwardly away from a longitudinal axis of the ferrule in a direction from the connection face  116  towards the rear end  114 . 
     In an embodiment, the at least one side wall may include a top face  118 , bottom face  120 , and side faces  122 , and the faces may each taper outwardly in a direction from the connection face  116  towards the rear end  114 . The use of ‘top’, ‘bottom’ and ‘side’ are provided for reference only and are relative to the figures, wherein the figures could have essentially been drawn with any orientation showing any of the faces  118 ,  120  or  122  as the ‘top’ for example. As depicted, faces  118  and  120  are opposite one another, and faces  122  are opposite one another and orthogonal to faces  118  and  120 . 
     The flange  19  extends laterally away from the top face  118 , bottom face  120 , and side faces  122 . A reference line  130  orthogonal to the flange  19  is also shown. In an embodiment, as shown, the side faces  122  may be disposed at an angle α from the orthogonal, and the top face  118  and bottom face  120  may be disposed at an angle β. In an embodiment, the angles α and β may be the same. In various embodiments, the angles α and β may have a value of about 1°, about 1.5°, about 2°, about 2.5°, about 3°, about 3.5°, about 4°, about 4.5°, and about 5°, and any value between any of the listed values. In an embodiment as represented by  FIGS. 3 and 3A , the angles α and β may be about 3°. The amount of angular taper may be limited essentially only by design. For example, it may be desirable for the tapered sides to remain external to the guide pin holes  25 . 
     In alternative embodiments, the angles α and β may be different from one another, or in further embodiments, each of the side faces  122  may be disposed at different angles α, and the top face  118  and bottom face  120  may be disposed at different angles β. Due to the angular taper, the cross-sectional area of the ferrule body at the connection face  116  is less than a second cross-sectional area adjacent the flange  19 , and the flange has a third cross-sectional area that is greater than the second cross-sectional area. 
       FIGS. 7A, 7B, 8A, and 8B , provide a representation of a panel structure  300  with mated ferrules  110   a ,  110   b . Each of the ferrules  110   a ,  110   b  may be a component of an optical fiber connector assembly  302   a ,  302   b  with some parts represented schematically. An adaptor  9 , as also represented in  FIG. 5 , may be mounted with the panel  300  and may be configured for receiving the connector assemblies  302   a ,  302   b , via opposing openings  9   a  and  9   b , into a longitudinal passage  9   c . The adaptor  9  may define a first longitudinal axis  9   d.    
     Each of the connector assemblies  302   a ,  302   b  may include a housing  304  that define an internal passage  305 , and a second longitudinal axis  305   d . The first longitudinal axis  9   d  and the second longitudinal axis  305   d  may generally be parallel when no external lateral forces are applied to a connector assembly  302   a ,  302   b . The ferrules  110   a ,  110   b  may be configured so that the front ends  112   a ,  112   b  extend out of connector assemblies  302   a ,  302   b  for mating of the connection end faces. Guide pins  27  may be provided as components of a pin block  308  that may be inserted through guide pin holes  25  through the back end  114  of a ferrule body to extend forwardly of the connection end face  116  to enter into guide pin holes  25  of the opposing mating ferrule body. 
     A biasing force for maintaining the ferrule  110   a ,  110   b  in engagement with one another may be provided by a biasing member, such as a spring  310  and spring retainer  312 . The spring  310  may be compressed between the pin block  308  and the spring retainer  312  to bias the pin block away from the retainer and forwardly through the connector housing  304  for engagement with the opposing ferrule. The ferrules  110   a ,  110   b  may be retained within the connector housings  304  by configuring the flange  19  to have a dimension that is greater than an internal dimension defined between the shoulders  320 . The flange  19  may be biased into engagement with the shoulder  320 . Similarly, the housing  304  may be retained within the adaptor  9  by providing an engagement projection  322  on the exterior of the housing and an engagement shoulder  324  internally within the adaptor so that the engagement projections define an external dimension that is greater than an internal dimension defined between the engagement shoulders  324 . 
