Method of stacking ferrules of a stacked-type optical connector and a stacked-type optical connector

Abstract: A method for stacking ferrules of a stacked-type optical connector wherein stacking portions for stacking are provided in corresponding positions of each ferrule (11), the individual ferrules (11) are stacked with the corresponding individual stacking portions aligned, and a plurality of ferrules are simultaneously stacked up with stacking members (12, 12) which work in cooperation with those corresponding stacking portions in such a manner that the ferrules (11) can substantially float with a specific degree of freedom to allow a gap between the ferrules (11), and a stacked-type optical connector assembled according to this method.

Description: The present invention relates to a method of stacking ferrules of a stacked-type optical connector, and a stacked-type optical connector. A prior art optical connector used for butt-connecting individual optical fibers of optical communication lines has a ferrule 2 and a single or multi optical fiber 3 like, for example, an optical connector 1 as shown in FIG. 29, the multi optical fiber 3 being installed on a main body 2a with the individual optical fibers 3a exposed at a butting end surface 2b of the main body 2a. The ferrule 2 has pin holes 2c and 2c provided on either side with the multi optical fiber 3 of the main body 2a between them, and it is butt-connected to a ferrule of another optical connector having the same configuration by inserting connecting pins, which are not shown, in the individual pin holes 2c. To butt-connect the optical connector 1 simultaneously with a plurality of other optical connectors, it is necessary to form a plurality of optical connectors 1 into one piece. A method described in, for example, Japanese Unexamined Patent Publication (Kokai) No. 2-297506, is known as a method of forming the optical connectors 1 into one piece. In a known electrical connector shown in Figs. 3 and 4 of US-A-3,920,309 the individual connectors are firmly screwed together, but some free play is provided by flexible female contact pins. However, when a plurality of optical connectors are assembled into one piece according to the aforementioned method, a stacking housing of a complicated shape with a plurality of inserting holes formed in it is required, and there are partitions taking an extra space between ferrules on the stacking housing. This presents a problem of a lower packaging density of an optical connector, hindering the achievement of a reduced size. When consolidating optical connectors, conventionally, a plurality of optical connectors were rigidly fixed to a stacking housing or the like in some cases. However, there were some cases where the positions of the pin holes 2c and 2c in an optical connector were not aligned with those in its matching optical connector due to a manufacturing error or the like. This presented a problem of prohibiting smooth butt-connection because when a plurality of optical connectors were rigidly stacked and a stacked-type optical connector in a stack was butt-connected with its mating stacked-type optical connector, the aforementioned connecting pins could not be inserted in the pin holes or the pin holes were damaged. Viewed from one aspect, the present invention provides a method of forming a stacked-type optical connector according to claim 1. Viewed from another aspect, the present invention provides a stacked-type optical connector according to claim 13 whose preamble is based on JP-A-2-297506. According to the method of forming a stacked-type optical connector of the present invention, a plurality of ferrules can be stacked easily and compactly with a high density. Further, a stacked-type optical connector assembled using this method can be made smaller, and the time required for simultaneously connecting with other stacked-type optical connectors can be reduced. Further, a plurality of ferrules are stacked so that they are allowed to float, therefore, they can move with a specific degree of freedom when butt-connecting the stacked-type optical connectors, and the centers of the connecting pins and pin holes are automatically aligned, permitting smooth connection between the stacked-type optical connectors. Furthermore, the stacking members used for stacking the ferrules have a simple structure and can be provided at a low cost. Adding the stacking portions to existing ferrules enables easy application of the present invention, permitting easy manufacture of the stacked-type optical connectors. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:- FIG. 1 is a front view of a stacked-type optical connector formed by stacking ferrules, illustrating a first embodiment related to a method for stacking the ferrules of a stacked-type optical connector, and a stacked-type optical connector; FIG. 2 is a plan view of an optical connector before it is stacked, which constitutes the stacked-type optical connector; FIG. 3 is a perspective illustration of a stacking pin used for stacking ferrules; FIG. 4 is a left side view of a stacked-type optical connector formed by stacking ferrules; FIG. 5 is a plan view of the stacked-type optical connectors of FIG. 1 which are butt-connected; FIG. 6 is a side view of the stacked-type optical connectors of FIG. 5; FIG. 7 is a plan view of an optical,connector before it is stacked , illustrating a second embodiment of the present invention; FIG. 8 is a front view of the stacking pin used for stacking the ferrules of the optical connector shown in FIG. 7; FIG. 9 is a front view of a stacked-type