DE1499574C - Tape drive, especially for magnetic tape devices - Google Patents

Description

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The invention relates to a tape drive, mechanisms are set in motion quickly and, in particular, for magnetic tape devices, are stopped for transport, while the relatively slow wire of a tape at a regulated speed in advance of the tape reel of higher inertia by a certain direction from a tape supply reel to change the tape loop length within the beciner z. B. from the recording and playback head 5 adjacent associated braking mechanisms protruding magnetic head assembly over is equalized. Therefore, the drive mechanism acts tape take-up reel, with at least one between correspondingly only on the relatively short and light of the magnetic head assembly and each a tape-tape piece between the brake mechanisms, so that reel-arranged vacuum chamber, the sub-start-stop times of the order of a few pressure with a common to the vacuum chambers io milliseconds can be easily achieved,
sam coupled reducing valve is changed and with most of the digital devices currently in use for the determination of the respective belt drives, constant counter-rotating belt loop lengths are provided, drive shafts are used to which pressure rollers or a servo drive are assigned for the other associated control mechanisms, which controls the tape reel to maintain a predetermined respective tape selectively according to a pre-tape loop length. Press or release the given start-stop sequence. Tape drives and in particular magnetic tape- The large friction drives acting on the tape are an example of many modern input and impulse forces, but cause difficulties that allow controlled transport of a problem with regard to the train drive and the tape at high speeds. 20 tape guide. In order to protect the tape, devices for signal recording and playback of high pneumatic or vacuum quality are often used, but require a control with relatively operated controls. All of these double high accuracy, since the signals are recorded with a high drive shaft arrangement, however, are very complex or wide bandwidth adorned and set certain limits in terms of speed and the tape often moves at high speed and control, which is better off. Correspondingly precise control is also required, and versatility is of increasing importance in tape recorders in which electric long. An additional property to be striven for, static or thermoplastic recording processes, consists in step-by-step operation or in · being used. In the following, however, only the possibility of asynchronous step movements of a magnetic recording is described, although it can be carried out 30, in order to be able to record data characters in a predefined normal representation. ,
the way generally applicable to tape drives The problems of precise tape transport are. * Of course not related to digital tape drives. Tape drives are already known (see e.g. restricts. While for digital tape drives the USA.-Patent 3 156 423), in which a kri drive shaft mechanism is used for acceleration and deceleration ,. the table is, these belt drives allow relatively large amounts of friction to act on a moving belt. Changes in the nominal speed (e.g. in addition to this drive shaft mechanism, there are ± 5 <y ₀ ). Recording devices for recording with various auxiliary devices for controlling measured values as well as audio and video signals for the desired tape movements are available. 40, however, require a much more precise speed. These auxiliary devices include control, while start-stop times and vacuum chambers between the respective lengths are less important for them. With a measured value tape supply reel and the drive shaft mechanism recorder, the speed and fluctuations between this drive shaft mechanism must often be kept within very narrow limits and a tape take-up reel. 45 become, e.g. B. within the tolerance of ± 0.1%>. In these known tape drives, the speed must also be in a very large tape that can be regulated with a high nominal speed of ßen range, z. B. between 19 and z. B. 190 to 380 cm / sec can run, very gently 300 cm / sec. Regarding the speed control, this will be dealt with in order to avoid tearing or stretching or, in the case of these drives, usually a servo-controlled shaft end abrasion of the oxide layer. Extra drive is used, which by comparing the timing or playback head arrangement determined by the tape as it passes the on a time reference track on the tape works stably on reference pulses with a fixed reference value, the precisely prescribed path. A higher efficiency can only be achieved here by meeting these demands for improving the servo devices, digital tape drive which operates incrementally and in what would normally be a complete redesign, entailing intricate problems of the respective device. Other orders. Digital tape storage devices must namely speed controls, such as. B. the tape used by the Hch in very short time intervals and over most of the sound recording devices, work very short tape lengths in motion using capstan drives higher and can stop in order to the respective associated 60 mass inertia, which cause little effort, data processing systems with regard to which, however, have a limited capacity.
To be adapted to working conditions. The problems that occur when the movement of the tape drives known up to now were precisely arrangements of low inertia used to control a tape without complicated devices, be it the tape wear, tape loops of variable length in the tape path between 65 or the limits of the performance of the tape supply reel in question high inertia and the fenden system arise from several requirements. Form drive shaft mechanisms. The extremely high acceleration and deceleration arrangements allow the band between braking and step-by-step operation

Drawing devices are required that cannot do with the narrow range of speed controls be compared. It is therefore desirable to provide a tape drive or control mechanism that has any or all of the properties mentioned.

It is now a system for moving a tape in a magnetic recording system Playback device became known (British patent specification 875 123). In this known recording and playback device, the tape is guided pneumatically and without rubbing guide elements. Vacuum chambers are provided through which the belt forms loops is passed through. The device in question is constructed so that the tape is in discrete intermittent Steps is movable. The recording and playback takes place in the time segments in where the tape stands still. When the belt has come to a standstill, the belt is tensioned by a clamp and determined by the negative pressure in a first of several vacuum chambers. Because of the effect the clamp, the other vacuum chambers have no influence on the belt tension. Will the tape Moved one step further, said clamp is released and another clamp is inserted to the effect. At the same time, a valve in the manner of a shut-off valve creates a vacuum in a second Vacuum chamber generated. The increased force acting on the belt is then differentiated by Determined negative pressures in the first and second vacuum chambers. The belt therefore continues to move.

During the processes considered above, different strengths act on the respective band Forces, d. This means that the belt is subjected to different levels of stress. This in turn results in the disadvantages have been shown above with respect to the devices operating with friction guiding elements.

The invention is based on the object of showing a way of avoiding the the Above considered known tape drives adhering disadvantages to proceed with relatively The speed of movement of a belt is low in terms of design and circuitry to keep it as constant as possible.

The above-mentioned object is achieved with the aid of a belt drive of the type mentioned at the beginning according to the invention in that the negative pressure difference generated with the reducing valve in the Vacuum chambers caused the tape to move past the magnetic head assembly and the circuit regulates the pressure difference in the vacuum chambers so that the belt speed is constant.

