JP2016078529A - Foamed non-puncture tube, method for fitting thereof, mold for core back injection molding, and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve weight reduction, wear resistance, support stabilization for rim, and facilitation of fitting in a tire by molding a toric foamed non-puncture tube through a core back injection molding method.SOLUTION: A toric foamed non-puncture tube C is molded by a core back injection molding method comprising filling an original cavity Kformed by a movable mold Fand a stationary mold Fwhen the former advances with a thermoplastic elastomer molten material including a foaming agent using a mold Afor core back injection molding, and then foaming the thermoplastic elastomer molten material M in a maximum cavity Kincreased by retreating the movable mold F. A skin layer 2 unfoamed or having a low foaming scale factor compared to a general part is formed on the whole area of an outer peripheral face in a surface layer part.SELECTED DRAWING: Figure 6-B

Description

  The present invention relates to a foamed no-puncture tube that is molded by a core back injection molding method and is mainly fitted into a bicycle tire, a fitting method thereof, a core back injection mold, and an injection molding method.

  As typical prior art documents regarding the no-puncture tube, there are Patent Documents 1 to 8, and in order to prevent wobbling of the no-puncture tube with respect to the rim, the rim is directly or via a separate member (Patent Documents 1 and 8). A structure that is brought into contact with the bottom portion of the head is adopted. The no puncture tubes disclosed in Patent Documents 2 and 7 are for motorcycles, the no puncture tube disclosed in Patent Document 3 is for forklifts, and the no puncture tubes disclosed in the remaining patent documents are all bicycles. It is for.

  In addition, all of the no-puncture tubes disclosed in Patent Documents 1 to 3 and 7 are annular in shape, and except for Patent Document 1, all the remaining no-puncture tubes directly contact the bottom of the rim. Since the structure is in contact with each other, when the no-puncture tube is fitted into the rim, the ratio of the diameter expansion due to elastic deformation increases, and there is a problem that it is difficult to fit the no-punk tube into the rim.

  The no-puncture tubes disclosed in Patent Documents 4 to 6 and 8 are all fitted into the tire outer skin by deforming the rod-like body into an annular shape, so that it is easy to fit into the tire outer skin, It is necessary to bond both ends of the rod-shaped body by bonding or the like, and if the bonding state of the both ends of the rod-shaped body is poor, the grounding state of this part will be different compared to the other parts, which is a bicycle ride. The comfort was reduced.

  On the other hand, from the aspect of molding material, each of the no-puncture tubes disclosed in Patent Documents 3 and 8 is made of rubber and thermoplastic elastomer, and the no-punk tubes disclosed in the remaining patent documents are both made of foamed rubber. It is. In particular, the no-puncture tube made of foamed rubber has the disadvantage that it is worn and partially deformed due to repeated large frictional contact with the inner peripheral surface of the tire skin due to the tire contact pressure. The life of the tube was reduced, and the ride comfort as a bicycle was reduced.

  As the comparative examples 1 to 8 for the foamed no-puncture tube according to the present invention, the “shape”, “material”, “wobble prevention structure” and “integralness of the rim portion” of the no-puncture tube disclosed in Patent Documents 1 to 8 described above are as follows. It is shown in the table of FIG.

Japanese Patent Laid-Open No. 9-2014 JP 2001-97003 A JP-A 63-219403 JP-A-8-197906 JP-A-10-329228 Japanese Patent Laid-Open No. 10-329229 JP 2007-276621 A JP 2010-111378 A

  In the present invention, an annular foamed no-puncture tube (hereinafter sometimes simply referred to as “tube”) is molded by a core back injection molding method, thereby reducing weight, wear resistance, stabilizing the rim, and It is an object to facilitate the fitting of the tire.

  The invention according to claim 1 for solving the above-described problems is a core in which an annular molding space having a cross section corresponding to the cross section of the tube is formed between the movable mold and the stationary mold when the core is backed. Using a back injection mold, after filling the original cavity containing the foaming agent into the original cavity formed with the fixed mold when the movable mold is advanced, the movable mold is core-backed. Molded by the core back injection molding method in which the thermoplastic elastomer raw material is foamed in the increased maximum cavity, and the foaming ratio is low or unfoamed compared to the foam main part, and is formed on the entire outer peripheral surface. It is characterized in that the wear resistance is enhanced by the skin layer, and the resilience is exerted by the foamed main portion.

  According to the first aspect of the present invention, the foamed non-punctured tube is formed by foaming a thermoplastic elastomer raw material to which a foaming agent is added by a core back injection molding method. The foaming ratio is lower than that of the main part, or an unfoamed skin layer is formed. The skin layer formed on the surface layer of the tube has higher hardness than the foam main part and has wear resistance, and the foamed non-punctured tube includes the ground contact part and includes the inner peripheral surface of the tire outer skin. The strength of the entire surface of the portion that comes into contact with the tube is increased, and the wear resistance of the tube is increased, whereby the durability of the foamed puncture tube is increased. On the other hand, the foam main part, which is the majority of the remaining part excluding the skin layer of the surface layer, is reduced in weight as a tube at the same time as the required resilience (elasticity) is obtained by foaming the thermoplastic elastomer. The

  The invention of claim 2 is characterized in that, in the invention of claim 1, the thickness of the skin layer is 0.5 to 4.0 mm.

  In the invention of claim 2, if the thickness of the skin layer is less than 0.5 mm, the strength is small and the durability as a tube is low, and if it exceeds 4.0 mm, the deformability becomes poor, and the rim and tube The wear of the tire outer skin between the two parts increases.

  A third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the expansion ratio of the thermoplastic elastomer is 1.5 to 3.5.

