JPH11166672A - Transparent expansion bellows duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce weight, to prevent the occurrence of hanging-down in an expanded state even in the long size, and to hold a shape of a contracted state by forming a reinforcing coil of at least one kind of transparent resin, and setting haze of a duct not more than a specific value. SOLUTION: This expansion bellows duct 5 is formed of a transparent resin such as polypropylene, and a reinforcing coil 2 is formed of a transparent resin such as high density polyethylene considering transparency. Weight is reduced by improving bending fatigue resistance by selecting such a transparent resin. The expansion duct is improved in transparency and an beautiful appearance by setting haze not more than 10%. As a structure of the expansion duct 5, a step-down part 9 is formed on a duct outside surface by forming a crest- shaped part adjacent to a groove of the crest-shaped part as a thick part 8. Therefore, stress easily concentrates only on the groove and the stepped-down part in a contracting/expanding process. Therefore, the stable length and a shape can be held at duct expansion time and contracting time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent telescopic bellows duct which can be easily observed in the duct, is lightweight and has excellent shape retention, and is particularly useful as an air conditioning duct.

[0002]

2. Description of the Related Art Conventionally, typical types of ducts of this kind are classified into three types (a), (b) and (c). (A): A telescopic bellows duct in which a metal coil is attached to a duct wall made of a synthetic resin, and grooves are provided in a valley portion and a mountain shoulder portion of the duct wall in a vertical section of the duct. (B): An elastic bellows duct composed only of a duct wall made of a synthetic resin (no coil is used) and having adjacent oblique sides in a relation of thick and thin or long and short sides. This duct can be compactly contracted when not in use, can be freely adjusted in length when in use, and can maintain its shape even in a bent state. (C): An elastic bellows duct in which a coil made of a synthetic resin such as highly crystallized polypropylene is attached to a duct wall made of a synthetic resin, and grooves are formed in a valley portion and a shoulder portion of the duct wall in a vertical section of the duct.

[0003]

However, the above (a),
The (b) and (c) types have the following problems. The type (a) is heavy because the coil serving as a reinforcing material is made of metal. If the coil is long, the coil hangs down due to its own weight, and the shape cannot be maintained. Also, it is not easy to cut during duct molding and piping work because of the presence of metal. When discarded by incineration, the metal coil remains without burning. Further, in the field where hygiene is required, metal rust is generated. The (b) type has no coil that plays the role of a reinforcing material, so that the duct is very weak in crushing in the radial direction, and cannot be maintained in shape when a negative pressure is applied to the duct even when used for air conditioning. Therefore, it is not actually used. The type (c) uses highly crystallized polypropylene or the like as the coil, and therefore has insufficient transparency, so that the inside of the duct cannot be easily observed. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made to reduce the weight by using a transparent resin as a coil serving as a reinforcing material. In addition to providing a telescopic bellows duct that is easy to cut and dispose of, it is possible to understand the movement of the fluid flowing inside the duct and make it aesthetic by using not only coils but also ducts with transparent resin. Another object of the present invention is to provide a telescopic bellows duct that can be deployed in piping in the interior field, in the field of electronic devices, and further in the field of medical devices.

[0004]

The object of the present invention is to provide a spiral bellows duct having a duct wall made of a transparent resin and a reinforcing coil, wherein the reinforcing coil is made of high-density polyethylene, methacrylic resin, polycarbonate, polyester, polyamide and styrene resin. By providing a transparent telescopic bellows duct having a haze of the duct of 10% or less, the valley portion and the shoulder portion of the duct wall in the vertical section of the duct are coils made of at least one transparent resin selected from the group consisting of: This is achieved by providing a groove and providing a transparent telescopic bellows duct that satisfies the following (A) to (F) in the extended state of the duct. (A) The ratio of the right and left hypotenuses formed by the duct wall with respect to the groove at the valley of the duct wall in the vertical section of the duct is 3: 7 to 7: 3. (B) The spiral pitch / wave height is 1.8 to 3.2. (C) Wave height / duct outer diameter is 0.02-0.1 (D) Flexural modulus of duct wall material is 2,500-10,
000 (kgf / cm ² ) (E) The bending elastic modulus of the coil material is 10,000 to 40,
000 (kgf / cm ² ) (F) Wave height / coil core diameter is 1.5 to 5

[0005] More preferably, the structure is such that a more stable form can be maintained by forming a stepped portion on the outer surface of the duct by increasing the thickness of the ridge portion adjacent to the groove of the ridge portion. It is.

