JP7165614B2 - Angular straight pipe manufacturing method - Google Patents

Description

The present invention relates to a method for producing straight angled pipes by centrifugal casting.

As shown in FIG. 5, a cast-iron pipe widely used for water pipes and the like consists of a cylindrical straight pipe portion 1 having a constant inner and outer diameter and a socket provided at one end thereof having a larger inner and outer diameter than the straight pipe portion 1. Many of them are composed of a portion 2 and an insertion port portion 3 provided at the other end and having an inner diameter equal to that of the straight pipe portion 1 . As shown by the chain line in the figure, this cast iron pipe P1 is constructed by inserting the insertion port ₃ of _another cast iron pipe P1 into the socket portion 2 of _one cast iron pipe P1 to construct a pipeline in a straight line. It is used in cases and is mainly manufactured by centrifugal casting.

On the other hand, a curved pipe is used for a pipeline having a curved portion. Centrifugal casting is difficult for this bent tube, and it is mainly manufactured by the pouring method, resulting in a high manufacturing cost.
For this reason, in the straight pipe P1 of FIG. ₅ shown in FIG. An angled straight pipe P has been proposed in which the inner surface of the straight pipe portion 2 is inclined at a required angle θ with respect to the axis o of the straight pipe portion 1 (see Patent Document 1 and FIG. 4). It is said that this angled straight pipe P can be manufactured by centrifugal casting (see Patent Document 1, FIG. 6). A curved pipeline is constructed by inserting and bending at each connection portion by an angle θ.

By the way, in centrifugal casting, defects such as blowholes and shrinkage cavities are less likely to occur inside the casting, the material is finely dense, and a casting of good quality such as mechanical properties can be obtained smoothly. For this reason, many cast iron pipes widely used for water pipes and the like are manufactured by the centrifugal casting method.
For example, as shown in FIG. 7, the centrifugal casting machine rotates a cylindrical mold (casting mold) 11 by rollers 12, and feeds molten metal a into a casting trough 20 through ladles 13 and 14. By casting (pouring) the molten metal a into the rotating mold 11 through the trough 20 and uniformly distributing the molten metal a on the inner surface of the mold 11 by centrifugal force, in principle, the pipe is formed around the axis. A cylindrical molten metal layer (cast iron pipe) P having a uniform thickness is formed.

At this time, as shown in the figure, the trough 20 is fixed and the mold 11 is moved in the longitudinal direction by the carriage 15, or the trough 20 is moved in the longitudinal direction of the mold 11 by the carriage 15. Then, the trough 20 and the mold 11 are moved relative to each other in their longitudinal direction (axial direction) and cast (Patent Document 2, paragraph 0003, FIG. 1).
The trough 20 is generally composed of a chute 21 for guiding the molten metal a from the ladle 14, a chute case 22 fixed to the carriage 15 by supporting and fixing the chute 21, and a chute case 22 fixed to the chute case 22 to guide the molten metal a from the chute 21. and a liner 23 for guiding the molten metal a into the mold 11 . In the figure, 14a is a support base for the ladle 14, 16 is a rail for moving the carriage 15, and 17 is a casing (cover) for covering the mold 11 on the carriage 15, which may be omitted (not attached).

In the centrifugal manufacture of this cast iron pipe P, particularly for large-diameter pipes, the core 18 is often used to form the socket portion 2 . At this time, it is difficult to create a product shape from as-cast, and after annealing, it is difficult to create a shape within the dimensional tolerance, and a feature of centrifugal casting is that impurities rise to the inner surface to obtain a good casting surface. Therefore, as shown in FIGS. 8 and 9, a machining allowance b (braided hatched portions b ₁ and b ₂ ) may be provided on the premise of machining such as cutting.
At this time, as shown in FIG. 8, it is conceivable (possible) to provide only the barrier plate 19 at the opening of the socket 2 and carry out centrifugal casting. Compared to the case where the machining allowance _b2 is secured by the element 18, there are many parts (iron parts) that must be removed by machining ( _b1 > _b2 ), the yield is poor, and the machining time is long.

