Positioning mechanism for a floppy disk drive read/write head carriage

Claim 1

A positioning mechanism for a read/write head carriage of a recording/playback machine of the type utilizing a recording disk upon which information is magnetically stored, said positioning mechanism comprising, in combination: (a) a carriage adapted to carry a read/writehead, said carriage being made of a first material Ml and arranged for movement along a linear path within the machine to position the read/write head with respect to the recording disk; (b) a cylindrical capstan having a central axis and a prescribed circumference CC, said capstan being made of a second material M2, being arranged for rotation about said central axis, and being disposed adjacent said carriage with said central axis perpendicular to said path of movement of said carriage; (c) a flexible, non-stretchable band having opposite ends, said band being made of a third material M3 and being wound around said capstan and affixed thereto with its opposite end portions extending from said capstan substantially along a line which is tangent to said capstan and parallel to said path of movement of said carriage; (d) means for rigidly attaching the respective, opposite ends of said band to said carriage, thereby defining a linear carriage distance D and a total band length L between the points of attachment; said first, said second and said third material Ml, M 2, M 3 and said three dimensions CC, D and L being selected such that, upon a change in the temperature within the expected temperature range of operation of the machine, the temperature-dependent changes in the dimensions CC and D, when added together, are substantially equal to the temperature-dependent change in the dimension L.