JP3296966B2 - Telescopic bellows duct - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duct having a stable duct length in a stretched state and a contracted state and a duct shape, and more particularly to a telescopic bellows duct suitable as an air conditioning duct.

[0002]

2. Description of the Related Art A typical form of this kind of duct is (a)
There are two types (b). (A): A metal coil is attached to a duct wall made of a synthetic resin, and a groove is provided in a valley and one of the shoulders in a longitudinal section of the duct wall, and a stable duct length in an extended state and a contracted state is provided. And a telescopic bellows duct having a duct form. (B): A duct wall made of a synthetic resin alone (no coil is used), and the adjacent oblique sides are made to have a relationship between a thick side and a thin side or a long side and a short side. A telescopic bellows duct having a stable duct length in a stretched state and a contracted state, and a duct form, where is a bending point. This type of duct can be compactly contracted when not in use, can be freely adjusted in length when in use, and can retain its shape even when bent.

[0003]

The above-mentioned (a) and (b)
The problems with each type are as follows: (a) When the type is long, there is a problem in that the type cannot be held down by its own weight in the extended state and the contracted state. In addition, since the coil serving as a reinforcing material is made of metal, it is not easy to cut it during duct molding and piping work. Also, disposal is difficult due to the presence of metal. In areas where hygiene is required, rust is a problem. (B) Regardless of the structure, there is no coil as a reinforcing material in any structure, so the crushing in the duct radial direction is very weak, and even when used for air conditioning, the shape is maintained when wind pressure is applied inside the duct. It is not actually used because it can no longer be used. The present invention has been made in view of the above-mentioned problems, and a core material is formed of a highly rigid synthetic resin. It is an object of the present invention to provide a telescopic bellows duct with improved properties and disposability.

[0004]

In order to achieve the above object, a telescopic bellows duct of the present invention is a spiral bellows duct made of polypropylene as a duct wall material. A groove is formed in the shoulder, and polypropylene can be melt-bonded to the duct wall material.
The spiral reinforcing coil is attached to the duct ridge and satisfies the following (A) to (F) in the extended state. (A) In the vertical section of the duct, the ratio of the right and left hypotenuses formed by the duct wall with respect to the groove at the trough of the duct wall is 3: 7 to 7: 3. (B) The pitch / wave height is 1.8 to 3.2 ( C) Wave height / duct outer diameter is 0.02 to 0.1. (D) Duct wall material has a flexural modulus of 2500 to 1000.
0 (kgf / cm ² ) (E) The bending elastic modulus of the coil material is 15000 to 3000
0 (kgf / cm ² ) (F) Wave height / coil core diameter is 1.5 to 5

[0005] da transfected wall material and the coil material is (referred to as PP hereinafter) together polypropylene by based,
In addition to improving weight reduction, bending fatigue resistance, and easy disposal, when the stepped portion is formed on the outer surface of the duct by making the mountain side adjacent to the groove of the shoulder shoulder thick, the expanded state and shrinkage The structure can maintain a more stable duct length and shape in a state.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional telescopic bellows duct to which a carbon steel wire coil is attached has a coil weight occupying about half of the duct weight, although it slightly varies depending on the size. When the coil is made of synthetic resin having the same wire diameter, the coil weight ratio is 1/7
１ ／. In other words, the problem that the present invention is trying to solve, ie, the problem of sagging due to its own weight in the extended state and the contracted state, can be solved by greatly reducing the weight of the duct. Further, not only can it be cut easily, but also it does not contain inorganic substances such as metals, and the disposability is improved.

With reference to the drawings, a detailed description will be given of the relationship between each component and the action in the process of contracting the duct. First, paying attention to the cross-sectional shape of a conventional highly rigid duct having a metallic coil at the time of expansion and contraction, as shown in FIG. 3
When a point link mechanism is configured to apply a compressive force P in the duct axis direction, the link mechanism changes the point 16 from the point 16 to the point 161 to the point 1 by the crank motion of the hypotenuse 18 around the point 17.
62, and the point 161 is associated with the hypotenuse 18
Is deformed to the oblique side 181, causing tension strain inside the resin (oblique side 181) constituting the duct wall, and generating the maximum compressive stress as seen in the compressive stress diagram of FIG. 6 as a repulsive force. In the process from point 161 to point 162,
Contrary to the previous process, the tension strain inside the resin acts in the direction of eliminating, so a negative compressive stress acts and the duct necessarily has a stress relationship that keeps the length and shape in a contracted state .

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 the tensile strain of 81 increases, that is, it is preferable 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, as 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 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.

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 is extended to the maximum extent in the axial direction of the duct and then left without applying 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. , 7 indicate a groove at the mountain shoulder. 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 oblique side of the duct wall that has no groove at the mountain shoulder, and 14 is the oblique side of the duct wall that has a groove at the mountain shoulder. . 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 resin forming the walls of the telescopic bellows duct of the present invention is preferably a resin mainly composed of polypropylene.
It is more preferable to use an elastomer component copolymerized or mixed with the above main component. The flexural modulus was 250
It is preferably from 0 to 10,000 (kgf / cm ² ). When the duct wall material has a flexural modulus of less than 2500 (kgf / cm ² ), the bent portion has a large rubber-like elasticity during the contraction process, and thus attempts to return to the expanded state. Therefore, it cannot be easily held in a contracted state. On the other hand, when the elastic modulus of the duct wall material exceeds 10000 (kgf / cm ² ), the bent portion is whitened, and the bending fatigue resistance is poor.

