JP2806159B2 - Optical fiber gas pressure head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber gas feed head connected to a pipe for feeding an optical fiber into the pipe by compressed gas, and more particularly to a head seal material.
The present invention relates to an optical fiber having improved shape and improved pumping characteristics.

[0002]

2. Description of the Related Art Generally, in order to lay an optical fiber or an optical unit (hereinafter simply referred to as an optical fiber) in a pipeline, the optical fiber is pressure-fed into the pipeline by a compressed gas such as air. I have. Connect the pumping head to the pipeline,
By sending a compressed gas together with the optical fiber into the head, the optical fiber is pressure-fed into the pipeline. Normally, the head is provided with a seal in order to prevent air leakage and backflow and increase the pumping force.

[0003] For example, a head described in Japanese Patent Publication No. 2-22921 is provided with seals at a leading end on a pipe side and an introducing end on an optical fiber supply side, respectively.
Gas in the hollow passage of the head is prevented from flowing out. It is suggested that these seals include rubber lips and narrow channels.

[0004]

However, the following disadvantages are expected in the seal structure of the conventional head which is suggested to include the rubber lip and the narrow channel described above.

(1) It is provided only to prevent gas leakage and backflow, and no detailed consideration is given to the sealing structure. For this reason, although the sealing effect is tentatively good, the frictional resistance at the seal portion is increased, the pumping speed is not increased, and the long pumping cannot be performed. As described above, the length of the pumping length is not extended by the seal, and the wear during long-length pumping is not considered. Therefore, a set of drive wheels is provided in the head separately from the seal, and a hydrostatic potential is provided. In order to overcome the above, an extremely complicated configuration of grasping and advancing the optical fiber is required.

(2) If the pressure is fed to some extent, the seal portion will soon break and air will leak.

(3) When passing through the seal portion, unit runout occurs.

(4) In addition, since the sealing effect itself is not always sufficient and there is air leakage, annoying noises such as shoe shoes are generated in the operation, which adversely affects the operator. An object of the present invention is to solve the above-mentioned drawbacks of the prior art by optimizing the material and shape of the seal, to reduce the leakage and backflow of compressed gas from the seal, and to reduce the pressure of light that is pumped into the pipeline. An object of the present invention is to provide a novel optical fiber gas pumping head capable of reducing the frictional force with the fiber surface and greatly increasing the pumping force of the optical fiber pumped into the pipeline.

[0009]

SUMMARY OF THE INVENTION An optical fiber gas pumping head according to the present invention has an optical fiber inlet at one end and an optical fiber inlet at the other end connected to the above-mentioned pipe to pressurize the optical fiber into the pipe by compressed gas. In a pressure feed head having a hollow tubular path having an optical fiber outlet and a gas inlet for feeding a compressed gas into the hollow tubular path, a cylindrical shape for preventing gas leakage by inserting an optical fiber into the optical fiber inlet is provided. A seal is provided so that the cylindrical seal satisfies the following conditions. That is, a. The material is a silicone rubber having a Shore A hardness of 20 to 60.

B. The shape is a cylindrical shape with a non-circularity of 0% to 30%, and the inner diameter S is d, where d is the outer diameter of the optical fiber to be pumped.
d ≦ S ≦ d + 0.5 mm , wall thickness 0.5 m
m and 1.5 mm or less, and the length of the portion in contact with the optical fiber is 2 mm or more and 10 mm or less. Here, the length of the portion in contact with the optical fiber is the seal length M of the portion shown in FIG.

Incidentally, an additive for lowering the friction coefficient may be added to the silicone rubber as required. As an additive to be added to the silicone rubber to reduce the coefficient of friction, there is, for example, silicone-grafted polyethylene. The compressed gas includes nitrogen and carbon dioxide in addition to air.

[0012]

[Action] Silicone rubber is preferable as the seal material. This is because a material that easily expands and contracts by pressure is suitable for the sealing material, and silicon rubber is most suitable as such a material. Further, by adding an additive for reducing the coefficient of friction with the optical fiber, the pumping characteristics of the optical fiber can be further improved.

The shape of the seal is preferably cylindrical. This is because the shape of the pressure-receiving light-transmitting fiber is circular in cross section, which prevents air leakage at the seal portion. The non-circular rate is 30%
Until the above, air leakage is prevented, but if it exceeds that, air leakage will occur and the pumping characteristics will deteriorate.

Assuming that the outer diameter of the optical fiber to be pressure-fed is d, the seal inner diameter S is set in the range of d ≦ S ≦ d + 0.5 mm to prevent air leakage and reduce the frictional force. When d> S, air leakage is prevented, but the frictional force increases, making it impossible to pump. Further, when d + 0.5 mm <S, the seal is not sufficiently tightened due to the pressure and air leakage occurs, so that the pressure-feeding characteristics deteriorate.

[0015] Seal thickness is 0.5 mm or more and 1.5 mm
The following have the best pumping characteristics. If it is less than 0.5 mm,
Before the pumping length reaches 500 m, the seal is broken and sufficient pumping cannot be performed. On the other hand, if it exceeds 1.5 mm, the sealing effect is lost, and the length of pressure feeding is not extended.
The seal length needs to be 2 mm or more and 10 mm or less. If it exceeds 10 mm, the tip of the seal will swing, causing air leakage, and the length of pressure feeding will not be extended. When the thickness is 10 mm or less, air leakage can be prevented and the pressure feeding characteristics can be improved. Also, 2mm
If it is less than this, the sealing effect is not obtained. The Shore A hardness of the seal is desirably 20 to 60. If it is 20 or less, it is soft and the friction coefficient becomes large, and if it is 60 or more, it is hard and the rubber does not tighten.

As described above, by limiting the material, shape, and dimensions of the seal, the pressure-feeding characteristics of the optical fiber can be greatly improved and stabilized.

[0017]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view of an optical fiber gas pressure feeding head according to the present embodiment. The head 2 has a straight hollow tubular passage 7 therethrough.
And a gas inlet 3 for feeding a compressed gas obliquely in the middle of the hollow tubular path 7. The hollow tubular passage 7 is a passage for introducing an optical fiber into the head 2 and leading it out together with the compressed air.
And an optical fiber outlet 8 connected to the optical fiber pressure-feeding pipeline 1 at the other end. The hollow tubular path 7 has a diameter large enough to allow the optical fiber to pass through in an idle state.

A guide 5 for smoothly introducing the optical fiber 6 into the hollow tubular path 7 is fitted into the optical fiber inlet 9 at one end of the head 2. As shown, the guide 5 has a protrusion 11 for guiding the optical fiber inside (inside the head), and the cylindrical seal 4 is attached to the protrusion 11. Therefore, the hollow tubular path 7 on the side of the introduction port 9 into which the guide 5 is fitted forms a chamber 10 having a size that allows the seal 4 to be mounted. The seal of the optical fiber outlet 8 may be a narrow channel suggested in the prior art or other known means.

As shown in FIG. 2, the cylindrical seal 4 has a cylindrical shape, and one end of the cylindrical seal 4 is pushed into the guide projection 11 so as to be expanded and mounted. Is to prevent. The following requirements are imposed on the seal 4 in order to reduce gas leakage, backflow and frictional force. FIGS. 4 to 7 show measurement data for determining the seal size and hardness, which are the basis for imposing this requirement. These are all pressures of 9k into a 1000m long pipeline.
FIG. 4 is a characteristic diagram showing a relationship between a pumping length and a seal size when an optical fiber is pumped at gf / cm ² . From these characteristic diagrams, it can be seen that the seal dimensions need only be within the following ranges.

First, as the material of the seal, use is made of silicone rubber or a material to which an additive such as silicon graft polyethylene is added to reduce the friction coefficient. The Shore A hardness is, as shown in FIG.

Next, the shape of the seal is a non-circularity of 0% to 30%.
Cylindrical shape. Assuming that the outer diameter of the optical fiber to be pumped is d, the seal inner diameter S is in the range of d ≦ S ≦ d + 0.5 mm where the pumping length does not decrease as shown in FIG. FIG.
As shown in FIG. 6, the wall thickness is set to a fixed length of 0.5 mm or more and 1.5 mm or less, and as shown in FIG.
Is not less than 2 mm and not more than 10 mm.

