DE7613359U - Device for generating tape tension In a magnetic tape transport according to the contact winding principle - Google Patents

Description

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BASF A ^ tieng ^ s ^ ilFic

Our reference: OZ 31 950 De / Gl M 6700 Ludwigshafen, April 26th, 1976 J

Device for belt tension generation in one Iiagnetbandtransport according to the contact winding principle

The invention relates to a device for generating belt tension in a magnetic tape transport according to the contact winding principle, essentially consisting of winding and unwinding rollers and at least one rotating drive roller for simultaneously driving both rollers in contact with one elastically deformable peripheral edge of the drive roller, the drive roller and the take-up and unwinding rollers on 'Mounted rotatable shafts and the shafts of the rollers are movably arranged with respect to the stationary shaft of the drive roller and the pressure forces at the contact points between the take-up and unwinding rollers and the drive roller are different are large and a differential pressure force occurs to generate the belt tension in the belt section between the contact points.

In general, tape transport systems that use unwinding and take-up rollers simultaneously by surface contact between a drive roller and the peripheral edge of both Belt rollers are driven, the presence of a bard tension in the tape section between the supply and take-up reels. .-x This belt tension enables the formation of a flangeless Core to be wound tape lap, which retains its shape even without lateral support and also the high speeds and can withstand strong accelerations and decelerations that are normally found in this type of device.

Some tape transport systems of the general type mentioned at the beginning Type also require constant tape tension in order to achieve even contact between magnetic head and tape ^ d in this way to enable a flutter-free signal to be picked up.

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An example of such a tape transport device is described in German Offenlegungsschrift DOS 2,436,008. the Tape tension in the tape transport device described there is almost completely due to the braking of the unwinding roller serving role achieved.

Such known tape transport systems are generally based almost exclusively on the phenomenon of differential Deformation. Another example of such a tape transport device is shown in U.S. Patent 3,370,803 described. By using an elastic material on the drive roller circumference and by applying a higher one Pressure force between the unwinding roller and the drive roller is a deformation difference of the at the two contact points Drive roller circumference reached, which the belt tension in the belt section between supply and take-up reels.

On the one hand, in a belt transport system in which only the principle of differential deformation is used, frequent belt loops, especially between the supply reel

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Unwinding side. If these loops are not eliminated, the tape transport stops. Such belt loops can for example, if a new roll of tape - ■ has never been transported through the tape transport, is placed on the unwinding shaft or if a roll of tape is used for a long time before it is used in the tape transport was stored and has therefore become "soft".

In such cases, the required pretensioning of the tape is only achieved when the tape is transported has gone through several times. Especially in the time before a sufficient belt tension is achieved, the above seem to be to form the loops mentioned above. Another disadvantage of one

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Belt drive system in which only the differential deformation principle is used to generate the belt tension, can be seen in the fact that such a drive has considerable cyclical fluctuations in the belt tension, which on a "blow" of rotating parts. Any such "hit" of the drive roller or the belt rollers and - whole in general - with "satellite arrangements", which is based on tolerances of the concentricity of the roll cores, the tape laps or bearings etc., causes a change in the radial force at the contact points between the drive roller and the satellite belt rollers. There are also deviations in the hardness of the elastic material of the drive roller peripheral edge (rubber tire) - which may be due to manufacturing tolerances, wear and tear, flats, etc. - fluctuations in the tape tension and thus flutter disturbances in the sampled signal.

As already mentioned, the generation of a stable pressing force, which is exerted on the drive roller by both "satellite rollers", is of the greatest importance for achieving reliable belt running with low flutter disturbances and small fluctuations in the belt tension. Belt drive systems based on the above-mentioned principle of differential deformation are therefore particularly sensitive to any change in the pressure force acting between the drive roller and the belt rollers - due to the fact that in such drive systems the belt tension is determined by the difference between these forces acting at the two contact points is produced.

