Abstract:
An optical connector device to be used in the field of optical communication between equipments in an office automation system, a factory automation system, an automobile and so on. In this optical connector device, a fitting projection portion of a plug-type optical connector is fitted in a fitting recess in a socket-type optical connector. A latch portion, formed at the plug-type optical connector, is releasably and retainingly engaged with a latch retaining portion formed at the socket-type optical connector. An auxiliary lock mechanism is provided between an inner peripheral surface of the fitting recess and an outer peripheral surface of the fitting projection portion. The auxiliary lock mechanism includes a lock recess and a lock projection which are releasably fitted together when the latch portion is to be engaged with the latch retaining portion.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to an optical connector device to be used in the field of optical communication between equipments in an OA (office automation) system, a FA (factory automation) system, an automobile and so on. 
   2. Background Art 
   One example of optical connector devices, currently used in an automobile, is shown in  FIG. 14 , and this connector device includes a socket-type optical connector  1  and a plug-type optical connector  2  which can be releasably connected together. The socket-type optical connector  1  includes a metal ferrule  4 , mounted on an end portion of an optical fiber cord  3  to hold an end portion of an optical fiber, a socket-type housing  5 , which receives the metal ferrule  4 , and holds this metal ferrule  4  in a predetermined posture, a coil spring  6 , which is mounted within the socket-type housing  5  to resiliently urge the metal ferrule  4  in a predetermined direction, a spring retainer  7 , which is mounted at an end portion of the socket-type housing  5  to retain the coil spring  6  against withdrawal, and a boot  8  which is mounted on the end portion of the socket-type housing  5 , and extends from this end portion to cover the optical fiber cord  3 . 
   Generally similarly, the plug-type optical connector  2  mainly includes a metal ferrule  14 , mounted on an end portion of another optical fiber cord  13  to hold an end portion of an optical fiber, a plug-type housing  15 , which receives the metal ferrule  14 , and holds this metal ferrule  14  in a predetermined posture, a coil spring  16 , which is mounted within the plug-type housing  15  to resiliently urge the metal ferrule  14  in a predetermined direction, a spring retainer  17 , which is mounted at an end portion of the plug-type housing  15  to retain the coil spring  16  against withdrawal, and a boot  18  which is mounted on the end portion of the plug-type housing  15 , and extends from this end portion to cover the optical fiber cord  13 . 
   The plug-type housing  15  of the plug-type optical connector  2  is formed into a narrow, elongate tubular shape, and a sleeve member  19  is received within this housing, and a front end portion of the metal ferrule  14  is fitted in this sleeve member, so that this sleeve member holds the metal ferrule  14  in the predetermined posture. 
   When the front end portion of the plug-type housing  15  is fitted into a fitting recess  5   a  in the socket-type housing  5 , a retaining portion  15   a , formed on an outer peripheral surface of the plug-type housing  5  at the front end portion thereof, is releasably and retainingly engaged with a retaining portion  5   b  formed on the socket-type housing  5 , so that the two housings are connected together. At this time, the front end portion of the metal ferrule  4  is fitted into the other end portion of the sleeve member  19 , so that the two optical fiber cords  3  and  13  are optically coupled together. 
   In this conventional optical connector device, the metal ferrules  4  and  14 , as well as the housings  5  and  15 , are independent, and these independent metal ferrule  4  and  14  are forcibly abutted against each other by the resilient forces of the coil springs  6  and  16 , thereby providing the connector-connected condition which is less liable to be affected by the fitted condition of the retaining portions  5   b  and  15   a  formed respectively on the socket-type housing  5  and plug-type housing  15 . However, the number of the component parts, including the metal ferrules  4  and  14 , the coil springs  6  and  16  and the spring retainers  7  and  17 , is large, and therefore there has been encountered a problem that the assembling operation requires much time and labor, and is cumbersome. 
   Therefore, there has been proposed the type of optical connector device in which a ferrule portion for holding an end portion of an optical fiber is formed integrally with each of a socket-type optical connector and a plug-type optical connector in order to reduce the number of the component parts and to reduce the time and labor for the assembling operation. In such an optical connector device, when a fitting projection portion of the plug-type optical connector is fitted into a fitting recess in the socket-type optical connector, a latch portion, provided at the plug-type optical connector, is releasably and retainingly engaged with a latch retaining portion, provided at the socket-type optical connector, and therefore the end surfaces of the two optical fibers are connected together in a butting manner, so that the two optical fiber cords are optically coupled together. 