A servo system is used for continuous belt movement at a certain nominal speed used. Accurate speed control is achieved by controlling one on a time reference track time reference signal recorded on the tape is reached. The one recorded in the time reference track The time reference signal is a signal of a fixed frequency recorded next to the information track. The frequency of the reproduced signal is therefore a direct measure of the actual tape speed at the Magnetic head assembly. The time reference signal obtained is compared with the aid of a frequency comparator circuit compared to a signal of constant frequency. A signal is obtained from this comparison, which corresponds to the error in the belt speed. The pressure difference in the two Vacuum chambers are regulated by the frequency comparison. This will affect the magnetic head assembly Maintain the desired belt speed in each case. The servo system also includes for the Tape supply reel and to be designated as sensing devices or tape sensors for the tape take-up reel Means that maintain a constant belt loop length in each vacuum chamber. The pressure difference in the vacuum chambers is

ίο being kept up to speed changes balance.

The two vacuum chambers contain devices that adjust the belt tension with the belt loop length to change. This can be more variable with the help of an elongated recess (or with the help of a slot) Depth. This recess or this slot lies on the center line of the respective Vacuum chamber between the side walls and cuts the belt loop when it is in the desired area is located within the vacuum chamber in question. The relevant depression or the relevant slot enables a secondary air flow in one of the respective belt loop lengths dependent strength, in such a way that the respective vacuum chamber on the belt loop like a spring acts. Changes in the vacuum content between the two vacuum chambers thus call shows a tension difference in the belt, even if both belt loops are the same Have length. The device provided for changing the voltage also ensures a stable position the belt loops in the vacuum chambers during all operating states.

Changes in pressure can be carried out extremely quickly in the two vacuum chambers, however not instantly. The time it takes to do this depends on the size and shape of each Vacuum chamber. In general, smaller vacuum chambers allow faster pressure changes can be achieved. With a smaller vacuum chamber there is a higher acceleration, however the tape storage capacity is low.

The pneumatic belt drive can have small and large vacuum chambers on each side of the magnetic head assembly. The small vacuum chambers are used to accelerate the process quickly of the tape used; they are located on each side near the magnetic head assembly. One for the control circuit provided for controlling the belt speed controls the negative pressure in these two small vacuum chambers, depending on control signals and read time reference signals. The larger vacuum chambers offer less tape storage capability Mass inertia between the respective small vacuum chamber and the associated tape reel. the Pressure in the large vacuum chambers is then measured by tape sensors that are in the smaller vacuum chambers are provided, adjusted so that the existing in the associated small vacuum chamber Volume remains roughly the same. The tape sensors in the larger vacuum chamber provide control signals for the servo system or for the servo drive of the tape reels, so that the tape loop in the relevant

the larger vacuum chamber is held in a predetermined position. This way is one extremely fast acceleration and deceleration of the belt possible without the need for a servo drive

high sensitivity for the tape reels is required.

The small vacuum chambers can be used with a drive shaft for driving the belt working belt drive can be used to compensate for short-term fluctuations in sand speed, also known as "flutter". A signal is sent through to correct the speed Monitoring of the time reference signal of a fixed frequency obtained on the time reference track next to the Recorded or contained in data tracks. The time reference signal read from the tape in question is compared with a constant signal, and the resulting signal becomes used to control a servo control device, with the help of which the negative pressure in the two Vacuum chambers is controlled. With a suitable phase position, the provided comparator device generates due to their output signals small short-term tape movements, the amplitude of which is opposite to the determined speed changes. This way the undesirable becomes Flutter compensated.

A pneumatic belt drive for step-by-step belt movement is with small vacuum chambers provided on each side of the magnetic head assembly. The respective band is used during the the respective interstep space is accelerated or decelerated quickly. Larger vacuum chambers or Servo controls for the tape reels can be used for further balancing after each operational step be used. A band brake device can be installed between each small vacuum chamber and on the band the magnetic head assembly are provided. After the tape in question reaches full recording speed has reached and the data information has been recorded on this tape, can thus this tape can be braked quickly and then stopped. That way is any backward movement of the tape to its initial position past the magnetic head assembly avoided. For this purpose, preferably pneumatic braking devices are used, which are arranged along the tape path and in time, Licher dependence on the step-by-step tape movements be operated. With this pneumatic belt drive, a step-by-step Tape recording with high data density and high step count can be achieved what so far with others Magnetic tape facilities, was not possible.

The invention is explained in more detail below using exemplary embodiments with reference to drawings.

Fig. 1 shows schematically an embodiment of the belt drive according to the invention;

F i g. FIG. 2 shows a sectional view along the section line 2-2 entered in FIG. 1 with a variable Pressure working vacuum chamber;

F i g. 3 schematically shows another embodiment of the belt drive according to the invention;

F i g. 4 shows a simplified schematic representation a belt drive working with drive shafts and pressure rollers, which is a belt control to compensate for short-term belt speed fluctuations;

F i g. 5 shows a sectional view through one of the FIGS. 4 illustrated vacuum chambers;

F i g. Figure 6 shows a sectional view of another embodiment of one for use with one Belt drive according to the invention suitable vacuum chambers;

F i g. 7 shows schematically the structure of a pneumatically operating belt drive according to the invention to move a belt step by step;

F i g. 8 shows a sectional view along the lines in FIG. 9 entered section line 8-8, with clarification a part of the tape drive according to FIG. 7

ίο provided vacuum chambers;

F i g. 9 shows a sectional view of the FIG. 8 along the vacuum chamber shown in FIG. 8 registered Section line 9-9.

In Fig. 1 are the main parts of a tape drive shown. These main parts are shown on a broken part of the front panel 10 of a tape machine mounted. A tape 12 is used for recording and playback in one way or another Direction along a certain path between the tape reels 14 and 16 on a magnetic head assembly 18 passed. Special servo drives 20 and 22 which contain drive motors (not shown) are coupled directly to the tape reels 14 and 16 behind the front panel 10. These servo drives are shown only schematically and separated from the tape reels for the sake of simplicity.

Between the two tape reels 14 and 16 there is one on each side of the magnetic head assembly 18 Vacuum chamber 24 and 26 are provided. These vacuum chambers 24, 26 form less belt loops Inertia. Different pressures prevail in the two vacuum chambers 24 and 26. the two vacuum chambers 24 and 26, which in the present case at their upper ends to normal Ambient atmosphere are open, have a suction opening at their respective closed end 28, to which a pneumatic line 30 is connected. About one with the pneumatic The controllable interchangeable flap of the reducing valve 32 connected to lines 30 are the suction openings 28 of the vacuum chambers 24 and 26 are connected to a vacuum pump 34. The two vacuum chambers 24 and 26 also contain a sensor device 36, also referred to below as a tape sensor, which shows the length of the belt loop in the respective vacuum chamber. Known band sensors can be used Belt loop sensors can be used, such as B. photoelectric arrangements with the help of which Position of the belt loop in the respective vacuum chamber can be determined. Appropriately, however, a special arrangement is used with whose output signals corresponding to the respective strip position are generated. This will be continued will be discussed in more detail below. The output signals of the tape sensors 36 actuate those mentioned Servo drives 20 and 22, and they also control the rotational movement of the tape reels 14 and 16. The Servo drives 20 and 22 can also be equipped with braking devices (not shown) that can optionally be put into operation be provided, which allow the respective tape reel to be shut down quickly. Furthermore can various other loop position and control devices to accomplish the foregoing Goals are used.