The already mentioned German patent application DOS 2 ^ 36 specifies a tape transport system in which some of the disadvantages mentioned above are reduced by braking the unwinding roll will. This system uses a pair of unidirectional brakes, one on each f Shaft that inhibits the rotation of the drive roller when this roller acts as a supply roller, whereas it is at Use the roll as a take-up roll to allow free rotation.

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The forces that the unwind and take-up reels are in the direction of urge on the drive roller are essentially the same size for every significant difference in deformation as well as avoiding the above mentioned problems caused thereby. The problem of looping, that occurs with loose tape wraps is essentially eliminated here, and so are the "flapping" problems. the Brakes that act in one direction work with a variable braking characteristic at the point of drive contact between the unwinding roller and the drive roller without regard to the diameter of the unwinding roll generates a more or less constant braking force. This characteristic of the varying The application of force results in an almost constant tension profile in the winding roll produced.

A disadvantage of the system, which is based only on the deceleration of the unwinding roll to maintain the belt tension, However, it is necessary to drive a drive roller, which in turn to drive a decelerated unwind roller, more energy is required.

As can be seen, reliance solely on one of the two tension-creating or tension-maintaining ones Means serious drawbacks with it. The combination of both effects can reduce the respective disadvantages to a certain extent Cancel degree. Known arrangements in which both effects are combined, however, either have new disadvantages or the disadvantages mentioned above are only inadequately eliminated.

Incidentally, the brake is a constant torque device that causes an increase in the force required to Drive of the unwind roll required on its periphery

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is, the diameter of this supply roll decreasing during the tape transport. Such an increase in driving force can decrease the speed of the drive roller due to the increasing load on the drive motor result. In video tape recording and playback systems, however, even low tape speeds are highly undesirable and must be avoided.

A belt transport system with brakes that also act in one direction to compensate for the changing roll diameter used in conjunction with the principle of differential deformation is disclosed in U.S. Patent '- "■' 3 482 800. In this system, the brakes inhibit however, the rotation of the supply reel is only such that the load on the drive roller motor remains constant to also reduce the Keeping the speed of the drive roller constant despite changing the diameter of the unwinding roller. By means of additional Torque motors is the different deformation, which the predominant contribution to the maintenance of the Represents tape tension generated.

This known system overcomes the disadvantage of de, ^ with U.S. Patent 3,638,888n. Since the However, they do not primarily brake the generation of the belt tension, but rather only slow down the rotation of the supply reel cause the load on the drive roller motor to be kept constant while the If the diameter of the unwinding roll changes, the problem of flapping faults of components and their effects on the remains Maintaining a constant tension by means of differential deformation, also unresolved.

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The object of the present invention is to provide a device for a tape transport device of the type mentioned at the beginning To provide kind which avoids the disadvantages mentioned above.

The task is with a device for tape tension generation in a magnetic tape transport according to the contact winding principle, consisting essentially of winding and unwinding rollers as well as at least one rotating drive roller for the simultaneous drive of both rollers in contact with an elastically deformable peripheral edge of the drive roller, whereby the drive roller and the winding - and AbwickeLrolle mounted on rotatable shafts and the shafts of the rollers are movably arranged opposite the stationary shaft of the drive roller and the pressure forces at the contact points between the winding and unwinding rollers and the drive roller are different and a differential force occurs to generate the tape tension in the tape section between the Contact points, solved according to the invention by brakes, which are arranged on each of the shafts for the winding and unwinding roll and which is only effective in the direction of rotation of the unwinding on the shaft of the respective unwinding roll, The brakes serve to generate the first belt tension component in the belt section and pressure force generation devices ₉ which are provided on each of the shafts and which cause the pressure force generation between the rollers and the drive roller, the pressure force generation devices depending on the respective rotary devices of the shafts between the winding roller and the drive roller cause greater pressure than between the supply roller and the drive roller. Surprisingly, this also makes it possible to detect fluctuations in the differential deformation on the circumference of the

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Drive roller, which are caused by the changing roller diameter, to compensate. Because it has found that under such conditions, as the tape roll diameter changes, there is also a change the deformation occurs at the peripheral edge of the drive roller.