   In this kind of optical connectors, there is used the system in which the end surfaces of the optical fibers are connected together in a butting manner, thereby securing a passage for light, and therefore a light loss, developing in the connected condition of the optical connectors, is much influenced by the butt-connected condition of the optical fiber end surfaces. 
   In the structure of connecting the socket-type and plug-type optical connectors each having the integral ferrule portion, the latch portion can be elastically deformed and moved to be releasably and retainingly engaged with the latch retaining portion, and therefore a relative shaking movement between the two optical connectors is liable to occur in the connected condition. There has been encountered a problem that the dimensional tolerances must be strictly controlled in order to stabilize and reduce the light loss in the connected condition. 
   SUMMARY OF THE INVENTION 
   With the above problems in view, it is an object of this invention to provide an optical connector device in which a relative shaking movement in a connected condition is prevented so as to stabilize a light loss. 
   Technical means for solving the above problems is directed to an optical connector device wherein a fitting projection portion of a plug-type optical connector is fitted in a fitting recess in a socket-type optical connector, and a latch portion, formed at the plug-type optical connector, is releasably and retainingly engaged with a latch retaining portion formed at the socket-type optical connector; and wherein an auxiliary lock mechanism is provided between an inner peripheral surface of the fitting recess and-an outer peripheral surface of the fitting projection portion, and the auxiliary lock mechanism includes a lock recess and a lock projection which are releasably fitted together when the latch portion is retainingly engaged in the latch retaining portion. 
   Preferably, the lock recess and the lock projection of the auxiliary lock mechanism have such an automatically-fitting structure that the lock recess and the lock projection are led in the mutually-fitting direction at the time when the operation of retaining engagement between the latch retaining portion and the latch portion is completed. 
   Preferably, a length of the lock projection in the direction of fitting of the fitting projection portion is larger than a length of the lock recess. 
   Preferably, a front portion of the lock projection with respect to the direction of fitting of the fitting projection portion is gently slanting while a rear portion of the lock projection with respect to the direction of fitting of the fitting projection portion is abruptly slanting. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an end view of a socket-type optical connector of a first embodiment of the invention. 
       FIG. 2  is an end view of a plug-type optical connector of the first embodiment. 
       FIG. 3  is a view explanatory of a fitting operation, showing the cross-section of the socket-type optical connector taken along the line A—A of  FIG. 1  as well as the cross-section of the plug-type optical connector of  FIG. 2  taken along the line B—B of FIG.  2 . 
       FIG. 4  is a cross-sectional view showing a fitted condition. 
       FIG. 5  is an explanatory view showing a condition immediately before the operation of retaining engagement between a latch retaining portion and a latch portion is completed. 
       FIG. 6  is a cross-sectional view of a lock projection portion, showing a condition immediately before the operation of retaining engagement between the latch retaining portion and the latch portion is completed. 
       FIG. 7  is a cross-sectional view showing a condition in which the lock projection is fitted in a lock recess. 
       FIG. 8  is a cross-sectional view showing a second embodiment. 
       FIG. 9  is a view explanatory of the process of fitting a lock projection into a lock recess. 
       FIG. 10  is a view explanatory of the process of fitting the lock projection into the lock recess. 
       FIG. 11  is a view explanatory of the process of fitting the lock projection into the lock recess. 
       FIG. 12  is a cross-sectional view of an important portion of a third embodiment. 
       FIG. 13  is a cross-sectional view of an important portion of a fourth embodiment. 
       FIG. 14  is a cross-sectional view showing a conventional example. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first embodiment of the present invention will now be described with reference to the drawings. As shown in  FIGS. 1  to  4 , an optical connector device includes a plug-type optical connector  31  for holding end portions of optical fiber cords  30 , and a socket-type optical connector  34  for holding end portions of optical fiber cords  33  to be optically coupled respectively to the optical fiber cords  30 . When the plug-type optical connector  31  and the socket-type optical connector  34  are connected together, the optical fiber cords  30  are optically coupled respectively to the optical fiber cords  33 . 
