Extendable arm and structure using the same

1. An extendable arm comprising:

a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

said rigid member has a linear shape in its central region in a longitudinal direction of said rigid member.

2. A three-dimensional object formed by using said extendable arm according to claim 1 , wherein

a three-dimensional shape that is formed by said extendable arm in a deployed state forms a surface selected from the group consisting of a cylindrical surface, a conical surface, and a spherical surface.

3. A three-dimensional object formed by using said extendable arm according to claim 1 , wherein

a three-dimensional shape that is formed by said extendable arm in a deployed state forms a shape selected from the group consisting of an arc shape, a helical shape, an arch shape, and a wave shape.

4. An extendable arm comprising:

a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point,

said coupling points at said both ends of said rigid member are shifted in a lateral direction of said rigid member, and

a curve that passes through said coupling points at said both ends and said central coupling point of said rigid member is curved with a uniform radius of curvature.

5. The extendable arm according to claim 4 , wherein

said rigid member has a shape that is curved with a uniform radius of curvature along its entire longitudinal length.

6. A three-dimensional object formed by using said extendable arm according to claim 4 , wherein

a three-dimensional shape that is formed by said extendable arm in a deployed state forms a surface selected from the group consisting of a cylindrical surface, a conical surface, and a spherical surface.

7. A three-dimensional object formed by using said extendable arm according to claim 4 , wherein

a three-dimensional shape that is formed by said extendable arm in a deployed state forms a shape selected from the group consisting of an arc shape, a helical shape, an arch shape, and a wave shape.

8. An extendable arm comprising:

a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

said coupling points at said both ends of said rigid member are shifted in a thickness direction of said rigid member and in a lateral direction of said rigid member.

9. The extendable arm according to claim 8 , wherein

said rigid member has a shape that is curved with a uniform radius of curvature along its entire longitudinal length.

10. A three-dimensional object formed by using said extendable arm according to claim 8 , wherein

a three-dimensional shape that is formed by said extendable arm in a deployed state forms a surface selected from the group consisting of a cylindrical surface, a conical surface, and a spherical surface.

11. A three-dimensional object formed by using said extendable arm according to claim 8 , wherein

a three-dimensional shape that is formed by said extendable arm in a deployed state forms a shape selected from the group consisting of an arc shape, a helical shape, an arch shape, and a wave shape.

12. A three-dimensional object, comprising:

a plurality of extendable arms each comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

a partition is formed by coupling said plurality of extendable arms in a lateral direction crossing a longitudinal direction.

13. A desk lamp, comprising: an extendable arm; a base member supporting a base end of said extendable arm; a lighting unit attached to a tip end of said extendable arm; and an electrical cord extending from said base member to said lighting unit, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point,

said extendable arm has clearance that allows said electrical cord extending from said base member to said lighting unit to extend therethrough,

said coupling points at said both ends of said rigid member are shifted in a thickness direction of said rigid member, and

said lighting unit emits light to the same position regardless of whether said extendable arm is in an extended state or in a contracted state.

14. A desk lamp, comprising: an extendable arm; and a lighting unit attached to a tip end of said extendable arm, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted in a lateral direction of said rigid member from a longitudinal axis passing through said central coupling point, and

a direction in which said lighting unit emits light is the same regardless of whether said extendable arm is in an extended state or in a contracted state.

15. An article holding device, comprising:

a bed;

an extendable arm that can be extended and contracted and that extends in a greatly curved shape from a side of said bed to a position above a face of a person lying on said bed when in an extended state; and

an article holding member attached to said extendable arm, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

a trajectory of an extension/contraction operation of said extendable arm forms a tilt angle with respect to a horizontal plane.

16. The article holding device according to claim 15 , wherein

said coupling points at said both ends of said rigid member are shifted in a thickness direction of said rigid member,

said article holding member holds a visual object, and

said visual object held by said article holding member provides a visual surface that faces toward said face of said person lying on said bed regardless of whether said extendable arm is in an extended state or in a contracted state.

17. The article holding device according to claim 15 , further comprising:

a base member, wherein

a base end of said extendable arm is rotatably supported by said base member.

18. An article holding device, comprising:

a bed;

an extendable arm that can be extended and contracted and that extends in a greatly curved shape from a side of said bed to a position above a face of a person lying on said bed when in an extended state; and

an article holding member attached to said extendable arm, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point,

a coupling structure of said extendable arm and said article holding member is configured so that an angle of said article holding member with respect to an extended direction of said curved-line path of said extendable arm changes according to an extension/contraction operation of said extendable arm,

one rigid member located at a tip end of said extendable arm is coupled at a fixed angle to said article holding member, and

said angle of said article holding member with respect to the extended direction of said curved-line path of said extendable arm changes according to an extension/contraction length of said extendable arm.

19. An article holding device, comprising:

an extendable arm that can be extended and contracted and that extends in a greatly curved shape when in an extended state; and

an article holder attached to said extendable arm, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point,

said coupling points at said both ends of said rigid member are shifted in a lateral direction of said rigid member, and

the number of at least one of said two rigid members is more than one.

20. The article holding device according to claim 19 , wherein

said coupling points at said both ends of said rigid member are shifted in said lateral direction of said rigid member and in a thickness direction of said rigid member.

21. A combination toy including a plurality of extendable arms, for playing by combining said plurality of extendable arms, each of said extendable arms comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, and each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point.

22. An extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising first and second rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

said first rigid member comprises a pair of rigid elements which are provided at an interval in a thickness direction, and said second rigid member is interposed between said pair of rigid elements of said first rigid member.

23. A three-dimensional object, comprising:

an extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape, wherein

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted in a thickness direction of said rigid member from a longitudinal axis passing through said central coupling point,

three axes in said thickness direction which pass through said central coupling point and said coupling points at said both ends of said rigid member converge on one point,

said rigid member has a semicircular shape in which an included angle between said both ends of said rigid member about said convergence point is 180 degrees, and

said extendable arm forms a sphere when in a deployed state.

24. A three-dimensional object, comprising:

a plurality of extendable arms comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

a cylindrical surface is formed by coupling said plurality of extendable arms in a lateral direction crossing a longitudinal direction.

25. A desk lamp, comprising: an extendable arm; and a lighting unit attached to a tip end of said extendable arm, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising first and second rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

said first rigid member comprises a pair of rigid elements which are provided at an interval in a thickness direction, and said second rigid member is interposed between said pair of rigid elements of said first rigid member.

26. A desk lamp, comprising: an extendable arm; and a lighting unit attached to a tip end of said extendable arm, wherein

said extendable arm comprising a plurality of cross units arranged in one direction and pivotally coupled to each other, each of said cross units comprising two rigid members that are pivotally coupled at a central coupling point so as to cross over each other to form an X-shape,

in order for said extendable arm to follow a curved-line path when being extended and contracted, each of said rigid members has such a curved shape that coupling points at both ends of said rigid member are shifted toward one side from a longitudinal axis passing through said central coupling point, and

said coupling points at said both ends of said rigid member are shifted in a thickness direction of said rigid member and in a lateral direction of said rigid member.