PIN PLUG FOR AN OPTICAL FIBER

Abstract: A plug body (11) has, on its front, a cylindrical portion (14) integrally molded therewith and a ferrule (15) is dis­ posed in the cylindrical portion along the axis. The front end portion of the ferrule projects out of the cylindrical portion and the rear end portion is inserted in the plug body. An optical fiber exposed at the front end of an opti­ cal fiber cable can be fitted in the front end portion of the ferrule with the rear end portion of the optical fiber cable led out from the back of the plug body (11).

Description: The present invention relates to a pin plug for an optical fiber according to the precharacterizing clause of claim 1 (US-A-4,186,996). Particularly, the present invention relates to a pin plug for an optical fiber which can be coupled with the mating jack by insertion therein to for optical coupling therewith. Optical connections are known which are composed of a plug and a jack as is the case with an electric connector. However, since the plug and the jack of the optical connector considerably differ in shape from those of the electric connector, the optical connector cannot be employed for those of the electric connector nor can it be used in combination with the electric connector. From US-A 4,186,996 a pin plug according to the precharacterizing clause of claim 1 is known. Said prior art pin plug comprises a ferrule to be radially compressed in order to bias corresponding optical cores into coincident alignment. Said ferrule is provided in the form of pipe or the like. Those pipes as well as the above described processing in order to bias the optical fibers renders the pin plug expensive. The object underlying the invention is, therefore, to provide a pin plug for an optical fiber which can be mechanically coupled with the conventional electric pin jack, for optical coupling therewith and which is cheap in manufacturing and assembling. The above object is, according to the invention, solved by a pin plug according to claim 1. Preferred embodiments are claimed in the subclaims. According to the present invention, a plug body has a cylindrical portion extending from the front thereof and a ferrule is disposed to extend through the plug body and the cylindrical portion along its axis. The front end portion of the ferrule projects out of the cylindrical portion and the rear end portion is inserted in the plug body. The optical fiber exposed at the front end of an optical fiber cable is fitted in the front end of the ferrule and the rear end portion of the optical fiber cable is led out from the rear of the plug body. In this instance, that portion of the ferrule projecting out of the plug body has the same size and shape as those of a contact of the so-called electric pin plug, and the cylindrical portion also has the same size and shape as those of a sleeve of the conventional electric pin plug. Therefore, the pin plug of the present invention can be mechanically coupled with the conventional electric pin jack. Accordingly, an optical connector can be formed with the same mechanical configuration and size as those in the prior art, by disposing a photodetector or light emitting element adjacent the tip of the pin plug inserted into the conventional electric pin jack. Since the ferrule is formed by simply bending sheet metal into a cylindrical form, the pin plug according to the invention is cheaper than known pin plugs. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view illustrating an example of the pin plug according to the present invention; and Fig. 2 is a perspective view showing a step in the manufacture of a ferrule used in the example of Fig. 1 and an example of the connection of an optical fiber cable to the ferrule DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 schematically illustrates an example of the pin plug of the present invention. Reference numeral 11 indicates a plug body, which is, for example, a columnar molding of an insulating material. The plug body 11 has a through hole 12 extending along its axis and the through hole 12 has a recess 13. The plug body 11 has a hollow cylindrical portion 14 integrally molded therewith on the front. The cylindrical portion 14 and the through hole 12 are axially aligned. A ferrule 15 is disposed along the axis of the cylindrical portion 14, with the rear end portion of the former pressed into and held in the plug body 11 and the front end portion projecting out of the cylindrical portion 14. The ferrule 15 has housed therein an optical fiber cable 16. An optical fiber 17 of the optical fiber cable 16 is exposed at the front end thereof and fitted and positioned in a thin through hole 20 formed in the tip of the ferrule 15. Accordingly, the inner diameter of the thin through hole 20 in the tip of the ferrule 15 is selected small enough to snugly receive the optical fiber 17 of the optical fiber cable 16. That portion 15a of the ferrule 15 projecting out of the plug body 11 has housed therein the optical fiber cable 15 with its outer sheath removed; accordingly, the portion 15a has an inner diameter larger than that of the thin through hole 20 and will hereinafter be referred to as a medium-diametered portion. That portion 15b of the ferrule 15 inserted in the plug body 11 has housed therein the optical fiber cable 16 with its outer sheath unremoved; accordingly, the portion 15b is larger in inner and outer diameter than the medium-diametered portion 15a and will hereinafter be referred to as a large-diametered portion. The rear end portion of the large-diametered portion 15b is formed as a cable clamper 18 for clamping the optical fiber cable 16 to fix it to the ferrule 15. The optical fiber cable 16 is led out of the rear end face of the plug body 11 for external connection. The ferrule 15 has a pawl 19 standing out from the underside of the large-diametered portion 15b, and the pawl 19 is positioned in the recess 13 for preventing the ferrule 15 from slipping out of the through hole 12 of the plug body 11 after the former was pressed into the latter from behind. The ferrule 15 is obtained by pressing sheet metal into a tubular form as shown in Fig. 2. In this case, a series of such ferrules 15 are produced and coupled together at the rear end through a carrier 21. The optical fiber cable 16 is inserted into each ferrule 15 and fixed thereto by the cable clamper 18, with the optical fiber 17 projecting out of the tip of the ferrule 15, and the projecting end of the optical fiber 17 is cut off at the tip of the ferrule 15. The cylindrical portion 14 of the plug body 11 has the same size and shape as those of a sleeve portion of an ordinary electric pin plug, and the medium-diametered projecting portion 15a of the ferrule 15 has the same size and shape as those of a pin contact of the ordinary pin plug. Accordingly, the ferrule 15 has a ring-shaped groove 22 made in the projecting portion 15a at a place close to the open end of the cylindrical portion 14 so that the projecting portion 15a is resiliently gripped by a contact piece of the mating pin jack. As described above, the pin plug according to the present invention can be used with an optical fiber, as a pin plug of an optical connector, in combination with an electric pin jack-pin plug assembly without the necessity of modifying its mechanical arrangement and size.