optical connector with ferrules stacked using the optical connector shown in FIG. 7; FIG. 10 is a plan view of the stacked-type optical connector shown in FIG. 9; FIG. 11 is a right side view of the stacked-type optical connector shown in FIG. 9; FIG. 12 is a plan view of the optical connector before it is stacked illustrating a third embodiment of the present invention; FIG. 13 is a perspective illustration of a coupling clip used for stacking the ferrule of the optical connector shown in FIG. 12; FIG. 14 is a front view of the stacked-type optical connector wherein a plurality of the ferrules of the optical connector shown in FIG. 12 are stacked with the coupling clip; FIG. 15 is a plan view of the stacked-type optical connector shown in FIG. 14; FIG. 16 is a perspective view of an elastic cap used for stacking the ferrules of a plurality of optical connectors, illustrating a fourth embodiment of the present invention; FIG. 17 is a perspective view of the elastic cap to be fitted a plurality of pinching portions of the stacked ferrules; FIG. 18 is a plan view of the stacked-type optical connector with the elastic cap fitted to the pinching portions of the stacked ferrules; FIG. 19 is a front view of FIG. 18; FIG. 20 is a perspective view of an optical connector constituting a stacked-type optical connector, illustrating a fifth embodiment of the present invention; FIG. 21 is a front view of a stacked-type optical connector assembled by stacking the optical connector shown in FIG. 20; FIG. 22 is a right side view of the stacked-type optical connector shown in FIG. 21; FIG. 23 is a perspective view of an adapter used for butt-connecting the stacked-type optical connector shown in FIG. 21 with another one; FIG. 24 is a cross-sectional view showing an enlarged view of a major section of the optical connector and the adapter in an initial phase of the butt-connection between the stacked-type optical connectors shown in FIG. 21; FIG. 25 is a cross-sectional view showing an enlarged view of a major section of the front section of the optical connector fitted to the adapter in the butt-connection of the stacked-type optical connectors; FIG. 26 is a cross-sectional view showing an enlarged view of a major section of the butted optical connectors in the butt-connection of the stacked-type optical connectors; FIG. 27 is a plan view of both stacked-type optical connectors with a clip on to keep them connected after the adapter is removed from the two butted stacked-type optical connectors; FIG. 28 is a perspective view showing another optical connector which constitutes a stacked-type optical connector; and FIG. 29 is a perspective view of an optical connector used for a method for stacking ferrules of a conventional stacked-type optical connector. FIG. 1 through FIG. 6 illustrate the first embodiment of the present invention, the stacked-type optical connector being assembled by simultaneously stacking individual ferrules 11 of five optical connectors 10 with stacking pins 12. In the optical connector 10, as shown in FIG. 2, a tape fiber 13 composed of a plurality of optical fibers which are covered and formed into a tape-like shape is installed on a main body 11a of a ferrule 11, and a part extending from the rear of the main body 11a is protected by a boot 14. The ends of the individual optical fibers 13a of the tape fiber 13 are exposed on a butting end surface 11b. Further, the main body 11a is stepped and protrudes in its front half, and on either side of its width are provided pin holes 11c for connecting pins. In the rear of the main body 11a, outside the pin holes 11c. there are stacking holes 11d which extend vertically therethrough, and these stacking holes 11d constitute the stacking portions. In the method for stacking the ferrules of a stacked-type optical connector according to this embodiment, using the aforementioned optical connector 10, five ferrules 11, for example, are stacked as described below. First, the five ferrules 11 are stacked up so that all pairs of the stacking holes 11d are aligned. Then, from above the stacked ferrules 11, the stacking pins 12 shown in FIG. 3 are inserted in the individual stacking holes 11d. The stacking pin 12, as shown in the drawing, has a head 12a secured on the top surface of the main body 11a of the ferrule 11 and a pin shank 12b which is inserted in the stacking hole 11d, and it also has a concave groove 12c which is formed circumferentially near the bottom end of the pin shank 12b and at a height that is slightly greater than the overall thickness of all the five ferrules 11 stacked. Then, a snap ring 15 such as a circular clip is fitted to the concave groove 12c of each stacking pin 12 jutting out downward from the bottom ferrule 11 so that it comes in contact with the bottom surface of the ferrule 11. This assembles the five optical connectors 10 into a stacked-type optical connector with compactly stacked ferrules 11 as shown in FIG. 1 and FIG. 4. The stacking pin 12 inserted in each stacking hole 11d does not come out of each ferrule 11 even if it is subjected to a force withdrawing it upwards because the snap ring 15 is fitted to the concave groove 12c. To butt-connect the stacked-type optical connector with another stacked-type optical connector, a connecting pin not shown is inserted in a pin hole 11c of the ferrule 11 of one stacked-type optical connector, the butting end surfaces 11b of the individual ferrules 11 are butted, and the connecting pin is inserted in a matching pin hole 11c of the butted ferrule 11 so that it extends over both pin holes 11c and 11c. In this