US3580526A

US3580526A - Apparatus for storing and winding discontinuously and reversibly moving tape

Info

Publication number: US3580526A
Application number: US855550A
Authority: US
Inventors: Michel Wichoud; Jean Pierre Engel
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-09-06
Filing date: 1969-09-05
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25
Also published as: GB1244896A; DE1945800A1; FR2017509A1; CH498763A

Abstract

In apparatus for storing and winding tape travelling discontinuously and reversibly through a reading unit and comprising drive means for reversibly driving the tape through the reading unit and a pair of reversibly driven spools off which and on to which the tape is wound, the provision of a takeup system, including a pair of pulley arrangements on opposite sides of the drive means, responsive to variations in the length of the tape paths between the spools and the drive means, and electrical means controlled by the takeup system to restore the proper driving relationships between the spools and the tape as it passes through the reading unit.

Description

United States Patent Inventors Michel Wiehoud 1, rte de Drize 1227, Geneva; Jean Pierre Engel, 3, Rue Schaub 1202, Carouge-Geneva, both of, Switzerland Appl. No. 855,550

Filed Sept. 5, I969 Patented May 25, 1971 Priority Sept. 6, 1968 Switzerland 13432 APPARATUS FOR STORING AND WINDING DISCONTINUOUSLY AND REVERSIBLY MOVING TAPE 6 Claims, 6 Drawing Figs.

US. Cl

318/7 Int. Cl 1365b 53/3}, G03b1/04,G11b 15/32 Field of Search 242/ l 79- [56] References Cited UNITED STATES PATENTS 3,115,314 12/1963 Manley et al. 242/187 3,251,048 5/1966 Killen 242/188X 3,318,546 5/1967 Bejach... 242/190 3,488,696 1/1970 Klang 242/190 3,523,655 8/ 1970 Bevis 242/190 Primary Examiner-Leonard D. Christian Attorney-Waters, Roditi, Schwartz and Nissen ABSTRACT: In apparatus for storing and winding tape travelling discontinuously and reversibly through a reading unit and comprising drive means for reversibly driving thetape through the reading unit and a pair of reversibly driven spools off which and on to which the tape is wound, the provision of a takeup system, including a pair of pulley arrangements on opposite sides of the drive means, responsive to variations in the length of the tape paths between the spools and the drive means, and electrical means controlled by thetakeup system to restore the proper driving relationships between the spools and the tape as it passes through the reading unit.

P'atentea may 25, 197i 5 Sheets-Shoot 1 FIG.

'atemd Mg 25, 1991 3,580,526

5 Sheets-Sheet 2 Patented May 25, 1971 3,580,526

5 Sheets-Sheet 8 FIG. 3

H HUDUUUD r Q o\ 1 In u u u u u n Patented May 25, 1971 5 Sheets-Sheet l 2 max max' FIG. 5

puma. May 25, 1911 5 Sheets-Sheet 5 APPARATUS FOR STORING AND WINDING DISCONTINUOUSLY AND REVERSIBLY MOVING TAPE This invention is concerned with the storage and winding of tape adapted to travel, past a reading unit or a working station, in an intermittent or discontinuous manner and adapted to have its direction of travel reversed instantaneously.

Although a length of tape can, because of its low inertia, stand abrupt accelerations and decelerations, in particular instantaneous reversals of its direction of travel, the same does not apply to the tape storage members, i.e. spools, which have an inertia that is dependent on the extent to which they are filled and whose-speed cannot abruptly be modified nor, with even greater reason, be instantaneously reversed.

Such a problem may for instance occur when designing magnetic tape sound reproduction apparatus, motion picture projection or filming apparatus and programme reading apparatus for controlling various machines, or with certain tape readers used in computer peripheral equipment.

It has already been proposed, in particular in connection with motion picture apparatus, to provide a loop of film between each of the film spools and the film reading unit, i.e. in the region of the illumination path and the film engaging sprocket'teeth.

Although this idea does in fact enable continuous winding on or off of tape to be reconciled with discontinuous travel thereof within a reading unit, it does not however enable the direction of movement of the tape to be reversed instantaneously when its speed of travel has become substantial.

An increase in the size of the tape loops might therefore be thought to be an appropriate idea but this would mean having to provide special means for their storage while in motion.

An object of the present invention is to avoid such a requirement.

