JPS5911383B2 - Low-pressure casting mold for tire molding and vulcanization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire molding and vulcanization mold (hereinafter referred to as a tire mold).

) relates to a mold consisting of a main mold and a refractory insulation core for low-pressure casting.

Conventionally, in gravity casting, tire molds are cast by arranging casting stones having the same shape as the outer surface of the tire in the form of a core on a metal base, and then pressing. The molten metal was surrounded by a main mold with multiple cylinders that secured the hot water part, and molten metal was poured into a cavity formed by these cores and the main mold.

However, the above method has the following drawbacks.

(1) The weight of the feeder alone cannot apply sufficient pressure to the core surface, resulting in poor flow of the metal and making it difficult to accurately transfer substantially the same shape as the tire outer surface onto the cast product. ,
This will deteriorate the surface appearance of the product.

(2) Air entrainment during injection of molten metal causes turbulence in the flow of molten metal, resulting in surface defects such as molten metal wrinkles.

(3) Thermal non-uniformity occurs between directly below the feeder and other parts, which deteriorates the dimensional accuracy of the cast product.On the other hand, in low-pressure casting, the above problems do not occur, but the upper part of the core and stalk Conventional low-pressure casting of tire molds without special consideration for the distance and spacing of the runners had the following drawbacks.

(1) When filling the cavity with molten metal, since the shape of the cast product is generally a large ring, the distance of the runner from the top of the stalk is long, and therefore the lower mold and core forming the runner are kept warm. If the force is insufficient, the runner will solidify while the product is still in an unsolidified state.

For this reason, shrinkage cavities occur inside the product part of the cast product and on the surface of the product part of the cast product, making it easy to produce defective products.

(2) The metal base on which the plaster segment for casting is placed is
Since it is cast using fermented metal, the thermal influence on the molten metal of this base is very large, and depending on the material of this base, large dimensional changes are likely to occur.

For example, in the case of a steel base, the casting plaster segments assembled in an annular shape on the base are affected by this dimensional change, which significantly impairs the accuracy of the casting, and the finished mold is completely defective. It ends up being a good product.

This invention was made in order to completely solve the above-mentioned problems of conventional gravity and low-pressure casting. The object of the present invention is to provide a low-pressure casting mold that can produce a high-quality, high-precision tire mold by making the following improvements.

This invention will be explained in detail below based on the drawings.

1 is a core consisting of a gypsum segment 11 for casting and a fireproof heat insulating base 12.

The casting gypsum segment 11 has substantially the same shape as the outer surface of the tire, is divided into several to several pieces in the radial direction, and is arranged concentrically and annularly on the disc-shaped fireproof and insulating base 12. , the outer surfaces should match, and they would be fixed side by side without any gaps.

The fireproof heat insulating base 12 has a disk shape and has a sufficient thickness (
The sufficient thickness refers to a thickness that guarantees the length of the runner and the stability of the segments, which will be described later.

), and the material used is one whose coefficient of expansion is comparable to that of the plaster segment for casting (for example, ceramic).

Particularly, when foundry gypsum is used for the fireproof heat insulating base 12, good effects can be obtained as will be described later.

2 is a lifting jig; 3 is a main mold of a low-pressure casting apparatus consisting of a cylindrical upper mold 31 and a lower mold 32; It is something that can be raised.

33 is a fireproof heat insulating layer lined on the upper surface of the lower mold.

The mold of the present invention consists of an upper mold core 1 and a main mold 3.

After lifting and fixing the core 1 inside the upper mold 31,
When the upper mold 31 is lowered and the upper mold 31 and the lower mold 32 are aligned at the casting position, the space between the main mold 3 and the core 1 forms a cavity 4, and the lower and side surfaces of the fireproof and insulating base 12 are formed. An annular runner 5 is formed between the refractory heat insulator layer 33 and the refractory heat insulator layer 33.