  In the invention of claim 3, if the foaming ratio of the thermoplastic elastomer is less than 1.5, foaming is insufficient, so the tube becomes heavy and impractical, and if the foaming ratio exceeds 3.5, the foam As the void ratio becomes too large, the strength as a tube decreases, and the durability is insufficient.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, when the tube is fitted into the tire outer shell, the tube enters the inner side by a predetermined length from the outer peripheral end surface of the tire rim, and the rim opening is formed. It is characterized by being supported at the opposed inner end.

  According to the fourth aspect of the present invention, by supporting the tube at the opposed inner end of the rim opening, the inner diameter of the tube is increased, the volume of the tube is decreased, and as a result, the tube is reduced in weight. Also, a skin layer is formed on the entire outer peripheral surface of the tube, and the grounding portion of the tube is formed in a substantially arc shape that follows the inner peripheral surface of the grounding portion of the tire outer skin, Since the tube is easily integrated, the tube can be supported without wobbling even if the tube is supported on the opposite inner end of the rim opening without contacting the bottom of the rim. Further, since the inner diameter of the tube is increased, it is easy to get over the rim of the tube when the tube is fitted to the tire rim, and the fitting operation of the tube to the rim is facilitated.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, in the cross sectional view, the length of the foamed puncture tube entering the rim from the outer peripheral end surface of the rim is 1 to 8 mm. .

  In the invention of claim 5, if the length is less than 1 mm, the tube cannot be stably supported without wobbling at both ends of the rim opening, and if it exceeds 8 mm, the weight of the tube is reduced and the tube is inserted into the tire. Both of the ease of fitting cannot be realized.

  A sixth aspect of the present invention is a method of fitting the annular foamed no-puncture tube according to any one of claims 1 to 5 into a tire outer cover of a bicycle in use, wherein one part of the foamed no-punk tube is a ring. It is characterized in that it is cut obliquely with respect to the direction and fitted into the tire skin.

  According to the sixth aspect of the present invention, it is possible to fit the tube into the tire skin without removing the tire skin from the vehicle body, and the bicycle user can easily work. In addition, the reason for cutting the tube obliquely with respect to the annular direction (longitudinal direction) of the tube is that the cut surface is dispersed in the annular direction (longitudinal direction) of the tube, making it difficult to understand the cut surface. This is because the elasticity of the vehicle is hardly changed to prevent the ride comfort from being lowered.

  A seventh aspect of the present invention is a core-back injection mold for molding the foamed non-punk tube according to the first aspect, wherein each cavity is molded in a concave ring shape to form both side surfaces in a cross-sectional view of the tube. In order to form an annular fixed mold and a movable mold each provided with a space, an outer peripheral surface portion serving as a grounding surface of the tube, and an inner peripheral surface portion opposed thereto, either the movable mold or the fixed mold On the other hand, it is composed of annular first and second movable insertion pieces provided so as to be able to enter and exit in a state of being urged in the protruding direction by the urging means while being connected to the respective cavity molding spaces, At the time of tightening, the first and second movable insertion pieces are retracted to the maximum with respect to the movable mold or the fixed mold, and the contact surfaces of the fixed mold and the movable mold are brought into close contact with each other. For synthesis of cavity forming space After the raw cavity for raw material injection is formed and the raw material is injected into the original cavity, the movable mold cores back, so that each of the first and second movable insertion pieces protrudes to be a fixed mold or a movable mold The maximum cavity for core back molding is formed by being in close contact with the close contact surface.

  According to the invention of claim 7, the first and second movable insertion pieces are retracted to the maximum with respect to the movable mold or the fixed mold, and the opposed close contact surfaces of the fixed mold and the movable mold are brought into close contact with each other. A raw cavity for injecting a thermoplastic elastomer raw material is formed by synthesizing the cavity mold spaces of a fixed mold and a movable concave ring, and a molten thermoplastic elastomer raw material containing a foaming agent is injected and filled into the original cavity. Thereafter, when the movable mold is moved backward (core back) with respect to the fixed mold, the first and second movable insertion pieces urged in the protruding direction by the urging means are moved back together with the movable mold. Without holding the position, that is, each of the first and second movable insert pieces protrudes relative to the movable type or the fixed type, so that the fixed or movable type contact surface is provided. The maximum cavity is formed by the fixed mold, the movable mold, and the first and second movable insert pieces while remaining in close contact with each other. Due to the presence of increased cavities in the largest cavity relative to the original cavity, the molten thermoplastic elastomer raw material containing the foaming agent is foamed, and an annular tube having a shape corresponding to the largest cavity is formed. The By the first and second movable insert pieces, an outer peripheral surface portion serving as a grounding surface of the tube and an inner peripheral surface portion facing the outer peripheral surface portion are formed.

  Of the molded annular tube, the surface layer portion, which is the entire outer peripheral surface that is in direct contact with each mold, has a lower cooling rate than the other portions, so the foaming ratio is low or not. By being foamed, a skin layer having a higher hardness than other portions is formed. In addition, the annular tube which is a molded product is taken out from the movable mold or the fixed mold by further retracting the movable mold with respect to the state in which the maximum cavity is formed.

  The invention of claim 8 is a core-back injection mold for forming the foamed non-punctured tube according to claim 1, wherein each cavity is formed in a concave ring shape to form both side surfaces in a cross-sectional view of the tube. Connected to each cavity forming space in order to form an annular fixed mold and a movable mold each provided with a space, an outer peripheral surface portion serving as a grounding surface of the tube, and an inner peripheral surface portion facing the outer peripheral surface portion. And each of the first and second movable insertion pieces provided in an annular shape so as to be able to enter and exit while being urged in the protruding direction by the urging means. Each movable insertion piece is divided into two at the most protruding portions of the outer peripheral surface portion and the inner peripheral surface portion, and the first and second movable insertion piece division bodies are provided for the fixed type and the movable type, respectively. At the time of mold clamping, Each of the first and second movable insert piece segments is retracted to the maximum with respect to the movable mold and the fixed mold, and the contact surfaces of the fixed mold and the movable mold are brought into close contact with each other, thereby forming each cavity in a concave ring shape. A raw cavity for raw material injection is formed by synthesizing the space, and after the raw material is injected into the original cavity, the movable mold cores back so that the first and second movable insert piece segments protrude. The maximum cavity for core back molding is formed by bringing the close contact surfaces of the movable insert piece segments into close contact with each other.