The material which can be melt-bonded to the duct wall forming the coil not only can reduce the weight but also needs to apply an adhesive to the coil or coat the coil with a synthetic resin which can be melt-bonded to the duct wall material. In general, the same material as the duct wall is used in order to enable easy and stable production. However, a material with a high flexural modulus is required.
Ri, especially 15000~30000 (kgf / ^cm 2)
Is preferred. Although it depends on the coil core diameter, when the bending elastic modulus of the coil material is less than the lower limit , the core material has a low rigidity and tends to bend in the shrinking process, so that it is difficult to maintain a stable duct length in a contracted state. on the other hand,
The bending elastic modulus of the coil material is 30,000 (kgf / c
When the synthetic resin exceeds m 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 , highly crystallized polypropylene is preferable, and polypropylene having rigidity can also be used. When both duct wall material and coil material are PP,
Bending fatigue resistance is also improved, which is effective for weight reduction. The flexural modulus refers to a value obtained by a measuring method according to JIS-K7203.

According to the present invention, in the vertical section of the duct wall forming the duct trough, the ratio of the hypotenuse provided with the groove at the mountain shoulder to the other hypotenuse is 3: 7 to 7: 3. However, the closer to the equal distribution, preferably from 4: 6 to 6: 4,
The pitch in the contracted state is reduced, and the length of the duct when not in use is reduced. In addition, as shown in FIG. 1, when the pitch 10 from the peak 3 to the adjacent peak 3 is divided by the valley 6, as shown in FIG. It refers to the ratio of the length in the axial direction of the hypotenuse 14 provided with a groove in the shoulder portion.

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.

Furthermore, the duct of the present invention has a wave height / duct outer diameter of 0.02 to 0.1. When the value is less than the lower limit, both the pitch and the 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 ratio is small. On the other hand, when the wave height / coil core diameter exceeds 5, the bending elastic modulus of the coil material is 15,000 to 30.
Even if it is 000 (kgf / cm ² ), the coil core diameter is small, so the rigidity is weak and it cannot be contracted and held. The wave height / coil core diameter is preferably 2 or more. Although it depends on the size of the duct, the coil core diameter is preferably selected from 1 mm to 6 mm, and 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,
The telescopic bellows duct of the present invention has an appropriate balance with respect to the pitch or wave height with respect to the diameter, or the thickness with respect to the diameter, and if not balanced, the duct does not meet the purpose of the present invention.

Further, in the duct of the present invention, the shoulder portion adjacent to the groove of the shoulder portion 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. In addition, since the mountain shoulder portion adjacent to the core material is made thick, it can play a role of reinforcing the coil. 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.

[0020]

Examples Examples of the present invention and comparative examples will be described. In the table, those marked with * indicate that the structure deviates from the present invention. Examples 1-3 and Comparative Examples 1-3
A duct tape is formed by winding a PP tape having a flexural modulus of elasticity of 7,000 (kgf / cm ² ) while being extruded and melting and bonding the overlapped portion to form an example product and a comparative example product having an inner diameter of about 65 mm. Obtained. 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 the ratio of the hypotenuse in the vertical section of the duct wall forming the valley portion of the duct was as shown in Table 1. . In the case of the example product, a coil (core diameter: 1.8 mm) formed of highly crystallized PP having a flexural modulus of 20,000 (kgf / cm ² ) was melt-attached to the PP tape inside the crest of the telescopic bellows duct. As for the comparative example, a coil in which a carbon steel wire having a carbon composition ratio of 0.4% by weight was coated with PP was melt-attached to a PP tape, or a coil formed of PP, which deviated from the present invention, was formed. did. The obtained telescopic bellows duct was measured for its sagging / shrinkage retention (in this case, whether it can be held in a contracted state). In the hanging test, as shown in FIG. 7, the hanging distance of 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.

[0021]

[Table 1]

As is clear from the above Examples and Comparative Examples, the telescopic bellows duct constructed according to the present invention can reduce the droop while maintaining the contraction holding property.
In addition, the problems of cutability, disposability, and rust, which were problems of metal coils, can be solved.

[0023]

Since the present invention is constructed as described above, it is possible to reduce the sagging in the stretched state or the contracted state even though it is made of 100% resin, and to reduce the weight and cuttability which are the advantages of the resin. It can make use of the simplicity of improvement and disposal. 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 compressive stress diagram in a shrinking process.

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

[Explanation of symbols]

1 the duct 2 the reinforcing coil 3 crest 4 troughs 5 duct wall 6 valley of the groove 7 Yamakata section groove 8 the thick portion 9 stages drop portion 10 pitch (p) 11 wave height (h) 12 outer diameter (D) 13 Oblique side without groove at mountain shoulder 14 Oblique side with groove at mountain shoulder 15, 16, 17 Bending point 18 Oblique side with groove at mountain shoulder 19 Oblique side without groove at mountain shoulder 20, 21, 22 bent Point 23 hypotenuse with groove on the shoulder 24 hypotenuse without groove on the shoulder

Claims (2)

(57) [Claims] In a spiral bellows duct made of polypropylene as a duct wall material, a groove is provided in a valley portion and one of the shoulder portions of the duct wall in a vertical cross section of the duct, and is made of polypropylene which can be melt-bonded to the duct wall material. A telescopic bellows duct, wherein a spiral reinforcing coil is attached to a duct peak, and the following (A) to (F) are satisfied in an extended state. (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 outside diameter is 0.02 to 0.1 (D) Duct wall material has a flexural modulus of 2500 to 1000
0 (kgf / cm ² ) (E) The bending elastic modulus of the coil material is 15000 to 3000
0 (kgf / cm ² ) (F) Wave height / coil core diameter is 1.5 to 5 2. The telescopic bellows duct according to claim 1, wherein a stepped portion is formed on an outer surface of the duct by making the shoulder portion adjacent to the groove of the shoulder portion thick.