JP3290737B2 - Bobbin for winding optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bobbin used for winding and storing and transporting an optical fiber, and is capable of controlling a temperature change in a certain range allowed during storage and transport. In addition, it is possible to reliably prevent the optical fiber strand wound around the bobbin from being broken.

[0002]

2. Description of the Related Art The winding drum of a bobbin for winding an optical fiber is usually made of plastic or metal, and an optical fiber having an extremely small coefficient of thermal expansion is formed with a predetermined winding force. It is wound up. If the tension applied to the optical fiber at the time of winding the optical fiber is too weak, the winding may be loosened due to temperature change during storage and transport, and the winding may collapse due to vibration during transport. The measured value of the transmission loss test of the optical fiber strand, which is performed while being wound, becomes a value larger than the original transmission loss of the optical fiber strand, thereby increasing the possibility of defective products due to the transmission loss test. Conventionally, in order to balance the above two contradictory sides, in order to make the transmission loss test result as close as possible to the original transmission loss result, the winding of the optical fiber at the time of winding as much as possible without causing collapse of the winding. The attachment force (tension applied to the optical fiber) is reduced. However, considering the loosening due to the difference in thermal contraction between the winding drum and the optical fiber due to the temperature change, with the winding force of the strength that allows for the above loosening while sacrificing the result of the transmission loss test to some extent I have to take it up. This loosened winding has a lower temperature during use (during transport, transmission loss test, etc.) than the temperature during winding, and the winding drum shrinks greatly compared to the shrinkage of the optical fiber, resulting in light from the winding drum. Since this is caused by the loss of the support force of the fiber strand in the radially outward direction, there is no other way than to compensate for the reduction of the support force by the winding drum by other means in order to prevent this.

[0003]

SUMMARY OF THE INVENTION According to the present invention, the transmission loss in a transmission loss test is reduced as much as possible by reducing the increment of the winding force of the optical fiber at the time of winding by considering the temperature change. It is an object of the present invention to minimize the loosening of an optical fiber due to a temperature change.

[0004]

Means taken to solve the above problems are constituted by the following elements (a) and (b). (A) The synthetic resin winding drum constituting the bobbin is covered with an elastic cylindrical material. (B) The material of the elastic cylindrical material has a coefficient of thermal expansion k ₂ satisfying the following expression. .

[Equation 3] Here, R is a value satisfying the following equation.

[Equation 4] The symbols in the above formula are as follows. r: radius of the winding drum (mm), k ₁ : coefficient of thermal expansion of the winding drum (1 / ° C.), E ₁ : Young's modulus of the winding drum (g / mm ² ), d: elastic cylindrical material wound on the bobbin Thickness (mm), k ₂ : coefficient of thermal expansion of elastic cylindrical material wound on bobbin (1 /
° C), E ₂ : Young's modulus of elastic cylinder material wound on bobbin (g / m
m ² ), a: Width (m) of linear body (optical fiber, same hereafter)
m), k ₃ : coefficient of thermal expansion of the linear body (1 / ° C.), E ₃ : Young's modulus of the linear body (g / mm ² ), S: cross-sectional area of the linear body (mm ² ), T: The winding tension of the linear body (g).

[0005]

