Abstract:
An optical connector is provided to reliably hold a ferrule assembly in a housing to enable it stable optical connection. The optical connector is able to accomplish stable connection without any concern of displacement of an optical connecting end portion of the ferrule, even if the optical connector is subjected to repeated connecting and disconnecting operations. In the optical connector, a ferrule assemble having a polygonal prism-shaped flange is accommodated and held so as to elastically reciprocate in a housing of a cavity which has a polygonal engaging portion to receive and engage the flange of the ferrule assemble. A protrusion is formed at an end part of each engaging wall in the direction of inserting the ferrule assemble to rise toward an insertion opening for the ferrule assemble, and each protruding portion of the protrusion is provided to have each different rising height thereof.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a housing for an optical connector which holds a ferrule assembly to be used for transmitting and receiving optical signals, and an optical connector for equipping the ferrule assembly to the housing. 
       BACKGROUND 
       [0002]    Conventionally, a ferrule which is used as a connecting end of an optical fiber for transmitting and receiving optical signals in optical communication is usually obtained by forming ceramics consisting primarily of zirconia into a predetermined shape by injection molding or the like, and then baking thereof. The ferrule is provided a through-hole for inserting an optical fiber and is used as a ferrule assembly to hold and fix the optical fiber in the through-hole. The ferrule assembly is widely used in optical connectors that are used to connect optical fibers together and to establish a communication path, or in a semiconductor laser module that is constituted by a semiconductor laser, the optical fiber and the like. 
         [0003]    The optical connector is widely used to transmit the optical signals emitted from the semiconductor module or the like to another optical component through the optical fiber, or used as relay members connected between the optical fibers to transmit the optical signals to the optical component placed at a far distant location. The optical connector in this type is a preferred connection configuration that opposite ferrule ends each other are accurately and closely contacted therebetween and axis lines of the ferrules (specifically, axis lines of cores of the ferrules) are aligned each other to efficiently transmit light from one optical fiber to the other optical fiber. For the optical connectors, stability of assembling thereof at an on-site of connection and protection of connecting portion are required, and further, in order to minimize connection loss when the optical connectors are mutually connected, it is desirable to accurately align the cores of the optical fibers, and manufacturing error is required to be eliminated as much as possible. It is specified that the axis lines of the fiber cores must be aligned within a range of connection error of μm order when the optical fibers are connected together, so that not only a high degree of accuracy is required for shapes and dimensions of components constituting the optical connector which becomes the connection ends, but also the utmost attention must be paid to assembling the optical connector. 
         [0004]    A communication path is established by inserting the optical connector described above into an opening of a jack socket disposed on a panel such as a wall. When the optical connector is inserted into the opening of the jack socket, a latch formed integrally with a housing of the optical connector is interlocked in the opening of the jack socket and held in order not to fall easily. In addition, there are many situations to be used the optical connectors which are oppositely connected in an adapter housing to extend the optical fiber. 
         [0005]    An example of the optical connector having the above-described configuration is disclosed, for example, in the Japanese Patent No. 3996335 of Patent Document 1. In a conventional optical connector  50  shown in  FIGS. 8 and 9 , a housing  51  which has a rectangular outer shape and is cylindrically formed a main body, and a cavity  52  is formed in the housing. A latch  53  is integrally provided on the housing  51 , and the housing  51  is held by interlocking, engaging the latch in the opening of the jack socket fitted to a panel or the like. A ferrule assembly  54  which has a ferrule  55  to establish a communication path is accommodated in the cavity  52 . A compression coil spring  56  is fitted around the ferrule assembly  54 , and the ferrule assembly is retained in the cavity so as to be elastically advanced or retracted by an elastic resilient force of the compression coil spring  56 , and is resiliently connected to another opposite ferrule (not shown), and a communication path is established. In the drawings, numeral  61  denotes a dust cap for protecting the ferrule from dust, dirt, and stains. 
         [0006]    As specifically shown in  FIG. 9 , the ferrule assembly  54  has the ferrule  55  and a holder  57  which holds it, and the holder  57  has a guide sleeve  57   a  to guide the compression coil spring  56 , and a flange  57   b  formed to a hexagonal column shape to be urged by the compression coil spring  56 . A truncated cone shaped guide portion  57   c  which is continued to the flange  57   b  is formed in the front portion where the ferrule is fitted. 
         [0007]    And, the ferrule assembly  54  is accommodated in the housing  51  in a state that the guide sleeve  57   a  is supported by an insertion  58 , and an optical connection end of the ferrule  55  is projected toward an opening  51   b  of one end of the housing  51 . At this time, the holder  57  of the ferrule assembly  54  is fitted into a recess  51   a  and a recess  51   d  which have shapes which have corresponding to the holder  57 , and as shown in  FIG. 8 , an opening  51   c  of the other end is closed by a sealing member so that the projection position of the ferrule  55  is established. By the sealing by the sealing member  60 , therefore, a front end of a trigger lever  60   a  projected from the sealing member  60  is positioned above the latch  53  of the housing  51 . By pressing the trigger lever  60   a  downward, the latch  53  opposite thereto descends resistively against an elastic force, so that an interlock of the optical connector  50  inserted into an opening of a jack socket or the like is released and is able to be pulled out therefrom. 
