Optical connector

Abstract: To realize an optical connector by which the optical plug can be engaged with the plug adapter firmly even when a large tensile force is applied to the optical cord, the optical connector comprising (a) an adapter housing (311) provided with an inner elastic lever arm (324) axially extending inwardly and having a claw (325) formed with an insertion inclined surface (329), an engage surface (326) and a side projection portion (328) at a free end thereof; (b) a plug housing (315) connected to an end of an optical fiber (317) and coupled to said optical adapter, said plug housing having an outer engage projection (318); and (c) a knob block (316) slidably fitted between said optical adapter and said plug housing, said knob block having an outer release projection (321) formed with an engage inclined surface (319) and a release inclined surface (320).

Description: The present invention relates to an optical connector for removably connecting an optical fiber, and in particular to secure a coupling force against a tensile force applied to the optical cord in connection. Prior to the description of the optical connector, a reference will be made to a prior-art optical connector with reference to the attached drawings. When a plurality of optical cables including optical fibers,respectively are removably coupled,in general an optical connector is used in such a way that an optical plug is connected to an end of an optical fibre, respectively, and the optical fibers are connected to each other with these optical plugs via a plug adapter. A high performance small coupling loss optical connector easily and removably engageable with a plug adapter is disclosed in Japanese Published Unexamined Patent Appli. No. 63-239407, for instance as a single core optical connector. Fig. 1 shows the structure of this single core optical connector. An optical plug 12 is connected to an end portion of an optical cord (fiber) 18. An plug adapter 10 removably engaged with the optical plug 12 includes an adapter housing 10a. Elastic levers 17 are provided within the adapter housing 10a. Each elastic lever 17 is formed with an engage claw 20 and two side projections 17a of the free end thereof. On the other hand, the optical plug 12 includes a ferrule 15, a plug housing 16 formed with an engage projections 18, and a knob block 9 slidably attached to the plug housing 16 and formed with release projections 11. Therefore, when the optical plug 12 is engaged with the plug adapter 10, since the engage claws 20 formed in the elastic levers 17 provided in the plug adapter 10, respectively are brought into contact with the engage projections 18 formed in the plug housing 16 of the optical plug 12, the plug adapter 10 is coupled to the optical plug 12. Reversely, when the optical plug 12 is removed from the plug adapter 10, since the knob block 9 of the optical plug 12 is removed from the adapter housing 10, the release projections 11 formed in the knob block 9 are brought into contact with the side projections 17a to deform the elastic arm 17, so that the engagement between the claws 20 and the engage projections 18 is released to allow the optical plug 12 to be decoupled from the plug adapter 10. Fig. 2 shows an enlarged view showing the prior-art engagement portion of the single core optical connector, in which the engagement between the optical plug 302 and the plug adapter 303 is achieved between the claw 306 of the elastic lever 304 provided in the adapter housing 305 and the engage projection 309 formed at an end of the plug housing 310. Therefore, when the optical plug 302 is pulled in the rightward direction in the drawing, a force is transmitted to the claw 306 via the engage projection 309. In this case, since a point of force application is offset by a distance d from the base portion of the elastic lever 304, a counterclockwise moment M is applied to the elastic lever 304 at the fixed portion of the elastic lever 304. Therefore, when a tensile force between the optical plug 302 and the plug adapter 303 is large, there exist problems in that the free end portion of the elastic lever 304 is bent upwardly, so that the engage surface of the claw 306 slips away from the engage surface of the engage projection 309 into disengagement condition and therefore the optical plug 302 is removed from the plug adapter 303. To overcome this problem, the frictional coefficient between the engage surface of the claw 306 and that of the engage projection 309 has been increased or an angle subtended by the tensile direction of the optical plug 302 and the engage surface between the claw 306 and the engage projection 309 has been determined to be an acute angle, as disclosed in the afore-mentioned document 63-239407. However, when the optical connector is small in size, since the dimensions of the claw 306 and the engage projection 309 are also small, it is rather difficult to obtain a sufficient frictional force between the claw 306 and the engage projection 309. Further, if the angle between the tensile direction and the engage surface (between the claw 306 and the projection 309) is determined to be an acute angle, since a stress is concentrated to these claw 306 and the fixed portion of the engage projection 309 and therefore these parts are easily broken, it has been difficult to prevent the optical plug 302 from being removed from the plug adapter 303. An optical connector in accordance with the invention is defined in claim 1. It is the object of the present invention to provide an optical connector by which the optical plug can be engaged with the plug adapter firmly even when a large tensile force is applied to the optical cord. To achieve the above-mentioned