According to the present invention there is provided apparatus for storing and winding discontinuously and reversibly moving tape, comprising a pair of holders for supporting a pair of tape spools; a pair of reversible motors for'reversibly driving said holders whereby said spools may be alternately receiving and delivering; tape reading means in the path of said tape between said spools; drive means for driving said tape as it enters and as it issues from the reading means; a tape takeup system in the path of said tape for temporarily modifying the length of first and second portions of said path between said drive means and said spools; first supply means actuated" by said system and adapted to supply, for each of the spools, a first electric index voltage dependent of the length of the corresponding one of said tape path portions; second supply means associated with each of said spool holders and adapted to supply, for each of the spools, a second electric index voltage dependent on the radius of the last turn of tape wound on the corresponding spool; and electronic circuit means having a comparing element 'for each spool and adapted to tie the speeds at which said motors drive said spool holders to the corresponding ones of said first and second index voltages; the arrangement being such that under continuous-duty operating conditions of the apparatus, the tape can unwind off the delivering spool and can be wound on the receiving spool at a linear speed equal to that at which it is driven by said drive means, with said first index voltage remaining constant and said second reference voltage, which is variable, progressively modifying the angular speed of the spool associated therewith, and such that any modification in the length of the tape along said path portions causes the takeup system to come into operation and a corresponding variation of the first index voltage to occur which triggers off transitional operating conditions tending to restore said tape path portions to-their previous length under continuous-duty operating conditions.

In the accompanying diagrammatic drawings:

FIG. 1 is a front elevation of one form of embodiment of the apparatus provided by the invention;

FIG. 2 is a side elevation of the apparatus shown in FIG. 1, on a larger scale; 1

FIG. 3 is an axial section, along line III-III of FIG. 4 and to a larger scale, of part of the apparatus shown in FIGS. 1 and 2;

FIG. 4 is a section taken along line IV-IV of FIG. 3;

FIG. 5 is an explanatory graph illustrating the operation of the apparatus shown in FIG. 1 and 2; and

FIG. 6 is a diagram of an electronic circuit used in the apparatus shown in FIGS. 1 and 2.

The apparatus shown in FIG. 1 comprises a baseplate l on the front side of which are mounted two delivery cum receiving

spools

2 and 3 carried and driven by rotary supports 21 and 31 and containing a tape 4; a drum 5, having a rotary shaft 51, for driving the tape intermediate the two spools; two sets 6 and 7 of pulley arrangements lying in the path of the tape, each between one of the

spools

2 and 3 and the driving drum 5; two feelers 8 and 9 pivotally mounted on pins 81 and 91 and carrying at their free ends follower rollers which come to bear under the action of springs 10 and 11 against the outermost turn of tape that is wound on the associated spools. The two sets of pulley arrangements are made up of four

rollers

61, 62, 63 and 64, and of four

rollers

71, 72, 73 and 74, respectively, that are mounted for free pivotal movement on the baseplate and of three rollers 65, 66 and 67, and of three

rollers

75,76 and 77, respectively, that are mounted for free pivotal movement also on

arms

12 and 13. .In each of these sets, the tape 4 alternately passes over one of the rollers that are pivotally mounted on the baseplate and over one of the rollers that are pivotally mounted on an arm.

Arms

12 and 13 are mounted on

pivot pins

121 and 131 and are subjected to the action of tension springs 14 and 15 having one end secured to the arms and having the other end secured to the baseplate 1.

In the illustrated form of embodiment of the apparatus, which is adapted to read information for the control of a machine, in particular a knitting machine, the baseplate 1 carries a unit 17 for reading the information recorded on the tape 4.

On the reverse side of the-baseplate are mounted, as shown by FIG. 2, a motor 18 for driving the drum 5; potentiometers l9 and 20 having control pins that are common with the pins 81 and 91 of feelers 8 and 9; potentiometers 22 and 23 having control pins that are common with the

pins

121 and 131 of

arms

12 and 13;

motors

24 and 25, each fitted with reduction gearing, for driving

spools

2 and 3; and a drive unit 26 for moving the tape through the reading unit 17.

The supply terminals of

motors

24 and 25, of motor 18, of drive unit 26, and of

potentiometers

19, 20, 22 and 23, are connected by leads, not shown, to connectors that are mounted on a bus bar 101 secured to the back of the baseplate 1. Other leads, not shown, connect some of the connectors 100 to the electronic circuit shown in FIG. 6.

This electronic circuit which is transistorized, can be mounted on a support that can either be secured to the base plate 1 or be separate therefrom.

Upon issuing from one of the spools 2 and 3 (the delivery spool), the tape 4 is fed to the drum 5 via the corresponding set of pulley-arrangements. It then cooperates with the drum a first time and then proceeds along a loop-shaped path towards the reading-unit 17 through which it passes. Upon issuing from this reading unit, the tape proceeds back to the drum along a path that is also loop-shaped. The tape then again cooperates with the drum 5, whereupon it proceeds, via the other set of pulley arrangements, towards the other, receiving, spool on which it is wound.

