Helmet and chinstrap

Abstract

To provide a helmet in which a chin strap of a helmet is hardly stretched against a tensile load.SOLUTION: There is provided a helmet comprising a cap body and a chin strap 11 provided inside the cap body. The chin strap 11 is woven in a cord shape with a plurality of warp yarns 11B and a plurality of weft yarns, and the plurality of warp yarns 11B includes first warp yarns made of first fibers and second warp yarns 20B made of second fibers made of ultra-high molecular weight polyethylene, and the second fibers have a higher tensile strength and modulus than the first fibers, and the weft yarns are composed of the first fibers.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a helmet and a chin strap.

Background Art

[0002] In a motorcycle helmet, a pair of chin straps are attached to the inside of the helmet body. The chin straps are attached to the helmet body via chin-strap mounting brackets (see, for example, Patent Document 1). The length of the chin straps is adjusted by a strap length adjuster. Thereby, the chin straps hold the helmet body in close contact with the wearer's head.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The chin straps need to hold the helmet body so that it does not come off from the wearer's head even in an emergency where a strong load acts on the helmet body. From the viewpoint of more suitably exhibiting the shock absorption performance of the helmet in an emergency, a configuration in which the chin straps are less likely to stretch under a tensile load is desired in order to maintain the state where the helmet body and the wearer's head are in close contact as much as possible.

[0005] For example, by increasing the width or thickness of the chin straps to make the chin straps thicker, the chin straps can be made less likely to stretch under a tensile load. However, when the chin straps are made thicker, problems such as an increase in weight and a decrease in flexibility occur.

Means for Solving the Problems

[0006] A helmet for solving the above problems includes a helmet body and a chin strap disposed inside the helmet body. The chin strap is woven into a string shape by a plurality of weft threads and a plurality of warp threads. The plurality of warp threads include a first warp thread made of a first fiber and a second warp thread made of a second fiber made of ultra-high molecular weight polyethylene. The second fiber has a higher tensile strength and elastic modulus than the first fiber, and the weft thread is composed of the first fiber.

[0007] According to the above configuration, in the chin strap, since the warp threads include the first warp thread and the second warp thread, the elongation of the chin strap can be reduced by the second warp thread, and the chin strap can be made to have a good texture by the first warp thread.

[0008] In the above helmet, a configuration may be adopted in which a plurality of the second warp threads are arranged at equal intervals in the extending direction of the weft thread. According to the above configuration, in the chin strap, since a plurality of the second warp threads are arranged at equal intervals in the extending direction of the weft thread, the tensile load applied to the chin strap can be made uniform in the extending direction of the weft thread. Therefore, the tensile load can be suitably dispersed by the first warp thread and the second warp thread constituting the warp thread.

[0009] In the above helmet, the chin strap may be configured to include a string length adjustment part for adjusting the length. The second warp thread has a property of being more slippery than the first warp thread. According to the above configuration, since the warp thread includes the first warp thread and the second warp thread, even if a string length adjustment part is provided, the elongation of the chin strap can be reduced while suppressing the slippage of the chin strap with respect to the string length adjustment part.

[0010] In the above helmet, the string length adjustment part may be made of stainless steel. According to the above configuration, in the chin strap, fastening fittings such as buckle rings and D-rings constituting the string length adjustment part can be made of a lightweight and high-strength metal material such as stainless steel.

[0011] In the warp threads, the ratio of the surface area occupied by the second warp thread may be greater than 0% and at most 43.6%. According to the above configuration, in the warp threads of the chin strap, since the ratio of the surface area occupied by the second warp thread is at most 43.6%, while suppressing the elongation of the chin strap, slipping of the chin strap with respect to the fastening fitting through which the chin strap is inserted is suppressed.

[0012] In the warp threads, the ratio of the surface area occupied by the second warp thread may be greater than 0% and at most 23.0%. According to the above configuration, in the warp threads of the chin strap, since the ratio of the surface area occupied by the second warp thread is at most 23.0%, while suppressing the elongation of the chin strap, slipping of the chin strap with respect to the fastening fitting through which the chin strap is inserted is suppressed.

