Patent Application
20080185471
Tape cartridges or cassettes, such as DAT (digital audio tape), DSS (digital data storage by Sony Corporation), etc., have a hub around which the tape is wound as a spool of tape. Some other types of tape cartridges have flanges on the hub to guide each winding of the tape into alignment with a previous winding of the tape in the spool. The DAT and DSS cartridges, among others, however, have a flangeless hub. Not having flanges allows more tape to be wound into the spool because the space available for one fully packed spool overlaps the space available for the other. Thus, the cartridge can hold more information or data.
Without flanges, however, it is more difficult to guide each winding of the tape onto the previous winding as the tape is being wound by a tape drive mechanism, particularly if the drive mechanism doesn't control the positioning of the tape very well. In this case, there can possibly be too much movement of the tape, so the tape packs too high or too low in the spool.
It is important to align the windings of the tape to prevent the tape from slipping off the spool or being damaged by undue stretching or bending within the drive mechanism or the cassette. Otherwise, the cartridge can be rendered inoperable and/or the data contained therein lost. Additionally, if the tape is not properly aligned when being passed through the drive mechanism, then errors may occur in the writing or reading of the data, thereby reducing the efficiency or performance characteristics of the tape and the drive mechanism.
Such flangeless cartridges typically have guide sheets between the inner surfaces of the cassette housing and the spool of tape. These guide sheets assist in aligning the tape on the spool of tape as the tape is being wound. Sometimes rigid plastic ribs are formed in the inner surface of the cartridge housing to support the guide sheets close to the spool of tape.
The guide sheets are sometimes called friction sheets, because the guide sheets cause less friction against the tape edge than do the inner surfaces of the housing. The tape edge rubs against the guide sheets as the tape moves, thereby causing a friction force between the tape and guide sheets that retards movement of the tape. Motors within the tape drive mechanism must overcome the friction of the tape against the guide sheets in order to turn the spool of tape. If the motor has to pull harder on the tape, then tension on the tape will increase, possibly resulting in tape edge damage as the tape is pulled through the tape drive mechanism. Further increases in tape tension may exceed the ability of the motors to pull the tape.
There is a tradeoff between the tape alignment capability of the guide sheets and the amount of friction generated between the moving tape and the guide sheets. If the guide sheets are held closely to the tape by the inner surfaces, or rigid plastic ribs, of the housing, then the alignment of the tape will be desirably good, but the tape will be tightly constrained, thus the friction forces will be undesirably high. On the other hand, if the guide sheets are given a lot of room between the tape and the inner surfaces of the housing, then the tape will be less constrained, thus the friction forces will be desirably low, but the alignment of the tape will be undesirably poor.
An exemplary tape cassette, or cartridge, 100 is shown in
The bottom housing portions 106 and 108 attach together in such a manner that the retractable bottom housing portion 108 can slide relative to the primary bottom housing portion 106 from the position shown in
The guide sheets 112 and 114 are generally shaped to be able to cover the spool of tape, when the tape is wound around either of the flangeless hubs 116 and 118. Also, the guide sheets 112 and 114 have holes 124 and 126 corresponding to the placement of the flangeless hubs 116 and 118, respectively. The bottom guide sheet 114 sits on the primary bottom housing portion 106. A portion of the flangeless hubs 116 and 118 protrudes through the holes 124 and 126, respectively, of the bottom guide sheet 114, so the flangeless hubs 116 and 118 can be seated in circular retainers 128 and 130, respectively, in the primary bottom housing portion 106.
The top guide sheet 112 sits on the spool of tape. Another portion of the flangeless hubs 116 and 118 protrudes through the holes 124 and 126, respectively, of the top guide sheet 112, so the flangeless hubs 116 and 118 can also be seated in circular retainers 132 and 134 (
The hub-locking mechanism 120 attaches to the top housing portion 104 and the door panel 110. When the door panel 110 is in the closed position, the hub-locking mechanism 120 is held in a position at which it engages the flangeless hubs 116 and 118 to prevent the flangeless hubs 116 and 118 from rotating. When the door panel 110 is pivoted to the open position, the hub-locking mechanism 120 is moved to a position at which it does not engage the flangeless hubs 116 and 118, so the flangeless hubs 116 and 118 are free to rotate.
The tape is attached between the two flangeless hubs 116 and 118. When the tape cartridge 100 is inserted into a tape drive mechanism, the door panel 110 is pivoted up (arrow B) and the retractable bottom housing portion 108 is retracted (arrow A) to expose the tape and provide bottom access to the flangeless hubs. Also, the hub-locking mechanism 120 releases the flangeless hubs 116 and 118. The tape drive mechanism can then move the tape back and forth between the flangeless hubs 116 and 118 reeling the tape into the spool on one of the flangeless hubs 116 or 118 and off of the spool on the other flangeless hub 116 or 118.
The tape cartridge 100 is illustrated as a type referred to as DAT (digital audio tape) or DSS (digital data storage by Sony Corporation). However, the invention is not limited to such tape cartridges, but may be incorporated in any appropriate tape cartridge having flangeless spools of tape.
The flexible spacer 122, in the embodiment shown in
The flexible spacer 122 gently pushes against the top guide sheet 112 to flexibly bias the top guide sheet 112, the spools of tape 136 on the flangeless hubs 116 and 118 and the bottom guide sheet 114 toward the inner surface of the primary bottom housing portion 106. In this manner, the flexible spacer 122 gently forces each winding of the tape 136 into alignment with the previous winding, so proper packing of the spools of tape 136 is enhanced. Additionally, the relative flexibility of the flexible spacer 122 results in only a slight compression force, or soft compliant contact, on the spools of tape 136, instead of a large compression force that has been found to result from a relatively rigid spacer, or rib, pressing against the spools of tape 136. Thus, there is a partial, but insignificant, retarding of the winding action. Therefore, the flexible spacer 122 causes the tape windings to be aligned without causing too much friction force retarding the action of winding the spools of tape 136 around both flangeless hubs 116 and 118.
The proper alignment of the spools of tape 136 also reduces lateral tape motion as the tape exits the tape cartridge 100 into the tape drive mechanism. As a result, the tape drive mechanism can write and read data to and from the tape with better precision. Thus, there is a significant improvement in overall function, efficiency or performance of the tape and the drive mechanism due to a reduced number of re-writes or re-reads when writing data to the tape or reading data from the tape.
Alternative embodiments for the number and placement of the flexible spacers 122 are shown in