   Each of the optical fiber cords  30  and  33  includes an optical fiber  30   a ,  33   a  (comprising a core and a cladding), and a sheath  30   b ,  33   b  formed on an outer periphery of the optical fiber to cover the same. When the optical fiber cord is to be held in the plug-type optical connector  31  or the socket-type optical connector  34 , the sheath  30   b ,  33   b  is beforehand removed from the end portion of the optical fiber cord  30 ,  33  over a predetermined length, so that the optical fiber  30   a ,  33   a  within the optical fiber cord is exposed. 
   The plug-type optical connector  31  mainly includes a housing body  36  of a generally square tubular shape made of an elastic resin or the like, and cord receiving hole portions  38 , into which the optical fiber cords  30  are inserted and received, respectively, in the axial direction, are formed in this housing body  36 . 
   Ferrule portions  40  of a generally cylindrical tubular shape each for holding the corresponding optical fiber  30   a , exposed at the end portion of the optical fiber cord  30 , are formed integrally at a front end of the housing body  36  (at which the end portions of the optical fiber cords  30 , inserted in the respective cord receiving hole portions  38 , are disposed), and project forwardly from this front end, and an optical fiber receiving hole portion  40   a  is formed in each ferrule portion  40 . 
   A surrounding wall portion is formed on the housing body  36 , and surrounds the ferrule portions  40  in suitably-spaced relation to outer peripheral surfaces thereof, and this surrounding wall portion forms a fitting projection portion  44  which can be releasably fitted into a fitting recess  42  formed in the socket-type optical connector  34 . 
   The inner diameter of the cord receiving hole portion  38  is so sized as to pass the sheath  30   b  of the optical fiber cord  30  therethrough, and the inner diameter of the optical fiber receiving hole portion  40   a  is so sized as to pass the optical fiber  30   a  therethrough. 
   When each optical fiber cord  30  is inserted into the corresponding cord receiving hole portion  38  from the rear side to be received therein, the sheath  30   b  of the optical fiber cord  30  is received in the cord receiving hole portion  38  while the optical fiber  30   a  is received in the optical fiber receiving hole portion  40   a . When the optical fiber  30   a  is thus received in the optical fiber receiving hole portion  40   a , the optical fiber  30   a  is held in this hole portion in a radially-positioned manner. The end surface of the optical fiber  30   a  is suitably processed into a specular surface at the distal end of the ferrule portion  40 . 
   The optical fiber cord  30 , received in the cord receiving hole portion  38 , is held therein against withdrawal by conventional means such as an adhesive or a suitable stopper structure. 
   An engagement extension piece portion  46  is formed on the upper side of the housing body  36 , and extends rearward from the fitting projection portion  44  in a cantilever manner. A latch portion  50  is formed on the engagement extension piece portion  46  intermediate opposite ends thereof, and this latch portion  50  can be releasably and retainingly engaged with a latch retaining portion  48  formed within the fitting recess  42  of the socket-type optical connector  34 . When the plug-type optical connector  31  and the socket-type optical connector  34  are to be connected together, the engagement extension piece portion  46  is elastically deformed downwardly so as to retainingly engage the latch portion  50  with the latch retaining portion  48 . 
   Guide ridges  52  are formed respectively on lower portions of opposite side surfaces of the housing body  36 , and guide grooves  54  are formed respectively in lower portions of opposed side surfaces of the fitting recess  42 , and during the time when the plug-type optical connector  31  and the socket-type optical connector  34  are connected together, the guide ridges  52  are slidingly guided by these guide grooves  54 , respectively. 
   The socket-type optical connector  34 , like the plug-type optical connector  31 , is made of an elastic resin or the like, and mainly includes a housing body  56  of a generally square tubular shape made of an elastic resin or the like, and a fiber holding member  60  fitted in a receiving hole portion  58  in the housing body  56 . The fitting recess  42  is formed in one end portion of the housing body  56 , and the receiving hole portion  58  is formed in the other end portion thereof. 
