JPH0236328B2 - ERUBOSEIKEIYONAKAGO - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention prevents the reduction and flattening of the cross-sectional area of the pipe that occurs at the elbow when straight pipe material is bent into an elbow, and also prevents the inner peripheral surface from becoming flattened. This invention relates to a core for elbow molding to maintain smoothness.

(Prior art) When bending a straight pipe into an elbow, if the relationship between the bending radius R of the elbow and the outside diameter D of the straight pipe is R<1.5D (see Fig. 6), In a cross section perpendicular to the axis of the elbow portion, molding defects such as a reduction in the internal cross-sectional area of the tube, flattening, or V-shaped bending occur. Various cores are used to prevent these molding defects. For example, called a bead-shaped core, a plurality of ellipsoids or spherical bodies with a crescent-shaped cross section are connected with beads with holes in the center, and the cores are inserted into the elbow forming part of a straight pipe material and bent. ing.

(Problems to be Solved by the Invention) In the conventional bead-shaped core, since the core does not continuously contact the inner wall of the elbow portion during bending, unevenness occurs in the elbow portion, resulting in a smooth inner periphery. It was difficult to maintain the appearance.

(Means for Solving the Problems) The present invention provides an elbow forming core that is used to maintain a smooth inner peripheral surface at the elbow portion and prevent deformation when bending a straight pipe material into an elbow. The structure is as follows.

This is an elbow forming core that is inserted into a straight pipe material when an elbow part is formed in the straight pipe material, and is made of a low melting point material, is located on the outside of the elbow part in the radial direction, and has an outer arcuate surface. A sacrificial plate in contact with the inner peripheral surface of the elbow part, and a sacrificial plate located inside the elbow part in the radial direction,
The sacrificial plate is arranged integrally in the longitudinal direction, and the width in the longitudinal direction forms an inclined surface that is thinner on the inner side than on the outer side in the radial direction, and the inner circular arc surface is on the inner circumferential surface of the elbow part. This is an elbow molding core comprising a plurality of core segments that are in contact with each other.

(Function) Insert the above elbow molding core into the straight pipe material,
If a straight pipe material is bent with the sacrificial plate as the outside of the bending radius, the outer arcuate surface of the sacrificial plate will contact the inner peripheral surface outside the bending radius of the elbow, and the inner peripheral surfaces of the sacrificial plate will be in contact with the inner peripheral surface outside the bending radius. The inner arcuate surfaces of each core segment whose surfaces abut are brought into contact and the straight pipe material is formed into an elbow. After the bending process is completed, heating is performed to melt only the sacrificial plate, and the core segments are taken out.

(Example) An example of the elbow molding core according to the present invention will be described based on the drawings.

FIG. 1 shows one linear core 1, and one end of the core 1 is provided with a locking portion 1a. The locking portion 1a consists of opposing circular arcuate surfaces 1c, 1c' and opposing parallel side surfaces 1d, 1d, and has a through hole 1f at the center and a screw hole 1g at the end. Also,
A fitting portion 1b is provided connected to the locking portion 1a. The fitting portion 1b has a top portion formed into an arcuate surface 1c having the same shape as the locking portion 1a, and opposing parallel side surfaces 1d',
1d', and a longer fitting piece 1e is provided in a convex shape on the base opposite to the arcuate surface 1c.

Then, an end surface of a sacrificial plate 4, which will be described later, is locked with an inner surface 1a' of the locking part 1a that protrudes from the fitting part 1b, and a fitting piece 1e of the fitting part 1b is inserted into the fitting groove of the sacrificial plate. Fits into 4e'.

FIG. 2 shows the core segment 2 located radially inside the elbow. A plurality of the segments 2 are connected to the end face of the fitting part 1b of one of the straight part cores, and are positioned at a position where the straight pipe material is bent into an elbow part. Its cross-sectional shape is made to match the cross-sectional shape of the fitting portion 1b of one of the linear cores.
In other words, 2c is the inner arc surface which is the top, and both 2c
d' are opposing parallel sides, and 2e is a fitting piece at the base. The front and rear surfaces in the longitudinal direction of the sacrificial plate 4 are wedge-shaped inclined surfaces 2h' and 2 connected to the parallel surfaces 2h and 2h and whose width decreases toward the circular arc surface 2c.
h' is formed. The angle α between the two inclined surfaces 2h' and 2h' is determined by the bending radius R of the elbow portion. Further, a through hole 2f connected to the through hole 1f is provided.

FIG. 3 shows the other straight part core 3. The cross-sectional shape of the core 3 is the fitting part 1b of one linear core.
The cross-sectional shape is made to match that of . That is, 3c is the circular arc surface at the top, both 3d' are opposing parallel sides, and 3e
is a fitting piece at the base, and 3f is a through hole.

FIG. 4 shows a sacrificial plate 4 made of a low melting point material such as an aluminum alloy and located radially outward of the elbow portion. The outer arcuate surface 4c' is formed in the same shape as the arcuate surface 1c' of one of the linear cores, and
Connected to c′ and slightly opposing parallel sides 4d′, 4
d', a fitting groove 4e' for receiving the fitting pieces 1e, 3e of both linear cores, and the fitting piece 2e of the core segment is provided. And parallel sides 4d', 4
Parallel sides 1d', 1d' or 3d', 3d' are connected to d' and coincide with parallel sides 1d, 1d. Further, each of the arcuate surfaces 1c, 1c', 2c, 3c, and 4c' substantially coincides with the inner circumferential surface of the straight pipe material into which the elbow is to be formed.

