Abstract:
An optical connector plug to be inserted to an adapter, is arranged such that a pair of engaging parts for expanding an elastic locking piece provided on a side of the adapter by a taper part and locking it with a step part is provided on a tip part of a plug frame which is a body of the plug; a locking releasing piece movable along an insertion-extraction direction is provided between the pair of engaging parts; a taper part for releasing a locking action of the elastic locking piece when extracting the plug is provided at a rear end of the locking releasing piece; and the taper part of the engaging parts has such a shape that the connecting stress is not lowered before being locked when inserting the plug.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an optical connector plug to be inserted into and extracted from a connector adapter, particularly relates to an optical connector plug which is easily inserted into and extracted from the connector adapter, and which is compatible with a SC type connector in the connector for optical fiber cord connection. 
       BACKGROUND ART 
       [0002]    In recent years, along with the development of FTTH, the opportunity for ordinary people other than a special construction dealer to touch an optical connector is increasing. In connector operations, when inserting and extracting the conventional SC type connector plug into and from a connector adapter, the connector plug remains in the connector adapter in the half-way in insertion or extraction, and it is known that a so-called half-way insertion occurs. In order to avoid this state, conventionally a marking was put on a part of the connector plug, and the connector plug was inserted or extracted so that the marking is invisible. 
       CITATION LIST 
     Patent Literature 
       [0003]    PTL 1: Japanese Patent Laid-Open No. s62-78507 (1987) 
         [0004]    PTL 2: Japanese Patent Publication No. 4215577 
         [0005]    PTL 3: Japanese Patent Laid-Open No. 2008-176297 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    The problem in the insertion and extraction of the conventional SC type connector plug into and from the connector adapter is described in further details with reference to the patent literature 1. 
         [0007]      FIG. 1A  to  FIG. 1E  are diagrams showing a connecting mechanism  100  in the conventional SC type connector. 
         [0008]    In  FIG. 1A , when a conventional SC type connector plug  110  is inserted into a connector adapter  120 , an adapter elastic locking piece  121  moves a flat part  112  at a tip part of a plug housing after moving along a slope  111  while being extended along the slope at the tip of the plug housing ( FIG. 1B ). Then, when the elastic locking piece  121  goes down along a slope  113  at a rear part of the plug housing, the tip of the elastic locking piece  121  falls in front of a suspending part  114  of a plug frame ( FIG. 1C ). If the plug  110  is furthermore pushed in, the plug  110  moves while the elastic locking piece  121  touches the suspending part  114  of the plug frame ( FIG. 1D ), and the elastic locking piece  121  is eventually fallen and locked by a step part  115  of the plug frame, and the engagement is attained ( FIG. 1E ). 
         [0009]    When such operation is performed, changes in stress  200  measuring the force of inserting the plug  110  into the adapter  120  are shown in  FIG. 2 . 
         [0010]    As for a stress when inserting the conventional SC type connector plug  110  into the adapter  120 , first, the adapter elastic locking piece  121  contacts a tip part of a plug housing, and by moving along the slope  111 , the elastic locking piece  121  is extended. Thus, the stress increases abruptly (symbol b). Thereafter, while the elastic locking piece  121  moves along the flat part  112  of the plug housing, and the slope  113 , changes in stress are seen, and the stress becomes almost zero when the elastic locking piece  121  falls in front of the suspending part  114  of the plug frame (symbol c). When being further inserted, the elastic locking piece  121  moves the suspending part  114  of the plug  110  on the other side (symbol d). Further, the stress increases as a ferrule of the plug starts contacting a partner ferrule on the other side, and the stress becomes almost zero when the elastic locking piece  121  falls in the step part  115  of the plug, and is stopped, whereby the plug is in the completely connected state (symbol e). By further inserting, a repulsive force from the ferrule on the other side is added, and the stress increases again. 
         [0011]    As can be seen in  FIG. 2 , since the state (symbol c) where the stress becomes almost zero exists in the middle of the connecting process, a worker mistakes the state for the state (symbol e) where the stress becomes zero when connected. In this case, a worker stops the connecting operation on the way, and the state in which the connector plug  110  has not been inserted into the connector  120  on the other side completely (half-way insertion) occurs. 
