JPH0247308B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a low-pressure casting mold for a tire molding and vulcanization mold (hereinafter simply referred to as a tire mold).

(Prior art) In the casting of tire molds, a method called low-pressure casting, in which a cast product is formed by applying pressure to a molten metal, such as an aluminum alloy molten metal, and causing it to rise through a stalk, is currently being adopted. It is being

The adoption of this method in tire mold casting is
Although this method is extremely effective in solving the problems of conventional gravity casting, it still has various drawbacks, so further improvements have been made, including a sprue bushing installed near the stalk or sub-riser connection. (Utility Model Publication No. 54-28416), or a cast plaster segment having substantially the same shape as the outer surface of the tire is placed on a thick fireproof heat insulating base. This is used as a core, and this is placed in a main mold consisting of an upper mold and a lower mold lined with a fireproof insulation layer, and a circular runner is formed with the lower and side surfaces of the fireproof insulation base and the lining fireproof insulation layer. (Special Publication No. 59-11383) has been proposed.

(Problems to be Solved by the Invention) However, in the former proposal, for example, the distance to the cavity is small and its capacity is small, so even though it is effective to some extent in terms of heat insulation of the runner, It is unsuitable for applications that require a large amount of molten metal, such as for large tire molds, and even if the latter can be improved, the base on which the plaster segment for casting is placed is large, and therefore the main mold As the capacity of the mold increases, the space for filling the molten metal within the mold also increases, which poses problems in maintaining the uniformity of the molten metal and in economical efficiency.

In addition, ``Collection of Examples of Field Casting Techniques,'' edited by Shinobu Yamaguchi, illustrates a brake drum mold that has multiple runners extending radially from the sprue to the cavity. However, even though this runner has the advantage of reducing the molten metal filling space, because the runner has a uniform depth, there is fluctuation in the flow of molten metal from the sprue, causing the molten metal to flow evenly into the cavity. The problem is that the molten metal lacks directional solidification.

The present invention deals with the above-mentioned actual situation, and aims to simplify the structure of the runner and the holding of the gypsum segment members.
The aim is to solve all of the above problems at once.

(Means for Solving the Problems) That is, a feature of the present invention that satisfies the above object is that, in the low-pressure casting mold for the tire mold, a runner is formed on the inner surface of the lower mold of the main mold. The recessed groove is filled with a fireproof insulation filler for a runner, which is formed in multiple stripes on the upper surface in a straight radial or curved blade shape at appropriate angular intervals from the sprue center, and The concave groove of the heat insulating filling material is formed to become shallower as it goes outward from the center, and
A plurality of strips are formed on the upper surface of the fireproof heat insulating base plate on which the casting gypsum member is placed and held, and in the lower part of the base plate by grooves on the upper surface of the fireproof heat insulating filler, which communicate from the sprue to the cavity space around the outer periphery of the casting gypsum member in the main mold. This is due to the formation of a runner that gradually becomes shallower toward the outside.

Note that the multiple radial or curved blade-shaped concave grooves extending outward from the sprue are not necessarily limited to one location on the inner surface of the lower mold, but may be placed at two or more locations from the top of the molten metal evenly distributed. It is particularly effective for mold molding of large tires.

(Function) In the above mold of the present invention, after the upper and lower molds of the main mold containing the core are aligned to determine the casting position, compressed air is pumped into a holding furnace installed at the bottom (not shown). Alternatively, when compressed gas is blown in, the gas pressure causes the molten metal such as aluminum alloy in the holding furnace to rise from the bottom of the stalk through the inside of the stalk, and is divided into multiple runners from the sprue at the top of the stalk to form the mold. filled inside.

At this time, the runner, which is formed to become shallower toward the outside, has the effect of reducing the flow of the molten metal from the sprue, causing it to flow uniformly into the cavity, and directional solidifying the molten metal.

The filled molten metal is directionally solidified from the upper part of the mold toward the sprue while being subjected to gas pressure applied to the surface of the molten metal, and a desired tire mold is formed in the upper part of the base plate.

(Example) Hereinafter, specific examples of the mold of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a main part of a low-pressure casting apparatus for a tire mold using the mold of the present invention, and FIG. 2 shows an aspect of forming a runner.

In these figures, 1 is a plaster member for casting, and 2 is a relatively thin plate-shaped fireproof and heat-insulating base plate on which the plaster member 1 for casting is placed and held. A core C is formed and housed in a main mold M consisting of an upper mold 3 and a lower mold 4.

Here, the outer surface of the casting plaster member 1 has substantially the same shape as the outer surface of the tire in order to fit the outer surface of the tire, and is usually divided into an appropriate number of segments in the shape of a thin disc. It is placed and fixed concentrically on the fireproof heat insulating base plate 2 of.

In addition, as mentioned above, the fireproof heat insulating base plate 2 is formed into a disk shape with a relatively thin wall, and its material is usually
Although the material used for the plaster member for casting is used, the material is not necessarily limited to this, and ceramic materials and the like can also be used.