object, each of said first and third housings (352) further comprises an elastic lever arm (357) axially extending forward and inwardly and having a claw (358) formed with an insertion inclined surface, an engage surface, and a side projection at a free end thereof, and the optical connector further comprises: (a) a plug housing (359) connected to an end of an optical fiber (361) and coupled to said housing, said plug housing having an outer engage projection (360); and (b) a knob block (362) slidably fitted between said housing and said plug housing, said knob block having an outer release projection (364) formed with an engage inclined surface and a release inclined surface. When said plug housing (359) is coupled to said housing (352) to outwardly deform said inner lever arm so that said outer engage projection (360) is engaged with the engage surface of said inner elastic arm (357); when said plug housing (359) is decoupled from said first or third housing (352), the release inclined surface of the outer release projection (364) is brought into contact with the side projection of said inner elastic lever arm (357) to outwardly deform said inner lever arm so that said inner elastic arm is disengaged from said engage projection (360). In the optical connector according to the present invention, when the optical plug is inserted into the connector housing, since the engage projections of the optical plug are brought into contact with the claws of the elastic arms provided for the connector housing to deform the elastic arms, the engage surfaces of the engage projections are engaged with the engage surface of the claws. Under these conditions, if the optical cord of the optical plug is pulled, although the force is transmitted to the claws via the engage projections, since the point of force application is offset from the base portion of the elastic arm relative to the connector housing, a moment is generated around the elastic arm in such a direction that the elastic arm end goes toward the optical plug side about the fixed end of the elastic arm. As a result, when a tensile force is applied to the optical cord in the direction that the optical plug is separated from the plug adapter, since the elastic arm end moves toward the optical plug side, the engage surface of the claw is further urged toward the engage surface of the engage projection, thus resulting in secure engagement conditions. On the other hand, when the optical plug is removed from the connector housing: that is when the knob block is gripped and the optical plug is pulled away from the connector housing, since the engage release projections of the blocks push upward the engage release side projections of the elastic arms of the connector housing, the elastic arms are deformed in the direction that the engage projections are removed from the claws. Therefore, when the optical cord is pulled, the optical plug can be removed from the connector housing. Fig. 1 is a perspective, partially broken view showing a prior art push-pull optical connector using an adapter; Fig. 2 is a principle illustration showing the engagement relationship of the prior art optical connector; Figs. 3 to 8 are views for assistance in explaining the present invention; Fig. 3 is a prtially broken, cross-sectional view showing an embodiement in which the optical connector according to the present invention is applied to a push-pull optical connector using an adapter; Fig. 4 is a front view showing the optical plug thereof; Fig. 5 is a plan view of same; Fig. 6 is a left side view of the optical plug shown in Fig. 4. Fig. 7 is a principle illustration showing the engagement relationship of the optical connector; Fig. 8 is a partially broken, cross-sectional view showing another embodiment in which the optical connector according to the present invention is applied to a plug-in optical connector fixed to a back panel; Fig. 3 shows an embodiment of a push-pull type optical connector according to the present invention. Fig. 4 is a front view of the optical plug and Fig. 5 is a plan view thereof. Fig. 6 shows a left side surface of the optical connector shown in Fig. 3. A plug adapter 311 is used to connect two optical plugs 314 under butt conditions. A cylindrical sleeve 312 is fitted to the center of the plug adapter 311. A ferrule 313 is also closely fitted to the cylindrical sleeve 312. An optical plug 314 having the ferrule 313 at one end is formed with a plug housing 315. A square knob block 316 is fitted to the plug housing 315 so as to be slidable within a predetermined range in the axial direction of the optical plug 314. The plug housing 315 to which an optical cord 317 is attached is formed with a pair of engage projections 318 at the inner end thereof. On both sides of these engage projections 318, an engage release projection 321 having an insertion inclined surface 319 and a removal inclined surface 320 is formed for the knob block 316 at the end thereof. The plug adapter 311 includes a coupling flange 322 and a square claw holder 323 into which the optical plug 314 is inserted. The square claw holder 323 is formed with a pair of elastic arms 324 extending axially and inwardly from outside to inside so as to sandwich the optical plug 314. Each elastic arm 324 is formed with a claw 325 engageable with each engage projection 318 of the optical plug 314. An engage surface 326 of this claw 325 is formed facing inward, and an engage surface 327 of the engage projection 318 is formed facing outward. Further, the elastic arm 324 of the optical adapter 311 is formed with two release side portions 328 (shown in Fig. 6) on both the sides of the engage claw 325, respectively so as to be brought into contact