   Cord receiving hole portions  62 , into which the optical fiber cords  33  are inserted and received, respectively, in the axial direction, are formed in the fiber holding member  60 . Ferrule portions  64  of a generally cylindrical tubular shape each for holding the corresponding optical fiber  33   a , exposed at the end portion of the optical fiber cord  33 , are formed integrally at that end of the fiber holding member  60  (at which the end portions of the optical fiber cords  33 , inserted in the respective cord receiving hole portions  62 , are disposed), and project forwardly from this end, and an optical fiber receiving hole portion  64   a  is formed in each ferrule portion  64 . 
   The inner diameter of the cord receiving hole portion  62  is so sized as to pass the sheath  33   b  of the optical fiber cord  33  therethrough, and the inner diameter of the optical fiber receiving hole portion  64   a  is so sized as to pass the optical fiber  33   a  therethrough. 
   Ferrule portion-holding holes  66  of a circular shape are formed in an axially-central portion of the housing body  56 , and the corresponding ferrule portion  40  of the housing body  36  and the corresponding ferrule portion  64  of the fiber holding member  60  can be fitted and received in each ferrule portion-holding hole  66 . 
   When each optical fiber cord  33  is inserted into the corresponding cord receiving hole portion  62  from the rear side to be received therein, the sheath  33   b  of the optical fiber cord  33  is received in the cord receiving hole portion  62  while the optical fiber  33   a  is received in the optical fiber receiving hole portion  64   a . When the optical fiber  33   a  is thus received in the optical fiber receiving hole portion  64   a , the optical fiber  33   a  is held in this hole portion in a radially positioned manner. The end surface of the optical fiber  33   a  is suitably processed into a specular surface at the distal end of the ferrule portion  64 . 
   The optical fiber cord  33 , like the optical fiber cord  30 , is held in the cord receiving hole portion  62  against withdrawal by suitable means such as an adhesive or a stopper structure. 
   In this condition, the fiber holding member  60  is mounted in the receiving hole portion  58 , and in this mounted condition the ferrule portions  64  are fitted and held in one end portions of the ferrule portion-holding holes  66 , respectively. 
   In this embodiment, lock projections  70 , each bulging into an generally arcuate shape, are formed on the lower side of the outer peripheral surface of the fitting projection portion  44  of the plug-type optical connector  31 , as best shown in  FIGS. 6 and 7 . Hole-like lock recesses  72  are formed in the corresponding lower side of the inner peripheral surface of the fitting recess  42  in the socket-type optical connector  34 . 
   The lock recesses  72  and lock projections  70  are of such an automatically-fitting structure that each lock recess  72  and the corresponding lock projection  70  are led in their mutually-fitting direction by the resilient force of the material (of which the plug-type optical connector  31  and the socket-type optical connector  34  are made) immediately before or after the retaining engagement of the latch portion  50  with the latch retaining portion  48  is completed at the time of fitting the fitting projection portion  44  in the fitting recess  42 , as shown in FIG.  5 . 
   As shown in  FIG. 7 , the length L of the lock projection  70  in the direction P of fitting of the fitting projection portion  44  is larger than the length S of the lock recess  72  in this fitting direction. 
   The lock projections  70  and the lock recesses  72  jointly form an auxiliary lock mechanism. 
   Guide grooves  74  each for guiding the sliding movement of the corresponding lock projection  70  during the fitting of the fitting projection portion  44  are formed in the lower surface of the fitting recess  42 . 
   As the fitting projection portion  44  of the plug-type optical connector  31  is fitted into the fitting recess  42  in the socket-type optical connector  34 , the two guide ridges  52  are guided along the two guide grooves  54 , respectively, and thereafter the ferrule portions  40  are fitted into the ferrule portion-holding holes  66 , respectively. Then, the engagement extension piece portion  46  is elastically deformed as shown in  FIG. 5 , and when the operation of retaining engagement between the upper-side latch portion  50  and latch retaining portion  48  is completed, each lower-side lock projection  70  is mostly fitted in the corresponding lock recess  72 , and is in an automatically-fitting condition so as to be led in the fitting direction, as shown in FIG.  6 . 