The angular position of the feelers 8 and 9 depends on the amount of tape the

spools

2 and 3 carry. The drum 5 is provided with sprocket teeth 51' (FIG. 3) for engagement with perforations formed along the edges of the tape 4 to drive the latter. The same applies to a rotary member, not shown, provided in the reading unit 17 to drive the tape therethrough. The latter is thus driven by both the drum and by this rotary member in the reading unit so .that the mean linear speedsat which the drum and this rotary member are drivenmust be the same.

This condition is here satisfied by fitting the drum Sand the reading unit 17 with electric synchronous motors, e.g. stepping motors. This requirement for synchronism could also be satisfied by resorting to two motors having controlled speeds of rotation. This however would involve the use of a servocircuit, thereby rendering the construction of the apparatus substantially more complicated.

As shown in FIG. 3, the drum 5 is mechanically connected to the shaft 181 of motor 18 via a rubber coupling element 182 having four

limbs

182a, 182b, 1826' and 182d arranged in quadrature formation and giving this element the appearance of a Maltese cross, as can be seen from FIG. 4. The ends of the pair of

opposite limbs

182a and 182b are connected to the ends of a diametral element 183, keyed to the motor shaft 181, by connection elements 184. The ends of the pair of

opposite limbs

182c and 182d are similarly connected to the rear part of the drum 5 by connection elements 185.

The coupling element 182 is so cut out that each of its limbs may, by elastic deformation, move away from its mean position by .-ior 45. One of the extreme positions the limbs 182C and 182d can occupy is shown in dashed lines in FIG. 4. By virtue of this coupling element, the intermittent motion of the drive shaft 181 is transmitted to the drum 5 as a continuous rotary motion when the drum is driving tape 4.

The motor 18 is fitted with an instantaneous blocking device 186 which comprises a rotary metal disc 187 carried by the opposite end of shaft 181 and coaxial therewith and an electromagnet 188 for axially actuating a nonrotary rubberlined disc 189 which, upon the electromagnet ceasing to be energized, is applied by spring means, not shown, against the disc 187 toblock rotation thereof. This blocking device is meant to be actuated only when the apparatus is being stopped and started.

The electronic circuit shown in FIG. 6 is provided twice, the first time in association with the group consisting of the motor 24 and the potentiometers 19 and 22, and the second time in association with the group consisting of the motor 25 and the

potentiometers

20 and 23, with the portion which is surrounded by a dashed line being common to both of these two circuits, and only one of these circuits will now be described.

The energization circuit for the motor 24 or driving

spool

2 or 3 is connected to terminals A, and A provided in a diode bridge D, D D D These terminals A, and A are connected one to terminals J, and 1', the other to terminals J and J of a reversing switch J having input terminals J and .I'; which can selectively be connected to the terminals J, and 1'': or J and J', depending on the direction in which the motor is required to rotate.

The linear potentiometer 22 or 23 has extreme terminals B, and B, which are connected one to terminals K, and K', the other to terminals K and K of a reversing switch K having input terminals K and K, which can selectively be connected to the terminals K, and K or K and K', depending on the direction in which

motor

24 or 25 is required to rotate. The potentiometer also has extreme, equipotential, zones B and 5.

The actuation of the reversing switch J and that of the reversing switch K are coupled and are effected simultaneously by an electromagnet, not shown, which is energized upon reversal of the direction of movement of the tape.

The voltage v or v that is picked off by the slide 8,, of

, potentiometer 22 or 23 is dependent on the angular position a of arm 12 or B of arm 13, that is common with the control pin of the potentiometer, and on the direction of movement of the tape. This direction of movement is determined, under continuousduty operating conditions of the apparatus, by the sign of the angular speed 0) of drum 5, which is arbitrarily chosen to be positive when the drum rotates in the direction of arrow F (FIG. 1). The angles a and B are reckoned to be positive in the direction of arrows F, and F from the leftmost position of

arms

12 and 13 in FIG. 1.

Voltages v and v respectively vary between 0 and maximum values V and V which are maintained up to angular positions a, and B, of

arms

12 and 13 when m 0, or which are reached at angular positions a, and B, of

arms

12 and 13 when w 0, and maintained, in this event, up to the maximum angular positions 01 and B, of arms 12 and I3.

FIG. 5 shows, in full lines when w O and in dashed lines when w 0, the variation of voltages v and v as functions of a and [3, respectively.