[0013] The chin strap for solving the above problems is a chin strap used for a helmet disposed inside a cap body, wherein the chin strap is woven in a string shape by a plurality of weft threads and a plurality of warp threads, and the plurality of warp threads include a first warp thread composed of a first fiber and a second warp thread composed of a second fiber made of ultra-high molecular weight polyethylene. The second fiber has a higher tensile strength and elastic modulus than the first fiber, and the weft thread is composed of a fiber made of the polyester.

Advantages of the Invention

[0014] According to the above configuration, it is possible to make the chin strap of the helmet less likely to elongate with respect to a tensile load.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0016] Hereinafter, the helmet to which the present invention is applied will be described with reference to the drawings. In FIG. 1, the front, rear, left, right, up, and down, which are the directions seen from the helmet wearer, are shown as the front, rear, left, right, up, and down with respect to the helmet.

[0017] As shown in FIG. 1, the helmet 1 is a full - face type helmet. The helmet 1 includes a cap body 2 and a pair of jaw string units 10 on the left and right. The cap body 2 constitutes the outer shell of the helmet 1. The cap body 2 is a resin member having a hemispherical shape. Inside the cap body 2, for example, an impact - absorbing member made of foamed resin (for example, expanded polystyrene) and an interior pad made of urethane foam are provided.

[0018] The cap body 2 includes a first opening 2A and a second opening 2B. The first opening 2A is formed in the front region of the cap body 2. The first opening 2A secures the wearer's field of vision. A shield 3 having light - transmissivity is provided in the first opening 2A. The second opening 2B is formed in the lower region of the cap body 2. The second opening 2B is an opening for inserting the wearer's head.

[0019] Each jaw string unit 10 includes a jaw string 11, a coupling member 12, a string length adjusting part 13, and a jaw string mounting fitting 14. The jaw string 11 is a string-shaped member formed by sewing chemical fibers configured in a filament shape. The jaw string 11 includes a first end portion attached to the cap body 2 via the jaw string mounting fitting 14, and a second end portion led out from the second opening 2B.

[0020] The coupling member 12 is a member provided at the second end portion of the jaw string 11. As an example, the coupling member 12 is a one-touch type ratchet buckle. Specifically, in one of the pair of jaw string units 10, a ratchet, which is an example of the coupling member 12, is provided at the second end portion of the jaw string 11. In the other of the pair of jaw string units 10, a buckle, which is an example of the coupling member 12, is provided at the second end portion of the jaw string 11. When the ratchet is inserted into the buckle, the ratchet and the buckle are coupled, whereby the pair of jaw string units 10 on the left and right are connected.

[0021] The string length adjusting part 13 has a function of adjusting the length of the portion led out from the second opening 2B of the jaw string 11. As an example, the string length adjusting part 13 is an annular tightening fitting such as a cock ring or a D-ring. In the present embodiment, a cock ring is used. The string length adjusting part 13 has two holes arranged in the extending direction of the jaw string 11, which is configured by partitioning the inside of the frame into two regions by a shaft. The jaw string 11 is inserted through the two holes provided in the string length adjusting part 13. Note that the string length adjusting part 13 may be provided only in one of the pair of jaw string units 10 on the left and right, or may be provided in both of the jaw string units 10. Cock rings and the like are usually formed of stainless steel, for example, SUS304.

[0022] Each jaw string attachment fitting 14 is fixed to the left and right inner peripheral surfaces of the cap body 2 by a fixing member 4. The fixing member 4 is, for example, a screw or a rivet. The jaw string attachment fitting 14 includes a fixing hole through which the fixing member 4 is inserted and an insertion hole through which the jaw string 11 is inserted. The jaw string attachment fitting 14 is fixed to the cap body 2 by caulking the fixing member 4 with the shaft portion of the fixing member 4 inserted through the fixing hole and the attachment hole penetrating the cap body 2.