  According to invention of Claim 8, the 1st and 2nd movable insertion piece is divided into two by the outermost surface part of the foaming no-punk tube to be shape | molded, and the most projecting part of an inner peripheral surface part, and it is a molded article from a movable mold | type. When removing (removing) the first and second movable insert piece divided bodies, since there is no undercut portion for the molded product, the molded product can be easily removed and the molded product can be removed. At times, the molded product is not damaged by the first and second movable insert piece divisions.

  The invention according to claim 9 is the invention according to claim 8, wherein each of the first and second movable insert piece divisions provided in the fixed mold is attached when the movable mold is further retracted from the core back molding position. The molded product is separated from the fixed mold by protruding by a predetermined length by the biasing means.

  According to the ninth aspect of the present invention, after the core-back injection molding, when the movable mold is further retracted for taking out the molded product, the first and second movable insertion pieces provided on the fixed mold. When the divided body further protrudes by the urging means, the molded product is separated from the fixed mold. As a result, the molded product does not remain in the fixed mold and retreats integrally with the movable mold, so that the molded product can be reliably taken out from the movable mold.

  A tenth aspect of the present invention is a method for injection molding the foamed non-punk tube according to the first aspect using the core back injection mold according to the seventh aspect, wherein each contact surface of the fixed mold and the movable mold. After injecting and filling the raw material of the molten thermoplastic elastomer containing the foaming agent into the original cavity formed by closely adhering the core, the movable mold is core-backed against the fixed mold. Due to the urging force, each of the first and second movable insertion pieces protrudes to the maximum, and each leading end surface is brought into close contact with the contact surface of the fixed type or the movable type, thereby forming the maximum cavity and filling the original cavity. The raw material is foamed, and the inner peripheral surface of the foamed no-puncture tube and the inner peripheral portion facing the grounding portion are formed by the inner peripheral surface of the first movable insertion piece and the outer peripheral surface of the second movable insertion piece, respectively. Be done It is characterized in.

  According to the invention of claim 10, core-back injection molding of an annular foamed no-puncture tube is possible as a whole, which has an atypical shape whose transverse section is deformed with respect to a circle.

The invention of claim 11 is a method of injection-molding the foamed non-punk tube of claim 1 using the core back injection mold of claim 8 or 9, wherein each of the fixed mold and the movable mold The raw cavity formed by adhering the close contact surface is injected and filled with the raw material of the molten thermoplastic elastomer containing the foaming agent, and then the movable mold is core-backed against the fixed mold, thereby energizing By the urging force of the means, the first and second movable insertion piece divisions provided respectively in the fixed mold and the movable mold are projected to the maximum, and each of the divided first and second movable insertion piece divisions is divided. The leading cavities are in close contact with each other to form the largest cavity, and the raw material filled in the original cavity is foamed,
The inner peripheral surface of the first movable insertion piece and the outer peripheral surface of the second movable insertion piece form a part of the grounding portion of the foamed non-puncture tube and an inner peripheral portion facing the grounding portion, respectively. Yes.

  According to the invention of claim 11, as in the invention of claim 10, core-back injection molding of an annular foamed no-punk tube is possible as a whole, which has an atypical shape whose cross section is deformed with respect to a circle. In addition, since the first and second movable insertion pieces are divided into two at the outermost surface portion and the outermost surface portion of the foamed non-puncture tube that is a molded product, the movable movable piece is integrated with the movable mold. It becomes easy to take out the formed product, and at the time of taking out, the molded product is not damaged.

  A twelfth aspect of the present invention is a foamed no-puncture tube formed by the core back injection molding method according to the tenth or eleventh aspect.

  The foamed no-puncture tube according to the invention of claim 12 is opposed to a part of the grounding portion of the foamed no-punk tube and the grounding portion by the first and second movable insertion pieces at the time of the movable core back. By forming the inner peripheral portion, a skin layer that improves the wear resistance of the no-puncture tube is formed on the entire outer peripheral surface of the foaming main portion.

  The foamed non-punctured tube according to the invention of claim 1 is made by foaming a thermoplastic elastomer to which a foaming agent is added by a core back injection molding method, so that the surface layer part of the entire outer peripheral surface is unfoamed or compared with the general part. Thus, a skin layer having a low expansion ratio is formed. The skin layer formed on the surface layer of the tube has higher hardness than other parts and has wear resistance, and the foamed non-punctured tube includes the ground contact part and the inner peripheral surface of the tire skin. The overall strength of the part in contact with the surface is increased, and the wear resistance of the tube is increased, so that the durability as a foamed non-punctured tube is enhanced. By foaming the plastic elastomer, necessary elasticity can be obtained, and at the same time, the weight of the tube can be reduced.

  According to each invention of Claims 7-9, each 1st and 2nd movable insertion piece for shape | molding the outer peripheral surface part used as the earthing | grounding surface of a tube, and the inner peripheral surface part which opposes this is with respect to a movable type | mold. Therefore, it is possible to perform core-back molding of an annular tube having an irregular shape whose transverse section is deformed with respect to a circular shape. In particular, according to the invention of claim 8, it becomes possible to take out the foamed no-puncture tube, which is a molded product, from the movable mold without damaging it. According to the invention of claim 9, the movable mold after core-back injection molding At the time of further retreat, the molded product can be reliably separated from the fixed mold and taken out from the movable mold.