In FIG. 6, the extreme zones B and B of the resistive element of potentiometer 22 or 23 are occupied by the slide B when 0 a Aa, or 0 B As, and a aa or fi flfl respectively.

Angles a, and [3, determine the position of terminal B, and angles a and B determine that of terminal B on this resistive element.

Potentiometer 19 'or 20 is subjected, between its extreme terminals, to a voltage V,,, or V having a variable fraction v, or v which is picked off by the potentiometer slide C and which is applied, via a diode D to the input terminal K;, of the reversing switch K. I

The position of the slide C, and hence the value of voltage v,,, or v is determined by the angular position of the feeler 8 or 9, which angular position depends on the extent to which

spool

2 or 3 is filled, this being characterized by the radius r, or r, of the last turn of tape wound on the corresponding spool. i

Since the apparatus being described is meant to control a machine, e.g. a knitting machine, this machine supplies, for instance, through the intermediary of a tachymetric generator not shown, a voltage U which is proportional to its linear speed V,, to which the present apparatus has toadjust its rate of operation.

This voltage U=K V,,, is applied to the input of that portion of the transistorized circuit which is surrounded by a dashed line in FIG. 6. This circuit portion delivers, through the intermediary of an input potentiometer P, voltage V,,, or V these two voltage being identical, so that there is obtained the following relationship:

i9 2o and the following consequential relationships:

l9 t9r 2) f( KU, 2)

2o 20, a) f( 3)- A fixed, reference, voltage U,,, eg of +12 volts or so, is applied to said circuit portion and to the series-mounted resistors R, and R A constant fraction of this voltage is applied, via a diode D to the input terminal K; of the reversing switch, which terminal is at the previously mentioned potential V, or V The circuit (R,, R,, D,,) serves to maintain voltages V and V at least equal to and F R 1 R2 thereby to maintain, at the low values of V, and hence of U and in particular when the machine is at a stop, the apparatus under servocontrol, and in particular to keep the

arms

12 and 13 in their correct positions.

Two cases may arise:

so that, via circuit (R,, R D

so that, via circuit (C, D

V,,=v,,, or V =V Potentiometer 22 (or 23) being linear, the following relationships moreover occur (FIG. 5):

Voltage V or V is applied to a load resistor R The following table shows the values that are given to the A resistor R placed at the output of the slide B of potenvarious resistors in the circuit represented in FIG. 6: tiometer 22 or 23, and a resistor R placed at the output of the slide C of potentiometer 19 or 20, enable the power level to be V l V 1 adapted at point Q and are loaded by a resistor R The voltage 20 .1 55 5% V at point Q is of the form:

This potential thus depends linearly of the value of voltages 0 kg 3 v,,, and v,, or of the value of voltages v and v i.e. of the an- 2 Bit: 0:1 gular positions of feeler 8 and of arm 12 or of feeler 9 and of gzarm 13, in other words of the parameters r and a or r and B, 10 R 1 respectively. Any variation of these parameters brings about a g3 g1: 0 proportional variation of the voltage V termed index volt- 5.16 R20: I 1 g I '5 21 1.?

A servocircuit is provided so as permanently to regulate the energization of

motor

24 or 25 in dependence on the value of parameters r and a or r; and B, respectively, i.e. to subject the speed of the motor to these parameters.

This servocircuit comprises a comparator cum amplifier CA having a feedback line (resistor R capacitor C by means of which the gain can be increased.

Comparator cum amplifier CA has two inputs E and E To the first, E is applied the index voltage V to the second, 5;, is applied a voltage V, from point S and termed measurement voltage, which is proportional to the energizing power of

motor

24 or 25 and which is derived from this power, ofi terminal 1, of the reversing switch J, via a resistor R loaded by a resistor R Comparator cum amplifier CA serves to reverse one of its input voltages, V then to add it to the other, V,, and to amplify the quantity V,V, thereby to supply, at its output E an error signal 5 having a sign which is the same as that of V,V,,. The resistance values of resistors R R R R and R are so chosen that under continuous-duty operating conditions of the apparatus, this error signal may be nil or remain less than a threshold value at which the servoaction is triggered off, iLe. that V,, may be substantially equal to V,.

The servocircuit comprises, moreover, a current source which includes resistors R R R a transistor T, and a loner diode Z, and which delivers a constant current I, of which one fraction i is regulated by a transistor T, (whose base is connected to its emitter by a capacitor C in dependence on the error signal 5 which is applied to its base via a resistor R and of which the other fraction i =l i is forwarded to a power amplifier forming the final portion of the servocircuit.