The usage of the elbow molding core will be explained based on FIG.

In the fitting groove 4e' of the sacrificial plate, from the left side in the figure, a fitting piece 3e of the other straight part core, a fitting piece 2e of a series of core segments, and a fitting piece 1e of one straight part core are inserted. are fitted, and one end of the sacrificial plate 4 is locked to the inner surface 1a' of the locking part of one of the linear cores, so that the postures of each core segment 2 are made to match. Next, the wire 5 is inserted into each through hole 3f, 2 from the other straight part core 3 side.
f and 1f, one end is fixed to the end face of the other straight part core 3, and the other end is fixed to the end face of one straight part core 1 by tensioning the wire 5. As one means of fixing, as shown in the figure, the other end of the wire 5 is fixed to a clip 6a inserted through a through hole 6f provided in a bolt 6 screwed into a screw hole 1g provided in one of the straight cores. do. Thereafter, by screwing out the bolt 6 and tensioning the wire 5, one straight part core 1, a series of core segments 2, and the other straight part core 3 are integrally assembled to the sacrificial plate 4. Natsuto 6
The position of the bolt 6 is maintained by tightening the bolt 6 to the end face of one of the linear portion cores 1.

The elbow molding core assembled in this way is inserted into the straight pipe material A, and the sacrificial plate 4 is assembled as shown in FIG.
An elbow portion B is formed by cold bending a straight pipe material A as the radially outer side of the elbow portion to be formed. At this time, the plurality of core segments 2 whose inner arcuate surfaces 2c are in contact with the inner circumferential surface of the elbow portion bring the inclined surfaces 2h', 2h' into contact with each other, and the sacrificial plate 4 is easily curved. Each of the arcuate surfaces 1c, 2c, 3c, and 4c' is in contact with the inner circumferential surface of the pipe material, and the portions corresponding to the straight cores 1 and 3 maintain a straight pipe state, and a series of core segments The portion where 2 is located forms the elbow portion B. After the bending process is completed, only the sacrificial plate 4 is melted by heating uniformly to an appropriate temperature, and both straight cores 1 and 3 and a series of core segments 2 are taken out.

In addition, in the embodiment, the fitting pieces 1e, 2e,
3e are provided on one straight part core 1, core segment 2, and the other straight part core 3, respectively, and the fitting groove 4
e' are provided on the sacrificial plate 4, one straight part core 1, core segment 2 and the other straight part core 3.
Even if a fitting groove is provided in the sacrificial plate 4 and a fitting piece is provided in the sacrificial plate 4, the fitting state is the same. In addition, both straight part cores 1 and 3
Alternatively, grooves may be provided on both sides of each core segment 2 and the core segments 2 may be tightened with flexible connectors.

Furthermore, if straight tube portions are not required at both ends of the elbow, it is of course possible to omit both straight portion cores 1 and 3.

(Effects of the Invention) As understood from the above explanation, the present invention has the following effects.

When forming a straight pipe into an elbow, the outer arcuate surface of the sacrificial plate is brought into contact with the outer inner peripheral surface of the bending radius of the elbow, and the inclined surface is brought into contact with the inner peripheral surface of the sacrificial plate. Since the inner arcuate surfaces of the series of core segments are in contact with each other, it is possible to form an elbow in which the inner circumferential surface remains smooth without reducing or flattening the pipe cross-sectional area in the elbow portion.

[Brief explanation of drawings]

Fig. 1 shows one straight part core of the elbow molding core according to the present invention, A is a side view thereof, B is a front view thereof, C is a sectional view taken along the - line of Fig. , shows the same middle nine core segments, A is its side view, B is its front view, and FIG. 3 is the same other straight section core, A is its side view, B is its front view, Figure 4 shows the sacrificial plate, and A is its side view.
B is a front view thereof, FIG. 5 is a sectional view showing how the elbow molding core according to the present invention is used, and FIG. 6 is a
FIG. 2 is a sectional view after elbow molding using the elbow molding core according to the present invention. 1: One straight part core, 1c, 1c': Arc surface,
1e: Fitting piece, 1f: Through hole, 2: Middle core segment, 2c: Inner arc surface, 2e: Fitting piece, 2
f: Through hole, 2h': Inclined surface, 3: Other straight part core, 3c: Arc surface, 3e: Fitting piece, 3f: Through hole,
4: sacrificial plate, 4c': outer arcuate surface, 4e': fitting groove, 5: wire (flexible connector).

Claims (1)

[Claims] 1 An elbow forming core that is inserted into a straight pipe material when forming an elbow part in the straight pipe material, is made of a low melting point substance, is located on the outside of the elbow part in the radial direction, and has an outer arcuate surface. is arranged integrally in the longitudinal direction of the sacrificial plate, which is in contact with the inner circumferential surface of the elbow part, and is located inside the elbow part in the radial direction, and the width in the longitudinal direction is larger than that on the outside in the radial direction. What is claimed is: 1. A core for forming an elbow, comprising a plurality of core segments each having a thinner sloped surface on the inner side, and an inner arcuate surface in contact with the inner circumferential surface of the elbow portion.