Bobbin holding structure

A bobbin holding mechanism for detachably mounting a bobbin in a bobbin case holder including a bottom of ferromagnetic material and having an open end, said mechanism comprising:

• a body member in the form of a bar to be mounted at the open end of the bobbin case holder and having opposite ends, at least one of said ends having therein a slot for receiving the open end of the bobbin case holder such that said body member when mounted will extend in a direction of a diameter of the bobbin case holder;
• a shaft extending perpendicularly from a center of said body member in an axial direction of the bobbin case holder when said body member is mounted thereon, said shaft having a tip end positioned adjacent the bottom of the bobbin case holder when said body member is mounted thereon;
• an attraction member located at said tip end of said shaft and formed of magnetic material;
• whereby when a bobbin is mounted in the bobbin case holder, said shaft is passed through a center opening of the bobbin, said body member is positioned at the open end of the bobbin case holder, and magnetic attraction between said attraction member and the bottom of the bobbin case holder retains said body member in position and the bobbin within the bobbin case holder;
• a bobbin thread tensioner spring having a base end mounted on said body member and a free end elastically abutting said body member, said free end having therein a thread guide slot through which passes a bobbin thread when a bobbin in mounted in the bobbin case holder;
• and
• an adjusting screw member extending through said tensioner spring for moving said tensioner spring relative to said body member and thereby adjusting the tension applied to a bobbin thread passing through said thread guide slot.