[0006]

Next, the present invention will be described in detail. FIG. 1 is a partially cutaway front view showing the duct in an extended state according to the present invention. The extended state refers to a state in which the duct maintains a stable length and shape without receiving any external force. FIG. 2 is a partial cross-sectional view of the contracted state, wherein 1 is a duct body, 2 is a reinforcing coil, 3 is a bellows crest, 4 is a bellows valley, 5 is a duct wall, and 6 is a trough groove. ,
Reference numeral 7 denotes a groove at the top of the mountain. In FIG. 1, reference numeral 10 denotes a helical pitch (P), and reference numeral 11 denotes a wave height (distance between a peak and a valley:
H)), 12 is the outer diameter (D) of the duct, 13 is the hypotenuse on the side of the duct wall that does not have a groove, and 14 is the hypotenuse on the side that has a groove on the top of the duct wall. . The duct in FIG.
When a force in the compression direction is applied, it bends at the grooves 6 and 7,
It contracts as shown in FIG. 2 and is held in that form.

The transparent resin forming the wall of the elastic bellows duct of the present invention includes polypropylene, polyethylene, high density polyethylene, medium density polyethylene, low density polyethylene, methacrylic resin, polycarbonate, polyester, polyamide and styrene resin. -Based copolymer resin (acrylonitrile-butadiene-
Transparent resins such as styrene copolymer resin, acrylonitrile-styrene copolymer resin) and the like can be mentioned, but it is preferable that the material of the duct wall is mainly composed of a synthetic resin having a relatively small specific gravity, for example, based on polypropylene. Things are good. Although it differs somewhat depending on the type of the transparent resin, it is preferable to use an elastomer component as a copolymer or a mixture with the above main component. The flexural modulus of the duct wall material is
It is preferably from 2,500 to 10,000 (kgf / cm ² ). The flexural modulus of the duct wall material is 2,500 (kgf /
If it is less than ² cm ² , the bent portion tends to have a large rubber-like elasticity during the contraction process, so that it tries to return to the elongated state. Therefore, it cannot be easily held in a contracted state. On the other hand, flexural modulus of duct wall material (JIS K7203)
Exceeds 10,000 (kgf / cm ² ), whitening occurs in the bent portion, resulting in poor bending fatigue resistance.

It is important that the coil is transparent, and the density of the coil is 1.3 g / cm ³ or less, especially 1.2 g / cm ^3.
/ Cm ³ or less. Also, the fact that the coil can be melt-bonded to the duct wall, and especially that the temperature at which both can be melt-bonded is close to each other, is to apply an adhesive to the coil or coat it with a resin that can be melt-bonded to the duct wall material. There is no need to easily and stably produce,
It is suitable. However, a coil material having a high flexural modulus is required, and it is required to be 10,000 to 40,000.
(Kgf / cm ² ) is preferred. Although it depends on the coil core diameter, the bending elastic modulus of the coil material is 10,000.
When it is less than (kgf / cm ² ), the core material has a low rigidity, and in the shrinking process, it is likely to bend and a stable duct length in a shrunk state cannot be maintained. On the other hand, if the coil material is made of a resin having a flexural modulus of more than 40,000 (kgf / cm ² ), the rigidity of the core is increased, but the impact strength is reduced, so that the core is easily broken. As the coil material, at least one transparent resin selected from high-density polyethylene, methacrylic resin, polycarbonate, polyester, polyamide and styrene resin is used. Here, high-density polyethylene is a density of 0.93 g / cm ³ or more,
It is preferably 0.94 g / cm ³ or more, more preferably 1.3 g / cm ^3.
cm ³ or less, preferably 1.2 g / cm ³ or less. Examples of the styrene resin include polystyrene and styrene copolymer resins (acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, etc.). Among these transparent resins, high-density polyethylene is optimal, improves bending fatigue resistance, and is effective for weight reduction. The telescopic duct of the present invention has a haze of 10%.
It is important that the haze is less than 8%. In particular, since the haze is 8% or less, a bellows duct excellent in transparency and aesthetics can be obtained. The optimum haze is less than 6%.

Next, according to the present invention, in a vertical section of a duct wall forming a duct valley, a hypotenuse having a groove at a mountain shoulder is provided;
Although the ratio of the other hypotenuse is set to 3: 7 to 7: 3, it is preferably 4: 6 to 6: 4. The duct length becomes shorter. Note that the ratio of the hypotenuse is, as shown in FIG. 1, a pitch 10 from the peak 3 to the adjacent peak 3.
Is divided by the valley 6, the ratio of the length in the axial direction of the hypotenuse 13 having no groove at the peak and the hypotenuse 14 having the groove at the peak.