[0023] [Jaw string] As shown in FIG. 2, the jaw string 11 is woven in a string shape by bag weaving a plurality of types of chemical fibers. The jaw string 11 has a sleeve shape by bag weaving. The jaw string 11 does not have a string member or the like for enhancing the strength against tensile load inserted inside the sleeve, so as to simplify the configuration and not impair the flexibility. Against the tensile load, as will be described below, it is made difficult to stretch by weaving the second warp 20B. Hereinafter, with reference to FIG. 3, the detailed structure of the jaw string 11 will be described.

[0024] As shown in FIG. 3, the jaw string 11 is constituted by weaving a plurality of weft threads 11A and a plurality of warp threads 11B. The weft thread 11A extends in the first direction which is the short side (width) in the jaw string 11. The weft thread 11A is constituted by a thread member in which first fibers made of polyester are twisted together. The thread member is, for example, a twist of two fibers. The first fibers made of polyester are an example of chemical fibers and have excellent weather resistance such as being difficult to absorb water and being difficult to deteriorate by sunlight.

[0025] The warp thread 11B extends in the second direction which is the long side in the jaw string 11. The warp thread 11B includes a first warp 20A and a second warp 20B. In the warp thread 11B, for example, the first warp 20A is used more than the second warp 20B.

[0026] The first warp thread 20A, like the weft thread 11A, is composed of a yarn member in which first fibers made of polyester are twisted together. The second warp thread 20B is composed of a yarn member in which second fibers made of ultra-high molecular weight polyethylene are twisted together. As an example, the first warp thread 20A and the second warp thread 20B have the same thickness, but they may have different thicknesses.

[0027] Both the first warp thread 20A and the second warp thread 20B are, as an example, twisted yarns of two fibers. The first fibers constituting the weft thread 11A and the first warp thread 20A are, for example, Tetoron (registered trademark), which is an example of polyester. Also, the second fibers constituting the second warp thread 20B are, for example, Izanas (registered trademark), which is an example of ultra-high molecular weight polyethylene.

[0028] The second fibers made of ultra-high molecular weight polyethylene are an example of chemical fibers and, in addition to excellent weather resistance, have excellent mechanical properties such as high tensile strength and high elastic modulus compared to the first fibers. The first fibers are more flexible and have a better texture than the second fibers.

[0029] The second warp thread 20B is provided, for example, arranged at equal intervals in the first direction. The jaw strap 11 has a sleeve shape, and as an example, on two opposite surfaces, the second warp threads 20B are arranged at equal intervals. In FIG. 3, three first warp threads 20A are arranged between the second warp threads 20B. In addition, the jaw strap 11 may have a configuration in which 20 first warp threads 20A are arranged between two adjacent second warp threads 20B over the entire circumference, a configuration in which 10 are arranged, a configuration in which 8 are arranged, a configuration in which 3 are arranged, a configuration in which 2 are arranged, and so on.

[0030] [Method of Wearing a Helmet] When wearing the helmet 1, first, the wearer inserts their head into the inside of the helmet body 2 through the second opening 2B. Next, by connecting the coupling members 12 provided on each of the pair of jaw strap units 10 below the wearer's jaw, the pair of jaw strap units 10 are connected. Thereby, the wearing of the helmet 1 is completed. The length of the jaw strap 11 is adjusted by the strap length adjustment part 13.

[0031] [Relationship between elongation in the chinstrap and content of the second fiber in the warp thread] The chinstrap 11 includes the second warp thread 20B in the warp thread 11B, making it difficult to stretch even when a load in the direction of coming off the wearer's head acts on the cap body 2.

