In an apparatus for recording and/or reproducing signals on a magnetic tape by means of at least one rotary head which extends into an annular gap between coaxial drum members for scanning oblique tracks on the tape while the latter is guided helically about the peripheral surfaces of the drum members, at least one of the drum members is rotated at a sufficient speed to produce an air bearing or cushion between the tape and the peripheral surface of each rotated drum member, and the peripheral surface of each rotated drum member is formed with one or more circumferential, endless grooves, each of which extends in a respective plane perpendicular to the axis of rotation and avoids the breakdown of the air bearing or cushion, for example, by reason of a crease, fold or other imperfection in the tape.
A tape guiding drum for a magnetic recording and reproducing apparatus including a rotary magnetic head, a lower drum having a cylindrical tape guide surface formed on the upper peripheral portion thereon, and an upper drum having a cylindrical tape guide surface on the lower peripheral portion thereof and disposed above the lower drum so as to leave a slit between the drums, the rotary magnetic head being provided within the slit and the tape being obliquely run around the drums, straddling the slit. At least one of the two drums has a notched portion along the side edge of the drum along the slit whereby a uniform reproducing output envelope can be obtained with the rotary head within the effective scanning zone of the rotary head.
A tape guide device of a rotary head type video tape recorder of the helical scanning system including a shoulder portion formed on an outer circumferential surface of a lower stationary cylindrical portion cooperating with an upper rotary cylindrical portion and constituting a head cylindrical drum for guiding a magnetic tape. The shoulder portion has, in a section thereof with which the magnetic tape is not brought into contact, a configuration consisting of a plurality of parabolic lines connected to one another. Alternatively, the offset portion may have a configuration consisting of curves which are such that their second differential coordinates are continuous over the entire circumference of the head cylindrical drum with respect to the fixed coordinate system disposed on the outer circumferential surface of the head cylindrical drum, or the shoulder portion may have a configuration consisting of curves which are such that the absolute value of the maximum value of the second differential coefficients is not equal to the absolute value of the minimum value thereof.
A device for the thermomagnetic recording of information on a highly coercive magnetizable recording medium. For this purpose is used, for example, a video recorder of the "helical scan" or "transversal scan" type whose drum has a co-rotating mirror and system of lenses with which an energy beam is directed and focussed on the recording medium at a small distance in front of the recording gap of the magnetic head. As a result of this the coercive force of the recording medium is locally reduced while using a very short heating time so that the medium can be recorded there by the head.
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.
Method and apparatus for producing a head drum for a video tape recorder and playback in which the head drum about which the tape passes is formed with a guide ledge so as to direct the tape past rotating magnetic heads and wherein the ledge is formed by cutting the surface of the head drums with a cutting tool and then providing a groove which undercuts the surface of the drum so as to form the ledge with a surface which is at right angles to the tangent of the tape engaging surface of the drum. By undercutting the surface of the drum to form the ledge assures that a radius will not be formed between the drum surface and the ledge, thus assuring accurate indexing of the lower edge of the video tape.
