A magnetic head drum includes an upper section that carries a set of magnetic heads and rotates at a preselected head speed, and a stationary lower section that is characterized by a reduced diameter step formed along the tape wrap path thereover (e.g., a helical path for a helical scan recorder). Because of the reduced diameter step, tape pressure is shifted from the lower drum section to the upper drum section which, by virtue of its rotation, produces a low friction air bearing. The reduction in diameter to produce the above-described step, moreover, results in a shoulder or ledge along the lower edge of the tape wrap path, which shoulder serves as a guide for the tape, and promotes accurate tape tracking over the drum. The amount of reduction in diameter for the lower drum section is not chosen arbitrarily, but is preferably within a range of 1 to 6 mils. In this range, a desirable balance is achieved between reduction in frictional drag and limiting of forces tending to distort the tape. Moreover, it appears that a reduction greater than around 6 mils tends to result in increased tape flutter.
This invention relates to a rotary head assembly in which a magnetic tape runs while being would helically, consisting of a fixed cylinder 21 having a fixed cylindrical part, and a rotatable rotary member 19 having a diameter approximately equal to that of said fixed cylinder 21, being disposed coaxially with a very small gap and holding a magnetic head 29, wherein pump-out type spiral grooves 20 are provided either partly or wholly on either plane of the confronting planes formed in the relative rotating part between said fixed cylinder 21 and said rotary member 19 in order to create a buoyancy on a running magnetic tape by air pressure not only in the rotary cylinder area but also in the fixed cylinder area, to realize a stable and smooth tape running, and to radically eliminate the tape chirping phenomenon, sticking phenomenon, and tape damage and cylinder wear accompanying sliding.
A tape recorder having a tape guide member with a guide edge against which the tape is loaded or biased by pressure members. To press the tape against the supporting edge with a transverse force approximately constant per unit of length, pressure members are arranged beyond the ends of the tape-supporting edge, and the tape supporting edge has a curvature convex toward the tape, with a peak substantially midway between tape-support entry and exit points having a smaller radius of curvature than that of the remainder of the tape-supporting edge.