case, the individual ferrules 11 of the stacked-type optical connectors are stacked to allow the individual ferrules 11 to substantially float in the axial direction of the stacking pins 12 with a specific degree of freedom so that a small gap is allowed between the ferrules 11. Thus, when the connecting pins inserted in the individual pin holes 11c of one ferrule 11 are inserted in the pin holes 11c of the matching ferrule 11, the ferrules 11 slightly float for the aforementioned gap in the axial direction of the stacking pins 12. Therefore, the centers of the matching pin holes 11c with respect to the connecting pins are automatically aligned, ensuring smooth connection between the matching ferrules 11 and 11. In this way, the stacked-type optical connectors with a plurality of ferrules 11 stacked are butt-connected by inserting connecting pins 16 (See FIG. 5) in the matching pin holes 11c and 11c of the individual ferrules 11 as shown in FIG. 5 and FIG. 6, and to their side surfaces are attached leaf springs 17 and 17 for holding the two stacked-type optical connectors connected. The butt-connected stacked-type optical connectors can be easily separated into individual stacked-type optical connectors by removing the leaf springs 17 and 17. Further, each stacked-type optical connector can be easily separated into individual optical connectors 10 by removing the snap ring 15 and drawing the stacking pins 12 out of the stacking holes 11d. When simultaneously stacking a plurality of ferrules 11 according to the foregoing method, no wasteful space is produced between stacked ferrules 11 of the stacked-type optical connectors, making it possible to compactly stack a plurality of ferrules 11 with a high packaging density. Furthermore, the ferrules 11 permit easy machining of the stacking holes 11d which constitute the stacking portions, and the stacking pins 12 have circular cross-sections, therefore, inexpensive stacked-type optical connectors can be provided. FIG. 7 through FIG. 11 illustrate the second embodiment of the present invention wherein a ferrule 21 of an optical connector 20 is stacked to form a stacked-type optical connector with a U-shaped stacking pin 22. In the optical connector 20, as shown in FIG. 7, a tape fiber 23 is installed on a main body 21a of a ferrule 21, and a part extending from the rear of the main body 21a is protected by a boot 24. The ends of the individual optical fibers 23a are exposed on a butting end surface 21b. Further, on either side of the width of the main body 21a are provided pin holes 21c and 21c for connecting pins. In the rear of the main body 21a, outside the pin holes 21c and 21c, there are stacking holes 21d and 21d which extend vertically therethrough and which constitute the stacking portions. The stacking pin 22 is a U-shaped pin consisting of a bridge 22a with inserting shanks 22b and 22b on either end of the bridge as shown in FIG. 8. Concave grooves 22c are formed circumferentially near the bottom ends of the inserting shanks 22b, at a height which is slightly greater than the overall thickness of all the ferrules 21 stacked. To stack, for example, five such optical connectors 20, they are first stacked so that the stacking holes 21d and 21d of the ferrules 21 are aligned. Then, the inserting shanks 22b of the stacking pin 22 are inserted in the matching stacking holes 21d from above the stacked ferrules 21 so that the bridge 22a extends from one stacking hole 21d to the other stacking hole 21d. After that, snap rings 25 are fitted to concave grooves 22c of each stacking pin 22 jutting out downward from the bottom ferrule 21 so that they come in contact with the bottom surface of the ferrule 21. This assembles the five optical connectors 20 into a stacked-type optical connector with compactly stacked ferrules 21 as shown in FIG. 9 or FIG. 11. The stacking pin 22 with its inserting shanks 22b inserted in the matching stacking holes 21d does not come out of each ferrule 11 even if it is subjected to a force withdrawing it upwards because the snap rings 25 are fitted to the concave grooves 22c. The stacked-type optical connectors with a plurality of ferrules 21 stacked up as described above can be easily butt-connected by inserting a connecting pin (not shown) into the matching pin holes 21c and 21c of each ferrule 21 so that the pin extends over the pin holes as in the first embodiment. In this case, the individual ferrules 21 of the stacked-type optical connectors are stacked so that the ferrules substantially float with a specific degree of freedom in the axial direction of the inserting shanks 22b of the stacking pins 22 to allow a small gap between the ferrules 21. Thus, when the connecting pins inserted in the individual pin holes 21c of one ferrule 21 are inserted in the pin holes 21c of the other ferrule 21, the ferrules 21 float in the axial direction of each inserting shank 22b. As a result, the centers of the matching pin holes 21c with respect to the connecting pins are automatically aligned, ensuring smooth connection between the matching ferrules 21 and 21. The butt-connected stacked-type optical connectors can be easily separated into individual stacked-type optical connectors simply by detaching them. Further, each stacked-type optical connector can be easily separated into individual optical connectors 20 by removing the snap rings 25 from the concave grooves 22c and drawing the stacking pin 22 upwards and out, thereby pulling the inserting shanks 22b and 22b out of the stacking holes 21d and 21d. According to the present embodiment, a plurality of ferrules 21 can be