The present invention is directed to recorder/reproducer apparatus and method embodying a unique magnetic signal transducer for storing information in a magnetic storage medium and retrieving the information stored therein. Further, the present invention is directed to a new type of scanning transducer which is capable of recording in and reproducing from magnetic media designed for vertical and/or horizontal recording.
During the recording of time varying information on a storage medium, the medium and the transducer are moved relative to one another. This relative motion is effected in various ways leading to a number of different recording formats. In one format, a storage medium such as a magnetic tape is transported past the transducer in the longitudinal direction of the tape. In this format, the information is recorded in the tape in a track which is coextensive with the length of the tape.
In an effort to increase the frequencies of information recorded in the tape, it has been known to move the transducer mechanically at an increased speed relative to the tape, to thereby scan the position of the transducer across the width of the tape. In such apparatus, the transducer is moved across the tape in a direction at a slight angle relative to the longitudinal direction in which the tape is transported. For example, in typical transducing arrangements the transducer is mounted on a drum that rotates about an axis generally parallel to the direction of tape transport. As a result of this movement, the transducer defines a track which is substantially perpendicular to the longitudinal dimension of the tape. Repeated scanning of the transducer in this manner, coupled with the transport of the tape in its longitudinal direction, produces discrete parallel tracks that extend across the width of the tape and are successively spaced along the length of the tape. In devices recording information in this mechanically scanning fashion, the width of the transducer and of the respective gap which produces a magnetic field to effect the recording of information, is much less than the width of the tape, whereby the unit pressure of each individual head on the tape is relatively high and promotes undesirable wear on the head and storage medium.
In another type of mechanically scanning arrangement used for example, in data and video recording, the parallel tracks are oriented at a very shallow angle, e.g. 5.degree. to 15.degree., relative to the longitudinal edge of the tape. This track orientation is provided by wrapping the tape around a drum shaped tape guide in a helical manner. The transducer is mounted on the circumferential surface of the drum for rotation. The longitudinal movement of the tape along its helical path, coupled with high speed rotation of the transducer during recording, results in parallel tracks being formed in the tape at the shallow angle.
While the scanning of a transducer across the tape significantly increases the frequencies of the information which may be stored in a tape, it is not without its attendant limitations. In particular, prior mechanically scanning arrangements have generally required that the portion of the transducer containing electrical windings, which generate and/or intercept the information flux, be moveable. For example, in the arrangements described previously, the entire transducer is mounted on a rotating drum. As a result, rather complex and costly electrical connections are required to facilitate the movement of and electrical connection to the transducer and its associated windings.
In addition, since the transducer is moveable, it is necessary to locate the record and reproduce electronics some distance away from the transducer. Consequently, relatively long leads are required to connect the signal processing electronics to the signal winding of the transducer. The need to use long leads, coupled with the rather complex connectors for connecting these leads to the moveable winding, results in high frequency losses and hence signal degradation.
Another concern associated with mechanically scanned transducers is their limited life, which decreases their reliability in certain applications. As previously mentioned, in magnetic tape recorders the transducer is in physical contact with the tape and is subject to high unit pressure. Because of the contact and the high speed of relative movement between the transducer and the tape in a scanning type of operation, the transducer is subject to significant wear. As a result, a typical mechanically scanned head might have a useful operating life of 1000-2000 hours, after which it must be replaced. The need to change the head after this period of operation reduces its reliability for some applications. For example, in high speed data backup operations, it is desirable to have a backup recorder running continuously in an out-of-the-way location with the knowledge that it is reliably capturing all information sent to it. However, if the transducer must be replaced on a frequent basis its reliability in such an environment is reduced. In addition, the cost of operating the recorder in such a situation is significant because of the need for continual replacement of parts.
A further version of a mechanically scanned head, of a probe type, employs a rotary head assembly which includes a generally flat, circular disk with a plurality of individual main poles embedded in the periphery of the rotary disk. The main poles may be embedded within the circumference of the disk to extend approximately radially relative to the rotary disk's axis of rotation, or may be embedded within the outer rim of the disk with the main poles extending generally parallel to the disk's axis. In the first embodiment, the poles scan a straight track generally transverse to the length of a magnetic tape (the tape must be concave to match the circumference of the disk), while in the second embodiment the main poles describe successive arcuate tracks across the tape width. A second stationary pole provides support for the magnetic tape while urging the tape against the main poles in the rotary disk. The stationary pole includes a signal coil wrapped thereabout via which a data signal is applied to the head assembly for recording. Rotation of the disk causes the main poles to sweep successively across the tape and the stationary pole so that they function as the main pole of a typical probe head.
This version also experiences excessive head and tape wear since the tape is confined with pressure between the stationary and main poles whereby the individual heads contact the tape with the relatively high unit pressure of previous mention.
In an effort to eliminate the need for moving transducer elements, magnetically scanned transducers, also known as solid-state scanning transducers, have been developed. In these types of devices, the transducer remains stationary and the magnetic signal to be recorded onto or reproduced from the tape is scanned across the face of the transducer. For example, in many of these transducers, a portion of the core is magnetically saturated to prevent signal flux from flowing therein. As a result, the signal flux can flow in only a limited region of the core which is unsaturated. By varying the location of the saturated region, either electronically or magnetically, the signal flux is scanned across the transducer, and hence across a tape disposed adjacent to it.
While such magnetically scanned transducers have eliminated the need for physically moving individual transducers to achieve scanning, they have not yet achieved widespread use due to various practical considerations in their implementation. Accordingly, there is still a need for the reliable, low cost scanning transducers such as those of previous mention which employ mechanical movement of the individual lo transducer elements across the magnetic storage medium.
It is to be understood that the term "mechanically scanned" transducers as used herein is intended to identify the typical prior art transverse and helical scan recording/reproducing apparatus in common use at the present time. This is to distinguish such typical apparatus from the present invention which, although it uses a mechanically rotating drum to aid in the scanning technique, does not mechanically move an individual transducing head (or heads) to perform the actual scanning of a respective magnetic track in the tape. For example, in the invention, the dimension of a recorded track in the tape generally is determined by the stationary pole, not the moveable main pole. Ergo, the scanning action is, in essence, a function of an intersecting portion of the "non-mechanically scanning" stationary pole, as contrasted with the typical "mechanically scanning" prior art of previous discussion. Thus, the term "mechanically scanning" is used herein to facilitate the comparison between the "mechanically scanned" prior art and the "non-mechanically scanned" present invention.