   Then, when the latch portion  50  passes past the latch retaining portion  48 , the engagement extension piece portion  46  is elastically restored, so that there is obtained the retained condition in which the latch portion  50  and the latch retaining portion  48  are locked to each other against disengagement from each other, as shown in FIG.  4 . At this time, each lock projection  70  is completely fitted in the corresponding lock recess  72 , so that the locked condition is also obtained at the lower side, as shown in FIG.  4 . 
   In this fitted locked condition, within each ferrule portion-holding hole  66 , the optical fiber  30   a , held in the ferrule portion  40 , and the optical fiber  33   a , held in the ferrule portion  64 , are abutted against each other in such a manner that the axes of these optical fibers  30   a  and  33   a  coincide with each other, and therefore the two optical fiber cords  30  and  33  are optically coupled together. 
   As described above, in this embodiment, the connected condition of the plug-type optical connector  31  and socket-type optical connector  34  is maintained not only by the retaining or locking engagement between the latch portion  50  and the latch retaining portion  48  (as in the conventional construction) but also by the locking engagement between each lock projection  70  and the corresponding lock recess  72 , and therefore the two optical connectors are locked to each other at the plurality of portions, and with this construction the connected condition of the optical connectors  31  and  34  is more firm, and the mechanical strength in the locked condition can be increased, and besides a relative shaking movement between the optical connectors in the connected condition can be effectively prevented, and the light loss can be stabilized in the connected condition. 
   The auxiliary lock mechanism is constituted by the ridge-like lock projections  70  and the lock recesses  72  in which the lock projections  70  can be fitted, respectively, and these portions are not movable in contrast with the latch portion  50 , and therefore the control of the dimensional tolerances is relatively easy, and in this respect, also, the light loss can be stabilized. 
   And besides, at the time when the operation of retaining engagement between the latch portion  50  and the latch retaining portion  48  is completed, each lock projection  70  is automatically fitted into the corresponding lock recess  72 , and therefore in the condition in which the latch portion  50  is retainingly engaged with the latch retaining portion  48 , the fitting projection portion  44  is urged in the fitting direction P by the automatically-fitting structure of the lock projections  70  and lock recesses  72 , and in this respect, also, the relative shaking movement is effectively prevented, and besides the end surfaces of the two optical fibers  30   a  and  33   a  are urged in such a direction as to be abutted against each other, and the abutting distance can be reduced, and the light loss can be reduced and stabilized. 
   The length L of the lock projection  70  is larger than the length S of the lock recess  72 , and therefore when the lock projection  70  is fitted in the lock recess  72 , no gap is formed therebetween as shown in  FIG. 7 , so that the more firmly-locked condition is obtained, and each optical connector is effectively prevented from moving in the fitting direction P and the opposite direction, and in this respect, also, the relative shaking movement can be effectively prevented. 
     FIGS. 8  to  11  show a second embodiment, and those constituent portions, similar to those of the first embodiment, will be designated by identical reference numerals, respectively, and explanation thereof will be omitted. 
   Namely, the first embodiment is directed to the relay optical connectors  31  and  34 , in which each mating pair of optical fiber cords  30  and  33  are connected together, while this embodiment is directed to optical connectors  31  and  34  in which optical fiber cords  30  are optically coupled respectively to optical elements  76  such as a light-receiving element or a light-emitting element. 
   In this embodiment, as shown in  FIGS. 9  to  11 , each lock projection  70 , formed in a bulged manner on a lower surface of a fitting projection portion  44 , has such a shape that a front portion  70   a  of this lock projection  70  with respect to a direction P of fitting of the fitting projection portion  44  is gently slanting while a rear portion  70   b  thereof with respect to the fitting direction P is abruptly slanting. There is provided such an automatically-fitting structure that at the time when the retaining engagement of a latch portion  50  with a latch retaining portion  48  is completed, the abruptly-slanting rear portion  70   b  is disposed at a peripheral edge of a lock recess  72  as shown in  FIG. 10 , and the lock recess  72  and the lock projection  70  are led in their mutually-fitting direction. 
   Therefore, in this embodiment, when the fitting projection portion  44  of the plug-type optical connector  31  is fitted into a fitting recess  42  in the socket-type optical connector  34 , the lock projections  70  are guided along guide grooves  74 , respectively, and each lock projection is gently engaged with the lock recess portion because of the gently-slanting surface of the fitting direction (P)-front portion  70   a , as shown in FIG.  9 . 