easily and compactly stacked to form a stacked-type optical connector, and further, the number of the ferrules 21 to be stacked can be changed by changing the length of the inserting shanks 22b. Further, compared with the foregoing embodiment, the number of stacking pins 22 is only one, resulting in fewer components required and also a shorter working time because one insertion allows a stacking pin to be inserted in two stacking holes. The third embodiment of the present invention is now described with reference to FIG. 12 through FIG. 15. As shown in FIG. 12, an optical connector 30 has a ferrule 31 and a tape fiber 32 whose end is attached to the ferrule 31, a part of the tape fiber 32 which extends from the rear of the ferrule 31 being protected with a boot 33. Individual optical fibers 32a of the tape fiber 32 are exposed on the butting end surface 31b which projects at the front of a main body 31a of the ferrule 31. On either side of the width of the main body 31a are provided pin holes 31c and 31c in which connecting pins are inserted for butt-connecting the optical connector with another optical connector. Concave stacking grooves 31d and 31d which constitute stacking portions are provided in the sides at the rear. In this embodiment, the optical connector 30 having the foregoing configuration is stacked with a coupling clip 34 shown in FIG. 13. The coupling clip 34 is made of metal or synthetic resin, and it has a bridge 34a arranged over the top surface of the ferrule 31, and holding sections 34b and 34b to be fitted to the stacking grooves 31d and 31d, engaging hooks 34c bent inward being provided at the bottom ends of the holding sections 34b. The coupling clip 34 is designed so that the holding sections 34b between the bridge 34a and the engaging hooks 34c are slightly longer than the overall thickness of the ferrules 31 stacked. To stack, for example, five ferrules 31, these ferrules 31 are first stacked so that their stacking grooves 31d are vertically aligned. Then, the coupling clip 34 is fitted onto the five stacked ferrules 31 from above while spreading the holding sections 34b and 34b. When the coupling clip 34 is pushed down along the stacking grooves 31d and 31d, the engaging hooks 34c and 34c slide down to the bottom ferrule 31, being guided by the stacking grooves 31d and 31d in the side surfaces of the individual ferrules 31. When the engaging hooks 34c and 34c reach the bottom surface of the lowest ferrule 31, the clamping force of the holding sections 34b and 34b causes the hooks to be secured onto the bottom surface of the lowest ferrule 31 and also causes the individual holding sections 34b to be fitted to the individual stacking grooves 31d of the five ferrules. Thus, a stacked-type optical connector with the five ferrules 31 stacked together is formed as shown in FIG. 14 and FIG. 15. The coupling clip 34 does not come off the stacked-type optical connector even if it is subjected to an upward pulling force since the clamping force of the holding sections 34b keeps the engaging hooks 34c secured to the bottom surface of the lowest ferrule 31. To butt-connect the stacked-type optical connector with another stacked-type optical connector, connecting pins not shown are inserted in the pin holes 31c of each ferrule 31 of one stacked-type optical connector, the butting end surfaces 31b of the individual ferrules 31 are butted, and the connecting pins are inserted in corresponding pin holes 31c of the individual butted ferrules 31, thus extending over both pin holes 31c and 31c. In this case, the length of the holding sections 34b between the bridge 34a and the engaging hooks 34c of the coupling clip 34 is made slightly greater than the overall thickness of the ferrules 31 stacked. Therefore, the individual ferrules 31 of the stacked-type optical connectors are stacked so that they substantially float along the length of the holding sections 34b with a specific degree of freedom to allow a gap between the ferrules 31. Thus, when the connecting pins inserted in the individual pin holes 31c of one ferrule 31 are inserted in the pin holes 31c of the mating ferrule 31, the ferrules 31 float along the length of the holding sections. As a result, the centers of the matching pin holes 31c with respect to the connecting pins are automatically aligned, ensuring smooth connection between the matching ferrules 31 and 31. In this way, the stacked-type optical connectors with a plurality of ferrules 31 stacked are butt-connected by inserting connecting pins in the matching pin holes 31c and 31c of the individual ferrules 31, and a leaf spring (not shown) is attached to their sides for keeping them butt-connected as in the first embodiment. The butt-connected stacked-type optical connectors can be easily separated into individual stacked-type optical connectors by removing said leaf spring and pulling them apart laterally. Further, each stacked-type optical connector can be easily separated into individual optical connectors 30 by spreading the holding sections 34b and 34b and drawing the coupling clip 34 upward. FIG. 16 through FIG. 19 illustrate the fourth embodiment of a method according to the present invention, wherein a plurality of optical connectors 40 are stacked into one piece with an elastic cap 50. In this case, the optical connector 40 has a ferrule 41, a tape fiber 42, and a boot 43 which protects a part extending from the rear of the ferrule 41 as shown in FIG. 17. The ferrule 41 has pinching portions 41b and 41b which protrude widthwise at the rear of a main body 41a, constituting the stacking portions. Optical