JPS58115671A - Detector for remaining amount of tape - Google Patents

Abstract

PURPOSE:To detect the remaining amount of a tape automatically, by detecting the rotational frequency of a tape supply reel during optional period in a tape threading period. CONSTITUTION:Magnets are provided having S poles and N poles alternately at the reverse-surface circumferential edge part of the tape supply reel at equal intervals, and the tape supply reel rotates to pass the magnets alternately to generate a sine wave. A generating circuit 2 shapes the waveform of the sine wave outputted from a tape supply reel rotation detecting means 1 to obtain a pulse signal. A switch 52 and the swelling part 51a of a threading ring 51 constitute a tape supply reel rotation detection period detecting means 3 and the switch 52 is turned during optional period in the threading period. The output of the rotation detection signal generating circuit 2 and the output of a generating circuit 4 for a tape supply reel rotation detection period display signal are ANDed to count a detection signal outputted from an AND circuit 5, thereby finding the rotational frequency of the tape supply reel from the number of magnets of the detecting means 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a tape recorder in which a tape is pulled out from inside a cassette and loaded into a predetermined rotating head drum, and then signals are recorded and played back on the tape. The present invention relates to a device for detecting remaining amount of tape.

When recording with a video tape recorder (hereinafter abbreviated as VTR), if the tape is wound around the take-up sole of the cassette, the remaining amount of tape may not be accurately known, and the amount of remaining tape may be low relative to the recording time. Having to flip the cassette or record onto a new cassette during recording can cause interruptions in the recorded content, unexpected discontinuities in the recorded video, or unnecessarily leave unused parts on the tape. The problem arises that it is not economical to leave it behind. especially,
When recording a desired television program while the user is away, the user ends up loading the tape even though there is only a small amount of tape remaining, resulting in a situation where part of the desired content is missed.

The present invention was proposed to solve the above-mentioned problems, and is a tape recorder in which a tape is pulled out from inside a cassette and loaded onto a predetermined rotating head drum, and then signals are recorded and played back on the tape. An object of the present invention is to provide a tape remaining amount detection device that automatically detects the remaining amount of tape.

In a VTR, when the cassette is mounted on the reel stand by the cassette holder mechanism, the tape is pulled out from the cassette and wrapped around the rotating head (lambda). This is called tape threading. The period from the start to the end is called the tape threading period.The length of the tape pulled out from the cassette during this tape threading period is constant, L1 is the winding diameter of the tape on the tape supply reel, and r is the rotational speed of the tape supply reel. n, the tape pull-out length for a predetermined period during the tape threading period, l, recording (playback) of the tape.
Vo is the speed of the time, Vo is the cassette hub diameter, and the remaining time of the tape is the ratio of the remaining length of the T1 tape to the total length (%).
) is P, then l=2・π・r−n (π; pi) ・・・・・・(
+1L-t=x・(r2-D2)
=(2JT-L/vo...
...(3) P=L・1oo/Lollllll・
...Equation (4) holds true. Here, l,, Vo are constant, and t.

D and Lo are unique values determined by the type of tape. Therefore, if the number of rotations n of the tape supply reel during a predetermined period during the tape threading period is detected, (
The winding diameter r of the tape is determined by equation (1), the remaining length L of the tape is determined from equation (2), and the remaining time J of the tape is obtained from equations (3) and (4).

The ratio P of the remaining length of the tape to the total length is determined.

Based on the above principle, the present invention detects the number of rotations of the tape supply reel during a predetermined period during the tape threading period, and also detects the tape thickness and tape total length according to the type of cassette stored in the storage device. By inputting the tape type, the hub diameter of the cassette is retrieved, the remaining time of the tape or the ratio of the remaining length of the tape to the total length is calculated, and this is displayed by an appropriate means such as a light emitting diode.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a tape remaining amount detection device for a video tape recorder according to an embodiment of the present invention. Second
3 is a plan view of an embodiment of the tape supply reel rotation detection means in the same block diagram, and FIG. 3 is a plan view of an embodiment of the tape supply reel rotation detection period detection means in FIG. 1.

1 is a tape supply reel rotation detection means for detecting the rotation of the tape supply reel, and an embodiment thereof is shown in FIG. In the figure (a), 20 is a tape supply reel, and 22 is a magnet with S poles and N poles arranged alternately and at equal intervals on the periphery of the lower surface of the tape supply reel, as shown in figure (b). It is. 23 is a frequency generator that generates a sine wave when the tape supply reel 20 rotates and the S and N poles of the magnet 22 alternately pass through. 21 is a rotating shaft of the VTR. Reference numeral 2 denotes a tape supply reel rotation detection signal generation circuit which shapes the sine wave output from the tape supply reel rotation detection means 1 and extracts a pulse signal. Reference numeral 3 denotes a tape supply reel +PA-rotation detection period detection means that detects the start and end of the rotation detection period of the tape supply reel. FIG. 3 is a plan view of an embodiment of the tape supply reel rotation detection period detection means arranged in a tape threading mechanism of a VTR, and shows a state in which tape threading is completed.

30 is a cassette, 31 is a tape supply reel, 32 is a take-up reel, 33 is a tape, 34 is a rotating head drum, 35 is an audio head, 36 is a full erase head, 37 is a tape tension regulator, 38-
Reference numeral 43 designates an f-p guide, 44 a capstan, and 45 a disc-shaped base on which the rotary head drum 34, audio head 35, full-surface erasing head 36, etc. are mounted. 46
~48 is a return guide roller, 49 is a pitch roller,
50 is a leading guide, these are threading rings 51
Fixed on top.

