JPS58115672A - Detector for remaining amount of tape - Google Patents

Abstract

PURPOSE:To detect the remaining amount of a tape automatically, by detecting the angular velocity of a tape supply reel. CONSTITUTION:Magnets are provided having S and N poles alternately at the reverse-surface circumferential edge part of the tape supply reel at equal intervals, and as the tape supply reel rotates, the S and N poles of the magnets are passed alternately to generate a sine wave; and the side wave outputted from a tape supply reel rotation detecting means 1 is waveform-shaped by a generating circuit for a tape supply reel rotation detection signal to obtain a pulse signal. A switch 52 and the swelling part 51a of a threading ring 51 constitute a detecting means 3 for a supply reel rotation detection period and the switch 52 is turned on during a constant tape drawing-out speed period in a threading period. The output of the generating circuit 1 and the output of a generating circuit 4 for a display signal for the tape supply reel rotation detection period are ANDed by an AND circuit 5, whose output detection signal in the detection period is counted to find the angular velocity 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 on the take-up reel of a cassette, the remaining amount of tape may not be known accurately, and the remaining amount of tape may not be sufficient for the recording time. During the process, the cassette must be reversed or recorded onto a new cassette, causing the recorded content to be interrupted, unexpected discontinuities in the recorded video, or unnecessarily leaving unused portions on the tape. The problem arises that it is not economical. Particularly, 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 unloading device that automatically detects the remaining amount of tape.

In a VTR, the cassette holder mechanism starts winding the tape around the tape. This is called tape threading, and the period from the start to the end of this tape threading is called the tape threading period. During this tape threading period The length of the tape pulled out from the cassette during this period is constant, and the tape pulling speed during this period is also the same as when the drive motor of the tape threading mechanism that performs tape threading changes from a stopped state to a steady state, and from a steady state to a stopped state. and is constant except for a very short period at the end.Now, let the thickness of the tape be t, the total length of the tape be , the remaining length of the tape, and the tape supply leap withdrawal speed at that time be t, the tape ■ Speed of recording (playback).

, the hub diameter of the cassette, the remaining time of the tape as T, and the ratio of the remaining length of the tape to the total length (IJI) as P, then V=r・ω
・・・・・・(1)(,-t=-rc・(r”=
D2) (π: pi) −・−・+2+T−2L/v
o...(3) p=L-100/Lo...
-Equation (4) holds true. Here, V and Vo are constant, t
.

D and Lo are unique values determined by the type of tape. Therefore, by detecting the angular velocity ω of the tape supply reel, the winding diameter r of the tape can be determined from equation (1), and the remaining length of the tape can be calculated from equation (2) using equations (3) and (
4) From the equations, the remaining time T of the tape and the ratio P of the remaining length of the tape to the total length are determined.

Based on the above principle, the present invention detects the f angular speed of the tape supply reel during a predetermined period when the tape speed is constant during tape threading, and also detects the f angular velocity of the tape supply reel according to the type of cassette stored in the storage device. By inputting the corresponding tape thickness, tape total length, and cassette nozzle diameter, the tape type is extracted, 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 used as appropriate for light emitting diodes, etc. It is displayed by means.

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
This figure 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.

Reference numeral 1 denotes 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 Figure 81, 20 is the tape supply reel, and 22 is the tape supply reel. As shown in Figure b1, S and N poles are arranged alternately and at equal intervals on the periphery of the bottom surface of the tape supply reel. 7 magnet. 23 is a frequency generator that generates a sine wave by rotating the tape supply reel 20 and passing the S and N poles of the fuse net 22 at intersections tj. 21 is the rotation axis of the VTR. 2 is 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. 3 is a tape supply reel rotation detection period detection means, which The start and end of the supply reel rotation detection period are detected. FIG. 3 shows an embodiment of this tape supply reel rotation detection period detection means.
This is a plan view when installed in the tape threading mechanism of R, and the figure shows a state in which tape threading has been 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
43 is a tape guide, 44 is a capstan, and 45 is a disk-shaped stand on which the rotary head drum 34, audio head 35, full erase head 36, etc. are mounted.