         [0008]    Patent Document 1: Japanese Patent No. 3996335 
       DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0009]    A ferrule and an optical connector are precisely manufactured to achieve accurate optical connection. And as shown in  FIG. 9 , a recess  51   d  which has a hexagonal shape which is provided so as to correspond to the shape of the flange  57   b  is provided in the cavity  52 , and the ferrule assembly  54  is normally urged by the compression coil spring  56  to add an appropriate pressing force to the connection end. Therefore, the flange  57   b  is accurately and closely engaged with the recess  51   d  by the pressing force of the compression coil spring  56 , and the ferrule assembly  54  is mounted in the cavity  52  of the housing  51 , then an appropriate communication path to an end of the other side to be connected is established to perform high-quality signal transmission. 
         [0010]    However, when the ferrule assembly  54  is accommodated in the cavity  52  through the manufacturing process to assemble the optical connector, there may be a case that, as shown in  FIG. 10 , the flange  57   b  which has a hexagonal column shape is not closely engaged with the recess  51   d  and the flange is fixed by the urging force of the compression coil spring  56 . Also, when the optical connector is repeatedly inserted into and pulled out from a jack socket, or repeatedly connected to and removed from an adapter for relay, there may be a case that the ferrule assembly  54  is fixed in the incomplete state shown in  FIG. 10 . When an optical connection operation is carried out by using the optical connector in which the ferrule assembly  54  is held in such an incomplete state, it is impossible to carry out accurate transmission of optical signals, and long working hours may be required to conduct operation without knowing the cause of the connection failure. Moreover, even though precision work is performed on components of the optical connector, actually subtle and serious eccentricity may occur in the optical connection. Therefore, after assembling the optical connector, it is adjusted that the engagement between the flange  57   b  and the recess  51   d  is released once, and the ferrule assembly  54  is rotated, then the flange  57   b  and the recess  51   d  are engaged with each other again at a position that an condition of an optimum optical connection is obtained. However, also in such case, there is a risk that the flange  57   b  is incompletely engaged with the recess  51   d.    
         [0011]    In view of the above conventional problems, the present invention provides a housing for an optical connector and an optical connector which are possessed a reliability of assemblage thereof, and are easy repeatedly to attach and remove the optical connector, and have high connection reliability as the optical connector. 
       Means for Solving the Problems 
       [0012]    The subject matter of the present invention is defined by: 
         [0013]    (1) a housing for an optical connector, comprising a cavity to accommodate and hold a ferrule assembly having a polygonal prism-shape flange and to hold the ferrule assembly to be capable of elastically advancing and retracting thereof, the housing characterized by comprising, 
         [0014]    a polygonal engaging portion provided in the cavity to insert and engage the flange of the ferrule assembly, and 
         [0015]    a protrusion provided at an end side of each engaging wall which forms the engaging portion in a direction of inserting the ferrule assembly therein to rise in a direction of an opening for inserting the ferrule assembly, wherein each protruding portion of the protrusion is provided to have different rising height each other; 
         [0016]    (2) the housing for an optical connector according to the above recited item (1), wherein the each protruding portion rises in a state of a curved surface; 
         [0017]    (3) the housing for an optical connector according to the above recited item (1), wherein the each protruding portion rises to form a curved surface having the same curvature radius; 
         [0018]    (4) the housing for an optical connector according to the above recited item (1) or (2), wherein the height of the protruding portion which is adjacent to one another is lowered consecutively; and 
         [0019]    (5) an optical connector characterized in that a ferrule assembly is held in a housing by fitting and engaging a flange of the ferrule assembly with the engaging portion of the housing for the optical connector according to any of the above recited items (1) to (4). 
       EFFECTS OF THE INVENTION 
       [0020]    According to the optical connector of the present invention, the ferrule assembly is rotatively moved around the axis thereof and the flange is always reliably and closely engaged with the recess which has a shape corresponding to the shape of the flange so that the ferrule assembly is smoothly accommodated in the cavity in a manufacturing process for assembling the connector, and further the ferrule assembly is held by a stable urging force of the spring, therefore, the reliability is increased at the time of assembling the connector, and there is no risk of decreasing accuracy of connection even when the connector is repeatedly fitted and removed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is an exploded perspective view of an optical connector according to the present invention. 
           [0022]      FIG. 2  is a vertical cross-sectional view of a housing of the optical connector according to the invention. 
           [0023]      FIG. 3  is a view of the housing of the optical connector as viewed from the direction of arrow A in  FIG. 2 . 
           [0024]      FIG. 4  is a schematic development view schematically showing a shape of a recess of the housing. 
           [0025]      FIG. 5A  is a side view of a ferrule assembly. 
           [0026]      FIG. 5B  is a vertical cross-section of the ferrule assembly. 
           [0027]      FIG. 6  is a partial vertical cross-sectional view showing a relationship between the housing and the ferrule assembly. 
           [0028]      FIG. 7  is a schematic view of a pressing test apparatus. 
           [0029]      FIG. 8  is a plan view of a conventional optical connector. 
           [0030]      FIG. 9  is a vertical cross-sectional view showing a good assembly state of a conventional housing for an optical connector and a ferrule assembly. 
           [0031]      FIG. 10  is a vertical cross-sectional view showing a bad assembly state of the conventional housing and the ferrule assembly. 
       
