JPH10268143A - Rubber bushing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rubber bushing capable of coping with optical fibers having different diameters. SOLUTION: Rubber bushing is formed out of a flange part 1 and a truncated cone part 3 formed to be continuous thereto. Also, the bushing has a large- diameter hole 2a and a small-diameter hole 2b formed at the center so as to be continuous to each other. At the time of sealing a pipe end by use of the rubber bushing, the slit 4 thereof is opened and, then, an optical fiber exposed from the end of a laid pipe 6 is introduced to an inner optical fiber holding hole 2, and the rubber bushing is inserted in a pipe 6. For application to an optical fiber corresponding to the diameter of the small hole 2b, the rubber bushing is used without any modification. For application to an optical fiber corresponding to the diameter of the large hole 2a, the rubber bushing is cut with a cutting groove for the disposal of the forward end thereof and, then, the optical fiber is retained with the hole 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal processing method for an optical fiber sent through a small-diameter pipe, and more particularly to a rubber bushing structure for holding an optical fiber at an end of the pipe and sealing a gap.

[0002]

2. Description of the Related Art In recent years, as a wiring method having a high degree of freedom in optical wiring technology, a small-diameter empty pipe is laid in advance, and an air current is used inside the pipe to provide a flexible pipe having no tensile strength. A method of transmitting and arranging a simple optical fiber is used. The optical fiber used at this time has an elastic modulus of 100 kg / mm ² with the optical fiber core.
And a very thin structure with a small outer diameter of 0.5 to 3.0 mm.

FIG. 4 is a sectional view of an example of such an optical fiber. In the figure, 11 is an optical fiber core, and 12 is a jacket. FIG. 4A shows a one-core optical fiber. Diameter 0.
The outer sheath 12 is formed by covering a 25 mm optical fiber core 11 with a foamed polyethylene having a foaming ratio of 55%. The outer diameter of the jacket is 1.0 mm. FIG. 4B shows a two-core optical fiber. Two optical fiber core wires 11 having a diameter of 0.25 mm are laid in parallel or twisted, and the periphery thereof is covered with a foamed polyethylene having a foaming rate of 55% as a jacket 12. The outer diameter of the jacket is 1.2 mm. FIG. 4C shows a seven-core optical fiber. Seven optical fiber core wires 11 having a diameter of 0.25 mm are assembled, and the outer periphery thereof is covered with a foamed polyethylene having a foaming rate of 55% as a jacket 12. The outer diameter of the jacket is 1.5 mm. The seven optical fiber core wires 11 are obtained by twisting six optical fibers around one center. FIG. 4D shows a four-core optical fiber.
It is made by covering a nylon-coated optical fiber core wire 11 having a diameter of 0.9 mm with a jacket 12 made of foamed polyethylene. The outer diameter of the jacket is 3.0 mm. FIG.
It is a Teflon coated optical fiber. The outer periphery of an optical fiber core wire 11 having a diameter of 0.25 mm is covered with Teflon as a jacket 12. The outer diameter of the jacket is 0.7 mm.
The above-described numerical values and materials are merely examples, and there are designs with appropriate numerical values, and appropriate materials are used.

FIG. 5 shows an example of a pipe. A plurality of pipes assembled into a cable is called a pipe cable. In the figure, 13 is a pipe, 14 is a central tensile member, and 15 is a sheath. FIG. 5A shows a pipe cable in which six cables are assembled. The pipe 13 has an inner diameter of 4.5 m
m, made of polyethylene having an outer diameter of 6.0 mm. The central tensile strength member 14 is formed by twisting steel wires and coating the resin with a resin to make the outer diameter approximately equal to the pipe diameter. Six pipes are assembled around the center tensile member 14 and a sheath 15 is applied to make the outer diameter 23 mm. FIG.
(B) is a cable in which two pipes are formed. A sheath 15 is provided around two pipes having an inner diameter of 6.0 mm and an outer diameter of 8.0 mm. The minor axis is 11 mm and the major axis is 19 mm. Also in this example, the numerical values and materials described above are examples, and there are designs with appropriate numerical values, and appropriate materials are used. For example, a pipe having an inner diameter of about 1.5 to 8.0 mm is generally used.

[0005] In a terminal that transmits an optical fiber as described above to the pipe, the optical fiber is fixed to the pipe, and dust or water accumulates in a gap between the pipe and the optical fiber, thereby impairing the reliability of the optical transmission line. Need to be sealed.

Conventionally, only commercially available optical fiber gripping and sealing parts at the end of a pipe are of a large size consisting of a number of parts using a screw mechanism, and have problems in terms of space efficiency and cost.

For this reason, conventionally, there has been a device using a rubber bushing 16 having a structure shown in FIG. The rubber bushing 16 has a hole 17 having an inner diameter corresponding to the outer diameter of an optical fiber to be used penetrating therein, and a slit 18 reaching the hole 17 from the outer periphery. This rubber bushing 1
6 was specially manufactured to seal and hold an optical fiber. Japanese Patent Application Laid-Open No. 8-43697 discloses a water stop bushing having a similar structure.

[0008] However, the rubber bushing with holes has the following problems.
Since the optical fibers are gripped by the holes 17 corresponding to the optical fibers of various types, the optical fibers having different outer diameters cannot be gripped and sealed at the end of the pipe. For this reason, it is necessary to prepare a rubber bushing in which a hole corresponding to each type of the outer diameter of the optical fiber is formed, which causes a problem that the manufacturing cost is increased and the management work is complicated.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a rubber bushing capable of coping with optical fibers having different outer diameters as exemplified in FIG. Things.

[0010]

According to a first aspect of the present invention, there is provided a rubber bushing which is inserted into an end of a pipe through which an optical fiber is passed and laid, and has a substantially frusto-conical outer portion. Holes having different diameters are continuously provided in the inside thereof in the longitudinal direction, and the holes are provided such that the small-diameter hole is on the tip side.

According to a second aspect of the present invention, there is provided a rubber bushing which is inserted into an end of a pipe through which an optical fiber is laid, and has a substantially truncated conical outer portion from the center toward both sides. In addition, holes of different diameters are provided inside the portions on both sides, and the holes on both sides are connected.

According to a third aspect of the present invention, in the rubber bushing according to the second aspect, the holes provided in at least one of the portions having the truncated cone shape provided on both sides have different diameters. Are continuous in the longitudinal direction, and the holes are provided so that a small-diameter hole is provided on the front end side of the outer shape.

According to a fourth aspect of the present invention, in the rubber bushing according to the first or third aspect, the hole is a hole whose diameter changes stepwise.

According to a fifth aspect of the present invention, in the rubber bushing of the first or third aspect, the hole is a hole having a continuously changing diameter.

[0015]

FIG. 1 is a view for explaining a first embodiment of a rubber bushing according to the present invention.
1A is a perspective view, and FIG. 1B is a cross-sectional view. In the figure, 1
Is a flange, 2, 2a and 2b are holes, 3 is a truncated cone,
4 is a slit, 5 is a cutting groove, and 6 is a pipe.

In this embodiment, the rubber bushing comprises a flange portion 1 and a frusto-conical portion 3 following the flange portion. The hole 2 along the central axis has a large diameter hole 2a and a small diameter hole 2b.
Are provided continuously. The boundary between the hole 2a and the hole 2b may change in diameter in a stepwise manner, or may be tapered so that portions having different inner diameters are continuous. The truncated conical portion 3 has a cutting groove 5 provided at an intermediate portion, and the cutting groove 5 is located at a position corresponding to a boundary between the hole 2a and the hole 2b.

In order to seal the end of the pipe using the rubber bushing, the slit 4 of the rubber bushing is opened, and the optical fiber projecting from the installed pipe end is led to the internal optical fiber holding hole 2. Inserting the rubber bushing into the pipe 6 seals the gap between the end of the pipe and the optical fiber. Since the diameters of the holes 2a and 2b correspond to the outer diameters of the optical fibers, this embodiment can be used for optical fibers having two types of outer diameters. That is, in the case of applying to an optical fiber corresponding to the diameter of the hole 2b, if the rubber bushing is used as it is, the optical fiber can be gripped by the hole 2b. Hole 2a
When applying to an optical fiber corresponding to the diameter of the hole 2a, the rubber bushing is cut at the cutting groove 5 and the tip side is discarded.
Hold the optical fiber with. The cutting groove 5 is easy to cut,
It is provided to make the cutting position easy to understand,
Instead of using grooves, the display may be replaced with a display that simply indicates the cutting position. The flange portion 1 does not necessarily have to be provided.