Further, in the present invention, the pitch / wave height is set to 1.8 to
It is necessary to form 3.2. When the pitch / wave height is less than the lower limit, the tensile strain on the hypotenuse where the groove is provided at the mountain shoulder in the compression process becomes too small, and the value of the maximum compressive stress becomes lower. In other words, drooping increases because it is likely to easily enter the contracted state and the extended state. On the other hand, if the value exceeds the upper limit, it cannot be fixed in the contracted state.

Further, the duct of the present invention has a wave height / duct outer diameter of 0.02 to 0.10. If the value is less than the lower limit, both the pitch and wave height are small, and if the thickness is constant, the rigidity of the hypotenuse against bending becomes too high, so that the duct form in the contracted state cannot be maintained. Conversely, when the value exceeds the upper limit, both the pitch and the wave height increase, and when the thickness is kept constant, the rigidity of the hypotenuse against bending becomes too low, and the sag increases.

In the present invention, when the wave height / coil core diameter is less than 1.5, the coil core diameter is too large, so that the expansion / contraction ratio is small. On the other hand, when the crest height / coil core diameter exceeds 5, the bending elastic modulus of the coil material is 10,000 to
Even at 40,000 (kgf / cm ² ), the coil core diameter is small, so the rigidity is weak, and it cannot be contracted and held.
Although the coil core diameter depends on the size of the duct, it is 1 to 6
mm, more preferably from 1 to 4 mm.

Such a duct has a spiral shape,
Continuous molding is possible, and long products can be molded. However,
In the telescopic bellows duct of the present invention, it is necessary to properly balance the pitch or wave height with respect to the diameter, or the thickness with respect to the diameter.

In the duct of the present invention, the mountain shoulder adjacent to the groove of the mountain shoulder is formed as a thick portion 8 as shown in FIG.
In the case where the stepped portion 9 is formed on the outer surface of the duct, stress is easily applied only to the portion where the groove and the step are dropped in the contraction process and the extension process, and only the valley portion and the portion can be a bending point. Therefore, the stress is not dispersed except the groove and the stepped part,
A stable length and shape can be maintained when the duct is extended and contracted. Further, the thickness of the shoulder portion adjacent to the core material is increased, so that the coil can play a reinforcing role. Furthermore, even if the groove is formed shallow for the reasons described above, the bending point is easy to be determined, so that it is resistant to bending fatigue.

Referring to the drawings, the relationship between each component and the action in the process of contracting the duct will be described. First, focusing on the cross-sectional shape of a conventional highly rigid duct having a metal coil at the time of expansion and contraction, as shown in FIG. When a compressive force P is applied in the direction of the duct axis, the link mechanism changes the point 16 from the point 16 to the point 161 to the point 161 by the crank motion of the hypotenuse 18 around the point 17.
At the point 161, the hypotenuse 18 is deformed to the hypotenuse 181 to cause tension strain inside the resin (oblique 181) constituting the duct wall. Generates the maximum compressive stress. On the other hand, in the process from point 161 to point 162, the tension strain in the resin acts in the opposite direction to the previous process, so that a negative compressive stress acts, and the duct is inevitably lengthened in a contracted state. And a stress relationship that maintains the form.

Therefore, when the sag is to be reduced by a coil having a high rigidity such as a metal, it can be maintained if the maximum value of the compressive stress shown in FIG. To increase the maximum value, the hypotenuse 1
It has been found that it is preferable to increase the tensile strain of 81, that is, to make the hypotenuse 18 and the hypotenuse 19 in the longitudinal section of the duct wall forming the valley of the duct as close as possible to the distribution, and to lower the wave height with respect to the pitch. .

However, in the case of a coil having a lower rigidity than a metal such as a synthetic resin, if the tensile strain of the hypotenuse 181 increases, the maximum value of the compressive stress shown in FIG. 151), the coil loses its maximum compressive stress, and if the compressive force P is further increased, the coil is bent and cannot be contracted.

Accordingly, the present invention slightly lowers the maximum value of the compressive stress shown in FIG. 6 for a low rigidity material such as a synthetic resin core material. That is, the tension strain of the hypotenuse 231 in FIG.
That is, the wave height is increased with respect to the pitch of the oblique sides 23 and 24 in the longitudinal section of the duct wall forming the valley of the duct,
It is preferred that the coil not lose its maximum compressive stress. The problem of sag can be solved by reducing the weight. Also, by adopting the above structure,
A duct that is strongly crushed in the duct radial direction can be obtained.