Claims: A pin plug for an optical fiber, comprising: a plug body (11) made of an insulating material; a cylindrical portion (14) formed integrally with the plug body on the front thereof; and a ferrule (15) disposed in the cylindrical portion and in the plug body (14) along the axis of the cylindrical portion, the front end portion of the ferrule extending into the cylindrical portion and the rear end portion being inserted in the plug body; the ferrule being adapted to have an optical fiber cable (16) inserted in it, such that an optical fiber (17) projecting of the optical fiber cable at the front end thereof is fitted and positioned in the front end portion of the ferrule with the rear end portion of the optical fiber cable being led out of the plug body at the rear end face thereof, characterized in that the ferrule (15) is formed, in its entirety, by bending sheet metal into a cylindrical form and projects out of the cylindrical portion (14). The pin plug of claim 1, characterized in that the front end portion of the ferrule (15) projecting out of the cylindrical portion (14) has an annular groove (22) in its outer peripheral surface. The pin plug of claim 1 or 2, characterized in that the plug body (11) has a through hole (12) bored along the axis thereof, the ferrule (15) being pressed into the through hole. The pin plug of claim 3, characterized in that the rear end portion of the ferrule (15) has a large-diametered portion (15b), the large-diametered portion being pressed in the through hole (12) of the plug body (11) from behind. The pin plug of claim 4, characterized in that the through hole (12) has a recess (13) and a pawl (19) standing out from the ferrule (15) in the large-diametered portion (15b) is locked in the recess. The pin plug of claim 4, characterized in that the large-diametered portion (15b) of the ferrule (15) is adapted to have inserted therein the optical fiber cable (16), said portion of the ferrule (15) projecting out of the plug body is a medium-diametered portion (15a) adapted to have inserted therein the optical fiber cable (16) with its outer sheath removed, and a small-diametered through hole (20) in the projecting end portion of the ferrule is adapted to have fitted therein the exposed optical fiber (17) of the optical fiber cable, an end face of the exposed optical fiber to be flush with an end face of the projecting end portion of the ferrule. The pin plug of claim 6, characterized in that the rear end portion of the large-diametered portion (15b) of the ferrule (15) has a cable clamping portion (18) formed integrally therewith, for clamping the optical fiber cable (16).

Inventors: KOMATSU, YASUHIRO
Applicants: HOSIDEN CORPORATION
Application year: 1988
Main classification: G02B6
IPC codes: G02B6, H01R24