One aspect of the present disclosure is a manufacturing device for a bent pipe. The manufacturing device includes an inner core metal placed inside a first pipe, and a tubular intermediate core metal placed between the first pipe and a second pipe. The intermediate core metal includes an intermediate core metal main body and a tubular first intermediate movable portion. The first intermediate movable portion is coupled to an end portion of the intermediate core metal main body, and swings about a first intermediate pivot axis relative to the intermediate core metal main body. The intermediate core metal main body includes an edge positioned closer to the first intermediate movable portion while the double pipe is bent. The edge intersects an imaginary plane orthogonal to a central axis of the second pipe at a position where the second pipe contacts the intermediate core metal.

One aspect of the present disclosure is a manufacturing device for a bent pipe. The manufacturing device includes an inner core metal placed inside a first pipe, and a tubular intermediate core metal placed between the first pipe and a second pipe. The intermediate core metal includes an intermediate core metal main body and a tubular first intermediate movable portion. The first intermediate movable portion is coupled to an end portion of the intermediate core metal main body, and swings about a first intermediate pivot axis relative to the intermediate core metal main body. The intermediate core metal main body includes an edge positioned closer to the first intermediate movable portion while the double pipe is bent. The edge intersects an imaginary plane orthogonal to a central axis of the second pipe at a position where the second pipe contacts the intermediate core metal.

A mandrel 10 for producing a thin-walled bent tube having a bending portion with high strength and a small radius of curvature by rotary draw bending without either cracks in an outside of bend or winkles and buckling in an inside of bend occurring includes a shank 14, a connection mechanism 15 and a mandrel ball 16. In a cross-section orthogonal to an axial direction of the mandrel ball 16 at a central position in the axial direction of the mandrel ball 16, the mandrel ball 16 has a first position 19 and a second position 20 at which a first straight line m that passes through a mandrel ball center 17 meets an outer periphery 21 of the mandrel ball. Further, a ratio (L.sub.1/L.sub.2) between a dimension L.sub.1 from the mandrel ball center 17 to the first position 19 and a dimension L.sub.2 from the mandrel ball center 17 to the second position 20 is in a range of 0.915 to 0.976.

A mandrel 10 for producing a thin-walled bent tube having a bending portion with high strength and a small radius of curvature by rotary draw bending without either cracks in an outside of bend or winkles and buckling in an inside of bend occurring includes a shank 14, a connection mechanism 15 and a mandrel ball 16. In a cross-section orthogonal to an axial direction of the mandrel ball 16 at a central position in the axial direction of the mandrel ball 16, the mandrel ball 16 has a first position 19 and a second position 20 at which a first straight line m that passes through a mandrel ball center 17 meets an outer periphery 21 of the mandrel ball. Further, a ratio (L.sub.1/L.sub.2) between a dimension L.sub.1 from the mandrel ball center 17 to the first position 19 and a dimension L.sub.2 from the mandrel ball center 17 to the second position 20 is in a range of 0.915 to 0.976.

One aspect of the present disclosure is a manufacturing device for a bent pipe. The manufacturing device includes an inner core metal placed inside a first pipe, and a tubular intermediate core metal placed between the first pipe and a second pipe. The intermediate core metal includes an intermediate core metal main body and a tubular first intermediate movable portion. The first intermediate movable portion is coupled to an end portion of the intermediate core metal main body, and swings about a first intermediate pivot axis relative to the intermediate core metal main body. The intermediate core metal main body includes an edge positioned closer to the first intermediate movable portion while the double pipe is bent. The edge intersects an imaginary plane orthogonal to a central axis of the second pipe at a position where the second pipe contacts the intermediate core metal.

One aspect of the present disclosure is a manufacturing device for a bent pipe. The manufacturing device includes an inner core metal placed inside a first pipe, and a tubular intermediate core metal placed between the first pipe and a second pipe. The intermediate core metal includes an intermediate core metal main body and a tubular first intermediate movable portion. The first intermediate movable portion is coupled to an end portion of the intermediate core metal main body, and swings about a first intermediate pivot axis relative to the intermediate core metal main body. The intermediate core metal main body includes an edge positioned closer to the first intermediate movable portion while the double pipe is bent. The edge intersects an imaginary plane orthogonal to a central axis of the second pipe at a position where the second pipe contacts the intermediate core metal.

One aspect of the present disclosure is a manufacturing device by which the bent pipe is obtained by bending a double pipe. The device includes inner and intermediate core metals, a bending mold, and a controller. The controller executes: a first bending process in which first and second pipes are bent by the bending mold in a first direction in a first area of the double pipe where the inner and intermediate core metals are placed; a second bending process in which the first and second pipes are bent, after the first bending process, by the bending mold in a second direction in a second area of the double pipe where the inner and intermediate core metals are placed; and a first bending-back process in which the second pipe is bent, after the first bending process, in a direction opposite to the first direction in the first area.

One aspect of the present disclosure is a manufacturing device by which the bent pipe is obtained by bending a double pipe. The device includes inner and intermediate core metals, a bending mold, and a controller. The controller executes: a first bending process in which first and second pipes are bent by the bending mold in a first direction in a first area of the double pipe where the inner and intermediate core metals are placed; a second bending process in which the first and second pipes are bent, after the first bending process, by the bending mold in a second direction in a second area of the double pipe where the inner and intermediate core metals are placed; and a first bending-back process in which the second pipe is bent, after the first bending process, in a direction opposite to the first direction in the first area.

Provided is a device for manufacturing a bent pipe, the device being capable of reducing buckling. The device including: an inner core metal arranged inside a first pipe; and a bending mold to bend the first pipe. The inner core metal includes: an inner core metal body; a first inner movable portion coupled to the inner core metal body and swingable around a first rocking shaft orthogonal to a central axis of the inner core metal body; and a second inner movable portion coupled to the first inner movable portion and swingable around a second rocking shaft parallel to the first rocking shaft. The first inner movable portion has an enlarging diameter portion enlarged in diameter toward the second inner movable portion. The bending mold causes an inner surface of the first pipe to press the first inner movable portion and the second inner movable portion.

Provided is a device for manufacturing a bent pipe, the device being capable of reducing buckling. The device including: an inner core metal arranged inside a first pipe; and a bending mold to bend the first pipe. The inner core metal includes: an inner core metal body; a first inner movable portion coupled to the inner core metal body and swingable around a first rocking shaft orthogonal to a central axis of the inner core metal body; and a second inner movable portion coupled to the first inner movable portion and swingable around a second rocking shaft parallel to the first rocking shaft. The first inner movable portion has an enlarging diameter portion enlarged in diameter toward the second inner movable portion. The bending mold causes an inner surface of the first pipe to press the first inner movable portion and the second inner movable portion.