With respect to specific seal dimensions, since the outer diameter of the optical fiber 6 used for pressure feeding is 1.8 mm, the inner diameter is 2.
0 mm, wall thickness 0.75 mm, and seal length 3 mm.
The optical fiber 6 is pressure-fed to the optical fiber pressure-feeding pipeline 1 using the pressure-feeding head 2 equipped with such a seal 4, and
It was possible to feed 1000 m to a tube wound around a 0φ drum. Note that these specific values and the range of the above values only need to be satisfied at least in the portion of the seal length M, and the mounting portion may be out of the above range.

According to the present embodiment, the cylindrical seal is a moving object because not only gas leakage is prevented, but also the length of the pumping length is increased, and the friction at the time of long length feeding is carefully considered. The sealing effect on the optical fiber is also sufficient, and in addition to this, the frictional resistance of the seal portion is reduced, the speed of pumping is improved, and long pumping is possible. In addition, since this is realized only by the material and dimensions of the seal itself, there is no need to incorporate complicated parts such as a drive wheel into the head as in the conventional case, and the pumping length can be reduced while having an extremely simple configuration. Can be stretched.

Also, the backflow of the compressed gas from the seal is small, so that even if the pumping distance is extended, the seal portion is not broken and air does not leak. In addition, since the seal length is set properly, there is no unit run-out when passing through, and there is no air leakage. It can be eliminated and a good working environment can be maintained.

In the above embodiment, the case where the thickness and the inner diameter of the cylindrical seal are constant in the longitudinal direction has been described.
The thickness and inner diameter may change in the longitudinal direction. Further, the seal structure may be a multilayer structure. For example, the inner layer is made of silicone rubber, and the outer layer is made of PE (polyethylene), PVC
(Polyvinyl chloride), polyamide or acrylic resin.

[0026]

According to the present invention, the backflow of compressed gas from the seal is prevented by preventing air leakage and minimizing the frictional force between the surface of the optical fiber fed into the conduit and the seal. By reducing the size, the pumping force of the optical fiber pumped into the pipeline can be greatly increased, and the pumping length can be significantly increased. In addition, since there is no air leakage, gas leakage noise is eliminated and the working environment can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical fiber gas pressure head according to an embodiment of the present invention.

FIG. 2 is a perspective view of a seal according to the embodiment.

FIG. 3 is a side view of a guide provided with a seal according to the embodiment.

FIG. 4 is a characteristic diagram of a pressure feeding length with respect to a seal inner diameter according to the embodiment.

FIG. 5 is a characteristic diagram of a pumping length with respect to a seal thickness according to the embodiment.

FIG. 6 is a characteristic diagram of a pressure feeding length with respect to a seal length according to the embodiment.

FIG. 7 is a characteristic diagram of a feeding length with respect to a seal hardness according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe for optical fiber pressure feed 2 Pressure feed head 3 Compressed gas inlet 4 Cylindrical seal 5 Guide 6 Optical fiber 7 Hollow tubular path 8 Optical fiber outlet 9 Optical fiber inlet 10 Chamber 11 Guide projection

Claims (2)

(57) [Claims] 1. A hollow tubular passage having an optical fiber inlet at one end and an optical fiber outlet at the other end connected to the conduit for pumping an optical fiber into the conduit by a compressed gas;
In a pressure feed head having a gas inlet for feeding compressed gas into the hollow tubular passage, a cylindrical seal for preventing gas leakage by inserting an optical fiber into the optical fiber inlet is provided, and the cylindrical seal has the following conditions. An optical fiber gas-feeding head characterized by satisfying the following. a. The material is silicone rubber with a Shore A hardness of 20-60. b. The shape is a cylindrical shape with a non-circularity of 0% to 30%, and the inner diameter S is d ≦ d if the outer diameter of the optical fiber to be pumped is d.
S ≦ d + 0.5 mm , the wall thickness is in the range of 0.5 mm to 1.5 mm, and the length of the portion in contact with the optical fiber is in the range of 2 mm to 10 mm. 2. The optical fiber according to claim 1, wherein the cylindrical seal has a multilayer structure, the inner layer is made of silicone rubber, and the outer layer is made of a synthetic resin such as polyethylene, polyvinyl chloride, polyamide or acrylic resin. Pneumatic pump head.