with the insertion inclined surface 319 and the removal inclined surface 320 of the engage release projection 321 of the optical plug 314. Therefore, as shown in Fig. 7, when the optical cord 317 is pulled and therefore the plug 314 is pulled in the rightward direction from the optical adapter 311, although the tensile force is applied to the claw 325 via the engage projection 318, since a point of force application is offset inward by a distance d from the fixed portion of the elastic arm 324 extending from the claw holder 323, a counterclock wise moment M is generated around the fixed portion of the elastic arm 324. As a result, when a tensile force is applied so that the optical plug 314 is removed from the plug adapter 311, the free end of the elastic arm 324 is bent inward in the direction that the engage surface 326 of the claw 325 is brought into tight contact with the engage surface 327 of the engage projection 318 to maintain the tight engagement condition between the optical plug 314 and the plug adapter 311. As described above, when a tensile force is applied to the optical cord 317, since the claw 325 is further tightly engaged with the engage projection 318, it is possible to sufficiently increase the coupling strength between the two, without increasing the frictional coefficient between the engage surface 326 of the claw 325 and the engage surface 327 of the engage projection 318 or determining the angle between the optical cord removal direction and the two engage surfaces 326 and 327 at an acute angle. In particular, when the optical connector is small in size, although the dimensions of the engage claw 325 and the engage projection 318 are also small, it is unnecessary to increase the frictional coefficient of the two engage surfaces 326 and 327 or to set the angle between the optical cord removal direction and the two engage surfaces 326 and 327 to an acute angle. Therefore, it is possible to reduce the stress concentration of the claw 325 and the fixed portion of the engage projection 318, thus increasing the strength of the claw 325 and the engage projection 318. When the optical plug 314 is coupled to the plug adapter 311, the knob block 316 is pinched by the fingers and the end surface of the optical plug 314 is inserted into the plug adapter 311. In this case, since the insertion inclined surface 319 of the engage release projection 321 formed at the end of the knob block 316 is brought into contact with the engage release side projection 328 (Fig. 6) of the elastic lever 324, the.free end of the elastic arm 324 is bent away from the engage projection 318. Subsequently, the removal inclined surface 320 is brought into contact with the engage release side projection 328 of the elastic lever 324, so that the knob block 316 is located within the plug adapter 311. In parallel with the above operation, since the engage projection 318 of the optical plug 314 is brought into contact with an insertion inclined surface 329 of the claw 325 (opposite side to the engage surface 326), the free end of the elastic arm 324 is bent away from the engage projection 318. After the engage projection 318 has passed through the claw 325 of the elastic arm 324, the elastic arm 324 is automatically is returned to the original condition to engage the engage projection 318 with the claw 325 of the elastic arm 324. On the other hand, when the optical plug 314 is removed from the plug adapter 311, the knob block 316 is pulled away from the plug adapter 311 in the rightward direction. Therefore, the knob block 316 is moved away from the optical plug 314 together with the optical plug 314 in the rightward direction. In this case, the removal inclined surface 320 of the engage release projection 321 formed at an end of the knob block 316 is brought into contact with the engage release side projection 328 of the elastic arm 324, so that the end of the elastic arm 324 is bent away from the engage projection 318. Therefore, the engagement between the engage projection 318 and the claw 325 is released. Under these conditions, the optical plug 314 can be removed from the plug adapter 311 together with the knob block 316. Further, in this embodiment, in order to prevent the so-called reverse insertion of the optical plug into the plug adapter, the outer shape of the optical plug 314 is formed in asymmetry with respect to the axial center of the ferrule 313. In more detail, as shown in Fig. 6 the plug adapter 311 is formed with a locating groove 330 on one inner side wall thereof and the knob block 316 is formed with a locating projection 331 on one outer side well thereof so as to be engaged with the locating groove 330 as shown in Fig. 4. Further, the widths of the engage release projections 321 formed in the knob block 316 on both the sides thereof as shown in Fig. 5 and the widths of the engage release cutout portions 3 formed in the plug adapter 311 as shown in Fig. 6 are determined to be different between the right and left sides, respectively. In other words, since the coupling orientation between the plug adapter 311 and the optical plug 314 is determined, when the optical plug 314 is inserted into the plug adapter 311 in the opposite erroneous direction, since the wider engage release projection 321 interferes with the plug adapter 311, it is possible to prevent the optical plug 314 from being inserted into the plug adapter in erroneous orientation. In the optical connector according to the present invention, since a distance between the end surface of the ferrule 313 of the optical plug 314 and the engage surface 327 of the engage projection 318 can be reduced smaller than that of the prior-art plug adapter shown in Figs. 1 and 2, it is possible to