JPH09174225A - Method for casting tubular body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the production cost of a tubular body while suppressing the occurrence of uneven thickness of the cast tubular body and facilitating the manufactured a mold and a core. SOLUTION: In the mold A, a cavity 6 for forming the tubular body and a core holding part for fitting and holding core prints 7A, 7B of the core 7 for forming a hollow part of the tubular body 2 are formed, and the core prints 7A, 7B of the core 7 are fitted and held by the holding part for the core. Further, after interposing an interval holding body 14 which is lost with the heat of the molten metal supplied into the cavity 6 between a forming surface opposed to the cavity 6 and the outer peripheral surface of the core 7 mutually opposed to the forming surface, the molten metal is poured into the cavity 6 to produce the tubular body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting a tubular body, such as a bend or a union, which is an example of a joint pipe, in which the axis of the pipe is bent.

[0002]

2. Description of the Related Art In a conventional tubular body casting method, as shown in FIG. 4, a mold A constituted by filling a mold 50 with green sand 51 is an example of a tubular body, as shown in FIG. And a cavity 52 for molding the pipe joint 2 in which the nut 1 is loosely fitted in a retaining state, and a skirting board 53A formed at both ends in the axial direction of the core 53 for molding the hollow portion 2A of the pipe joint 2. , 53B
Holding portion 54 for fitting and holding the nut, and the nut 1
The nut holding portion 55 for fitting and holding is formed, and the nut 1 is provided with the protective sand 56 forming a part of the molding surface in a state of covering the female screw 1a. Then, the nut 1 is loosely fitted and held in the core 53, and then both skirting boards 53A and 53B of the core 53 are fitted and held in the core holding portion 54 of the mold A, and the nut 1 is held in the mold A. After being fitted and held in the nut holding portion 55, the pipe joint 2 was manufactured by pouring the molten metal into the cavity 52.

[0003]

In the conventional tubular body casting method, both skirting boards 53A and 53B of the core 53 are fitted to the core holding portion 54 of the mold A, but the pipe joint 2 The tube axis is bent, and each skirting board 53A, 53B and the mold A
Since there is a minute gap between the core holding part 54 and the core holding part 54, the axis of the core 53 is easily displaced (tilted) within the cavity width of the cavity 52 due to the impact of the initial pouring, the buoyancy of the molten metal, etc.
Occasionally, uneven thickness was generated in the cast pipe joint 2. If such an uneven thickness allowance is larger than the cutting allowance after casting, it will result in a defective product, leading to a decrease in yield.If a large cutting allowance after casting is expected, the material cost will not only increase. However, the cutting process requires a lot of time and labor, and in any case, the manufacturing cost has risen. Further, as a method of suppressing the core misalignment of the core 53 during pouring, each of the two skirting boards 53A and 53B of the core 53 is increased in a direction orthogonal to the pipe axis core, and , The skirting boards 53A, 53B and the core A holding portion 54 of the mold A can be improved in accuracy, but in this case,
It takes a lot of time and effort to manufacture the mold A and the core 53, and the manufacturing cost cannot be reduced. In particular, when casting the pipe joint 2 in which the nut 1 is loosely fitted and held,
Since the mounting of the nut 1 on the core 53 is blocked by the skirting board 53A, the core 53 itself has to be divided into two and joined, which contributes to a rise in manufacturing cost due to a reduction in workability before pouring. Was.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress the occurrence of uneven thickness of a cast tubular body and to facilitate the production of a mold and a core. However, another object of the present invention is to provide a tubular body casting method capable of achieving a reduction in manufacturing cost.

[0005]

A feature of the tubular body casting method according to claim 1 of the present invention is that a cavity for molding a tubular body and a core skirting for molding a hollow portion of the tubular body are fitted in a mold. A core-holding portion for holding together is formed, and while the core skirting board is fitted and held in the core-holding portion, between the molding surface facing the cavity and the outer peripheral surface of the core opposite thereto. An intervening space holding material that disappears or sublimes due to the heat of the molten metal supplied into the cavity is interposed therebetween, and then the molten metal is poured into the cavity to manufacture the tubular body. According to the above characteristic configuration, the tube axis of the tubular body is bent, and even if there is a minute gap between the fitting surfaces of the core skirting board and the mold core holding portion, Since the part of the core that is located inside the cavity is supported by the molding surface facing the cavity via the spacing member at the set axis position, shock and buoyancy of the molten metal act on the core at the beginning of pouring. However, it is possible to prevent the axial center of the core from shifting until the spacing member disappears or sublimes due to the heat of the molten metal supplied into the cavity and is gasified. Moreover, when the spacing member disappears or sublimes and is gasified, a part of the annular space between the outer peripheral surface of the core and the molding surface facing the cavity is already filled with the molten metal. It is possible to prevent the core of the core from being displaced by the molten metal. Therefore, as compared with the conventional casting method, it is possible to suppress the occurrence of uneven thickness of the cast tubular body, so that the occurrence of defective products is reduced without taking an excessively large cutting allowance after casting. In addition, the required processing accuracy of the mold and the core is low, and as a result, the manufacturing cost can be reduced while facilitating the manufacture of the mold and the core.

