DE2320264A1 - TAPE RECORDER AND / OR PLAYBACK DEVICE - Google Patents

Description

it 2472

SONY CORPORATION, Tokyo / Japan

Tape recorder and / or player

The invention relates generally to a tape recorder and / or playback device and in particular a device with two drums for tape guidance.

A tape recorder and / or player in which a fixed guide drum for guiding a magnetic tape around the rotating circular surface of a rotary head, such as a rotary magnetic head and for transporting the tape in a surface opposite to the circular inclined path is provided is known. Such a device has the disadvantage that when the tape runs around the guide drum due to the sliding friction,

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caused by this, the running resistance of the The band is increased and the band vibrates at a high frequency. Especially when the band is high frequency vibrates, occurs in a reproduced image recorded on the tape due to a video signal, a so-called tremor, which deteriorates the quality of the reproduced image.

In order to avoid this disadvantage, a construction as described in US Pat. No. 3,333,753 has been proposed is. In this construction, a guide drum is rotated at high speed to create an air gap. to form a layer of air between the outer circumference and a belt guided by the drum and thereby the sliding friction to diminish between these. In this construction, however, the outer surface of the guide drum is one smooth surface, so that if a fold, a kink or the like. occurs in the tape, the layer of air at the fold or the Kink is interrupted. This causes the space between the belt and the guide drum to become or near a vacuum a vacuum and disrupts the movement of the belt. As a result, the tape travel becomes abnormal and the tape can be wound onto the guide drum and cut.

In order to avoid such a disadvantage, the construction of U.S. Patents 3,534,893 and 3,614,338 has been proposed. at these constructions are grooves on the tape guide surface the tape guide drum moving at high speed rotates, parallel or oblique to the axis of rotation. Even if the air layer between the belt and the Guide drum is partially interrupted, the gap

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air may be supplied between the belt and the drum to prevent the formation of a vacuum and the above To eliminate disadvantage.

However, a problem other than the above may arise with these constructions. The grooves on the leader drum are formed intermittently collide with or grip the belt as the drum rotates at the point where the belt runs onto or leaves the drum. Therefore, a vibration or Vibration with a high repetition frequency occur in the belt when the guide drum rotates, so that a so-called Tremors may occur in the picture reproduced from a video signal obtained from one of the US Patents described device was recorded on a tape.

The invention is based on the object of a rotary drum assembly in which the undesirable vibration of a belt does not occur, even if the arrangement has a Has groove on the guide surface of their guide drum the one guide part for spiral guidance of the tape is provided and operating at a sufficiently high speed (of e.g. 30 cm / sec) compared to the tape transport speed (from e.g. 10 to 20 cm / sec) can be rotated.

This task is solved with a tape recording and / or playback device consisting of a tape guide drum which is rotatably attached to an axis, at least a rotary head for recording and / or playback

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a signal arranged coaxially with the tape guide drum is, a device for spiral guidance a tape around the circumference of the tape guide drum, and at least one groove on the circumferential surface of the tape guide drum, according to the invention in that the groove is in the substantially perpendicular to the axis of the guide drum Level lies.

The invention is explained below with reference to FIGS. 1 and 2, for example. It shows:

Figure 1 is a side view, partly in section, of one embodiment a magnetic head drum assembly according to the invention, and

Fig. 2 is an enlarged view of part of an on the Drum of the magnetic head drum assembly of Fig. 1 formed groove.

A head drum arrangement according to the invention will first be described with reference to FIG. 1, wherein 1 denotes a magnetic tape guide drum arrangement which is made, for example, of an aluminum alloy and to which magnetic heads Ha and Hb are attached for recording and / or reproducing a signal. The guide drum arrangement 1 consists of two guide drums 2 and 3 t which are arranged coaxially one above the other with a predetermined gap h between them and have the same outer diameter. The upper guide drum 2 is rotated clockwise as indicated by arrow a, while the lower guide drum 3 is attached to a base plate 12. The magnetic heads Ha and Hb are at an angular distance of about 180 ° in the

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Gap h between the two guide drums 2 and 3 is arranged so that they are directed from the drums 2 and 3 outwards. In the illustrated embodiment, the magnetic heads Ha and Hb are fixed so that they are rotated together with the rotary drum 2. For this purpose, the magnetic heads Ha and Hb are attached to the head holders 13 ^a and 13b, and these b attached to the underside 2a of the upper guide drum 2, for example by means of screws 14a and 1 ^. The angular distance (180 °) of the heads Ha and Hb and the distance they protrude from the tape guide surface of the drum 2 are set to a certain value by attaching position adjusting devices to the respective brackets 13a and 13b. The rotating or upper drum 2 is attached to a rotating shaft 5, which is supported by the fixed guide drum 3 and a base plate