         [0012]    In order to avoid the foregoing state of the half-way insertion, the several measures have been taken. For example, the procedures to insert until it stops moving, or until hearing the clicking sound are described in the procedure manual. Moreover, a white line is printed on a connector housing in order to determine that the connector plug is completely connected. 
         [0013]    The above measures may be effective. However, under bad installation conditions of the adapter  120 , it may be hard to hear the sound when connected, or the white line is hard to recognize if the connector housing cannot be seen directly. Therefore, in fact it is difficult to completely prevent the half-way insertion. Furthermore, as the FTTH becomes popular, the cases where unskilled workers or ordinary people deal with the optical connector are increasing, and the measure for preventing this state of half-way insertion is more necessitated. 
         [0014]    Also when extracting the plug from the adapter, the plug is stopped on the way in the state where the stress becomes zero (symbol c). This state is also the state of half-way insertion when extracting, which is a problem. If this state of the half-way insertion occurs, although the plug  110  is apparently inserted into the adapter  120 , light is not conducted. Therefore, this may cause a delay in defining a factor of a failure. 
         [0015]    The present invention has been made in view of the above circumstances and provides an optical connector plug which can prevent an occurrence of such phenomena that a connecting stress is reduced to zero or lowered on the way in a process of inserting or extracting, or preventing an occurrence of a half-way insertion on the way of inserting or extracting process, when a general person other than a professional construction worker inserts or extracts the optical connector. 
       Solution to Problem 
       [0016]    In order to solve the above problem, the optical connector plug of the present invention is the optical connector plug to be inserted into an adapter, wherein a pair of engaging parts for expanding an elastic locking piece provided on a side of the adapter by a taper part and locking it with a step part is provided on a tip part of a plug frame which is a body of the plug; a locking releasing piece movable along an insertion-extraction direction is provided between the pair of engaging parts; a taper part for releasing a locking action of the elastic locking piece when extracting the plug is provided at a rear end of the locking releasing piece; and the taper part of the engaging parts has such a shape that the connecting stress is not lowered before being locked when inserting the plug. 
         [0017]    The optical connector plug includes a flat face between the taper part and the step part of the engaging part. 
         [0018]    The taper part of the engaging part has a multistage tapered shape. 
         [0019]    The optical connector housing is provided with a light-shielding member. 
       Advantageous Effects of Invention 
       [0020]    According to the optical connector plug of the present invention, when connecting to the adapter, an adapter elastic locking piece is directly extended by the plug frame, to move the plug frame, and the adapter locking piece falls in a suspending part, thereby completing the connecting. With this mechanism, both the frame front part and frame center part of the plug form slopes, more preferably form slopes with constant inclination, whereby the stress increases gradually until the adapter locking piece falls in the suspending part of the plug frame, and it is possible to hold a change amount in stress to the same as possible. 
         [0021]    As a result, the stress does not decrease in the middle when connecting the plug. Thus, the worker who connects the connector plug does not misunderstand that the plug is inserted in the suspending part, thereby preventing the half-way insertion. 