Attempts to do this have produced the unpredictable result that a larger roll of tape is required for the same pressure force causes less deformation on the drive roller than a smaller one. As the deformation changes, it changes also the belt tension generated by it. In order to maintain a constant belt tension, therefore, do not have to constant, but varying pressure forces are used to keep the unwinding and winding rollers against the drive roller to press.

The tape transport device according to the invention is essentially designed in the same way as described in the German ^{patent application DOS 2 J} i36 0Q3 = The problems-effect

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The following are summarized and explained using a such known transport. The unwinding and winding rolls are rotatably mounted on e.g. slidingly mounted slides. The one provided between the two carriages Springs work together to create a force, polygamy pulls the rollers in the direction of the drive roller. In contrast to the Brakes of DOS 2 ^ 36 008 acting on the shafts are used the braking / pressure force systems on each of the two shafts here two different purposes. The braking effect of the braking / pressing force generation systems only works in one direction, so that only the rotation of those shafts is inhibited

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the respective unwinding roll carries. The braking force decreases with the diameter of the tape roll of the supply reel, thus the force is maintained which is necessary to propel the rollers at a practically constant speed. As previously explained, this constant driving force facilitates the operation of the drive roller with more uniformity Speed and also contributes to an almost constant belt tension component with the help of the braking effect to create. In contrast to the DOS 2 436 008 The brakes described generate the braking / pressing force generation systems of the present invention a pressure force acting on one side in the direction of the drive roller, which complements the above-mentioned, jointly acting spring forces. The braking / pressing force generation systems are designed in such a way that the unit attached to the take-up shaft has a much larger unit towards the drive roller directed force generated as the unit arranged on the unwinding shaft. The one-sided towards the drive roller acting force decreases with the diameter of the take-up roll and this helps to compensate for the Change in aer verrormung aes umiangrana.es of the drive roller to create, which is caused by the change in the tape roll diameter. The result is one significantly more uniform differential deformation of the drive roller periphery than one through differential deformation alone Deformation generated by pressing forces.

To further reduce the drive roller deformation as a result of the change in the roller diameter, a Drive roller of the type specified in DOS 2 436 008 can be used. The influence of the changing The tape roll diameter is continued by the

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Reduced the use of a drive roller whose peripheral edge - despite its radial deformation, which is the influencing the belt tension according to the principle of differential deformation - sufficient in the circumferential direction Has stiffness in order to weaken the difference in deformation that would otherwise change due to the changing Tape roll diameter would result.

Further details of devices according to the invention are contained in the following description of an embodiment shown in the drawing. In the drawing is shown in

Fig. 1 is a perspective view of a tape transport device according to the invention.

FIG. 2 shows the tape transport device of FIG. 1 from below as well as the arrangement of the braking devices.

Fig. 3 is a perspective view of one of the brake / Correction generating facilities.

Fig. ¹ I shows various alternative designs of the braking / Andruckkrafterzeugungs devices.

Fig. 5 shows a further embodiment of the drive roller.

In Fig. 1 and 2, the drive roller 1 is rotatably mounted on the base plate 2 and can be clockwise by the motor 3 or counterclockwise. The carriages 4 and 5 slide on the base plate 2 mounted to have an almost smooth, rectilinear movement towards and away from the drive roller 1

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allow. The shafts 6 and 7 are rotatably mounted on the carriages 4 and 5, respectively. The hollow cores 8 and 9 are shown with tape rolls 10 and 11 wound up. A tape section 12 extends from the tape roll 10 around the tape guide 13 and past the magnetic head Ik to the tape roll 11. Due to the pressure forces between the tape rollers and the tape drive roller, which are primarily generated by the springs 15, it is possible to use the Drive tape roll by contact pressure of their Urafangrandes with the edge of the drive roller. The tape 12 is transported from left to right in the drawing when the drive roller 1 ^ rotates clockwise and in turn drives the tape rollers 10 and 11 counterclockwise by engaging with their peripheral edges. The tape transport from right to left is achieved by driving the drive roller 1 in a counterclockwise direction.