1 is an overall perspective view of a foamed no-puncture tube C according to the present invention. It is an enlarged transverse sectional view similarly. FIG. 2 is a front view in which a part of a tire T in which a foamed non-punctured tube C is fitted in an annular space 22 of a tire outer skin 21 is broken. FIG. 4 is an enlarged sectional view taken along line XX in FIG. 3. Is a view seen from the side of the fixed mold F ₁ core back injection mold A ₁ for molding a foamed no puncture tube C according to the present invention. (A), (b) shows the core back injection mold A ₁ in which the raw cavity K ₀ is injected and filled with a molten thermoplastic elastomer material, and the movable mold F ₂ is retracted after injection and filling. FIG. 6 is an enlarged sectional view taken along line YY in FIG. 5. (C), (d) shows a state in which the thermoplastic elastomer raw material is foamed in the maximum cavity K ₁ in the core back injection mold A ₁ , and the movable mold F ₂ is further retracted after foam molding. FIG. 6 is an enlarged sectional view taken along line YY in FIG. (A), (b) shows a state in which the thermoplastic elastomer raw material is foamed in the core back injection mold A ₂ in a state where the molten thermoplastic elastomer raw material is injected and filled in the original cavity K ₀ and in the maximum cavity K ₁ . It is the YY line expanded sectional view of FIG. (C), in the core-back injection mold A _2, is a line Y-Y enlarged sectional view of FIG. 5 in a state to take out the molded article further retracting the movable mold F ₂ after the foam molding. It is a table | surface which shows the Example of this invention. It is a table | surface which shows the comparative example of this invention.

Hereinafter, the foamed non-punctured tube C according to the present invention is a core back injection mold A ₁ provided with movable insert pieces F ₃ and F ₄ used in the molding method, and an injection molding method using the injection mold A _1. Will be explained.

As shown in FIGS. 1 and 2, the foamed no-puncture tube C according to the present invention is characterized in terms of structure and molding, by using a molten thermoplastic elastomer raw material containing a foaming agent as described in the following core back injection. The surface layer portion of the entire outer peripheral surface of the foamed no-puncture tube C formed by the core back injection molding method occupies most of the remaining portion in that it is molded in an annular shape using the molding die A ₁ (A ₂ ). Compared to the foam main part 1, the foaming ratio is low or it is not foamed, so the skin layer 2 having high hardness is formed, so that it is lightweight, riding comfort and durability due to appropriate rebound resilience. A no puncture tube satisfying the above is obtained. That is, the foamed non-punctured tube C according to the present invention is formed by foaming a thermoplastic elastomer, and the inside excluding the surface layer portion that occupies most of the foamed weight is reduced as a whole, and an appropriate and indispensable mode for the tube. Elasticity can be ensured, and only the surface layer portion is formed by the skin layer 2 having higher hardness and excellent wear resistance than the other portions, and therefore, due to contact with the inner peripheral surface of the tire outer skin 21 Abrasion resistance is enhanced, and in particular, a portion in contact with the portion near the rim R of the tire T in the foamed no-puncture tube C is subjected to a large lateral pressure during use, but due to the presence of the skin layer 2 in the surface layer portion, Abrasion resistance against side pressure is enhanced, and it becomes difficult to be damaged even after long-term use.

  The skin layer 2 preferably has a thickness of 0.5 to 4.0 mm. When the thickness of the skin layer 2 is less than 0.5 mm, the strength is small and the durability as the tube C is low, and when it exceeds 4.0 mm, the deformability is poor and the gap between the rim R and the tube C is reduced. The wear of the tire outer skin 21 in the portion sandwiched between the two increases.

  As shown in FIG. 3 and FIG. 4, the shape of the foamed non-punctured tube C according to the present invention is opposed to the grounding portion of the tube C when fitted to the rim R and fitted to the tire outer skin 21. That is, the inner peripheral portion 12 of the annular tube C does not reach the bottom of the rim R, and the tube C is supported by the opposite inner end 32 of the opening of the rim R with respect to the rim R. It is a point.

  As shown in FIGS. 1 and 2, the tube C has an annular shape as a whole, and has a substantially arc-shaped outer peripheral grounding portion 11, an inner peripheral portion 12 facing the grounding portion 11, It consists of a total of four parts, each side face part 13 on both sides connecting between the grounding part 11 and the inner peripheral part 12. Almost half of the inner peripheral portion 12 of each side surface portion 13 is an easy wear portion 13a that is most easily worn by sliding contact with the inner peripheral surface of the tire outer skin 21 with a large force during driving of a bicycle or the like. However, since all the surface layer portions of the foam main body portion 1 are covered with the skin layer 2 having a higher hardness than the foam main body portion 1, the structure has an improved wear resistance. In the present embodiment, the inner peripheral surface of the tube C has a shape in which a flat plate is bent in an annular shape, and has a shape that appears substantially on a straight line in a cross-sectional view.