[0032] On the other hand, when a load in the direction of coming off the wearer's head acts on the entire chinstrap unit 10 with respect to the cap body 2, the chinstrap 11 inserted through the string length adjustment portion 13 may be tightened so as to increase the length of the portion led out from the second opening 2B against the frictional force with the string length adjustment portion 13. In addition to the above-described characteristics, the second fiber constituting the second warp thread 20B has a characteristic of being more slippery than the first fiber constituting the first warp thread 20A and the weft thread 11A. Therefore, although the second warp thread 20B is necessary to suppress the elongation of the chinstrap 11 with respect to the tensile load, if the area of the second warp thread 20B exposed on the surface is excessively large, the static friction coefficient and the dynamic friction coefficient between the chinstrap 11 and the string length adjustment portion 13 in the string length adjustment portion 13 become too small. Therefore, it is preferable that the area of the second warp thread 20B exposed on the surface is such that the friction coefficient between the chinstrap 11 and the string length adjustment portion 13 does not decrease excessively.

[0033] Therefore, in the warp thread 11B, the appropriate ratio of the first warp thread 20A and the second warp thread 20B was confirmed by checking the changes in the static friction coefficient and the dynamic friction coefficient accompanying the change in the surface area ratio between the first warp thread 20A and the second warp thread 20B. The static friction coefficient serves as an index of the holding force (slip start load of the chinstrap 11) of the chinstrap 11 tightened by the string length adjustment portion 13 in the string length adjustment portion 13. Also, the dynamic friction coefficient serves as an index of the ease of stopping the chinstrap 11 that has slipped out with respect to the string length adjustment portion 13 (braking force with respect to the slipped-out chinstrap 11). The surface area ratio here is the ratio of the surface area occupied by the second warp thread 20B in the warp thread 11B.

[0034] FIG. 4 is a diagram showing the relationship between the surface area ratio of the second warp thread 20B in the warp thread 11B and the static friction coefficient and the dynamic friction coefficient between the chinstrap 11 and the surface plate. Surface area ratio of sample A... 0% (does not contain the second fiber 20B.) Surface area ratio of sample B... 6.0% (including the second fiber 20B). Surface area ratio of sample C... 9.9% (including the second fiber 20B). Surface area ratio of sample D... 11.8% (including the second fiber 20B). Surface area ratio of sample E... 23.0% (including the second fiber 20B). Surface area ratio of sample F... 30.1% (including the second fiber 20B). Surface area ratio of sample G... 43.6% (including the second fiber 20B). Surface area ratio of sample H... 65.9% (including the second fiber 20B). Here, the surface area ratio is calculated as follows.

[0035] Considering the fiber (raw yarn) before twisting as a single cylinder, the cross-sectional area A (mm 2 ) of a single fiber is expressed as in Equation (1) using the fiber diameter X (dtex) and the density ρ (g / cm 3 ). Note that 1 dtex is the weight (g) per 10,000 m of unit length in the fiber.

[0036]

Number

[0037] Also, the circumference L (mm) of the fiber is expressed as in Equation (2) when the diameter of the fiber is D (mm).

[0038]

Number

[0039] Then, using the circumference L (mm) of the fiber, the surface area S1 of the first fiber and the surface area S2 of the second fiber per unit length in the second direction are calculated. For example, in a unit length of 1 mm in the second direction, the surface area S1 (mm 2 ) of the first fiber is expressed as S1 = L1 using the circumference L1 of the first fiber. Similarly, in a unit length of 1 mm in the second direction, the surface area S2 (mm 2) is represented as S2 = L2 using the circumference L2 of the second fiber.

[0040] Also, the surface area ratio S r (%) of the second warp 20B in the warp 11B is expressed as in Equation (3) using the sum S T1 of the surface areas of the first warp 20A in the warp 11B and the sum S T2 of the surface areas of the second warp 20B. Also, the sum S T1 of the surface areas of the first warp 20A in the warp 11B is expressed as in Equation (4) using the surface area S1 of the first fiber, the number a1 (twist number) of the first fibers constituting the first warp 20A, and the number b1 of the first warps 20A constituting the warp 11B. Similarly, the sum S T2 of the surface areas of the second warp 20B in the warp 11B is expressed as in Equation (5) using the surface area S2 of the second fiber, the number a2 (twist number) of the second fibers constituting the second warp 20B, and the number b2 of the second warps 20B constituting the warp 11B.