At both ends of the vacuum chambers 24 and 26, at the entrance and at the exit (as the entrance hereinafter understood as the end closest to the magnetic head assembly 18), the tape 12 runs

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Via conventional tape guides 39 and 40, the gate 46 outputs constant frequency signals cause little friction. Preferably are leads. The frequency discriminator 44, which in itself the pneumatic bearings used for this purpose, which are designed in a known manner, yields a fault thin layer of air between the band surface and the signal, which is characteristic of the frequency difference Evoke leadership. In this way, any difference between the two is compared borrowed frictional contact effectively prevented. The vibrations or signals, some of which like pneumatic tape guides are known, signals by the tape 12 removed which is why they are not shown here in more detail and neither are time reference signals formed and of which the approximate are described. It should be noted, however, that their signals are supplied by the oscillator In such an arrangement the band practically re-io th signals are formed. The error signal generated in this way A switch 50 and an amplifier 48 become idle in the field of the magnetic head arrangement and therefore only by means of the control signal in a manner known per se Vacuum chambers generated voltages controlled trained actuating device 52 for the Rewill, Duzierventil 32 supplied. The switch 50 is in the

A part of the front panel 10 expediently forms 15 positions that can be switched FORWARD, BACK and STOP. Since there is one rear wall for the vacuum with the respective belt movement and its directional chambers 24 and 26. Each rear wall is adjustable with one device. Depending on the polarity of the actuating device 52 supplied to the elongated depression or recess 42, the cross section of which is inclined and the error signal of which the changeover flap of the reducing surface is rotated lengthwise from the open to the closed valve 32 in the corresponding direction. Increases towards the end of the vacuum chamber. The offset opposite rotation, the polarity of the parallel side walls supplied in the tion 42 is preferably located midway between the BACK position of the switch 50; it is at the same time inverted error signal with the aid of an inverter 54, small parts on both sides of the desired position. In Fig. 2 the extender valve 32 determines the changes required for a desired savings with a variable depth, but the changes in the belt movement can also be slits, the width of which changes the pressure difference between the two vacuums (as shown in FIG. 3) . Any other chambers 24 and 26. The inverter 54 and the VerForm, which have a gradual increase in cross-section, are designed and manufactured in a known manner, can also be used. So one can only briefly describe 3 ° here,
also change the width of the vacuum chambers or The setting of switch 50 in the switching position

the openings leading to the vacuum pump FORWARD, BACK and STOP can be in well-known make the rear wall elongated. The spanned manner is also used as control signals in the following gen 42 enable a pneumatic auxiliary air-labeled command signals automatically controlled current, whose cross-section (will be dependent on the band 35. These control signals can be used according to the loop length) is variable. The band conditions give way to an associated one (not shown) added loop length of a normal value for a data processing system simple control relay If the vacuum content decreases, the pressure decreases. The switch 50 can also be used as a difference be implemented on the belt loop accordingly to or fold electronic gate circuit, the away. In this way, the respective vacuum chamber 4 ° acts in accordance with the control signal supplied more on the belt loop like a spring less one of three input voltages optionally through ground, whose spring force depends on the vacuum content. switches. For example, if a This arrangement is used to tape the "STOP" signal to ground potential at the output of this grind to keep the same length in continuous operation and gate circuit appear while when occurring the tape does not creep in the rest position. The signals "FORWARD" and "BACK" are the same the. Without this balancing property, small but opposite polarity signals would be am Changes in the width of the tape or the Va- output of the circuit in question occur. the vacuum chambers cause a corresponding movement - start-stop transitions for the two running directions Things. of the tape are controlled by a servo

For speed control, the belt 12 can be set to 5 ° open or closed control loop, provided with a control track (not shown) These servo controls bring the tape to nominal value, on which a time reference signal in the form of a speed or stop it. In any case Vibration or in the form of pulses, the actuation of the switch 50 also causes the frequency at a given belt speed drive the speed control circuits for the is recorded. This time reference track is 55 bands. These speed control circuits In addition to the data track, which is also not shown, the frequency discriminator 44 then delivers this. A mentioned error signal associated with the magnetic head assembly 18 for the speed separately Playback head key control (not shown).

When recording or reproducing the data signals, the actuating device 52 for the change at the same time emits the mentioned time reference signals. The flap of the reducing valve 32 holds in the position The interchangeable flap in its set multi-frequency oscillation on the respective middle position. So there is vacuum in both genes Tape recorded and when scanning chambers 24 and 26 the same. Vacuum. Are toBandes are screened out accordingly. Each recorded in front of the two belt loops at the same length Time reference signals have been placed on a 65 so the tape remains in the idle input a frequency discriminator 44 is supplied. ment, and the intended servo drives are working Another input of this frequency discriminatory- not. However, if the switch 50 is in the position tors 44 are switched by a quartz-stabilized oscillator "VOR", so the interchangeable flap of the

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Reduction valve 32 is immediately pulled out by a certain amount, while the tape reel 16 is additionally

Angle rotated clockwise, as a result of which the tape was lent into the opening of the vacuum chamber 26.

the air flow from the vacuum chamber 24 is too. This happens depending on signals,

the vacuum pump 34 is reduced, while the determining the respective belt loop position

deliver the air flow from the vacuum chamber 26 to 5 tape sensors 36. The control circuits for the

the vacuum pump 34 is enlarged towards. Adjusting the belt speed work like

between the two vacuum chambers 24 and above, on the reducing valve 32

26 caused the pressure difference to increase or decrease the belt speed.