A portion of the outer periphery of the threading ring 51 is provided with a projecting portion 51a concentric therewith. 52 is a switch whose tip roller part 52a is always urged in the direction of the threading ring 51 by a spring, and when the threading ring 51 rotates and its protruding portion 51a comes to the switch 52 position, The length of the overhanging portion 51a and the relative position of the overhanging portion 51a and the switch 52 are such that the switch 52 is turned on during a certain period during the threading period. It can be decided as if it were. Reference numeral 4 denotes a tape supply reel rotation detection period display signal generation circuit, which rises when the switch 52 of the tape supply reel rotation detection period detecting means 3 is turned on and falls when it is turned off, that is, the pulse width is set to the tape supply reel rotation detection period. Generates a pulse. 5 obtains a tape supply reel rotation detection signal within the tape supply reel rotation detection period by taking the AND of the output of the tape supply reel rotation detection signal generation circuit 2 and the output of the tape supply reel rotation detection period display signal generation circuit 4. It is an AND circuit. 6 is a magnet 220 of the tape supply reel rotation detection means 1 which is preset by counting the tape supply reel rotation detection signal outputted from the AND circuit 5 within the tape supply reel rotation detection period.
This is a tape supply reel rotation speed calculation circuit that calculates the rotation speed of the tape supply reel from the number of tape supply reels. 7 is a tape winding diameter calculation circuit which calculates the tape winding diameter from the tape supply reel rotational speed determined by the tape supply reel rotational speed calculation circuit 6 and the threading length of the tape during a preset tape supply reel rotation detection period. . Reference numeral 8 denotes a cassette type input means for manually inputting the type of cassette before the VTR user loads the cassette into the VTR, and is provided in the operation section of the VTR.

Reference numeral 9 denotes a cassette unique value storage device that stores unique values of the tape thickness, tape total length, and hub diameter of the cassette according to the type of cassette. Reference numeral 10 denotes a cassette unique value reading circuit which reads the unique value of the cassette from the cassette unique value storage device 9 by inputting the cassette type using the cassette type input means 8. Reference numeral 11 denotes a remaining tape length calculation circuit that calculates the remaining tape length from the tape winding diameter determined by the tape winding diameter calculation circuit 7, the tape thickness read by the cassette specific value reading circuit 10, and the hub diameter. 12 calculates the remaining tape length (tape remaining amount) from the remaining tape length calculated by the tape remaining length calculation circuit 11, the total tape length read by the cassette unique value reading circuit 1O, and the tape speed at the time of tape recording (playback) obtained in advance. This is a tape remaining amount calculation circuit that calculates the total length) or the remaining tape amount time. Reference numeral 13 denotes a tape remaining amount display circuit for displaying the tape remaining amount ratio or tape remaining amount time determined by the tape remaining amount calculating circuit 12 on the tape remaining amount display device 14. The remaining tape amount display device 14 may be a light emitting diode or the like, and may display the remaining amount of tape digitally or graphically.

As explained above, the present invention detects the number of rotations of a tape supply reel within a predetermined period of time during which tape threading is performed after loading a cassette into a tape recorder, and detects the rotation speed of the tape supply reel detected. The remaining tape amount (tape remaining time or tape remaining amount percentage) is calculated from the tape thickness, tape total length, hub diameter, etc. set according to the number and the cassette type input before loading the cassette. Since this is displayed, the remaining amount of tape can be accurately identified immediately after loading the cartridge into the tape recorder without running the tape.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a remaining tape amount detection device for a video tape recorder according to an embodiment of the present invention, and FIG. 2 is a block diagram of a remaining tape amount detection device for a video tape recorder shown in FIG. 1. FIG. 3 is a plan view of an embodiment of the tape supply reel rotation detection means in FIG. 1; FIG. 3 is a plan view of an embodiment of the tape supply reel rotation detection period detection means in FIG. 1.2... Tape supply reel rotation detection means, 3.
4... Tape supply reel rotation detection period detection means, 5... Gate circuit 6... Tape supply reel rotation speed detection means, 7.
...first calculation means, 8.. cassette type input means, 9.. cassette unique value storage device, lO.. cassette unique value reading circuit, 11.. second.
Calculating means, 12...Tape remaining amount calculation circuit, 13...Tape remaining amount display circuit, 14...Tape remaining amount display device. Agent for patent applicant ShinNippon Electric Co., Ltd.

Claims (1)

[Scope of Claims] In a tape recorder in which a tape is pulled out from the inside of a cassette and loaded onto a predetermined rotating head drum, signals are recorded and played back on the tape. a tape threading mechanism that operates so that the length l of the tape drawn out during the tape threading period is always constant; a detection means that detects the number of rotations n of the supply reel inside the cassette during the tape threading period; a first calculation means that calculates the radius r of the tape wound on the supply reel according to the formula A/2πn (π is pi) according to the radius r given by the first calculation means; Then, the length L of the tape wound on the supply reel is calculated from the formula π(r2-D2)/l (where D is the reel diameter and t is the tape thickness).
A tape remaining amount detection device comprising calculation means.