Fig. 2 shows the mirror image arrangement of the brake / pressure " force system. Brake bands 16 and 17 attached to the base plate 2 are around the brake drums 18, 19 on the shafts 6.7 laid around and at the ends of the springs 20 frzw. 21 attached. The springs 20, 21 are in turn on brackets 22, 23 attached, which proceed from the movable carriages 4, 5. -. The tension of the springs 20 and 21 depends on the size of the respective Tape roll diameter. A large roll of tape increases the length of the spring compared to the length that the Spring with a small roll of tape to the distance which the carriage from its position with a small roll travels until it reaches its position in a large role. The magnitude of the voltage can be mathematically as follows

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express the measure: t = t + KAx, where t is the voltage of the

SO S

Spring, t is the preload of the spring in a position of the slide that corresponds to a small roller diameter (in
hereinafter referred to as "small roller position"), K is the spring constant and Δχ is the distance that the carriage takes from its
Small rolls from up to its large roll position. J ₁

Couplings acting in one direction only (in the drawing
not shown) between shaft 6 and brake drum 18 or
between shaft 7 and brake drum 19 allow each of the
Waves, a rotational movement unhindered by their drum *
while the roll of tape connected to this shaft serves as a take-up roll. As long as this is the case
stands the one cooperating with the roll of tape to be wound up
The brake drum is still due to the action of the brake band, and (

the spring tension is essentially unchanged from FIG

Transfer the end of the brake band towards the base plate. The f

Presence of the voltage between the base plate 2 and the R

The carriage generates a supplementary pressure force which |

close the take-up roller in the direction of the drive roller | moves away, this force being the tension of the brake band spring

is equivalent to.

On the other hand, if a reel of tape works as a supply reel, then be; j

If the coupling connected to it acts the simultaneous S

Rotation of drum and shaft. As a result of the frictional contact it;!

between the tensioned brake band and the rotating ν

Drum, the counteracting force is not just Sr

endeavors to brake the tape roll acting as an unwinding roll, |;

but also reduces the tension on the one with the basic |

plate 2 connected end of the tape. While the fundamental! ■

plate end of the brake band in the prevailing voltage essential h

tie

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chen is equal to the spring tension, if the corresponding If the tape roll works as a take-up roll, this tension is significantly lower at the end of the brake tape on the base plate side than the spring tension in a tape roll acting as a supply roll. With the same diameter of the unwinding and the For winding rollers, the winding roller is therefore pressed against the drive roller with greater force than the supply roller. This force differential creates the differential deformation of the drive roller which is the first of the belt tension components results. As already mentioned, the second Banc tension component is generated directly by the deceleration of the unwinding reel generated.

If the tape roll diameters change, the values of the braking and pressure forces also change in such a way that the Deformation of the drive roller and the force required to drive the unwinding roller are kept almost constant will. These measures represent an important aspect of the invention Knowledge. For example, US Pat. No. 3,370,8O4 describes a pressure force generation system, in which the belts looped around both shafts carrying the belt rolls are expressly used for the purpose to pull the waves in the direction of the drive roller or away from it, depending on whether the shaft in question the Take-up or the supply roll carries. In the pressing force generation system described in this US patent specification however, it lacks several important features of the measures of the present invention. Quite apart from the fact that nier No brake drum is provided for generating correspondingly large braking forces, the shafts even have cross-sectional reductions in order to reduce the braking effect. Besides that The known device lacks the feature of the force acting only in one direction, due to which the braking

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effect on the shaft of the take-up roll is completely canceled / /. What matters most, however, is the fact that neither the clamping force nor the braking effect, insofar as these effects are present at all, change with the roll diameter.