The runner 5 has a longer distance from the sprue to the cavity in response to the thick fireproof ML heat base 12, and forms an annular space to ensure the minimum required space capacity.

The gist of the present invention lies in the structure of the mold described above, and its function will be described below along with the process of low-pressure casting of a tire mold using the mold of the present invention.

The upper mold 31 of the main mold 3 in which the core 1 is installed is fitted to the lower mold 32, and set at the casting position.

Next, compressed air or compressed gas is supplied through the blowing port 6 to the molten metal (minutan) 8 such as aluminum alloy in the holding furnace 7.
Blow into the space above.

Due to the mega gas pressure, the bi-molten metal 8 rises inside the stalk 9 from the bottom of the vertically erected stalk 9 against gravity,
The sprue at the top of the stalk fills the mold.

That is, a large amount of hot water 8 passes through the runner 5 and is smoothly pushed up and filled into the key pit 4.

The molten metal 8 filled in the mold undergoes directional solidification from the top of the mold toward the sprue while receiving gas pressure applied to the surface of the molten metal. However, in the mold of the present invention, in particular, The runner 5 is well maintained in a molten state until the molten metal facing the casting gypsum segment 11 is completely solidified.

Since the low-pressure casting mold for tire molds of the present invention has the above-described configuration, it has the following various superior effects compared to conventional molds.

■ A thick fireproof and insulating base generally forms a runner with a length and capacity suitable for forming large tire molds, allowing molten metal to smoothly fill the cavity and achieve good directional solidification.

In other words, forming large tire molds requires a large amount of hot metal, and it was difficult to process this large amount of hot metal using conventional low-pressure casting molds. By the way, we have overcome this problem of mass processing.

■ Casting gypsum segments are placed on a thick, refractory, insulated base, so they are stable and do not have ridges between segments.

■ If the base is a thin fireproof insulating base or a metal base, the heat received from the molten metal will cause abnormal dimensional changes, causing the casting plaster segment to move during casting and resulting in poor dimensional accuracy; however, in the present invention, Since the body expansion rate of the heat-insulating base was made comparable to that of the cast plaster segment, the above-mentioned defects were completely eliminated.

■Especially when casting plaster is used for the fireproof insulation base. In addition to obtaining the optimum base thickness in relation to the amount of molten metal, it is possible to minimize the movement of the casting plaster segment during casting, and also to avoid cracking despite sudden heat shocks. Therefore, a highly accurate tire mold casting can be obtained.

As described above, according to the present invention, since the tire mold is large,
Although the conventional low-pressure casting mold structure would be incomplete, the mold structure of the present invention has a remarkable effect in that a high-quality tire mold can be obtained.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of a low-pressure tire mold casting apparatus using the mold of the present invention. DESCRIPTION OF SYMBOLS 1... Core, 11... Plaster segment for casting, 12... Fireproof insulation base, 2...
...Lifting jig, 3...Main mold, 31...
・Upper mold, 32...Lower mold, 33...
・Fireproof insulation layer, 4... Cavity, 5...
... Yudo.

Claims (1)

[Scope of Claims] 1(a) A casting gypsum segment 11 having substantially the same shape as the outer surface of the tire, on which the segment 11 is placed, and having a required thickness and the segment 1
Fireproof insulation base 1 made of a material with a body expansion coefficient equivalent to 1.
2, (b) a main mold 3 consisting of an upper mold 31 and a lower mold 32 facing the fireproof heat insulating base 12 whose upper surface is lined with a fireproof heat insulating layer 33; For tire molding and vulcanization, an annular runner 5 is formed by the lower and side surfaces of the fireproof heat insulating base 12 and the fireproof heat insulating layer 33 in the casting position where the core 1 is housed in the main mold 3. Mold for low pressure casting. 2. The low-pressure casting mold for a tire molding and vulcanization mold according to claim 1, wherein the fireproof heat insulating base 12 is made of casting gypsum.