         [0022]    Further, as the 7th clause of JIS C5973, structure, form, and size is defined in  FIG. 1A  through  FIG. 1E , generally, SC has a slope angle of a front part of the plug frame of 25° to 35°. Here, the smaller is this slope angle, the smaller is the stress when connecting the plug frame to the adapter. In the optical connector plug of the present invention, however, since the taper part for extraction at a rear part of the plug housing of the conventional SC type connector is not needed, there is an advantage that the slope angle can be made smaller. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]      FIG. 1A  is a drawing explaining a connecting mechanism of a SC type connector using conventional technology; 
           [0024]      FIG. 1B  is a drawing explaining the connecting mechanism of the SC type connector using conventional technology; 
           [0025]      FIG. 1C  is a drawing explaining the connecting mechanism of the SC type connector using conventional technology; 
           [0026]      FIG. 1D  is a drawing explaining the connecting mechanism of the SC type connector using conventional technology; 
           [0027]      FIG. 1E  is a drawing explaining the connecting mechanism of the SC type connector using conventional technology; 
           [0028]      FIG. 2  is a drawing showing changes in stress when connecting the SC type connector using conventional technology; 
           [0029]      FIG. 3A  is a drawing explaining a connecting mechanism of an optical connector plug according to an embodiment in the examination process of the invention of the present invention; 
           [0030]      FIG. 3B  is a drawing explaining the connecting mechanism of the optical connector plug according to the embodiment in the examination process of the invention of the present invention; 
           [0031]      FIG. 3C  is a drawing explaining the connecting mechanism of the optical connector plug according to the embodiment in the examination process of the invention of the present invention; 
           [0032]      FIG. 3D  is a drawing explaining the connecting mechanism of the optical connector plug according to the embodiment in the examination process of the invention of the present invention; 
           [0033]      FIG. 4  is a drawing showing changes in stress when connecting the optical connector plug according to the embodiment in the examination process of the invention of the present invention this application; 
           [0034]      FIG. 5A  is a drawing explaining a connecting mechanism of an optical connector plug according to a first embodiment of the present invention; 
           [0035]      FIG. 5B  is a drawing explaining the connecting mechanism of the optical connector plug according to the first embodiment of the present invention; 
           [0036]      FIG. 5C  is a drawing explaining the connecting mechanism of the optical connector plug according to the first embodiment of the present invention; 
           [0037]      FIG. 5D  is a drawing explaining the connecting mechanism of the optical connector plug according to the first embodiment of the present invention; 
           [0038]      FIG. 5E  is a drawing explaining the connecting mechanism of the optical connector plug according to the first embodiment of the present invention; 
           [0039]      FIG. 6  is a drawing showing changes in stress when connecting the optical connector plug according to the first embodiment of the present invention; 
           [0040]      FIG. 7A  is a drawing showing a variation of a slope form of a plug frame of the optical connector plug according to the first embodiment of the present invention; 
           [0041]      FIG. 7B  is a drawing showing a variation of a slope form of a plug frame of the optical connector plug according to the first embodiment of the present invention; and 
           [0042]      FIG. 8  is a drawing showing an outline of the optical connector plug with a light-shielding member according to a second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0043]    An optical connector plug of the present invention is explained in detail with reference to the drawings. 
         [0044]    First, an embodiment in an examination process of the present invention is described based on the connector plug shown in the patent literature 2. The patent literature 2 discloses a connector plug of SC type conformity. The adapter disclosed in the patent literature 2 is the same as that of the SC type connector adapter shown in  FIG. 1A  to  FIG. 1E , and only the form of a connector plug differs. In the examination process of the present invention, a configuration wherein a tip slope is added to the connector plug disclosed in the patent literature 2 is considered. 
         [0045]      FIG. 3A  to  FIG. 3D  are drawings explaining a connecting mechanism  300  of a connector according to an embodiment in the examination process of the present invention. 
         [0046]    The comparison with the conventional technology is described in detail. That is, in the conventional SC type connector  110  shown in  FIG. 1A  to  FIG. 1E , when connecting, after extending and moving the elastic locking piece  121  of the adapter  120  along the slope  111  at a front part of the plug housing, the locking piece  121  falls in the step part  115  of the connector plug  110 , whereas when releasing the connecting, the elastic locking piece  121  is opened by the slope  113  at the rear part of the plug housing to come off from the step part  115 . 
         [0047]    On the other hand, according to the connector shown in  FIG. 3A  to  FIG. 3D , an elastic locking piece  321  of an adapter  320  is opened directly by a front part  311  of the plug frame ( FIG. 3B ), and after moving along a flat part  312  of the plug frame ( FIG. 3C ), the locking piece  321  falls in a step part  313  of the plug frame ( FIG. 3D ). When releasing the connecting, the elastic locking piece  321  is opened by a pulling plate  314  located between a plug frame  310  and the elastic locking piece  321 , to come off from the step part  313 . 
         [0048]      FIG. 4  is a drawing showing changes in stress  400  when the connector plug  310  is inserted into the adapter  320 . According to the SC type connector of the conventional technology, the elastic locking piece  121  falls by the slope  113  at the rear part of the plug housing, which surrounds the plug frame  110 . According to the connector plug  310  shown in  FIG. 3A  through  FIG. 3D , since the elastic locking piece  321  does not fall on the way, it is not seen that the stress becomes zero. As a result, the state of the half-way insertion is less likely to occur as compared to the SC type connector of the conventional technology. 