In the present braking / pressure force generation system, the respective contributions and rates of change of the braking and pressure force effects can be adjusted by relocating the fastening points of the belt ends on the base plate side or their springs, or by both measures. Fig. IJa shows alternative fastening points for the belt ends on the base plate in order to reduce the one-sided, shifting tension force that comes into effect at a given braking value. If, for example, the bands are attached to points B instead of points A, the direction of pull of the brake bands is no longer parallel to the carriage movement as in FIGS no longer merely equal to the tension in the ends of the belts on the base plate side, but now only corresponds to the belt tension component, the pressure force is reduced, which still comes into effect in the direction of the slide movement, i.e. t ^ cos O, where t. represent the tension at the end of the belt on the base plate side and 6 the angle enclosed by the belt and the direction of the carriage movement. A similar result would result if the straps were fastened in points C.

The relocation of the tape attachment points also affects dis Rate of change of the one-sided application of pressure force and braking. The tension of the spring can be

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by the formula t = f „+ K.A.y, where Δ y is the

S O

Is the amount by which the spring is stretched when the with it connected carriage moves away from the position corresponding to the small roll diameter. A geometric one Consideration results in the following equation:

j / 7ab) ² + (χ + ΔΧ) ² - I / (ab) ² + X ²

is therefore not simply equal to Δ X as in FIGS. 1 to 3, in which 6 is equal to 0 °, but the speed of the changes in the unilateral application of pressure force and braking resulting from changes in diameter is reduced here.

Fig. ¹ Ib shows a band arrangement which increases the one-sided application of pressure force at a given braking force. Here both the base plate side band and the spring are attached to the base plate 2, and the force component acting in the direction of the drive roller increases because the spring tension contributes both to increasing this one-sided pressure force and to increasing the tensile stress at the base plate side of the belt end. It is also important with this arrangement that the speed at which the braking effect or the pressure force effect changes is effectively doubled, since the tensile stress of the spring changes according to the equation f_ = f + ΖκΑχ and not as in the exemplary embodiment according to FIGS 3 according to the equation f = f + κΛχ-changes.

Undoubtedly, the attachment points on the baseplate side Band ends and the spring in the embodiment shown in Fig. 4b similar to that shown in Fig. 4a

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Relocated to the relative impact on the example Adjust the braking or clamping force effect even further.

To maintain the improved tape transport an essentially constant belt tension in the belt section between the unwinding and winding rollers To promote further, a drive roller can be used that has specific features. That of that driving role The criterion to be fulfilled is a minimal change in deformation for a constant pressure force with changing Tape roll diameter η.

The physical properties required to meet this criterion are flexibility in the radial direction and Rigidity in the circumferential direction. The radial flexibility enables the desired local acceleration of the drive roller periphery, while the stiffness in the circumferential direction is the change in such an acceleration, insofar as it changes results from the contact of the drive roller with a tape roller of changing diameter, reduced to a minimum.

Fig. 5 shows an embodiment of a drive roller which has the desired properties. The driving role consists of a rigid inner roller core 24, the periphery of which is covered with a 1 mm thick elastic rubber covering 25 is provided, which is still four or five about 6 / um (micrometer) strong adhesive tape made of Mylar has 26 layers (belt) (Mylar® is a for the DuPont company, USA registered trademark.) With the German Offenlegungsschrift DOS 2 435 008 is a special drive roller construction described with either at all

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no or only a negligible rubber coating is placed around a rigid inner roller core, around the frequency response to improve the tape transport device. Only with the present invention is surprisingly found that the Mylar® layers have the above-mentioned important further advantage of reducing the on the change in Band roll diameter based, known from the older elastic drive rollers her deformation with it bring.

Tests in which a tape transport device was used that was either compatible with only the variable braking / pressing force generating devices or were additionally equipped in connection with the drive roller described here, yielded a much more uniform belt tension than that achievable with prior art systems, where the numerous disadvantages explained at the beginning were avoided.

From the detailed description above, sahi realms can be identified Modifications oaer ÄDY / eiuhuii £, eii iicx-lcitcn, uic however correspond to the meaning and scope of the following protection claims. In the exemplary embodiment in FIG. 5a, for example, there is a drive roller shown, which is surrounded by five layers. Of course, this number of layers of adhesive tape must not be limited Senses are grasped. Satisfactory results have also been achieved, for example, with drive rollers with more than five layers, e.g. ten layers, were provided.