[0041] [Number]

[0042] [Number]

[0043] [Number]

[0044] Note that when calculating the surface area ratio S r of the second warp 20B in the warp 11B, the area of the portion covered by the weft 11A in the first warp 20A and the second warp 20B is ignored. Also, in Equations (4) and (5), since the jaw string 11 has a sleeve shape, 1 / 2 is multiplied by the surface area S1 of the first fiber and the surface area S2 of the second fiber to obtain only the area of the outer surface of the sleeve shape.

[0045] The first warp yarn 20A used for Samples A to H is composed of two twisted first fibers. The first fiber used for Samples A to H has a fiber diameter D of 1100 dtex and a density ρ of 1.38 g / cm 3 . The second warp yarn 20B used for Samples A to H is composed of two twisted second fibers. The second fiber used for Samples A to H has a fiber diameter D of 1320 dtex and a density ρ of 0.97 g / cm 3 .

[0046] Also, the static friction coefficient and kinetic friction coefficient of Samples A to H with respect to the surface plate were measured using a tensile testing machine as shown in Fig. 5. The tensile testing machine 30 includes a surface plate 31 on which Samples A to H are placed, a weight 32 placed on Samples A to H, a measuring unit 33 for measuring the frictional force of Samples A to H with respect to the surface plate 31, a connecting thread 34 connecting the measuring unit 33 and Samples A to H, and a pulley 35.

[0047] The specific conditions are as follows. Tensile testing machine: Minebea TG-50kN Surface plate: UNI SEIKI U-9090 Test speed: 100 mm / min Test end point (displacement): 60 mm Sample length: 25 cm Weight mass: 2 kg Vertical resistance force generated by the weight mass: 19.6 N Friction coefficient = Frictional force (N) / Vertical resistance force (N) Then, the static friction coefficient and kinetic friction coefficient were calculated using the frictional force and the vertical resistance force generated by the weight mass. For Samples A to H, tests were conducted on 4 samples each, and the average values were taken as the static frictional force and kinetic frictional force.

[0048] FIG. 6 shows the relationship between the surface area ratio of the second warp 20B in Samples A to H and the static friction coefficient with the surface plate 31 of Samples A to H. As is clear from FIG. 6, in Samples A to G, the static friction coefficient falls within the range of 0.193 to 0.172 (saturated state). However, when it becomes larger than 43.6%, which is the surface area ratio of Sample G, a clear decrease in the static friction coefficient is observed. Therefore, from the viewpoint of suppressing the reduction of the static friction coefficient, it is preferable that the surface area ratio of the second warp 20B in the warp 11B is 43.6% or less. Thereby, it becomes difficult for the jaw string 11 to slip with respect to the ladle ring through which the jaw string 11 is inserted. That is, the holding force of the jaw string 11 in the string length adjusting section 13 can be increased.

[0049] FIG. 7 shows the relationship between the surface area ratio of the second warp 20B in Samples A to H and the dynamic friction coefficient with the surface plate 31 of Samples A to H. As is clear from FIG. 7, in Samples A to E, the dynamic friction coefficient falls within the range of 0.165 to 0.157 (saturated state). However, when it becomes larger than 23.0%, which is the surface area ratio of Sample E, a clear decrease in the dynamic friction coefficient accompanying the increase in the surface area ratio is observed. Therefore, from the viewpoint of suppressing the reduction of the dynamic friction coefficient, it is preferable that the surface area ratio of the second warp 20B in the warp 11B is 23.0% or less. Thereby, it becomes easy for the jaw string 11 to stop with respect to the ladle ring through which the jaw string 11 is inserted.

