JPH029930B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a holder for a green tube molding machine, and more particularly, to a holder for a green tube molding machine, in particular, a molding method in which both ends of an intermediate member made by cutting an unvulcanized rubber material extruded into a hollow cylindrical shape into a predetermined length are joined in an endless shape. In the aircraft holder, by forming an inclined surface on the front surface of the back plate of the holder and attaching the elastic member thereto, the elastic member can be easily deformed when the holders are butted together. In general, unvulcanized tire tubes (green tubes) are made by extruding unvulcanized rubber material into a hollow cylindrical shape with a uniform thickness, cooling it and cutting it into a predetermined length. A member is made, a valve is attached to this intermediate member, and both ends are joined to form an endless annular body. Conventionally, a holder as shown in Figure 1 has been used as a molding machine for this green tube. ing. This figure shows one of a pair of left and right upper mold holders 10 and lower mold holders 20 used when joining both ends of an intermediate member by the butt joint method. 12 and 22 are fixed to each other, and elastic members 14 and 24 made of rubber or the like are bonded to the front surfaces of the back plates 12 and 22. When joining the intermediate member, both ends of the intermediate member (not shown) are placed between the holding members 26 of the lower mold holder 20 spaced apart on both the left and right sides, so that both ends of the intermediate member (not shown) are approximately lower than the front end surface of the elastic member 24 of the lower mold holder 20. It is attached with the intermediate member pulled out by 1 cm, and then the upper die holder 10 is lowered and both ends of the intermediate member are clamped and fixed between it and the lower die holder 20, and both ends of the intermediate member are held together with a knife (not shown). Create a new joining end face by cutting each part so that about 1 mm remains, then butt the holders from both the left and right sides, and press the joining end faces to join them endlessly. At the joint of the intermediate member, when the holders are butted together, the elastic members 14 and 24 are compressed, and the elastic member 14 of the upper die holder 10 is bent upward, and the elastic member 24 of the lower die holder 20 is bent downward. Therefore, each of the joints has an outwardly protruding shape, but the thickness of this joint differs depending on the degree of deformation of the elastic members 14 and 24. By the way, in the conventional holder, as shown in FIG. 2a, since the elastic member 14 is bonded to the front surface of the back plate 12 as a vertical surface, the degree of deformation of the elastic member 14 is small when the holders are butted against each other. The thickness of the joint portion of the intermediate member is relatively thin. For this reason, the tube 40 obtained by vulcanizing a green tube molded with a conventional holder has a joint portion 42 with a cross-sectional shape of a second shape.
As shown in FIG. When such a tube is attached to a tire and used, stress is concentrated on the joint surface, resulting in an open splice, which tends to cause a puncture accident. This invention was made to eliminate the above-mentioned drawbacks, and an object of the invention is to provide a holder for a green tube molding machine that can increase the degree of deformation when the elastic members are butted together. Another object of the present invention is to provide a holder for a green tube molding machine that can prevent open splices from occurring at the joints of tire tubes. That is, the present invention provides an intermediate member 3 made by cutting a hollow flat body made of an unvulcanized rubber material of uniform thickness into a predetermined length, as shown in the illustrated embodiment.
0 is clamped between a pair of left and right upper mold holders 10 and lower mold holders 20 each having back plates 12, 22 with elastic members 14, 24 provided on the front end surfaces, and the holders are butted against each other. In the holder for a green tube molding machine, the upper die holder 10 and the lower die holder 2 are joined together.
The front surfaces of the back plates 12 and 22 are formed into inclined surfaces 15 and 25 having an angle of 11 to 20 degrees with respect to the direction in which the holders butt each other. This invention relates to a holder for a green tube molding machine, characterized in that it is equipped with a holder for a green tube molding machine. Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a sectional view showing an embodiment of the invention. On the front surface of the back plate 14 fixed to the abutment 11 of the upper mold holder 10, an inclined surface 15 that is inclined with respect to the butting direction (front) of the holders is formed, and the back surface of the elastic member 14 is attached to this inclined surface 15. It is glued in close contact. Similarly, the back plate 22 of the lower die holder 20 also forms an inclined surface 25 with respect to the direction in which the holders are brought together, and the elastic member 24
is attached. Reference numeral 30 is an intermediate member. FIG. 4a shows the back plate 12 of the upper die holder 10.
Although the inclination angle θ of the inclined surface 15 is shown in the figure, it is desirable that the inclination angle θ is 11 degrees or more and 20 degrees or less. As mentioned above, the back plate 1 of this invention
Since 2 and 22 have inclined surfaces 15 and 25 on their front surfaces, the degree of deformation of the elastic members 14 and 24 increases when the holders are butted together, and the intermediate member 3
The thickness of the 0 joint can be increased. The reason why the inclination angle of the back plates 12 and 22 is set to 11 degrees or more and 20 degrees or less is because if the inclination angle is too small, such as less than 11 degrees, the elastic members 14 and 22
This is because if the degree of deformation is not sufficient, and if the inclination angle is too large, exceeding 20 degrees, the formability during joining will be extremely poor, causing buckling. Generally, the bonding force at the joint of a tire tube must be 60% or more of the tensile strength of the parts other than the joint, and most preferably 80% or more. To achieve this, the cross-sectional area of the joint must be at least 150% of the cross-sectional area of the parts other than the joint, but if the ratio of this cross-sectional area is over 250%, buckling will occur during vulcanization. Since this causes product failure, it actually becomes difficult to manufacture the product. FIG. 4b shows the cross-sectional shape of the joint 42 of the tube 40 manufactured by vulcanizing the green tube molded by the holder of the present invention, and the joint 42 is similar to that shown in FIG. 2b. It is raised higher than the conventional tube shown, and there is a part at the hem of the joint 42 that is slightly thinner than the part 44 other than the joint, but the thickness Hb of the joint 42 is equal to the thickness of the part 44 other than the joint. It is necessary and sufficient thickness compared to SaHa,
The cross-sectional area of the joint is the cross-sectional area of the part other than the joint.
It can be 150% or more and less than 250%. FIG. 5 shows another embodiment of the present invention, and FIG. As shown in the example, the angle α between the inclined surface 15 and the bottom surface 16 of the back plate 12 is an acute angle, and this prevents the elastic member 14 from peeling off and the intermediate member from being damaged. . Figure b shows a structure in which a stepped surface 17 is provided between the bottom surface 16 and the inclined surface 15 of the back plate 12 to particularly increase the effect of preventing the elastic member 14 from peeling off.
Figure 2d shows a case where the bottom of the sloped surface 15 of the back plate 12 is chamfered so as to be sloped in the opposite direction to the bottom surface 16. This is particularly effective in preventing damage to members. Next, Table 1 shows the results of a bending resistance test on the joints of a tire tube manufactured by vulcanizing a green tube molded using the holder of the present invention and a conventional tire tube. show. The test method used was a bending test specified in JIS6301 Vulcanized Rubber Physical Test Method, and the test piece was punched out with a JIS No. 2 dumbbell centered around the joint. The size of the test tube is a 175R14 tube for passenger car radial tires. The back plate of the holder of this invention is the fifth
The shape was as shown in Figure c, the inclination angle θ was 20 degrees, and the chamfer angle was 45 degrees.