determine the engage position between the engage projection 318 of the optical plug 314 and the claw 325 of the elastic arm 324 at a position near the inner end of the optical plug 314. Therefore, the optical connector of the present invention is preferably applicable to the plug-in optical connector. Fig. 8 shows another embodiment of the optical connector of the present invention, which is applied to a plug-in optical connector fixed to a back panel side of a book-shelf connector package unit. In the drawing, a main back panel housing 352 (substantially the same in structure as the plug adapter 311 already explained) and a subsidiary back panel housing 353 are attached to a pack panel 351 so as to sandwich the pack panel 351 between the two housings 352 and 353. Into this main back panel housing 352, an optical plug 354 (substantially the same in structure as the optical plug 314 already explained) is removably inserted. The subsidiary back panel housing 353 and the back panel 351 are formed with through holes 355 and 356, respectively through which the optical plug 354 is passed. An elastic arm 357 extends axially and inwardly from the back panel side of the main back panel housing 352. When a claw 358 of the elastic lever 357 is engaged with an engage projection 360 of a plug housing 359, the optical plug 354 is coupled to the main back panel housing 352. In this embodiment, when an optical cord 361 extending from the optical plug 354 is pulled, since the tensile force is applied to the claw 358 of the elastic arm 357 via the engage projection 360 of the plug housing 359, the claw 358 and the engage projection 360 are more tightly engaged with each other as in the embodiment shown in Figs.3 to 6, so that the optical plug 354 is kept coupled with the main back panel housing 352. Further, the well-known structure can be adopted on the package side. Or else, the structure shown in Fig. 3 can be modified as shown in Fig. 8. Further, when the optical plug 354 is removed from the main back panel housing 352, the knob block 362 is moved in the leftward direction in Fig. 8 in the same way as in the embodiment shown in Figs. 3 to 6. As described above, although the optical connector according to the present invention has been applied to the single core optical connector and the plug-in optical connector, it is of course possible to apply the optical connector according to the present invention to other optical connectors. In the optical connector according to the present invention, even if a large tensile force is applied to the optical cord, since the free ends of the elastic arms of the plug adapter are deformed toward the engage projections of the optical plug, it is possible to maintain the tight engagement condition between the engage surfaces of the claws of the elastic arms and the engage surfaces of the engage projections of the optical plug. Further, the optical plug is removed from the plug adapter by simply moving the knob block away from the plug adapter, thus realizing an optical connector of higher tensile strength and excellent coupling/decoupling operability.

Claims: An optical connector, comprising: (a) an adapter housing (311) having a passageway therethrough provided with an inner reflexed elastic canti-lever arm (324) whose free end axially extends inwardly from one end of the passageway and has a claw (325) that projects in a first direction towards the central axis of the passage way and is formed with an insertion surface (329) inclined to the central axis, an engage surface (326) substantially orthogonal to the axis, and has a side projection portion (328) at said free end thereof that projects in a second direction perpendicular to the first direction, (b) a plug housing (315) connected to an end of an optical fiber (317), and that, upon insertion, can be mechanically coupled to said engage surface by means of an outer engage projection (318) so that upon application of an axial force tending to pull the plug out, a moment is generated that causes the free end of the arm to move towards the plug housing; and (c) a knob block (316) partially encasing an end of the plug housing so that on insertion the block is slidable between said optical adapter and said plug housing, said knob block having an outer release projection (321) formed with an engage surface (319) inclined to the axis and a release inclined surface (320) which are arranged to cooperate with the side projection portions of the adapter to disengage the claw from the outer engage projection. The optical connector of claim 1, wherein when said plug housing (315) is coupled to said optical adapter (311), the engage inclined surface (319) of the outer release projection (321) of said knob block (316) is brought into contact with the side projection portion (328) of said inner elastic lever arm (324) of said optical adapter (311) to outwardly deform said inner lever arm to engage said outer engage projection (318) with the engage surface (326) of said inner elastic arm (324); and when said optical plug housing (315) is decoupled from said optical adapter, the release inclined surface (320) of the outer release projection (321) is brought into contact with the side projection portion (328) of said inner elastic lever arm (324) to outwardly deform said inner lever arm to disengage said inner elastic arm (324) from said engage projection (318).

Inventors: ANDO YASUHIRO, IWANO SHIN ICHI, KANAYAMA KAZUNORI, NAGASE RYO, SUGITA ETSUJI, ANDO, YASUHIRO, IWANO, SHIN'ICHI, KANAYAMA, KAZUNORI, NAGASE, RYO, SUGITA, ETSUJI
Applicants: NIPPON TELEGRAPH & TELEPHONE, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Application year: 1990
Main classification: G02B6
IPC codes: H01R13, G02B6