DE8125650U1 - TAPE GUIDE DEVICE FOR MAGNETIC TAPES AND MAGNETIC TAPE CASSETTE WITH SUCH A DEVICE - Google Patents

Description

O.Z. 0050/035391

Tape guide device for magnetic tapes and magnetic tape cassette with such a device

The invention relates to a tape guide device for Magnetic tapes, consisting of tape guide elements which are in contact with the magnetic tape, one side of the magnetic layer and having an electrically insulating film side, and particularly relates to a magnetic tape cassette containing such a magnetic tape guide device, wherein in each case in the tape running direction the tape from an unwinding tape roll is unwound, then with at least one inlet guide element each on the layer side and film side in Contact is made and then in contact with the layer side and the film side via at least one outlet guide element is wound up on a take-up tape roll.

Tape guides are varied from magnetic tape recorders to audio, video, and data signal recording known. There are also a wide variety of tape guide devices such as rollers, pegs, etc. in magnetic tape cassettes known.

It is also known that as tape speeds increase also the electrostatic charges of the parts in moving contact, such as tape and Tape guide devices, enlarged grounding and sticking of the tape to the devices occurs, in particular in unfavorable climatic conditions and / or special magnetic layer and tape film combinations. The consequence is an at least temporary blocking of the tape, so that recording / playback processes are disturbed or impossible will.

BASF Aktiengesellschaft - 2 - O. Z. 0050/035391

^r It is known from DE-OS 30 10 772 for magnetic tape cassettes ⁿ for audio recording on metal film magnetic tape to arrange a discharge and ground connection member within the cassette, which is a conductive connection from the layer side of the magnetic tape to a device ground potential connection manufactures. The use of such a special member requires changes to the cassette and an adaptation of the device, which must be avoided in a finished cassette system because of the expense involved. An application for tape guide elements is not known and not obvious.

It is generally known for magnetic tapes to provide backing layers which reduce the roughness of the poleside of the tapes jg to improve the winding ability of the tapes on flangeless winding cores. This reduces the risk of tape sticking to guide elements due to downsizing the contact surface is indirectly reduced.

2Q It is also known, for example, conductive layers made of carbon black or Apply graphite to tapes, in particular to the polish side, in order to reduce the surface resistance of the respective Lower band area. (Cf. CH. Schneider, H. Völz "Magnetic tapes and basics of the transport works" Akademie- -Verlag Berlin 1970).

Both changes to the tape, .back coating and Conductive layer training, are too costly to block of tapes in mass-produced video cassettes to avoid 3Q.

The invention has therefore set itself the task of avoiding the tape blocking without changing the magnetic tapes.

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According to the invention, the object is achieved with a tape guide device of the type defined at the outset so that at least two are known to consist of electrically conductive Material existing tape guide elements via an electrically conductive connection for charge equalization between the tape layer and tape film side are connected to one another.

This ensures that the amount of charge which is present and which causes the tape to be blocked on guide elements be balanced on the tape.

Thus, by reducing the amount of static electricity, it is now surprisingly possible to remove the surfaces of the strip and Form guide elements smoother, so that in particular when recording video through elevations on the tape and tape guides caused signal interference can be avoided.

In further developments, the ohmic resistance of the conductive connection can be in the range of up to 3 megohms; but it can also be of the order of magnitude of the surface resistance of the strip layer side, in particular at 1 megohm.

The resistance can expediently also be one or more 100 kiloohms, which accelerates the charge equalization will. In practice, the conductive connection can consist of resistive material, such as carbon layers etc. It is advantageously also possible to use a metal body or a conductive lacquer or a semiconductor lacquer as the conductive Connection to use.

The task at hand is also used for a magnetic tape cassette, in particular a video cassette containing a tape guide device according to the invention, in which in each case in

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BASF Aktiengesellschaft - 4 - O. Z. 0050/035391

^{^ Tape direction the tape} is unwound from an unwinding tape roll, then is in contact with at least one inlet guide element on the layer side and polish side and then in contact with the layer side and film side via at least one outlet guide element

a winding tape roll is wound, according to the invention solved in that the inlet and outlet guide elements consist of electrically conductive material and between the individual inlet guide elements as well ^ q between the outlet guide elements each one electrically conductive connection is provided.