Since this rubber bushing has an outer diameter of a truncated cone, it can be brought into close contact with the pipe when it is pushed into the pipe, and has a truncated conical outer shape, so that a predetermined range of the pipe inner diameter can be accommodated. Can be given.

Although specific examples will be described, the present invention is not limited to the numerical values and materials described below. In a specific example, the bushing corresponds to two types of optical fibers having an outer diameter of 1 mm and 1.5 mm. Therefore, the diameter of the hole 2a was 1.5 mm, and the diameter of the hole 2b was 1 mm. When used for an optical fiber having an outer diameter of 1 mm, the entire length is pushed into the pipe as shown in FIG. 1 (A), and the optical fiber is gripped by the hole 2b of the small diameter portion on the tip side of the bushing, and the space with the pipe is reduced. Seal. When used for an optical fiber with an outer diameter of 1.5 mm, the cutting groove 5 is cut with a nipper or a cutter, the tip end including the hole 2b is removed, and the optical fiber is gripped using only the large diameter portion of the hole 2a to form a pipe. To seal the space.

The dimensions of each part are as follows.
mm, and the length in the axial direction is 3 mm. The truncated cone 3
The outer diameter on the flange 1 side is 5 mm and the outer diameter on the tip side is 3.5
mm, the length in the axial direction is 25 mm, and 1 mm in the middle
A cutting groove 5 having a width of 5 mm was formed. The applicable pipe inner diameter is 4.
Although it is 5 mm, there is some margin because the outer periphery is a truncated cone.

The rubber bushing was made of natural rubber having a hardness of 60, and provided a grip force of 350 g and 540 g for optical fibers having an outer diameter of 1 mm and 1.5 mm, respectively. As a material for the rubber bushing, a synthetic resin having an appropriate elasticity can be used.

FIGS. 2A and 2B are views for explaining a second embodiment of the rubber bushing of the present invention. FIG. 2A is a perspective view and FIG. 2B is a sectional view. In the figure, the same parts as those in FIG. 3a and 3b are truncated cones, and 7 is a display.

In this embodiment, two frusto-conical portions are formed, and the large diameter side is brought into contact with the flange portion 1 so as to be integrated. Of the holes 2, the large-diameter hole 2 a is provided on the side of the truncated cone 3 a, and the small-diameter hole 2 b is located on the side of the truncated cone 3.
The hole 2a and the hole 2b communicate with each other.
Indications 7 are obtained by printing the outer diameter of the applied optical fiber in numerical values. In this example, the fact that 1.0 mm and 1.5 mm can be applied is indicated on the truncated cone. It may be displayed by symbols, patterns, colors, or the like.

In use, when applied to an optical fiber corresponding to the small diameter hole 2b, the side of the truncated cone 3b is inserted into a pipe, the outer periphery is supported by the pipe, and the optical fiber is gripped by the hole 2b. Seal the space with the pipe. When applied to an optical fiber corresponding to the large-diameter hole 2a, the frustoconical portion 3a is inserted into a pipe and used similarly. In this case, the small-diameter hole 2b side may be cut and removed, or may be left. This is because the truncated conical portion 3b on the side of the small-diameter hole 2b is not pressed from the outer periphery by the pipe, so that the slit 4 is in a half-open state, and no large lateral pressure is applied to the optical fiber.

The dimensions of the specific example are as follows. The flange portion 1 has an outer diameter of 8 mm and an axial length of 3 mm. Frustoconical part 3
In a and 3b, the outer diameter on the flange portion 1 side was 5 mm, the outer diameter on the distal end side was 4.0 mm, and the length in the axial direction was 12 mm. The diameter of the hole 2a was 1.5 mm, the diameter of the hole 2b was 1.0 mm, and the inner diameter of the pipe to be applied was 4.5 mm, as in the specific example in the first embodiment.