Belt loop in the vacuum chamber 26 one size. In continuous operation, the pressure differences are

Renal pressure and thus a larger belt loop, as already stated, is low.

voltage. The tape is therefore moved past the magnetic head assembly 18 as long as the control signal is present, whereby the tape shortens the tape at nominal speed in the loop in the vacuum chamber 24 and in the desired direction. However, if the switch 50 is extended in the vacuum chamber 26. When the "STOP" position is brought immediately, the alternating acceleration of the piece of tape between the vacuum flaps of the reducing valve 32 in its neutral central vacuum chambers 24 and 26 results in a lot of snow. The pressure at the suction openings 28 is less than the servo drives 20 and 22 can follow. thus becomes the same, with which the belt loops - The initial change in belt speed lengths also become the same. The friction of the tape depends almost entirely on the change in the tape - the magnetic head arrangement 18 thus prevents the loop lengths. However, before the full tape 20 further movement of the tape. So that the tape can take effect at loop lengths if the magnetic head arrangement 18 is brought to a standstill, it is determined by the tape sensor 36, whereupon
the servo drives 20 and 22 are put into operation. From the above description, the before (J den. As a result, the tape reel 14 delivers tape to the opening parts for accelerated operation and for continuous operation ming of the vacuum chamber 24, while the tape 25 When the tape reel 16 is started or stopped from the opening of the vacuum chamber, only the free length of tape between the vacuum 26 is absorbed. In this way, the chambers are exposed to a force The tape reels 14 and 16 run until there is practically no wear, and in addition, the given tape impulses are briefly not possible due to the sudden tensile stresses caused by mechanical tape reels. There is a limit The speed of the belt is then the speed of movement of the air stream Ömungen grind in the vacuum chambers in their given lengths and returned to the changing flap of the reducing valve 32. give. In this way, ex-

Due to the increased belt speed, extremely high accelerations and decelerations are also renewed which are delivered by the frequency discriminator 44. In addition, there is also a service Error signal reduced. The actuator-controlled speed control is available, device 52 therefore responds in such a way that it changes the speed of the respective belt at the flap of the reducing valve 32 in the sense of an all-magnetic head arrangement over automatically monitored gradual reduction of the pressure difference between 4 ° and regulates. This cruise control resp. the two vacuum conditions at the open ends -control now not only enables control the vacuum chambers operated until the required to maintain a digital tape drive, as previously explained the desired belt speed has been required and the requirements relating to it Pressure is reached. In continuous operation with a high the start-stop properties are much higher than given belt speed, the tires are 45 with a different belt drive, but rather matic vacuum chambers only with little change - also the use of a drive system for a borrowed pressure differentials operated to tape readings recording. In this case the speed fluctuations balance. The speed setting is unlimited, the average pressure difference is so great and the speed control can be used the slight friction in the course of the tape path 50 take place in a conventional manner, z. B. overcome a time reference will. The instantaneous pressure difference trace, in the time reference signals of higher frequency (and the resulting shifted tape- are recorded.

length) corresponds to the current time for the tape sensor and for the servo drives

necessary speed correction. Tape reels are made up of many known arrangements

If the contact arm of the switch is reversible from position 55. With a view to stability and performance, "STOP" is brought to the "BACK" position, however, depending on consumption, the operating sequence described above is preferably used. In some reverse direction. In this case, the application cases is a belt loop position in the polarity of the positive error signal of the frequency vacuum chambers 24 and 26 in the area between the discriminator 44 reversed by the inverter 54, ⁶ ° of an upper and a lower limit position. The tape sensor will then only issue a yes-no actuation device 52 to rotate the change, and the provided servo drives for the flap of the reducing valve 32 counter to the clock tape reels keep the tape loops in the clockwise direction fed. By the pressure-related target range caused.

The difference is the band from the vacuum chamber ⁶ 5. However, it is preferably worked in such a way that 26 leads to the vacuum chamber 24. Then the tape sensors generate a signal that the difference starts to rotate the tape reel 14, whereby the position between the actual and desired tape tape from the opening of the vacuum chamber 24 corresponds to the dragging position. Furthermore, it is

11 12

gone that the servo drives for the tape reels purpose is to respond to the level of the signal generated on each side of the provided magnet head assembly 64 a relatively small vacuum can come. A preferred embodiment of one of these 60 or 62 is provided. The dimensions of these tape-like sensor is shown in Figure I. ₁ and 2. FIG. Vacuum chambers 60 and 62 are somewhat larger. The tape sensor consists of a light source 37 and 5 selects than is required for the desired acceleration of a photoelectric sensing device 36, which is required in FIG. A second pair of vacuum chambers lengthways of the side walls of the respective mern 66 and 68 creates a moderate acceleration vacuum chambers opposite one another and which are designed for low mass tape storage. The light source 37, which is z. B. is the length of tape required inertia between the zugeeine fluorescent tube, gives light through an io arranged smaller vacuum chambers 60 and 62 and translucent elongated opening in one of the respective tape reel 70 and 72. Each side walls on the opposite side wall of the smaller vacuum chambers 60 and 62 rejects in, whereby a constant illumination of its rear wall is achieved with a density running in the longitudinal direction per unit length. The photo slot or a recess 74, the electrical sensing device 36 of which enlarges on the mentioned cross-sectional area towards the closed end of the opposite side wall, consists of a strip 38 of a photosensitive substance which is gradually elongated towards a relevant vacuum chamber. The slots or recesses 74 are marked with fes, e.g. B. a known photoconductor. This strip of increasing width and constant depth is shown directly opposite the aforementioned light. So they have in Fig. 3 arranged in the form of an elongated opening. This makes this 20 borrowed isosceles triangle; they correspond to the strips 38 from the light wave 37 in a manner determined by recesses 42 of variable depth according to the position of the opaque ribbon loop. 1 and 2.

irradiated to the greatest extent. The light-sensitive strip To create a negative pressure in the small-38 can, as F i g. 2 shows, triangular vacuum chambers 60 and 62 as well as in the size trained and on a non-conductive pad 25 Ren vacuum chambers 66 and 68 can be a single be applied, which a rectangular part of the suction pump 76 are used. For the smaller ones relevant side wall of the vacuum chamber forms. The suction pump 76 is vacuum chambers 60 and 62 If the belt loop in the vacuum chamber 24 is lengthened via pneumatic lines and via a reducer or shortened, the total valve 78 with the vacuum chamber connections changes Area of the photosensitive strip 38. 30 bound. The cruise control circuit 80 is as So that the output signal changes according to a single device that is shown with that of the time reference provided to the magnetic head assembly 64 by the change in length of the tape loop projected rectangle opposite the er signals as well as with control signals from a (not wished normal position. This output signal can be presented as a data processing system Control signal for the associated tape reel 35 is controlled. The called speed control servo drive be used. It should be seen that circuit 80 may be such as that shown in FIG. 1 being shown, that the shape of the photosensitive stripe orders and a frequency dis-38 according to any given characteristic criminator, emit a signal of a fixed frequency for the output signal can be selected. This uses the oscillator, a switch or circuit Characteristic can be a certain servo control 40 three switch positions and a servo drive for the tion of the tape reels. From the pre-interchangeable flap of the reducing valve 78 included. the For the sake of simplicity, the speed control is preferred Proportional band sensor because of its circuit 80 in FIG. 3 and in the other figures better sensitivity compared to other tape with three control inputs STOP, FORWARD and BACK sensors used for tape treatment. 45 shown.

