JPH11286031A - Method for rubber molding tire valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a deterioration of operability caused by a residue of a cured rubber at a gate port of a mold. SOLUTION: A rubber curing of a gate part of a mold is eliminated and yield of a rubber material is improved by the method for rubber molding a tire valve comprising the steps of introducing a valve stem, injection casting a rubber material in a cavity sealed by a casting mold at an unvulcanizing temperature and a lower mold introduced with the stem, removing the casting mold, clamping an upper mold to fill the rubber material and vulcanizing the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rubber molding of automobile tire valves.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view of an automobile tire valve product. The tire valve is provided with a rubber portion on the valve stem 1 to maintain airtightness between the tire valve and the rim. Further, the valve stem 1 is a cylindrical pipe, has a hole for supplying or discharging air into the tire, and a valve core 2 which is a check valve for controlling compressed air is screwed into the valve core 2 so that foreign matter is not contained in the valve core 2. The valve cap 3 is assembled so as not to enter. The process of injection molding rubber on the valve stem 1 is generally a first stage injection process,
Fill rubber at high pressure to about 95% of mold volume. In the second stage dwelling step, the remaining rubber is filled at low pressure.

[0003] In the above-mentioned injection process, rubber is blown at once.
The reason for filling about 95% instead of filling at 00% is as follows. First, when rubber is filled at a stretch of 100%, the pressure inside the mold exceeds the mold clamping force and the mold may be opened, which causes a problem of defective burr leakage. Secondly, if the amount of rubber to be filled in the injection step is reduced so as not to reach 95%, the vulcanization reaction of the rubber proceeds during the filling of the rubber at a low pressure in the subsequent pressure-holding step, and the rubber is reduced. To cure.

When the rubber is cured, it is difficult to fill the rubber with 100%. In the injection step, as much rubber as possible is filled at a high pressure, and the remainder is filled at a low pressure in a pressure-holding step.

[Problems to be solved by the invention]

[0005] In the above method, the filled rubber material is in a vulcanized state because the rubber pressure inlet is at a high temperature and cannot be reused. Poor use efficiency. Further, the supply of the rubber material and the discharge of the surplus vulcanized rubber require an operator and an automatic facility, and the working efficiency is poor.

Further, since the heat of the cavity is transmitted to the runner and the gate and the temperature is high, the rubber material filled in the runner and the gate is in a vulcanized state. There are various problems in the conventional technology, such as the necessity of equipment and poor work efficiency, and the production cost is high and the surplus vulcanized rubber becomes an industrial waste. In addition, in order to fill the rubber material with details, it is necessary to maintain the injection pressure, and the injection molding cycle becomes longer.

[0007]

SUMMARY OF THE INVENTION The present invention eliminates the excessive vulcanized rubber of the conventional runner and gate, eliminates the holding time of the injection pressure, and maintains the cavity volume at a constant pressure in the metering / injection process. Injecting as much as possible into the inside, and by completing the injection by changing the speed of the screw, higher injection accuracy than the conventional metering / injection method is obtained,
An object of the present invention is to provide a method for manufacturing a rubber portion of a tire valve, which has a low manufacturing cost.

[0008] That is, a) a step of charging the valve stem 1 into a heated high-temperature lower mold, and b) a normal-temperature mold for injection and the valve stem 1 not heated by an injection molding machine. A step of injecting and injecting a rubber material into a cavity sealed by a high-temperature lower mold; and c, a step of filling the rubber material into the cavity details by clamping the heated high-temperature upper mold. d. a step of vulcanizing and molding the rubber material filled into the cavity details.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a rubber molding method for a tire valve according to the present invention will be described. FIG. 1 is an explanatory view of a rubber molding step of a rubber portion of a tire valve according to the present invention. FIG. 2 is a sectional view of a mold showing an injection / injection step of the rubber material of FIG. 1b of the present invention.
FIG. 2 is a sectional view of a mold showing a vulcanization molding step of the rubber material of FIG. 1d of the present invention.