    
    
     EXPLANATION OF REFERENCE NUMERALS 
       [0000]    
       
           1 : Optical connector 
           2 : Housing 
           3 : Ferrule assembly 
           4 : Insertion 
           5 : Sealing member 
           6 : Latch 
           9 : Ferrule 
           10 : Holder 
           10   a : Flange 
           12 : Compression coil spring 
           13 : Cavity 
           14 : Recess 
           14   a : Engaging portion 
           14   b : Fitting portion 
           14   c : Protrusion 
       
     
       DESCRIPTION OF PREFERRED EMBODIMENT 
       [0047]    Hereinafter, a preferred embodiment for working the present invention will be described with reference to the drawings. 
         [0048]      FIG. 1  is an exploded perspective view of an optical connector according to the present invention,  FIG. 2  is a vertical cross-sectional view of a housing of the optical connector according to the invention,  FIG. 3  is a view as shown from the direction of arrow A in  FIG. 2 ,  FIG. 4  is a schematic development view explaining a shape of a recess, by spreading thereof, of the housing of the invention,  FIGS. 5A and 5B  are respectively a side view and a vertical cross-sectional view of a ferrule assembly,  FIG. 6  is a partial vertical cross-sectional view showing a relationship between the housing and the ferrule assembly, and  FIG. 7  is a schematic view of a pressing test apparatus. 
         [0049]    As shown in  FIG. 1 , an optical connector  1  of the invention is comprised of a housing  2  which is a main body of equipment, a ferrule assembly  3  accommodated in the housing  2 , an insertion  4  that guides the ferrule assembly  3 , and a sealing member  5 . The housing  2  and the sealing member  5  are made of a based material of a polyphenylsulfone (PPSU). A cavity  13  is formed inside the housing  2  ( FIG. 2 ). On the housing  2 , a latch  6  is integrally formed with the housing as cantilevered manner to project from the housing by providing a base anchor at a connection end side thereof. A dust cap  8  is removably mounted to an opening  7  where an optical connection end of the ferrule is located. 
         [0050]    As shown in  FIGS. 5A and 5B , a main body of the ferrule assembly  3  is comprised of a ferrule  9  and a holder  10  that firmly holds the ferrule  9 . The ferrule  9  is formed from ceramics or zirconia by a known method such as injection molding. On the other hand, the holder  10  is made of stainless steel or brass. The ferrule  9  has a through-hole  9   a  for inserting an optical fiber in the axis direction thereof and is held to the holder  10  by means of press fitting or adhesive bonding. In the invention, the ferrule  9  is available to use any of a single mode ferrule and a multi mode ferrule. The ferrule  9  is formed into a cylindrical shape, and for example, may have an external diameter D of φ1.25 mm, a length L of 6.4 mm, and an internal diameter d of φ0.125 mm. 
         [0051]    The holder  10  is provided with a guide sleeve  10   c  which is integrally formed on the rear end of a flange  10   a  of a hexagonal column shape to guide a compression coil spring, and a guide portion  10   b  of a shape of a frustum of a cone is integrally formed on the front end of the flange  10   a . On the flange  10   a  of a hexagonal column shape in the holder  10 , the distance between wall surfaces facing each other is specified as 2.54 mm. A flexible tube  11  is inserted and fitted to the guide sleeve  10   c  of the holder  10 , and a compression coil spring  12  is mounted and fitted around the outer circumference of the tube  11 . The ferrule assembly  3  is held in an elastically advanceable and retractable manner by the compression coil spring  12  in the cavity  13 . The cylindrical insertion  4  is inserted from the rear end of the tube  11  and presses an end of the compression coil spring  12 , and the sealing member  5  and the housing  2  are engaged with each other in the longitudinal direction, so that the ferrule assembly  3  is accommodated in the cavity  13 , the end of the insertion  4  is projected from an end of the sealing member  5 , and the optical connector is assembled in the same way as the conventional optical connector shown in  FIG. 8 . By this assembling, the ferrule assembly  3  is elastically accommodated in the cavity as shown in  FIG. 6 . By the engagement of the housing  2  and the sealing member  5 , a front end of a trigger lever  5   a  of the sealing member  5  is positioned above the latch  6  of the housing  2 . 
