A device (10) is disclosed for bending hollow structural components (100), in particular pipes, having a mandrel shaft (40) for receiving a receiving element (20), wherein a row of at least two ball joints (30, 30′) connected with each other can be inserted into the receiving element (20) at its end, wherein the row of ball joints (30, 30′) is preferably lockable by a ball-and-socket joint (70) at an end located opposite the receiving element (20), wherein each ball joint (30, 30′) of the row is circumferentially enclosed by a shingle (50, 50′) and the ball-and-socket joint (70) is circumferentially enclosed by an end shingle (60) and the shingles (50, 60) overlap each other at least in portions.

A method and apparatus for bending a pipe to mitigate internal wrinkling, with particular benefit when bending a lined pipe upon spooling. Bending is performed continuously by advancing the pipe through a bending zone while an internal mandrel is held at the bending zone to resist wrinkling. In one variant, the mandrel comprises longitudinally-spaced pipe-engaging elements and a tensile link between the elements allows relative movement between the elements. A holdback connection on one of the elements applies hold-back force to that element to be transmitted to the other element via the tensile link. In another variant, the mandrel comprises an elongate pipe-engaging body with a hold-back connection at one end of the body. The body is flexible to bend with the pipe and is shaped to engage an inner surface of the pipe along most of the length of the body.

A method and apparatus for bending a pipe to mitigate internal wrinkling, with particular benefit when bending a lined pipe upon spooling. Bending is performed continuously by advancing the pipe through a bending zone while an internal mandrel is held at the bending zone to resist wrinkling. In one variant, the mandrel comprises longitudinally-spaced pipe-engaging elements and a tensile link between the elements allows relative movement between the elements. A holdback connection on one of the elements applies hold-back force to that element to be transmitted to the other element via the tensile link. In another variant, the mandrel comprises an elongate pipe-engaging body with a hold-back connection at one end of the body. The body is flexible to bend with the pipe and is shaped to engage an inner surface of the pipe along most of the length of the body.

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.

A variable-diameter full-support mandrel structure with a slider-type cross section for preventing a reverse rotation of a ratchet wheel includes a movable mandrel segment and a straight shank, and the movable mandrel segment and the straight shank are connected through a quick-disconnect universal joint. A rotating shaft of the movable mandrel segment is provided with a connecting rod mounting flange, a ratchet wheel, a reverse ratchet wheel, a bearing, and a limit clamp ring in sequence. An outer ring of the bearing is provided with a pawl mounting frame. The connecting rod mounting flange and the pawl mounting frame are respectively hinged to a long connecting rod and a short connecting rod, and the long connecting rod and the short connecting rod are hinged to slider components in an outer ring. The slider component has a Z-shaped structure composed of two layers of arc blocks.

A variable-diameter full-support mandrel structure with a slider-type cross section for preventing a reverse rotation of a ratchet wheel includes a movable mandrel segment and a straight shank, and the movable mandrel segment and the straight shank are connected through a quick-disconnect universal joint. A rotating shaft of the movable mandrel segment is provided with a connecting rod mounting flange, a ratchet wheel, a reverse ratchet wheel, a bearing, and a limit clamp ring in sequence. An outer ring of the bearing is provided with a pawl mounting frame. The connecting rod mounting flange and the pawl mounting frame are respectively hinged to a long connecting rod and a short connecting rod, and the long connecting rod and the short connecting rod are hinged to slider components in an outer ring. The slider component has a Z-shaped structure composed of two layers of arc blocks.

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 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.