7 for the drum is supported by bearings 6 and 6 '. The upper end of the rotary shaft 5 is thus on the bottom 2a of the upper drum 2 in its central bore by a nut 5a or the like. attached. A pulley 8 is at the lower end of the rotary shaft 5 and a belt pulley ^9a is mounted on the free end of the rotating shaft of a motor 9b. An endless, flexible belt 10, for example made of rubber or the like. extends between the pulleys

8 and 9a, so that when the motor 9 is driven, the rotating shaft 5 and thus the upper drum 2 with the heads Ha and Hb are rotated. A synchronous motor can be used as motor 9 in a known manner. If at With this arrangement, the braking device 11, which will be described later for the rotary shaft 5, is not actuated the rotating shaft by choosing e.g. the radius ratio of the two disks 8 and 9a at a slightly higher speed can be rotated as a reference speed.

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The braking device 11 is in the center of the rotating shaft or between the disc 8 and the lower end of the base plate 7 and can be formed in a known manner »The braking device 11 consists, for example, of a rotor 11a which is attached to the rotating shaft 5, a stator core 11b opposite the rotor 1 la with a Gap therebetween and an excitation winding 11c wound on the core 11b. Here, a rotor can with of a construction similar to that of a known induction motor can be used as the rotor 11a »If When current is supplied to the winding 11c, an eddy current flows in the rotor 11a, so that a counter-rotating force acts on the rotary shaft 5 to this, with the braking force apply. The winding 11c is powered by a current i fed according to an error signal obtained by comparing the phase of an index signal corresponding to the Rotational position Ha and Hb is obtained with a reference signal. When the rotating shaft 5 in this way with the braking force is applied, the heads Ha and Hb can be rotated in synchronism with the period of the reference signal. When recording a standard television signal in Japan and the United States and / or is reproduced, the above-mentioned rotary guide drum 2 at a speed of 30 Tj / sec. »Therefore, between the Guide drum and one wound on its outside Tape, a thin layer of air can be formed (which will be described later).

In Fig. 1, T is a magnetic tape for recording and / or reproducing a signal around the tape guide drum assembly 1 revolves in a spiral. For this

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is a known inclined guide 3a at z ^ B. the fixed guide drum 3 is provided for guiding the tape T in particular at its edge. When the tape T is transported around the guide drum assembly 1 in this way, it is guided by the rotary guide drum 2 in the same direction as the rotating direction of the latter and then transported to the fixed drum 3. In order to transport the tape T, a known construction of a capstan and a pressure roller (not shown) is provided.

According to the invention, several grooves, for example concave grooves, are provided on the circumferential surface of the rotary drum described above. Here, each of the grooves is designed so that it lies in the plane of the rotary drum 2 perpendicular to its axis of rotation. In the illustrated embodiment of FIG. 1, three grooves are formed on the circumferential surface of the rotary drum 2. Each of the grooves lies in a plane perpendicular to the axis of the rotary shaft 5. In FIG. As Fig. 2 shows the cross section _t of the grooves G ₁ to G ~ preferably, for example V-shaped and narrows from the circumferential surface of the drum 2 toward its center gradually.

In Fig. 2, W denotes the width of the opening of each groove G to G ″ on the circumferential surface of the drum 2, L denotes the depth, θ its opening angle and (A and β the angles of its edge parts e and e_ or the Designated peripheral surface of the drum 2 with the inclined surfaces of each groove.

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In the embodiment shown in FIGS. 1 and 2, it is assumed, for example, that the outer diameter of the rotary guide drum 2 is 110 mm, its height 22 mm, its speed 30 u / sec, the relative speed between the drum 2 and the belt T 10.5 m / sec, the width of the tape T 2.5 ^ x -jr ~ cm, the width of the V-shaped grooves G to G_ ¥ = 0.1 mm, the depth L = 0.087 mm, θ = 60 ° and j / \ = fo = 120 °. Here, the grooves G ₁ to G are formed from the bottom to the top of the drum 2 at a distance of k mm.

The rotary guide drum 2 with the grooves G to G “can manufactured according to the following process:

1. The drum 2 is injection molded from aluminum;

2. The drum thus formed is annealed;

3 · The annealed drum is machined e.g. on a lathe so that its diameter is slightly larger than the Final diameter is;

4. The processed drum is rinsed;

5 · Be in the circumferential surface of the drum so rinsed Grooves at predetermined locations by means of a cutting tool, taking into account the final diameter the drum formed and

6. The drum treated in this way is reduced to its final diameter cut to size and their surface is machined, deburring the edges created by the formation of the grooves so that they are smooth as the figure shows.