2 to 4, the relationship between the width (W) of the tube C and the width (B) of the annular space 22 of the tire outer skin 21, and the height (H) of the tube C and the inner surface apex of the tire outer skin 21 rim. The relationship between the distance R to the outer end surface (D) is that the tube C is slightly compressed and deformed, and is fitted in close contact with the inner peripheral surface of the annular space 22 of the tire outer skin 21. Is considered to be supported by the opposed inner end 32 of the rim opening 31 without being brought into contact with the bottom of the rim R as follows. The unit is (mm).
B ≦ W ≦ (B + 2)
(D + 1) ≦ H ≦ (D + 8)

  Further, as shown in FIGS. 3 and 4, the tube C is fitted in the tire outer skin 21 </ b> K annular space 22, and the inner peripheral surface of the tube C is not in contact with the bottom surface of the rim R. The portion of the side surface portion 13 close to the inner peripheral portion 12 is supported while being hooked on the opposed inner end portion 32 of the rim opening 31 of the rim R. In such a support structure, in order to stably support the tube C with respect to the rim R, the length (E of the inner peripheral portion 12 of the tube C entering the inside of the rim R from the outer peripheral end of the rim R (E ) Must be 1-8 mm. If the length (E) is less than 1 mm, the tube C cannot be stably supported without wobbling at the opposed inner end 32 of the rim opening 31, and if it exceeds 8 mm, the inner diameter of the tube C becomes too small. Both the weight reduction of the tube C and the ease of fitting the tube C into the tire outer skin 21 beyond the rim end cannot be realized.

  By supporting the tube C with the opposed inner end portion 32 of the rim opening 31, the inner diameter of the tube C is increased, so that the volume of the tube C is reduced and the tube C is reduced in weight. Further, the skin layer 2 is formed on the entire outer peripheral surface of the tube C, and the grounding portion of the tube C is formed in a substantially arc shape that follows the inner peripheral surface of the grounding portion of the tire outer skin 21. Since the tube C is easily integrated with the outer skin 21, even if the tube C is supported by the opposed inner end 32 of the rim opening 31 without contacting the bottom of the rim R, the tube C is Can support without wobbling. Further, since the inner diameter of the tube C is increased, the tube C can be easily climbed over when the tube C is fitted into the rim R, and the fitting operation of the tube C into the rim R is facilitated.

Next, referring to FIG. 5, FIG. 6-A and FIG. 6-B, the core back injection mold A ₁ provided with the first and second movable insert pieces F ₃ and F ₄ is used. A method of forming the tube C will be described. The core back injection mold A ₁ includes an annular fixed mold F ₁ , a similar annular movable mold F ₂ that moves forward and backward with respect to the fixed mold F ₁ to form the original cavity K ₀ by close contact, The movable mold F ₂ includes first and second movable insertion pieces F ₃ and F ₄ which are mounted on the movable mold F ₂ and are urged in the protruding direction by the compression spring 40 with respect to the movable mold F ₂ . Each of the first and second movable insert pieces F ₃ and F ₄ has an annular shape with different sizes, and each of the movable insert pieces for forming the sides of the grounding portion 11 and the inner peripheral portion 12 of the tube C, respectively. In the state where the movable mold F ₂ is retracted to the core back position as shown in FIG. 6A (b), the concave mold cavity 41 of the fixed mold F ₁ and the movable mold F ₂ are formed. A maximum cavity K ₁ is formed by forming a hollow ring thick disk-shaped intermediate cavity forming space 43 that is proportional to the retracted length of the movable mold F _{2 to} the core back position between 42. The first and second movable insertion pieces F ₃ and F ₄ are inserted into the respective annular grooves 46 and 47 provided to open in the contact surface 45 of the movable mold F ₂ so as to be able to enter and exit. In FIG. 6A, reference numeral 44 denotes a contact surface of the fixed mold F _{1 that} is in close contact with the contact surface 45 of the movable mold F ₂ .

The inner peripheral surface of the first movable insertion piece F ₃ forms a concave ring continuous with the concave annular cavity forming space 41 of the movable mold F ₂ , and the outer peripheral surface of the second movable insertion piece F ₄ is a cylindrical body. It has the same shape as the outer peripheral surface. The first and second movable insert pieces F ₃ and F ₄ are attached to the movable body F ₂ by urging mechanisms Pa and Pb having the same structure provided at a plurality of locations along the circumferential direction of the movable mold F _2. It is urged in the direction protruding. That is, the urging mechanisms Pa and Pb include a plurality of rod bodies 48a and 48b that are integrally provided on the back side of the first and second movable insertion pieces F ₃ and F ₄ , and the annular grooves 46, communication with provided rod member insertion holes 49a to 47, the middle of the stepped portion 51a of 49b, 51b and compression which is elastically interposed between the rear surface of the respective first and second movable insertion piece F _3, F ₄ The first and second movable insertion pieces F ₃ and F ₄ are biased in the protruding direction by the restoring force (biasing force) of the compression springs 52a and 52b. Stopper heads 53a and 53b are provided at the rear ends of the rod bodies 48a and 48b. The stopper heads 53a and 53b come into contact with the stepped parts 51a and 51b, so that The maximum protruding length of each movable insertion piece F ₃ , F ₄ is restricted. 6A and 6B, reference numeral 54 denotes a sprue that injects a molten thermoplastic elastomer melt raw material M containing a foaming agent.

  For forming the foamed no-puncture tube C according to the present invention, a thermoplastic raw material containing a foaming agent is used. As the thermoplastic elastomer, one that is ester-based, urethane-based, or styrene-based, or a mixture of a plurality of them in a predetermined ratio is used.

In order to mold the foamed no-puncture tube C according to the present invention using the core back injection mold A ₁ described above, as shown in FIG. 6A (a), the contact surface 44 of the fixed mold F ₁ is fixed. When the close contact surface 45 of the movable mold F ₂ is brought into close contact with the mold, the first and second movable insertion pieces F ₃ and F ₄ resist the restoring force (biasing force) of the compression springs 52a and 52b. The front end surfaces of the first and second movable insertion pieces F ₃ and F ₄ are moved backward with respect to the movable mold F ₂ , and are brought into close contact with the contact surface 44 of the fixed mold F ₁ , thereby forming a hollow annular shape. The original cavity K ₀ is formed. After the molten raw material M of the molten thermoplastic elastomer containing the foaming agent is injected and filled into the original cavity K ₀ from the plurality of sprues 54 provided in the fixed mold F ₁ , FIG. As shown, when the movable mold F ₂ is core-backed (retreated) by a set amount, the front end surfaces of the first and second movable insert pieces F ₃ and F ₄ are restored by the restoring force of the compression springs 52a and 52b. Is in a state of being in close contact with the contact surface 44 of the fixed mold F ₁ , so that the maximum cavity K having a large capacity by the intermediate cavity molding space 43 relative to the original cavity K ₀ by a total of four molds F _{1 to} F _{4. 1} is formed. That is, a portion indicated by a void in the maximum cavity K ₁ in FIG. 6A (b) becomes an increased cavity increased with respect to the original cavity K ₀ , and the foaming of the molten raw material M of the thermoplastic elastomer can be performed. Space.