[Operation] The above formulas for calculating the conditions include the temperature and winding force at the time of winding of everything related to the temperature change, the change in diameter and length due to the temperature change, and the change in the amount of elastic deformation due to the winding force. Since all the requirements such as changes in internal stress and the like that affect the rigidity of the winding of the optical fiber are incorporated, the temperature at the time of winding and the temperature at the time of use (for example, at the time of transmission loss test) are 1
Even if the angle is reduced by 0 degrees, the support force of the elastic cylindrical member toward the outside in the radial direction with respect to the cylindrical bundle of the optical fiber wires does not become zero. That is, the elastic cylindrical member compensates for the reduction of the outer diameter due to the temperature change of the winding drum, thereby preventing the winding force of the optical fiber around the winding drum from becoming zero. Therefore, if the temperature drop is 10 degrees or less, the winding will not collapse due to loose winding regardless of the reduction in the outer diameter of the winding drum due to the temperature change. The details of the above operation will be described phenomenally with reference to FIG. 1 as follows. An outer periphery 2 of an elastic cylindrical material such as a sponge is compressed to 2 'shown by a dotted line by applying tension to an optical fiber (hereinafter referred to as a linear body). At this time, the outer circumference 1 of the winding cylinder is also compressed by the winding force of the linear body, but since the Young's modulus of the winding cylinder is much larger than that of the elastic cylindrical material, the compression amount is extremely smaller than the compression amount of the elastic cylindrical material. . When the temperature during transport or the like is lower than the temperature during winding, the winding drum, the elastic cylindrical member, and the linear body wound around the elastic cylindrical member contract at the respective rates of thermal expansion. Since the coefficient of thermal expansion k ₃ of the linear body is extremely smaller than the coefficients of thermal expansion k ₁ and k ₂ of the winding cylinder and the elastic cylindrical material, when the outer periphery of the winding cylinder contracts to the position shown by the dotted line 1 ′, the elasticity is increased. Although the cylindrical material also thermally contracts, the inner circumference of the elastic cylindrical material, which has been greatly compressed by the tightening force of the linear body, elastically restores inward in the radial direction, following the contraction of the outer circumference of the winding drum, and the heat of the winding drum is reduced. Compensate for shrinkage. Although the elastic cylindrical material elastically rebounds inward in the radial direction, the supporting force of the elastic cylindrical material with respect to the linear body is reduced. However, as long as the coefficient of thermal expansion k ₂ satisfies the relationship of the above equation, the temperature drop is 10 Below this degree, the bearing capacity does not become zero. Next, the basis of the above equation will be described with reference to FIG. The change in the diameter of the winding cylinder and the diameter of the linear body (optical fiber) wound on the winding cylinder are caused by a change in temperature and a change in the winding tension of the linear body. T temperature of the winding body at the time of winding the linear body is from t ₀
When it is lowered, the winding cylinder contracts, and the amount of contraction becomes (k ₁ r
+ K ₂ d) (t ₀ −t). Temperature t ₀ ′, winding tension T,
The magnitude of the thermal contraction of the linear body wound with the winding radius R is k ₃
Is R (t ₀ '-t). Further, since the linear body is wound by the tension T, the linear body is wound in an extended state by the tension T. When the winding drum contracts, the tension of the linear body decreases, and when the tension becomes zero, the amount of reduction in the winding diameter due to the relaxation of the tension is R {1-1 / (1 + T / SE ₃ )}. The basis for this equation is as follows. When the radius R of the linear body wound around the winding drum and the free length of the linear body for one winding are L, tension T, and elongation ε, 2πR = L (1 + ε). Assuming that the cross-sectional area of the linear body is S, ε = σ / E = 1 / E × T / S. From this, L = 2πR /
(1 + T / SE ₃ ) When T = 0, the linear body has a free length, and the radius at this time is R ′ = L / 2π. Radius change amount RR ′ = RL−2π = RR− (1+
T / SE ₃ ) = R {1-1 / (1 + T / SE ₃ )}. Next, R will be described. The radius of one layer of the innermost layer in a state where the linear body is wound on the winding drum corresponds to the above R. Width a
Is wound around the winding drum with the tension T, the stress perpendicularly applied to the winding drum outer peripheral surface by the linear body wound directly on the winding drum outer peripheral surface becomes T / Ra (this is Since it is a well-known general formula, a description of the grounds derived will be omitted.) Since this stress is applied to the outer peripheral surface of the elastic cylindrical member 11 and further to the outer peripheral surface of the winding drum 10, the winding drum 10 and the elastic cylindrical member 11 are respectively r (1
−T / RaE ₁ ) and d (1−T / RaE ₂ ). Here, d is the thickness of the elastic cylindrical member in the free state. When the linear body 12 is wound around the outer peripheral surface of the elastic cylindrical member having a radius of r + d with a tension T in a free state, the radius is R, so that

[Equation 5] Becomes Since this is a quadratic equation for R, solving this gives

[Equation 6] Becomes In order to prevent the linear body wound on the outer periphery of the elastic cylindrical member from being extremely collapsed due to a temperature drop after the winding, the radius of the outer periphery of the elastic cylindrical member after the heat shrinkage is determined by the line after the heat shrinkage. The minimum necessary condition is that the tension is larger than the winding diameter of the linear body at which the tension of the body becomes zero. If this condition is expressed by an equation,

[Equation 7] Becomes In this equation, t: temperature during use (° C.), t ₀ : temperature of the winding drum at the time of winding the linear body (° C.), t ₀ ′: temperature of the linear body at the time of winding the linear body ( ° C), and assuming that the temperature drop is 10 degrees, t ₀ -t = 10
Because

[Equation 8] Becomes That is, even if the material is selected so that the coefficient of thermal expansion k ₂ of the elastic cylindrical material satisfies the above relationship, the temperature decreases by 10 degrees from the winding temperature. Never goes to zero.