A simple and effective change to the cassette can thus cause a serious problem with the tape running, in particular <e other with magnetic tapes with very different surface resistance values occur on the layer and film side, recoverable.

In a further inventive magnetic tape cassette DER 2Q same type, it is useful both as to provide between each inlet guide elements, between an infeed trapping-leading member and the only one in this embodiment electrically conductive Ausiauf-guide element, an electrically conductive connection.

This makes it possible to use additional guide elements made of insulating Material, even if they are further apart.

τη In a practical version, the electrically conductive Connection consist of sheet metal, which can easily be inserted into the cassette, even afterwards.

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In a further, practically advantageous embodiment, the conductive connection can be made of a graphite or carbon containing There are varnish that can be easily attached to the cassette during manufacture or afterwards.

Finally, it is also conceivable in a cassette that has a sliding layer or film for the tape rolls, to train these metallized and to use them in direct contact with parts of the guide elements as a lead connection.

In the context of the present invention, the property "conductive" is understood to mean that an electron and hole conduction takes place in the shortest possible time. It is therefore all suitable as a ladder and Semiconductors known metals and substances for use |

as a "conductive connection". Insulating materials or materials that are only temporarily conductive are unsuitable for the A connection to the charge equalization from the layer to the film side of the tape to be realized technically.

becomes a tape guiding device, essentially consisting of I.

from an unwinding roll, the tape guide elements for I.

Layer or film side and the take-up roll considered, electrostatic charges can occur at the following points in the system.

The friction between the belt and the guide elements occurs Static electricity, or electrical induction, and both the body, belt and guide element, become electrostatic charged. This charge can also be added to each body by separating the already existing ones Charges arise.

BASF Aktiengesellschaft - 6 - O. Z. 0050/035391

"" By separating the magnetic tape from the outer winding of the tape The supply reel can also cause a charge separation between the withdrawn tape and the remaining external tape Band winding take place, so that a contact tension arises. Normally there are positive and negative amounts of charge separated, which are transported on to the corresponding belt locations.

In both cases it is a question of indistinguishable ίο electrostatic charge generation or separation and their The sign is determined by the relative dielectric constant of the material.

Another factor is important, the charge affinity, by which it is determined on which surface which body at which point in time a larger or smaller one

^{: i} Amount of charge is present. In addition to the respective relative dielectric constant, the current properties of the surfaces involved play an important role. This also means that the removability of the respective charges is different, for example from the layer side and the film side of the tape. Charges are more difficult to dissipate from the foil.

The above considerations about the generation and distribution of occurring electrostatic charges raise no claim to completeness or absolute correctness, as it is known to be extremely difficult to determine the origin and / or to determine the size of such charges as

3Q electrostatic charges are everywhere and therefore the measurements are inevitably influenced.

Details of the invention are described below with reference to the exemplary embodiments shown in the drawing.

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? igur 1 a magnetic tape guide device according to the state of the technique

Figure 2 shows a first magnetic tape guide device according to the present invention

Figure 3 shows a second magnetic tape guide device according to of the present invention

FIG. 4 shows a motor-load diagram of a chromium dioxide magnetic tape in a device according to FIG. 1

FIG. 5 shows a motor-load diagram of the same magnetic tape in a device according to FIG. 2 and FIG. 3

A magnetic tape guide device according to FIG. 1 consists essentially of a magnetic tape 4 with layer side S and carrier side F ₃ which is wound from an unwinding roller 6 on a reel 7 to a winding reel 8 on a reel 9 or vice versa. On the way from the roller 6 to the roller 7, the tape is moved over tape guide elements 10 and 20, as well as 11 and 21, generally guide rollers or pins, the contact with the magnetic head, not shown here, usually taking place between the elements. Depending on the angle at which the band 5 wraps around the guide elements, the contact parts between the band 5 and elements 10 or 20, 11 or 21 are of different sizes.

Figure 1 can represent the tape guide device in one of the known video cassette systems. In that are the elements 10 and 20 metal sleeves, which are on cassette-proof plastic axes are arranged and 11 is a metal pin, while 21 is also a metal pin or a metal roller.