However, it is preferable that the body expansion coefficient is approximately the same as that of the plaster member for casting.

On the other hand, the main mold M consisting of the upper mold 3 and the lower mold 4 is similar to the known mold, but the inner surface of the lower mold 4 has a sprue 9 that opens at the upper end of the stalk 10 through which the molten metal rises to the upper surface. It is filled with a fireproof insulation material 5 for runners in which at least a plurality of radial grooves 8 (six in the figure) are formed, which extend outward in a straight or curved manner around the center. It is formed so that it gradually becomes shallower as it goes. These plural grooves 8
and the fireproof and heat insulating base plate 2 form a radial runner which becomes gradually shallower toward the outside, communicating from the sprue 9 to the space of the cavity 11 on the outer periphery of the casting gypsum member 1 at the bottom of the base plate 2.

The refractory heat insulating material 5 filled into the inner surface of the lower mold 4 may be cast gypsum as described above, but may also be made of other materials with the same effect, such as ceramic.

In the figure, 6 is a sealing member, and 7 is casting sand, for example, core sand solidified with _CO2 , and the sealing member 6 can also be filled with asbestos or a similar casting sand to the above-mentioned core sand. .

The mold of the present invention has the above-mentioned configuration, and the molten metal such as aluminum alloy rising through the stoke 10 in the same way as in known low-pressure casting passes through the sprue 9, passes through the refractory insulating base plate 2 and the refractory insulating material 5. The cavity space 1 on the outer periphery of the casting plaster member 1 is passed through the runner formed by the groove 8 of
1 and fill it up.

At this time, since the runner 8 is formed to become gradually shallower as it goes outward, the flow of the molten metal from the sprue 9 is reduced, and the molten metal flows uniformly into the cavity 11, resulting in directional solidification of the molten metal. It has the effect of causing

Then, the filled molten metal is directionally solidified sequentially from the upper part according to the outer surface shape of the casting gypsum member 1, and a tire mold is formed. Although the gas generated in the mold at this time is not shown,
When appropriate, degas from the gas vent hole in the upper mold.

In this way, a tire mold can finally be obtained by low pressure casting.

(Effects of the Invention) As described above, the present invention fills the inner surface of the lower mold with a fireproof insulating material having a plurality of straight radial or curved grooves extending outward from the sprue, and extends the grooves from the center. The base plate for placing and holding the casting gypsum member is formed relatively thin and becomes shallower as it goes outward, and becomes gradually shallower towards the outside of the plurality of strips that communicate from the sprue to the cavity space around the outer periphery of the casting gypsum member. Since multiple runners are formed using a fireproof insulation material with concave grooves and a thin plate-like base plate, it is easy to form runners, and the molten metal flows smoothly.
Not only does the molten metal flow evenly into the cavity, but wasteful filling of the molten metal, such as in an annular runner, is prevented, and the molten metal can be distributed and filled in an economical manner.

Since the runner is formed to become shallower as it goes outward, the molten metal from the sprue can be flowed with less turbulence and evenly flowed into the cavity, allowing the molten metal to solidify directionally.

Further, since the fireproof heat insulating material that receives the casting plaster member is relatively thin, there is no wastage of space within the main mold, and it is easy to utilize the space to the maximum extent.

Furthermore, as mentioned above, since the recessed groove is formed on the upper surface of the fireproof insulation material to form a runner, it has an excellent heat-insulating effect, and the molten state of the molten metal in the runner can be maintained uniformly and well, making it suitable for directional solidification. It also has the effect of obtaining high-quality tire mold castings, and is expected to be industrially effective as a low-pressure casting mold.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a low-pressure casting apparatus for a tire mold using a mold according to the present invention, and FIG. 2 is a schematic plan view showing a state in which a runner is formed. 1... Plaster member for casting, 2... Fireproof insulation base plate, C... Core, 3... Upper mold, 4... Lower mold, M... Main mold, 5... Fireproof insulation material, 8... Concave Groove, 9... sprue, 10... stoke, 11... cavity.

Claims (1)

[Claims] 1. Consists of a casting plaster member having substantially the same shape as the outer surface of the tire, a core consisting of a fireproof and heat insulating base plate for mounting and holding the member, and a main mold consisting of both upper and lower molds that accommodate the core inside. The lower mold of the main mold is filled with a refractory heat insulating material for runners having a plurality of straight or curved grooves extending outward at appropriate angular intervals on the inner surface thereof. and the concave groove of the fireproof insulation material for runners is formed to become shallower as it goes outward from the center,
When the core is housed in the main mold, the plurality of concave grooves and the lower surface of the fireproof heat insulating base plate communicate with the cavity on the outer periphery of the casting gypsum member in the main mold, and the runners gradually become shallower toward the outside. A low-pressure casting mold for a tire molding and vulcanization mold, characterized in that it is formed by forming: