OPTICAL CONNECTOR

Abstract: An improved optical fiber connector (1) adapted to prevent excessive bending of the optical fiber (7) connected is proposed. A bushing (8) having a curved convex surface (29) at its rear end is provided adjacent to the rear end of the plug attached to the end of the optical fiber (7).

Description: OPTICAL CONNECTOR BACKGROUND AND SUMMARY OF THE IYVENDION The present invention relates to an optical connector for connecting optical fibers with photoelectric elements or optical fibers. In the optical communication, signals are transmitted from a light emitting element through optical fibers to a light receiving element. An optical connector is used for connection of optical fibers with photoelectric elements or optical fibers. In many cases, an elongated metallic plug is mounted on the tip of each optical fiber and the plug is held in a male optical connector. On the other hand, the photoelectric elements are held in a female optical connector having a hollow portion. When the male and female connectors are coupled to each other, there will result a connection between the optical fibers and the photoelectric elements. Because of the necessity of connecting two lines, transmitting and receiving ones, the female optical connector is often adapted to contain light emitting and receiving elements disposed side by side. In that case, the male optical connector, too, contains two optical fibers disposed side by side, each fiber having a plug attached to its end. Of course, sometimes only a single line has to be connected. In the conventional connectors, optical fibers are enclosed in a flexible material such as synthetic resin and rubber, the optical fibers extending from the rear end of the metal plugs. But, they are sometimes forced to bend excessively under tension applied thereto. The flexible material is easily deformed so that it is not capable to prevent the optical fibers from bending excessively. Optical fibers are made from quarts, glass, plastics, etc. They might' bye broken if the optical fiber were forcibly bent with too small a radius of curvature. An object of the present invention is to provide an optical connector which can prevent excessive bending of the optical fiber cables. In accordance with the present invention, a bushing havi a curved convex surface at its rear end is provided adjacent to the rear end of the plug to prevent excessive bending of the optical fibers. Other- objects and advantages of the present invention wiLl become apparent from the following description taken with reference to the accomianying drawings, in which: BRIEF DESCRIPTION OF ss DRAWINGS Fig. I is-a plan view of an optical connector embodying the present invention; Fig. 2 is a front view of the same; Fig. 3 is a cross-sectional view taken along line III - III of Fig. 1; Fig. 4 is a rear view of the bushing; Fig. 5 is a plan view of the same broken in part; Fig. 6 is a front view of the same; Fig. 7 is a right side view of the same broken in part; Fig. 8 is a cross-sectional view taken along line VIII - VIII in Fig. 7; Fig. 9 is a perspective view of the bushing as seen from the front side; Fig. 10 is a perspective view of the same as seen from the rear side; Fig. 11 is an enlarged sectional view showing the optical connectors bent; Fig. 12 is a schematic view showing different radii of curvature on a curve formed by the curved convex surface. DETAILED DESCRIPTION OF THE INVENTION An optical connector l has a connector body 2, a waterproof boot 3, a bellows 4 and a tape 5. The optical connector 1 accommodates a pair of optical fiber cables 7 having a plug 5 attached to the tip thereof. The cables 7 extend through the waterproof boot 3 and the bellow 4 with the plug 6 extending through a bushing 8 and a top cover 9. The connector body 2 made of plastics has an opening 10 in its front part, where the tips of the plugs 6 protrude. A female optical connector (not shown) with photoelectric- elements is to be received in the opening 10. At the midpoint of the connector body 2 there is formed a partition plate 11 perpendicular to the axis and having a hole 12 to receive -the plug 6. At on side of the connector body 2 is provided a retaining plate 14 formed with a jaw 13 to prevent the possible removal of the male connector from its connected position The connector body 2 is also provided-with a projection 15 near its rear end for engagement between the top cover 9 and connector body 2. The top cover 9- functions to couple the waterproof boot 3 with the connector body 2 as well as to keep the plug 6 in alignment. The top cover 9 comprises a tubular portion 16 disposed at its rear, a central ring portion 17, vertical grooves 18 and a front ring portion 19 at its front. The top cover 9 is made in the form of a stepped tube whose diameter is narrower at its rear and wider at its front. There are provided at least