[0050] In the above test, the static friction coefficient and kinetic friction coefficient of the jaw string 11 with respect to the surface plate 31 are calculated. On the other hand, in the jaw string unit 10, it is necessary to consider the friction between the jaw string 11 and the stirrup that constitutes the string length adjustment unit 13. Generally, the frictional force tends to increase as the area of the part in contact with the mating surface (true contact area) increases. Also, the true contact area tends to decrease as the hardness of the two contacting surfaces increases, and tends to increase as the hardness of the two contacting surfaces decreases. In the above test, a cast iron surface plate 31 is used as the mating surface in contact with the jaw string 11. In contrast, the string length adjustment unit 13 is often made of stainless steel (for example, SUS304), whether it is a D-loop or a stirrup. Although cast iron and stainless steel are different metals, their hardness (Brinell hardness: converted to HBW) is approximately the same, with cast iron being 160 - 180 HB and SUS304 being 187 HB. Therefore, it is considered that the static friction coefficient and kinetic friction coefficient in the friction between the jaw string 11 and the D-loop or stirrup are almost the same as those in the friction between the jaw string 11 and the surface plate 31.

[0051] To confirm this point, the surface area ratio of the second warp 20B in the warp 11B and the kinetic friction coefficient in the stirrup, which is an example of the jaw string 11 - string length adjustment unit 13, were confirmed. Fig. 8 is a diagram showing the relationship between the surface area ratio of the second warp 20B in the warp 11B and the kinetic friction coefficient in the stirrup, which is an example of the jaw string 11 - string length adjustment unit 13.

[0052] Fig. 9 is a diagram showing the tensile testing machine 40. The tensile testing machine 40 includes a surface plate 41 on which samples A - H are placed, a stirrup, which is an example of the string length adjustment unit 13, placed on the samples A - H, a weight 42 configured integrally with the stirrup, a measurement unit 43 for measuring the frictional force of the samples A - H, a connecting thread 44, and a pulley 45. Also, the connecting thread 44 connects the stirrup and the measurement unit 43. Further, both ends of the samples A - H are fixed to the surface plate 41 by fixing members 46 such as adhesive tapes. Note that the specific conditions and test methods of the test are the same as those in the case of the test using the tensile testing machine 30 in Fig. 5.

[0053] FIG. 10 shows the relationship between the surface area ratio of the second warp 20B in samples A to H and the coefficient of kinetic friction with a cockle, which is an example of the string length adjuster 13 for samples A to H. As is clear from FIG. 10, in samples A to E, the coefficient of kinetic friction falls between 0.246 and 0.239 (saturated state). However, when it becomes larger than 23.0%, which is the surface area ratio of sample E, a clear decrease in the coefficient of kinetic friction accompanying the increase in the surface area ratio is observed. That is, the relationship between the surface area ratio of the second warp 20B and the coefficient of kinetic friction of the jaw string 11 - cockle shows the same tendency as the relationship between the surface area ratio of the second warp 20B and the coefficient of kinetic friction of the jaw string 11 - surface plate 31. Therefore, it is considered that the relationship between the surface area ratio of the second warp 20B and the coefficient of static friction of the jaw string 11 - cockle also shows the same tendency as the relationship between the surface area ratio of the second warp 20B and the coefficient of static friction of the jaw string 11 - surface plate 31.

[0054] 〔Effects of the Embodiment〕 The above embodiments can obtain the following listed effects. (1) In the jaw string 11, since the warp 11B includes the first warp 20A and the second warp 20B, while reducing the elongation of the jaw string 11 by the second warp 20B, the jaw string 11 can be made to have a good texture by the first warp 20A. The jaw string 11 can be made less likely to elongate with respect to the tensile load as the amount of the second warp 20B increases.

[0055] (2) In the jaw string 11, since a plurality of the second warps 20B are provided at equal intervals in the extending direction of the weft, the tensile load applied to the jaw string 11 can be made uniform in the extending direction of the weft 11A. Therefore, the tensile load can be suitably dispersed by the first warp 20A and the second warp 20B constituting the warp 11B.