When natural rubber having a hardness of 60 was used as the material, when used for optical fibers having an outer diameter of 1 mm and 1.5 mm, the gripping force was 400 g and 550 g.

FIG. 3 is a sectional view of a rubber bushing according to a third embodiment of the present invention. In the figure, the same parts as those in FIG. 2c is a hole.
In this embodiment, the first embodiment and the second embodiment are combined. Hole 2a has a large diameter and hole 2b
Has a small diameter and the hole 2c has an intermediate diameter, but the hole 2b may have an intermediate diameter and the hole 2c may have a small diameter.

As the dimensions of the specific example, the same dimensions as those described in the first and second embodiments can be adopted. The diameter of the hole is, for example, 1.5 mm for the large diameter, 1.2 mm for the intermediate diameter, and 1.0 mm for the small diameter, but is not limited thereto.

In the above-described embodiment, the number of holes provided in the truncated cone is up to two, but three or more types of holes may be provided. However, they are arranged so that the diameter becomes smaller toward the distal end side.

The hole provided in the frustoconical portion is a hole whose diameter changes stepwise, but a tapered hole whose diameter changes continuously, for example, an opening on the flange side is set to 1.
The hole may be 5 mm, the opening on the tip side is 1.0 mm, and a hole between which the diameter changes gradually.

[0031]

As is apparent from the above description, according to the present invention, two or more types of optical fibers having different outer diameters can be gripped and sealed in a pipe by using a rubber bushing formed as one part. it can. In the case of frusto-conical portions formed on both sides, the side not inserted into the pipe, that is, the hole on the side that is not compatible with the optical fiber to be accommodated, gently grasps the optical fiber outside the pipe, and the optical fiber ends at the pipe end. This has the effect of preventing bending to an extremely small diameter.

[Brief description of the drawings]

FIG. 1 is a view for explaining a first embodiment of a rubber bushing of the present invention, and FIG. 1 (A) is a perspective view, FIG.
(B) is a sectional view.

2 (A) is a perspective view for explaining a second embodiment of the rubber bushing of the present invention, and FIG.
(B) is a sectional view.

FIG. 3 is a sectional view of a rubber bushing according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of an example of an optical fiber.

FIG. 5 is a sectional view of an example of a pipe.

6 (A) is a perspective view and FIG. 6 (B) is a cross-sectional view for explaining an example of a conventional rubber bushing.

[Explanation of symbols]

1. Flange, 2, 2a, 2b, 2c ... Hole, 3, 3
a, 3b: frustoconical part, 4: slit, 5: cutting groove, 6
... pipe, 7 ... display.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuo Hokari, Inventor, Nippon Telegraph and Telephone Corporation 3-9-1, Nishishinjuku, Shinjuku-ku, Tokyo (72) Inventor Shinichi Furukawa 3-192, Nishishinjuku, Shinjuku-ku, Tokyo No. Japan Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. A rubber bushing to be inserted into an end of a pipe through which an optical fiber is laid, wherein the rubber bushing has a substantially frustoconical outer portion, and holes having different diameters are continuous in the longitudinal direction. A rubber bushing characterized in that the hole is provided such that the small-diameter hole is on the front end side. 2. A rubber bushing to be inserted into an end of a pipe through which an optical fiber is laid, wherein each of the rubber bushings has a substantially frustoconical outer shape from a center toward both sides, and is provided inside both sides. A rubber bushing wherein holes of different diameters are provided and holes on both sides are connected. 3. A hole provided in at least one of the portions having a truncated cone shape provided on both sides, holes having different diameters are continuous in the longitudinal direction, and the hole has a small diameter. The rubber bushing according to claim 2, wherein the rubber bushing is provided so as to be on the front end side of the outer shape. 4. The rubber bushing according to claim 1, wherein the hole is a hole whose diameter changes stepwise. 5. The rubber bushing according to claim 1, wherein the hole is a hole having a continuously changing diameter.