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The manufacturing process of the rotary guide drum is ended after the drum manufactured in the last process step (6) has been rinsed again. However, if necessary, it is possible for the surface of the mounted drum to be machined by guiding a lapping tape around the tape guide drum. When the grooves are formed by the cutting tool as mentioned above, it is easy to make the cross section of each groove V-shaped. Often θ is chosen to be 6o or 90. Assuming the width W to be constant, the larger the angle θ, the sooner an air layer is formed between the tape T and the tape guide drum on which the tape T is wound. If a fold like a kink or the like. is present in the tape T, the above-mentioned condition may be preferable in order to avoid negative pressure between the tape T and the guide drum. However, if the angles (X and / i of the edges e .. and e "are reduced too much by reducing the angle θ, there may be a risk of the magnetic tape T being damaged from the edges e .. and e" or into the grooves G ₁ to G "is bent, so that the running property of the tape is impaired. Therefore, if the groove is V-shaped in cross-section, the angles oi and / 3 of the edges e .. and e" should be greater than 90 or obtuse If the edges e ... and e "are subjected to a deburring process, as mentioned above, the contact of the strip T with the rotary guide drum 2 can also be more even.

Since in the invention as described above, a plurality of, for example, three annular grooves G to G "in a predetermined Distance between each other on the outer circumference of the

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Rotary guide drum 2 of the guide drum arrangement 1 is formed are, the outside or the peripheral side of the rotary guide drum 2, even if wrinkles, such as Creases and the like occur on the tape T and the tape T contacts the rotary guide drum 2 along the folds while the tape transport communicates with the atmosphere via any of the grooves without failure. Therefore there is no risk with the invention that the pressure of the space between the belt T and the guide drum 2 is decreased, and therefore an air layer between the tape T and the guide drum 2 always becomes formed to transport the tape T stably and evenly. When the rotary guide drum is a guide drum assembly and a magnetic head can be rotated together, the rotary magnetic head can also be uniformly rotated by the invention be rotated and damage to the tape is prevented, so that a magnetic recording and / or high quality playback is achieved.

According to the invention, each of the annular grooves G is located to G "in a plane perpendicular to the central axis of the Guide drum assembly 1, so that the disadvantages of the known Arrangements in which several grooves on a rotary guide drum are parallel to the axis of rotation of the drum or are formed obliquely to the axis, avoided will. In particular, the disadvantage that the groove with the band on the part tapering towards the rotary guide drum or the part running away from it when the rotary guide drum rotates collides is avoided and thus an undesirable vibration of the belt caused by the collision of the groove with the tape caused during the rotation of the tape can be avoided.

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There are now a number of annular grooves and their Width described in detail. If the width of the annular grooves is chosen too small, the intended Effect cannot be achieved. If, on the other hand, the width of the grooves is chosen too large, the tape can in the groove will be bent and deteriorate the smooth running of the belt. As will be described later, the arrangement is a small number of annular grooves having a relatively large width W is less preferable than the arrangement a larger number of annular grooves with a relatively small width W. It was found that the width and the number of grooves have a significant influence on the belt run. Different experiments were carried out to investigate the relationship between the width and number of grooves and tape travel and the following results were obtained:

1. Number of grooves:.

Since the groove is provided to prevent wrinkles and tears of the tape, the tape must be prevented from attaching to adhere to the guide drum. When the number of grooves is increased, the tape run is significantly stabilized. The stability of the belt can be expressed roughly as follows:

Belt stability OC (1 T ~ +

where χ is the number of grooves.

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As can be seen from the above expression, a larger ¥ ert of χ is preferable. However, as will be explained later, it has also been found that as the value of χ increases, the thickness of an air layer between the
Band T and the rotary guide drum 2 is formed so
greatly decreases, so that the effect of the grooves on the belt travel decreases.

As a result of various experiments one came to
conclude that at least three annular grooves are attached
formed the circumferential surface of the rotary guide drum
can be.

2. Width of the grooves:

The experimental data are in the following Table specified:

Tabel

Width of the grooves Number of grooves A (%) (mm)

0.1 3 0.10

0.15 0.15

0.2 3 0.13

0.2 4 0.17

0.2 5 0.27

0.3 3 0.50

0.3 h o, 8o

0.4 3 1.20

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The condition under which the data in the table above is obtained is as follows:

(a) The rotating speed of the drum, which has the same construction as that of Fig. 1, is denoted by a. Of the However, braking current i is chosen to be zero (i = θ) here;

(b) The drum is powered by a motor of the same construction like that of FIG. 1, the braking current i being selected to be zero (i = θ).