It should be understood that air pressure changes with the inlets at the bottom of the larger

The suction pump 76 is created in the respective vacuum chamber with the aid of vacuum chambers 66 and 68

of a reducing valve are not connected via a reducing valve 82 or 84, respectively,

take place instantaneously, but in their temporal The positions of the interchangeable flaps of this reduction

Duration through the exit or entry time of the air in 50 valves 82 and 84 are controlled by servo drives 86 and

the vacuum chamber in question are determined. The 88 is controlled separately, in response to signals that

The time required in each case depends primarily on tape sensors 90 in the smaller vacuum chambers.

Line from the ratio of the vacuum chamber volume 60 and 62 are generated,

mens on the flow velocity of the air. If the operation considered above is carried out,

This generally results in the "STOP" signal being sent to the belt drive when using a low order.

In the ner vacuum chambers a larger belt acceleration is given, so is the one generated in each vacuum chamber

However, the tape storage tension will also be approximately the same as in the others

like reduced inertia. Belt tension generated from the vacuum chambers. Through this

For reasons of this, the size of the respective vacuum must stand still on the magnetic head assembly 64,

chamber must be carefully selected so that at large 60 If a control or command signal is now

With acceleration, the storage capacity of the volatility of the band in one or the other

vacuum chambers is not exceeded. Direction issued, the tape in question is

In Fig. 3 is another embodiment of one through the then between the two smaller vapneumatic working belt drive shown, vacuum chambers 60 and 62 generated pressure under who moved the above difficulties 65 and resolved to the desired nominal value are and accelerated at the extremely high speed of the belt. In dependence of the resulting changes in the belt loops in low inertia can be achieved. To this generate the smaller vacuum chambers 60 and 62

13 14

the band sensor 90 signals for the corresponding directions are used. With the help of these vacuum control servo drives 86 and 88, through which the reducers 128 and 130 are placed between the pilot valves 82 and 84 can be set. The small vacuum chambers 102 and 104 seen below press in the two large vacuum chambers - pressure difference created. The phase adjustment which itself and cause a tape transport of 5 is made by known servos for each causes larger vacuum chamber in the associated belt drive.

smaller vacuum chamber, while on the other it should be noted that the digital tape drive

Side of the arrangement under consideration, the tape from the 108 even without the device for avoiding

Smaller vacuum chamber in which the associated short-term speed fluctuations work,

large vacuum chamber is moved. As a result, through the use of the mentioned vacuum chamber

The smaller belt loops in the smaller chambers 102 and 104, however, eliminate the flutter.

vacuum chambers held in their given position. resembled, and also will reduce the

The large vacuum chambers 66 and 68 are also belt speed fluctuations by almost two if provided with belt sensors 94, the signals of which reaches orders of magnitude. It should be noted that the servo drives 96 and 98 for the tape reels are thereby devoted to the entire assembly of the tape. As a result, the tape reels 70 drive nothing changes and that an effect on and 72 rotated in such a way that the predetermined positions, the normal step operation does not exist.
of the larger belt loops. On In F i g. 5, the interior of one vacuum chamber is shown in this manner preventing the small-scale tape stored in the larger vacuum mer 102 and the vacuum control device 128 in chambers 66 and 68 from being individually. This arrangement is suitable for the inertia that the smaller storage capacity of the inclination and delay especially for the generation of the necessary short vacuum chambers 60 and 62 is exceeded by the small band and 104 loops depending on the output signal. of the frequency discriminator 124. The two small ones

In Fig. 4 is another embodiment of a 25 vacuum chambers 102 and 104 included, respectively pneumatically operating belt movement control a centrally arranged longitudinal slot or a shown used in conventional belt drives for recess 136 of variable cross-sectional compensation Brief surface known as flutter to stabilize the belt loops in the speed fluctuations are used in both vacuum chambers. At the closed end can. Small vacuum chambers 102, 104 are 30 each vacuum chamber is a suction each side of a magnetic head assembly 106 has an opening 138. The end of the vacuum chamber 102 is conventional digital tape drive 108 is provided. closed by a movable membrane, This tape drive works in a known manner with that of a central rigid part 140 and from two counter-rotating drive shafts, which correspond to a flexientresponding one that holds and surrounds this part Pinch rollers the assemblies 110 35 blen part 142 consists. The membrane is with hers or 112 form. These arrangements 110 and 112 edge between an upper and a lower Holding parts 144 and 146 are attached in two directions for transporting the tape. On a right optionally operated. Double ended to the angular bobbin 149 attached to the rigid part Ends tapering vacuum chambers 114 and 140 of the membrane on the interior of the Va-116 ensure the formation of belt loops 40 is attached to the side facing away from the vacuum chamber, is a low inertia between the drive shafts of a loudspeaker voice coil corresponding coil and the high inertia tape reels 118, 120. 148 wound up. The bottom part 150 of this arrangement die Tape reels 118 and 120 are servo-made from magnetic material; It is with drives rotated, depending on Si a center piece 152 is provided, which is in the Hohlgnalen, which protrudes into the vacuum chambers 114 and 116 45 space of the winding body 149. With his deliver the intended tape sensors. Further details of the relevant bottom part 150 on the edges such known parts of this tape drive and holding part 146 attached. The one about the frequency disaster In this case, speed error notifications that are no longer issued are not used by the terminator 124, since it is used to understand the invention signal is applied to one end of the coil 148, are not required. 50 The other end of coil 148 is grounded. With on-

Such a speed error signal occurs for signal recording and reproduction As seen magnetic head assembly 106 includes a deflection of the rigid part 140 occurs special magnetic head that can be used to record from above or below. This will increase the volume in a time reference track of the respective band on the relevant vacuum chamber from the closed drawn time reference signals is used, the frequency of which is enlarged or reduced in size. This arrangement a measure for the respective belt speed is thus similar to a conventional one on the ground is. The signals of the vacuum chamber 102 occurring at this frequency become attached speakers with the help of a frequency discriminator 124 system. It generates short-term rapid negative pressure with Compared to signals that change with a fixed frequency due to rapid enlargement or occurrence. In response to this comparison, the customer gives a reduction in the volume of the vacuum sequence discriminator in question 124 a short-term band chamber.

speed fluctuations at the magnetic head - In the membrane a small hole 151

arrangement 106 from the corresponding error signal, which can be provided through which a slow printout

in the following is also possible as a speed error signal on both sides of the membrane.

referred to as. This error signal is generated after 65 In this way, the effect of residual forces

Suitable phase setting for opposing ants on the membrane avoided during continuous operation

control of the intended vacuum regulating devices,

lines 128 and 130 are used as valve devices on the other side of the magnetic head assembly.