Further, when the inner surface of the socket portion 2 of the angled straight pipe P is formed by cutting (finishing), the straight pipe 1 is cut along the same vertical plane (the vertical plane in the up-down direction in FIG. 6) of the axis o of the straight pipe 1, It is divided into an upper partial cross section 2a and a lower partial cross section 2b, and as shown in FIG. When the upper partial cross section 2a is overlapped, as shown in FIG. 1(c), the portion where the cast portions of both partial cross sections 2a and 2b overlap (dotted portion in FIG. 1(b)) becomes a machining allowance. Therefore, if the core 18 has the outer peripheral surface shape of the portion where the machining allowance b is connected, the core 18 is symmetrical about the axis o (having the same geometrical moment of inertia). A cast iron pipe P is manufactured by centrifugal casting with a core 18, and in the inner surface shape socket portion 2 of FIG. 6 (FIG. 10(a)) to obtain an angled straight pipe P by rotary cutting.

Japanese Utility Model Publication No. 01-8786 Japanese Patent Application Laid-Open No. 2006-150432 JP 2011-212732 A

In the centrifugal casting of the angled straight pipe P in Patent Document 1, the core 18 is loaded in the socket 2 (see FIG. 6 of the same document), and the core 18 and the cast part of the socket 2 do not coincide with the center of gravity (central axis) o of the straight pipe portion 1 (because they are deviated) (see FIG. 1 of the present application), when the mold 11 rotates, its rotation axis is the straight pipe Since it is the axis o of the part 1, the primary moment of area of the mold 11, the core 18, and the angled straight pipe P to be cast with respect to the axis o is different over the entire length thereof, and the centrifugal force causes the mold 11 to vibrate. As a result, the mold 11 deviates from the rollers 12, making centrifugal casting difficult, and casting quality deteriorates.

Further, the manufacturing of the angled straight pipe P by cutting as described above requires a large amount of finishing allowance due to cutting, resulting in poor workability. For example, in the socket part 2 of the UR type (R system) φ2600×4m, θ: 3° joint structure, in FIG. only a modest reduction.

SUMMARY OF THE INVENTION Under the above circumstances, an object of the present invention is to smoothly manufacture an angled straight pipe P by centrifugal casting and to reduce the manufacturing cost.

In order to achieve the above object, the present invention firstly reduces the finishing allowance for the inner surface of the socket portion of the angled straight pipe P formed by the outer peripheral surface of the core by inserting the core obliquely. be.
By inclining the core (inclining the axis c of the core with respect to the axis o), the outer peripheral surface can be made to approximate the shape of the inner surface of the socket portion of the angled straight pipe P. That is, the finishing allowance can be made extremely small.
Next, a counterweight (balance weight) is attached to the core and the mold, and the finishing allowance is changed to balance the entire length of the axis of the mold.
If the balance is achieved in this way, the mold 11 will hardly vibrate due to the centrifugal force.

Specifically, it consists of a straight pipe portion, a socket at one end, and an insertion port at the other end, and the outer surface of the socket is parallel to the axis of the straight pipe. , in a method of manufacturing an angled straight pipe by centrifugal casting, wherein the inner surface of the socket portion is inclined at a required angle with respect to the axis of the straight pipe portion, a core having an outer peripheral surface along the inner surface of the socket portion; , the center of the core is loaded into the socket with the axis inclined at a required angle with respect to the axis of the straight pipe, and the total center of gravity of the core and the cast iron cast in the socket is the straight pipe A counterweight is provided on the core or mold so that it approaches the central axis of
A configuration can be adopted in which the finishing margin of the cast portion of the socket is provided so that the total center of gravity of the core and the cast iron cast into the socket is close to the central axis of the straight pipe portion.

Since the present invention is configured as described above to balance the entire axial center length of the mold, it is extremely unlikely that the mold will vibrate due to the centrifugal force during centrifugal casting of an angled straight pipe. less, smoother and cheaper to manufacture.

1 is a partial cross-sectional view of an embodiment of a method for manufacturing an angled straight pipe according to the present invention; FIG. Partial cross-sectional view of the same other embodiment Partial cross-sectional view of the production mode of the core of the same embodiment Partial cross-sectional view of the same other embodiment Cross section of cast iron pipe Partial cross section of angled cast iron pipe Schematic cross section of centrifugal casting Partial cross-sectional view for manufacturing explanation of cast iron pipe Partial cross-sectional view for explaining the manufacturing of other cast iron pipes Explanatory diagram of casting action of cast iron pipe

FIG. 1 shows an embodiment of a method for manufacturing an angled straight pipe P according to the present invention. As shown in the figure, the angled straight pipe P of this embodiment is composed of a straight pipe portion 1, a socket portion 2 at one end thereof, and an insertion portion 3 at the other end. The surface is parallel to the axis o of the straight pipe portion 1, and the inner surface of the socket portion 2 is inclined at a required angle θ with respect to the axis o of the straight pipe portion 1. As shown in FIG. This angle θ is 1 to 5 degrees.

