Mandrel, bent tube, and method and apparatus for producing bent tube

Patent metadata

Field	Value
Publication number	US-11278947-B2
Application number	US-201816484531-A
Country	US
Kind code	B2
Filing date	Feb 20, 2018
Priority date	Feb 21, 2017
Publication date	Mar 22, 2022
Grant date	Mar 22, 2022

Abstract

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 (L1/L2) between a dimension L1 from the mandrel ball center 17 to the first position 19 and a dimension L2 from the mandrel ball center 17 to the second position 20 is in a range of 0.915 to 0.976.

First claim

The invention claimed is:

1. A mandrel comprising a shank, a connection mechanism being in a spherical contact with the shank so as to be rotatable in an arbitrary direction, and a mandrel ball supported in a two-dimensionally or three-dimensionally displaceable manner with respect to the shank by the connection mechanism; wherein:
in a cross-section orthogonal to an axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball,
the mandrel ball has a first position and a second position at which a first straight line that passes through a mandrel ball center meets an outer periphery of the mandrel ball, and
a ratio (L 1 /L 2 ) between a dimension L 1 from the mandrel ball center to the first position and a dimension L 2 from the mandrel ball center to the second position is in a range of 0.915 to 0.976.

2. The mandrel according to claim 1 , wherein, in the cross-section orthogonal to the axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball, the mandrel ball has a first region surrounded by a second straight line orthogonal to the first straight line and an outer periphery of the mandrel ball which includes the first position, and a second region surrounded by the second straight line and an outer periphery of the mandrel ball which includes the second position.

3. The mandrel according to claim 1 , wherein, in the cross-section orthogonal to the axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball, the outer periphery of the mandrel ball in the first region and the outer periphery of the mandrel ball in the second region are continuously connected.

4. The mandrel according to claim 2 , wherein, in the cross-section orthogonal to the axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball, a shape of the outer periphery of the mandrel ball in the second region is semicircular.

5. A method for producing a bent tube having a bending portion that is two-dimensionally bent by performing rotary draw bending on an original tube using:
a two-dimensionally rotatable bending die having a groove for guiding a portion corresponding to inside of bend of the original tube that is a straight tube;
a cramping die that presses an end portion at outside of bend of the original tube to thereby press an end portion at inside of bend of the original tube against the bending die, the cramping die being two-dimensionally rotatable together with the bending die;
a wiper that supports the portion corresponding to inside of bend of the original tube; and
a pressure die that presses a portion corresponding to outside of bend of the original tube to thereby press the portion corresponding to inside of bend of the original tube against the wiper;
wherein the rotary draw bending is performed by disposing a mandrel according to claim 1 inside the original tube in a manner such that the first position of the mandrel ball is located facing a portion corresponding to outermost of bend of the original tube and the second position of the mandrel ball is located facing a portion corresponding to innermost of bend of the original tube.

6. The method for producing a bent tube according to claim 5 , wherein the rotary draw bending is performed while applying a compressive force in an axial direction to the original tube.

7. An apparatus for producing a bent tube having a bending portion that is two-dimensionally bent by performing rotary draw bending on an original tube, comprising:
a two-dimensionally rotatable bending die having a groove for guiding a portion corresponding to inside of bend of the original tube that is a straight tube;
a cramping die that presses an end portion at outside of bend of the original tube to thereby press an end portion at inside of bend of the original tube against the bending die, the cramping die being two-dimensionally rotatable together with the bending die;
a wiper that supports the portion corresponding to inside of bend of the original tube; and
a pressure die that presses a portion corresponding to outside of bend of the original tube to thereby press the portion corresponding to inside of bend of the original tube against the wiper;
the apparatus further comprising a mandrel according to claim 1 that is to be disposed inside the original tube,
wherein the mandrel is disposed in a manner such that the first position of the mandrel ball is located facing a portion corresponding to outermost of bend of the straight tube, and the second position of the mandrel ball is located facing a portion corresponding to innermost of bend of the straight tube.

8. The apparatus for producing a bent tube according to claim 7 , comprising means for applying a compressive force in an axial direction to the original tube on which the rotary draw bending is being performed.

9. The mandrel according to claim 2 , wherein, in the cross-section orthogonal to the axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball, the outer periphery of the mandrel ball in the first region and the outer periphery of the mandrel ball in the second region are continuously connected.

10. The mandrel according to claim 3 , wherein, in the cross-section orthogonal to the axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball, a shape of the outer periphery of the mandrel ball in the second region is semicircular.

11. The mandrel according to claim 9 , wherein, in the cross-section orthogonal to the axial direction of the mandrel ball at a central position in the axial direction of the mandrel ball, a shape of the outer periphery of the mandrel ball in the second region is semicircular.

12. A method for producing a bent tube having a bending portion that is two-dimensionally bent by performing rotary draw bending on an original tube using:
a two-dimensionally rotatable bending die having a groove for guiding a portion corresponding to inside of bend of the original tube that is a straight tube;
a cramping die that presses an end portion at outside of bend of the original tube to thereby press an end portion at inside of bend of the original tube against the bending die, the cramping die being two-dimensionally rotatable together with the bending die;
a wiper that supports the portion corresponding to inside of bend of the original tube; and
a pressure die that presses a portion corresponding to outside of bend of the original tube to thereby press the portion corresponding to inside of bend of the original tube against the wiper;
wherein the rotary draw bending is performed by disposing a mandrel according to claim 2 inside the original tube in a manner such that the first position of the mandrel ball is located facing a portion corresponding to outermost of bend of the original tube and the second position of the mandrel ball is located facing a portion corresponding to innermost of bend of the original tube.

13. A method for producing a bent tube having a bending portion that is two-dimensionally bent by performing rotary draw bending on an original tube using:
a two-dimensionally rotatable bending die having a groove for guiding a portion corresponding to inside of bend of the original tube that is a straight tube;
a cramping die that presses an end portion at outside of bend of the original tube to thereby press an end portion at inside of bend of the original tube against the bending die, the cramping die being two-dimensionally rotatable together with the bending die;
a wiper that supports the portion corres

Assignees

• Nippon Steel Corp

Inventors

• Tamura Shohei
• Arita Hidehiro

Classifications

• B21D7/025 Primary

  and pulling or pushing the ends of the work · CPC title

• B21D9/03 Primary

  and built-up from loose elements, e.g. series of balls · CPC title

• F16L43/001

  made of metal · CPC title

• B21D9/05

  co-operating with forming members · CPC title

• B21D9/07 Primary

  with one or more swinging forming members engaging tube ends only · CPC title