This amplifier, which comprises resistors R R R R and R transistors T T T and T diodes D and D and a chemical capacitor C,, delivers to the terminal J of reversing switch J the energizing power for

motor

24 or 25.

The circuit includes a portion which consists of diodes D and D transistors T, and T resistors R R R and R and which enables the current discharged by the

motor

24 or 25 to be absorbed and to be limited when the latter, upon reversal of its energization by actuation of the reversing switch J, operates, through inertia, as a generator before stopping and reversing its direction of rotation. Current sources P,, P; and P discharge at constant voltages V V and V respectively.

When the above described apparatus is operating under continuous-duty operating conditions, the direction of travel of the tape 4 is defined, as'has been seen, by the sign of the angular speed 6 of drum 5, this sign being chosen positive in the direction of arrow F.

Under transitional operating conditions, this sign only defines the direction of travel of the tape in the drum 5 and the reading unit 17.

The speed of the motor controlling the rotary member that drives the tape in the reading unit 17 and the speed of the motor driving drum 5 are adjusted to the speed of operation, V,,,, of the machine to which the apparatus is fitted. These two motors can, to this end, be driven by impulses emitted by the machine and having a frequency proportional to V As will be seen further on, the operation of the drum motor remains, however, dependent on that of the motor controlling the rotary member in the reading unit.

A. CONTINUOUS-DUTY OPERATING CONDITIONS Under continuous duty operating conditions, the mean linear speed of the tape 4 is uniform and is the same over its entire path of travel, i.e. from when it is unwound off the delivery spool (3 if w 0 2ifw 0) until it is rewound on the receiving spool (2 if m 0 3 if w 0).

The linear speed of the tape on the drum is made uniform, despite the jerky motion of the drum motor, by means of the transmission arrangement described above with reference to FIGS. 3 and 4. Y

The motion of the tape through the reading unit 17 remains jerky but the mean linear speed of the tape is the same as the even speed over the drum 5.

In this form of embodiment, wherein the motors for the reading unit 17 and the drum 5 are stepping motors, a counting circuit, not shown, is provided to trigger off, outside the periods in which the direction of travel of the tape is reversed, one step of the drum motor for every three steps of the reading unit motor, the angular ahTpfiide of the steps of theset wo motors being of course dependent on the diameter of the drum and on the diameter of the tape driving member in the reading unit so that the linear speed of the tape may, on average, be the same over the drum and in the reading unit.

The

arms

12 and 13 remain in a substantially mean angular shown in full lines in FIGS. 1. The slide 8, of potentiometer 22 or 23 remains in the corresponding mean position it occupies and a decrease of V =k v +k v The comparator cuni amplifierCA br'fiie electronic circuit that is associated with the potentiometers l9 and 22 and with the motor 24, delivers an error signal e proportional to variation in the speed V,, that characterizes the operating conditions, or the working rate, of the machine with which the present apparatus is associated, or a variation in the angular speed of the

spools

2 or 3 in relation to the value this speed has under continuous-duty operating conditions, or else a change in the value or of the sign of to.

These various factors bring about a momentary break in the synchronism existing between the operation of the

spools

2 and 3 and that of the members which cooperate with the tape 4 along its path of travel, i.e. the drum 5 and the reading unit 17. This gives rise to a change in the length of this path of travel, which change is absorbed by the

arms

12 and 13, under the action of the springs 14 and 15, by modifying their angular positions (angles or and [3). zivaiasai of V,,

It may happen, for instance as a result of a variation in the frequency of the mains supplying the machine, or of a desired change in the working rate of the machine, that the linear speed V,,, comes to be modified. It is imperative that the apparatus should adjust as quickly as possible to this new working rate set by the machine.

V,,V 0 which, by acting on the base of the transistor T pared to the decreasing voltage V The quantity V ,V,,,

which is still positive, continues to cause the motor 24 to slow down.

Spool 3 is delivering: r, is decreasing and v is increasing.

I As long as i R which increases and causes an increase of and an increase of V =k v +k2v2 The comparator cum amplifier CA of the circuit that is associated with the

potentiometer

20 and 23 and with the motor 25, delivers an error signal e 0 proportional to V,-V 0 which, by acting on the base of the transistor T causes the current i to decrease and hence brings about an increase of the current i and, via the circuit for amplifying the power for the energization of motor 25, an acceleration of this motor. The voltage V, is thus increased and again compared with the decreasing voltage V The quantity V,V which is still negative, continues to cause the motor 25 to accelerate.