In FIG. 1a shown in FIG. 1, the lower mold 6 for molding, which includes the lower nest 16 for molding and the guide bush 17 for positioning, is heated to a high temperature. The valve stem 1 is put into the lower molding die 6. Next, as shown in FIG. 1B, the injection mold 5 and the lower molding die 6 into which the valve stem 1 has been inserted are sealed, and a rubber material is injected and injected.

The injection mold 5 shown in FIG. 2 comprises a mounting plate 10 for mounting on an injection molding machine, a nest 11 for injection, an injection plate 14 on which injection pins 12 and positioning pins 13 are mounted. Spool 20, runner 21
Is provided. The injection plate 14 is provided with an oil circulation path 15 for controlling the temperature so that the temperature is kept constant at which the rubber material is not vulcanized. The injection insert 11 has four gates 19.

Also, the molding upper nest 18 shown in FIG.
Is made smaller in the radial direction and higher in the height direction.
As a result, in the state shown in FIG. 1D, the rubber is prevented from protruding at the time of sealing, and a pressure is generated for filling the cavity with details. The injection pin 12 is used for injection injection of the rubber material of FIG. 2 and for the upper mold 7 of FIG.
It is intended to form the rubber shape at the time of the first molding so that the hole of the valve stem 1 is not dull when tightening. The shapes of the injection nest 11 and the injection pin 12 are such that the injection dies 5 and the injection pin 12 do not adhere to the cavity surfaces of the injection nest 11 and the injection pin 12 when the injection mold 5 rises after the rubber material is injected.
In order to reduce the cavity volume of the molding upper nest 18 as much as possible and to improve the releasability, the injection nest 11 is used.
Is hemispherical and the injection pin is conical.

After the injection is completed, the injection mold 5 is raised, and then the injection molding is completed at another processing station, and the molding upper nest heated to a high temperature as shown in FIG. 1c. 18 and the upper molding die 7 including the mold pins 20 and the positioning pins 21 are sealed and vulcanized.

[0014]

As described above, according to the present invention, a rubber material is injected and injected into a cavity sealed by a high-temperature lower mold into which the valve stem 1 is charged and a normal-temperature mold for injection. Then, the rubber material is filled into the details of the cavity by clamping the hot upper mold for molding. This eliminates the excess vulcanized rubber in the conventional heating chamber, runner, and gate, thereby improving the material yield and reducing the injection pressure holding time, thereby shortening the injection molding time and reducing the manufacturing cost. The effect was obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a rubber molding process of a rubber portion of a tire valve according to the present invention.

FIG. 2 is a sectional view of a mold showing an injection / injection step of the rubber material of FIG. 1b of the present invention.

FIG. 3 is a sectional view of a mold showing a vulcanization molding step of the rubber material of FIG. 1d of the present invention.

FIG. 4 is a sectional view of a conventional tire valve molding die.

FIG. 5 is a sectional view of a tire valve product.

[Explanation of symbols]

1 Valve stem 2 Valve core 3
Valve cap 4 Cylinder 5 Injection mold 6
Lower mold for molding 7 Upper mold for molding 8 Injection pot 9
Spool 10 Mounting plate 11 Injection insert 12
Injection pin 13 Positioning pin 14 Injection plate 15
Oil circulation path 16 Lower nest for molding 17 Guide bush for positioning 18 Upper nest for molding 19 Gate 20
Mold pin 21 Heating chamber 22 Screw mechanism 23
Rubber push plate 24 runner 25 gate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 30:00

Claims (1)

[Claims] 1. A tire valve comprising a valve stem 1 having a valve core 2 mounted thereon, a valve cap 3 and a rubber portion.
In the rubber molding method of the valve stem 1 and the rubber portion, a: a step of putting the valve stem 1 into a heated high-temperature lower mold; and b, an injection mold not heated by an injection molding machine. A step of injecting a rubber material into a cavity sealed by a high-temperature lower mold into which the valve stem 1 has been charged; c. Filling the rubber material into the cavity details by clamping the heated upper mold. And d) vulcanizing and molding the rubber material filled into the cavity details.