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Claims (12)

- 17 - "" ö; z. 3 Protection claims ^ l 1. Device for generating tape tension in a magnetic tape transport according to the contact winding principle, essentially consisting of winding and unwinding rollers and at least one rotating drive roller for the simultaneous drive of both rollers in contact with an elastically deformable peripheral edge of the drive roller, the drive roller and the winding and unwinding rollers mounted on rotating shafts and the shafts of the rollers are arranged movable relative to the stationary shaft of the drive roller and miscellaneous the pressing forces at the contact points between the winding and unwinding rollers and the drive roller are large and a difference force occurs to produce the tape tension in the tape section between the contact points, characterized by brakes which are arranged on each of the shafts for the winding and unwinding roll and which are only effective in the direction of rotation of the unwinding on the shaft of the respective unwinding roll, the brakes for generating g of the first belt tension component in the belt section and tensioning force generating devices which are provided on each of the shafts and which generate the pressing force between the rollers and the drive roller, the tensioning force generating devices depending on the respective directions of rotation of the shafts each causing the greater pressing force between the winding roller and the drive roller than between the tapping roller and the drive roller. 2. Apparatus according to claim 1, characterized in that the brakes have such a variable braking characteristic that the pressure force necessary to drive the unwinding roller is constant on the circumference of the unwinding roller during its decrease in diameter when the tape is running. - 18 - 7613359 25.1176 - 18 - - '". \ Q \ z'; ,, ii 56o i *.» ^: 3. Device according to claims 1 or 2, characterized in that each Andruckkrafterzeugungseinrichtung produces such a variable pressure force that the deformation of the drive roller circumference at the contact points with the rollers at an approximately constant value with changes in diameter of the rollers during the tape run. 4. Apparatus according to claim 1 and one or both of claims 2 and 3, characterized by the use of a drive roller in the tape transport with a peripheral edge which is flexible in the radial direction and rigid in the circumferential direction. 5. Device according to claim 4, characterized in _a that the drive roller of a rigid core with an elastic rubber pad is outside the periphery and having a further layer of polyethylene terephthalate. 6. Device according to one or more of claims 1-5, characterized in that the brakes and pressure force generating devices each form a unit on each of the two shafts of the tape rolls. 7. Apparatus according to claim 6, characterized in that the braking and pressure force generating unit comprises the following parts: a brake drum, which is arranged coaxially around the shaft, a brake band with two end pieces, of which the first end piece is attached to a tension spring ₉ which in turn is connected to the movably mounted carrier of the associated shaft and of which the second end piece directly to the chassis of the belt transport connected is, - 19 - 7613359 11/25/76 - 19 - OZ 31 96ο L and wherein the brake band is itself wrapped around the brake drum in frictional contact therewith, thereby causing movement The shaft in the direction away from the drive roller causes the length of the brake band and thus the tension in the mainspring is increased by an amount less than or equal to the path of movement of the shaft corresponds to the drive roller away. 8. Apparatus according to claim 7, characterized in that the other end of the tension spring is attached to the chassis of the tape transport. 9. Apparatus according to claim 7 or 8, characterized in that each of the braking and pressure force generating units comprises a one-way clutch which is arranged between the brake drum and the shaft, so that the shaft is in one direction independently of the brake drum, in the opposite direction, however, can only rotate together with the brake drum. 10. Apparatus according to claim 9, characterized in that _a rotational direction in which the clutch allows a free rotation of the shaft, the direction of rotation of the shaft in which the web roll serves as a take-up roll. 11. The device according to one or more of claims 7 to 10, characterized in that the part of the second brake band end piece between the brake drum and the chassis is arranged essentially parallel to the movement path of the associated shaft to and from the drive roller. - 20 - 7613359 25.1176 - 20 - 0 '. ¹ line * 31 9'6Ο " 12. The device according to one or more of claims 7 to 10, characterized in that the part of the second brake band end piece between the brake drum and chassis encloses an angle with the direction of movement of the associated shaft to the unrt of the drive roller. BASF Aktiengesellschaft Sign. 7613359 25.1176