   Then, at the time when the operation of retaining engagement between the latch portion  50  and the latch retaining portion  48  is completed, the lock projection is automatically led in the fitting direction P, so that the lock projection is abruptly fitted into the lock recess because of the abruptly-slanting surface of the fitting direction (P)-rear portion  70   b.    
   Therefore, this embodiment achieves the effects similar to those of the first embodiment, and even when a pulling fore acts on the optical fiber cord  30  to apply a force tending to withdraw the optical connectors  31  and  34  from each other, the fitted condition is easily restored, and the increase of the light loss can be effectively prevented, and the light loss can be stabilized. 
     FIG. 12  shows a third embodiment, and those constituent portions, similar to those of the second embodiment, will be designated by identical reference numerals, respectively, and explanation thereof will be omitted. 
   Namely, in this embodiment, each of a gently-slanting front portion  70   a  and a steeply-slanting rear portion  70   b  of each lock projection  70  is formed into a straight configuration. 
   This embodiment achieves effects similar to those of the second embodiment. 
     FIG. 13  shows a fourth embodiment, and those constituent portions, similar to those of the first embodiment, will be designated by identical reference numerals, respectively, and explanation thereof will be omitted. 
   Namely, in this embodiment, each lock projection  70  has a generally rectangular cross-section, and a peripheral edge portion of a corresponding lock recess  72  has slanting surfaces  72   a  which form the above automatically-fitting structure. 
   This embodiment also achieves effects similar to those of the first and second embodiments. 
   Although the optical connectors  31  and  34  of the above embodiments are of the two-pole type, the invention can be applied also to connectors of the single-pole or the multi-pole type. 
   As described above, in the optical connector device of the present invention, the auxiliary lock mechanism is provided between the inner peripheral surface of the fitting recess and the outer peripheral surface of the fitting projection portion, and the auxiliary lock mechanism includes the lock recess and the lock projection which are releasably fitted together when the latch portion is retainingly engaged in the latch retaining portion. Therefore, the two optical connectors are locked to each other at the plurality of portions, and with this construction the connected condition of the optical connectors is more firm, and the mechanical strength in the locked condition can be increased, and besides a relative shaking movement between the optical connectors in the connected condition can be effectively prevented, and the light loss can be stabilized in the connected condition. Furthermore, the auxiliary lock mechanism is constituted by the lock projection and the lock recess in which the lock projection can be fitted, and these portions are not movable, and therefore the control of the dimensional tolerances is relatively easy, and in this respect, also, there is achieved an advantage that the light loss can be stabilized. 
   The lock recess and the lock projection of the auxiliary lock mechanism have such an automatically-fitting structure that the lock recess and the lock projection are led in the mutually-fitting direction at the time when the operation of retaining engagement between the latch retaining portion and the latch portion is completed. In this case, when the latch portion is retainingly engaged with the latch retaining portion, the fitting projection portion is urged in the fitting direction, and in this respect, also, there is achieved an advantage that the relative shaking movement is effectively prevented, and besides there is achieved an advantage that the end surfaces of the two optical fibers or the like to be optically coupled together are urged in such a direction as to be abutted against each other, and the abutting distance can be reduced, and the light loss can be reduced and stabilized. 
   The length of the lock projection in the direction of fitting of the fitting projection portion is larger than the length of the lock recess. In this case, when the lock projection is fitted in the lock recess, no gap is formed therebetween, so that the more firmly-locked condition is obtained, each optical connector is effectively prevented from moving in the fitting direction and the opposite direction, and in this respect, also, there is achieved an advantage that the relative shaking movement can be effectively prevented. 
   The front portion of the lock projection with respect to the direction of fitting of the fitting projection portion is gently slanting while the rear portion of the lock projection with respect to the direction of fitting of the fitting projection portion is abruptly slanting. In this case, even when there is applied a force tending to withdraw the two optical connectors from each other, the fitted condition is easily restored, and the increase of the light loss can be effectively prevented, and in this respect, also, there is achieved an advantage that the light loss can be stabilized.