In addition, the tape is transported at a normal speed and a back tension applied to the Guide drum wound tape is maximized by adjusting the tape drive system. If under under this condition the speed of the drum is denoted by b, the speed reduction ratio A can be expressed by the following equation:

a = - * ^1O °

The cross-section of each groove is V-shaped and the grooves are equidistant along the width of the belt formed on the peripheral surface of the guide drum.

This means that the size A determined by means of the above Experiment is nothing other than the frictional force between the belt and the drum. Of course the size A should be small. In view of the frictional force, each groove should therefore have a small width to have.

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The width ¥ of the groove should be, for example, 0.025 mm. With regard to at the risk, however, that e.g. the coating material that falls from the belt can clog the groove, the width of the groove can be practically larger than 0.05 mm be. On the other hand, it was found that when the Width of the groove e.g. 0.3 or 0.4 mm is selected, the frictional force increases and the measurement results are scattered caused. This means that such a case poses some problems from a practical point of view.

If the servo system described with reference to FIG. 1 is used, the variable A must be less than or equal to 0.7 ° . The quantity A = 0.7 $ is, strictly speaking, a theoretical quantity and in practice it is necessary for this quantity to have a certain safety range with regard to the deviation of the parts of the device and the deviation during manufacture. If the magnitude has no safety margin, the period of rotation of the head cannot perfectly follow that of a reference signal of the servo system of the drum. For this reason, the upper limit of the width W of the groove should be less than 0.25 mm. In addition, a large frictional force is undesirable not only in terms of the servo system but also in terms of damage to the tape.

Based on the above experiments, the following condition arises:

0.05 now ^ "W = - 0.25mm.

It was also used in the experiment in which a tape with different Wrinkles have been transported around the drum,

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provided that the number of grooves should be equal to or greater than three.

In the embodiment described with reference to the figure the tape guide drum assembly 1 from two upper and lower drums 2 and 3 and the upper drum 2 only is rotated at high speed together with the heads Ha and Hb. When the lower drum 3 on its The circumferential surface is provided with grooves and only these together is rotated with the heads at high speed, the same effect as mentioned above can be achieved will. It is also possible that both guide drums 2 and 3 with grooves are rotated at high speed with the same effect. Here can be the sliding resistance between the guide drums and the tape around them can be effectively reduced. It is also possible to change the direction of rotation of the drum together with the heads Ha and Hb opposite the direction of travel of the tape T to reverse it. This is the relative speed of the tape run with respect to the heads Ha and Hb increased compared to that of the embodiment of FIG. 1, to extend the upper limit of the frequency band of a signal that can be recorded and / or reproduced.

In the embodiment of FIG. 1, the heads are Ha and Hb attached to the rotary guide drum 2, but can they also on a separate drum from the rotary guide drum Rotary part to be attached. Here, the number of rotary guide drums and their speed can be independent of the rotation of the heads Ha and Hb can be selected so that the sliding resistance between the rotary guide drum and the band around this can be kept at a maximum value.

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In the embodiment of FIG. 1, two heads Ha and Hb are equally angularly spaced and rotated in the same plane, but a or several rotary heads are used, their angular distance is not limited to the same values, but can also be different. The invention is also based on several heads applicable, which are rotated at a distance from one another along their axis of rotation. Also the number of tape guide drums is not limited to two as in the case of FIG. 1, but can be three or if necessary amount more. In this case, it suffices that one of the drums is rotated at high speed.

The cross-sectional shape of the concave groove is not limited to the described above, but can also be U-shaped, for example.

From the above description it can be seen that the invention eliminates various disadvantages that occur in a conventional Recording and / or reproducing apparatus with a rotary magnetic head can be avoided without damaging the tape. In addition, the inventive Device the tape can be transported stably, so that the recording and / or playback of a Signal can be improved.

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Claims (1)

Expectations . ~ 7) Tape recorder and / or playback device, consisting of from a tape guide drum which is rotatable on an axis is attached, at least one rotary head for recording and / or reproducing a signal that is coaxial is arranged to the tape guide drum, a device for helically guiding a tape around the circumference of the tape guide drum, and at least one Groove on the circumferential surface of the tape guide drum, thereby characterized in that the groove lies in the plane substantially perpendicular to the axis of the guide drum. 2. Apparatus according to claim 1, characterized in that the edge angle of the groove with the peripheral surface of the drum is an obtuse angle. 3. Apparatus according to claim 1, characterized in that the te W of the opening
0.25 mm met. Width W of the opening of the groove the condition 0.05 mm = W. k. Device according to claim 1, characterized in that the number of grooves is at least three. 5. Apparatus according to claim 1, characterized in that the Speed reduction ratio A (= χ lOO) is greater than $ 0.7. V / ed. 309845/1088 1* Blank page