A characteristic configuration of the tubular body casting method according to claim 2 of the present invention is that the spacing member is made of a styrofoam band that can be wound around the outer peripheral surface of the core. According to the above characteristic structure, depending on the type of the tubular body to be cast, even if the gap width between the outer peripheral surface of the core and the molding surface facing the cavity changes, the styrofoam wound around the outer peripheral surface of the core Since it can be dealt with by adjusting the number of windings, for example, the spacing member, the polystyrene foam formed in an annular shape corresponding to the annular space between the outer peripheral surface of the core and the molding surface facing the cavity, There is no need to prepare multiple types according to the type of tubular body to be cast, as in the case of being composed of sublimable ink that is solid at room temperature, and there is no need for molding equipment such as dies. Therefore, it is possible to promote the reduction of the casting cost of tubular bodies of various shapes.

According to a third aspect of the present invention, a tubular body casting method is characterized in that the tubular body is a pipe joint in which a nut is loosely fitted in a retaining state, and the nut is fitted and held in the mold. A nut holding part is formed,
The nut is provided with a protective sand forming a part of the molding surface in a state of covering the female screw, and further, the Styrofoam wound around the outer peripheral surface of the core is provided with the protective sand. It is in the point that the nut was fitted outside. According to the above characteristic configuration, the facing distance between the outer peripheral surface of the core and the molding surface of the protective sand of the nut can be maintained at the set interval by the Styrofoam wound around the outer peripheral surface of the core. It is possible to form the skirting board on one end side in the same cross-sectional shape as the core part in which the nut is loosely fitted, and as a result, the core itself is divided into two and joined as in the conventional casting method. There is no need, and the workability before pouring can be improved to promote the reduction of manufacturing cost.

[0008]

1 and 2 show an example of a tubular body in which the tube axis is bent. As shown in FIG. 3, a bronze cast cap nut 1 is loosely fitted in a retaining state. The casting method of the pipe joint 2 made of bronze casting is shown. First, in producing the mold A, as shown in FIG. 1 and FIG. 2A, a pipe joint is formed on the joint surface side of the raw sand 5 filled in each of the lower mold 3 and the upper mold 4. Forming recesses 6A, 6B constituting the cavity 6 of
Of the shell core 7 for forming the hollow portion 2A of the pipe joint 2, and a core holding portion 8 for fitting and holding the skirting boards 7A, 7B located at both ends in the axial direction of the shell core 7. Mating recess 8
A, 8B, and fitting recesses 9A, 9B forming a nut holding portion 9 for fitting and holding the cap nut 1 are formed, and in the green sand 5 on the upper mold 4 side, A sprue 10 and a riser 11 are formed in the molding recess 6B so as to communicate with each other. Moreover, the female screw 1a of the cap nut 1 is covered over the inner peripheral surface of the cap nut 1 and a part of both end surfaces continuous with the cap nut 1, and one of the molding surfaces is continuous with the molding recesses 6A and 6B. Protective sand 13 constituting the part is attached. One end side of the core 7, that is, the cap nut 1
The skirting board 7A on the side where the skirt is mounted is formed to have the same cross-sectional shape as the core portion that loosely fits and holds the cap nut 1, and the skirting board 7B on the other end side is orthogonal to the pipe axis. It is formed so as to project in the direction.

Then, of the outer peripheral surface of the core 7, the molding surface facing the cavity 6 and the outer peripheral surface of the core 7 opposite to the molding surface are located at a portion corresponding to the nut holding portion 9 of the mold A. Facing distance, that is, the molding surface 13 of the protective sand 13
In order to keep the facing distance between a and the outer peripheral surface of the core 7 facing each other at a set distance, it is an example of a spacing member that is lost and gasified by the heat of the molten metal supplied into the cavity 6. The styrofoam (lost foam member) 14 is wound with a thickness corresponding to the set interval, and then the cap nut 1 provided with the protective sand 13 is externally fitted onto the outer circumference of the wound styrofoam 14. I am doing it. In this external fitting state, the unwinding of the wound polystyrene foam 14 is prevented by the protective sand 13 of the cap nut 1, but if the free end of the polystyrene foam 14 is caught when the cap nut 1 is fitted, the foam polystyrene 14 will be caught. The free end of 14 may be temporarily fixed with an adhesive or the like.