     With an embodiment as shown and described, the tapered body ferrules  110   a ,  110   b , are configured as ‘floating’ ferrules and may be floatably mounted within their respective housings  304 , wherein the ferrule and housing are movable relative to one another, so that the ferrule may tilt through a conical range of movement within the housing. In an embodiment as illustrated in  FIG. 7B , housing  304  may be displaced laterally relative to the ferrule  110   b  so that the longitudinal axis  305   d  moves through an angle of about θ 1  with respect to the longitudinal axis  9   d . In an embodiment, the angle θ 1  may be an amount approximately the same as the previously described angle α. 
     Application of a lateral force F, for example, may therefore cause the housing  304  to mover relative to the mated ferrules, thereby reducing possible breakage of a connector  302   a ,  302   b , and allowing for the mated connection surfaces to remain aligned and mated within the adaptor  9 . In an embodiment, a stop  330  may be provided to prohibit movement beyond the maximum displacement angle θ 1 , thereby reducing potential damage to a ferrule. A multifiber connector  302  may be designed such that the clearances between the inner sidewalls  305  of the connector housing  304  and the tapered ferrule sides are increased in a manner which maintains the alignment of the ferrule relative to the connector housing, while at the same time permitting the ferrule to freely float within the connector housing as lateral forces are applied to the multifiber connector, thereby maintaining low optical attenuation as lateral forces are applied. In particular, it has been determined that the clearance between the inner sidewalls of the connector housing and the forward end of the ferrule are particularly critical to the freedom with which a ferrule floats within the connector housing as the multifiber connector is subjected to lateral forces. In an additional embodiment, not shown, the side walls  305  may also taper outwardly from the shoulder  320  towards the front end  306  to provide additional relative angular movement between the housing  304  and the ferrule  110 . 
       FIGS. 8A and 8B  provide a similar depiction to the illustrations of  FIGS. 7A and 7B  except from a side view of the mated ferrules  110   a ,  110   b . In a similar manner as discussed, the connector housing  304  may move up and down relative to the ferrule through an angle θ 2 . In an embodiment, the angle θ 2  may be an amount approximately the same as the previously described angle β. 
     As represented in  FIG. 8C , in an alternative embodiment of the engagement surfaces of flange  19  and shoulder  320 , one or both of the surfaces  19   a  of the flange and surface  320   a  of the housing shoulder, may be angled. As such, under the bias applied by the spring  310  the ferrule  110  may self-center within the internal passage of the housing. For comparison,  FIG. 7B  depicts an embodiment having squared shoulders for the engagement surfaces of flange  19  and shoulder  320 , and  FIG. 8B  depicts an embodiment having an angled surface for the engagement surfaces of flange  19  and a squared shoulder  320 . 
     In an alternative embodiment, as represented in  FIGS. 9A and 10A , by providing the body  110  with tapered faces, a degree of angular freedom may be provided during insertion of the ferrule into an adaptor  9 .  FIG. 9A  shows a representative top/bottom view of a ferrule body  110  after a partial insertion into an adaptor  9 , while  FIG. 10A  shows a representative side view. The representations of  FIGS. 9A and 10A  are provided as examples only, to illustrate an approximation of the angular leeway during an insertion, and other variants and configurations may also be provided. In comparison,  FIG. 11  depicts the insertion of the ferrule body  210  (rectangular-cuboid or non-tapered, insertion end) into an adaptor  9 . 
     Prior to insertion of a ferrule into an adaptor, with no obstacles near the opening of the adaptor, there might be essentially angular freedom of movement within approximately hemispherical confines as the ferrule is brought into the vicinity of the adaptor. However, as shown in  FIG. 11 , after a partial insertion of the cuboid housing  210  into the adaptor  9 , there is essentially no remaining angular freedom of movement for the ferrule body within the adaptor, thus requiring there to be essentially completely unrestricted access directly in front of the adaptor  9  for a straight-in insertion. If a forced bending is required during insertion, strain may be applied to the other components of an MPO connector containing the MT ferrule, and damage, or a reduction in the quality of the connection, may result. For example, the MPO fibers may break if the MPO connector is forcibly bent for insertion into the adaptor  9 . 
     As shown in  FIGS. 9A and 10A , however, if the insertion end  112  is tapered, the ferrule may still be movable side-to side ( FIG. 9A ) within an angular displacement of about θ 1  and may still also movable up-and-down ( FIG. 9B ) within an angular displacement of about θ 2 . The values for θ 1  and θ 2  may be the same, or may be different. The extent of θ 1  and θ 2  may vary based on the taper angle of the sides, as well as the internal configuration within the opening of the adaptor  9 . For example, in an embodiment as shown in  FIGS. 9A and 10A , portion  140   a  and  141   a , and portions  142   a  and  143   a  of the internal guide walls adjacent the opening may be parallel to provide a larger internal cavity adjacent the opening at least for about one-half of the insertion length. The remaining portion of the guide walls  140   b  and  141   b , and portions  142   b  and  143   b  may be tapered to provide alignment of the ferrule body  110  into its final seated position (shown in  FIGS. 9B and 10B ). Other internal configurations may also be provided. 
     In an embodiment as depicted in  FIG. 6 , ferrule housings  110  with tapered bodies may include cylindrical guide pin holes  25 . To provide for an improved face-to-face connection of connection surfaces  116 ,  216 , (as shown for example in  FIGS. 6 and 13C ), the connection surfaces should be free of foreign material that may inhibit contact between the surfaces and the optical fibers terminated therein. One area in which an accumulation of foreign material may result is at the base of the guide pins  27  (see for example  60 - 1  in  FIG. 13A ). For example, the foreign material may accumulate here in the formed ‘corner’ when the connection surface is wiped. Also, In order to attain precise alignment of ferrules, very little tolerance is provided between the external diameter of the guide pins  27  and the internal diameter of the guide pin holes  25 . As such, if any foreign debris is present on the guide pin  27  the debris may be pushed along the pin as the pin is inserted into the pin hole  25  so that the debris remains as an accumulation at the base of the pin on the surface  116 ,  216 . This accumulation may prevent proper contact between adjoining contact surfaces and thereby result in a poor transmission between ferrules. 
     One manner in which to inhibit an accumulation of foreign material at the base of the pins  27  from being a hindrance to good surface contact between surfaces  116 , or surfaces  216  may include providing a fluted internal surfaces within the pin holes  25 , or providing a plurality of longitudinal grooves along the internal surface of the pin holes. In an embodiment as shown in  FIGS. 3B, 3C, 4B and 4D , for example, and enlarged detail in  FIG. 12 , guide pin holes  25  may include at least three raised ridges  50 - 1 ,  50 - 2  and  50 - 3 , offset circumferentially from one another at about 120°, and having a radially inward surface for contacting the guide pin  27 . In addition, between the ridges  50 - 1 ,  50 - 2  and  50 - 3  there may be provided intervening grooves  52 - 1 ,  52 - 2  and  52 - 3 , offset circumferentially from one another at about 120°. A cross-sectional view taken through a guide pin hole  25  is represented in  FIG. 4A . 
     As represented in  FIG. 5 , and shown in detail in  FIG. 12B , the configuration of ridges and grooves in one ferrule housing  210 A may be arranged in opposition to the configuration of ridges and grooves in the abutting ferrule housing  210 B so that the ridges of one housing align with the grooves of the other housing. This is represented by the end view shown in  FIG. 12B , taken in a direction of arrow X in  FIG. 5 , wherein the ridges  50 - 1 B,  50 - 2 B and  50 - 3 B of the housing  210 B are visible at the ends of the grooves  52 - 1 A,  52 - 2 A and  52 - 3 A of the housing  210 A. The circumferential (angular) length of the ridges  50 - 1 ,  50 - 2  and  50 - 3  may be at most about 60°, and the circumferential (angular) length of the grooves  52 - 1 ,  52 - 2  and  52 - 3 , may be at least about 60°. In an embodiment, the angular length of the grooves should be greater than the angular length of the ridges so that when mated the ridges of one ferrule do not overlap with the ridges of the mating ferrule at the edges of the ridges. 
     Since it may be common with some ferrules, as shown in  FIG. 5 , to connect ferrules by inverting one ferrule housing  210 A of one cable connector in relation to the other ferrule housing  210 B to which it is to be connected, a configuration of ridges and grooves, such as is illustrated in  FIGS. 4B, 4C and 5  may provide for such an opposition alignment. Referring to  FIG. 4B , for example, guide pin holes  25  may each have a groove  52  disposed upwardly, and therefore, when inverted, an additional housing will have the same groove disposed downwardly. 
     With such a fluted configuration of guide pin holes  25 , any accumulated foreign material that occurs on the connection surface  216  at the base of a guide pin  27  will thereby end up, when adjoining an adjacent ferrule, in a groove  52  of the guide pin hole of the adjacent ferrule. This is represented in  FIGS. 13A-13C , depicting a connection of ferrules by means of an alignment guide pin  27 . In the depiction as shown, ferrule housing  210 A has a groove  52 A at the top and a ridge  50 A at the bottom, while the inverted ferule housing  210 B has a ridge  50 B at the top and a groove  52 B at the bottom. Guide pin  27 , previously inserted into housing  210 A, as shown in  FIG. 13A , has foreign material particles  60  on the surface, with an accumulation of particles  60 - 1  on the connection surface  216 A at the base of the pin  27 . 
     As represented in  FIG. 13B , as the housing  210 B is inserted onto the guide pin  27 , the upper ridge  50 B of the guide pin holes pushes the foreign material particles  60 - 2  along the guide pin in a direction to the left in the figure toward the opposite housing  210 A, while any foreign material  60 - 3 , on the bottom side remains in place within the lower groove  52 B. When connection surfaces  216 A and  216 B abut, particles  60 - 2  are pushed into the opposing groove  52 A, while the particles  60 - 1  likewise enter into an opposing groove  52 B, thereby allowing for the surfaces  216 A and  216 B to cleanly abut one another, resulting in reduced insertion loss and return loss, and thereby resulting in reduced network failures. 
     In alternative embodiments, the number and configuration of ridges and grooves may vary. For example, as shown in  FIG. 14 , an internal fluting within the guide pin holes  25  may include fours ridges  53  separated by four grooves  55 , also configured so that when one housing is inverted for mating the ridges align with grooves of an opposing housing. Alternatively, there may be five ridges/five grooves, six ridges/six grooves, seven ridges/seven grooves or eight ridges/grooves, or any configuration of ridges and grooves that may be accommodated by the internal dimensions of the guide pin holes. In general, the pin holes  25  may have n longitudinal ridges separated by n longitudinal grooves. The n longitudinal ridges may be disposed equidistantly from one another on the interior surface and spaced at 360°/n from one another along the internal circumference of the pin hole, and each ridge may extend in a circumferential direction at most about 360°/2n along the internal circumference of the pin holes. Similarly, the n longitudinal grooves may be disposed equidistantly from one another on the interior surface and spaced at 360°/n from one another along the internal circumference of pin hole, and each groove may extend in a circumferential direction at least about 360°/2n along the internal circumference of the pin holes. 
     This disclosure is not limited to the particular systems, devices and methods described, as these may vary. The terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope. 
     In the above detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
     The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. 
     As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Nothing in this disclosure is to be construed as an admission that the embodiments described in this disclosure are not entitled to antedate such disclosure by virtue of prior invention. As used in this document, the term “comprising” means “including, but not limited to.” 
     While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of” or “consist of” the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups. 
     With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. 
     It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” 
     In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group. 
     As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth. 
     Various of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.

Technology Classification (CPC): 6