Ii w 0, spool 2is receiving and spool 3 is delivering. A

reduction of V,,, immediately causes a corresponding decrease in the speed at which the tape is driven in the reading unit 17 and a corresponding decrease of (0, whereas

spools

2 and 3, do not instantaneously change their rate of motion. 7

This gives rise to an increase in the length of tape between i the spool 3 and the drum 5, which increase is absorbed by an increase in B on account of the compensating action of the spring 15 on arm 13, and further gives rise to a corresponding decrease in the length of tape between the drum 5 and the spool 2, which decrease is absorbed by an increase in a, the arm 12 tensioning the spring 14.

This decrease in V, causes a decrease in the'voltage U which in turn causes a drop in V and V and hence a drop in V and V respectively.

The increase of a and of B FIG. 5 cau ses a decrease in v and in v this decrease being accentuated by the drops in V and in V This gives rise to a decrease in V, and, since V,-V, becomes 0, to the emission by the comparator cum amplifier CA of an error signal e 0 which causes i to become larger and i to become smaller, thus reducing the energization of the

v motors

24 and 25

driving spools

2 and 3, which motors'slow down and cause a and B to become smaller thereby progressively to return them to their continuous-duty operating con- Spool 2 is delivering and r, is decreasing. The circuit which is associated with the potentiometers l9 and 22 and with the motor 24 reacts to this decrease of r, in the same way as the circuit which is associated with the

potentiometers

20 and 23 and with the motor 25 when w 0, and so causes the motor 24 to accelerate.

Spool 3 is receiving and r, is increasing. The circuit which is associated with the

potentiometers

20 and 23 and with the motor 25 reacts to this increase of r: in the same way as the circuit which is associated with the potentiometers l9 and 22 and with the motor 24 when (n O, and so causes the motor 25 to slow down.

Of course, this subjection of the operating conditions of

motors

24 and 25 to the values of parameters r and r,,, respectively, is carried out instantaneously and continuously.

B. TRANSITIONAL OPERATING CONDITIONS What has'just been iplaiiied intastiest;536E553 transposed without difficulty to the case where w 0 with the spool 2 delivering and the spool 3 receiving. W b. Variationin the speed of the spools 23nd 3 inrelation to their continuous-duty operating conditions speed:

It may happen that the angular speed of one of the

spools

2 and 3, or both simultaneously, be subjected to an abruptchange. Let it be assumed, for instance, that the receiving spool 2 comes to slow down (w 0): the length of tape between this spool and the drum 5 increases and this increase in length is absorbed, under the action of spring 14, by a displacement of arm 12 which decreases angle a. FIG. 5 shows that this decrease of or causes v,, to increase and hence, all other things being equal, an increase of V, and the appearance of a difference V,V 0 causing the comparator cum amplifier CA to emit an error signal e 0 which causes i to become smaller and hence i, to become larger. This larger i, causes the energization of motor 24 to increase thereby accelerating spool 2 and reducing the excess length of tape between the spool and the drum 5, thus causing an increase of a which, progressively and at the same time as the angular speed of this spool, returns to its continuous-duty operating conditions value.

Any other variation of the speed of

spools

2 and 3 when m causes in like manner the appearance of transitional operating conditions which restore the angular speed of these spools to their continuous-duty operating conditions value.

c. Variation of (n:

An abrupt variation in the value of w triggers off transitional operating conditions of the kind described under a, except that since V,, is constant, voltages V and V do not vary.

d. Reversal of the sign of m:

The tape 4 is alternately read in one direction of travel and then in the other ((o 0 and m 0). The reversal of this direction of movement is triggered off by the reading of a reversal item of information carried by the'tape and occurs'instantaneously in the reading unit. This reversal causes, through the intermediary of an electromagnet not shown, the reversing switches J and K to change over.

In order to give the drum 5, now being driven by inertia, time to stop, the previously mentioned counting circuit triggers off the first reversed step of the drum motor only afterthe reading unit motor has moved, in its new direction of rotation (3n+x) steps, x being the number of steps made by this motor in its previous direction of rotation between the time the last drum motor step was triggered off and the time when the reversal item of information was read. The number I: may be equal to 3, 4 or even 5. This results, .on opposite sides of the reading unit, in a dissymmetry of the loop formed by the tape due to the time lag between the reversal of the sign of to after the reversal of the direction of movement of the tape in the reading unit. This dissymmetry subsists as it is until the next reversal of the sign of u.

The changing over of the reversing switch J causes the value of v as a function of a, or of v as a function of B, to pass from one curve of FIG. to the other, whereas the changing over of the reversing switch K reverses the energization ofmotors 24 and 25.