two vertical grooves 18, the part except the grooves continuing to the front ring portion 79. A projection 20 serves to couple the top cover 9 with the waterproof boot 3. The waterproof boot 3 is formed with a c-onical portion 21 narrowing toward its rear end so as to protect the optical fiber cables 7. The waterproof boot 3 is formed with an enlarged portion 22 to receive the rear end of the bushing 8. The waterproof boot 3 has a projection 23 which serves to receive the projection 20 of the top cover 9. The foremost end of the boot 3 is a tubular portion 24 for holding the connector body 2 in position. Each plug 6 has a flange 25 which abuts against the inner face of the partition plate 11 in the connector body. A spring 26 is mounted between the flange 25 and the tubular portion 16 of the top cover 9 to urge the flange 25 against the partition plate 11. The plug 6 is provided with a light passing hole 27 on its front end. The present invention is characterized in that the bushing 8 is provided in order to avoid excessive bending of the optical fiber cables. A bushing 8 is of a plate-like shape at its rear end with each corner rounded. (Fig. 9) Important is that a curved convex surface 29 is formed on its rear end face. The bushing 8 has a central hole 30 extending axially, the optical cables passing therethrough. The convex surfaces 29 - above and below the hole 30 are in the form of a half circle (Fig. 7) with a radius Rb of 3 mm, while the curved convex surfaces 29 to the right and left of the hole 30 are in the form of a quadrant (Fig. 5) with the same radius. The bushing 8 has a tubular portion 31 of an oval cross-section to encase the tubular portion 16 of the top cover 9. The bushing 8 is formed with an outer shoulder 32, where the bushing 8 abuts against the projecting portion 22 of the boot 3. An inner shoulder 55 is fit on the end face of the tubular- portion 16 of the top cover. Next, the effect of the present invention will be described below. In the optical connector according to the present invention, a bushing having the curved convex surface 29 on its rear end is provided. Therefore, the optical fiber cables passing through the bushing will not be bent to an excessive degree even under tension applied thereto from side. Fig. 11 shows an optical fiber cable subjected to bending. The value R in' which is the minimum radius of curvature at the bending portion of the optical fiber cable, may be expressed as Rmin = Rb + rc --- (1) wherein Rb is the radius of curvature of the curved convex surface of the bushing and rc is the radius of the cable. Therefore, the optical fiber cable will not bend with a smaller radius of curvature than the minimum onem This ensures that the breakage of the fiber cables due to repeated excessive bendings can be prevented. In this embodiment, the radius of curvature Rb along the curved convex surface is constant. The central angle 6 of the arc formed with said radius is 1800 (semicircle) in the vertical direction while it is 900 (quadrant) in the horizontal direction. The difference in the central angle is due to the fact that the two optical fibers are more liable to be bent in the vertical direction since they extend side by side. However, the central angle of the arc defined by the convex surface may be selected suitably over the range of about 700 and 1800. Also, the radius of curvature Rb may not necessarily be constant. Fig. 12 is a schematic view showing a crosssectional configuration of the curved convex surface 29. By the following formula, the radius of curvature Re may be defined at each point P on a curve l having coordinates X and r, EMI7.1 This makes it possible to determine the minimum radius of curvature Rmin on basis of the materials, diameter and other measurements of the optical fibers used. The radius of curvature Rl at a given point is determined to meet the following requirement, Rl # Rmin ------------ (3) Although the present invention has been described with reference to a preferred embodiment, it is to be understood that many changes and variations can be made without departing from the scope of the present invention

Claims: What are-claimed are. 1. In an optical fiber connector for connecting at least one optical fiber with a photoelectric element or an optical fiber, said optical fiber having a plug attached to the end -thereof, the improvement comprising means for preventing excessive bending of said optical fiber. 2. The optical fiber connector as claimed in claim 1, wherein said means comprise a bushing disposed adjacent to the rear end of said plug, said bushing having a curved convex surface at the rear end thereof.

Inventors: HAYASHI, KYOZO, MORIYAMA, MASAKAZU, SHINOHARA, TOSHIO, SUGIMOTO, TETSUO
Applicants: SUMITOMO ELECTRIC INDUSTRIES LIMITED, TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1982
Main classification: G02B6
IPC codes: G02B6