The core 18 forming the inner surface of the socket portion ₂ has an outer peripheral surface with a finishing margin b2 removed, and the core 18 is attached to the mold 11 with its axis c inclined by θ degrees with respect to the axis o of the straight tube portion 1 . to load. At this time, since the axis c of the core 18 is inclined by .theta. degrees with respect to the axis o of the mold 11, the sectional primary moment around the axis o including the core 18 is not uniform.
For this reason, as shown in the same figure, part of the outer peripheral surface of the core 18 is removed, and a finishing allowance b3 for the black _- painted portion is further formed so that the geometrical moment of inertia about the axis o is uniform. make sure to At this time, in FIG. ₁ , the upper inner thick portion 2a1 of the receptacle portion 2 is longer toward the opening side (left side in FIG. ₁ ) than the lower thick portion 2b1. The moment of inertia increases toward the upper side. For this reason, the _finishing allowance b3 is formed _on the lower side _, and the drawing of FIG. Then, confirm how much the center of gravity position in the drawing deviates from the axis o, add a rough weight to the inner diameter of the socket, and recalculate with 3D-CAD so that the center of gravity is on the axis o to At this time _, the cross section ( _FIG . 1) of the finishing margin b3 is such that the thickness gradually decreases toward both sides in the circumferential direction, or the thickness decreases stepwise (block-like) and is absorbed by the finishing portion b2. to

1, the mold 11 is moved to the left as shown in FIG. A cast iron pipe of the angled cast iron pipe P is manufactured by centrifugal casting performed from the part 2 side toward the insertion port part 3 side. At this time, at the beginning of the pouring a, the rotation of the mold 11 is slow so that the molten metal a rotates over the entire area including the finishing margins b ₂ and b ₃ of the socket 2, and after the casting of all the molten metal a is completed, Shift to normal high speed rotation. For example, when the nominal diameter is 1500, GNo. : 20 to 24, at high speed rotation, GNo. : 49-57. In addition, GNo. is an index representing the centrifugal force generated by tube rotation, and GNo. =V2/r x 1/g (V: tube peripheral velocity, r: tube radius, g: gravitational acceleration).

In this manufacturing action, since the first moment of area with respect to the axis o including the core 18 in the socket portion 2 is substantially the same over the entire length of the mold axis o, and the center of gravity is located on the axis o, the mold 11 rotates without vibrating for smooth casting.
The cast iron pipe cast in this way has the inner surface of the socket part 2 centered on its axis c (axis o), the upper part 2a being the finished part b ₂ and the lower part 2b being the finished part b ₂ and b3 are respectively cut to obtain an angled cast iron pipe P shown in FIG. ₆ having an upper partial cross section 2a and a lower partial cross section 2b shown in FIG.

In the embodiment of FIG. 2, a counterweight 30 is embedded in the core 18, and the counterweight 30 makes the sectional primary moment of the socket 2 around the axis o including the core 18 uniform. It is designed to The size and weight of this counterweight 30 can be determined by using 3D-CAD to create the drawing of FIG. After confirming whether there is a deviation, an appropriate core 18 and a counterweight 30 having an appropriate weight are inserted into the hole, and the center of gravity is recalculated by 3D-CAD so that the position of the center of gravity is on the axis o.

The fitting hole in the core 18 of the counterweight 30 is, for example, when forming the core 18 using the holding band described in Patent Document 3, as shown in FIG. 32, a wooden pattern 33 having a draft angle of a required shape is placed outside the holding band 31 to form the fitting hole 34. As shown in FIG. According to this forming means, if the angle .theta. changes, the wooden pattern 33 can be shaped accordingly. A mode in which the counterweight 30 is embedded in the core 18 can also be adopted.