         [0049]    However, such phenomenon that the connecting stress is reduced from the start in the half way is seen also in the mechanism in which this plug frame extends the elastic locking piece  321  of the adapter directly, although the stress in the half-way does not become zero. In this case, a worker may feel like there becomes no stress when working. 
         [0050]    Moreover, when extracting the connector plug  310  from the connector adapter  320 , since stress is not changed halfway, it becomes in a stable state, and the situation in which the connector plug  310  has not come off from the connector adapter  320  occurs, and there is a problem that a worker may have an erroneous recognition. 
         [0051]    The optical connector plug according to the present invention which solves the above problem is explained with reference to the drawings. 
         [0052]      FIG. 5A through 5E  are drawings explaining a connecting mechanism  500  of the optical connector plug according to the first embodiment of the present invention. 
         [0053]    As shown in  FIG. 5A through 5E , an optical connector plug  510  which has a locking releasing piece  514  in the position which adjoins a frame part is extended by an approximately 10° tip taper part  511  in an locking piece  521  of a connector adapter  520  by pushing in a plug ( FIG. 5B )). 
         [0054]    By pushing in, the locking piece  521  can extend gradually by an approximately 8° loose continuous central slope  512 , and a rear flat part is moved ( FIG. 5C ), finally it falls in a step part  513 , and the connector plug  510  and the connector adapter  520  connect in ( FIG. 5D ). 
         [0055]    When releasing the connected plug  510  from the adapter  520 , the plug  510  is retreated, while retreating the locking releasing piece  514  and releasing the locking piece  521  from the step part  513  ( FIG. 5E ). 
         [0056]      FIG. 6  is a drawing showing changes in stress  600  when connecting the optical connector plug according to the first embodiment of the present invention. 
         [0057]    The connector shown in  FIG. 3A  through  FIG. 3D  is extended along an approximately 33° slope at an internal tip of the plug frame. In contrast, the optical connector plug  510  according to the first embodiment of the present invention is extended along the approximately 10° slope  512 . Thus, the stress when starting the connecting decreases from approximately 10 N to approximately 4 N. Furthermore, the connector shown in  FIG. 3A  through  FIG. 3D  moves on the flat frame on the way of insertion, and therefore, the stress drops down from the initial state of connecting although the stress does not become zero. In contrast, in the optical connector plug  510  according to the first embodiment of the present invention, since the taper part  511  at the tip portion of the plug frame is a gentle continuous slope, the elastic locking piece  521  is only gradually extended as the plug  510  is inserted into the adapter  520 . Thus, the connecting stress hardly reduces from that in the initial state of connecting, but is increased again after the plug  510  contacts the ferrule on the other side, and the elastic locking piece  521  falls in the step part. Then, the stress decreases and connecting is completed. 
         [0058]    From these results, the optical connector plug according to the present invention has a smaller stress in early stages of insertion and the connecting stress in the middle of insertion hardly reduces but increases gradually compared with the stress of connector shown in  FIG. 3A  through  FIG. 3D . As a result, the state of the half-way insertion is still less likely to occur. 
         [0059]    As shown in variations  700  and  710  for the slope shapes of the plug frame of  FIG. 7A  and  FIG. 7B  respectively, the width at a tip part of a taper part is almost equal to distances  705 ,  715  of the two locking pieces, and as for the slope, it is desirable that the inclination be as small as possible, and as continuous as possible so that the abrupt change in connecting stress does not occur. 
         [0060]    Next, a second embodiment of the present invention is described with reference to  FIG. 8 . 
         [0061]    The second embodiment is an embodiment provided with a light-shielding member disclosed in the patent literature 3.  FIG. 8  is a drawing showing an outline of a connector  800  provided with a light-shielding member according to the second embodiment of the present invention. 