[0056] (3) The second warp thread 20B has a property of being more slippery than the first warp thread 20A. By providing the warp thread 11B with the first warp thread 20A and the second warp thread 20B, even if the string length adjustment part 13 is provided, it is possible to make the jaw string 11 less slippery with respect to the string length adjustment part 13 while reducing the elongation of the jaw string 11 with respect to the tensile load. That is, it is possible to suppress the string length adjustment part 13 from moving in a direction in which the length of the portion led out from the second opening 2B in the jaw string 11 slides and increases with respect to the jaw string 11.

[0057] The jaw string 11 has a sleeve shape in which two layers overlap, and the two layers overlap in a separated state from each other at positions other than the folded-back part connecting the two layers. When forces from various directions such as when putting on and taking off the helmet 1 are applied to the jaw string 11, one layer may repeatedly shift with respect to the other layer. And by repeating the movement of these layers, the relative position between the buckle and the jaw string 11 may move, and there is a possibility that the length of the portion led out from the second opening 2B may become longer with respect to the jaw string 11. In this regard, the jaw string 11 has a surface ratio of the first warp thread 20A and the second warp thread 20B set to a predetermined ratio, so that the two layers are less slippery. Therefore, it is possible to suppress the length of the portion led out from the second opening 2B from moving in a direction in which it increases with respect to the jaw string 11 due to the buckle sliding with respect to the jaw string 11.

[0058] (4) The buckle constituting the string length adjustment part 13 can be made of a lightweight and high-strength metal material such as stainless steel. (5) In the warp thread 11B of the jaw string 11, by making the surface area ratio occupied by the second warp thread 20B larger than 0%, the elongation of the jaw string 11 with respect to the tensile load can be reduced.

[0059] (6) In the warp thread 11B of the jaw string 11, by setting the surface area ratio of the second warp thread 20B to 43.6% or less, the static friction coefficient with respect to the cock ring constituting the string length adjustment part 13 reaches a saturation state. When the surface area ratio of the second warp thread 20B exceeds 43.6%, the static friction coefficient significantly decreases as the surface area ratio increases, that is, it becomes easier to slide with respect to the cock ring. Therefore, by adjusting the surface area ratio of the second warp thread 20B within the range of 43.6% or less, it is possible to make it difficult to stretch with respect to the tensile load of the jaw string 11 without reducing the static friction coefficient.

[0060] (7) In the warp thread 11B of the jaw string 11, by setting the surface area ratio of the second warp thread 20B to 23.0% or less, in addition to the static friction coefficient with respect to the cock ring constituting the string length adjustment part 13, the dynamic friction coefficient reaches a saturation state. When the surface area ratio of the second warp thread 20B exceeds 23.0%, the dynamic friction coefficient significantly decreases as the surface area ratio increases, that is, it becomes easier to slide with respect to the cock ring. Therefore, by adjusting the surface area ratio of the second warp thread 20B within the range of 23.0% or less, it is possible to make it difficult to stretch with respect to the tensile load of the jaw string 11 without reducing the dynamic friction coefficient.

[0061] Note that the above embodiments can be further appropriately modified and implemented as follows. · The surface area ratio of the second warp thread 20B may be made larger than 23.0% or 43.6%. In this case, the jaw string 11 becomes easier to slide with respect to the string length adjustment part 13. In such a case, the string length adjustment part 13 is provided with a locking claw or the like and bites it into the jaw string 11. Thereby, the jaw string 11 can be made difficult to slide with respect to the string length adjustment part 13.

[0062] · The string length adjustment part 13 may be constituted by a D-ring instead of a cock ring, or may be other fastening fittings. Also, the cock ring or D-ring may be made of a metal other than stainless steel, or may further be a molded product of synthetic resin.