         [0052]    The cylindrical cavity  13  is formed in the housing  2 , and a recess  14  which has a shape corresponding to the shape of the holder  10  is formed between the cavity  13  and the opening  7  in which a forward end of the optically connected ferrule  9  is situated. Specifically, the recess  14  is provided with a fitting portion  14   b , a shape of which is corresponded to the truncated cone shape of guide portion  10   b , and the flange  10   a  of the hexagonal shape, and a hexagonal shaped engaging portion  14   a  which are adjacent to each other. Protrusion  14   c  (comprised of a plurality of protruding portions  14   c   1  to  14   c   6 ) is formed at each side edge of a plurality of wall portions  14   a   1  to  14   a   6  of the engaging portion  14   a  in the direction of inserting the ferrule assemble (i.e., from each side part or edge of the of the wall portions  14   a   1  to  14   a   6  toward the cavity  13 ). It is preferred that the plurality of the protruding portions  14   c   1  to  14   c   6  is formed to rise in a shape of curved surface. The boundary portions between the protrusion  14   c  and the wall portions of the engaging portion  14   a , are smoothly connected, therefore, the ferrule assembly  3  can be easily and reliably inserted into and held in the housing  2 . It is preferred that the shape of the curved surface of the each protruding portions are formed to have the same curvature radius R, and the radius R is preferred to be about 0.45 mm to 0.85 mm. As shown in  FIGS. 3 and 4 , each rising height L of the protruding portions  14   c   1  to  14   c   6  is preferred to be 0.24 mm to 0.51 mm to have the respectively varied and different heights thereof. As schematically shown in  FIG. 4 , it is preferred that rising heights L 1  to L 6  of the adjacent protruding portions are formed such that the heights are successively lowered. For example, a rising height L 1  of the protruding portion  14   c   1  is set to 0.45 mm, and a rising height L 2  of the adjacent protruding portion  14   c   2  is set to 0.42 mm, and in the same way, from L 3  to L 6 , the respective rising height thereof is successively lowered by 0.03 mm by changing a protruding amount. As a result, since the rising height L 1  of the highest protruding portion  14   c   1  is 0.45 mm and the rising height L 6  of the lowest protruding portion  14   c   6  is 0.30 mm, and the difference becomes 0.15 mm. In this way, by successive variation of the rising heights of the protruding portion adjacent to one another, the flange  10   a  of the ferrule assembly  3  is smoothly guided to the protrusion  14   c , and the ferrule assembly  3  is rotated around the axis thereof and easily held in the recess  14 . 
         [0053]    As shown in  FIG. 6 , optical connection can be achieved by inserting the holder  10  into the recess  14  so that the flange  10   a  of the holder  10  is reliably engaged with the engaging portion  14   a . However, if an insignificant eccentricity occurs, the engagement of the flange  10   a  and the engaging portion  14   a  is released, and the ferrule assembly  3  is rotated, and the flange  10   a  and the engaging portion  14   a  are engaged together again in a position where an optimal optical connection can be achieved. 
         [0054]    In the example described above, a case in which the flange  10   a  of the holder  10  has a hexagonal column shape is described. However, the shape of the flange  10   a  may be a square prism-shape or other polygonal prism-shapes. It is understood that the shape of the flange is not limited to the shape described in the embodiment since the shape of the flange may be appropriately determined. 