fibers 42a of the tape fiber 42 are exposed on a front butting end surface 41c. Pin holes 41d and 41d which extend longitudinally are provided in either side of the main body 41a. An elastic cap 50 is a component which wraps around and holds all pinching portions 41b of a plurality of stacked ferrules 41, and its height and longitudinal width are slightly greater than the all pinching portions 41b together of the stacked ferrules 41. The elastic cap 50 has, as shown in FIG. 16, a base wall 50a, side walls 50b and 50b standing on the side edges of the base wall 50a, a top wall 50c, and a bottom wall 50d. The elastic cap 50 further has slits 50e which separate the side walls 50b and 50b from the top and bottom walls 50c and 50d, each of the walls 50b through 50d being provided with elasticity. There is no limitation on the material of the elastic cap 50 in particular as long as the stacked ferrules 41 are elastically held together. For instance, a metal such as aluminum or a synthetic resin such as polyethylene may be used. In this embodiment, the ferrules 41 of a plurality of optical connectors 40 are stacked using the elastic cap 50 as described below. First, the desired number, e.g., three, of optical connectors 40 are stacked by the pinching portions 41b which constitute the stacking portions to stack the ferrules 41. Then, as shown in FIG. 17, the elastic cap 50 is fitted onto the three pinching portions 41b on one side of the stacked ferrules 41. In the same manner, the elastic cap 50 is fitted onto the three pinching portions 41b on the other side to form a stacked-type optical connector shown in FIG. 19. Accordingly, in this stacked-type optical connector, a small gap is allowed between the ferrules 41 so that the ferrules can move slightly and also substantially float in the longitudinal direction, i.e., the butting direction, and in the vertical direction with a specific degree of freedom. In this case, the elastic cap 50 has a slightly greater height and longitudinal width than the size of all pinching portions 41b together of the stacked ferrules 41, and each of the walls 50b through 50d is given elasticity by the slits 50e. Therefore, the walls 50b through 50d elastically deform to slightly expand, allowing the elastic cap 50 to be easily fitted onto all the pinching portions 41b as shown in FIG. 18 and FIG. 19. Thus, by using the elastic cap 50, the three optical connectors 40 can be formed into a stacked-type optical connector wherein a plurality of ferrules 41 are compactly and easily stacked without taking any extra space. In addition, the elastic cap 50 can be provided at a low cost because of its simple structure. In the case of the stacked-type optical connector, the elastic cap 50 can be easily removed from a plurality of the pinching portions 41b simply by pulling the elastic cap 50 sideways, thus separating the stacked ferrules 41 into individual pieces. The stacked-type optical connector with a plurality of ferrules 41 stacked is butt-connected with another stacked-type optical connector by inserting connecting pins not shown into the corresponding pin holes 41d and 41d of the mating ferrules 41 and 41 in such a manner that the pins extend over the pin holes. When butt-connecting the stacked-type optical connectors, the pinching portions 41b of a plurality of the ferrules 41 are held together by the elastic cap 50, and the individual ferrules 41 are stacked so that they substantially float in the longitudinal vertical direction with a specific degree of freedom. Therefore, the individual ferrules 41 slightly float when butt-connecting the stacked-type optical connectors, and when the connecting pins inserted into the individual pin holes 41c of one ferrule 41 are inserted in the pin holes 41c of the mating ferrule 41, the centers of the matching pin holes 41c are automatically aligned, ensuring smooth connection between the matching ferrules 41 and 41. The fifth embodiment of the present invention is now described in detail, referring to FIG. 20 through FIG. 28. A stacked-type optical connector 60 consists of a plurality of optical connectors 61 shown in FIG. 20 which are stacked with stacking pins 62 so that they can float in the axial direction of the pins with a specific degree of freedom to allow a gap between the individual ferrules as shown in FIG. 21 and FIG. 22. As shown in FIG. 20, the optical connector 61 has a ferrule main body 61a with individual optical fibers 63a of a tape fiber 63 exposed at the front, and pinching portions 61b and 61b which project widthwise at the rear of the main body 61a. A part of the tape fiber 63, which extends from the main body 61a, is protected with a boot 64. The main body 61a has a tapered surface 61d around a front butting end surface 61c, and pin holes 61e and 61e formed lengthwise in either side of the width of the main body 61a. Connecting pins 61f and 61f for positioning when connecting with another stacked-type optical connector are inserted in the individual pin holes 61e in such a manner that they jut out from the butting end surface 61c and are free to move vertically. The connecting pins 61f are made slightly longer than the pin holes 61e so that their ends on one side protrude from the pin holes 61e by a specific length when they are inserted in the pin holes 61e. Further, the ends of the connecting pins 61f and of the pin holes 61e are tapered for easy insertion of the connecting pins 61f. The individual pinching portions 61b have stacking holes 61g and 61g which run through vertically, and these stacking holes 61g and 61g constitute the stacking