The inertia of

spools

2 and 3, which becomes quite substantial by virtue of the amount of tape wound thereon, does not enable the direction of rotation of the spools to be instantaneously reversed. Transitional operating conditions thus come into being upon reversal of the sign of m.

Although the energization of the

motors

24 and 25 is instantaneously reversed, the latter still retain for a certain length of time, termed kinematic reversal time, the same direction of rotation, through being driven by the inertia of the

spools

2 and 3.

This kinematic reversal time may amount to a few tenths of a second in the case of a linear tape travel speed of about 100 cm/sec. it depends, in the case of each spool, on the extent to which it is filled.

Supposing, for instance, that w is initially positive, with spool 2 receiving and spool 3 delivering, the tape 4 continues, during this kinematic reversal time, to be wound by spool 2 and to be unwound by spool 3 when it is in fact already being driven in the opposite direction by the drum 5 and in the reading unit 17, :0 having become negative. This results in a decrease in the length of tape between the spool 2 and the drum 5 and in an increase in the length of tape between the drum 5 and the spool 3, which decrease and which increase are respectively absorbed by an abrupt increase of a and B.

Upon being so driven, both

motors

24 and 25 operate as generators and the current they supply is looped through earth via the diode bridge (D,, D D D and the transistor T, which becomes unblocked as soon as the value of the voltage at the terminals of resistor R exceeds a threshold value. This current exerts a braking action on the motor which slows down. The voltage at the terminals of resistor R, decreases and because this current is now decreasing as a result of the motor slowing down, the transistor T becomes blocked as soon as the voltage at the terminals of resistor R,, has dropped back below said threshold value. The

motors

24 and 25 then stop whereupon they reverse their direction of rotation and gather up speed while causing a and B to decrease.

in being negative, the variation of v =f(a) and of v =f(B) is represented by the curve shown in dotted lines in FIG. 5. The effect of decreasing a and B is to cause v and v,. and hence V to rise and to cause a difference V,V 0 to appear which generates at the output of the comparator cum amplifier an error signal e O that increases i and that decreases i and hence the energization of

motor

24 or 25, the apparatus as a whole tending progressively to achieve new continuous-duty operating conditions characterized by -u and B-B v Of course, transitional operating conditions similartothose which have just been described will come into being when to again becomes positive upon the direction of travel of the tape being again reversed.

We claim:

1. Apparatus for storing and winding a discontinuously and reversibly moving tape, comprising a pair of holders for supporting a pair of tape spools; a pair of reversible motors for reversibly driving said holders whereby said spools may be alternately receiving and delivering; tape reading means in the path of said tape .between said spools; drive means for driving said'tape as it enters and as it issues from the reading means, a tape takeup system in the path of said tape for temporarily modifying the length of first and second portions of said path between said drive means and said spools; first supply means actuated by saidsystem and adapted to supply, for each of the spools, a first electric index voltage dependent on the length of the corresponding one of said tape path portions; second supply means associated with each of said spool holders and adapted to supply, for each of the spools, a second electric index voltage dependent on the radius of the last turn of tape wound on .the corresponding spool; and electronic circuit.

means having a comparing element for each spool and adapted to tie the speeds at which said motors drive said spool holders to the corresponding ones of said first and second index voltages; the arrangement being such that under continuous-duty operating'conditions of 'the apparatus, the tape can unwind off thedelivering'spool and can be wound on the receiving spool at a linear speed equal to that at which it is driven by said drive means, with said first index voltage remaining constant and said second reference voltage, which is variable, progressively modifying the angular speed of the spool associated therewith, and such that any modification in the length of the tape along said path portions causes the takeup system to come into operation and a corresponding variation of the first index voltage to occur which triggers off transitional operating conditions tending to restore said tape path portions to their previous length under continuous-duty operating conditions.

2. Apparatus according to claim 1, further comprising a baseplate through which project said holders andon one face of which are mounted said tape reading means, said drive means and said tape takeup system, wherein said takeup system includes first and second arms disposed on opposite sides of said tape reading means and carried by first and second pivot pins mounted in said baseplate for angular movement between first and second extreme positions, first and second sets of pulley arrangements adapted to cooperate with said tape and respectively disposed along said first and second tape path portions, each set having a first plurality of rollers pivotally mounted on a corresponding said arm and a second plurality of rollers pivotally mounted on said baseplate, said tape being arranged to cooperate, during operation, with alternate ones of said first and second pluralities of rollers whereby the angular position occupied by said first and second arms between said extreme positions will determine the length of said first and second tape path portions, respectively, said system further including first and second spring means cooperating with'said first and second arms, respectively, and urging said arms into angular positions lengthening the corresponding tape path portions.

carried by first and second pivot pins mounted in said f baseplate in the vicinity of said spool holders and which carry at their free ends first and second follower rollers for engagement with the last turn of tape wound on said spools, respectively, when mounted on said holders, first and second spring means cooperating with said first and second feeler arms to urge said follower rollers, during operation, into engagement with the last turn of tape wound on said spools, and first and second linear potentiometers controlled by said first and second pins, the value of said second electric index voltage supplied during operation by said second supply means for each spool being dependent on the angular position of the corresponding one of said feeler arms, said angular position being in turn dependent on the radius of the last turn of tape wound on the corresponding spool.