46 to 48 are return guide rollers, 49 is a pinch roller, and 50 is a leading guide, which are fixed on a threading ring 51. A portion of the outer periphery of the threading ring 51 is provided with a projecting portion 51a concentric therewith. Reference numeral 52 denotes a switch, whose tip roller portion 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 position of the switch 52, its outer periphery It is turned on when pressed by the unit. That is, the switch 52 and the overhanging part 51a of the threading ring 51 constitute the supply reel rotation detection period detection means 3, and the length of the overhanging part 51a and the relative position of the overhanging part 51a and the switch 52 are determined during the threading period. It is determined that the switch 52 is turned on during a period in which the tape drawing speed is constant. 4
is 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 detection means 3 is turned on, and when turned off) γ
In other words, a pulse whose pulse width is the period during which the rotation of the tape reel is detected is generated.

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 counts the tape supply reel rotation detection signal outputted from the AND circuit 5 during the tape supply reel rotation detection period, and detects the predetermined tape supply reel rotation detection period and the magnet of the tape supply reel rotation detection means 1. This is a tape supply reel angular velocity calculation circuit that calculates the angular velocity of the tape supply reel from the number of tape supply reels. Reference numeral 7 denotes a tape winding diameter calculation circuit that calculates the tape winding diameter from the angular velocity of the tape supply reel found by the tape supply reel angular velocity calculation circuit 6 and the tape speed obtained in advance. Reference numeral 8 denotes a cassette type input means for inputting the type of cassette by the VTR user before loading the cassette into the VTR, and is provided in the operation section of the VTR. 9 is the tape thickness of the cassette, the total length of the tape,
This is a cassette eigenvalue storage waveform that stores the eigenvalue of the hub diameter 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 wave W19 by inputting the cassette type using the cassette type input means l. 11 is a tape winding diameter calculated by the tape winding diameter calculating circuit 7 and a cassette specific calculating circuit. Reference numeral 12 indicates the remaining tape length calculated by the remaining tape length calculating circuit 11, the total tape length read by the cassette specific value reading circuit 10, and the recording (playback) of the tape obtained in advance.
This is a tape remaining amount calculating circuit that calculates the remaining tape amount ratio (relative to the total length of the tape) or the remaining tape amount time from the tape speed at the 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 to display the remaining amount of tape digitally or graphically.

As explained above, the present invention detects the angular velocity of the tape supply reel within a predetermined period during which tape threading is performed after loading a cassette into a tape recorder, and Before loading a cassette and the angular velocity of the supply reel, the remaining tape amount (tape remaining time or tape remaining percentage) is determined based on the tape thickness, tape total length, hub diameter, etc. set according to the input cassette type. ) is calculated and displayed, so the remaining amount of tape can be accurately identified immediately after loading the cassette into the tape recorder without running the tape.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a remaining tape amount detecting 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 detecting device for a video tape recorder shown in FIG. FIG. 3 is a plan view of an embodiment of the tape supply reel rotation detection means in FIG. 1. FIG. ■... Tape supply reel rotation detection means, 2...
Signal generation means, 3.4... Tape supply reel rotation detection period detection means, 5... Gate means, 6... First calculation means, 7... Second calculation means, 8... Cassette type. Input means, 9... Cassette specific value storage device, 10... Cassette specific value reading circuit, 11... Third
Calculating means, 12...Tape remaining amount calculation circuit, 13...Tape remaining amount display circuit, 14...Tape remaining amount display device.

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 tape withdrawal speed V is always constant during a tape threading period; a detection means for detecting rotation of a supply reel inside the cassette; signal generating means for outputting a detection signal corresponding to the rotational frequency of the supply reel; gate means, associated with the threading mechanism, for extracting the detection signal only during the tape threading period; a first calculation means for calculating an angular velocity ω of the supply reel in accordance with the detection signal; and a radius [
according to the radius r given by the second calculation means,
The length L of the tape wound on the supply reel is rc(
r2-D2)/t (π is pi, D is the hub diameter of the reel, and t is the tape thickness).