BASF AMiengesellschaft - 8 - O. Z. 0050/0 ^ 5391

^r In operation of the cassette, particularly in fast forward and rewind of the tape 4 within the cassette (speed about 0.8 m / sec) is on the belt in frictional contact with the guide and / or deflection elements, resulting in the generation of static electricity . In this case, taking place between the elements 11 and 21 by the applied magnetic layer charge separation S is low, since a thereby resulting friction stress between the layer and 11 and 21, due to the relatively high conductivity of the layer immediately q] dismantled. The situation is different on the back of the belt: the charge 12 transferred here from guide elements, for example 10, onto the belt is immobile on the isolated belt surface and is transported away from the guide element by the belt movement.

As a result of the friction of the foil side F on the metal pins 16 and 20, the metal gives off large amounts of free electrons the film F and is thereby itself more positive. As a result of opposing charges of different names

2Q there is a blocking effect. Since the negative charge on the Layer side S and the one on the guide pins 10 and 20 The resulting positive charge is only separated by the thin film, a considerable amount is created between the tape and the pin electrostatic attraction which causes the tape to stick and block, so that the magnetic tape assembly becomes unfit for use.

In addition, it must be assumed in each case that due to the separation of the tape 4 from the winding 6 or 8 of 3Q an anyway increased amount of charge (due to the contact charge) must be assumed on the film F, which further intensifies the blocking or adhesive effect.

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BASF Aktiengesellschaft - 9 - 0.2. 0050/0 ^ 5391

'"In the case of the magnetic tape used in all of the following experimental arrangements it is a commercially available video magnetic tape with a chromium dioxide magnetic layer that has a sheet resistance (Surface resistance measured with a square test arrangement on the layer side) of approx. Such chromium dioxide tapes have sheet resistances in the range of about 10 ^ to 5 »10i £ depending on the type of chromium dioxide -Materials, size of the chromium dioxide particles, degree of filling the layer, related layer additives that reduce the ionic

] q increase conduction, as well as binder. The foil of the tapes

has a typical surface resistance between 10 and 10 JL A common measuring arrangement consists of a two-part and two-pole contact surface for the tape, which is used in Measurement rests flat and a resistance measuring bridge.

The is measured based on a square strip area Resistance value at which the current ambient conditions are automatically taken into account, such as surface properties, moisture, pollution, etc.

FIG. 2 shows a first magnetic tape arrangement according to the invention. As in FIG. 1, all guide elements 10 and 20 or 11 and 21 are made of electrically conductive material, for example made of metal, and therefore designated with the suffix "M". According to the invention, the guide elements are 1OM

-j and UM or 2OM and 21M with a conductive connection each 15 or l6 to balance the load on the hinge sides S and F connected to each other.

In the example, sheet metal brackets 15 and 16 are shown here represents. However, the connection can be made from any conductive material such as graphite, molybdenum sulfite, other semiconducting materials Substances, conductive varnish or resistance material such as carbon U3W. exist.

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BASF Aktiengesellschaft - 10 - Ο.Ζ. 0050/035391

* "This allows the negative charge from layer S to The guide element UM and then flow off via the guide connection 15 to the guide element 1OM, i.e. it finds a Charge equalization takes place so that the charge difference between Guide element 1OM and layer side S is dismantled and thus the forces of attraction also disappear. This will The contact area between the belt and the guide element is also reduced, which in turn leads to the generation of static electricity is prevented from the start, i.e. the effect of the charge equalization also brings the charges to and after to disappear. In experiments, you can press 10 and 20 or 11 and 21 at the same time a wire, a blocking arrangement can be brought to run smoothly.

15th

The conductive connection can practically also be established by a metal insert or overlay. Appropriate the resistance value of the connection should be such that the amount of charge present in a sufficiently short time 20 is removed so that the tape does not hit the guide element adheres.

In a further embodiment in FIG. 3, in contrast to the example in FIG. 2, the guide roller 21 is made of plastic manufactured, 21K. Here the lead connection corresponds to 17 * die e.g. can consist of a graphite strip in the cassette, the baffle 15 in Figure 2. Since the roller 21K is now from Consists of plastic, is for the belt running direction 2, return, only at the guide elements 1OM and UM a charge

2Q compensation possible, but this is also possible due to the opposing materials with very different surface resistance values (metal approx. 0 ^ 2, plastic approx. Io ¹² &, layer approx.