Since the maximum cavity K ₁ is formed by the core back of the movable mold F ₂ , the molten raw material M filled in the original cavity K ₀ is gradually foamed and its volume is increased, so that the volume of the maximum cavity K ₁ is increased. When the whole is filled and left as it is for a predetermined time, as shown in FIG. 6B (c), the entire surface layer portion of the molded product that is in direct contact with the molds F _{1 to} F ₄ is left as the rest. Since the cooling rate is faster than that of the foam main body 1 occupying the majority, the foaming is cured with insufficient foaming or unfoamed. As a result, the skin layer 2 having a higher hardness than the foam main body 1 is formed on all surface layer portions of the molded foam puncture tube C. 3 and 4 including FIG. 6B, the skin layer 2 is illustrated so as to be clearly identifiable with respect to the foam main body 1, but actually, the foam main body 1 The boundary between the skin layer 2 and the skin layer 2 is in a state where the boundary cannot be recognized as the foaming ratio of the molten raw material M gradually changes.

Thus, according to the core back injection mold and the injection molding method according to the present invention, the shape of each side portion of the foamed no-puncture tube C is determined by the fixed mold F ₁ and the movable mold F ₂ , and the first and By using the second movable insertion pieces F ₃ and F ₄ , it becomes possible to determine the shapes of the ground contact portion 11 and the inner peripheral portion 12 of the foamed no-puncture tube C, and the first and second movable insertion pieces F. ₃ and F ₄ are featured.

After the foaming of the molten raw material M is completed and the molded product is cooled to a certain temperature, the movable die F ₂ is further retracted as shown in FIG. The movable insert pieces F ₃ and F ₄ are separated from the contact surface 44 of the fixed mold F ₁ to expose a part of the molded product. In this state, a plurality of eject pins provided on the movable mold F ₂ are exposed. The molded product is taken out from the movable mold F ₂ by the protrusion (not shown).

In the core back injection mold A ₁ of the above embodiment, the first and second movable insert pieces F ₃ and F ₄ are provided in the movable mold F ₂ , but are provided in the fixed mold F _1. Is also possible.

Next, with reference to FIG. 7-A and FIG. 7-B, a method for forming a foamed non-punctured tube C ′ using another core back injection mold A ₂ will be described. The core back injection mold A ₂ has an outer peripheral portion that serves as a ground contact portion of the foamed non-punctured tube C ′, with respect to the core back injection mold A ₁ , the first and second movable insert pieces F ₃ and F _4. The first and second movable insert piece division bodies F ₃₁ and F ₄₁ are divided into two at the most projecting portion of the inner peripheral portion, and compression springs 52a and 52b are respectively formed on the movable type F ₁ and the fixed type F _2. It is the structure incorporated in the state urged | biased by protrusion direction. Further, as shown in FIG. 7A (b), in the state where the movable mold F ₂ is core-backed, each of the first and second movable insert piece divisions F ₃₁ and F ₄₁ on the movable mold F ₂ side. The stopper heads 53a and 53b of the rod bodies 48a and 48b connected to the rod bodies 48a and 51b have a slight gap in the step portions 51a and 51b of the rod body insertion holes 49a and 49b, but are in a state of just before contact. On the other hand, on the fixed mold F ₁ side, the stopper heads 53a, 53b of the rod bodies 48a, 48b have predetermined gaps 55a, 55b between the step portions 51a, 51b. Note that the inner peripheral portion of the foamed non-punctured tube C ′ slightly protrudes toward the center side (inward).

Therefore, as shown in FIG. 7A (a), the original cavity K ₀ formed by bringing the contact surfaces 44 and 45 of the fixed mold F ₁ and the movable mold F ₂ into contact with each other contains a foaming agent. After injecting the molten thermoplastic elastomer raw material M, the movable mold F ₂ is core-backed (retreated) to form the maximum cavity K ₁ as shown in FIG. 7A (b). The raw material injected into the original cavity K ₀ is foamed to form a foamed no-puncture tube C ′, which is a molded product. In this state, as described above, the stopper heads 53a, 53b of the rod bodies 48a, 48b on the movable F ₂ side have a slight gap in the step portions 51a, 51b of the rod body insertion holes 49a, 49b. whereas in the state of abutting the verge Te, rod body 48a of the fixed mold F _1, a stopper head 53a of 48b, 53b is the stepped portion 51a, a predetermined gap 55a between 51b, and 55b Have.

After the injection molded product is cooled to a certain temperature, as shown in FIG. 7B (c), when the movable mold F ₂ is further retracted, the stoppers of the rod bodies 48a and 48b are fixed on the fixed side F ₁ side. Until the heads 53a and 53b come into contact with the stepped portions 51a and 51b, the first and second movable insertion piece divisions F ₃₁ and F ₄₁ on the fixed side F ₁ are separated from the fixed mold F ₁ by a gap 55a, By projecting by the length of 55b, the foamed no-puncture tube C ′, which is an injection molded product, is forcibly separated from the fixed mold F ₁ and retracted integrally with the movable mold F ₂ to produce an injection molded product. Can be taken out.