portions. As shown in FIG. 21 and FIG. 22, the stacked-type optical connector 60 is assembled by stacking four optical connectors 61 with the stacking holes 61g in the pinching portions 61b aligned and inserting the stacking pins 62 in the vertically aligned stacking holes 61g, then installing snap rings 65 near the top ends. In this case, the length of the stacking pins 62 of the stacked-type optical connector 60 is set slightly greater than the height of the optical connectors 61 stacked so that, when the stacked-type optical connector is assembled, the individual optical connectors 61 can substantially float and move with a specific degree of freedom in the axial direction of the stacking pins 62 by a gap C formed between the top optical connector 61 and the snap rings 65 as shown in FIG. 21 and FIG. 22. The floating amount which allows the individual optical connectors 61 to move in the axial direction of the stacking pins 62 and which given by the gap C formed between the top optical connector 61 and the snap rings 65 is set smaller than the chamfering amount of the tapered surfaces 61d in the optical connector 61 and the chamfering amount of the ends of the connecting pins 61f or the pin holes 61e. The stacked-type optical connector 60 thus assembled is butt-connected to another stacked-type optical connector via an adapter 66 shown in FIG. 23. The adapter 66 has top and bottom pieces 66a and 66b, a side piece 66c, a flap 66d hinged with the bottom piece 66b, and a plurality of partitioning pieces 66e protruding from the side piece 66c and the flap 66d, the adapter being molded into one piece using a synthetic resin or the like. The adapter 66 is shaped like a rectangular tube by hooking a hook 66f provided on the top end of the flap 66d onto a engaging projection 66g formed on the end of the top piece 66a. When the stacked-type optical connector 60 is attached to the adapter, the individual optical connectors 61 move vertically with its tapered surfaces 61d being guided by the partitioning pieces 66e, and they are separately housed in the respective spaces formed by the side piece 66c, the flap 66d, and the individual partitioning pieces 66e. In this case, the gap C formed between the top optical connector 61 and the snap ring 65 specifies the floating amount for the optical connector 61 to move in the axial direction of the stacking pin 62. However, the actual floating amount allowed for each optical connector 61 is a value obtained by subtracting the total thickness of the three partitioning pieces 66e of the adapter 66 from the gap C and then equally dividing the resulting value. A stacked-type optical connector 60 using the adapter 66 thus configured is butt-connected to another stacked-type optical connector 60 according to the following procedure. First, the stacked-type optical connector 60 with connecting pins 61f inserted in the respective pin holes 61e is placed facing the other stacked-type optical connector 60 with no pins inserted, and the tapered surfaces 61d of the individual optical connectors 61 are applied to the partitioning pieces 66e of the adapter 66 as shown in FIG. 24. Then, when the individual stacked-type optical connectors 60 are pushed into the adapter 66, the tapered surfaces 61d are guided by the individual partitioning pieces 66e of the adapter 66, the individual optical connectors 61 float vertically, and as shown in FIG. 25, the front side of each of the optical connectors 61 is fitted into a specific space enclosed by the side piece 66c, the flap 66d and each partitioning piece 66e of the adapter 66. At the same time, the individual connecting pins 61f retreat while they are in contact with the pin holes 61e of the matching optical connector 61, thus moving in the respective pin holes 61e of the matching optical connector 61 to the right in the drawing. When both stacked-type optical connectors 60 are further pushed into the adapter 66, the individual connecting pins 61f of one optical connector 61 are inserted in the individual pin holes 61e of the other optical connector 61 while they are guided by the tapered ends, thereby butting the butting end surfaces 61c and 61c of the two optical connectors 61 and 61 as shown in FIG. 26. Thus, the individual optical connectors 61 of the stacked-type optical connectors 60 and 60 are butt-connected within the adapter 66. At this time, the individual optical connectors 61 float in the axial direction of the stacking pins 62 and 62 to permit good positioning for butt-connection. Since the floating amount is set smaller than the chamfering amount of the tapered surface 61d and of the end of each connecting pin 61f, each of the optical connectors is fitted into the specific space enclosed by the side piece 66c, the flap 66d and each 66e of the adapter 66. In addition, the individual connecting pins 61f of the mating optical connector 61 are made slightly longer than the pin holes 61e, and therefore, their ends are inserted in the pin holes 61e of the matching optical connector 61. In this way, the tape fibers 63 of the individual optical connectors 61 are properly butt-connected so that the individual optical fibers 63a exposed on the butting end surfaces 61c incur no connecting loss. The adapter 66 is removed from the properly butt-connected stacked-type optical connectors 60 and 60 by releasing the engagement between the hook 66f and the engaging projection 66g, pulling the flap 66d down, and drawing out the individual partitioning pieces 66e installed between the optical connectors 61 and 61. After that, a clip 67 is fitted from a side onto the two