Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
1999-07-29
2001-04-03
Evans, Jefferson (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Head accessory
Reexamination Certificate
active
06212035
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to tape recording and playback apparatus, and relates more particularly but not exclusively to the intermittent cleaning of helical scanning drums utilised in tape recording and playback apparatus.
DESCRIPTION OF PRIOR ART
It is well known to utilise magnetic tape for recording and replaying high frequency signals that may represent (for example) video pictures or computer data (i.e., analogue data, digital data, or a mixture of analogue and digital data). Such magnetic tape is commonly held on and extends between two rotatable reels normally housed within a tape cassette. A form of electromagnetic transducer known as a tape head is utilised for writing signals onto magnetic tape (“write” operation) or for reading previously recorded signals (“read” operation). Both read and write operations require relative movement between the magnetic tape and the tape head, and the greater the bandwidth requirements (i.e. the greater the highest signal frequency to be dealt with), the greater must be such relative velocity. For directly recorded audio-frequency signals (e.g. music) it is sufficient for the tape head(s) to be stationary, and for the tape to be wound past the tape head(s) at a mechanically undemanding velocity. However, for writing and reading signals of a much higher frequency, e.g. video signals and computer data signals, it is known to mount one or several tape heads in the periphery of a drum which is rotated about a central axis that is skewed with respect to a notional perpendicular through the plane of tape movement such as to give the tape head(s) a component of movement transverse to the length of the tape (which passes along a path that extends around part of the periphery of the rotating drum), as well as giving the tape head(s) a component of movement along the tape. Such relative movement is known as “helical scanning” while the combination of tape head(s) and rotating drum is known as a “helical scanning drum”.
On the one hand, high-frequency data signals require a very high fidelity of writing and reading if interference and other errors are to be avoided, but on the other hand, the high velocity rubbing contact between tape and tape heads tends to result in the accumulation of scraped-off magnetic recording medium and/or other debris (e.g., airborne dust and dirt) on the tape heads. Such accumulations of debris degrade the performance of the tape heads, and must be avoided, or removed before worsening performance reaches an unacceptable level. Continuous cleaning of the periphery of a helical scanning drum is likely to cause excessive friction and wear, and/or to be ineffective if contact pressure of the cleaner on the drum is reduced in an attempt to avoid excessive friction and wear.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided tape recording and playback apparatus including a cleaning assembly having a cleaning means operable to clean the periphery of a helical scanning drum of said apparatus by contact therewith, the cleaning means being mounted for controllable movement into and out of contact with the periphery of the helical scanning drum, the assembly further comprising contact control means coupled to the cleaning means for controlling movement of the cleaning means into contact with the periphery of the helical scanning drum, the contact control means comprising a cam means including a cam-driving motor and a motor-driven cam, said cam means being operable to displace the cleaning means to make contact with the periphery of the helical scanning drum, said motor being a multi-function motor additionally utilisable for one or more of the additional functions of motor-driven loading of a tape cassette holding a length of magnetic tape, dragging a length of tape from the cassette into contact with the periphery of the helical scanning drum, and moving a pinch roller to pinch a portion of the tape against a tape-driving capstan forming part of the apparatus, such movements being effected by mechanisms coupled with the motor-driven cam, characterised in that said cam means is operable to displace the cleaning means independently of said additional functions.
Preferably said cam means is arranged to operate intermittently to cause the cleaning means to make intermittent contact with the periphery of the helical scanning drum.
The cleaning means may be mounted on movable mounting means comprising an arm or a bracket which is rotatable and/or slidable and which also comprises a cam follower co-operating with the cam means to be controllably moved thereby. The cam-driving motor is preferably a rotary electric motor having a rotatable output shaft, and the motor-driven cam is preferably a rotary cam directly connected to the rotatable output shaft of the cam-driving motor to be directly rotated thereby in use of the cleaning assembly.
The cleaning means is preferably an abrasive cleaning means operable to clean the periphery of the helical scanning drum by a combination of physical contact therewith and relative movement therebetween in use of the cleaning assembly. The abrasive cleaning means is preferably an abrasive wheel mounted for free rotation about a wheel axis in use of the cleaning assembly.
According to a second aspect of the present invention there is provided a method of operating apparatus according to the first aspect of the present invention, the method comprising the steps of controlling movement of the cleaning means into contact with the periphery of the helical scanning drum upon each occurrence of a selected one or more of the following conditions:
(a) upon the loading and/or unloading of a tape cassette;
(b) at substantially regular intervals of time;
(c) upon a data error being detected during a write cycle and/or during a read cycle;
(d) upon receipt of a manually originated command signal.
Preferably, movement of the cleaning means is such as to effect temporary or intermittent contact with the helical scanning drum.
REFERENCES:
patent: 5729398 (1998-03-01), Nouchi et al.
patent: 5745320 (1998-04-01), Ohshima et al.
patent: 5835317 (1998-11-01), Kawakami et al.
patent: 5949629 (1999-09-01), Suzuki et al.
patent: 6043949 (2000-03-01), Sakui
patent: 6069776 (2000-05-01), Hasegawa et al.
patent: 0 782 136 A1 (1997-07-01), None
Evans Jefferson
Hewlett--Packard Company
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