In the state where the injection molded product can be taken out, each of the first and second movable insert piece divisions F ₃₁ and F ₄₁ does not have an undercut portion with respect to the injection molded product. _It is easy to take out the injection-molded product from _2, and the injection-molded product is not damaged by the first and second movable insert piece divisions F ₃₁ and F ₄₁ at the time of taking out.

Here, the expansion ratio of the thermoplastic elastomer forming the molded no-punk tube C is a value obtained by dividing the cross-sectional area of the maximum cavity K _{1 by} the cross-sectional area of the original cavity K _0. The value that can perform the function is 1.5 to 3.5, preferably 2.0 to 3.0. If the foaming ratio of the thermoplastic elastomer is less than 1.5, foaming is insufficient and the tube becomes heavy, which is not practical. If the foaming ratio exceeds 3.5, the porosity of the foam increases. After that, the durability as a tube is reduced due to a decrease in strength as a tube.

  The skin layer 2 has a thickness of 0.5 to 4.0 mm, preferably 1.5 to 3.0 mm. When the thickness of the skin layer 2 is less than 0.5 mm, the strength is low and the durability as a tube is low. When the thickness exceeds 4.0 mm, the deformability is poor and the skin layer 2 is sandwiched between the rim and the tube. The wear of the outer tire cover increases.

  The foamed non-punctured tube C according to the present invention is formed by foaming a thermoplastic elastomer to which a foaming agent is added by a core back injection molding method. Thus, the skin layer 2 having a low expansion ratio or close to non-foaming is formed. The skin layer 2 formed on the surface layer of the foamed non-punctured tube C has higher hardness than the foamed main portion 1 and has wear resistance. The tube C includes a grounding portion, and includes a tire outer skin. The strength of the entire surface of the portion contacting the inner peripheral surface of 21 is increased, and the wear resistance as the tube C is enhanced, so that the durability as the foamed no-puncture tube C is enhanced. On the other hand, the foaming main body 1 occupying most of the remaining portion excluding the skin layer 2 of the surface layer is provided with elasticity necessary for securing riding comfort of a bicycle or the like by foaming the thermoplastic elastomer. At the same time, the weight of the tube C can be greatly reduced.

  Further, the foamed non-punctured tube C is supported on the rim R by contacting the inner peripheral side of the tube C from the outer peripheral end surface of the rim R by a predetermined length without bringing the inner peripheral side of the tube C into contact with the bottom of the rim R. The structure is such that the inside of the rim opening 31 enters the inside and is supported by the opposed inner end 32 of the rim opening 31 of the rim R. Therefore, the inner diameter of the tube C can be increased and the fitting to the rim R is facilitated. In addition, since the cross-sectional area of the tube C is reduced, the weight can be reduced.

  In the case of a new tire T, the tube C can be fitted into the rim R of the single tire T while remaining in an annular shape, but an air tube or the like can be inserted into the rim R of the tire T such as a bicycle in use. 1, as shown by the cut surface 3 in FIG. 1, one part of the annular tube C is cut obliquely and fitted into the rim R and used as it is, or After the fitting, the cut surface of the tube C can be integrated by bonding with an adhesive. Thus, the annular tube C can be fitted without removing the tire from the main body, and even a general bicycle user can easily fit the tube into the tire. In addition, by cutting the tube obliquely with respect to the annular direction (longitudinal direction) of the tube, the cut surface is dispersed in the annular direction (longitudinal direction) of the tube, making it difficult to understand the cut surface. Further, since the elasticity of the cut portion hardly changes, there is no decrease in riding comfort.

  Examples 1 to 4 of the foamed no-puncture tube according to the present invention used for a bicycle tire having a size of (27 × 1 3/8) are shown in FIG. In Examples 1 and 2, as the thermoplastic elastomer, ester-based ones are used, and in Example 3, the weight ratio of urethane-based and ester-based (1/7) is used. Then, the weight ratio of styrene type and ester type is (1/9), and as a blowing agent to be added to the thermoplastic elastomer, a masterbatch chemical blowing agent is 6 to 8 parts based on the whole. The foamed no-puncture tubes of Examples 1 to 4 were molded by the core back injection molding method.

  From Example 1 to Example 4, the foaming ratio of the raw material is sequentially increased, and the weight of the tube is reduced in inverse proportion to this, and the weight of the tube of Example 4 is reduced to 390 g. . On the other hand, there is no problem with the fitting property of the tube to the tire because the inner diameter is large, both of which are smooth when mounted on a bicycle tire, and vibration during running No problem with respect to the fact that none of them affect the ride comfort, and furthermore, the tube has passed the durability of JISK6302.

C, C ': Foamed no-punk tube
A ₁ , A ₂ : Core back injection mold
F ₁ : Fixed type
F ₂ : Movable type
F ₃ : First movable insertion piece
F ₃₁ : 1st movable insertion piece division body
F ₄ : Second movable insertion piece
F ₄₁ : Second movable insertion piece division body
K ₀ : Original cavity
K ₁ : Maximum cavity
Pa, Pb: Energizing mechanism
R: Rim
T: Tire
1: Foam main part
2: Skin layer
44: Fixed-type contact surface
45: Movable contact surface 52a, 52b: Compression spring

Claims (12)