connected stacked-type optical connectors 60 and 60 as shown in FIG. 27 to hold them connected. In the case of the stacked-type optical connectors 60 thus butt-connected, if a failure or the like occurs, a single affected optical connector 61 can be isolated by removing the clip 67 and drawing out the stacking pins 62 and 62 to separate the optical connectors into single optical connectors 61. This makes it possible to perform maintenance work such as repair with all optical fibers 63a in other optical connectors 61 alive. Further, it is also possible to branch the optical line, taking out only the desired optical connector 61 while keeping the line alive. Each of the optical connectors constituting the foregoing stacked-type optical connector 60 may be provided with a guide 72 which extends lengthwise along either side of a ferrule 71 as in an optical connector 70 shown in FIG. 28, the guide 72 being provided, as shown in the drawing, with tapered surfaces 72a and 72a which serve as vertical guides and a tapered surface 72b which serves as a widthwise guide for butt-connecting the connectors via the adapter 66. In FIG. 28, the same components as those of the optical connector 61 of the foregoing stacked-type optical connector 60 are given the corresponding numbers, the detailed description being omitted. In the embodiments described above, when the ferrules are stacked up with the stacking pins, the snap rings are fitted near the ends of the stacking pins to prevent the pins from slipping off the ferrules. Needless to say, the means for preventing the stacking pins from slipping off the ferrules is not limited to the snap rings as long as it serves the purpose, and a cotter pin, for instance, may be used as the retainer. Further, in the embodiment wherein an adapter is used to stack the ferrules, the optical connectors are provided with tapered surfaces. Needless to say the adapter may be provided with tapered surfaces which serve as guides at the time of butt-connection. Furthermore, in all the embodiments discussed above, the description is based on optical connectors which have multi optical fibers, but needless to say the optical connectors may have a single optical fiber. Thus, in at least preferred embodiments there is provided a method for stacking ferrules of a stacked-type optical connector whereby easy, high density stacking of a plurality of ferrules can be achieved, and there is provided a stacked-type optical connector which permits smooth butt-connection between stacked-type optical connectors in a stack.

Claims: A method of forming a stacked-type optical connector, comprising providing a plurality of individual optical connectors (10;20;30;40;61;70) each having a ferrule (11;21;31;41;61a;71) in which one or more optical fibres of an optical fibre cable are embedded, the one or more optical fibres being exposed at an end portion (11b;21b;31b;41c;61c;71c) of the ferrule, each ferrule having a plurality of positioning pin receiving holes (11c;21c; 31c;41d;61e;71e) for butt connection, arranging said ferrules in a stack, aligning matching stacking portions (11d;21d;31d;41b;61g;71g) provided on each said ferrule (11;21;31;41;61a;71) and assembling the stacked-type optical connector by bringing one or more stacking members (12;22;34;50;62) into cooperation with said stacking portions of said ferrules, such that the stacked ferrules (11;21;31;41;61a;71) are guided by said stacking member or members, so that they can float therealong with a degree of freedom to move towards and away from each other in the direction in which they are stacked, thereby allowing gaps to be formed between adjacent ferrules. The method of forming a stacked-type optical connector according to claim 1, wherein each ferrule (11;21;31;41;61a;71) has two positioning pin receiving holes (11c;21c;31c;41d;61e;71e) formed in said end portion (11b;21b;31b;41c;61c;71c), spaced laterally with the one or more optical fibres therebetween, and said one or more stacking members (12;22;34;50;62) are engaged with stacking portions (11d;21d;31d;41b;61g;71g) on both laterally spaced sides of each ferrule (11;21;31;41;61a; 71), such that each ferrule (11;21;31;41.;61a;71) can move towards and away from adjacent ferrules (11;21;31; 41;61a;71) at each laterally spaced side thereof. The method of forming a stacked-type optical connector according to claim 1 or 2, wherein said stacking portions are stacking holes (11d;21d;61g;71g) formed in said ferrules (11;21;61;70). The method of forming a stacked-type optical connector according to claim 3, wherein said stacking members are a plurality of stacking pins (12;62) which are inserted in said respective corresponding aligned stacking holes (11d;61g;71g) and which are provided with retaining means (12c;15;65). The method of forming a stacked-type optical connector according to claim 4, wherein said retaining means consists of a concave groove (12c) formed in said stacking pin (12) and a snap ring (15) fitted onto the concave groove (12c). The method of forming a stacked-type optical connector according to claim 3, wherein said stacking member is a single U-shaped stacking pin (22) which is inserted in two sets of said aligned and stacked stacking holes (21d) and which is provided with a retaining means (22c,25). The method of forming a stacked-type optical connector according to claim 6, wherein said retaining means consists of concave grooves (22c) formed in said stacking pin (22) and snap rings (25) fitted to the concave grooves (22c). The method of forming a stacked-type optical connector according to claim 1 or 2, wherein