Cassette tape recorder

Details Cassette tape recorder Cassette tape recorder

2000-08-30

2004-04-27

Hudspeth, David (Department: 2651)

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the record

Reexamination Certificate

active

06728058

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cassette tape recorders, such as video tape recorders and audio tape recorders, for recording signals on a magnetic tape wound on a pair of reels in a tape cassette or reproducing signals from the magnetic tape, and more particularly to a control system for moving the magnetic tape at a high speed and winding the tape on one of the reels.
2. Description of the Related Art
VTRs (video tape recorders) are conventionally settable in a fast-forward (FF) mode and rewinding (REW) mode. In these modes (hereinafter referred to as “high-speed winding mode”), the rotation of a capstan motor is delivered to the reel on the take-up side to transport the magnetic tape at a high speed. In recent years, a high-speed winding mode is realized in which the tape speed is 300 to 400 times the playback speed.
With reference to
FIG. 10
, provided in such a high-speed winding mode are an acceleration section R
1
, constant-speed section R
2
, deceleration section R
3
and low-speed section R
4
, as arranged from a position where the tape is started for a high-speed movement to the tape tail end. In the constant-speed section R
2
, the capstan motor rotates at a maximum speed, giving a maximum tape speed Vm. The tape is thereafter wound to a predetermined tape position Pb, whereupon the tape starts to decelerate. The tape speed then decreases to a predetermined value Ve, whereupon the tape is brought into a slow-speed movement and wound up to the winding end.
The tape position Pb for the transition from the constant-speed section R
2
to the deceleration section R
3
is detected by a known method of detecting the remaining amount of the tape (see, for example, JP-A No. 81389/1990). Stated more specifically with reference to
FIG. 11
, suppose the radius of a magnetic tape
17
wound on a supply reel
15
of a cassette
1
is Rs, the radius of the tape
17
wound on a take-up reel
16
is Rt, and the radius of each of the supply reel
15
and the take-up reel
16
is r. It is possible to calculate from these values the area of the tape
17
wound on the supply reel
15
, i.e., the area Ss between the circle with the radius r and the circle with the radius Rs, and the area of the tape
17
wound on the take-up reel
16
, i.e., the area St between the circle with the radius r and the circle with the radius Rt. Further the radii Rs, Rt of the tape
17
on the respective reels can be calculated from the speed V of the tape
17
and the rotational periods Ts, Tt of the reels. The reel radius r and the tape speed V are known values.
For example, in the case where the tape is transported from the supply reel
15
to the take-up reel
16
and assuming that the tape
17
has an entire length Q, the amount Lm of the tape
17
remaining on the supply reel
15
can be calculated from the following mathematical expression.
Lm=Q·Ss
/(
Ss+St
)
However, the thickness of magnetic tapes for use in tape cassettes for conventional VTRs involves variations (e.g., 17 &mgr;m to 20 &mgr;m) due to the tolerance and difference of manufacturer, consequently impairing the accuracy in measuring the amount of remaining tape. Even if the tape is wound on the reel on the supply side over the same area Ss, the actual length of the tape portion providing the area is short when the tape has a large thickness, or is large when the tape has a small thickness.
In the case where the tape moving at the constant speed is decelerated as seen in
FIG. 12
based on such inaccurate detection of the amount of remaining tape, there arises the problem that if the tape thickness is small, the actual deceleration starting position is shifted to a position Pb′ from the intended tape position Pb toward the supply side, with the result that the length of the tape to be wound up to the tail end by the low-speed movement increases to a value R
4
′ which is greater than the minimum length R
4
required, necessitating a longer period of time for winding up the tape to the trailing end.
Alternatively if the tape has a large thickness, the actual deceleration starting position is shifted to a position Pb″ from the contemplated tape position Pb toward the take-up side, with the result that the tape is wound up to its trailing end at a great speed Ve″ during deceleration before the movement at the low speed Ve. This entails the likelihood that the resulting impact will damage the tape.
Further in the constant-speed section, the capstan motor is out of speed control, rotating at the greatest possible speed, so that differences in the magnitude of the load involved at this time produce variations in the tape speed. For example, in the case where the tape is moved at a constant speed Vm′ which is less than the specified speed Vm as shown in FIG.
13
and if the tape is then brought into a decelerated movement at the predetermined tape position Pb, the low-speed section is subsequently reached earlier, with the result that the tape portion to be wound up by the low-speed movement has a length R
4
′ which is greater than the minimum length R
4
required, leading to the problem that the winding of the tape up to its trailing end requires a longer period of time.
The problems described above become more pronounced when the high-speed winding mode is realized at a tape speed at least 500 times the playback speed.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to shorten the time required for winding up a magnetic tape by giving specified speed variations to the tape in the high-speed winding mode even when the tape thickness varies from tape to tape.
The present invention provides a cassette tape recorder which comprises a tape transport mechanism for unwinding a magnetic tape from one of two reels (i.e., the reel on the supply side) and winding the tape on the other reel (on the take-up side), and a control circuit for controlling the operation of the tape transport mechanism. The control circuit comprises remainder detecting means for detecting the amount of the tape remaining unwound and extending to a tape trailing end, speed control means for controlling the speed of movement of the tape based on a tape position corresponding to the detected amount of the remaining tape to bring the tape into an accelerated movement, a constant-speed movement and a decelerated movement successively, and means for estimating the thickness of the tape. The speed control means comprises deceleration starting position adjusting means for altering the tape position where the deceleration of the tape is to be started, in accordance with the estimated thickness of the tape.
With the cassette tape recorder of the invention described above, the remainder detecting means calculates the amount of the remaining tape from the area Ss of a region positioned between and defined by the radially innermost circle of the tape as wound on the reel on the supply side and the radially outermost circle thereof, the area St of a region positioned between and defined by the radially innermost circle of the tape as wound on the reel on the take-up side and the radially outermost circle thereof and the overall length Q of the tape. The tape thickness estimating means calculates the thickness of the tape by dividing the combined area (Ss+St) of the tape wound on the two reels by the overall length Q of the tape. The deceleration starting position adjusting means alters the deceleration starting position toward a leading end of the tape when there is an increase in the estimated thickness of the tape.
For example, if the tape has a thickness greater than the standard value, the true amount of the remaining tape is less than the amount of the remaining tape detected by the remainder detecting means. The tape position (deceleration starting position) where the tape in the constant-speed movement is to be decelerated is therefore shifted toward the tape leading end, whereby the length of tape to be wound by the deceleration movement is adjusted

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