[0063] · From the jaw strap unit 10, the strap length adjustment part 13 may be omitted. In this case, the length of the jaw strap 11 cannot be adjusted. In this case, the length of the jaw strap 11 is adjusted according to the wearer and then the jaw strap unit 10 is attached to the cap body 2. Also, a jaw strap unit 10 with a predetermined length is attached to the cap body 2.

[0064] · In the jaw strap 11, the second warp threads 20B may not be arranged at equal intervals in the extending direction of the weft thread 11A. For example, when the jaw strap 11 is a bag weave, the second warp threads 20B may be provided at equal intervals only on the surface opposite to the surface in contact with the wearer's skin. Thereby, it is possible to suppress a decrease in the touch feeling due to the use of the second warp threads 20B.

[0065] · In the bag - woven jaw strap 11, the intervals between the plurality of second warp threads 20B do not all have to be the same. For example, the opposing surfaces may have the plurality of second warp threads 20B provided at equal intervals, and at the folded - back part connecting the opposing surfaces, the second warp threads 20B may be provided at different intervals, for example, with a wider interval. Also, the folded - back part may be composed only of the first warp thread 20A and the second warp threads 20B may be omitted.

[0066] · In addition to the first warp thread 20A and the second warp thread 20B, the warp threads may further include a third warp thread, a fourth warp thread,... made of different fibers. Thereby, the strength, elongation, slipperiness, touch feeling, etc. of the jaw strap 11 can be adjusted.

[0067] · In the warp thread 11B, the first warp thread 20A may be less than or the same as the second warp thread 20B. · The jaw strap 11 may have a flat - strap shape such as a plain weave instead of a bag shape.

[0068] · As the first fiber, it may be a synthetic resin fiber such as nylon instead of polyester. ·The helmet 1 is not limited to a full-face helmet. For example, it may be a flip-up helmet with an adjustable jaw, an open-face helmet, a helmet with a detachable jaw, or a convertible helmet with a rotatable jaw that can be fixed to the back of the head.

Explanation of Signs

[0069] 1…Helmet 2…Helmet body 10…Jaw strap unit 11…Jaw strap 11A…Weft 11B…Warp 12…Coupling member 13…Strap length adjuster 14…Jaw strap mounting bracket 20A…First warp 20B…Second warp

Claims

1. A helmet comprising a cap body and a chin strap disposed inside the cap body, wherein the chin strap is woven in a string shape by a plurality of weft threads and a plurality of warp threads, the plurality of warp threads include a first warp thread made of a first fiber and a second warp thread made of a second fiber made of ultra-high molecular weight polyethylene, the second fiber has a higher tensile strength and elastic modulus than the first fiber, and further has a property of being more slippery than the first fiber, the weft threads are composed of the first fiber, furthermore, the chin strap is a string length adjuster through which the chin strap is inserted into a hole portion, and includes the string length adjuster for adjusting the length, in the warp threads, the ratio of the surface area occupied by the second warp thread is greater than 0% and not more than 43.6% Helmet.

2. In the chin strap, a plurality of the second warp threads are arranged at equal intervals in the extending direction of the weft threads The helmet according to Claim 1.

3. The string length adjuster is made of stainless steel The helmet according to Claim 1.

4. In the warp threads, the ratio of the surface area occupied by the second warp thread is greater than 0% and not more than 23.0% The helmet according to any one of Claims 1 to 3.

5. A chin strap used for a helmet disposed inside a cap body, wherein the chin strap is a string length adjuster through which the chin strap is inserted into a hole portion, and includes the string length adjuster for adjusting the length, the chin strap is woven in a string shape by a plurality of weft threads and a plurality of warp threads, the plurality of warp threads include a first warp thread made of a first fiber and a second warp thread made of a second fiber made of ultra-high molecular weight polyethylene, the second fiber has a higher tensile strength and elastic modulus than the first fiber, and further has a property of being more slippery than the first fiber, the weft threads are composed of the first fiber, in the warp threads, the ratio of the surface area occupied by the second warp thread is greater than 0% and not more than 43.6% Chin strap.

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