Importance

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Abstract

A hysteresis tensioning device 10 incorporates an improved apparatus for setting and maintaining an air gap 48 between a hysteresis ring 32 and a magnet 36. The hysteresis ring operates in a fully saturated magnetic force field, and is thus amenable for tension control in environments subject to wide temperature variations. To the extent that magnetic tape recording is involved, the apparatus incorporates the use of magnets which are structured for being fixed relative to magnetic tape heads associated therewith, whereby any associated flux leaks are of the direct current type only. In a preferred embodiment, the device includes a pulley assembly 12 rotatably mounted on a bearing 20 having an inner race 22 supported on an axially disposed pulley shaft 16. The assembly includes a hysteresis ring 32 bonded to one side of a pulley sheave 18, the ring being axially spaced with respect to a magnet 36, whereby an air gap 48 is defined therebetween. The magnet is part of a magnet assembly 14 which, in turn, includes an axially extending member 40 supported on the shaft, and spaced by shims 46 from a radial surface 44 of the aforementioned inner race. The shaft includes an axial bore 50 and the magnet assembly includes a coupling member 52 cooperating with the bore for securing the axially extending member against the shims, wheeby the air gap may be accurately set and maintained.

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First Claim