In the state shown in FIG. 2, in which the core 18 is loaded in the socket 2, a cast iron pipe of an angled cast iron pipe P is similarly produced by centrifugal casting shown in FIG. At this time, due to the presence of the counterweight 30, the cross-sectional primary moment of the socket 2 including the core 18 is substantially the same over the entire length of the mold axis o, and the center of gravity is located on the axis o, so that the mold 11 rotates without vibrating for smooth casting. The cast iron pipe thus cast becomes an angled straight pipe P. This angled straight pipe P does not form a finishing margin, but by increasing the accuracy of the outer peripheral surface of the core 18, the finishing margin can be made extremely small.

1, the counterweight 30 can also be fixed to the outer surface of the mold 11 by appropriate means such as bolting, welding, etc. so that it does not drop when the mold 11 rotates. The size, weight, and mounting position of this counterweight 30 are determined by using 3D-CAD to create the drawing of FIG. Then, the appropriate size, weight, and position of the counterweight 30 are recalculated by 3D-CAD so that the center of gravity position is on the axis o.

According to the mold 11 with the counterweight 30, similarly, according to the centrifugal casting shown in FIG. Since the center of gravity is located on the axis o, the mold 11 rotates without vibrating and smooth casting is performed. The cast iron pipe thus cast becomes an angled straight pipe P.

In addition, in the embodiment shown in FIG. 1, the core 18 shown in FIG. ₂ can be used without the finishing margin b2. At this time, of course, a _finishing allowance b3 is provided.
Further, when the counterweight 30 is attached to the core 18, as shown in _FIG . 4, a finishing margin b2 for finishing the groove portion 2c can be formed.
In this way, the embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope of equivalence to the scope of claims.

1 Straight pipe portion of cast iron pipe 2 Socket portion 3 Insertion portion 11 Mold 18 Core 19 Shear plate 20 Pouring trough (casting trough)
30 Counterweight a Molten metal (pouring)
b ₁ , b ₂ Finish allowance b ₃ Finish allowance for center-of-gravity adjustment c Shaft center (central axis) of socket part of angled straight pipe
o Axis (central axis) of the same straight pipe (mold)
θ Inclination angle of the shaft center of the socket of the angled straight pipe

Claims (3)

It consists of a straight pipe portion (1), a socket portion (2) at one end thereof, and an insertion portion (3) at the other end thereof, and the outer surface of the socket portion (2) is the straight pipe portion (1). and the inner surface of the socket (2) is inclined at a required angle (θ) with the axis (o) of the straight pipe (1). A method for manufacturing a straight pipe (P) by centrifugal casting,
A core (18) having an outer peripheral surface along the inner surface of the socket (2) is inserted into the socket (2) with the axis (c) of the core (18) being the axis of the straight tube (1). The total center of gravity of the cast iron cast into the core (18) and the socket (2) is the axis of the straight pipe (1) while being loaded with a required angle (θ) tilted with respect to the center (o). A method for manufacturing an angled straight pipe in which a core (18) is provided with a counterweight (30) so as to approach (o). It consists of a straight pipe portion (1), a socket portion (2) at one end thereof, and an insertion portion (3) at the other end thereof, and the outer surface of the socket portion (2) is the straight pipe portion (1). and the inner surface of the socket (2) is inclined at a required angle (θ) with the axis (o) of the straight pipe (1). A method for manufacturing a straight pipe (P) by centrifugal casting,
The finishing margin (b3) of the cast portion of the socket (2) is set to the center axis ( o) A method of manufacturing an angled straight pipe provided so as to approach. It consists of a straight pipe portion (1), a socket portion (2) at one end thereof, and an insertion portion (3) at the other end thereof, and the outer surface of the socket portion (2) is the straight pipe portion (1). and the inner surface of the socket (2) is inclined at a required angle (θ) with the axis (o) of the straight pipe (1). A method for manufacturing a straight pipe (P) by centrifugal casting,
A core (18) having an outer peripheral surface along the inner surface of the socket (2) is inserted into the socket (2) with the axis (c) of the core (18) being the axis of the straight tube (1). It is loaded at a required angle (θ) with respect to the center (o), and the total center of gravity of the core (18) and socket (2) approaches the central axis (o) of the straight pipe (1). A method for manufacturing an angled straight pipe in which a counterweight (30) is provided in a centrifugal casting mold (11).

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