[Table] As is clear from the results in Table 1, the tube according to the present invention has a bonding strength that is more than twice that of the conventional tube. As explained above, the present invention has a structure in which the front surface of the back plate of a holder for a green tube molding machine is formed into an inclined surface having an angle of 11 to 20 degrees with respect to the direction in which the holders butt together, and an elastic member is attached. There is. Therefore, according to the present invention, the thickness of the joint can be made thicker than before without increasing the degree of deformation of the elastic member when the holders are brought together and hindering the moldability of the intermediate member. When vulcanized as a tire tube, the cross-sectional area of the joint of the tire tube will be within the specified range compared to the cross-sectional area of the parts other than the joint, and when used in a pneumatic tire, the joint will be vulcanized. The applied stress is dispersed, the number of open splices at the joint surface is reduced, and it is possible to prevent puncture accidents from occurring.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a holder for a green tube molding machine, Fig. 2a is a cross-sectional view showing the back plate and elastic member of a conventional holder, Fig. 2b
3 is a sectional view showing a joint part of a conventional tire tube, and FIG. 3 is a sectional view showing an embodiment of the present invention.
FIG. 4a is a cross-sectional view showing the back plate and elastic member of FIG. 3, FIG. 4b is a cross-sectional view showing the joint part of the tire tube according to the present invention, and FIG.
1 to d are cross-sectional views showing other embodiments of the present invention, respectively. In the figure, 10 is an upper mold holder, 20 is a lower mold holder, 12 and 22 are back plates, 14 and 24 are elastic members, 15 and 25 are inclined surfaces of the back plate, and 30 is an intermediate member.

Claims (1)

[Claims] 1. Both ends of an intermediate member made by cutting a hollow flat body made of an unvulcanized rubber material of uniform thickness into a predetermined length are attached to a pair of left and right parts each having a back plate with an elastic member provided on the front end surface. In a holder for a green tube molding machine which is sandwiched between an upper mold holder and a lower mold holder and the holders are joined by butting each other, the front surface of the back plate of the upper mold holder and the lower mold holder is A holder for a green tube molding machine, characterized in that each of the holders is formed with an inclined surface having an angle of 11 to 20 degrees with respect to the direction in which the holders meet, and an elastic member is attached to each of the inclined surfaces.