6. Apparatus according to claim 1, wherein said comparing element for each spool is a comparator cum amplifier having a first input for receiving an index voltage resulting linearly from said first and second electric index voltages, and having a second input for receiving a measurement voltage which is proportional to the power for energizing the corresponding spool-holder driving motor, the difference between the measurement voltage received at said second input and the index voltage received at said first input being amplified by said comparator cum amplifier and giving rise to an error signal, either positive or negative, which reacts on the energization of said corresponding motor and hence on the angular speed of the spool-holder driven by said motor.

Claims

1. Apparatus for storing and winding a discontinuously and reversibly moving tape, comprising a pair of holders for supporting a pair of tape spools; a pair of reversible motors for reversibly driving said holders whereby said spools may be alternately receiving and delivering; tape reading means in the path of said tape between said spools; drive means for driving said tape as it enters and as it issues from the reading means, a tape takeup system in the path of said tape for temporarily modifying the length of first and second portions of said path between said drive means and said spools; first supply means actuated by said system and adapted to supply, for each of the spools, a first electric index voltage dependent on the length of the corresponding one of said tape path portions; second supply means associated with each of said spool holders and adapted to supply, for each of the spools, a second electric index voltage dependent on the radius of the last turn of tape wound on the corresponding spool; and electronic circuit means having a comparing element for each spool and adapted to tie the speeds at which said motors drive said spool holders to the corresponding ones of said first and second index voltages; the arrangement being such that under continuous-duty operating conditions of the apparatus, the tape can unwind off the delivering spool and can be wound on the receiving spool at a linear speed equal to that at which it is driven by said drive means, with said first index voltage remaining constant and said second reference voltage, which is variable, progressively modifying the angular speed of the spool associated therewith, and such that any modification in the length of the tape along said Path portions causes the takeup system to come into operation and a corresponding variation of the first index voltage to occur which triggers off transitional operating conditions tending to restore said tape path portions to their previous length under continuous-duty operating conditions.

2. Apparatus according to claim 1, further comprising a baseplate through which project said holders and on one face of which are mounted said tape reading means, said drive means and said tape takeup system, wherein said takeup system includes first and second arms disposed on opposite sides of said tape reading means and carried by first and second pivot pins mounted in said baseplate for angular movement between first and second extreme positions, first and second sets of pulley arrangements adapted to cooperate with said tape and respectively disposed along said first and second tape path portions, each set having a first plurality of rollers pivotally mounted on a corresponding said arm and a second plurality of rollers pivotally mounted on said baseplate, said tape being arranged to cooperate, during operation, with alternate ones of said first and second pluralities of rollers whereby the angular position occupied by said first and second arms between said extreme positions will determine the length of said first and second tape path portions, respectively, said system further including first and second spring means cooperating with said first and second arms, respectively, and urging said arms into angular positions lengthening the corresponding tape path portions.

3. Apparatus according to claim 2, wherein said first supply means include first and second linear potentiometers actuated by said first and second pivot pins, the supply of each of said potentiometers being reversible at the same time as the direction of travel of the tape.

4. Apparatus according to claim 3, wherein said potentiometers have each two extreme, equipotential, zones which correspond to regions in the angular movement of said arms adjacent said extreme positions.

5. Apparatus according to claim 1, wherein said second supply means include first and second feeler arms which are carried by first and second pivot pins mounted in said baseplate in the vicinity of said spool holders and which carry at their free ends first and second follower rollers for engagement with the last turn of tape wound on said spools, respectively, when mounted on said holders, first and second spring means cooperating with said first and second feeler arms to urge said follower rollers, during operation, into engagement with the last turn of tape wound on said spools, and first and second linear potentiometers controlled by said first and second pins, the value of said second electric index voltage supplied during operation by said second supply means for each spool being dependent on the angular position of the corresponding one of said feeler arms, said angular position being in turn dependent on the radius of the last turn of tape wound on the corresponding spool.