         [0062]    In  FIG. 8 , the light-shielding member is made up of a shutter housing  804  which surrounds an outside of a tubular plug frame  803  which stores therein and supports a ferrule  802  holding a tip part of an optical fiber  801 , so as to make a freely slidable contact with the tubular plug frame  803 , and which is inserted inside the opening part for connecting of a receptacle connector to be connected when connecting the optical connector; a shutter  805 , one end part of which is supported by the housing at a front part of the shutter housing  804 , the other end portion of which is energized by the elastic force from a spring  806  so as to shield the optical fiber  801  at the front portion of the ferrule  802  to be closed; and an elastic member (not shown), provided inside the shutter housing  804 , always energizing the shutter housing  804  forwards, which is provided in a spacing between the rear part of the plug frame  803  and the shutter housing  804 . 
         [0063]    Moreover, according to the light-shielding member of the present embodiment, the shutter housing  804  surrounds the outside of the tubular plug frame  803  which stores therein and supports the ferrule  802  holding the tip part of the optical fiber  801 , so as to make a freely slidable contact with the tubular plug frame  803 , and is inserted inside the opening part for connecting of the receptacle connector. Therefore, the guide nature when mounting can be exhibited, and even if the light-shielding member is added on the side of the plug, there is no need of improvement in particular on the receptacle connector side of the other side of connecting, and it can be connected in the same manner as the conventional manner. Thus, the light-shielding member is highly versatile. Furthermore, the light-shielding member does not go outside the outside dimension of the plug housing of an optical plug connector, and therefore does not become an obstacle in a high density assembly. 
         [0064]    The connecting mechanism of the optical connector plug described in the first embodiment of the present invention shown in  FIG. 5A through 5E  can be adopted also in the configuration provided with the light-shielding member shown in  FIG. 8 , and changes in stress when connecting the optical connector plug as shown in  FIG. 6  can be reproduced. 
         [0065]    According to the optical connector plug of the present invention, when connecting to the adapter, the adapter elastic locking piece is directly extended by the plug frame, to move the plug frame, and the adapter locking piece falls in the suspending part, thereby completing the connecting. With this mechanism, both the frame front part and frame center part of the plug form slopes, more preferably form slopes with constant inclination, whereby the stress increases gradually until the adapter locking piece falls in the suspending part of the plug frame, and it is possible to suppress a decrease in stress to the minimum. 
         [0066]    As a result, the stress does not decrease in the middle when connecting the plug. Thus, the worker who connects the connector plug does not misunderstand that the plug is inserted in the suspending part, thereby preventing the half-way insertion. 
         [0067]    Further, as the 7th clause of JIS C5973, structure, form, and size is defined in  FIG. 1A  through  FIG. 1E , conventional SC connector has a slope angle of a front part of the plug frame of 25° to 35°. Here, the smaller is this slope angle, the smaller is the stress when connecting the flag frame to the adapter. In the optical connector plug of the present invention, however, since the taper part for extraction at a rear part of the plug housing of the conventional SC type connector is not needed, there is an advantage that the slope angle can be made smaller. 
         [0068]    Although the length of the flat part parallel to the movement direction of the plug between the slope part in the frame center portion and the step part of the frame rear portion is defined such that the extended locking piece can be surely mounted to the flat portion in the generally used SC type connector. According to the optical connector plug of the present invention, the length can be shortened to the minimum. As a result, the slope angle can be made to a low angle, and changes in stress can be prevented from being generated. 
       REFERENCE SIGNS LIST 
       [0069]      110  SC type connector plug by conventional technology 
         [0070]      111  slope at tip of plug housing 
         [0071]      112  flat part at tip part of plug housing 
         [0072]      113  slope at rear part of plug housing 
         [0073]      114  suspending part of plug frame 
         [0074]      115 ,  313 ,  513  step part 
         [0075]      120 ,  320 ,  520  adapter 
         [0076]      121 ,  321 ,  521  elastic locking piece 
         [0077]      310  connector plug of patent literature 1 
         [0078]      311  front part of plug frame 
         [0079]      312  flat part of plug frame 
         [0080]      314 ,  514  pulling plate 
         [0081]      510  connector plug of the present invention 
         [0082]      511  tip taper part 
         [0083]      512  central slope 
         [0084]      515  rear flat part 
         [0085]      705  elastic locking piece interval 
         [0086]      801  optical fiber 
         [0087]      802  ferrule 
         [0088]      803  plug frame 
         [0089]      804  shutter housing 
         [0090]      805  shutter 
         [0091]      806  spring