Next, the skirting boards 7A and 7B of the core 7 to which the cap nut 1 is attached are fitted to the fitting recesses 8A and 8A on the lower mold 3 side.
8B, the upper mold 4 is superposed on the lower mold 3, and as shown in FIG. 2 (B), the molten metal is poured into the cavity 6 from the sprue 10 and the pipe shown in FIG. The joint 2 is manufactured. Then, as described above, the pipe axis of the pipe joint 2 is bent into an L shape, and the fitting surfaces of the skirting boards 7A and 7B of the core 7 and the core holding portion 8 of the mold A are fitted. Even if there is a minute gap, the part of the core 7 located inside the cavity 6 is transferred to the molding surface 13a of the protective sand 13 on the side of the cap nut 1 through the expanded polystyrene 14 wound around the part. Since it is supported, even if impact or buoyancy of the molten metal acts on the core at the initial stage of pouring, until the Styrofoam 14 is lost and gasified by the heat of the molten metal supplied into the cavity 6, It is possible to prevent the axis of the child 7 from shifting (tilting). Moreover, when the styrofoam 14 disappears and is gasified by the heat of the molten metal, a part of the annular space between the outer peripheral surface of the core 7 and the forming surface facing the cavity 6 is already filled with the molten metal. It is possible to prevent the axial center of the core 7 from being displaced (tilted) by the filled molten metal.

Each of the core 7 and the protective sand 13 is made of a mixture of silica sand and phenol resin. In addition, in the embodiment, the gas generated by the disappearance of the Styrofoam 14 is supplied to the baseboard 7A of the core 7,
It is configured to be discharged to the outside through a gap between the mating surfaces of the upper and lower molds 3, 4 through 7B.

Other Embodiments In the above-described embodiment, the core 7 is a shell
Although the child has been described as an example, it is not limited to this.
No, for example, cores with clay as a binder, CO _TwoCore,
There are air set cores, etc. In the above-mentioned embodiment, it is supplied into the cavity 6.
Holds an interval where gas disappears or sublimes due to the heat of the melt
As the material 14, a strip-shaped member which is one of the lost foam members
Explained with Styrofoam (expanded polystyrene) as an example
However, it is not limited to this.
A low melting point thermoplastic resin such as ethylene may be used.
Between the outer peripheral surface of the core 7 and the molding surface facing the cavity 6.
Styrofoam molded into a cylindrical shape corresponding to the annular space of
May be used and is also supplied in the cavity 6.
Circles solid ink at room temperature that sublimes due to the heat of molten metal
You may implement using what was shape | molded by the cylindrical shape. In the above embodiment, the tubular body 2 is a nut.
Example of L-shaped pipe joint that is loosely fitted in position 1
However, the present invention is not limited to this,
For example, pipes such as elbows and bends that do not have the nut 1.
It may be a joint, or a pipe body other than the pipe joint.
Is also good.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a tubular body (pipe joint) casting method of the present invention.

[Fig. 2] (a) is a horizontal sectional view before pouring. (B) is a horizontal sectional view after pouring.

FIG. 3 is a perspective view of a cast pipe joint.

FIG. 4 is a horizontal sectional view showing a conventional tubular body (pipe joint) casting method.

[Explanation of symbols]

 A Mold 1 Nut (cap nut) 1a Female thread 2 Tubular body (pipe joint) 2A Hollow part 6 Cavity 7 Core 7A Baseboard 7B Baseboard 8 Core holding part 9 Nut holding part 13 Protective sand 14 Spacing material (Styrofoam)

Claims (3)

[Claims] 1. A method for casting a tubular body (2) having a bent pipe axis, wherein a cavity (6) for molding the tubular body (2) and a hollow portion of the tubular body (2) are provided in a mold (A). (2A) A core-holding part (8) for fitting and holding the skirting boards (7A, 7B) of the molding core (7) is formed, and the core (7) is formed in the core-holding part (8). ) Is fitted and held in the cavities (6) between the molding surface facing the cavities (6) and the outer peripheral surface of the core (7) facing the cavities (7A, 7B). A tubular body casting method for producing a tubular body by interposing a space holding material (14) which disappears or sublimes by the heat of the supplied molten metal and then pours the molten metal into the cavity (6). 2. The tubular body casting method according to claim 1, wherein the spacing member (14) is a band-shaped styrofoam that can be wound around the outer peripheral surface of the core (7). 3. A pipe joint in which the tubular body (2) is loosely fitted in the nut (1) in a retaining state, and the nut (1) is fitted and held in the mold (A). Holding portion (9) is formed and the nut (1) is formed.
Is provided with a protective sand (13) forming a part of the molding surface in a state of covering the female screw (1a), and further, a styrofoam wound around the outer peripheral surface of the core (7) ( 1
The tubular body casting method according to claim 2, wherein a nut (1) provided with the protective sand (13) is externally fitted to (4).