15 16

Riung 106 provided vacuum chamber 104 is connected in direction 161. The side walls of the vagabonds Designed in the same way as the vacuum chamber 162 just considered, they run parallel to one another. the Vacuum chamber 102. That of the frequency discrete pressure regulator 161 contains a in the middle minator 124 provided speed error signal cavity 164 with an exit port 163, the however, it is supplied in such a way that there is a cone 5 via a pneumatic line with a cone constant power (not shown) operating in the opposite direction to vacuum chamber 102 Has an effect. To this end, various measures are connected to a suction pump. A mobile coward possible, such as B. the reversal of polarity bran, consisting of a rigid central part 166 with of the speed error signal for one of the Va of a small bore 167 and a flexible part vacuum chambers, or the reverse of winding io 168, is in cavity 164 near the closed like a voice coil. Attached to the end of the vacuum chamber 162. To stare

If smaller vacuum chambers are used together with central part 166, a coil former 172 with a larger vacuum chamber is used, as is the case with the voice coil 170, which the intended meme arrangement according to FIG. 4 shows, the lower branch must deflect. The bottom portion 174 of the vacuum chamber pressure will be stronger in the smaller chambers. In one piece consists of magnetic material; In some cases, a central protrusion is provided by sudden occurrences of a central protrusion, which completely serves as a fixed acceleration of a belt. Current is drawn through voice coil 170. The rafts form an exception to this, so the membrane becomes extremely high due to the pressure difference that occurs in the case that the magnetic field generated in the small belt loops, a maximum of 20 coils and the magnetic core 175. Who is deflected in one direction or the other,
The aforementioned process is not dangerous as long as the parallel side walls of the vacuum chamber, the belt loop, after reaching the nominal speed, protrude slightly into the cavity 164, and a new formation can be made. This can be done in the direction of the rigid central part 166. A number of known devices have stood between the side walls and the membrane, one of which simply consists of an additional channel for air flow from the closed bolt or from a roller 160 consists, the end of the vacuum chamber 162 to the exit at the open end of the smaller vacuum chambers opening 163 out. When the voice coil 170 is energized, it is arranged 102 and 104 in the middle between the tape entry and the membrane towards the central magnetic core 175 and the tape exit guides. Since ^ 30 is deflected, the cross-section of this channel is enlarged by completely leaving the respective band, and more air is sucked out. Prevented the relevant vacuum chamber; The result is that at the closed end of the vacuum, a greater negative pressure remains in a position at the open end of the vacuum chamber 162. If the membrane chamber, from where it is deflected again in the opposite direction by the negative pressure, is sucked into the vacuum chamber in question 35, the cross-section of this channel is reduced. There can be. Such a bolt, however, is not required by the pressure rises, and the degree of Va required when the tape path and the open end kuums at the closed end of the vacuum chamber of the respective vacuum chamber so formed 162 decreases. In addition, a sudden movement of the membrane causes the belt to buckle during acceleration. the open ends of the vacuum chambers 102 and 40, the change in volume at the closed end of 104 is kept constant so that there is a sufficient vacuum chamber 162. A sudden change in volume-pressure difference to restore a banding causes a rapid change in the air loop. concentration per room unit and thus des

The compensation of short-term speed pressure. The change in pressure that occurs in this way occurs aside Fluctuations due to the additional use of the 45 caused by the change in the air flow, relatively simple pneumatic systems th change in pressure, but only for a short time. the Much more accurate speed control allows greater pressure change at the start of the accelerator less complicated belt drives. and delay results in a fast tape-therefore So far, they can only be used for less precise work start or belt stop, while the subsequent ones ting of digital data recording usable cheap airflow setting a maintenance of the airflow gen drives by slight modification in systems with somewhat lower constant pressure as well as its for recording of measured values, images and audio signals. Control for continuous tape movement in the whose speed fluctuates in one or the other direction, like this changes are 0.1% or less. already in connection with Figs. 1, 2 and 3

In Fig. 6 is another embodiment of a 55 that has been refined.

Vacuum chamber with variable pressure, regardless of whether it is set by a valve. This vacuum chamber works using pressure regulating devices formed in each Establishment of a facility similar to that shown in FIG. 5 trap by a butterfly valve or a membrane shown vacuum chamber. The mechanical direction should be controlled with the help of this single voice coil are short-term, for rapid acceleration, deflection with the electrical signal in required pressure changes in the respective linear relationship to which the gen vacuum chamber as well as constant pressure difference frequency, repercussions, environmental influences or zen to drive the respective belt with continuous belt loop position should have an influence, An exception to this is the case that this is enough, as it is already intentionally used for damping in connection with 65 sizes. F i g. 1, 2 and 3 has been explained. · When using the diaphragm with the voice coil

At the closed end of a conventional vacuum chamber there can be an undesirable unilateral preload 162 is a pressure control entry, if not through a small opening in the

17 18

Membrane for pressure equalization on both sides chooses whether together with the step-by-step operation

the membrane is taken care of. continuous operation should also be possible. for

With these pneumatic devices step-by-step operation alone can be achieved the simple meme band accelerations, which the branch arrangement according to FIG. 5 are used, with known powerful mechanical drive 5 while the pressure regulating drives achievable accelerations for both operating modes are far in the direction shown in FIG. 6 is used, and indeed surpass. These improved properties are very favorable for maintaining a small, practically constant value for digital storage systems, since the entire period of time for starting or stopping is used in the case of the pressure difference in the case of continuous band creatures. These regulating devices have already been described above for a band that is relatively long, and indeed explained in detail compared to io, which is why the high data transmission speed does not need to be discussed further here.
ner computing systems. The vacuum control devices for the belt lengths passing through are also important in these periods of time, since the vacuum chambers 180 and 181 are controlled by control signals between successive storages for forward and backward movement; there must be gaps that are caused by the speed control circuits 184 that no data transmission takes place before the respective control signal is generated by a data processing system (not the nominal speed. It follows from this) that the entire memory content of a given data processing system is generated. With continuous operation, the tape length is compared with a fixed frequency by reducing these gaps in each case read time reference signals without changing the information density in bits per 20-sequence signals, which means that the incorrect length unit in the recordings can be increased with respect to the low speed signals. Fluctuations to compensate for these fluctuations. Furthermore, the start and stop times and are obtained. For each step movement, the control or command signal used for the tape forward movement or tape back movement in the step-by-step magnetic tape recording or generation is of even greater importance. Here an acceleration and deformation of a short voltage pulse is required, the delay of which of the respective tape between one and the other length of the short tape acceleration interval to the other bits is required. The tape or achievement of the nominal speed corresponds. The magnetic tape should, as far as possible, already have nominal speed - the relevant pulses are rectangular or have reached speed before the recording or otherwise suitably designed to achieve the desired playback, although the recording can be accelerated according to the electrical properties even when the tape is not running. In order to achieve the respective actuated throttle valve or the diaphragm operating mode as a valve in-attainment of a direction suitable for normal computer tape, the signal recording or must be ensured. If only the step-by-step playback is carried out with an information density of 79, 219 35, the speed control or 316 bit / cm can be carried out. For this reason, circuits 184 are simplified in such a way that power amplifiers have hitherto been used for a step-by-step operation to generate methods with punch cards or punch-long current pulses for the voice coils, with magnetic expenditures being used.

