Adjustable-inductance electric coil

In an adjustable inductance electrical coil including:

• 1. a fixed core body formed of a magnetizable material and having an upper and a lower core portion, each core portion having a substantially double U-shaped cross-sectional configuration which includes an outer leg and a shorter inner leg extending from a wall thereof, a free end of each outer leg of one core portion abutting against a free end of a respective outer leg of the outer core portion so as to define a lateral passage within said core body, said core portions each having a circumferential space between said inner and outer legs thereof and an axial passage located between the respective inner legs of a core portion extending from a wall thereof to the free end of said inner legs thereof, said axial passage and circumferential space of a core portion being substantially aligned with the axial passage and circumferential space of the other core portion so as to define an aligned circumferential space and an aligned axial passage within said core body;
• 2. a winding means positioned within said aligned circumferential space of said core body so as to create an inductance in the core upon energization of said coil;
• and
• 3. means positioned within said aligned axial passage in said core body and extending across said lateral passage for adjusting the inductance of said coil;
• the improvement comprising wherein:
• a. an internally threaded sleeve formed of a non-magnetizable material having an elongated cylindrical body of a length less than the length of the axial passage in said upper core portion, said cylindrical body having a crowned closed upper end portion and an opposite open end portion providing access to the interior of said sleeve, said sleeve being positioned within said axial passage in said upper core portion so that a top of said crowned closed upper end portion is substantially aligned with a top surface of said upper core portion;
• b. a mastic means positioned on the outside of said sleeve between inner walls of said axial passage in said upper core portion, said crowned closed upper end portion of the sleeve and outside surface portions of said sleeve;
• and
• c. said means for adjusting the inductance of said coil consists essentially of:
• c.sub.1. a solid shaft formed of a non-magnetizable material having a body of a length less than the length of said aligned axial passage in said core body but greater than the length of the axial passage in said upper core portion so that said body extends from the lower core portion at least across the lateral passage in said core body, said shaft body being externally threaded at least along upper portions thereof and having a slotted tool-engageable head positioned at a select location within the axial passage in said lower core portion and having the body thereof threadedly engaged in said sleeve with an end portion of said shaft opposite the slotted head portion thereof being selectively spaced from an inner wall of said sleeve located interiorly of the crowned upper end portion thereof;
• and
• c.sub.2. a hollow elongated internally threaded cylindrically-shaped tube core formed of a magnetizable material having a length less than the length of the respective axial passages in said upper and lower core portions, said tube core being threadedly engaged on said shaft at a select location thereof above the slotted head portion thereof and below said sleeve;
• whereby rough inductance adjustment of the coil is attained by
• moving said tube core to a select location on said shaft and fine inductance adjustment of the coil is attained by moving said shaft to a select location within said sleeve.