Helical coil, method of producing same and helical antenna using same

A method of producing a helical coil, comprising:

• continuously die-cutting a member on a belt-shaped strip of electrically conductive metallic sheet, wherein said member comprises one of a plurality of substantially U-shaped and a plurality of substantially V-shaped branch portions;
• positioning open ends alternating inversely, and the branch portions being connected with each other in a W-shape;
• wherein connection to said electrically conductive metallic sheet is held only by a pair of linkage portions at opposite sides;
• forming a helical coil by curving the branch portions into turns of helical coil of said one of a plurality of substantially U-shaped and a plurality of substantially V-shaped members in a substantially circular arc toward an obverse side and a reverse side of the metallic sheet alternatively;
• forming a bobbin for connecting each turn of the turns of said helical coil by one of insert-injection molding and outsert-injection molding of an electrically nonconductive material on each individual turn of said helical coil formed of said belt-shaped strip of electrically conductive metallic sheet;
• and
• shearing off the linkage portions to the electrically conductive metallic sheet.

A method of producing a helical coil, comprising:

• continuously die-cutting a member on a belt-shaped strip of electrically conductive metallic sheet, wherein said member comprises one of a plurality of substantially U-shaped and a plurality of substantially V-shaped branch portions;
• positioning open ends alternating inversely, the branch portions being connected with each other in a W-shape wherein connection to said electrically conductive metallic sheet is held only by a pair of linkage portions at opposite sides;
• forming a helical coil by curving the branch portions into turns of helical coil of said one of a plurality of substantially U-shaped and a plurality of substantially V-shaped members in a substantially circular arc toward an obverse side and a reverse side of the metallic sheet alternatively;
• forming a cover for connecting each turn of the turns of helical coil and for enclosing an outer periphery thereof by one of insert-injection molding and outsert-injection molding of electrically nonconductive material on each individual turn of said helical coil formed of said belt-shaped strip of electrically conductive metallic sheet;
• and
• shearing off the linkage portions to the electrically conductive metallic sheet.

A helical antenna having a helical coil, said antenna comprising a plurality of branch portions made of a thin metallic sheet and having one of a substantially U-shape and a substantially V-shape, the branch portions being connected continuously so that their open ends alternate inversely;

• wherein the branch portions alternatively curve toward an obverse side and a reverse side of the metallic sheet to form each turn of said helical coil, the alternatively curved branch portions defining half-cylindrical portions of said helical coil, whereby said helical coil has a generally cylindrical configuration;
• said helical coil having a center axis;
• and
• said helical coil including a conductive feeding part extending from an end of said helical coil coaxial with said center axis.

A method of producing an antenna, comprising:

• continuously die-cutting a member on a belt-shaped strip of electrically conductive metallic sheet, wherein said member comprises one of a plurality of substantially U-shaped and a plurality of substantially V-shaped branch portions;
• positioning open ends alternating inversely, and the branch portions being connected with each other in a W-shape;
• wherein connection to said electrically conductive metallic sheet is held only by a pair of linkage portions at opposite sides;
• forming a helical coil by curving the branch portions into turns of helical coil of said one of a plurality of substantially U-shaped and a plurality of substantially V-shaped members in a substantially circular arc toward an obverse side and a reverse side of the metallic sheet alternatively;
• forming a bobbin for connecting each turn of the turns of said helical coil by one of insert-injection molding and outsert-injection molding of an electrically nonconductive material on each individual turn of said helical coil formed of said belt-shaped strip of electrically conductive metallic sheet;
• and
• shearing off the linkage portions to the electrically conductive metallic sheet.

A method of producing an antenna, comprising:

• continuously die-cutting a member on a belt-shaped strip of electrically conductive metallic sheet, wherein said member comprises one of a plurality of substantially U-shaped and a plurality of substantially V-shaped branch portions;
• positioning open ends alternating inversely, the branch portions being connected with each other in a W-shape wherein connection to said electrically conductive metallic sheet is held only by a pair of linkage portions at opposite sides;
• forming a helical coil by curving the branch portions into turns of helical coil of said one of a plurality of substantially U-shaped and a plurality of substantially V-shaped members in a substantially circular arc toward an obverse side and a reverse side of the metallic sheet alternatively;
• forming a cover for connecting each turn of the turns of helical coil and for enclosing an outer periphery thereof by one of insert-injection molding and outsert-injection molding of electrically nonconductive material on each individual turn of said helical coil formed of said belt-shaped strip of electrically conductive metallic sheet;
• and
• shearing off the linkage portions to the electrically conductive metallic sheet.

A method of producing an antenna, comprising:

• continuously die-cutting a member on a belt-shaped strip of electrically conductive metallic sheet, wherein said member comprises one of a plurality of substantially U-shaped and a plurality of substantially V-shaped branch portions;
• positioning open ends alternately inversely, and the branch portions being connected with each other in a W-shape;
• wherein connection to said electrically conductive metallic sheet is held only by a pair of linkage portions at opposite sides;
• forming a helical coil by curving the branch portions into turns of helical coil of said one of a plurality of substantially U-shaped and a plurality of substantially V-shaped members in a substantially circular arc toward an obverse side and a reverse side of the metallic sheet alternatively;
• forming into said helical coil during die-cutting of the member a conductive feeding part coaxial with a center axis of said helical coil;
• forming a bobbin for connecting each turn of the turns of said helical coil by one of insert-injection molding and outsert-injection molding of an electrically nonconductive material on each individual turn of said helical coil formed of said belt-shaped strip of electrically conductive metallic sheet, said bobbin being formed in an insulating part projecting in an axial direction of said helical coil with said conductive feeding part being exposed on an outer surface;
• and
• shearing off the linkage portions to the electrically conductive metallic sheet.

A method of producing an antenna, comprising:

• continuously die-cutting a member on a belt-shaped strip of electrically conductive metallic sheet, wherein said member comprises one of a plurality of substantially U-shaped and a plurality of substantially V-shaped branch portions;
• positioning open ends alternately inversely, the branch portions being connected with each other in a W-shape wherein connection to said electrically conductive metallic sheet is held only by a pair of linkage portions at opposite sides;
• forming a helical coil by curving the branch portions into turns of helical coil of said one of a plurality of substantially U-shaped and a plurality of substantially V-shaped members in a substantially circular arc toward an obverse side and a reverse side of the metallic sheet alternatively;
• forming into said helical coil during die-cutting of the member a conductive feeding part coaxial with a center axis of said helical coil;
• forming a cover for connecting each turn of the turns of helical coil and for enclosing an outer periphery thereof by one of insert-injection molding and outsert-injection molding of electrically nonconductive material on each individual turn of said helical coil formed of said belt-shaped strip of electrically conductive metallic sheet to define an insulating part extending in an axial direction of said helical coil with said feeding part being exposed on an outer surface;
• and
• shearing off the linkage portions to the electrically conductive metallic sheet.