[0019]

Examples Examples of the present invention and comparative examples will be described. Examples 1 to 3 and Comparative Example 2 A tape made of polypropylene (PP) having a flexural modulus of 7,000 (kgf / cm ² ) was turned while being extruded, and a duct wall was formed by melting and bonding the overlapped portions. At the same time, the coils shown in Table 1 were melt-adhered to obtain examples and comparative examples having an inner diameter of about 65 mm. The grooves at the valleys and the shoulders were formed by dies during tape extrusion. The shoulder portion adjacent to the groove of the shoulder portion was made thick to form a stepped portion on the outer surface of the duct, and a duct as shown in Table 1 was obtained. In addition, for the product of the example, a bending elastic modulus of 16,000 (kgf / cm
² ) A coil (core diameter 1.8 mm) formed of high-density polyethylene (PE) (Example 1), a flexural modulus of 20,000
00 coil (core diameter 1.8 mm) formed by styrene-based resin (kgf / cm ²⁾ (Example 2), flexural modulus 2
A coil (core diameter: 1.8 mm) formed of a polyamide of 000 (kgf / cm ² ) was melt-attached to form a duct. For the comparative example, carbon content 0.4
A coil in which a carbon steel wire of weight% was coated with PP (Comparative Example 1) and an opaque coil made of highly crystalline polypropylene (Comparative Example 2) were each melt-attached to form a duct. The obtained telescopic bellows duct was measured for its sagging and shrinkage retention (whether or not it can be held without stretching when it is in a contracted state). In the hanging test, as shown in FIG. 7, the hanging distance at the tip of the duct was measured with a test length of 50 cm in an extended state. In addition, the temperature condition was measured without blowing air into the duct at room temperature of 25 ° C. Table 1 shows the obtained results. In addition, all of the examples were light in weight and had good cutting performance with scissors.

[0020]

[Table 1]

[0021]

The telescopic bellows duct of the present invention can easily observe the inside of the duct, is lightweight, has little drooping in the extended state, and has good shape retention in the contracted state.
Furthermore, it has excellent cutting properties and disposal properties. Furthermore, by making the shoulder portion adjacent to the groove of the shoulder portion thick, and forming a stepped portion on the outer surface of the duct, the thick portion of the shoulder portion adjacent to the core material serves as a reinforcing material In addition, even if the groove is shallow, it is possible to obtain a holding force in an extended state and a contracted state that is almost the same as a deep state, and to solve the duct durability due to bending fatigue, which was a problem when the groove was deep. Can be.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing a duct extension state of the present invention.

FIG. 2 is a partial cross-sectional view illustrating a contracted state of the duct according to the present invention.

FIG. 3 is a partial sectional view showing another embodiment of the duct of the present invention.

FIG. 4 is a partial simplified cross-sectional view of a comparative example illustrating an operation.

FIG. 5 is a partial simplified cross-sectional view of the embodiment explaining the operation.

FIG. 6 is a view showing a compressive stress in a contraction process.

FIG. 7 is a diagram illustrating a sag test method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Duct 2 Reinforcement coil 3 Crest part 4 Valley part 5 Duct wall 6 Valley part groove 7 Mountain shoulder groove 8 Thickness part 9 Step drop part 10 Pitch (p) 11 Wave height (h) 12 Outer diameter (D) 13 Slope with no groove at the shoulder 14 Slope with groove at the shoulder 15, 16, 17 Bending point 18 Slope with groove at the shoulder 19 Slope without groove at the shoulder 20, 21, 22 Bend Point 23 hypotenuse with groove on the shoulder 24 hypotenuse without groove on the shoulder

Claims (3)

[Claims] 1. A spiral bellows duct having a duct wall made of a transparent resin and a reinforcing coil, wherein the reinforcing coil is at least one transparent material selected from high-density polyethylene, methacrylic resin, polycarbonate, polyester, polyamide and styrene resin. A transparent telescopic bellows duct, wherein the duct is a coil made of resin and the haze of the duct is 10% or less. 2. The transparent telescopic bellows duct according to claim 1, wherein a groove is provided in a valley portion and a mountain shoulder portion of the duct wall in the vertical section of the duct. 3. The transparent telescopic bellows duct according to claim 1, which satisfies the following (A) to (F) when the duct is extended. (A) The ratio of the right and left hypotenuses formed by the duct wall with respect to the groove at the valley of the duct wall in the vertical section of the duct is 3: 7 to 7: 3. (B) The spiral pitch / wave height is 1.8 to 3.2. (C) Wave height / duct outer diameter is 0.02-0.1 (D) Flexural modulus of duct wall material is 2,500-10,
000 (kgf / cm ² ) (E) The bending elastic modulus of the coil material is 10,000 to 40,
000 (kgf / cm ² ) (F) Wave height / coil core diameter is 1.5 to 5