Drawing with good information density then paper 40 Each of the smaller vacuum chambers 180 and 181

Magnetic tape converters were used. is equipped with a pneumatically operated brake 186

With the pneumatically operated tape attached to the magnetic head assembly 182

The high belt acceleration that can be achieved by the drive can be

however, data recording and playback is attached with mern. As is particularly clear from FIG. 8th

high information density can be seen in step-by-step tape 45 and 9, there is such a pneumatic

movement can be carried out. The brake required for this is to be actuated by a signal

Borrowed devices are using the tapered voice coil arrangement

Features of the embodiment membrane 188 described above, as used in a loudspeaker system

built up. is provided. The membrane 188 adjoins it

In Fig. 7 is a pneumatically operating belt 50 of the outer wall of the vacuum chamber in question

Drive shown, the step-by-step recording next to the magnetic head arrangement. 182 a little

and playback mode in two directions suitable lumen. The edge of the membrane in question 188

is, with a high information density is achieved. closes with the outer surface of the relevant var

In addition, a continuous operation in the vacuum chamber can be tight, and that from the membrane the directions as well as seeking out predetermined 55 enclosed part of the wall is with small

Storage locations are carried out. It should be noted that bores 189 are provided. The membrane is made

that the step-by-step operation, if desired, is largely made of flexible material alone; an exception

can be provided. For this purpose, a small rigid central part can be formed from it

some parts of the device provided can be omitted, a hollow bobbin 190 for the reception. 60 connects to a voice coil. A fixed one

On both sides of the recording and for the core 191 is provided playback magnetic head assembly means forming part provided with a the actual magnetic core, which is protrudes per 190,180 and 181 in the Wickelkör- 182 each have a vacuum chamber. Flows provided as a result of a brake signal, the pressure of which is adjustable. Both Va- a current through the provided voice coil, so vacuum chambers are used to move the tape in 65, the rigid winding body 190 of the diaphragm is small steps. The wall of the relevant vacuum chamber provided at the closed ends quickly outward from the perforated sides of the vacuum chambers 180 and 181 — vacuum control devices — are then deflected. The small one enclosed by the membrane

19 20

Volume expands rapidly, whereby the pressure has a period of one millisecond and the band in front of the membrane is reduced. The resulting path of a little less than 0.025 mm negative pressure is then covered through the holes 189 . The diaphragms in the pressure regulators also on the tape or magnet of their flexible parts located behind the wall of the relevant directions then return to their normal position due to the resilient effect of the vacuum chamber. As a result, this band is strongly opposed to the vacuum chambers 180 and 181 . The ripening between the band and the inner wall is worth it again, so a further movement of the vacuum chamber in question becomes impossible on this band in the forward direction, since the be-mode is greatly increased. As a result, a sudden braking of the belt occurs in the belt path at an accelerating pressure difference that is no longer present. Usually this results in a reverse, upward movement of the belt in the opposite direction.

That for actuating the device for band braking. If this were made possible, the required pneumatic braking would return to its initial position with respect to the magnetic brake signal can return from the trailing edge of the FORWARD or head assembly 182 , so that only a BACK control signal would result from a high-pass signal resulting in forward movement of the tape device 194 and a rectifier arrangement 195 would be achieved in step-by-step operation. Through which to be won. The high-pass circuit 194 differential pneumatic brakes 186 will, however, receive the confusion of the occurring control or command of each forward movement after the termination signal and generates a command signal on its leading edge.
Needle impulse of one polarity and on the back. The rectifier arrangement 195 bilden- tive command signal at the output of the Hochpaßden rectifiers or diodes occurs only for the circuit 194, abgeleite- through said diodes from the trailing edge of the command signals 25 of the rectifying device is disabled 195, that ten pulses permeable. On the other hand, as in but the posi-Fig. 1 an operating needle pulse that can be set in three positions is used through the diode type switch, this can be provided with a white brake and the pneumatic brakes 186 after the recorder contact, via which the respective data pulse is actuated when the respective data pulse is set. On the switch in the STOP position, a brake signal from 3 ° is given by the braking effect. In the outer vacuum chambers 197 further and backward movement of the belt and 198 are prevented between each smaller vacuum des, which are created by the pressure equalization in chamber 180 and 181 and the associated vacuum chambers 180 and 181 , tape reel 200 and 201 additional tape loops could. In other words, it means being educated. If only step-by-step operation is carried out, so that the two vacuum chambers 180 and 181 do not have to be provided with pressure regulating devices for pressure equalization by the pneumatic 198 , the outer vacuum chambers 197 and 181. Brakes 186 are decoupled from one another. Before there is also a higher tape storage capacity than the pressure equalization begins, the tape loop in the inner vacuum chambers 180 and 181 is not in the vacuum chamber 181 into which the tape is required. Instead, prevails in the outer Va 40 forward direction has been introduced, slightly longer than kuumkammern 197 and 198, a constant sub-band loop The pressure in the vacuum chamber 180. The two vacuum chambers 197 and 198 The reason for this is the stepping motion. The have a low storage capacity, the only negative pressure at the closed end of the vacuum for the implementation of a rapid sequence of chamber 181 is briefly somewhat higher than the lowering steps must be sufficient. For a continuous pressure in the 45 vacuum chamber 180.
Borrowed operation must, however, also the external vacuum Before the pneumatic brakes 186 released Werkuumkammern 197 and 198 with the in F i g. 6, however, a small piece of tape will be provided from the provided pressure regulating device, the vacuum chamber 197, in which a constant negative pressure prevails depending on the tape sensors in the inner Va-. At the same time, the vacuum chambers 180 and 181 will work. These processes 50 vacuum chamber 198 by exercising a constant are already in connection with FIG. 3 explains how a piece of tape of the same length is tied into it. In both modes of operation, the tape feed reel 200 and the tape take-up reel 201 are pulled through the small vacuum chamber 181. This rotates the belt loop back into its servo drives 202 and 203 . This servo brought the original position. The sub-drives 202 and 203 are thus balanced against one another by pressures signals before the pneumatic controls, which release the brakes 186 in the outer vacuum chambers. Deliver with other 197 and 198 provided tape sensors. Expressed in words, this means that the external