10 ic _} Foil approx. 10 ¹² Ώ) leads to the tape sticking and thus blocking the transport. The remedy provides

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conductive connection 18, which has a baffle inside or outside, e.g. on a cassette wall or along a web in the cassette or a metallized layer or film over the tape rolls 6 and 8 or a conductive lacquer or semiconductor lacquer connection can be. The result is a perfect run of the magnetic tape device.

Figures 4 and 5 show on the basis of engine load diagrams the conditions in a device according to Figure 1 and, in contrast, the surprising results of the invention Arrangements from Figures 2 and 3 «

Figure 4 shows the current curve of a strongly blocking tape guide device, in which a belt run is reestablished by reversing the direction in each case with an absolute belt standstill had to become. On average, there was a change between half load - S ^ and full load L max. 1 denotes the forward direction, 2 the reverse direction.

In contrast, in the case of a device according to Figure 2 with the same tape, a chromium dioxide tape and the same cassette, however, with metal brackets 15 and 16, a very even and undisturbed belt run can be obtained with about a tenth the full load energy was required (-

Sign.

Claims (11)

BASF Aktiengesellschaft O-Z- 0050/35391 rNew protection claims 1. Tape guide device for magnetic tapes, consisting of tape guide elements which are in contact with the magnetic tape, which has a magnetic layer side and an electrically insulating pollen side, characterized in that at least two tape guide elements known from electrically conductive material via an electrically conductive ig connection (15, 16, 17, 18) are connected to each other to balance the charge between the tape layer and tape film side. 2. Apparatus according to claim 1, characterized in that c that the ohmic resistance of the conductive connection is in the range up to about 3 megohms. 3. Device according to claim 1, characterized in that that the ohmic resistance of the conductive connection 2Q is roughly in the order of magnitude of the surface resistance the tape layer side (S), in particular at about 1 megohm. 4. Device according to claims 1 to 3, characterized in that the conductive connection consists of resistance material. 5. Device according to claims 1 to 3, characterized in that the conductive connection is a metal 2Q body (15, 16) is. 1 ( I)
IIII 3ASF Aktiengesellschaft - 2 - 0.2. 0050/35391 · ■ 6. Device according to claims 1 to 3, characterized in that the conductive connection (17, 18) consists of conductive varnish or non-conductive varnish. - 7. Magnetic tape cassette containing a magnetic tape guide device according to claim 1, wherein in each case in the direction of travel of the tape the tape is from an unwinding tape roll is unwound, then each with at least one inlet guide element on the layer side and polishing IQ side is in contact and is then wound onto a winding tape roll via at least one outlet guide element in each case in contact with the layer side and the film side, characterized in that the inlet and outlet guide elements (11, 10 ._ or 20, 21) made of electrically conductive material exist and between the individual inlet guide elements (10, 11) and between the outlet guide elements (20, 21) each have an electrically conductive connection (15 or 16) is provided. 8. Magnetic tape cassette containing a magnetic tape guide device according to claim 1, wherein in each case in the direction of travel of the tape the tape is from an unwinding tape roll is handled, then with at least one at a time - The inlet guide element is in contact on the layer side and the film side and is then wound onto a winding tape roll via at least one outlet guide element, characterized in that the inlet guide elements (10, 11) and an outlet guide 3Q approximately element (20) made of electrically conductive material exist and both between the individual inlet -guide elements (10, 11) and between one Inlet guide element (11) and the outlet guide element (20) an electrically conductive connection (17 or 18) is provided. • I * I (I BASF Aktiengesellschaft -3- ° ² 0050/35391 9. Cassette according to claim 7 or 8, characterized in that the electrically conductive connection consists of sheet metal (15, 16). 10. Cassette according to claim 7 or 8, characterized in that the electrically conductive connection (17, 18) consists of a graphite or carbon-containing paint. 11. Cassette according to claim 7 or 8, characterized in that the electrically conductive connection consists of a metallized film.