Using a core back injection mold in which an annular molding space having a cross section corresponding to the cross section shape of the tube is formed between the movable mold and the fixed mold at the time of the core back,
After filling the original cavity formed by the stationary mold with the movable mold when the movable mold is advanced, the thermoplastic elastomer raw material containing a foaming agent is filled, and then the movable mold is cored back to increase the heat in the maximum cavity. Molded by core back injection molding method to foam plastic elastomer raw material,
The foaming ratio is lower than that of the foaming main part, or the foaming main part is unfoamed, and the wear resistance is enhanced by the skin layer formed on the entire outer peripheral surface. A foamed no-puncture tube characterized by that.   The foamed puncture tube according to claim 1, wherein the skin layer has a thickness of 0.5 to 4.0 mm.   The expansion ratio of the thermoplastic elastomer is 1.5 to 3.5, and the foamed puncture tube according to claim 1 or 2.   2. The foamed non-punctured tube is inserted into a predetermined length from an outer peripheral end surface of a tire rim in a state of being fitted into a tire outer skin, and is supported at an opposed inner end portion of a rim opening. The foamed puncture tube according to any one of 3 above.   5. The foamed no-puncture tube according to claim 4, wherein, in a cross-sectional view, the length of the foamed no-puncture tube entering the rim from the outer peripheral end surface of the rim is 1 to 8 mm. A method of fitting the annular foamed no-puncture tube according to any one of claims 1 to 5 into a tire outer cover of a bicycle in use,
A method for fitting a foamed no-puncture tube, wherein one part of the foamed no-puncture tube is cut obliquely with respect to the annular direction and fitted into the tire skin. A core back injection mold for molding the foamed puncture tube according to claim 1,
A ring-shaped fixed mold and a movable mold each provided with a concave annular cavity forming space for forming both side surfaces in a cross-sectional view of the tube;
In order to mold the outer peripheral surface portion that becomes the grounding surface of the tube and the inner peripheral surface portion that opposes the outer peripheral surface portion, either one of the movable mold or the fixed mold is connected to each cavity molding space, and the biasing means Each of the annular first and second movable insertion pieces provided so as to be able to enter and exit in a state of being biased in the protruding direction by
Consisting of
At the time of mold clamping, the first and second movable insertion pieces are retracted to the maximum with respect to the movable mold or the fixed mold, and the contact surfaces of the fixed mold and the movable mold are brought into close contact with each other. By combining each cavity molding space, a raw cavity for raw material injection is formed,
After the raw material is injected into the original cavity, the movable mold cores back, so that each of the first and second movable inserts protrudes and comes into close contact with the contact surface of the fixed mold or the movable mold. A core back injection mold for a foamed non-punk tube, characterized in that a maximum cavity for molding is formed. A core back injection mold for molding the foamed puncture tube according to claim 1,
A ring-shaped fixed mold and a movable mold each provided with a concave annular cavity forming space for forming both side surfaces in a cross-sectional view of the tube;
In order to mold the outer peripheral surface portion that becomes the grounding surface of the tube and the inner peripheral surface portion that opposes the outer peripheral surface portion, the tube is attached to the fixed mold and the movable mold in a protruding direction by a biasing means in a state of being connected to the cavity forming spaces. Each of the annular first and second movable insertion pieces provided so as to be able to enter and exit in a state of being urged;
Consisting of
Each of the first and second movable insert pieces is divided into two at the most projecting portions of the outer peripheral surface portion and the inner peripheral surface portion, and each of the first and second movable insert piece divisions is fixed and movable. Provided for the mold,
At the time of mold clamping, the first and second movable insertion piece segments are retracted to the maximum with respect to the movable mold and the fixed mold, and the contact surfaces of the fixed mold and the movable mold are brought into close contact with each other. A raw cavity for raw material injection is formed by synthesizing each annular cavity forming space,
After the raw material is injected into the original cavity, the movable mold cores back so that each of the first and second movable insert piece segments protrudes, and the tip contact surfaces of the movable insert piece segments are in close contact with each other. By doing so, a core back injection mold of a foamed non-puncture tube, characterized in that a maximum cavity for core back molding is formed.   Each of the first and second movable insertion piece segments provided on the fixed mold protrudes by a predetermined length by the urging means when the movable mold further moves backward from the core back molding position, The core back injection mold for a foamed no-puncture tube according to claim 8, wherein the molded article is separated. A method for injection-molding the foamed non-punctured tube according to claim 1 using the core-back injection mold according to claim 7,
After injecting and filling a raw material of a molten thermoplastic elastomer containing a foaming agent into the original cavity formed by bringing the fixed surfaces of the fixed mold and the movable mold into close contact with each other, the movable mold is attached to the fixed mold. By making the core back, the first and second movable insertion pieces are projected to the maximum by the urging force of the urging means, and the leading end surfaces are in close contact with the fixed type or movable type close contact surface, thereby maximizing the cavity. Is formed, the raw material filled in the original cavity is foamed,
The inner peripheral surface of the first movable insertion piece and the outer peripheral surface of the second movable insertion piece form a part of the grounding portion of the foamed non-puncture tube and an inner peripheral portion facing the grounding portion, respectively. A core back injection molding method for foaming no-punk tube. A method for injection-molding the foamed non-punctured tube according to claim 1 using the core-back injection mold according to claim 8 or 9,
After injecting and filling a raw material of a molten thermoplastic elastomer containing a foaming agent into the original cavity formed by bringing the fixed surfaces of the fixed mold and the movable mold into close contact with each other, the movable mold is attached to the fixed mold. By making the core back, the first and second movable insert piece divided bodies provided in the fixed mold and the movable mold are projected to the maximum by the urging force of the urging means, and the divided first and second halves are divided. The maximum cavity is formed by the respective tip surfaces of the movable insert piece divisions in close contact with each other, the raw material filled in the original cavity is foamed,
The inner peripheral surface of the first movable insertion piece and the outer peripheral surface of the second movable insertion piece form a part of the grounding portion of the foamed non-puncture tube and an inner peripheral portion facing the grounding portion, respectively. A core back injection molding method for foaming no-punk tube.   A foamed non-punctured tube formed by the core back injection molding method according to claim 10 or 11.

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