The step-by-step operation of the arrangement is at the vacuum chambers 197 and 198, in which a constant

best understandable when there is an actual negative pressure sequence while stepping for

considered from operating states which, when occurring 60, compensate for the states of the internal vacuum

provide a command signal for the sliver antechambers 180 and 181 step by step. The servo drives 202

upward movement occur. This command signal is and 203 only come into action if after a

z. B. a rectangular voltage pulse with negative series of step movements in one direction

Polarity and with a length of one millisecond. Belt loops in the outer vacuum chambers 197

At the end of this period the tape extended the opening 65 and 198 by a noticeable amount or

take speed of about 254 cm / sec have been reduced.

suffices. These values apply to those with a single-For continuous operation in both directions

results actually achieved. At the end of the, the command signals FORWARD and BACK can be used

also have a rectangular shape; they occur with negative polarity during the entire period of movement on. At the end of this period, the negative trailing edge of the command signal is effected pneumatically braking as has been described. In addition, the tape will stop quickly. the Backward movement of the belt is prevented except for a small percentage of the distance covered. The rest of the system works like that in FIG. 3 shown as an embodiment system with continuous Belt movement at a regulated speed.

From the above it should be apparent that with the help of the tape drives described and in particular Stepper drives are possible, one after the other with data bits on a tape or magnetic tape a density of 394 bits / cm to record or read from this, even if the The nominal speed of the belt is 254 cm / sec. At the same high speeds can also Bit / cm can be achieved. Thus, in the field of step-by-step magnetic tape recording, there is one significant improvement achieved. In this context it should be noted that with the invention achievable data density and the recording and playback speed at gradual working tape drives with the sophisticated punch card or tape devices that have been used up to now by far exceed the achieved values.

Claims (10)

Patent claims: 1. Tape drive, especially for magnetic tape devices, for transporting a tape at a controlled speed in a predetermined direction from a tape supply reel on a z. B. from recording and playback head existing magnetic head assembly over on a tape take-up reel, with at least one arranged between the magnetic head assembly and a tape reel each vacuum chamber, the vacuum is changed with a jointly coupled to the vacuum chambers reducing valve and in which a device for determining each in her formed tape loop length is provided which controls a servo drive for the respectively assigned tape reel to maintain a predetermined loop length, characterized in that the negative pressure difference in the vacuum chambers generated by the reducing valve (32) causes the tape to be transported past the magnetic head arrangement (18) and the circuit ( 44, 46, 48, 50, 52, 54) regulates the pressure difference in the vacuum chambers so that the belt speed is constant. 2. Belt drive according to claim 1, characterized in that the circuit for the control the pressure difference includes switching means (50, 54) which correspond to one of the desired The command signal, depending on the direction of belt movement, reverses the polarity of the reducing valve (32) cause controlling error signals. 3. tape drive according to claim 1 or 2, there-: characterized in that the circuit for Control of the pressure difference contains a frequency discriminator (44), the frequency of a Time reference signal taken from the magnetic tape with the frequency of a quartz stable Oscillator (46) compares and the fluctuations of the time reference signal and thus the tape speed corresponding error signals generated. 4. Belt drive according to one of claims 1 to 3, characterized in that the through their pressure difference causing the tape to be transported past the magnetic head assembly (18) Vacuum chambers each have a recess in their back wall perpendicular to the belt surface (42), the cross-section of which increases with the length of the belt loop and one with the Belt loop length allows increasing secondary air flow. 5. Tape drive according to claim 4, characterized in that in one side wall of each of the vacuum chambers (24, 26) causing the tape to be transported past the magnetic head arrangement (18) by their pressure difference, an elongated light source (37) and in the respective opposite side wall a strip ( 38) made of photoelectric material is present. 6. Tape drive according to one of claims 1 to 5, characterized in that when using the respective tape reel associated first vacuum chamber and between this and the respective associated tape reel provided second vacuum chamber with a larger volume than it has the adjacent first vacuum chamber in the second vacuum chambers (66, 68) reducing valves (82, 84) for controlling the belt loop length in the first vacuum chambers (60, 62) are provided and that the second vacuum chambers (66, 68) each with a device (94) for determining the in them each existing belt loop length are provided. 7. Belt drive according to one of the preceding claims, characterized in that the reducing valves (32 in Fig. 1; 82, 84, 78 in Fig. 3) each consist of one at the closed end of each vacuum chamber (e.g. 162 in Fig. 6), which can be deflected electromagnetically by a voice coil (170) and a magnetic core (175) , which is provided with a small central through-hole (167) and through its deflection, the membrane (166, 168 ) provided by the suction pump (34 and 76, respectively) ) controls the sucked air flow in such a way that a vacuum change occurs in the vacuum chamber (162) , which results in the tension change on the belt loop. 8. Tape drive according to claim 6 or 7, characterized in that the first vacuum chambers (180, 181) , which by their pressure difference keep the tape speed constant, on their outer side facing the magnetic head arrangement (182), a tightly seated, loudspeaker-like membrane (188 in F i g. 8), the interior of which is connected to the interior of the respective vacuum chamber and whose voice coil can be controlled by braking pulses in such a way that the membrane (188) increases its interior volume after an operating step has been carried out and thus the in the associated vacuum chamber (180; 181) located magnetic tape to the inner wall this vacuum chamber (180,181) sucks. 9. Belt drive according to claim 8, characterized in that the voice coil of the membrane (188) to a high-pass circuit (194) and a rectifier arrangement (195) comprising Circuit is connected, the command signals supplied by it the trailing edges to control the voice coil. 10. Belt drive according to one of claims 1 to 6 and 8, in particular to complement one magnetic tape drive operating with friction waves, characterized in that in the Tape path inserted between each vacuum chamber and its associated tape reel (118, 120) second vacuum chamber with larger compared to the volume of the first vacuum chamber Volume of the negative pressure in the respective second vacuum chamber is kept constant. 1 sheet of drawings 009585/320