         [0055]    In addition, the curvature radius and the rising height of the protrusion of the invention can be properly changed in design by those skilled in the art, and are not limited to the values described above. Although an example is described in which the rising heights of the protruding portions adjacent to one another is changed in a stepwise manner, it is possible to form the protruding portions into a continuously spiral shape as a whole, in which the height is gradually lowered, by smoothly lowering the rising heights of the protruding portions. 
       EXAMPLE 
       [0056]    Three optical connectors (samples 1 to 3) of the present invention which have protruding portions formed so that the rising heights are lowered from 0.45 mm to 0.30 mm to be respectively and lowered 0.03 mm in order, and three conventional optical connectors (samples 4 to 6) which do not have protrusion are prepared. Then, the ferrule  9  is repeatedly pressed by a pressing test apparatus shown in  FIG. 7 , and whether or not the ferrule  9  returns to a correct position is tested. 
         [0057]    The pressing test apparatus is entirely controlled by a controller (CPU)  21 , and reciprocative movement is repetitively is given to the ferrule  9  by reciprocating a plunger  20   a  of a cylinder apparatus  20  being straight to the ferrule  9 . When the ferrule  9  is pressed by the plunger  20   a , the ferrule assembly  3  is evacuated in the opening  7  against the force of the compression coil spring described above. This evacuation operation becomes an adjustment operation of the eccentric position described above. The reciprocal movements of the ferrule  9  are detected by sensors  26   a  and  26   b , and the movements are captured by a video camera  25  and displayed on a monitor  24 . An output signal from the sensor  26  is measured by a counter  23  and the result is stored in a memory  22 . In spite of evacuation of the ferule  9  after the projecting movement of the plunger  20   a , if the ferrule  9  does not project to the original position by the elastic force of the compression coil spring, the sensor counts one error, i.e. 1 of the error. 
         [0058]    The reciprocal movement of the plunger is performed 50 times for each sample by using the above-described measurement apparatus, and the number of errors was measured. The result is shown in table 1. As seen from the result in table 1, for the conventional optical connectors, the error occurs 9 times in the sample 4, 5 times in sample 5, and 7 times in the sample 6. On the other hand, for the optical connectors of the present invention, it is demonstrated that the error hardly occurs in any of the samples 1 to 3, and only one time error occurred in the sample 3. A large difference in stability when the ferrule assembly is contained into the housing is observed between the optical connector obtained by using the housing of the invention which includes protrusion in the cavity and the optical connector obtained by using a conventional housing which does not include protrusion. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                   
                 Comparative Example 
               
               
                   
                 Example 
                 (Conventional Article) 
               
               
                   
                 (Present Invention) 
                 Protrusion: 
               
               
                   
                 Protrusion: Existence 
                 Nonexistence 
               
             
          
           
               
                   
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
               
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
               
               
                   
                   
               
             
          
           
               
                 Number of 
                 0 
                 0 
                 1 
                 9 
                 5 
                 7 
               
               
                 times 
               
               
                 Counted Error: 
               
               
                 (In 50 Times of 
               
               
                 Operating Test)