said stacking portions are stacking grooves (31d) provided in said ferrule (31). The method of forming a stacked-type optical connector according to claim 8, wherein said stacking member is a coupling clip (34) which has holding portions (34b) to be fitted to said aligned and stacked stacking grooves (31d), and engaging hooks (34c). The method of forming a stacked-type optical connector according to claim 1 or 2, wherein said stacking portions consist of pinching portions (41b) provided on said ferrule (41). The method of forming a stacked-type optical connector according to claim 10, wherein said stacking member is an elastic cap (50) designed to wrap and hold said aligned and stacked pinching portions (41b). The method of stacking ferrules of a stacked-type optical connector according to claim 11, wherein said cap (50) is provided with slits (50e) for producing elasticity. A stacked-type optical connector comprising a plurality of individual optical connectors (10;20;30; 40;61;70) each having a ferrule (11;21;31;41;61a;71) in which one or more optical fibres of an optical fibre cable are embedded, the one or more optical fibres being exposed at an end portion (11b;21b;31b;41c;61c;71c) of the ferrule each ferrule having a plurality of positioning pin receiving holes (11c;21c;31c;41d;61e;71e) for butt connection, said stacked-type optical connector further comprising means for assembling said ferrules into a stack with their end portions; aligned, characterised in that said means for assembling the ferrules (11;21;31;41;61a;71) into a stack comprises one or more stacking members (12; 22;34;50;62) adapted to co-operate with stacking portions (11d;21d;31d;41b;61g;71g) formed at matching positions on each said ferrule in such a way that the stacked ferrules are guided by said stacking member or members so that they can float therealong with a degree of freedom to move towards and away from each other in the direction in which they are stacked, thereby allowing gaps to be formed between adjacent ferrules. The stacked-type optical connector as claimed in claim 13, wherein each ferrule (11;21;31;41;61a;71) has two positioning pin receiving holes (11c;21c;31c;41d; 61e;71e) formed in said end portion (11b;21b;31b;41c; 61c;71c), spaced laterally with the one or more optical fibres therebetween, and said one or more stacking members (12; 22;34;50;62) engage with stacking portions (11d;21d;31d; 41b;61g;71g) formed on both laterally spaced sides of each ferrule (11; 21;31;41;61a;71), such that each ferrule (11;21;31;41;61a;71) can move towards and away from adjacent ferrules (11;21;31;41;61a;71) at each laterally spaced side thereof. The stacked-type optical connector according to claim 13 or 14, wherein said stacking portions are stacking holes (11d;21d;61g;71g) provided in said ferrule (11;21;61a;71). The stacked-type optical connector according to claim 15, wherein said stacking members are a plurality of stacking pins (12;62) which are inserted in said corresponding stacking holes (11d;61g;71g) and which are provided with a retaining means (12c,15;65). The stacked-type optical connector according to claim 16, wherein said retaining means consists of a concave groove (12c) formed in said stacking pin (12) and a snap ring (15) fitted to the concave groove (12c). The stacked-type optical connector according to claim 15, wherein said stacking member is a single U-shaped stacking pin (22) which is inserted in two sets of said aligned and stacked corresponding stacking holes (21d) and which is provided with a retaining means (22c, 25). The stacked-type optical connector according to claim 18, wherein said retaining means consists of concave grooves (22c) formed in said stacking pin (22), and snap rings (25) fitted to the concave grooves (22c). The stacked-type optical connector according to claim 13 or 14, wherein said stacking portions consist of stacking grooves (31d) formed in said ferrule (31). The stacked-type optical connector according to claim 20, wherein said stacking member is a coupling clip (34) which has holding portions (34b) fitted to said corresponding aligned and stacked stacking grooves (31d) and engaging hooks (34c). The stacked-type optical connector according to claim 13 or 14, wherein said stacking portions consist of pinching portions (41b) provided on said ferrule (41). The stacked-type optical connector according to claim 22, wherein said stacking member is an elastic cap (50) designed to wrap and hold said corresponding aligned and stacked pinching portions (41b). The stacked-type optical connector according to claim 23, wherein said cap (50) is provided with slits (50e) which produce elasticity. The stacked-type optical connector according to any of claims 13 to 24, wherein said stacked-type optical connector is butt-connectable to another stacked-type optical connector via an adapter (66). The stacked-type optical connector according to claim 25, wherein the individual ferrules (71) of said stacked-type optical connector are provided with guides (72) for butt-connecting to another stacked-type optical connector via said adapter (66).

Inventors: OHTA SHINICHIRO, OHTA TOSHIHIKO, SAITO MASAMI, TANABE ETSUO, YAMADA HIROYUKI, OHTA, SHINICHIRO, OHTA, TOSHIHIKO, SAITO, MASAMI, TANABE, ETSUO, YAMADA, HIROYUKI, Ohta, Shinichiro, c/o The Furukawa, Ohta, Toshihiko, c/o The Furukawa, Saito, Masami, c/o The Furukawa, Tanabe, Etsuo, c/o The Furukawa, Yamada, Hiroyuki, c/o The Furukawa
Applicants: FURUKAWA ELECTRIC CO LTD, THE FURUKAWA ELECTRIC CO., LTD.
Application year: 1991
Main classification: G02B6
IPC codes: H01R13, G02B6