[0006]

EXAMPLE Next, a specific example will be described. Regarding the winding drum, the radius of the bobbin winding drum was 150 mm, material: synthetic resin (name: ABS resin), thermal expansion coefficient k ₁ = 0.0001 / ° C., Young's modulus E ₁ = 200 kg / mm ² . Elastic cylindrical material, a belt-shaped elastic member having a thickness of 5 mm lightly wound around a winding drum, Material: foamed resin (namely foamed polyethylene), coefficient of thermal expansion k ₂ = 0.0002 / ° C., Young's modulus E ₂ = 30 g / mm ² . Regarding the linear body (optical fiber), the width a of the linear body is 1.1 mm, the effective sectional area S is 0.049 mm ² , and the coefficient of thermal expansion k ₃ of this linear body is 0.0000005 /
° C, Young's modulus E ₃ = 7300 kg / mm ² , temperature of the linear body during winding t ₀ ′ = 25 ° C. Regarding the winding conditions, the winding drum temperature during winding t ₀ = 25 ° C., the winding tension T = 150 g, and the winding length: 10 km. Regarding the test results, ten bobbins wound under the above conditions were prepared, and the bobbins were cooled to 15 ° C., which is 10 ° C. lower than the winding temperature, and a vibration test was performed. As a result, no one had collapsed. Ten bobbins to be compared were prepared by winding the same linear body on the same bobbin as above (with no elastic cylindrical material wound) under the same conditions, and this was set at 10 to the winding temperature. The vibration test was performed by lowering the temperature by 15 ° C. to 15 ° C. As a result, two pieces had a roll collapse, and eight pieces did not have a roll collapse.

[0007]

[Effect] As described above, by estimating the temperature at the time of transportation and use, it is possible to reliably prevent loosening and collapse of the winding under the temperature condition. Therefore, the filament (optical fiber) can be wound up with the minimum necessary tension, thereby producing an effect such that the inherent transmission loss of the filament can be accurately measured. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining an operation of the present invention.

FIG. 2 is an explanatory diagram for explaining an operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Outer circumference of winding cylinder 1 '... Outer circumference when contraction of winding cylinder 2 ... Outer circumference of elastic cylindrical material 2' ... Outer circumference when elastic cylindrical material is compressed 10 ... Winding Body 11: Elastic cylindrical material 12: Linear body (optical fiber)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-117924 (JP, A) JP-A-4-352107 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H 75/14 G02B 6/00 336

Claims (1)

(57) [Claims] 1. An optical fiber in which a winding cylinder made of a synthetic resin constituting a bobbin is covered with an elastic cylindrical material, and the material of the elastic cylindrical material has a coefficient of thermal expansion k ₂ satisfying the following expression. Bobbin for winding. [Equation 1] Here, R is a value satisfying the following equation. [Equation 2] The symbols in the above formula are as follows. r: radius of the winding drum (mm), k ₁ : coefficient of thermal expansion of the winding drum (1 / ° C.), E ₁ : Young's modulus of the winding drum (g / mm ² ), d: elastic cylindrical material wound on the bobbin Thickness (mm), k ₂ : coefficient of thermal expansion of elastic cylindrical material wound on bobbin (1 /
° C), E ₂ : Young's modulus of elastic cylinder material wound on bobbin (g / m
m ² ), a: Width (m) of linear body (optical fiber, same hereafter)
m), k ₃ : coefficient of thermal expansion of the linear body (1 / ° C.), E ₃ : Young's modulus of the linear body (g / mm ² ), S: cross-sectional area of the linear body (mm ² ), T: The winding tension of the linear body (g).